Parasites Flashcards
Type Clinical Pathogenesis/Life cycle
Entamoeba histolytica
T: Protozoa
C: Bloody diarrhea
Liver abscess
P/L: Cyst is excreted by someone and ingested by someone else;
Undergoes excystation and becomes a trophozite, attaches to colonic mucosa;
Can penetrate the portal circulation and cause liver abscess;
New cysts form in the gut and are shed, ready to infect another
T: Metronidazole with subsequent paromomycin or diloxanide
Acanthamoeba
T: Protozoa
C: Infection of cornea
P/L: Attach to contact lenses and infect the cornea
Naegleria fowleri
T: Protozoa
C: Meningo-encephalitis (usually fatal)
P/L: Enters the nose when someone is swimming, then enters the brain through the cribriform plate
T: No effective treatment
Giardia lamblia
T; Protozoa
C: Frothy, smelly diarrhea
Reservoir in wild animals, farm animals, pets
P/L: Ingested, then grows cysts convert to trophozoites, which multiple in the duodenum, then convert back to cysts in the colons, which are excreted into stool; tends to infect pts with IgA deficiencies
T: Metronidazole
Cryptosporidium spp.
T: Protozoa
C: Prolonged diarrhea
Reservoir mostly in farm animals but also pets
PAcquired by ingestion, then oocytes develop into sporozites in the intestine which attach and invade enterocytes; develop into trophozites causing diarrhea, has worse effects in immunocompromised
T: Good hygiene, water treatment;
Nitazoxanide; restore immune function in immunocompromised
Microsporidia
T: Protozoa
C: Diarrhea, mainly affects immunosuppressed people with HIV
T: Albendazole, restoration of immune function via anti-HIV meds
Trichomonas vaginialis
T: Protozoa
C: Frothy vaginal discharge with fish-like odor;
Vulvovaginal soreness/irritation;
Most men are asymptomatic
P/L: Passed from female to male to female via sex; no vector needed for transmission
T: Metronidazole
Plasmodium spp.
T: Protozoa
C: Uncomplicated malaria - cyclic fever (cold stage, hot stage, sweating stage)
Severe malaria - microvascular disease, hypoglycemia, cerebral malaria, renal failure, pulmonary edema, anemia, multiorgan failure, coma
P/L: Mosquito vector (P. falciparum in tropical regions, P. vivax, ovale in more temperate zones); sporozoites (mosquito) → schizonts (liver) → merozoites (RBCs) → ring form → trophozoite → schizont → merozoite; merozoites lyse RBCs to escape and infect more red blood cells; sexual stage in mosquitoes
T: Chloroquine, quinine, primaquine, artemisinin derivatives, mefloquine, malarone
Virulence - PfEMP expression leads to endovascular binding
Babesia
T: Protozoa
C: Typically asymptomatic, can have mild fevers and diarrhea;
Prevalent in Martha’s Vineyard/ Cape Cod area
P/L: Tick vector; infects RBCs forming “Maltezer cross”; part of life cycle occurs in deer/mice
T: Clindamycin and quinine or atovaquone and azithromycin
Leishmania spp.
T: Protozoa
C: Cutaneous - skin ulcers
Mucocutaneous - ulcers/lesions of mucous membranes
Visceral - hepatosplenomegaly, fevers
P/L: Infect macrophages in humans; sandfly is the vector; prevalent in Central/South America, the Middle East, and Africa
Trypanosoma spp.
African- Brucei
American - cruzi
T: Protozoa
C: African - chancre at site of infection, systemic spread with lymphadenopathy, fever, anemia, transient edema, rash; can lead to CNS involvement - often fatal meningoencephalitis
American - Chagas disease - esophageal and colon dysmotility, cardiomyopathy
P/L: African - trypomastigote lives in blood of mammalian host, part of life cycle takes place in tsetse fly (vector); reservoir in cattle; has variation of variable surface glycoprotein (VSG) to evade host antibodies (antigenic shift);
American - kissing bug vector, S. America, no antigenic variation of surface proteins, intracellular
T: Treatment depends on clinical stage, parasite, and side effects
Toxoplasma gondii
T: Protozoa
C: Eye infections (retinitis);
Encephalitis in immunocompromised
Can be perinatally transmitted, causes ocular and CNS symptoms in baby, not always apparent at first
P/L: Transmitted from cat feces or uncooked meat; infectious sporozoites penetrate intestine wall, infect macrophages, become tachyzoites, then disseminate to brain or CNS, forms cyst; can become dormant, then reactivates in the immunocompromised, leading to encephalitis; opportunistic infection
T: Prevention - pregnant women shouldn’t change cat box
Drugs available for treatment
Intestinal roundworms (5 kinds)
T: Helminths
C: Perianal itch (pinworm); Disseminated infx (Strongyloides); Non-specific abdominal discomfort or anemia (Ascaris, Trichuris)
P/L: Female worms in the gut produce eggs, which embryonate and infect other humans via ingestion (Ascaris, Enterobius, whipworm) or penetration of the skin by larvae (hookworm, Strongyloides)
T: Albendazole/mebendazole or ivermectin;
Pyrantel for E. vermicularis
nchocerca, Wuchereria, Brugia
T: Helminths
(Tissue nematodes)
Clinical: Filariasis
O - river blindness
W - elephantiasis
B - elephantiasis
P/L Transmitted by mosquitoes; larvae pass into lymphatics where they mature; destroy lymphatics causing edema; fertilized females then discharge microfilariae into the blood
Trichinella
T: Helminth
(Tissue nematode)
C: Diffuse myalgias, facial edema, fevers
P/L: Ingestion of raw/undercooked contaminated meat, larvae migrate through intestinal mucosa, mature, and new larvae go into muscles
