Parasites V

Question 1

Pneumocystis jivoveci: how is it spread? who is susceptible? what is a potential reservoir? What are some scientific challenges?

Answer 1

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

Question 2

How do you diagnose pneumocystis?

Answer 2

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

Question 3

How does pneumocystis kill patients?

Answer 3

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)

Question 4

How do you treat pneumocystis? Any considerations?

Answer 4

-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

Question 5

cryptosporidium: diagosis

Answer 5

diarrhea, weight loss, acid fast stain of fecal specimen.

Question 6

What disease is caused by cryptosporidium?

Answer 6

watery diarrhea

Question 7

How is cryptosporidium transmitted?

Answer 7

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

Question 8

What happens when people with normal immune systems ingest cryptosporidium?

Answer 8

watery diarrheal disease

but, it is self-limiting in immunocompetent host

Question 9

What is the lifecycle of cryptosporidum?

Answer 9

1. oocyst
2. excystation
3. sporozoite attaches to brush border and matures to merozoite
4. schizogony with more merozoite formation
5. some merozoites become sexual stages
6. gametes fuse to form oocyst. most exit, but some persist in body –> this is a big problem for the immunocompromised

Question 10

When can a kid with cryptosporidium go back to school/day care

Answer 10

after symptoms have passed

Question 11

How do you treat cryptosporidium? Patient considerations?

How do you prevent infection?

Answer 11

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.

Question 12

What is cyclospora? Where is it relevant? How is it different from cryptosporidium?

Answer 12

cyclospora: emerging pathogen in AIDS patients
2X the size of cryptosporidium
both are acid fast

Question 13

Microsporidia: what are they? For whom is it relevant?

Answer 13

obligate intracellular spore0forming protozoa
induce diarrhea
important in AIDS pts

Question 14

How do you diagnose toxoplasma gondii?

Answer 14

usually based on serology and/or history (esp. history of HIV infection). INCREASES in titer are diagnostic

Question 15

What are the three forms of toxoplasmosis diseases caused by toxoplasma gondii?

Answer 15

1. febrile lymphadenopathy, swollen, enflammed nodes. least common, least severe.
2. reactivation of lethal infection that forms brain lesions in the immunocompromised. often lethal
3. congenital infection

Question 16

How do you treat toxoplasmosis gondii?

Answer 16

Bactrim; pyrimethamine-sulfadiazine (though this may be contraindicated during pregnancy)

Question 17

What is the toxoplasmosis gondii lifecycle?

Answer 17

1. pseudocysts exist in the mouse
2. cat eats mouse
3. T. gondii undergoes sexual replication in cat
4. oocytes pass into feces and are inhaled by person, OR person eats undercooked infected animal
5. tachyzoites infect liver cells
6. infected macrophages introducte tachyzoites throughout the body
7. organism undergoes asexual cycle; pseudocysts are produced.

Question 18

What problems can result from toxoplasmosis gondii infection?

Answer 18

brain lesions (when pseudocysts are reactivated), chorioretinitis, hepatitis, lymphadenitis

Question 19

Why must pregnant women avoid toxoplasmosis gondii infection?

Answer 19

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

Question 20

What is strongyloidiasis?

Answer 20

parasite (nematode) infection
usually asymptomatic except in immunocompromised host, in which case auto-infection may be fatal
exposure may have been decades earlier

Question 21

What is the strongyloides lifecycle?

Answer 21

can go through entire lifecycle inside of humans. So, auto-infection is a big issue!

1. larvae penetrate skin
2. larvae migrate to lungs
3. larvae penetrate alveoli
4. larvae are swallowed
5. larvae develop in the small intestine and adult worms live embedded in intestinal epithelia
6. 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

Question 22

How do you diagnose strongyloides?

Answer 22

larvae in the stool or sputum (severe cases)

Question 23

What are some symptoms of strongyloides?

Answer 23

abdominal pain, diarrhea, and mucus passage. eosinophilia. accumulation of larvae in lungs and adults in the intestine of immunocompromised patients

Question 24

What are two drugs that can be used to treat stongyloides?

Answer 24

ivermectin and albendazole. disrupt organism microtubules