Nematodes Flashcards
Describe general morphology of intestinal nematodes
large, cylindrical unsegmented bodies
they live in GI tract and release eggs into feces
Describe general morphology of filariae nematodes
long slender bodies that infect blood, lymph, subcutaneous, and connective tissues
transmitted by biting flies or mosquitoes
produce larval worms called microfilariae
What are the 7 clinically relevant intestinal nematodes
- Enterobius vermicularis
- Ascaris lumbricoides
- Toxocara & Baylisascaris
- Trichuris trichiura
- Ancylostoma duodenale and Necator americanus
- Ancylostoma Brazilinese
- Strongyloide stercoralis
Describe Entrobius vermicularis in terms of common name, distribution, what causes it, symptoms, how to dx, and prevention
Common name: pinworms
Distribution: Worldwide, most common helminthic infection in N. America, occurs in crowded conditions
Cause: eggs are ingested or auto infection can occur, no known animal reservoir
Symptoms: asymptomatic, anal pruritus w/ possible secondary bacterial infection
DX: clinical manifestation and eggs on anal mucosa
Prevention : hygiene
Describe Ascaris lumbricoides in terms of what causes it, symptoms, how to dx, treatment and prevention
Cause: poor sanitation and feces used in fertilizer
Symptoms: most common helminthic infection in the world, symptoms based on infection burden.
- low burden: asymptomatic possible peritonitis from worms perforating the intestine
- high burden: Pnuemonitis (worm goes to lungs then coughed up to go to GI tract to mature)
DX: eggs in stool
Treatment: Need to treat this worm first because if not other treatments can cause worm to migrate
Prevention : sanitation education of not using feces in fertilizer
Describe Toxocara and Balylisascaris in terms of what causes it, symptoms, how to dx, treatments and prevention
Cause: exposure to eggs from feces of infected raccoon/dogs/cats
Symptoms: based on tissue it invades, where ever it ends up it causes granulomas and necrosis
DX: clinical findings, exposure to raccoon/dogs/cats and ELISA confirmation
treatments: corticoid steriods if serious pulmonary, heart, or brain involvement
Prevention : deworm pets and clean up dog/cat poo, do not keep racoons as pets
Describe Trichururis trichiuria in terms of common names, distribution, what causes it, symptoms, how to dx, and prevention
Common name: whip worm
Distribution: worldwide, where poor sanitation and feces is used as fertilizer
Cause: exposure to contaminated feces
Symptoms: asymptomatic to bloody diarrhea, anemia, and 2ndry bacterial infection depending on worm burden
DX: eggs in stool
Prevention: sanitation education of not using feces in fertilizer
Describe Ancylostoma duodenale and Nector americanus in terms of common name, distribution, what causes it, symptoms, how to dx, treatment and prevention
Common name: Hook worms
Distribution: worldwide but eggs are deposited in moist/good soil like is SE USA
Cause: barefeet in soil
Symptoms: rash at site of entry, then pnuemontitis from migrating larva. Microcytic, hypochromic anemia. emaciation and retardation d/t nutrition def
DX: eggs in stool
treatment: iron treatment in anemic
Prevention: education sanitation and shoes
Describe Ancylostoma Braziliense in terms of distribution, what causes it, symptoms, how to dx, and prevention
Distribution: beaches of subtropical and tropical regions
Cause: playing/walking in soil contaminated by dog cat feces that contain eggs
Symptoms: erythema and vesicular rxn with pruritis
some may develop Loffler syndrome (pulmonary infiltrates with peripheral eosinophilia)
DX: clinical appearance of the tunnels and a history of contact with dog and cat feces
Prevention: educating pet orders and wearing shoes in endemic areas
Describe Strongloides stercoralis in terms of distribution, what causes it, symptoms, how to dx, and prevention
Distribution: temperate climate
Cause: sexual transmission, contaminated soil, and auto infection
Symptoms: asymptomatic to ulcer w/ peripheral eosinophilia to hyerinfection syndrome in immunocompromised
DX: difficult, need 1 stool sample for 3 days
Prevention : sanitation, education, prompt treatment
Describe Trichinella spiralis in terms of distribution, what causes it, symptoms, how to dx, and prevention
Distribution: pork eating people worldwide
Cause: eating undercooked pork
Symptoms: depends on burden and migration of larva usually asymptomatic
DX:Cinical symptoms, biopsy, eosinophilia, serology
Prevention : cook meat
What are the 7 clinically relevant filaria nematodes
- Wuchereria bancrofti
- Brugia malayi
- Loa Loa
- Onchocerca volvulus
- Dracunculus medinensis,
- Mansonella sp
- Dirofilaria immitis
Describe Wuchereria bancrofti and Brugia malayi in terms of distribution, what causes it, symptoms, how to dx, and prevention
Distribution:
Wuchereria bancrofti: tropical and subtropical areas, no animal reservoir
Brugia malayi: SE Asia Japan and Korea, animal reservoir of ogs and cats
Cause: bite from infected mosquitos
Symptoms: asymptomatic to enlarged lymph nodes, elephantiatis, and ascites/pleural effusions
DX: microfilariae in blood and eosinophilia early
Prevention : control mosquitos
Describe Loa Loa in terms of distribution, what causes it, symptoms, how to dx, treatment and prevention
Distribution: rain forest of Africa
Cause: bite of infected Mango fly (Chrysops), which are present from ~10 am to 2 pm
Symptoms: asymptomatic at first, then calabar swelling in extremities, and possible migration to the eye causing swelling and impaired vision
DX: microfilariae in blood, worm in eye, calabar swelling
Treatment: diethylcarbamazine (DEC), steriods, and surgical removal of worm in the eye
Prevention: Education and protection form mango fly bite (Chrysops)
Describe Mansonella Sp in terms of distribution, what causes it, symptoms, how to dx, and prevention
Distribution:
- M. perstans=Africa, C. and S. America
- M. ozzardi= S. America and West Indies
- M. streptocerca= Africa especially Congo basin
Cause: Biting midges and blackflies
Symptoms: generally asymptomatic, lymphadenitis, rarely elephantiasis
DX: Blood smears/microfilariae in blood, serologic test and Nucleic Acid Amplification Tests
Prevention: insect repellents and protection
