exam 2 deck Flashcards
protozoa are a sort of strange collection of microbes that really existed as early… what?
they existed as early Eukarya
does the protozoa define a specific, seperate domain or class of organisms?
no it doesn’t form a particular specific group within any taxonomic class, protozoa are a sort of strange collection of microbes that really existed as early eukarya
are plants, animals or fungi a type of protazoa?
no
are entamoebae and slime molds types of protazoa?
yes
what are 5 groups that are protazoa?
ciliates, flagellates, trichomonads, microsporidia, diplomonads
do ciliate protazoa typically cause diseases in humans?
no
how are protazoa classified?
through their means of movement, nutrition and reproduction
are protazoa typically intracellular
yes
why are ciliates bad news for smaller organisms?
because ciliates can consume them whole
are amoeba and stentor ciliates?
no only stentor is a ciliate
how do are protozoan diseases transmitted to other organisms?
ingestion, vectors, sexual contact, transovarial, placental
why are protozoan pathogens not well represented in foodborne illnesses?
because they are typically sensitive to heat, so any cooking usually kills them even if they are present in water
are protazoan pathogens capable of surviving high temperatures?
no, they are typically sensitive to heat and cannot survive high temperatures
how are vector borne transmissions distinguished?
vector borne transmission then is distinguished by a lack of ability to transfer the disease from one host to another; you need a mosquito or another organisms to act as a vector between hosts
what are the 4 main malaria species?
what is the general class through which maleria appears?
apicomplexa
what are the unique strucutures that appear in in apicomplexa cells?
they have a polar ring, conoid and a microneme and rhoptry
what is the significance of the polar ring and conoid?
they maintain a distinctive shape
what is the significance of the microneme and rhoptry?
they aid in host cell invasion
are apicomplexa motile?
no they tend to live within cells and rely on other species to transport them between hosts
how does the polar ring and conoid aid the apicomplexas invasion of other cells?
it is very pointy and rigid which helps the pathogen burrow into the cell with its pointed end
how do the microneme and rhoptry help the apicomplexa invade host cells?
they secrete proteins which break down host cell membranes
what is the malaria life cycle?
-steps 4, 5 and 6are called the cyclical stage
-The ring stage is where you have one parasite in the centre of a red blood cell. and that undergoes a, a procedure in three, three broad steps whereby it multiplies. at that third step, the merozoites are produce in dozens inside a red blood cell And that eventually ruptures. And all of those parasites that are released will then go on to infect other red blood cells.
how come blood products aren’t tested for parasites before transfusion happens?
if you’ve got dormant parasites in the liver for two years that are in such low numbers, you can hardly detect them in the blood. They can still potentially be transferred to other hosts through a blood transfusion,
what do sporozoites undergo in the liver?
they undergo schozogony which results in the merozoites which infect the red blood cells
why is the circumsporozoite protein important?
because most the successful vaccines target that
why is heparin sulfate glycosaminoglycan (GAG) important?
because that is the host liver cell antigen which the parasite will bind too. there’s an interaction between the circumsporozoite protein and that binds to the GAG on the host cells.
how are the symptoms during the schizogony stage?
mild, malaria hepatitis is rare and the variation in liver involvment is rare because the parasites coat themselves in host liver cell membranes because it gives them a greater chance at survival
malaria pathogenicity
the exonemes help the parasites rupture out of red blood cells. And the dense granules on the far right hand side express antigens that appear on the red blood cell surface. So if a red blood cell is infected, it will have it will have malaria antigens on its surface.
why is it not useful to vaccinate against the antigens appearing on infected red blood cell surfaces?
he potential combination of antigens that could be on an infected red blood cell fall into the thousands, because there’s loads of different combinations of different antigen classes. So, the dense granule produced antigens tend not to be able to be vaccinated against.
why are micronemes important for the apicomplexa?
the micronemes allow the apicomplexa to glide across the surface of the redblood cell and orient themselves ti exusre the apical complex is facing into the cells
why are rhoptres important?
they secrete enzymes, proteolitic enzymes which break down the red blood cell surface and form a vacuole which the parasite can enter
what are the fever patterns of P. vivax and P. ovale
you have a tertian fever; one day of fever for every 2 days of no fever/symptoms
what are the fever patterns of P. vivax and P. ovale
what are the fever patterns of P. malariae
you have a fever once every 4 days; quartan fever
what are the fever patterns of P. falciparum
for every 2 days of fever you have 1 day without fever; tertian fever, the body is more sensitive to falciparum as fever is triggered at lower levels of toxin production
cyclical malarial fever
why do you get headaches and fever symptoms with malaria?
the immune system is very sensitive to hemozoin, which is the by product of malarial cells breaking down haemoglobin, hemozoin is released when the red blood cells rupture
how to malaria quinine treatments work?
thye work by preventing the parasites from breaking down their own toxic byproducts; the protozoa poison themselves with their own hemozoins and toxic oxygen species
what conditions are protective against malaria?
how is fever triggered by malaria?
the hamozoins trigger an immune response, the immune response affects the hypothalamus and then that results in elevated core body temperature
what is the pyrogenic threshold?
the amount of parasites needed per microlitre of blood to trigger an immune response
what is the pyrogenic threshold?
what is the typical pyrogenic threshold?
between 200-1500 parasites per microlitre (ul) of blood
what is the pyrogenic threshold of P. falciparum?
about 150 parasites per microlitre (ul) of blood
what is toxoplasmosis
it is an apicomplexan disease caused by toxoplasma gondii
is apicomplexan an obligate intracellular parasite
yes
which hosts should be more concerned with toxoplasmosis
at risk hosts
what are the routes of spread of T. gondii?
is toxoplasma gondii reliant on humans?
no, it cycles through wild animals and typically gets to humans through undercooked meat products, blood or organ transplants, pregnancy or the fecal matter from pets
what does tachyzoites refer to?
tachyzoites means a fast replicating form of parasite
what does bradyzoites mean?
bradyzoites refers to a slow, dormant form of parasite that is barely even metabolising so this form is not concerning for humans unless you have a weakened immune system
in neonates, when is a toxoplasma infection most concerning?
during the 1st and 2nd trimesters
what are the possible outcomes of neonatal toxoplasmosis?
ocular abnormalities, brain damage or foetal death
why is a 3rd trimester toxoplasma infection not as concerning?
the symptoms are milder however potential damage is possible and damage to brain and eye tissue that leads to developmental problems, blindness and deafness is still possible
are humans terminal hosts of toxoplasma?
yes, this means they are accidental hosts
what are merozoites?
a merozoite is an apicomplexa protozoa that is in an infective form
why can toxoplasma be so dangerous for neonates?
because protozoa are very large cells compared to say bacteria thus a small number of cells can cause significant damage to developing tissue so not many cells are required to cause lesions
what are the symptoms caused by T. gondii infections?
flu-like illness that is caused by an immune response not the parasite itself
what is a dormant T. gondii infection
it is a stand off between parasites and the host where neither wins.
bradyzoites exist as cysts in neuron and muscle tissue, the infection is reactivated if the host becomes immunocompromised
what people are at risk to toxoplasmosis?
if the person has taken steroids, immunosuppressant drugs, suffers from HIV/Aids
how can toxoplasmosis affect immunocomprimised people?
it can cause pneumonia, carebral calcification, nephritis, skin rashes
how can complex cases of toxoplasmosis be treated?
they can be treated with a combination of pyrimethamine, sulfadiazine and folinic acid
why is it difficult to treat protozoan disease compared to bacterial diseases?
the protozoan cells are closer to our own cells so there are fewer targets
what is african trypanomiasis?
sleeping sickness
what is african trypanomiasis caused by?
trypanosoma brucei, central and west african distribution
what are the two types of trypanosoma brucei
trypanosoma brucei gambiense
trypanosoma brucei rhodesiense
what is american trypanosomiasis?
chagas disease, endemic in south america especialy in Brazil
what is chagas disease caused by?
trypanosoma cruzi
african trypanosomiasis life cycle
what is a vector for human african trypanosomiasis
Tsetse flys
Tsetse flys
what are Tsetse fly habitats
forests/shrub land
rivers and watering holes
animal reservoirs
concetrations close to human settlements
they are very difficult to eradicate but traps have helps reduce their numbers
how has human african trypanosomiasis spread been controlled?
using traps has been very effective as apposed to vaccines or drugs as the vectors that spread them are controlled
when do symptoms for human african trypanosomiasis usually show up?
they can take months to years from initial infection to show up
why is it difficult to treat sleeping sickness?
because early stage disease mirrors many other diseases but the most effective drugs needs to be given early
human african trypanosomiasis symptoms
how can african trypanosomiasis cause coma?
if the parasite crosses the choroid plexus to the brain and CSF
how can african trypanosomiasis be diagnosed
through the cerebral spinal fluid
what can happen if african trypanosomiasis is left untreated?
it can cause weight loss and neurological impairment
what is the biggest factor in protozoan induced damage
low level chronic activation of the immune system; If we can’t clear these pathogens from our body within a few weeks or even months, you get a chronic infection. The immune system is always trying to fight back, and that causes inflammation, scarring and other kinds of damage
how can trypanosomes be treated?
drugs that target the glycosome, which does not occur in human cells
what drug can treat trypanosomes?
suramin is a drug that binds to enzymes in the cytoplasm. suramin bound enzymes are dysfunctional as their ATP synthesis is reduced so cell cannot maintain energy levels
how is american trypanosomiasis spread?
through blood transfusions because vector to human contact has become less common, urban areas are more impacted
from what vector is chagas disease spread?
Triatomine bugs which infect the host in low quality housing usually,
chagas disease symptoms
2 stages
Acute stage occurs shortly after infection with swelling at the site of the infection
chronic stage, occurs to 30% of people after an asymptomatic period of several years
how does the Triatomine bug infect people
it defacates on the eye, or defaction of the vector is rubbed into the eye by the host inadvertdly, which rubs the pathogen into the eye mucosa reuslting in Romaña’s sign
what occurs in the chronic stage of chagas disease?
27% of people get cardiac symptoms; heart is the most likely organ to be affected
3-6% develope megaviscera or peripheral nerve damage
the parasite resides in the tissue cells of the host
chronic stage causes these parasites to build up and build up in these muscle tissues there will be some level of immune activation against Chagas disease pathogens. This can happen over years. You’ve got low level immune activity attacking your heart tissues and it never eliminates the parasites, it doesn’t completely wipe them out and Neither does the pathogen completely wipe the host out. So for years and years, you’ve got this chronic infection and the immune system in trying to get rid of these parasites I s constantly irritating the tissues. It’s constantly causing lesions and inflammation in the heart tissues themselves And long term that’s going to cause scarring. So over several years it’s like collateral damage. Your own immune system trying to wipe out these parasites damages your own heart tissues. the heart is going to be less efficient and effective And eventually that could be fatal because the heart simply doesn’t have the tone or strength to continue to pump blood around the body
what is the name of the chagas disease parasite
trypanosoma cruzi
what happens to the chagas disease parasite once it enters the cytoplasm of a muscle cell?
it becomes an amastigote which has a residual flagellum as it is no longer necessary
why is the kinetoplast in sleeping sickness and chagas disease parasites important?
it can be a target for drug treatments as human cells do not have it
why can cerebral spinal fluid be useful in detecting chagas disease
because about 70% of people have parasites in CSF
is leishmaniasis an intracellular parasite?
yes it is an obligate intracellular parasite
how is leishmaniasis spread
transmitted by female sandflies
what sort of disease does leishmaniasis occur as?
cutaneous, mucocutaneous and visceral disease
life cycle of leishmaniasis
what are the clinical presentations of cutaneous leishmaniasis?
lesions may not be as painful as they look which can help in diagnosing them
what happens shortly after a bite from an infected sandfly?
one or more skin sores can arise
what happens if a bite from an infected sandfly remains untreated
the sores can last from weeks to years and develope raised edges with a central crater
when can mucocutaneous leishmaniasis happen?
it can happen months-years after the cutaneous lesion has healed
how can mucocutaneous leishmaniasis be differentiated?
scanty presence of parasites and naso-pharangeal tissues are affected
what is the main cause of the tissue damage seen in mucocutaneous leishmaniasis?
constant low level activation of the immune system causing inflammation and tissue destruction as it tries to eradicate vesicles containing parasites. it is a chronic long term infection
how can mucocutaneous leishmaniasis be treated?
you can surgically remove infected tissue and give drugs
where does visceral leishmaniasis infections occur
they happen internally where it mainly affects the liver and spleen- It’s chronic long term infection causing immune system targetted collateral damage to organs and structures.
how can leishmaniasis be treated?
they have a kinetoplast which can be targetted by drugs
how can visceral leishmaniasis infections be fatal?
they can cause damage to liver and spleen via the massive swelling of these organs which can eventually result in them no longer functioning if not treated
which form of leishmaniasis is most often seen as the most serious?
visceral leishmaniasis because it will always be fatal if left untreated
where is the kinetoplast?
note the flagella is also no longer there
What are the major routes of transmission for protozoan infections?
Ingestion, vector-borne, sexual contact, transovarial, and placental transmission.
Name the four classifications of protozoa based on their structure and movement.
Ciliates, flagellates, amoebae, and Apicomplexa.
What is schizogony, and why is it significant in protozoan lifecycles?
Schizogony is asexual reproduction leading to multiple daughter cells, significant in Plasmodium spp. for rapid proliferation.
Why are vector-borne protozoan diseases challenging to control?
They require managing not only the pathogen but also the vector populations, such as mosquitoes or ticks.
Which protozoan species can transmit through ingestion and cause waterborne diseases?
Giardia lamblia and Cryptosporidium spp.
What structural adaptations allow Apicomplexa protozoa to invade host cells?
Specialized structures like apical complexes, micronemes, and rhoptries.
How do vector-borne protozoa differ in their transmission from waterborne protozoa?
Vector-borne protozoa require an intermediate host for transmission, whereas waterborne protozoa are typically ingested as cysts.
What is the main survival strategy of protozoa in the environment?
Formation of cysts that can withstand harsh environmental conditions.
What distinguishes Apicomplexa from other protozoan groups?
Apicomplexa are obligate intracellular parasites with a polar ring structure and no external means of movement.
Name two protozoan diseases caused by amoebae.
Amoebic dysentery and primary amoebic meningoencephalitis (PAM).
Name the four main species of Plasmodium that cause malaria.
P. falciparum, P. vivax, P. malariae, and P. ovale.
What is the exoerythrocytic stage in the malaria lifecycle?
It is the stage where sporozoites infect liver cells and undergo schizogony to produce merozoites.
How does Plasmodium evade the host immune system?
By hiding in liver cells and red blood cells, and coating themselves in host cell membranes.
What are the protective factors against malaria in certain populations?
Sickle cell trait, thalassemia, lack of the Duffy antigen, and glucose-6-phosphate dehydrogenase deficiency.
What triggers cyclical fever in malaria?
The synchronous rupture of red blood cells releasing merozoites and toxins like hemozoin.
What is the role of the circumsporozoite protein in malaria?
It aids in the initial attachment of sporozoites to liver cells and is a target for vaccines.
Which Plasmodium species can cause dormant liver stages?
P. vivax and P. ovale.
What is the pyrogenic threshold, and how does it differ in P. falciparum?
It is the parasite density needed to trigger fever; P. falciparum has a lower threshold (~150 parasites/µL blood).
How does quinine work against malaria parasites?
By preventing the parasites from detoxifying hemozoin, effectively poisoning them.
Why is P. falciparum considered more severe than other malaria species?
It triggers fever at lower parasite densities and causes continuous fever with fewer symptom-free days.
What are the main infective forms of Toxoplasma gondii?
Tachyzoites (rapidly replicating) and bradyzoites (dormant cysts).
How is Toxoplasma gondii transmitted to humans?
Through contaminated food, water, cat feces, or transplacentally during pregnancy.
Why are humans considered terminal hosts for Toxoplasma gondii?
Humans are not part of its natural lifecycle, which primarily cycles between cats and prey animals.
What are the severe outcomes of congenital toxoplasmosis?
Brain damage, ocular abnormalities, and fetal death, particularly during the first trimester.
What is the significance of bradyzoite cysts in Toxoplasma infections?
They remain dormant in host tissues and can reactivate if the host becomes immunocompromised.
How does toxoplasmosis affect immunocompromised individuals?
It can cause invasive infections like pneumonia, cerebral calcification, and nephritis.
What is the role of tachyzoites in acute infections?
They are the rapidly replicating stage responsible for active tissue invasion and damage.
How is toxoplasmosis diagnosed in pregnancy?
Through serological testing and amniocentesis for fetal infection.
What treatments are available for severe toxoplasmosis?
Pyrimethamine combined with sulfadiazine and folinic acid.
Why are pregnant individuals advised to avoid handling cat litter?
To prevent exposure to Toxoplasma oocysts shed in cat feces.
What are the two types of human African trypanosomiasis?
T. brucei gambiense (chronic) and T. brucei rhodesiense (acute).
What vector transmits African sleeping sickness?
The tsetse fly (Glossina spp.).
What is Romana’s sign in Chagas disease?
Swelling around the eyes caused by Trypanosoma cruzi infection via triatomine bug feces.
How does Trypanosoma cruzi evade the host immune system?
By forming intracellular amastigotes within host cells.
What chronic complications can arise from Chagas disease?
Cardiac damage, megaviscera, and peripheral nerve damage.
How is sleeping sickness treated in its early stages?
With drugs like suramin targeting the glycosome for ATP synthesis disruption.
What are the reservoirs for Trypanosoma species?
Domestic animals, wildlife, and humans.
What are the symptoms of late-stage sleeping sickness?
Coma, neurological impairment, and weight loss.
What measures are effective for controlling tsetse fly populations?
Insecticide-treated traps and managing habitats like watering holes.
Why has blood transfusion become a significant route for Chagas disease transmission?
Due to difficulty in screening for low levels of parasites in donors.
What are the three clinical forms of leishmaniasis?
Cutaneous, mucocutaneous, and visceral leishmaniasis.
Which vector transmits Leishmania spp.?
Female sandflies (Phlebotomine spp.).
What are the symptoms of cutaneous leishmaniasis?
Skin sores with raised edges and central craters.
Why is visceral leishmaniasis the most severe form?
It affects internal organs like the spleen and liver and is often fatal if untreated.
What is the role of amastigotes in Leishmania infections?
They are the intracellular stage that replicates within host macrophages.
How can leishmaniasis be prevented?
Using insecticide-treated nets and avoiding exposure to sandfly habitats.
What is the main diagnostic marker of visceral leishmaniasis?
Enlargement of the spleen and liver.
How does mucocutaneous leishmaniasis differ from cutaneous forms?
It affects mucosal tissues, often leading to deformities in the nasal and oral regions.
Why are sandflies challenging to control with standard nets?
They are small enough to pass through most standard net mesh.
What is the role of the kinetoplast in Leishmania?
It aids in energy metabolism and is a target for drug development.
What are the main features that differentiate protozoa from other microorganisms?
Protozoa are single-celled eukaryotes with a nucleus and organelles, unlike bacteria, which are prokaryotic.
What are the primary routes of protozoan disease transmission?
Ingestion, vector-borne, sexual contact, transovarial, and placental.
Why do most protozoa not survive high temperatures?
They lack the ability to withstand heat, making cooking an effective method to kill them.
How do protozoan cysts contribute to their survival?
Cysts are a dormant, protective form that allows protozoa to survive harsh environmental conditions.
What is the function of the apical complex in Apicomplexa protozoa?
It aids in host cell invasion by secreting enzymes that digest cell membranes.
How do flagella and cilia aid protozoa in their lifecycle?
They provide movement, aiding in feeding, evasion, or host cell targeting.
Why are vector-borne protozoan diseases particularly difficult to control?
They require the control of both the pathogen and the vector population.
What distinguishes Apicomplexa from other protozoa in terms of movement?
They lack external movement structures like cilia or flagella and rely on host invasion for transport.
How does phylogenetics classify protozoa?
Protozoa are not a distinct taxonomic group but are spread across multiple eukaryotic lineages.
What environmental factors favor the survival and spread of protozoa?
Warm climates, water bodies, and poor sanitation.
Name an example of a sexually transmitted protozoan infection.
Trichomonas vaginalis.
How do ingestion-based protozoan diseases spread in human populations?
Through contaminated food or water and fecal-oral transmission.
What are the differences between trophozoite and cyst forms of protozoa?
Trophozoites are the active, feeding form, while cysts are dormant and resistant to environmental stress.
How does plasmodial streaming in amoebae aid their movement?
It allows amoebae to flow over surfaces by extending their cytoplasm.
What role do ciliates play in protozoan pathogenesis?
Most ciliates do not cause diseases in humans, but exceptions like Balantidium coli can cause gastrointestinal issues.
What are the four primary species of Plasmodium that cause malaria?
P. falciparum, P. vivax, P. malariae, and P. ovale.
How is malaria transmitted to humans?
Through the bite of infected female Anopheles mosquitoes.
What is the exoerythrocytic stage of the malaria lifecycle?
The stage where sporozoites infect liver cells and undergo schizogony to produce merozoites.
What role does the circumsporozoite protein play in malaria pathogenesis?
It enables sporozoites to attach to liver cells and initiate infection.
Why are P. vivax and P. ovale infections prone to relapse?
They form dormant hypnozoites in the liver.
What is the pyrogenic threshold for P. falciparum, and why is it significant?
~150 parasites/µL blood, significantly lower than other species, making it more likely to trigger symptoms.
How does Plasmodium evade the immune system?
By hiding in liver and red blood cells and using host cell membranes for camouflage.
What distinguishes P. falciparum from other Plasmodium species in terms of severity?
It causes more severe symptoms due to higher toxin production and lower pyrogenic thresholds.
What is the cyclical fever pattern of P. vivax and P. ovale infections?
Tertian fever: one day of fever followed by two fever-free days.
How do quinine and related drugs work against malaria parasites?
By inhibiting the parasite’s ability to detoxify hemozoin, leading to self-poisoning.
What are the symptoms associated with the erythrocytic stage of malaria?
Cyclical fever, chills, headache, and anemia.
What is the role of hemozoin in malaria pathogenesis?
It acts as a pyrogen, triggering fever by stimulating the immune system.
Why is the liver stage of malaria asymptomatic?
Parasites remain hidden within liver cells, avoiding detection by the immune system.
What genetic factors provide resistance to malaria?
Sickle cell trait, lack of the Duffy antigen, and glucose-6-phosphate dehydrogenase deficiency.
How does malaria influence public health in endemic regions?
It imposes a high disease burden, impacting economic productivity and healthcare resources.
What are the primary sources of Toxoplasma gondii infection?
Undercooked meat, contaminated water, and cat feces.
Why are humans considered accidental hosts for Toxoplasma gondii?
Humans are not part of its natural lifecycle, which cycles between cats and rodents.
What are tachyzoites and bradyzoites?
Tachyzoites are fast-replicating forms, while bradyzoites are dormant cysts in tissues.
What are the risks of congenital toxoplasmosis during pregnancy?
Brain damage, ocular abnormalities, and fetal death, especially in the first trimester.
How does toxoplasmosis present in immunocompromised individuals?
It causes severe infections such as cerebral calcification, pneumonia, and nephritis.
How does the immune system maintain a ‘stand-off’ with Toxoplasma gondii in healthy individuals?
By preventing bradyzoites from reactivating while allowing their dormancy in tissues.
How can toxoplasmosis be diagnosed during pregnancy?
Through amniocentesis or serological testing for antibodies.
What is the role of cat litter in Toxoplasma transmission?
Cats shed oocysts in their feces, which can infect humans handling litter.
Why is Toxoplasma gondii a concern in blood transfusions?
Dormant bradyzoites in the donor’s blood can reactivate in immunocompromised recipients.
What treatments are available for severe toxoplasmosis?
Pyrimethamine, sulfadiazine, and folinic acid.
What factors can reactivate dormant Toxoplasma infections?
Immunosuppression from conditions like HIV/AIDS or steroid use.
What is the primary target of Toxoplasma gondii in human hosts?
Muscle and nerve tissues.
How does Toxoplasma gondii evade the immune system during acute infections?
By rapidly replicating as tachyzoites and hiding within host cells.
What are the symptoms of mild toxoplasmosis in healthy individuals?
Flu-like symptoms, including fatigue and muscle aches.
Why is raw or undercooked meat a significant risk factor for Toxoplasma infection?
Bradyzoite cysts in infected animal tissue can survive if not adequately cooked.
What are the two diseases caused by Trypanosoma species?
Sleeping sickness (African trypanosomiasis) and Chagas disease (American trypanosomiasis).
What vector transmits African trypanosomiasis?
The tsetse fly (Glossina spp.).
What is Romana’s sign in Chagas disease?
Swelling around the eyes caused by Trypanosoma cruzi infection.
How does Trypanosoma brucei evade the immune system?
By continuously varying its surface glycoproteins.
What chronic complications arise from Chagas disease?
Cardiac damage, megaviscera, and peripheral nerve damage.
How can Trypanosoma infections be diagnosed?
Through blood smears, cerebrospinal fluid analysis, or serology.
What is the primary vector for Chagas disease?
Triatomine bugs, also known as ‘kissing bugs.’
What environmental factors increase the risk of Chagas disease?
Poor-quality housing and proximity to insect reservoirs.
How does suramin work against Trypanosoma infections?
By disrupting ATP synthesis in the parasite’s glycosome.
What are the symptoms of early-stage African sleeping sickness?
Fever, swollen lymph nodes, headaches, and rash.
What is the key distinguishing feature of T. brucei gambiense infections?
They cause chronic disease with symptoms appearing months or years after infection.
How does Chagas disease transmission differ in urban areas?
It is increasingly spread via blood transfusions rather than vector bites.
What structures in Trypanosoma are unique drug targets?
The kinetoplast and glycosome.
Why are vector-control measures critical in reducing Trypanosoma transmission?
They target the tsetse fly and triatomine bug populations, interrupting the lifecycle.
How can sleeping sickness progress if left untreated?
Parasites invade the central nervous system, causing coma and death.
what does Cryptosporidium parvum cause?
Cryptosporidiosis
what does Cyclospora cayetanesis cause?
Cyclosporiasis
what does Giardia lamblia cause?
Giardiasis
what does Balantidium coli cause?
Balantidiasis (dysentery)
what does Acanthamoeba spp. cause?
Keratitis
how can protozoa survive in water
they change to a cyst form
what happens to the protozoa cysts if you ingest them?
in the gut the cyst will transform into their trophozoite forms
what is the life cycle of cryptosporidium?
what is the life cycle of entamoeba coli?
what is the prevelance of Giardia in rich countries?
2-7%
what is the prevelance of giardia in poor countries?
20-30%
what is the main symptom of giardia?
it causes diarrhoea for several weeks, abdominal cramps, gas production, lots of fat is in the faecal material
what is the mechanism of action for giardia?
toxins called giardins affect cntractile proteins in the gut this induces apoptosis and activation of lymphocytes; resulting in malabsorption and increased transit
how do giardia physically affect the gut?
they line the gut and damage the villi and because the cells are comparable in size to ours a large number or giardia cells can cover large areas of the body making the infection spread across a wider range
what can treat Giargia?
metronidazole
what is metronidazoles mechanism of action
the drug targets anaerobic metabolic pathways which human cells do not have
what are key charachteristics of luminal protozoan parasites? such as Giardia and other flagellate organisms
do flagellates have mitochondria?
no
how are protazoa infections diagnosed and why?
using microscopy techniques because protazoa do not form colonies on agar
what test is used to diagnose protozoa?
the ova, cyst and parasites method
cryptosporidium cell cycle
large resoevoirs in cattle herd and water run off from farm land, this pathogen can affect anybody but is more serious in immunocomprimised people
does crytosporidium have vectors?
no
what are high risk resevoirs for cryptosporidium?
large resoevoirs in cattle herd and water run off from farm land
what is the treatment and recovery like for immunocompetent people suffereing from cryptosporidiosis?
fluid and electrolyte replacment
some protective immunity comes naturally as it happens to young people who end up developing protections after exposure to the illness
illness is self limiting as it lasts 1-2 weeks
what is the treatment and recovery like for immunosuppressed people suffereing from cryptosporidiosis?
severe diarrhoea causing dehydration and weight loss
not self-limiting, there is no targeted treatment, no actual drugs that can actually kill the pathogen
vigorous rehydration and anti-diarrhoeal drugs needed
extraintenstinal infection can be fatal
how is cryptosporidiosis relevent to poverty
A major cause of childhood(<1 y.o.) diarrhoea
Associated with malnutrition
what happens to cryptosporidium when it is outside the host?
it forms cysts
are there any drugs available to treat the cryptosporidium pathogen?
there is no targeted treatment, no actual drugs that can actually kill the pathogen
is cryptosporidium an apicomplexa?
yes
what is the pathogenicity of cryptosporidium?
there is no scientiific consensus on the pathogenicity mechanism
is cryptosporidium intracellular?
it is partly intracellular
what are the possible affects crypotosporidum potentially has on host cells?
*Impaired Na+ and H2O
absorption?
*Increased Cl- secretion?- this would result in water being drawn out of cells via osmotic effect
*Induction of host cell
apoptosis?
how does cryptosporidium protect itself from the immune system
it coats itself with the host cells membrane to evaid detection
what stains can be used to easily detect cryptosporidia cysts via light microscopy?
Ziehl neelsen stain- the cryptosporidia are pink
Aurimine stain shows bright
green Cryptosporidia using
UV microscopy
Immunofluorescent stains
offer greater accuracy- but need a UV floresce microscope
what species cause acanthamoeba Keratitis?
Caused by A. polyphaga and A. castellanii
what is Keratitis?
Inflammation of cornea
who is most at risk of Acanthamoeba Keratitis
- Almost exclusive to contact lens wearers.
- Risk factors: swimming in pools, lakes or sea water while wearing contact lenses; storing lenses in home made solutions; poor lens hygiene.
what are the symptoms of Acanthamoeba Keratitis?
- Severe pain
- Redness
- Scant (if any) discharge, very unlikely to cause discharge- basically is doesnt cause discharge unlike other eye infections
- scarring and unceration of the cornea as the Acanthamoeba imbedds itself in
Proximity of eyes and brain means The protozoa also causes granulomatous encephalitis
is Acanthamoeba Keratitis
common?
yes it is extremely common in the environment, can be found in evironmental and tap water too
why can the eye being an immune privaledged site pose problems?
you tend to get limited inflammation in the ey, you do get some inflammation, but the limitated capacity meant the parasites can build up in number because the immune response in the eye is quite weak initially
what are the treatments for Acanthamoeba Keratitis ?
Treatment: multiple antimicrobials
including topical antiseptics;
hospitalization is often necessary
If severe corneal scarring occurs,
corneal transplantation may be
required
Severe loss of vision or of the eye may
occur, even if the condition is diagnosed
early and managed appropriately
- Therapy and treatment can last for
more than a year.
Acanthamoeba Keratitis – laboratory diagnosis
- Agar plate seeded with bacteria (such as E.coli) and inoculated with swab from
infected eye - Active forms of the amoeba will scoot around the plate as they
phagocytose the bacteria – the trail can be seen under a microscope - Molecular methods such as PCR, may also be used
what is the virus lipid membrane (envelope) made of?
The viral envelope is made from fatty lipids molecules taken form the host cells.
What are the main routes of protozoan transmission?
Ingestion, vector-borne, sexual contact, transovarial, and placental.
Name the four classifications of protozoa based on movement.
Ciliates, flagellates, amoebae, and Apicomplexa.
How do protozoan cysts contribute to survival?
They are dormant forms that resist environmental stress, aiding in transmission.
What is schizogony, and why is it significant?
It is asexual reproduction, producing multiple daughter cells, critical in Plasmodium spp. for rapid infection.
Which protozoa are waterborne and cause diarrheal diseases?
Cryptosporidium parvum, Cyclospora cayetanensis, Giardia lamblia, and Balantidium coli.
How do protozoa differ from bacteria in cellular structure?
Protozoa are eukaryotic with organelles, while bacteria are prokaryotic without organelles.
What are trophozoites in protozoan lifecycles?
The active, feeding, and reproducing stage.
What distinguishes Apicomplexa from other protozoan groups?
They have a unique apical complex for host cell invasion.
How does the size of protozoa compare to bacteria?
Protozoa are larger, often comparable to human cells.
Why is microscopy the gold standard for diagnosing protozoan infections?
Protozoa cannot form colonies on agar plates, so direct visualization is necessary.
How do protozoa cause host cell damage?
Through physical destruction, toxin release, or immune response activation.
What is the primary difference between vector-borne and waterborne protozoa?
Vector-borne protozoa require an intermediate host, while waterborne protozoa are typically ingested.
Name a sexually transmitted protozoan.
Trichomonas vaginalis.
How do amoebae like Acanthamoeba spp. move?
By extending pseudopodia.
What are the primary environmental conditions for protozoa survival?
Moisture, nutrients, and moderate temperatures.
How does Cryptosporidium parvum resist water treatment?
It forms oocysts that resist chlorine and filtration.
Why are protozoan diseases more prevalent in developing countries?
Poor sanitation, unsafe water, and lack of healthcare infrastructure.
What distinguishes trophozoites from cysts?
Trophozoites are metabolically active, while cysts are dormant and resistant.
Why is Giardia lamblia reclassification important?
Its various names (G. intestinalis, G. duodenalis) reflect its taxonomy and prevalence in literature.
What are the key characteristics of protozoa that impact their pathogenicity?
Ability to invade host cells, evade immune responses, and transition between life stages.
Name five protozoa that cause waterborne diseases.
Cryptosporidium parvum, Cyclospora cayetanensis, Giardia lamblia, Balantidium coli, Acanthamoeba spp.
What is the primary disease caused by Cryptosporidium parvum?
Cryptosporidiosis.
How is Giardia lamblia transmitted?
Through ingestion of cysts in contaminated water or food.
What distinguishes Acanthamoeba spp. from other waterborne protozoa?
It causes keratitis, an eye infection, instead of gastrointestinal disease.
How does Cryptosporidium parvum cause diarrhea?
By impairing Na+ and water absorption and inducing host cell apoptosis.
What diagnostic stain is used for Cryptosporidium detection?
Ziehl-Neelsen or immunofluorescent staining.
What are the symptoms of giardiasis?
Chronic diarrhea, malabsorption, abdominal cramps, and fatigue.
How do Giardia trophozoites damage the gut?
By attaching to the intestinal lining, causing villous atrophy and malabsorption.
What role does Acanthamoeba spp. play in encephalitis?
It can spread to the brain from the eye, causing granulomatous encephalitis.
What is the primary treatment for giardiasis?
Metronidazole.
How does Acanthamoeba keratitis primarily occur?
From contaminated contact lenses or poor lens hygiene.
What are the symptoms of Cryptosporidium infection in immunocompromised patients?
Severe diarrhea, dehydration, and weight loss.
How is Balantidiasis transmitted?
By ingestion of cysts in contaminated water or food.
What are oocysts in Cryptosporidium?
Dormant forms that resist harsh environments and aid in transmission.
How can waterborne protozoa be controlled?
By improving water treatment, sanitation, and public health education.
Why is Cryptosporidium difficult to eliminate in water supplies?
It resists conventional chlorination and small filtration systems.
How does Cyclospora cayetanensis differ from Cryptosporidium?
It causes prolonged diarrhea and is primarily linked to contaminated produce.
What are the symptoms of Acanthamoeba keratitis?
Severe eye pain, redness, and potential vision loss.
Why is Acanthamoeba keratitis difficult to treat?
Antimicrobials poorly penetrate the cornea, requiring prolonged and intensive therapy.
What are granulomatous amoebic encephalitis risk factors?
Immunosuppression and environmental exposure to Acanthamoeba-contaminated water.
What are the two major forms of human African trypanosomiasis?
T. brucei gambiense (chronic) and T. brucei rhodesiense (acute).
What is the vector for malaria?
Female Anopheles mosquitoes.
Name the protozoa that causes Chagas disease.
Trypanosoma cruzi.
What is Romana’s sign in Chagas disease?
Swelling near the eye due to Triatomine bug feces.
How does Leishmania spp. evade the immune system?
By surviving within host macrophages.
What are the clinical forms of leishmaniasis?
Cutaneous, mucocutaneous, and visceral.
How is American trypanosomiasis transmitted?
By Triatomine bug bites or contaminated food.
What are the symptoms of visceral leishmaniasis?
Fever, weight loss, anemia, and hepatosplenomegaly.
How does Plasmodium spp. cause cyclical fever?
Through synchronized rupture of red blood cells releasing merozoites.
What is the role of sandflies in transmitting Leishmania?
They serve as vectors, transmitting the parasite during feeding.
What are the stages in Trypanosoma brucei infection?
Chancre formation, hemolymphatic stage, and meningoencephalitic stage.
How is malaria treated?
Using antimalarial drugs like chloroquine and artemisinin.
What is the vector for babesiosis?
Ticks, primarily Ixodes species.
What are the symptoms of cutaneous leishmaniasis?
Skin sores with raised edges and central craters.
How does trypanosomiasis lead to neurological symptoms?
Parasite invasion of the central nervous system.
What are the symptoms of acute Chagas disease?
Fever, swelling at the infection site, and lymphadenopathy.
Why is vector control critical in managing protozoan diseases?
It interrupts the lifecycle of the pathogen and reduces transmission.
How does the kinetoplast in Trypanosoma aid its survival?
It facilitates energy metabolism and is a drug target.
What drugs are used to treat sleeping sickness?
Suramin for early stages and eflornithine for later stages.
What are the major complications of chronic Chagas disease?
Cardiac damage and megaviscera.
What are the primary diseases caused by Giardia lamblia?
Giardiasis, characterized by chronic diarrhea, malabsorption, and abdominal discomfort.
How does Giardia lamblia cause malabsorption in the intestines?
By attaching to the intestinal lining, damaging villi, and interfering with nutrient absorption.
What is the prevalence of Giardia infections in developed vs. developing countries?
Developed countries: 2–7%; Developing countries: 20–30%.
What are the long-term effects of chronic giardiasis?
Persistent diarrhea, fatigue, abdominal pain, and symptoms resembling irritable bowel syndrome (IBS).
What is the role of cysts in the lifecycle of Giardia lamblia?
Cysts are the dormant, environmentally resistant form that aids in transmission and survival outside the host.
How is cryptosporidiosis transmitted?
Through ingestion of oocysts in contaminated water or food, or direct contact with infected individuals or animals.
What are the symptoms of cryptosporidiosis in immunocompetent individuals?
Self-limiting diarrhea lasting 1–2 weeks, abdominal cramps, and nausea.
Why is cryptosporidiosis more severe in immunocompromised patients?
They cannot clear the infection effectively, leading to prolonged diarrhea, dehydration, and potentially systemic infection.
What is the diagnostic method for Cryptosporidium?
Microscopy with Ziehl-Neelsen stain or immunofluorescent staining to detect oocysts in stool samples.
What factors increase the risk of cryptosporidiosis outbreaks?
Heavy rainfall causing runoff of contaminated animal feces into water supplies.
How does Cryptosporidium impair intestinal function?
By inducing host cell apoptosis and disrupting ion transport, leading to diarrhea.
What treatment options are available for cryptosporidiosis?
Supportive care with fluid and electrolyte replacement; no effective targeted antimicrobial therapy exists.
How does Balantidium coli differ from other waterborne protozoa?
It is a ciliate and primarily causes balantidiasis, which includes symptoms of severe dysentery.
What are the risk factors for acquiring Acanthamoeba keratitis?
Contact lens use, exposure to contaminated water, and poor lens hygiene.
What are the symptoms of Acanthamoeba keratitis?
Severe eye pain, redness, blurred vision, and potential vision loss.
Why is Acanthamoeba keratitis rare but serious?
It often requires intensive treatment and can lead to permanent vision damage or eye loss.
How does Acanthamoeba cause keratitis?
By attaching to the cornea, releasing cytotoxic enzymes, and penetrating deeper eye tissues.
How is Acanthamoeba keratitis diagnosed?
Using agar plates seeded with bacteria to detect amoebic trails, or PCR for molecular identification.
What is Cyclospora cayetanensis, and how is it transmitted?
A protozoan that causes cyclosporiasis, transmitted through contaminated fresh produce and water.
What are the symptoms of cyclosporiasis?
Watery diarrhea, bloating, fatigue, and loss of appetite, often lasting several weeks.
How is Cyclospora cayetanensis diagnosed?
Through stool examination using UV fluorescence or modified acid-fast staining.
What are the common reservoirs for Cryptosporidium in the environment?
Lakes, rivers, and water runoff contaminated with animal feces, particularly from cattle.
How do waterborne protozoa survive in unfavorable environmental conditions?
By forming cysts or oocysts that are resistant to desiccation, chlorine, and other treatments.
What is the primary method for preventing waterborne protozoan infections?
Ensuring safe drinking water through filtration and proper sanitation.
Why is Cryptosporidium difficult to remove from drinking water supplies?
Its oocysts are small and resistant to standard filtration and chlorine-based treatments.
How does Cyclospora differ from Cryptosporidium in its clinical presentation?
Cyclospora causes longer-lasting diarrhea and is often associated with outbreaks linked to contaminated produce.
What are the symptoms of Balantidiasis?
Diarrhea, abdominal pain, nausea, and sometimes dysentery with blood and mucus in the stool.
Why is Acanthamoeba not typically considered a gastrointestinal pathogen?
It primarily infects the eyes or brain rather than the gut.
How can Acanthamoeba keratitis be prevented?
By using sterile solutions for contact lenses, avoiding tap water for rinsing, and practicing proper lens hygiene.
What is the significance of villous atrophy in Giardia infections?
It reduces the absorptive surface of the intestines, leading to malabsorption and diarrhea.
what dot he surface proteins on the virus lipid membrane do?
These help the virus recognise and bind to cells in the host organism
what is the purpose of the Genetic material(DNA or RNA)
The virus genetic material contains the instructions for making new copies of the virus
why is the protein coat for a virus needed?
The capsid contains the virus genetic material
draw a diagram of a virus
what is something all viruses have?
a viral genome (DNA or RNA) and a viral capsid (protein coat)
why is an envelope important for a virus?
Envelope = lipid bilayer with glycoproteins, can helpvirus bind to cells
is a virus more stable with or without an envelope?
viruses without an envelope are more stable and more resistant to pH, temperature changes and the air.
do enveloped viruses get into your cells easier?
yes because of the lipid bilayer with the surface proteins.
what is the helical capsid formation?
there is a directional assembly around the genome
what is the icosahedric capside formation?
there is assembly/packaging around the genome
what is a scaffolded icosahedric capsid?
Capsid assembly: formation of the capsid shell.
Packaging: viral genome placement inside a capsid or an envelope
what is acapsid
a very strong Closed 3-dimensional structure
No holes - to remain Stable
Built of repeating protein structures
how are capsids formed?
by the self assembly of viral protein subunits into different capsomers which then undergo self assembly to form a spherical viral capsid
what is the viral envelope?
a lipid bilayer
what is the viral envelope involved with?
virus attachment to cells- Envelope proteins recognised by cellular receptors
Can fuse with the hose cell membrane
how can a virus exit a cells machinery?
Virus can exit cells using the cell machinery-
Can avoid cell damage (potentially avoiding the immune response!)- the virus envelope is most important for exiting the cells, the virus is able to co-opt the host cell membrane and use it to hide from the host immune system- it does not need to produce its own cell membrane
why do non-enveloped viruses usually cause more damage?
When exiting cells they disrupt the integrity of the membrane and can cause cell lysis.
how are non enveloped viruses more stable?
Non-enveloped viruses are more resistant to pH, heat, dryness, alcohol, soap!
how do enveloped and non-enveloped viruses enter the cell differently?
define a capside
a protein coat that encloses and protects the genetic material/genome.
define a capsomer
clusters of proteins that compose
The capsid
define a protein envelope
a lipid bilayer that surrounds the capsid
of some viruses.
define a peplomer
Proteins on the envelope of the virus
(like Glycoprotein)
what is a virion?
A Complete virus particle or infectious particle is called a VIRION
why is Knowing the structure of viruses important?
Can help in creating treatments
Can help in developing vaccines
Knowing what kills the viruses (soap, alcohol, bleach)
how are viruses grouped?
based on phenotypic characteristics
-Morphology
Nucleic acid type (DNA/RNA)
Replication cycle in the cells
Host
Disease caused
what does a viridae refer too?
a specific family of viruses
what do all viruses need to produce?
mRNA
what is the Baltimore classification system used?
classify viruses based on their manner of messenger RNA (mRNA) synthesis.
why is it difficult to classify viruses?
We don’t know all properties of viruses or all known viruses
We do not know if viruses have a one common ancestor
Viruses can mutate and change
Polythetic classification (as opposed to monothetic!)
No single property but a portfolio of properties: target cells, biochemistry, structure and mainly now genome sequences
Related viruses share many of these, but often not all.
what is a susceptible cell?
A susceptible cell has a functional receptor for a given virus - the cell may or may not be able to support viral replication
what is a resistant cell?
A resistant cell has no receptor - it may or may not be competent to support viral replication
what is a permissive cell?
A permissive cell has the capacity to replicate virus - it may or may not be susceptible
what is a susceptible AND permissive cell
A susceptible AND permissive cell is the only cell that can take up a virus particle and replicate it
how does pH allow genetic material to be released from virus cells?
within the cells endosomes can be formed, when the virus is in the endosome the pH changes, this causes the capsid to release the genetic information stored in the virus and allows the virus to replicate.
what are the stages of the viral infectious cycle?
Very simply the viral life cycle is:
1. Attachment to cells
2. Enter & uncoating
3. mRNA
3. Translation using host ribosomes
4. Assembly
5. Egress (exit)
what is viral pathogenesis?
Viral Pathogenesis: the process by which a virus causes a disease
what is viral virulence?
Virulence can be quantitated:
- Virus titer
- Mean time to death
- Mean time to appearance of signs
- Measurement of fever, weight loss
Many signs/symptoms of disease are caused by immune response!
what is the difference between signs and symptoms?
Symptoms = What only you can feel
Signs = what others detect
what can viral virulence be influenced by?
Influenced by dose, route of infection, species, age, sex, and susceptibility of host
Not correct to compare virulence of different viruses
what does virulence depend on?
how do viruses affect us?
how can viruses be useful?
Oncolytic viruses
Alternatives to antibiotics
Gene therapy
Biological control-an alternative to pesticides?
what do we need to study viruses?
we must have living appropriate cells to study viruses
how can we grow viruses for studying?
using cell cultures with HeLa cells
and HEp-2 cells or we can
embtyonated eggs can be used to develope vaccines
in vivo (live animals)
what is the cytopathic affect?
Cytopathic effect (CPE) is the term used to describe the structural changes that occur in a host cell after it has been infected by a virus
how can the cytopathic effect be important in cell culture
- in cell culture, testing for cytopathic effect can help to quantify the effect a virus has on susceptible and permissible cells by showing how thye can cause cell damage and death
- a cytopathic effect shows damage and changes to cells
Why are virus diagnostics needed?
- Appropriate management of patients.
- Routine public health measures
- Surveillance
why is Appropriate management of patients improtant?
Avoids further unnecessary testing
Avoids unnecessary drug use (antibiotics!)
Informs patient treatment and prognosis
Are treatment strategies working (viral load testing)
why are virus diagnostics needed for Routine public health measures necessary?
Screening of donated blood (HIV, HepB, HepC)
Notifiable infections (Measles, Rubella, Mpox, etc.)
Activate contact tracing
Limit spread or outbreak
Put mechanisms in place to contain and eradicate
Surveillance
why are virus diagnostics needed for Surveillance?
To monitor the significance and prevalence of viruses in a community.
Monitoring and tracking of outbreaks (e.g. COVID-19)
Evidence of reemerging or emerging viruses –
Individuals travelling from other countries (e.g. polio in London).
Viruses spreading within animal communities (e.g. H5N1).
Viruses with zoonotic potential
What is the definition of a virus?
A virus is an obligate intracellular parasite comprising genetic material (DNA or RNA), often surrounded by a protein coat (capsid) and sometimes a lipid membrane (envelope).
What are the two types of viral genetic material?
DNA and RNA.
What is the function of the viral capsid?
To protect the viral genome and assist in delivering it to host cells.
What is the difference between enveloped and non-enveloped viruses?
Enveloped viruses have a lipid bilayer with glycoproteins, making them less resistant to environmental conditions; non-enveloped viruses are more resistant and often cause more cellular damage.
How do surface proteins on viruses aid infection?
They help the virus recognize and bind to host cell receptors for entry.
What are the three forms of viral capsids?
Helical, icosahedral, and scaffolded icosahedral.
How are viruses classified under the Baltimore classification system?
Based on their nucleic acid type, sense (positive or negative), and method of replication.
What are the main stages of the viral life cycle?
Attachment, entry and uncoating, mRNA production, protein synthesis, assembly, and egress.
What is a virion?
A complete infectious virus particle.
What is the significance of viral genome integration into host DNA?
It can contribute to long-term infections, oncogenesis, or beneficial adaptations, such as the formation of the human placenta.
What is viral tropism?
The specificity of a virus for a particular host cell type, determined by receptor compatibility.
How does the host immune system contribute to disease symptoms?
Many symptoms, such as fever and inflammation, result from the immune system’s response to infection.
What methods are used to study viral capsid structures?
Techniques like cryo-electron microscopy (cryo-EM).
What factors influence viral virulence?
Dose, route of infection, host species, age, sex, and immune status.
Why are non-enveloped viruses more resistant to environmental factors?
They lack a fragile lipid envelope and rely on a robust capsid for protection.
What are examples of diseases caused by RNA viruses?
Influenza, HIV, and SARS-CoV-2.
How do viruses like HIV evade immune detection?
By using host cell membranes as an envelope and integrating their genome into host DNA.
What are examples of viruses named after locations?
Zika virus (Zika Forest, Uganda) and West Nile virus (West Nile region).
What is the role of peplomers in viruses?
Surface glycoproteins involved in receptor recognition and entry.
How do antiviral treatments target viruses?
By disrupting capsid integrity, replication enzymes, or entry mechanisms.
What is viral pathogenesis?
The process by which a virus causes disease in a host.
What are the two main contributors to viral disease symptoms?
Effects of viral replication and the host immune response.
What is the difference between acute and long-term viral infections?
Acute infections cause rapid onset of symptoms and resolution, while long-term infections persist and may involve latency.
Name a virus that causes oncogenesis.
Human papillomavirus (HPV), which is associated with cervical cancer.
How does HIV affect the immune system?
It infects CD4+ T cells, weakening the immune response and leading to AIDS.
What is the primary symptom of respiratory syncytial virus (RSV) infection in children?
Severe lower respiratory tract infections.
How does the influenza virus evade the immune system?
Through antigenic drift and shift, leading to changes in surface proteins (H and N).
What is the significance of the 1918 influenza pandemic?
It caused widespread mortality, killing an estimated 20 million people worldwide.
What are zoonotic viruses?
Viruses that are transmitted from animals to humans, such as SARS-CoV-2.
What role do bacteriophages play in the environment?
They infect bacteria, contributing to microbial balance and nutrient cycling.
How is viral virulence quantified?
By measuring virus titer, mean time to death, symptom severity, and weight loss in experimental models.
What is the economic impact of viruses on agriculture?
Viruses like tomato spotted wilt virus cause significant crop losses, estimated at billions of dollars annually.
Name an example of a beneficial virus.
Oncolytic viruses, which can selectively kill cancer cells.
How does viral resistance to treatment occur?
Through mutations in viral genes targeted by antiviral drugs.
What is the impact of Ebola virus outbreaks on local economies?
Decreased trade, tourism, agricultural production, and economic growth.
What are the symptoms of measles?
High fever, cough, runny nose, conjunctivitis, and a characteristic rash.
How do phage therapies work?
By using bacteriophages to specifically target and kill antibiotic-resistant bacteria.
What is the relationship between viruses and the human microbiome?
The human virome includes viruses that coexist with bacteria and contribute to immune modulation.
How does viral integration affect human evolution?
Endogenous viral elements in DNA have influenced traits like placental development.
How are viruses used in gene therapy?
As vectors to deliver therapeutic genes to correct genetic disorders.
What are the components of a typical virus?
Genetic material, capsid, and sometimes an envelope with surface proteins.
How are viruses classified phenotypically?
By morphology, genome type, replication method, host range, and disease caused.
What is the Baltimore classification system?
A system that groups viruses into seven categories based on mRNA synthesis methods.
What are double-stranded RNA viruses, and why are they rare?
Viruses with both strands of RNA; this structure is uncommon in nature.
How does the viral envelope facilitate infection?
It allows fusion with host cell membranes for genome entry.
What is the main function of the capsid?
To protect the viral genome from environmental damage.
How do helical capsids differ from icosahedral capsids?
Helical capsids coil around the genome, while icosahedral capsids form geometric shells.
What is the significance of viral symmetry?
It ensures capsid stability and efficient genome packaging.
Why are non-enveloped viruses more environmentally stable?
They lack a fragile lipid bilayer, making them resistant to desiccation and heat.
How does viral mutation impact classification?
Mutations can change surface proteins and replication mechanisms, altering classification.
What is the importance of surface proteins in vaccines?
They are targets for immune system recognition and response.
How does viral size compare to bacteria?
Viruses are much smaller, often requiring electron microscopy for visualization.
What is the function of viral mRNA during infection?
It serves as a template for protein synthesis using host cell machinery.
How are viruses named?
Based on disease caused, host infected, location of discovery, or discoverers.
What are examples of viruses that cause gastrointestinal diseases?
Norovirus and rotavirus.
How does norovirus resist disinfection?
Its non-enveloped structure makes it resistant to alcohol-based sanitizers.
What are the implications of polythetic classification for virology?
It groups viruses by shared but not universal properties, reflecting their diversity.
Why are bacteriophages considered potential alternatives to antibiotics?
They specifically target bacteria without harming human cells.
How do viruses use host cell membranes for immune evasion?
By incorporating host lipids into their envelope, they camouflage themselves.
Why is understanding viral structure important for public health?
It informs disinfection methods, vaccine design, and antiviral drug development.
why is Surveillance-reported by diagnostic labs?
UK Health Safety Agency (UKHSA) (former PHE).
Reporting weekly of Notifiable diseases and Non-notifiable diseases’ insidence rates.
We could use these data to predict future peaks for increased incidence rates of infections and prepare healthcare settings for expected addmissions
what is Sentinel surveillance of Influenza-like illness (ILI)?
In addition to reported hospital testing
In Europe, ~5% of GPs are involved with sentinel surveillance
People attending the clinic with ILI have swabs sent to clinical virology labs
Monitors rates of circulating influenza and other respiratory viruses
Can see unusual patterns, monitoring of circulating sub-types
what kind of patients does Sentinel surveillance include?
it includes patients who have gone to their doctors but are not sick enough to go hospital
what is clinical virology dependent on and why?
it is dependant on good sampling
-This is very important because in many cases we are going to do diagnostics using PCR. -This is very important because in many cases we are going to do diagnostics using PCR and the nucleic acids can be degraded very quickly. So we really need to collect the sample and preserve it with nuclease inhibitors or freeze it.
what will the sample collected in clinical virology be dependent on?
The type of sample will largely be determined on the signs/symptoms of disease
This can indicate what organ systems are involved
what is a direct method to help detect an infectious virus?
Isolation of virus
Cultivation in cell culture followed by identification
what are 2 indirect methods used in clinical virology?
(indirect methods cannot detect infectious virus)
2 methods are:
Detection of virus components
Serology
what entails Detection of virus components
looking for virions, viral antigens, viral nucleic acids
what is serology?
Detection of antibodies in the patient’s serum
what is an OBLIGATE INTRACELLULAR PARASITE?
they can only be grown inside a host cell
what is the “host range”?
gFor new viruses very often trial and error to find out what the virus can infect-the ‘host range’
to figure this out we can use cell lines, embryonated eggs or live animals (in vivo)
why can cell lines be useful in studying viruses?
hen you culture a virus into a cell line, you can, for instance, do microscopy and look for cytopathic effect. You can see the comparison between a culture that has and has not been infected. And you can look at the cells, the morphology, the shape and decide whether something about the cells is changing
what kind of assay can be used to study the cytopathic effect?
plaque assay
- it is a Key technique in virology.
Time-consuming and not suitable for all viruses.
Mostly research technique, but still used in diagnostics (enrichment).
what are plaque forming units?
Viruses will spread by probability to the surrounding cells better than any other cells further away. So in the end, if the virus causes a cytopathic effect it will cause a hole in the monolayer that can be detected by staining or by the naked eye, and we don’t know how many viral particles are in there. What we know is that that is the plaque forming unit.
does plaque assay use living cells?
yes
what kind of seuqencing can you use when the target virus is unknown?
metagenomic sequencing
what kind of sequencing can be used when you know or suspect the virus?
amplicon sequencing that amplifies a region of the viral genome
how can virus sequencing be used to detect and stop new viruses spreading?
new sequences can be sequenced using metagenomic sequencing and aligned to known virus sequences
If it is an unknown virus, similarities in related viruses can be identified
From the sequencing, you could predict whether the virus might resist particular treatment of particular or be susceptible to a particular treatment. you could test for mutations via sequencing and changes to the genome of known viruses
what is direct detection?
Detection of virions, viral nucleic acids or viral antigens
what is a virion?
Virion: A complete virus particle
what is viral nucleic acid?
Viral nucleic acid: the genetic material of a virus, either RNA or DNA
what is a virus antigen?
Antigen: molecular structures on the surface of viruses that can be recognized by the immune system
how does a florescence microscope make use of antibodies?
antibodies are very specific, So they become a great tool for diagnostics because they can identify a particular molecule or component in a very specific wayWe can take advantage of antibodies, make them against a particular antigen, and then we can label them.We can label them with enzymes or fluorophores something that allows us to visualise the presence of that antibody.
When we want to use this in terms of microscopy, what we do is we incubate the antibodies with the sample normally on a glass surface, and then we can either couple a second antibody or directly detect the floraphores for the was attached to it. And then you get images that come through for us and that gives us much more sensitivity and also provides the specificity of knowing we are detecting a particular antigen.
what are negri bodies?
negri bodies can be detected to determine whether someone has rabies
what are the pros and cons of using an electron microscope?
Much better resolution than a light microscope.
A scanning transmission electron microscope has 50 pm resolution
Most light microscopes are limited to about 200 nm
Can view the structure of virions
During the 1970s new groups of hard to culture viruses discovered in faeces (rotaviruses, calciviruses, astroviruses, HepA)
One method: negative staining. Virus dilution on carbon coated grid. Virions adhere to the surface. Electron dense fluid added and surrounds virions.
Thin tissue sections can also be imaged.
Low sensitivity (need 106 virions/mL, ok for faeces but difficult for respiratory samples).
Impractical for large scale testing.
pros and cons of PCR for testing viral nucleic acids
Polymerase Chain Reaction
Quick and (fairly) easy
Can be easily scaled up for high-throughput testing
Initially expensive, but cheaper in high volume
Very sensitive and highly specific
Can be quantitative (qPCR)
A positive PCR may not indicate active infection
Why do you think this might be?
So detecting the viral nucleic acid doesn’t mean you’re detecting an infection. It can mean youre detecting part of the virus. But in many cases, after a viruses infects you the genome of the virus can hang around for a really long time.
explain the process of rt-PCR
explain the process of qPCR
explain the process of RT-qPCR
You can measure light in the machine as the reaction happens to determine how much viral material is present in the sample
what does a low amount CT value for rt-qPCR mean
there is alot of viral material
what does a high-ct value mean?
there is very little viral material present becuase you need to do more cycles to reacht the light threshold to determine a positive result.
what is a cycle threshold?
The number of cycles of PCR needed until the sample is detectable.
The lower the number, the less cycles, the more viral nucleic acids present.
what is serology?
Serology is the scientific study of serum and other body fluids. In practice, the term usually refers to the diagnostic identification of antibodies or antigens in serum
what are serology methods?
Methods include:
ELISA
Agglutination
Precipitation
Complement fixation
what is an ELISA test?
Enzyme-linked immunosorbent assay (ELISA) or Enzyme Immunoassay (EIA)
Still used, but replaced by PCR in many instances.
An antibody to the target is absorbed on the solid surface. The unknown sample is added. If antigen (like viral protein) is present it will bind to the antibody. An enzyme labelled antibody is then added. A substrate is added. The enzyme, if present, will cause the substrate to change colour.
High sensitivity
Lots of different assay formats, easily adaptable
how does an ELISA test work?
can be direct or indirect form of ELISA
the sandwich ELISA is the most common form and works like this-
you have a plate that is coated with one particular antibody.
you would then add Your sample, presumably containing the virus or parts of the virus.
This would be recognised by this antibody, then you can wash off the rest of the sample and then you can add what we call the detection antibody,
which is another antibody that will detect the same virus or the same part of the virus.
what is a lateral flow test?
a form of Immunochromatography available for HIV, dengue, influenza, COVID-19, RSV (not all in common usage)
how do lateral flow tests work?
Antigens move through a support (filter paper, nitrocellulose film)
Labelled antibody reacts with sample containing antigen.
Second antibody produces a colour change
Can incorporate a positive and negative control
Less sensitive
Useful for rapid testing, point-of care testing
how does a Haemagglutination assay work?
also makes use of antibodies
Sialic acid receptors on RBCs bind to the HA protein on the surface of influenza and keep the RBCs in suspension.
No flu-RBCs settle
what is the difference between and accurate and precuse test?
Accurate: A test that provides a result close to the real value
Precise: A test is repeatable and the result reproducible
what is the difference between sensitivity and specificity?
Sensitivity: The probability of a positive test from a truly positive sample (true positive rate)
Specificity: The probability of a negative test from a truly negative sample (true negative rate)
why is it dififcult to diagnose viral infections?
many have similar “flu-like” symptoms because it is the bodies immune system that causes the same key symptoms not the virus itself
What is the primary goal of clinical virology?
To diagnose viral infections, monitor viral diseases, and guide appropriate patient treatment and public health responses.
Why is it challenging to diagnose viral infections based on symptoms alone?
Many viral infections share similar symptoms, such as fever, chills, and fatigue, caused by the immune response rather than the virus itself.
What is the significance of viral load monitoring in patient management?
It helps assess the effectiveness of treatment and detect potential resistance to antiviral therapies.
Name three reasons why virus diagnostics are essential.
Patient management, routine public health measures, and surveillance.
What is sentinel surveillance in virology?
A system where specific GPs or clinics collect and test swabs from individuals with influenza-like illness to monitor viral patterns.
How do public health agencies track the spread of viruses like SARS-CoV-2?
Through wastewater monitoring, hospital data collection, and sentinel surveillance systems.
What role does the UKHSA play in clinical virology?
It reports weekly on notifiable diseases and monitors circulating viruses like influenza and RSV.
Why is viral genome sequencing important in diagnostics?
It identifies novel viruses, tracks mutations, and determines susceptibility to treatments.
What is the importance of accurate sampling in viral diagnostics?
It ensures the quality of nucleic acids or antigens for reliable testing.
What are the two broad categories of virology diagnostic methods?
Direct methods (detect infectious virus) and indirect methods (detect viral components or antibodies).
What is a plaque assay, and when is it used?
A technique to quantify infectious virus by counting plaques formed in a cell monolayer; mainly used in research and antiviral testing.
How does PCR aid in detecting viral nucleic acids?
It amplifies specific viral DNA or RNA sequences, making detection highly sensitive and specific.
What is quantitative PCR (qPCR), and how does it differ from standard PCR?
qPCR measures the amount of DNA in real-time during amplification, providing both detection and quantification.
What does a low cycle threshold (Ct) value in qPCR indicate?
A high viral load in the sample.
What is multiplex PCR, and why is it advantageous?
A PCR method that detects multiple viruses simultaneously by using different fluorophores for each target.
What is the principle of ELISA in viral diagnostics?
It uses antibodies to detect viral antigens or antibodies in a sample through enzyme-substrate reactions producing color changes.
What is the purpose of a lateral flow test?
To provide rapid point-of-care detection of viral antigens, such as in COVID-19 testing.
How does haemagglutination assist in virus detection?
By observing the ability of viruses to agglutinate red blood cells, used for viruses like influenza.
What are Negri bodies, and what do they signify?
Intracellular inclusions diagnostic for rabies, detectable through fluorescence microscopy.
Why is electron microscopy valuable in virology?
It provides high-resolution images of virions, helping identify viruses that are difficult to culture.
How does metagenomic sequencing aid in identifying unknown viruses?
By sequencing all genetic material in a sample to compare against known viral genomes.
What is serology, and how is it applied in virology?
The study of serum to detect antibodies or antigens, used to confirm past or current infections.
What are the strengths of PCR in viral diagnostics?
High sensitivity, specificity, and scalability.
Why are fluorescent microscopes used in diagnostics?
They detect labeled antibodies bound to viral antigens, providing specificity and sensitivity.
What are the limitations of using light microscopy for viral detection?
Poor resolution for small viruses and inability to detect specific viral features.
What factors influence the choice of diagnostic technique?
Suspected virus, sample type, clinical urgency, and resource availability.
What are the common viral causes of aseptic meningitis?
Enteroviruses (Coxsackie, echovirus) and mumps.
What are the uncommon viral causes of aseptic meningitis?
Polio, LCMV, HSV-2, and adenovirus.
What specimens are collected for diagnosing aseptic meningitis?
NP-throat, CSF, urine, stool, and serum for LCMV.
What are the common viral causes of encephalitis?
Arboviruses and HSV-1/-2.
What are the uncommon viral causes of encephalitis?
Mumps, measles, influenza, rubella, VZV, rabies, EBV, and enteroviruses.
What specimens are collected for diagnosing encephalitis?
NP-throat, stool, CSF, brain biopsy (if herpes is suspected), and serum.
What are the common viral causes of URI, bronchitis, or ‘flu’?
Rhinovirus, parainfluenza, influenza, adenovirus, enteroviruses, and RSV.
What are the uncommon viral causes of URI, bronchitis, or ‘flu’?
Measles, coronaviruses (NL, HK), and bocavirus.
What specimens are collected for URI, bronchitis, or ‘flu’?
NP-throat and nasal aspirate.
What is the common viral cause of croup?
Parainfluenza.
What are the uncommon viral causes of croup?
RSV, adenovirus, and influenza.
What specimens are collected for diagnosing croup?
NP-throat and nasal aspirate.
What are the common viral causes of pneumonia?
RSV, adenovirus, influenza, and metapneumovirus.
What are the uncommon viral causes of pneumonia?
Parainfluenza, CMV, rhinovirus, measles, rubella, and enterovirus.
What specimens are collected for diagnosing pneumonia?
NP-throat, stool, tracheal aspirate, nasal aspirate, urine, and serum.
What are the common viral causes of bronchiolitis?
RSV and influenza.
What is an uncommon viral cause of bronchiolitis?
Parainfluenza, adenovirus, and rhinovirus.
What specimens are collected for diagnosing bronchiolitis?
NP-throat and nasal aspirate.
What are the common viral causes of vesicular rashes?
VZV, HSV-1, and HSV-2.
What are the uncommon viral causes of vesicular rashes?
Vaccinia and enteroviruses.
What specimens are collected for vesicular rashes?
Vesicular fluid, NP-throat, stool (for enterovirus), and serum.
What are the common viral causes of non-vesicular rashes?
Measles, rubella, and enterovirus.
What are the uncommon viral causes of non-vesicular rashes?
EBV and hepatitis B virus.
What specimens are collected for non-vesicular rashes?
NP-throat, stool (for enterovirus), and serum.
What are the common viral causes of congenital infections?
CMV, HSV-2, and rubella.
What are the uncommon viral causes of congenital infections?
Parvovirus B19.
What specimens are collected for congenital infections?
NP-throat, stool, pleural fluid, pericardial fluid, and serum.
What are the common viral causes of eye lesions?
HSV-1, HSV-2, and adenoviruses.
What is an uncommon viral cause of eye lesions?
Measles.
What specimens are collected for diagnosing eye lesions?
Eye swabs, NP-throat, and nasal washing.
What are the common viral causes of gastroenteritis?
Rotavirus, norovirus, and adenovirus.
What are the uncommon viral causes of gastroenteritis?
Enterovirus (newborns) and influenza.
What specimens are collected for diagnosing gastroenteritis?
Stool, NP-throat, and urine.
What are the common viral causes of hepatitis?
Hepatitis A, B, C, D, EBV, CMV, and VZV.
What are the uncommon viral causes of hepatitis?
Enterovirus, adenovirus, and HSV-1/-2.
What specimens are collected for diagnosing hepatitis?
Serum, NP-throat, stool, and urine.
What are the common viral causes of parotitis?
Mumps and parainfluenza.
What are the uncommon viral causes of parotitis?
Adenovirus, LCMV, EBV, and enterovirus.
What specimens are collected for diagnosing parotitis?
NP-throat, urine, nasal aspirate, and serum.
What are the advantages of virus isolation as a diagnostic method?
Produces further material for studying the agent, usually highly sensitive, and is ‘open-minded’ (applicable to unknown agents).
What are the disadvantages of virus isolation?
It is slow, time-consuming, expensive, requires selection of appropriate cell type, and is useless for non-viable viruses or non-cultivable agents.
What are the advantages of electron microscopy in virology diagnostics?
Rapid, detects viruses that cannot be grown in culture, detects non-viable viruses, and is ‘open-minded.’
What are the disadvantages of electron microscopy?
It is relatively insensitive, cumbersome for large sample numbers, and limited to detecting a few infections.
What are the advantages of serological identification methods like EIA?
Rapid, sensitive, provides serotype information, and readily available as diagnostic kits.
What are the disadvantages of serological identification?
Not applicable to all viruses, interpretation can be difficult, and it is less sensitive than PCR.
What are the advantages of PCR for detecting viral genomes?
Rapid, very sensitive, applicable to all viruses including non-cultivable ones, can be multiplexed, allows good quantitation of viral load, and additional reagents/primers can be easily made.
What are the disadvantages of PCR?
High sensitivity may detect irrelevant co-infections, risk of DNA contamination, requires good quality control, and is targeted to specific agents.
What are the advantages of using antibody seroconversion in diagnostics?
Useful for excluding or confirming past infections when direct detection samples are unavailable.
What are the disadvantages of antibody seroconversion?
It is slow, retrospective (requires paired sera), and not suitable for rapid diagnosis.
What are the advantages of IgM serology in viral diagnostics?
Rapid and useful for diagnosing recent infections.
What are the disadvantages of IgM serology?
Interpretation can be difficult, targeted to specific agents, and false positives may occur.
What is the primary aim of this viral diagnostics practical?
To interpret and perform various diagnostic assays for viruses, including PCR, haemagglutination, haemagglutination inhibition assays, and plaque assays, to diagnose infections and determine viral characteristics.
Why is it important to use multiple assays for diagnosing viral infections?
Each diagnostic assay has advantages and limitations, so combining assays provides a comprehensive diagnosis and helps guide effective treatment plans.
What safety precautions must be followed during the practical?
Wear appropriate PPE (lab coat, gloves, safety spectacles), avoid handling mobile phones, keep benches clean, and properly dispose of waste according to lab protocols.
What is the purpose of using PCR in this experiment?
To identify the presence of common respiratory viruses in patient samples by amplifying specific viral genomic sequences.
Why can a single PCR reaction distinguish between seven respiratory viruses?
Specific primers are designed to amplify unique sequences from each virus, allowing differentiation based on band patterns in agarose gel electrophoresis.
What are the justifications for using PCR as a diagnostic tool?
It is highly sensitive, specific, and rapid, making it effective for detecting viral genomes even at low concentrations.
What does the absence of a band in PCR results indicate?
It indicates that no viral genomic material was detected in the sample, either due to the absence of the virus or an inadequate sample.
What is the purpose of the haemagglutination assay in this experiment?
To quantify the total number of viral particles in patient samples by measuring their ability to agglutinate red blood cells (RBCs).
How is the haemagglutination titre calculated?
It is determined as the highest dilution (lowest concentration) that still causes haemagglutination.
What is the significance of haemagglutination in viral diagnostics?
It provides a relative measure of the viral particle count in a sample, though it does not indicate infectivity.
Why are sheep erythrocytes used in the HA assay?
They are highly sensitive to haemagglutination by many viruses, including influenza.
Why does the assay not provide information about infectivity?
It measures total viral particles, including both infectious and non-infectious forms.
What is the purpose of the haemagglutination inhibition assay in this practical?
To identify the specific subtype of influenza virus infecting each patient by testing the ability of antibodies to inhibit haemagglutination.
How does the HI assay work?
Antibodies specific to a virus bind its antigens, preventing the virus from agglutinating red blood cells. If haemagglutination is inhibited, the virus-antibody match is confirmed.
Why are positive controls (H1N1 and H3N2) used in the HI assay?
To validate the assay and ensure that the antibodies are functioning correctly.
What justifies the use of the HI assay in diagnosing influenza subtypes?
It is rapid, specific, and effective for differentiating between influenza A subtypes, critical for targeted treatment and surveillance.
What does a red pellet formation in the HI assay indicate?
That haemagglutination was inhibited, suggesting a specific virus-antibody match.
What is the purpose of the plaque assay in this experiment?
To measure the level of infectious virus in patient samples and assess susceptibility to the antiviral drug oseltamivir (Tamiflu).
How is the infectious virus titre calculated in a plaque assay?
By counting the number of plaques formed, adjusting for the sample volume, and correcting for the dilution factor.
What is the significance of comparing plaque assay results with HA assay results?
It allows differentiation between total viral particles and infectious viral particles, highlighting the proportion of the virus that is infectious.
How can oseltamivir susceptibility be tested in the plaque assay?
By observing changes in plaque count or appearance when the virus is cultured in the presence of oseltamivir.
Why is the plaque assay important for guiding treatment plans?
It determines viral infectivity and drug susceptibility, essential for selecting effective antiviral therapies.
What are the two influenza A subtypes circulating in humans?
H1N1 and H3N2.
Why are H5N1 and H7N9 subtypes concerning for public health?
They cause severe respiratory infections with high mortality rates and are transmitted inefficiently between humans, but mutations could increase their transmissibility.
What are the two classes of antiviral drugs used for influenza treatment?
Neuraminidase inhibitors (e.g., oseltamivir) and adamantanes (e.g., amantadine).
What are the symptoms of severe lower respiratory tract infections caused by influenza?
Persistent coughing, difficulty breathing, fever, and fatigue.
How does oseltamivir reduce the spread of influenza virus?
By inhibiting the neuraminidase enzyme, it prevents the release of new virions from infected cells.
Why is it important to vaccinate against influenza annually?
The vaccine protects against circulating strains, which change frequently due to antigenic drift.
Why are multiple diagnostic assays needed for viral identification?
Each assay provides unique information, such as total viral particles, infectivity, or subtype, which are collectively necessary for accurate diagnosis.
name the key steps in the viral life cycle
what methods can viruses take to enter cells
uncoating at the plasma membrane and uncoating within endosomes
what is necessary for a virus to enter into a cell
Glycoproteins on the surface of the virus will recognize attachment and entry receptors to initiate the penetration of the viral particle in the cells. And those receptors also make the specificity of the cells to be permissive to the entry of the virus.
viruses enter specific cells due to the receptor specificity
are viruses and receptors specific
Different viruses can bind to same receptors (e.g: Adenovirus and Coxsackievirus B3)
Same virus can bind to multiple receptors (e.g: Retroviruses can bind to 16 receptors) and cause damage to multiple different tissues
what are the two modes of virus entry?
what is the main dofference between a virus fusing with the cell membrane vs a virus forming an endosome to enter a cell?
when a virus fuses with the cell membrane it expresses all the glycoproteins on the surface of the cell, this can indicate to the immune system that the cell is infected
how does uncoating of the viral particle from its vesicle happen?
what is translational shutoff?
One well studied viral strategies is the translational shutoff:
- Virus stop cellular translation
- Use the translation complex for its own translation
where does dsDNA replication occur?
in the cell nucleus.
uses RNA polymerase 2 to develope mRNA that travels to the cytoplasm and forms proteins needed to create its virus, such as herpes simplex virus
how does ssDNA replication occur?
DNA can be positive or negative, DNA dependant RNA polymerase synthesises viral mRNA which can be exported to the cytoplasm to create a viral protein.
here we also have a supplementary step to produce a virus where the viral double stranded DNA will be seperated again into a negative and positve strand which can then be encapsulated into a virus once again
how do ssRNA (+) viruses create their own genomes?
they use the proteins they produce to create more viral RNA by creating their own RNA dependant RNA polymerase encoded by the virus
how do ssRNA (-) viruses create their own genome
mainly cytoplasmic but can occur in the nuclease (influenza virus) potentially because the virus is trying to hide
the negative RNA is used to produce a positive strand that can then uses host ribosomes in the cytoplasm to produce proteins
the positive strande formed also uses RNA dependant RNA polymerase encoded by the virus to replicate and create more negative ssRNA to be encapsulated into the virus
how does retrovirus form proteins?
once the VIrus enters the host cell it will import its genetic material, positive RNA, to the nucleus where it is converted to negative dsDNA using reverse transcriptase and RNA dependant DNA polymerase; the dsDNA will then create proteins and more viral particles using host machinery
what are secretory pathways important for enveloped viruses?
Often enveloped viruses use secretory pathways to assemble, mature, and egress the cell.
once encapsulation occurs the virus can use the ER to create its own envelope and mature from the ER to the golgi where it uses the low pH of the exosomes it enters to mature the envelope proteins and egress the cell; not all virions mature correctly; not all end up being capable of being infectious
why is cellular exocytosis pathway popular for many viruses?
Cellular exocytosis pathway is very popular mainly because it is not disturbing the cell and once you are in the vesicles you are protected from immunde detection
what are the steps for when a virus is budding off an infected cell
what happens during non-lytic vial egress?
the virus can use double membrane-vesicles formed via autophagy, the viral particles remain in the vesicles where they mature until the vesicles fuse to the membrane and the viruses are released
the multiple viral particles can also remain in exosomes which are encosed in multivesicular bodies that release the particles into the extracellular space without removing their exosomes; this makes it easier for them to evade the immune system the viral particles can also infect the next cell together
what methods can a virus take to transmit itself to other cells
what is an entry inhibitor?
what are nukes and non-nukes?
what are integrase inhibitors?
what are protease inhibitors?
symptoms of RSV IN CHILDREN
how rhinovirus cause infection
detail the RSV genome
what are upper respiratory tract viral infections
what are lower respiratory tract infections
covid pathogenesis
So here we have an infection of an epithelial, cell in the respiratory tract. so the virus undergoes its classic cycle, however, after the first 1 or 2 cell infections, some cytotoxic damage occurs where the cells start to sense infection and secrete some cytotoxins And those chemical, particles are gonna be sent to the neighbour cells or tissue to prepare them for the coming infection. And this gonna also attract you can see here immune cells like macrophages, neutrophil or dendritic cells.
how is infuenza named?
what are the symptoms of influenza?
influenza viral life cycle
- the first step will be the binding to your cells. The HA proteins bind to sialic acid receptors on the host cell
- 2 - then internalisation of the viral particle requires endocytosis and acidification of the endosome releases the capside and RNA genome into the cytosol
- during uncoating RNPs are released into host cytosol. RNPs transported to the nucleus where mRNA is transcribed, RNPs are transported to the nucleus by microtubules
- Viral mRNA exported out of the nucleus and translated by
host ribosomes. Viral polymerase subunits and NP proteins move to the
nucleus to form RNPs - Assembly & budding: HA, NA and M2 proteins trafficked to the cell
membrane. RNPs in the nucleus move to the cytosol then the cell membrane. Virions bud from the cell membrane
antigenic shift vs antigenic drift
Drift: Accumulation of mutations in antigens
(particularly HA, also NA))
* Occurs most frequently in Influenza A, then B
Shift: Different strains infecting the same host
cells can undergo ’reassortment’
* Occurs among influenza viruses of the same
genus. Most common in IAV (particularly avian
influenza)
what diagnostic methods are available for GE viruses?
label how all the VP proteins exist on the 3 capsid layers of a rotavirus
what is unique about when rotaviruses enter a host cell?
rotaviruses keep their internal capsids in the cytosol of the cell. These capsids have holes, as you can see here in this cartoon for VP2. And these holes allow the messenger RNA to be released into the cytosol because those messenger RNA need to be transformed into protein by cellular ribosomes.
what is the pathology of rotavirus?
- Virus infects the tips if the microvilli in the intestine
- Massive change in the host ability to reabsorb water. lots of water is lost, as it cannot be reabsorbed
- Most effective treatment is re-hydration (avoid de-hydration
what are the reasons for high rotavirus transmission
why do Norovirus have the VPg protein on the 5’ end of their RNA?
the VPg protein is recognised by host ribosomes and initiates translation to form proteins
