Helminths Flashcards
Roundworm transmitted by ingestion that may cause pneumonia, malnutrition, and obstruction
**Ascaris lumbricoides **(giant roundworm)
- Eggs hatch in small intestine; larvae invade intestinal wall, spread to lungs (pneumonia), ascend to pharynx and are swallowed into small intestine where they mature into adults that consume intestinal contents (malnutrition, obstruction)
- Dx: Eosinophilia; rough eggs detected in feces
- Tx: pyrantel pamoate, bendazoles
Roundworm transmitted by ingestion that presents with perianal itchiness
**Enterobius vermicularis **(pinworm)
- Eggs hatch in duodenum and jejunum, mature into adults in ileum and colon, mate in colon, and lay eggs in perianal skin
- Dx: Scotch tape test
- Tx: bendazoles, pyrantel pamoate
Tapeworm (cestode) transmitted by ingestion of poorly cooked beef
Taenia saginata
- Larvae mature and grow in small intestine where the scolex (head) attaches to the intestinal wall (malnutrition) and the numerous autonomous prolottids are passed in feces
- Unlike T. solium, T saginata has not hooks on its scolex
- Tx: niclosamide + cathartic, praziquantel
Tapeworm (cestode) transmitted by ingestion of poorly cooked pork
Taenia solium
- Larvae mature and grow in small intestine where scolex attaches to intestinal wall (malnutrition) and numerous autonomous proglottids are passed in feces
- Oncospheres may penetrate intestinal wall and travel to other tissues (brain, skeletal muscle, eye), leading to cysticercosis
- Tx of intestinal infection: praziquantel
- Tx of tissue infection: praziquantel or albendazole + steroids (for neurocysticercosis)
Tapeworm (cestode) that causes Vitamin B12deficiency
Diphyllobothrium latum
- Caused by ingestion of larvae from raw freshwater fish
- Tx: Praziquantel
Roundworm transmitted by ingestion of undercooked pork
Trichinella spiralis
- Larvae mature into adults in small intestine where they penetrate intestinal wall (gastroenteritis) and spread to skeletal muscle, heart, brain (myalgias, myocarditis, encephalitis)
- Dx: eosinophilia, cysts in striated muscle
- Tx: bendazoles; steroids for myositis, myocarditis
Tapeworm (cestode) spread by ingestion that forms hyatid cysts in liver, lung, and brain
Echinococcus granulosus
- Eggs from dog feces are ingested and hatch in small intestine where their larvae penetrate intestinal wall and spread to other tissues (liver, lung, brain)
- Rupture of cyst –> severe anaphylaxis
- Dx: albendazole, pre-inject cysts with ethanol before surgery
Roundworm that penetrates the skin of feet before causing lung and intestinal infection
Strongyloides stercoralis
- Infectious filariform penetrate skin of feet (local itching), spread to lungs, ascend toward trachea and are swallowed, mature into adults in small intestine, and subsequent eggs hatch in intestinal wall (gastroenteritis); subsequent larvae may re-penetrate intestinal wall and spread to lungs (autoinfection) in immunocompromised
- Dx: detect larvae not eggs in stool (unlike hookworm); eosinophilia; string test for duodenal pathogens
- Tx: ivermectin, albendazole
Roundworm that penetrates the skin of feet to cause pneumonia, gastroenteritis, and anemia
Necator americanus, Ancylostoma duodenale (Hookworm)
- Infectious filariform penetrate skin of feet (local itching), spread to lungs, ascend toward trachea and are swallowed, mature into adults in small intestine, and attach to mucosa via suckers (gastroenteritis, anemia)
- Dx: eosinophilia detect eggs not larvae (vs. Strongyloides)
- Tx: bendazoles, pyrantel pamoate, iron for anemia
Flukes (trematodes) that are released from snails into fresh water and penetrate human tissue
**Schistasoma **(Blood fluke)
- Cercariae (larvae) penetrate human flesh and travel to portal vein where they mature into adults, which migrate in pairs to various venous plexuses
- Acute inflammatory symptoms (fever, chills, LAD)
- Chronic inflammatory symptoms (periportal fibrosis, liver/spleen granulomas, intestinal polyps, bladder carinoma)
- Dx: eggs in feces/urine; eosinophilia
- Tx: praziquantel
Roundworms transmitted via female blackfly that cause river blindness and hyperpigmented skin
Onchocerca volvulus
- Black fly bite releases larvae into skin where it matures into adults in SQ nodules and releases microfilariae which move subcutaneously through the body (thickened, hyperpigmented pruiritic rash) and to the eye (blindness)
- Dx: microfilariae in skin
- Tx: ivermectin (only effective vs. microfilariae)
“Black flies, black skin nodules, black sight”
Roundworm transmitted via female mosquitos that cause elephantiasis after 9 mo - 1 year
Wuchereria bancrofti
- Microfilariae are released into bloodstream and travel to LNs of genitals and LEs where they mature into adults over the course of a year; repeated infections lead to obstruction of lymphatic drainage (edema and scaly skin in legs and scrotum)
- Dx: microfilariae in blood at night
- Tx: diethylcarbamazine
**Brugia malayi **and Brugia timori are other lymphatic filariasis
Roundworm transmitted via deer/horse/mango fly that appears in conjunctiva
Loa loa
- Tx: diethylcarbamazine
Roundworm transmitted via fecal-oral that causes visceral larva migrans
Toxocara canis
- Tx: bendazoles
Fluke (trematode) transmitted via undercooked fish that causes bilary tract inflammation (pigmented gallstones)
Clonorchis sinensis
- Associated with cholangiocarcinoma
- Tx: praziquantel
