Immunology - week 3 parasites 2 Flashcards
What organism causes Entameoba histolytica?
Amebiasis
How is Amebiasis transmitted?
Ingestive - direct fecal/oral - anal sex
How can you tell the difference between trophozoites in an invasive disease of Amebiasis and cysts in a non-invasive case of Amebiasis?
Trophozoites: Diarrheal stool Cysts: formed stool
What is the life cycle of Entameoba histolytica?
1) Infective acid-resistant cysts ingested, excystation in colon 2) Trophozoites attach to colonic mucin and divide 3) Resistant cysts form in colon and shed in feces 4) Trophozoites can penetrate the mucosal layer which leads to invasive disease
What is the pathology of Amebiasis? (3)
1) Carriers: Chronic for months or years - shed millions of cysts per day
2) Dysentary: Severe bloody diarrhae - invade colonic epithelium and submucosal ulcers
3) Invasive: Rare - dissemination throughout body but mostly liver (not always associated with diarrhea)
How do you diagnosis Amebiasis? (2)
1) cysts in stool or trophozoites in bloody diarrhea 2) travel history is essential (amebiasis often picked up in developing countries)
How is Giardia transmitted?
Ingesitive: fecal/oral from animals also from anal sex ex. animal poops in stream and you drink water and get it
What is the lifecycle of Giardia?
1) injest cysts - trophozoites excyst in upper small intestine 2) encystation in colon 3) excrete cysts in stool (trophozoites are very unstable outside body)
What’s the pathology of Giardia?
Onset of 2 weeks, asympotomatic to “explosive” diarrhea Most people don’t need treatment
What are the apicomplexan parasites of humans? (4)
cryptosporidium
Toxoplasma
plasmodium
Babesia
What are common characteristics with Apicomplexan Parasites?
Obligate intracellular parasites (must invade to live)
How are Cryptosporidiosis transmitted?
Fecal oral transmission
Where does Cryptosoporidiosis reside in the body?
Intestine
What is unique regarding the lifecycle of Cryptosporidium? Why is this important?
Extra-cytoplasmic - developmental cycle in brush boarder Important: difficult to treat - aids/immune compromised patients particularly vulnerable
What is the pathology of Cryptosporidiosis? (3)
1) 3 or more loose watery bowl movements per 24 hours 2) Symptoms similar to giardia but more diahhrae and fluid loss 3) Healthy people have an immune response to clear parasite
How is Cryptosporidiosis diagnosed?
2-5 mm cysts in stool - red cup and saucer shaped
What is the definitive host for Toxoplasmosis?
Cats
How is Toxoplasmosis transmitted?
Ingestive: fecal/oral and undercooked meat (can be in any warm blooded animal) Transplacental: congenital infection (which is why it’s so important for pregnant woman)
What is the lifecycle of toxoplasmas?
1) Oocytes shed by cats - can last for a while in environment 2) ingested by warm blooded animal where it goes through sexual reproduction 3) Goes into muscle or neuronal tissue: cysts form 4) animal gets eaten
When should a pregnant woman not be worried about Taxoplasmosis?
If a pregnant woman has already been exposed to it then they will have developed an immune response and will be immune to a secondary infection
Why is Toxoplasma dangerious for pregnant women?
Toxoplasma easily crosses the placenta and grows well in the brain tissue of the fetus causing lots of problems (usually abortion)
How is Toxoplasmosis diagnosed?
1) serology - use an indirect immunofluoresence (IFA) 2) confusion or seizure
What is a ring enhancing lesion?
areas of edema where cysts in brain have started to grow again
How can you tell if a ring enhancing lesion is caused by cancer or taxoplasma?
If taxoplasma there will be more than 1
What does it mean if your serology revealed the following: Positive for Toxo-specific IgG? Positive for Toxo specific IgM? High IgG avidity? Low IgG avidity? Positive for IgG but not IgM?
Positive for Toxo-specific IgG: infected at some point with Toxoplasmosis Positive for Toxo specific IgM: infected within past 2 years High IgG avidity: infected 12 weeks or more prior Low IgG avidity: possibly a recent infection Positive for IgG but not IgM: chronic infection - infected for greater than six months
Why is gardening a risk for taxoplasmosis?
Because the oocyte can survive in soil and they’re hard to wash off
What does Babesiosis infect?
red blood cells
What is the definitive host of Babesiosis?
Deer tick
Who is the intermediate host for Babesia?
mice and small mammals
Who is the accidental host for Babesia?
humans
What is the lifestyle of Babesia?
1) tick introduces babesia into rbc of mouse - babesia forms gamates
2) tick then takes the gamates in second tic bite for same host - sexual reproduction of gamates takes place
3) make oocyst that goes into salivary glands of tic
4) tick bites another host - transmitted via saliva
How is Babesia transmitted? (2)
1) via nymph stage of deer tick 2) blood transfusion
What is the pathology of Babesiosis?
Usually nothing - some hemolytic anemia and nonspecific flu like symptoms
How can you diagnose Babesiosis vs. Malaria?
Babesiosis: In rbc: babesia has cross shaped structure called “maltase cross” plasmodium: In rbc but doesn’t have maltase cross
What causes Malaria?
Plasmodium (various species)
Where does plasmodium infect? first? second?
first hepatocytes, then erythrocytes
What is the definitive host of plasmodium?
mosquito
What is the intermediate host of plasmodium?
humans
How is plasmodium transmitted? (3)
Vector-borne: female mosquitoes Also congenital and needle transfer
Why is it difficult or even impossible to eradicate malaria?
Because different plasmodium species have animals as their primary host
Why is plasmodium difficult to create a vaccine for?
Because the parasite periodically switches out the knob proteins it uses thus requiring a different immune response every time.
Which is the most dangerous plasmodium?
P. falciparum
What is the lifecycle of malaria?
1) Mosquito bites human - inject sporozoites from their saliva
2) sporozoites go to liver and replicate
3) merozoites go to RBCs
4) Mosquito picks up blood from infected person
5) develop in mosquito into sporozoites
What is the mechanism that causes cerebral malaria?
In RBC the Merozoites make knob proteins on surface of RBC making them bumpy and adherent to capillaries. The immune system attacks these RBC’s on the surface of capillaries including the ones in the brain. This breaks down the BBB and allows the parasite access to the brain.
What causes the majority of symptoms in malaria?
over active immune response that react to the knob proteins on RBC’s created by the merozoites
Where do vaccines attach that are currently available for malaria? Why is that ineffective?
Vaccines that attack the sporozoites are ineffective because the sporozoites quickly migrate to the liver to differentiate into merozoites who go into RBC’s
Why would shortening the lifespan of a mosquito mitigate the spread of malaria?
Malaria needs a certain amount of time to develop in the mosquito before it can be spread to humans - shortening the lifespan of mosquitos would prevent the malaria from having that time to develop
What are the human malaria species? What are their geographic distributions?
P. falciparum: Africa, Western pacific, SE and S asia P.
vivax: Asia and South America mostly, some in SE asia P.
ovale: 8% in parts of Africa P. malariae: 2-3% in africa P.
knowiesi: 70% in some areas of SE asia
Which species of malaria does not relapse from the liver?
P. faciparum - because it is too virulent
What is the pathology of malaria? What causes this?
You get spikes of fever followed by chills - caused by synchronous division in RBC so they lyse at the same time
What are the symptoms of cerebral malaria?
unarousable coma not attributable to other causes usually seen in children over 2 years
What symptoms are more common for children under 2 years old? less common?
More common: anemia
Less common: cerebral malaria (because they don’t really have an immune system yet)
What is respiratory distress syndrome?
Injury to lung micro-vascular endothelium and alveolar epithelium because of an overactive immune response to malaria
What causes Anemia in malaria patients?
lysing of rbc
How do you diagnose malaria?
Microscopic tests: P. falciparum have multiple rings per RBC
