Parasites Flashcards
________ infections are among the most prevalent diseases in developing countries.
Parasitic
What is the difference between a parasitic infection and parasitic disease?
Infections are prevalent, but are not prolonged. Diseases are a consequence of prolonged, repeated, or high burden infection
Parasitic diseases are rarely fatal except for _______ which may be rapidly fatal (within 3-5 days).
Malaria
What are the two parasite types?
Protozoa and helminths
Many parasitic infections are ________ which could indicate why they are more prevalent in underdeveloped countries.
Zoonoses
Protozoa are _____-_______ __________.
One-celled eukaryotes
A ________ inoculum is required for initiation of protozoan infection.
Small
*parasitic replication to high numbers; intracellular; no free environmental stage in life cycle
Protozoa are often transmitted by which route?
fecal-oral (extracellular = lumen of GI)
What are the two forms within the protozoan life cycle?
Active Trophozoite Dormant Cyst (withstands environmental desiccation)
How do Mastigophora move?
Flagella
How do Mastigophora reproduce and divide?
Reproduce: sexual = syngamy
Divide: Longitudinal Fission
Parasitic forms of Mastigophora tend to lack ______ and _______.
Mitochondria
Golgi Apparatus
True or False: Most Mastigophora are solitary.
True
What are four examples of Mastigophora? Give one example of how one of these caused an outbreak of illness in the US.
- Trypanosoma
- Leishmania
- Giardia and Cryptosporidium*
- Trichomonas
*Cryptosporidium: drinking water outbreak in Milwaukee, 1993
Most Apicomplexa are ________, except male gametes.
Non-motile
What do Apicomplexa produce through sexual reproduction?
sporozoites
Apicomplexa are also known as what?
Sporozoa
What are two examples of Apicomplexa?
Plasmodium
Toxoplasma gondii
Helminths are ___________ ___________, also known as _________.
Multicellular animals
Metazoa
What three characteristics allow Helminths to be extracellular parasites?
- Large size
- Protective cuticle
- Larvae can develop into dormant cysts
Describe the complex life cycle of helminths.
- They exist in animal and human reservoirs
- They do NOT typically complete their life cycle within a human host
- Developmental stages take place outside of human, in insect vectors, or in animal reservoirs.
- Reproduce sexually; some are hermaphroditic
What kind of hosts are humans for Helminths?
Definitive Hosts
What kind of hosts are animals for Helminths?
Intermediate Hosts
Most Helminths cause _________ infections that are tolerated by the human host.
Chronic
True or False: Disease caused by Helminths is a consequence of parasitic replication.
False: Disease is NOT a consequence of REPLICATION. Rather, it is parasitic burden due to the number of parasites initially acquired from the environment.
Helminth infections spontaneously resolve when adult worms reach ___________. They are not eliminated by host response.
Senescence
True or False: Adult Helminths are large enough to be seen with the naked eye, but eggs/larvae must be identified with a microscope.
True
What are the two major groups of Helminths?
Flatworms
Roundworms
What is the common name for cestodes?
Tapeworms (a type of flatworm/platyhelminthes)
What is a common name for Trematodes?
Flukes (a type of flatworm/platyhelminthes)
Nematodes, from the phylum Aschelminthes, are also known as _____________.
Roundworms
Name one difference between flatworms and roundworms in relation to their visible characteristics.
Flatworms are segmented, round worms are not.
Most parasite vectors are _______________.
Arthropods
What is the vector for Malaria?
Female Anopheles mosquito
What is the vector for Sleeping Sickness?
Tsetse Flies
What is the vector for River Blindness?
Black Flies
What is the vector for Chagas’ Disease?
“Kissing” bugs
What is the vector for babesiosis?
Ticks
What are two local conditions that favor arthropod breeding and therefore parasitic prevalence?
- Stagnant water, foliage
2. Suitable animal hosts
What are parasite reservoirs?
Sources of parasites that do not DIRECTLY participate in transmission.
Name the three means for parasite entry.
- Oral (contaminated food/water)
- Skin penetration
- Bite Wounds/Arthropod-borne (blood transfusion)
For disease manifestation, Amoebiasis needs a _______ inoculum size.
Large
For disease manifestation, Cryptosporidiosis needs a ______ inoculum size.
Small
How do parasites evade host antibody and cell-mediated immune responses?
- Surface antigen variation (trypanosomes)
- Host Plasma Protein Coat (blood flukes)
- Secretion of Superoxide Dismutase to prevent host phagolysis.
What is the tissue tropism for Hookworms?
Intestinal Lumen
Which antigen on RBC surface is required for entry of P.vivax malaria parasites? Who often lacks this antigen and is, therefore, resistant to Malaria?
Duffy Factor Antigen
Those of Black/African Descent
Parasitic spread and multiplication are dependent upon what two external factors?
- Tissue/species Tropism
2. Temperature
Damage from parasites may be due to what two means?
- Direct tissue damage by parasite (cytolysis = ulcers)
2. Effects of immune response (inflammation, hypersensitivity)
True or False: Most clinical complications occur quickly after entry.
False, most occur years after initial infection.
For which parasite is the adult form asymptomatic in the intestine, but the larvae may enter the blood to infect deep tissues (possibly causing seizures or hydrocephalus in CNS).
Pork Tapeworm
What is Chagas’ Disease?
Also known as American Trypanosomiasis, it is found commonly in Mexico, South America, and Central America. Infection most commonly occurs through interaction with the feces of a “kissing bug.” There is an acute and chronic phase.
Describe the Acute Phase of Chagas’ Disease.
Immediately following infection.
May last a few weeks or months.
Mild (swelling or fever at site) or Asymptomatic.
Romana’s Sign = swollen eyelid
Describe the indeterminate phase of Chagas’ Disease.
Following the acute phase, most infected people enter into this prolonged asymptomatic form of disease during which few or no parasites are found in the blood.
Describe the Chronic phase of Chagas’ Disease.
20 - 30% of infected people will develop debilitating and sometimes life-threatening medical problems over the course of their lives: lesions on organs (heart, esophagus, colon), heart murmurs. Damage is irreversible and sometimes fatal.
For eradication success, more than one of which three methods must be employed?
- Chemoprophylaxis- preventative drugs
- Immunization
- Field Control Measures (insecticides, sanitation)
What are three parasitic mechanisms that make immunization difficult?
- Many parasites masquerade by coating in host antigens
- Some continually alter surface antigens
- Different proteins are displayed at different life stages
What are the four RBC Parasites (Plasmodium) and how do their preferences vary?
- P. falciparum: ALL ages of red blood cells ( hi mortality)
- P. Vivax: YOUNG red blood cells & reticulocytes
- P.Ovale YOUNG red blood cells & reticulocytes
- P. malariae: OLD red blood cells
True or False: Around the world, Malaria remains a crucial controllable disease.
True.
*infection in the US is typically driven via travel
Transmission of _______ occurs 9-17 days after bite from infected female Anopheles mosquitoes and symptoms develop 8-30 days later.
Malaria
What is the difference between induced and imported Malaria?
Imported: Travelers import parasite into a non-endemic area during the incubation period
Induced: Transmission via blood transfusions/needles
Mosquito salivary glands are inhabited by which form of the plasmodium?
Sporozoites
After a mosquito bite, how and where do sporozoites travel?
Through the bloodstream.
To the liver cells where they multiply and mature.
Plasmodium sporozoites mature in liver cells and are released to blood as _____________.
Merozoites
After plasmodium merozoites are released to the blood, they invade, divide and mature into _________.
Trophozoite
What are the stages of Plasmodium spread and multiplication following a mosquito bite?
- Travel as sporozoites through blood to liver
- Multiply and mature into merozoites
- Invade RBCs, divide, and mature into trophozoites
- RBCs burst and release merozoites
Plasmodium multiply via ________ in liver and red blood cells.
Binary fission
Malaria damage is caused by lysis of RBC and release of large numbers of ___________.
Merozoites and other parasitic molecules every 48-72 hours.
How is glycophosphatidylinositol (GPI) involved in malarial damage?
GPI stimulates TNF and IL-1 from macrophages = fever, edema, anemia, shock
A single nucleotide mutation (glutamate to valine) of the beta-globin results in what disease?
Sickle Cell Anemia
Black Africans are often missing which blood group antigen?
Duffy/Glycophorin A
Chloroquine targets the parasite’s _________ where hemoglobin is degraded. By blocking detoxification of heme, the parasite dies.
Food Vacuole
P. vivax and P. ovale have __________ liver stages during which chloroquine is not effective.
Dormant
P. falciparum and P. malariae do not produce _______ _______ stages.
Dormant Liver Stages
P. ___________ has resistant strains to which chloroquine is not effective.
falciparum
_______ is endemic in the U.S. and is easily confused with P. falciparum.
Babesia
How is Babesia transmitted?
Deer Tick
Animal reservoir = white footed mouse
How is the Babesia life cycle different from Malaria?
Merozoites are injected under the skin by tick (malaria: sporozoites from mosquito), RBCs are invaded (malaria has intermediate liver stage for producing merozoites), replicate via binary fission, lyse RBC
Toxoplasma is a _______ protozoa that causes infections in humans, but rarely disease.
tissue
What are the three syndromes associated with toxoplasma infection?
- Mononucleosis-like
- Congenital infection
- Brain/heart (immunocompromised)
Toxoplasma survive in macrophages by preventing _______and ________ fusion.
Acidification and phagolysosome fusion
How are humans infected with toxoplasmosis?
Consumption of inadequate cooked meat (tissue cysts) or food contaminated with cat feces (oocysts).
For which parasite do cats harbor a sexual cycle that is similar to mosquitoes with malaria?
Toxoplasmosis
Toxoplasma can cause _________ in human women.
Miscarriage
_____ behavior changes after consumption of cat feces that results in an affected amygdala.
Rat
There is some evidence that toxoplasma infection is linked to __________ in humans.
Schizophrenia
Link associated with increased cat popularity as pets. Take with a grain of salt
What is the small protozoan parasite that is transmitted by sandflies in tropical areas?
Leishmania
What is Kala azar?
Aka: Black Fever: It is the second largest parasitic killer in the world (behind malaria). As the visceral form of leishmaniasis, parasites migrate to the liver, spleen and bone marrow
What are the symptoms of Black Fever?
Fever, weight loss, fatigue, anemia, and substantial swelling of the liver and spleen.
The “type” of leishmaniasis (cutaneous, visceral) is determined by the _______________.
Location of the macrophages that are infected.
After the vector for leishmaniasis (sand fly) infects a host with _____1____ they enter circulating macrophages and reproduce as _____2___.
1 Promastigotes,
2 Amastigotes
(the macrophage will then die and release amastigotes to infect more macrophages)
Which are flagellated, Promastigotes or Amastigotes?
Promastigotes
________-containing compounds are useful for treatment of Leishmania.
Antimony
How is Chagas’ Disease (Trypanosoma cruzi) transmitted?
Reduviid “Kissing” Bug bites and deposits feces onto skin. Scratching the area will introduce the organism into the lesion.
Chagas’ Disease displays as what kind of illness?
Mild at first, but complications arise 10-20 years later with nerve, GI, and heart damage.
Which parasite is transmitted directly via tsetse fly bites?
African Sleeping Sickness
The main reservoirs for African Sleeping Sickness are ______ in East Africa and _______ in West Africa.
East: Wild game animals
West: humans and domestic animals (cattle)
A patient presents with a fever and swollen lymph nodes and a dominant surface antigen with antigenic variation due to genetic rearrangement. Months/years later, the patient presents with infection of the CNS, brain, and Spinal Fluid. What is the parasite?
Trypanosomes (African Sleeping Sickness or Chagas)
Which intestinal/vaginal protozoa are flagellates, frequent in the US, and transmitted via water or sex?
Giardia Lamblia
Trichomonas Vaginalis
Which intestinal/vaginal protozoa are non-motile, reproduce via alternating sexual/asexual cycles, and are foodborne?
Cryptosporidium
Cyclospora
Isospora
Cysts from Giardiasis are _________ by stomach acid to transform into ________ ___________.
Stimulated
Vegetative trophozoites
Which parasite is a common cause of vaginitis?
Trichomonas vaginalis
Which intestinal parasite destroyed host tissue in the colon, forms flask-shaped ulcers, and can spread through the bloodstream to cause abscesses in the liver and brain?
Entamoeba histolytica
Humans are ______-______ hosts for some parasites because the parasite developmental life cycle cannot be completed following infection.
Dead-End
Amoebiasis is transmitted through which route?
Fecal-Oral (highly resistant cyst)
Entamoeba histolytica adheres to host cell receptors containing _________residues via lectin surface protein.
digalactose
Damage from Entamoeba histolytica occurs after they attach and form _________.
Amoebapores
Entamoebas produce ______ _________ that digests IgA, IgG, and other proteins.
Cysteine Protease
What a parasitic example of zoonosis that can be spread person to person in crowded urban environments?
Cryptosporidium
What is a symptom of cryptosporidium?
Diarrhea that lasts about 2 weeks while the parasite remains within microvilli of the small intestines.
What is the most frequent intestinal helminth, seen commonly in the Southern US?
Ascaris
What is the lifecycle of Ascaris?
- Eggs mature in the environment for several weeks before reaching infective stage
- Eggs are ingested
- Eggs hatch within small intestine and release larvae that penetrate the mucosa
- Travel to lung, trachea/pharynx, mature in the GI tract and release eggs in stool
Nematodes (pinworms) are common in _______areas.
Tropical
True or False: Enterobius eggs require a maturation stage outside the body.
False: they do not require a maturation stage outside of the body.
Perianal itching is associated with which parasites?
Helminths/Pinworms.
Females migrate out of the anus and deposit eggs, causes itchiness, eggs transferred via fingers
What characteristics of Hookworms make them unique?
They do not require ingestion, can be transmitted through fecal-cutaneous route.
Penetrate skin as Filariform larvae
________ is less likely in persons infected by hookworms.
Asthma
About _____species of parasitic worms infect humans and yearly worldwide infections are in the _______.
50
billions
How can intestinal helminths cause chronic anemia?
Hookworms hang onto intestinal mucosa with teeth, secrete anticoagulant, and suck host’s blood. Severity is proportional to load.
Which helminth causes malfunction by perforating intestinal walls and producing septicemia?
Strongyloides stercoralis
Helminths that are long and ribbonlike with rectangular segments and sucking discs are known as?
Tapeworms
Tapeworms attach to intestinal walls via a head with sucking discs or grooves, known as what?
Scolex
Tapeworms are _____-______ and can penetrate deep tissues to form infective cystic larvae.
Non-fecal
What are the definitive and intermediate hosts for tapeworms?
Definitive: Humans
Intermediate: Animals
Deep tissue infections from tapeworms can cause what forms of severe disease?
Cysticercosis (from infected pork)
Echinococcosis (carnivore feces)
Cysts calcify, but tissue and blood helminths can _______ later in life because ______can be viable for 30 years.
re-emerge
worms
With what food source is trichonellosis most commonly associated?
Pork, deer or bear meat.
_______ are skin acquired helminths, also known as blood flukes.
Schistosomes
Schistosomiasis symptoms depend on ________ and type of ________ released.
Location of adult worms,
eggs
Snails are the ______ in schistosomes.
Vector (or intermediate host)
In which parasitic infection to the male and female move in pairs to the intestines or bladder where they sexually reproduce and release eggs?
Schistomiasis
Schistosoma ____________of people in infected water.
burrow through the skin
Humans lack effective immune responses to worms that can reside for decades due to camouflage with host proteins (serum albumin and HLA antigens) for which skin acquired helminth?
Schistosomiasis
Filariasis is transmitted by arthropods and adult filarial worms live in _______of humans or lymphatics.
Subcutaneous
What are the two forms of filariasis?
Onchocerciasis (River Blindness): via black flies
-through subcutatneous tissue
Lymphatic Filariasis (elephantiasis): via mosquitoes
-through lymphatics
Name the five intracellular protozoa:
- Malaria
- Babesia
- Toxoplasma
- Trypanosomes
- Leishmania
Name the five extracellular protozoa:
- Cytosporidia
- Giarda
- Entamooba
- Trichomonas
- Cyclosporin
Name the two round helminths:
Pinworm
Hookworm
Name the two flat helminths:
Flukes
Tapeworm
Name the two flukes:
Schistosomes
Pork tapeworm
What is a reservoir and on what factors does it depend?
The entity that holds the parasite (long-term host)
Population and Environment
What is a vector?
The organism involved directly in transmission of the parasite from one to another
What are the three types of hosts?
Intermediate
Dead-End
Definitive
