Parasitology

Question 1

Pt presents with bloating, flatulence, foul smelling, fatty diarrhea

Answer 1

Giardia Lamblia causing giardiasis

Trasmitted via cysts in water

dx when multinucleated trophozoites or cysts are found in stool and antigen detected

tx: metronidazole

Question 2

Pt presents with bloody diarrhea and RUQ pain. It was later found that they had a liver abscess and flask shaped ulcers in their colon.

Answer 2

Entamoeba histolytica

transmitted via cysts in water

Entamoeba eats erythroctes - trophozoites engulf the RBCs

tx with metronidazole

Question 3

Pt was dx with AIDS 3 years prior and now presents with severe diarrhea. Oocysts were identified on an acid fast stain

Answer 3

Cryptosporidium

Severe diarrhea in aids
Mild dz if immunocompetent (give nitazoxanide)
Prevent by filtering water supplies

Question 4

Pt is a newborn that presents with chorioretinitis, hydrocephalus, and intracranial calcifications

Answer 4

This is the classic triad for Congenital toxoplasmosis caused by toxoplasma gondii

If reactivation in AIDS then see brain abscesses on MRI

Cysts in meat (most common) or oocytes in cat feces. Crosses placenta and so pregnant women should avoid cats

Tx with sulfadiazine + pyrimethamine

Question 5

Pt went swimming in a warm freshwater lake and then developed meningoencephalitis

Answer 5

Naegleria fowleri

Enters via cribriform plate

Dx when amoebas are found in the CSF

Tx with Amphotericin B

Question 6

Pt was bit by a fly and now presents with enlarged lymph nodes, recurring fever, somnolence, coma

Answer 6

Trypanosoma brucei

Tsetse fly

Trypomastigote in blood smear

Tx with suramin for bloodborne disease or melarsoprol for CNS penetration (“melanin helps with sleep”)

Question 7

Pt presents with fever, headache, anemia, and splenomegaly

Answer 7

Malaria due to plasmodium spp thats transmitted via anopheles mosquito

Plasmodium vivax/ovale - 48 hr cycle, fever on first and 3rd day, dormant form (hypnozoite) in liver

Plasmodium falciparum - severe irregular fever patterns. Cerebral malaria where parasitized RBCs occlude capillaries in brain, kidneys, lungs

Plasmodium malariae - 72 hr cycle

on blood smear you see trophozoite ring within RBC, schizont containing merozoites, red granules (Schuffner stippling) throughout RBC cytoplasm seen with P vivax/ovale

Question 8

Pt was bit by a tick and now presents with fever and hemolytic anemia. Pt is from northeastern untied states

Answer 8

Babesia from Ixodes tick

Babesiosis - fever and hemolytic anemia. Asplenia increases severity of dz

look for ring form and latese cross on blood smear

Question 9

Pt is from South America and presents with one eye appearing swollen shut after being bit by a bug

Answer 9

This is the Romana sign due to the bite of a triatomine bug which is a reduviid bug that deposits feces in a painless bite

Chagas disease- dilated cardiomyopathy with apical atrophy, megacolon, megaesophagus

See trypomastigote in blood smear

Question 10

Visceral and cutaneous Leishmaniasis

Answer 10

Leishmania donovani

Visceral - spiking fevers, hepatosplenomegaly, pancytopenia

Cutaneous- skin ucers

Spread via sandfly. Macrophages containing amastigotes

Question 11

Pt presents with foul smelling green discharge from vagina accompanied with burning and itching. You note a “strawberry cervix”

Answer 11

Trichomonas vaginalis

STI

Trophozoites (motile) on wet mount

Question 12

Pt received the tape test in the anal region and saw eggs

Answer 12

Enterobius vermicularis (pinworm)

Question 13

Ascaris lumbricoides (giant roundworm)

Answer 13

obstruction at ileocecal valve
biliary obstruction
intestinal perforation

migrates from the nose/mouth

knobby coated oval eggs in feces under microscope

Question 14

Strongyloides stercoralis (thread worm)

Answer 14

Larvae in soil penetrate skin

Autoinfection: some larvae may penetrate the intestinal wall to enter the bloodstream without leaving the body

Question 15

Ancylostoma duodenale, Necator americanus (hook worms)

Answer 15

microcytic anemia by sucking blood from intestinal wall

cutaneous larva migrans - pruritic, serpiginous rash from walking barefoot on contaminated beach

Question 16

Trichinella spiralis

Answer 16

From undercooked meat (esp pork)

Larvae enter bloodstream, encyst in striated mm and cause inflammation

Trichinosis - fever, vomiting nausea, periorbital edema, myalgia

Question 17

Trichuris trichiura (whipworm)

Answer 17

Loose stools, anemia, rectal prolapse in children due to heavy infection

Question 18

Toxocara canis

Answer 18

Visceral larva migrans - nematodes migrate to blood through intestinal wall causing inflammation and damage

Heart, liver, eyes, and CNS

Question 19

Onchocerca volvulus

Answer 19

Female blackfly

causes river blindness - black flies, black skin nodules, black sight

Question 20

Loa Loa

Answer 20

Swelling in skin
Worm in conjunctiva
deer fly, horse fly, mango fly

Question 21

Wuchereria bancrofti

Answer 21

Lymphatic filariasis (elephantiasis) - worms invade lymph nodes –> inflammation –> lymphedema

female mosquito

Question 22

Taenia solium

Answer 22

Intestinal tapeworm: Ingestion of larvae encysted in undercooked pork

Cysticercosis, neurocysticercosis (cystic CNS lesions, seizures) : ingestion of eggs in food contaminated with human feces

Question 23

Diphyllobothrium latum

Answer 23

Vitamin B12 deficiency (tapeworm competes for B12) –> megaloblastic anemia

Ingestion of larvae in raw freshwater fish

Question 24

Echinococcus granulosus

Answer 24

Hydatid cysts “eggshell calcification” in liver

cyst ruptures and causes anaphylaxis

Ingestion of eggs in food contaminated with dog feces

Question 25

Schistosoma

Answer 25

S. Mansoni , egg with lateral spine- liver and spleen enlargement, fibrosis, inflammation, portal hypertension

S. Haematobium , egg with terminal spine- squamous cell carcinoma of the bladder, painless hematuria, pulmonary HTN

Question 26

Clonorchis sinensis

Answer 26

Biliary tract inflammation - pigmented gallstones

cholangiocarcinoma

undercooked fish

Question 27

Sarcoptes scabiei

Answer 27

mites burrow into stratum corneum
serpiginous burrows in webspace of hands and feet

tx with permethrin cream

Question 28

pediculus humanus phthirus pubis

Answer 28

Blood sucking lice

can transmit Rickettsia prowazekii (epidemic typhus)
Borrelia recurrentis (Relapsing fever)
Bartonella quintana (trench fever)