Apr30 M1-Nematodes Flashcards
3 categories of helminths (worms. pluricellular parasites)
nematodes (roundworms), cestodes and trematodes
5 intestinal nematodes (roundworms)
- strongyloides
- ascaris
- trichuris
- hookworms (ancylostoma and necator)
- enterobius
3 systemic nematodes (roundworms)
- trichinella
- toxocara
- filaria (lymphatic, loa loa, onchocerca)
how a parasitic nematode infection is diagnosed normally
microscopy/detection of eggs in the stool (the parasite stays in the intestines)
trichuris trichiura mode of transmission and what is transmitted
fecal-oral
the eggs are what is transmitted
trichuris trichiura where the parasite lives
in the colon
trichuris trichiura (whipworm) clinical presentation in individual with low burden of infection (Canada or immigrant living in Canada)
asymptomatic, no eosinophilia
trichuris trichiura (whipworm) clinical presentation in individual with high burden of infection (tropics, worm load dependent)
- dystentery
- prolapsed rectum
- iron deficiency anemia
- clubbing (hypertrophic osteoarthropathy)
trichuris trichiura (whipworm) life cycle (linked to transmission) + reservoir
- lives in humans only (fecal-oral between humans)
- main transmission is human feces used as fertilizer and then it gets in food
enterobius vermicularis (pinworm) mode of transmission
fecal-oral (it helps that the mom worm living in the distal colon lays eggs around the anus at night so you’ll scratch and spread them everywhere)
who gets enterobius vermicularis (pinworm) infections particularly
children
enterobius vermicularis (pinworm) clinical pres low burden (Canada)
- asymptomatic
- perianal itch
- recurrent UTIs (female children)
enterobius vermicularis (pinworm) clinical pres high burden (tropics)
- asymptomatic
- perianal itch
- recurrent UTIs (female children) (same as low burden)
resistant worms definition
- doesn’t exist
- if you have a maintained infection with a worm that doesn’t live long, it means you have eggs in your environment (if worm lives 2-3 months, dies after that)
enterobius vermicularis (pinworm) transmission
same as whipworm, fecal-oral. eggs layed. ends up in someone’s mouth
ascaris lumbricoides (roundworm) transmission
fecal-oral
geohelminths definition
group of helminths with life cycle similar to ascaris, trichuris and enterobius and also called SOIL TRANSMITTED helminths (bc human feces in soil)
geohelminths (trichuris (whipworm), enterobius (pinworm), ascaris (roundworm), hookworms, etc.) common clinical association
- geohelminth triad
- associated with cognitive and growth development problems in children
ascaris lumbricoides (roundworm) clinical pres in low burden (Canada)
asymptomatic
ascaris lumbricoides (roundworm) clinical pres high burden (tropics)
- abdominal pain
- SI obstruction (lives in SI)
- biliary tree obstruction (if very heavy burden and crawled up)
- perforation of intestine suture
- malnutrition
- eosinophilia (if in its migratory phase)
how ascaris (roundworm) life cycle differs from trichuris (whipworm) and enterobius (pinworm)
when you swallow eggs (that an adult worm hatched in someone else’s SI), it goes in your SI, hatches (hatches = mot pour couver et éclore), bursts through intestinal mucosa and goes in portal circulation, liver, IVC, lungs, airways, pharynx, esophagus, back in SI and NOW adult (eosinophilia DURING this cycle only)
how ascaris (roundworm) dx differs slightly from trichuris (whipworm) and enterobius (pinworm) dx
for ascaris, you CAN pass WORMS in the stool and see them (not just eggs)
2 genera (pl. genus) of hookworms
- ancylostoma duodenale
- necator americans
hookworms (ancylostoma and necator) mode of transmission
- fecal-skin transmission (don’t step on poop). the LARVA gets through the skin
- contact with feces contaminated soil
hookworms (ancylostoma and necator) life cycle
like ascaris, it’s just that they get in through the skin, reach lymphatics and small veins (do the whole, liver-IVC to esophagus thing like ascaris) with eosinophilia DURING this migration
hookworms (ancylostoma and necator) infection symptoms low burden
- asymptomatic
- eosinophilia (migration stage)
hookworms (ancylostoma and necator) infection symptoms high burden (tropics)
- minor abdominal pain
- iron deficiency anemia (bc this worm is different. bites in your intestines and eats your blood rather than sharing food with you)
- malnutrition
- geohelminth triad (malnutrition and development problems)
difference between age groups affected by whipworms (trichuris), roundworms (ascaris) and hookworms (ancylostoma and necator)
- whipworms and roundworms affect children mostly (bc they eat poop the most. fecal-oral)
- hookworms affect everyone (bc even adults walk barefoot)
what happens if you have an animal hookworm (cutaneous larva migrans or ancylostoma caninum)
- worm stays in your skin and dies
- cutaneous larva migrans is very itchy
how is strongyloides stercoralis very different form the other nematodes
others = you eat one egg, you get one worm (the eggs the worm sheds are for the next host) strongyloides = can replicate, multiply inside the same human host. can eat a few eggs and end up with a million worms
2 life cycles of the strongyloides stercoralis, related to its 2 modes of transmission
- hookworm-like: larva passed on the ground from human feces. step on it and wtv, gets through the skin, does veins-IVC-esophagus whole migratory route
- fecal-oral route. eat egg. hatches in gut. breaches gut mucosa and does the whole portal-IVC-esophgus thing
strongyloides stercoralis transmission and who’s at risk and gets it more
- contact with feces contaminated soil
- immunocompromised (but not AIDS)
- HTLV1 (increases leukemia chance)
strongyloides stercoralis clinical pres in Canada
- asymptomatic
- dyspepsia
- cutaneous larva currens
- eosinophilia
- disseminated strongyloides
strongyloides stercoralis clinical pres in tropics
- asymptomatic
- dyspepsia
- cutaneous larva currens (skin crawling)
- eosinophilia (now permanent bc migratory cycles all the time)
- disseminated strongyloides
- chronic diarrhea
- weight loss
- *SAME SYMPTOMS AS CANADA**
why strongyloides clinical pres is same in Canada and in tropics
- no more burden difference
- burden ends up being the same because the worms multiply inside you anyways
charact of the eosinophilia in strongyloides stercoralis infection
- as usual only during migratory cycle
- but migratory cycles always happening bc worm multiplying
- constant eosinophilia
strongyloides stercoralis: how do you dx (based on a similarity with ascaris)
- like roundworms (ascaris), worms can pass in the stool
- stool culture on agar will reveal stool being dragged by the larvae (and diff bacterial colonies seeding on their way)
disseminated strongyloidiasis in the immunocompetent
- adult worms and larvae limited to submucosa of SI
- internal and external autoinfective cycles are very limited
disseminated strongyloidiasis in the immunosuppressed (steroids, HTLV1, etc.)
larvae can wonder anywhere in the body (and carry gut bacteria with them)
- meningitis
- bacteremia
- pneumonitis
- peritonitis
- necrosis of intestine wall
what is cutaneous larva currens
strongyloides stercoralis worm gets out of anus and enters the perianal skin (bc is also a way of transmission) and then the rash it formed bc it’s in the skin moves 1 cm per hour (currens for courir)
trichinella (a systemic roundworm, nematode) species that cause trichinosis
- trichinella spiralis in the pig (think spiralis for pig tail)
- trichinella nativa in walrus (Natives eat walrus)
- note: can really be in any carnivore*
mode of transmission of trichinella (and life cycle) and reservoir
- sits without multiplying inside cysts in muscles of carnivorous animals (humans included)
- transmitted when you eat raw meat with a cyst in it
- trichinella will go in your gut and migrate from there to your muscle and form cysts in your muscle
2 types of presentation of trichinosis and depend on what
- no immunity (first infection) = MYOPATHIC (classic)
2. secondary response (2nd infection or more) = DIARRHEIC
myopathic trichinosis presentation
- muscle pain, weakness
- fever
- edema
- CPK (creatine phosphokinase)
- eosinophils
- IgG IgM for trichinella
- positive muscle bx
- abnormal EMG
diarrheic trichinosis presentation
(have immunity so attack larvae in the gut)
- diarrhea only (no fever or edema)
- normal CPK
- eosinophilia
- trichinella IgG
- negative muscle bx
- normal EMG
how trichinosis is diagnosed
- symptoms
- eosinophilia
- CKT (creatine kinase test)
- serology
- bx
toxocara canis (systemic roundworm, nematode) life cycle
(is an animal ascaris)
- animal eats egg, larvae do whole migration, other animal will eat poop with eggs
- if human eats egg, toxocara stays in SI and wanders in intestine and peritoneum
toxocara canis (canis for canine) infection name in humans
visceral larva migrans (wanders in SI, peritoneum, eye, liver but dies if liver after forming granuloma)
visceral larva migrans (toxocara) symptoms
- HIGH eosinophilia (bc it wanders in the body)
- weakness
- pruritus
- dyspnea (allergic phenomenon)
- rash, urticaria
- abd pain
- dizziness
- cough
dx of toxocara canis (visceral larva migrans) done how
- serology
- clinical picture
filiriasis is caused by what
filaria = a group of nematodes, a group of systemic round worms (like trichinella and toxocara)
2 species of filaria that cause lymphatic filariasis + (elephantiasis) (live in lymph nodes and obstruct them)
-wuchereria bancrofti
-brugia malayi
(adult worms are in lymphatics, etc.)
how lymphatic filariasis (wuchereria bancrofti
and brugia malayi) is transmitted
culex and anopheles mosquito
vector transmission
possible clinical presentations of wuchereria bancrofti infection (filaria)
- asymptomatic
- inflammatory (lymphangitis in legs and arms, epididimitis, funiculitis)
- obstructive (elephantiasis, chyluria, hydrocoele)
- tropical pulmonary eosinophilia
Loa loa (eye worm) filaria transmission
crysops fly (vector transmission)
Loa loa (eye worm) filaria symptoms
- calabar swelling (transient hand swelling, tissue angioedema bc of allergic type reaction)
- red eye bc worm crosses conjunctiva but doesn’t cause problems
- transient swollen eye
loa loa symptoms in native of the tropics vs in white individual
native = tolerant, HIGH burden, eye worm and nothing else (no eosin. no symptoms) white = strong immune response, LOW burden, eosinophilia, calabar swelling, allergic type rx, NO EYE WORM
onchocerca volvulus (river blindness worm) mode of transmission
simulium damnosum (black fly) (vector transmission)
onchocerca symptoms
- nodule in adults (if superficial infection)
- dermatitis due to microfilaria migrating in skin (sauda). = itchy dry skin
- corneal precipitates, cornea opacification and corneal blindness
how can you diagnose filaria infection with blood culture
- larvae (microfilaria) are in the blood and the dermis
- blood test: thick and thin smear, Ag capture, etc. to detect the MICROFILARIA
- skin bx with no blood for onchocerca (microfilaria in skin)
