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Flashcards in Parasites Deck (40):

Intermediate host vs definitive host

Intermediate = larval/asexual

Definitive = adult/sexual


Cause of dysentery-like illness or liver abscesses, see inverted flask shaped lesions in large intestine, cysts are transmitted via fecal-oral route, diagnose by cysts in stool

Entamoeba histolytica


Attaches to duodenal wall and causes malabsorption leading to steatorrhea, cysts transmitted via fecal oral route, falling leaf motility, fecal antigen test has replaced string test

Giardia lamblia


Most common parasitic cause of persistent watery diarrhea in AIDS patients, cysts transmitted in undercooked meat, acid fast round oocysts seen in stool

Cryptosporidium parvum


Persistent watery diarrhea in AIDS patients, causes steatorrhea via malabsorption, fecal oral transmission, acid fast elliptical oocysts seen in stool

Isospora belli


Trophozoite transmitted sexually, corkscrew motility, frothy vaginal discharge with fish like odor and strawberry cervix, treated with metronidazole

Trichomonas vaginalis


Associated with swimming in fresh water, primary amebic meningoencephalitis leads to severe prefrontal headache and altered sense of smell, rapid onset and fatal



Associated with contact lens solution, causes keratitis or granulomatous amebic encephalitis, slow onset but encephalitis progresses to death



In malaria, fever spikes are due to what?

Erythrocytic schizont rupture


Which two forms species of Plasmodium tend to relapse and why? What treatment consideration is needed?

Vivax and ovale tend to relapse due to tendency to remain in liver as hypnozoites. Primaquine is added to drug regimen which addresses liver stage.


Irregular fever spikes with multiple ring forms and crescent shaped gametes, resistant to chloroquine

Plasmodium falciparum


Plasmodium associated with 72 hr fever spikes and band forms



Diagnosis of any form of Leishmaniasis?

Look for amastigotes in macrophages


Initially presents as swelling around the eye (Romana sign), usually in children, disease caused by inflammatory response to trypomastigotes and leads to cardiac, liver, brain, and colon involvement

Chagas disease - Trypanosoma cruzi with the Reduviid bug vector


Cause of African Sleeping Sickness, causing a hemolymphatic disease with fever, chills, and anorexia. Diagnose with trypomastigotes in blood film. What is the hemoflagellate and vector?

Trypanosoma brucei gambiense (West) or T. brucei rhodesiense (East)

Tsetse fly vector


3 variations of Leishmaniasis and their vector?

1) Visceral (L. donovani) - Kal Azar and hepatosplenomegaly

2) Cutaneous - ulcerating sore

3) Mucocutaneous (braziliensis) - most severe and disfiguring

All transmitted by sandfly bite, treat all with stibogluconate


Malaria-like illness transmitted by Ixodes tick, can be co-infection with Borrelia (but no response to doxycycline), maltese cross on Giemsa strain



What are risks to the fetus of a primary Toxoplasmosis infection in utero?

- if early in pregnancy, congenital infection is severe and can see hydrocephaly and intracerebral calcifications

- if late in pregnancy, infection may be inapparent but leads to progressive blindness later in teen years


What disease does Toxoplasmosis cause in AIDS patients?

leading cause of focal CNS disease with ring enhancing lesions


First intermediate hosts of trematodes (flukes)



Trematode that is associated with intestinal disease, is acquired by penetrating intact skin (often associated with rice field workers, as they are in standing water for extended periods), causes itching and granulomas in liver, egg has subterminal spine

Schistosomiasis mansoni

(S. japonicum is also presents the same, but egg has no subterminal spine)


Trematode that is associated with bladder disease, penetrates intact skin and matures in bladder veins, egg has a terminal spine. Chronic infection, as would be seen in Egypt or Africa, increases risk of bladder squamous cell carcinoma

Schistosomiasis haematobium


Trematode associated with intensely itchy dermatitis and self resolves, eggs are operculated

Non-human schistosomes - usual host is birds and cannot survive long in human


Ingestion of rare beef or pork leading to an intestinal tapeworm. Can lead to cysticerosis and inflammation, including adult onset epilepsy.

Taenia saginata (beef tapeworm) or T. solium (pork tapeworm)


Intestinal tapeworm associated with eating fish and developing a Vitamin B12 deficiency and subsequent megaloblastic anemia

Diphyllobothrium latum


Tapeworm associated with sheep raising areas and hydatid cyst disease. Treat with surgical removal and be careful not to break the cyst - it will cause anaphylactic shock!

Echinococcus granulosus


Associated with alveolar hydatid cyst disease - cysts are very aggressive and bud off frequently, making treatment difficult

Echinococcus multilocularis


Pinworm - perianal itching, eggs transmitted person to person or back to self, diagnose with scotch tape test

Enterobius vermicularis


Whipworm - associated with appendicitis or rectal prolapse, eggs are ingested and barrel shaped with bipolar plugs

Trichuris trichiura


Largest roundworm - Bile stained knobby eggs that cause pneumonitis and may obstruct intestine

Ascaris lumbricoides


Visceral Larva Migrans - larvae are confused by different host, wander around aimlessly until they die and cause inflammation, caused by handling pets

Toxocara canis or cati


Most frequent helminth parasite in US vs worldwide?

US - Enterobius vermicularis (pinworm)

Worldwide - Ascaris lumbricoides


Hookworm - New world, associated with pneumonitis and anemia, larva penetrates intact skin of bare feet

Necator americanus


Cutaneous Larva Migrans - intense itching, tunnels through skin, can't mature in humans

Ancylostoma braziliense or caninum (dog and cat hookworms)


Threadworm - can cause chronic disease due to autoinfection, pneumonitis and diarrhea eventually lead to malabsorption and ulcers

Strongyloides stercoralis


Associated with hunting bear and presents as fever, myalgias, splinter hemorrhages, and eosinophilia

Trichinella spiralis


Mosquito vector causing elephantiasis

Wucheria bancrofti


Mango fly vector causing itching and swelling in eye - does not progress to blindness

Loa loa


Black fly vector causing itchy leopard rash, nodules, and progresses to blindness

Onchocerca volvulus


Guinea worm that erupts from skin and needs very slow removal to avoid breaking it and inducing anaphylaxis

Dracunculus medinensis