Parasites Flashcards
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
Naegleria
Associated with contact lens solution, causes keratitis or granulomatous amebic encephalitis, slow onset but encephalitis progresses to death
Acanthamoeba
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
malariae
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
Babesia
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)
Snails
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
