Parasites V Flashcards
Pneumocystis jivoveci: how is it spread? who is susceptible? what is a potential reservoir? What are some scientific challenges?
spread via aerosol- very ubiquitous. natural environment or person-to-person
immunocompromised ppl, especially those with HIV, are susceptible
kids may be the human reservoir
pneumocystis can’t be cultured in vitro
causes pulmonary infections
How do you diagnose pneumocystis?
need lung material- sputum won’t cut it.
we use broncho-pulmonary lavage at the bedside
diagnosis in 2-3 hrs
very traumatic for peds pts
How does pneumocystis kill patients?
primarily by progressive asphyxia- alveolar space is filled with organisms and exudate
precipitous decline also suggests that host inflammatory pathways may also play role- putting these pts on a respirator dramatically increases mortality rates (and higher O2 levels can cause inflammation)
How do you treat pneumocystis? Any considerations?
-no immunotherapy
-trimethoprim-sulfamethoxazole (Bactrim)- works well for leukemia pts but less well for AIDS pts.
Treat prophylactically for pts with CD4 counts below 200 cells/ml
-antifungals don’t work well because they target ergosterol, and pneumocystis uses cholesterol.
-corticosteroids may help reduce damage due to inflammation
cryptosporidium: diagosis
diarrhea, weight loss, acid fast stain of fecal specimen.
What disease is caused by cryptosporidium?
watery diarrhea
How is cryptosporidium transmitted?
oral-fecal route- oocysts present in feces of domestic and wild animals or persons. autoinfection also a problem. oocyte remains infectious for a long time. disease appears 3-12 days post-infection
resistant to chlorination
What happens when people with normal immune systems ingest cryptosporidium?
watery diarrheal disease
but, it is self-limiting in immunocompetent host
What is the lifecycle of cryptosporidum?
- oocyst
- excystation
- sporozoite attaches to brush border and matures to merozoite
- schizogony with more merozoite formation
- some merozoites become sexual stages
- gametes fuse to form oocyst. most exit, but some persist in body –> this is a big problem for the immunocompromised
When can a kid with cryptosporidium go back to school/day care
after symptoms have passed
How do you treat cryptosporidium? Patient considerations?
How do you prevent infection?
treat: nitazoxanide
however, nitazoxanide doesn’t work well in immunocompromised pts.
therapy is mostly supportive.
for HIV/AIDS, HAART is very important for prevention. Generally, hand washing is also critical.
What is cyclospora? Where is it relevant? How is it different from cryptosporidium?
cyclospora: emerging pathogen in AIDS patients
2X the size of cryptosporidium
both are acid fast
Microsporidia: what are they? For whom is it relevant?
obligate intracellular spore0forming protozoa
induce diarrhea
important in AIDS pts
How do you diagnose toxoplasma gondii?
usually based on serology and/or history (esp. history of HIV infection). INCREASES in titer are diagnostic
What are the three forms of toxoplasmosis diseases caused by toxoplasma gondii?
- febrile lymphadenopathy, swollen, enflammed nodes. least common, least severe.
- reactivation of lethal infection that forms brain lesions in the immunocompromised. often lethal
- congenital infection
How do you treat toxoplasmosis gondii?
Bactrim; pyrimethamine-sulfadiazine (though this may be contraindicated during pregnancy)
What is the toxoplasmosis gondii lifecycle?
- pseudocysts exist in the mouse
- cat eats mouse
- T. gondii undergoes sexual replication in cat
- oocytes pass into feces and are inhaled by person, OR person eats undercooked infected animal
- tachyzoites infect liver cells
- infected macrophages introducte tachyzoites throughout the body
- organism undergoes asexual cycle; pseudocysts are produced.
What problems can result from toxoplasmosis gondii infection?
brain lesions (when pseudocysts are reactivated), chorioretinitis, hepatitis, lymphadenitis
Why must pregnant women avoid toxoplasmosis gondii infection?
generally not a problem for a serologically pos mom, but rather a prob for the mom that converts during pregnancy. problems can include spontaneous abortion, still birth, and many pathologies including hydrocephaly
What is strongyloidiasis?
parasite (nematode) infection
usually asymptomatic except in immunocompromised host, in which case auto-infection may be fatal
exposure may have been decades earlier
What is the strongyloides lifecycle?
can go through entire lifecycle inside of humans. So, auto-infection is a big issue!
- larvae penetrate skin
- larvae migrate to lungs
- larvae penetrate alveoli
- larvae are swallowed
- larvae develop in the small intestine and adult worms live embedded in intestinal epithelia
- larvae are produced. they can either autoinfect and penetrate the bloodstream to restart the cycle, or pass in the feces, where they can be transmitted to the soil
How do you diagnose strongyloides?
larvae in the stool or sputum (severe cases)
What are some symptoms of strongyloides?
abdominal pain, diarrhea, and mucus passage. eosinophilia. accumulation of larvae in lungs and adults in the intestine of immunocompromised patients
What are two drugs that can be used to treat stongyloides?
ivermectin and albendazole. disrupt organism microtubules
