Parasites

Question 1

What protects someone against P. falciparum malaria?

Answer 1

HbS and HbC in both the heterozygous and homozygous state

Question 2

If you lack the Duffy RBC antigen, which plasmodium are you resistant to?

Answer 2

Plasmodium vivax - most people in central Africa lack Duffy antige, P falciparum predominant form

Question 3

Plasmodium life cycle:

Mosquitoes inject what into humans that travel and infect the hepatocytes to complete their liver stage development?

Answer 3

Sporozite

Question 4

Plasmodium life cycle:

When the hepatocyte ruptures, what infects the RBCs?

Answer 4

Merozoite

Question 5

What do merozoites develop into?

Answer 5

Schizonts - rupture RBCs and infect other cells

Question 6

Why is P. falciparum more severe?

Answer 6

The ability of its trophozoite and schizont forms to sequester in the deep venous microvasculature

PfEMP-1 binds to CD36 and ICAM-1 (microvasculature endothelium)

May also bind CSA on placenta - selective sequestration in placental tissue

Question 7

How is leishmania spread? Where are they distributed? How does it manifest in people?

Answer 7

Sandflies; across tropical, subtropical and temperate regions; Cutaneously, visceral, mucosal

Question 8

What is the causative agent of American trypanosomiasis?
How is it spread?
What are infections due to T. cruzi referred to as?

Answer 8

1. T. cruzi
2. triatomine insects pooping infective forms in mucous or breaks in skin
3. Chagas disease - fever or swelling around the site of inoculation - usually around kid’s eye (Romana sign) 20-30% people develop debilitating medical problems - heart; esophagus, colon = difficulty eating & passing stool

Question 9

How is babesia transmittd?

Answer 9

Tick, like Borrelia burgdorferi - nonspecific symptoms

Question 10

Giardiasis

Answer 10

cause of endemic and epidemic diarrhea - waterborne outbreaks of diarrhea and occasionally foodborne outbreaks via ingestion of cysts

acute self-limited diarrhea and chronic diarrhea, malabsorption, and weight loss

Question 11

Cryptosporidiosis

Answer 11

Causes diarrhea
Second most common parasitic infection in U.S.
Transmission by ingestion of oocysts (resistant to chlorination)

Question 12

Entamoeba histolytica associated with intestinal and extratestinal infections

Answer 12

Infection from ingested cyst via fecal contaminated water
Most common manifestation is diarrhea w.o dysentery
More severe form of infection = liver abcess, right lobe of liver

Question 13

Trichomoniasis (Trichomonas vaginalis)

Answer 13

Associated with other STDs and a marker of high-risk sexual behavior
vaginal frothy discharge, odor, erythema
Can be confused wtih candidiasis and bacterial vaginosis

Question 14

Nematode (roundworm) - hookworm - Ascariasis

Answer 14

Most common helminthic infection
Live and mate in lumen of small intestine (jejunum)
Each female worm makes 200,000 ova per day - eggs pass in feces

Egg ingested, hatch in small intesting & release larvae, larvae migrate venous blood to liver, heart, lungs, tracheobronchial tree, swallowed and return to intestine where they develop into mature worms

most people with ascaris infections = asymptomatic, small proportion develop pulmonary symptoms when the larvae provoke immune mediated hypersensitivity response

entanglement of worms near ileocecal valve = spasmodic contraction, obstruction, perforation, intussussception, volvulus, death

Question 15

Whipworm infection (Trichuris trichiura)

Answer 15

Transmitted through soil, 3rd most common
eggs shed in stool, undergo maturation, ingestion of egg -> hatching in GI tract and maturation to adult worm
Heavy infection in distal portion of colon - rectal prolapse

Question 16

Hookworm (nematode/roundworm) (Ancylostoma duodenale and Necator americanus)

Answer 16

soil-transmitted (human feces used as fertilizer, defecation into soil), one of the most common roundworms

Eggs passed in stool and hatch, rhabditiform larvae grow in feces and mature (infective) ->penetrate foot -> carried through blood vessels to the heart -> to lungs -> ascend bronchial tree to pharynx where swallowed -> small intestine where mature into adults

Question 17

Enterobiasis (enterobiasis vermicularis) human pinworm

Answer 17

most common worm infection in US
Person infected by ingesting pinworm eggs directly or indirectly
Eggs deposited around anus by the worm - adult female worm migrates to colon and lays eggs around the anus
Common clinical manifestation - itchy anal region

Question 18

Intestinal Cestodes
What is their morphology?
How is it acquired?
What are the three different kinds?
Tapework lifecycle?

Answer 18

1. Flat segmented worms that live in intestines of some animals
2. From eating undercooked meat
3. Taenia saginata (beef), solium (pork), latum (fish)
4. Animal infected - > eggs hatch in inestine -> migrate to striated muscle and develop into cysticerci-> in humans mature into adult tapeworm in intestine -> segments and eggs passed in feces

Question 19

What condition can the pork tapeworm cause?

Answer 19

Cysticercosis - ingested eggs hatch in the intestine, invade the intestinal wall, migrate to striated muscles and brain, liver, other tissue - where they develop into cysticerci- localize in brain = neurocysticercosis

Question 20

Diphyllobothrium latum

Answer 20

Largest tapework - 30 feet long