Lec43 Nematodes Flashcards
What do you generally use to treat nematodes [round worms]?
- albendazole, mebendazole, pyrantel pamoate
What are the intestinal nematodes?
- ascaris lumbricoides
- hookworm [necatur americanus, ancylostoma duodenale]
- strongyloides stercoralis
- enterobius vermicularis [ping worm?]
- trichuris trichiura
What are properties of ascaris lumbricoides
- infects 1/4 of world population
- most infections asymptomatic
- clinical presentation in intestines related to obstruction
- more significant disease in children
- not attached to wall, constantly swimming against fecal stream
What is ascaris lumbricoides life cycle?
- human host, no other reservoir
- male and female worms live 1-2 yrs in lumen of duodenum and upper jejunum
- females produce 2000 eggs daily
- eggs laid in duodenum and evacuated in feces
- develop to infective stage in soil in 3-4 wks
- after ingestion –> larvae penetrate intestinal wall and enter circulation/lymph
- migrate to liver –> right heart –> lungs
- develop in pulmonary capillaries
- mature larvae enter alveoli, coughed up and swallowed –> are now mature enough to resist gastric acidity and enter duodenum
How is ascaris lumbricoides transmitted?
- ingestion of soil/food contaminated with eggs
What are clinical effects of ascaris lumbricoides?
- intestinal obstruction
- secrete digestive enzymes and use host-ingested proteins –> nutrient impairment causes reduced growth in children
- ascaris pneumonitis [loeffler’s syndrome] –> productive cough/fever/dyspnea/wheezing
What is loeffler’s syndrome?
- pneumonitis caused by ascaris
- due to hypersentitivity rxn to migrating larvae in lung
- present with productive cough, dyspnea, wheezing, fever, angioedema, urticaria, pulm infiltrates, eosinophilia
What is mech of action of benzimidazoles?
- inhibit assembly of microtubules and inhibit uptake of glucose by helminths
- get immobilization and death of helminths
- also kills larva
What do you use to treat ascaris?
benzimidazoles [albendazole or mebendazole]
What are two types of benzimidazoles?
- albendazole
- mebendazole
What can benzimidazoles treat?
- ascaris lumbricoides
- hookworm
- strongyloides stercoralis
- enterobius vermicularis
- trichurius trichiura
Where are ascaris infections?
in impoverished areas world wide
How do you diagnose ascaris
- find adult female
- look under microscope for eggs in stool
What are signs of hookworm
- microcytic anemia [not as much pigment and small RBC] = chronic iron deficient anemia
- eosinophilia
Where do you get hookworm infections?
in warm temperate climates
When you hear hookworm what should you think?
- childhood anemia in developing country
How is hookworm transmitted? life cycle??
- no reservoir hosts
- penetrates skin and migrates through venous circulation, pulm arterial irculation, alveoli, bronchi, trachea, swallowed and go to small intestine
- mature into adults in small intestine and mate
- adult worms 9mm-13mm long have two pairs of cutting plates [NA] and teeth [AD]
- live for 4-5 yrs
- feed on host small bowel mucosa and suck blood directly from site where attached to wall
- goes through free-living cycle, molts to become infective filariform larvae
What does ancyclostoma braziliense? pathogenesis?
- dog hookworm
- causes creeping eruption when enters human = wrong host –> cannot complete life cycle and get itchy tracks in skin
- after wks - mos larva dies and
What do you use to treat ancylostoma braziliense/
- single dose ivermectin or 2 days albendazole
Where is ancyclostoma braziliense common?
- southeastern US and the tropics
How do you treat hook worm?
mebendazole or albendazole
What are the two hook worm species?
- necatur americanus
- ancyclostoma duodenale
How do you diagnose hook worms?
eggs in stool
What are signs of strongyloides steroralis?
- causes severe hyperinfection syndrome in immunocompromised [have lots of bacterial infections at same time]
- can see worsening after you give steroids
- intestinal obstruction
- nutritional deficiencies
- pulm infiltrates
What are active treatments against s. stercoralis?
- ivermectin
- albendazole
- thiabendazole
Where is strongyloides stercoralis world wide?
worldwide, in SE US
Worsening symptom on steroids what should you think?
strongyloides
How is strongyloides transmitted?
penetration of intact skin by filariform larvae
How is strongyloides diagnosed?
- visualization of larvae in stool, sputum, biopsied tissue
- serologic evidence of past exposure
what is pathogenesis of infection?
- penetrates skin
- through blood to lungs
- coughed up and swallowed
- thousands of eggs per day, hatch in intestinal lumen, shed in stool as larvae
- free form life cycle
- maintain auto-infection cycle sometimes for decades because larvae can reinfect via perianal skin when they are being excreted
What are the intestinal worms with migratory phase in lungs?
- ascaris lumbricoides
- necator americanus [hookworm]
- ancyclostoma duodenale [hookworm]
- strongyloides stercorales
What is pinworm?
- enterobius vermicularis
What is whipworm? sign?
- trichurius trichuria
- causes rectal prolapse
What is dog helminth? sign?
- toxocara canis
- causes visceral larva migrans and retinal larva migrans
- reason for sandbox covers
Where is enterobius vermicularis prevalent?
- throughout world including US
What are signs of pinworm?
- many infections asymptomatic
- ma have: perianal itching, vaginitis from worms migrating ectopically
What is the most common intestinal nematode infection in US?
- enterobius vermicularis
Is there a reservoir for enterobius vermicularis?
nope! only humans
What are risk factors of pinworm spread?
- moderate humidity
- dense indoor crowding
- high proportion of school-age children increases prevalence
What is life cycle of pinworm?
- at night gravid female migrates to perianal and perineal region to lay eggs
- eggs mature in 6 hrs and transferred from perianal region to mouth = autoinnoculation [scratch butt then suck thumb]
What are lateral alae?
- on adult enterobius worm, allow it to move easily along GI tract mucosa
How is enterobius transmitted?
- ingestion of embryonated eggs from stool of infected individual
What is diagnostic test for pinworm?
- identify ova in perianal area using scotch tape test
What is treatment for enterobius/
- pyrantel pamoate or mebendazole or albendazole
Who/where is trichuris trichiura infection usually found?
- mostly children of low socioeconomic status
- warm most climates –> SE Asia, sub saharan africa, caribbean islands
- esp. found where human feces used as fertilizer
What is polyparasitism?
- having multiple parasites
- common with trichuris trichiura and ascaris/hookworm/malaria
What are properties of trichuris trichiura?
- adult worm 3-4.5 cm
- anterior end threaded into epithelial tunnel
- posterior end protrudes into small intestine
What is associated wtih trichuris trichiura?
rectal prelapse
How is trichuris transmitted?
- ingestion of eggs from stool
What are clinical signs of trichuri trichiura?
- diarrhea
- abdominal pain
- rectal prolapse
How is trichuris diagnosed?
- identification in stoll of barrel shaped eggs with characteristic polar plugs
How is trichuris treated?
mebendazole or albendazole
What are diseases of tissue nematodes
- lymphatic filiariasis
- river blindness [onchocerciasis]
What are tissue nematodes?
diseases whos adult phase is outside of intestinal tract
What is lymphatic filariasis?
- infected mosquito introduces 3rd stage filarial larvae onto skin of human host
- larvae penetrate bite wound and develop into adult
- adult resides in lymphatic channels
- adults produce microfilariae that migrate into blood channels moving actively through lymph and blood
What are clinical manifestations of lymphatic filiarisis
- disrupt normal lymphatic flow
- chronic lymphedema –> elephantiasis
- damage to lympathics stays after adult worms dead or treated
How is lymphatic filiarasis transmitted?
mosquito bite, introduce mirofiliari
What is geo distribution of parasites that cause lymphatic filiarasis?
- wuchereria bancrofit in tropical areas
- onchocerca volvulus in Africa, latin ameria, middle east
- others endemic to asia or indonesia or south america etc
When are highest times of microfilarisis?
- at night –> adult worms release microfilariae at night at same time as mosquitos feed
What is river blindness? Effects?
- onchocerca volvulus adult worms live in subcutaneous tissue
- microfilariae migrate in subcutaneous tissue causes pruritis and hypopigmnetations
- migrate to eye and cause blindess
What is life cycle of onchocerca vovlulus?
- infected blackfly brings filarial larvae to skin
- pentrates into bite wound
- in subcutaneous tissue larvae develop into adult filariae
- adult filariae reside in subcutaneous nodules
- female worms in nodules live 9 yrs
Where are onchocerca vovlulus found in body?
- typically in skin and lymphatic connective tissue
- also in peripheral blood, urine, sputum
What is geo distribution of onchocerca volvulus?
- mainly africa, also latin america and middle east
What are clinical manifestations of river blindness?
- subcutaneous nodules
- dermatitis
How is river blindness diagnosed?
skin snips
How is river blindness treated?
ivermectin
How is dracunculis medinsis transmitted?
by drinking water contaminated by larvae that infect copepods
What is pathogenesis of dracunculiasis?
- larvae penetrate host stomach and intestinal wall and enter ab cavity and retroperitoneal space
- adult females migrate toward skin surface
- 1 yr after infection female worm induces blister on skin
- when lesion comes into contact with water, female worm emerges and releases larvae
What is treatment for dracunculiasis?
- local cleansing of lesion and local application of antibiotics
- mechanical extraction of worm over period of days
- no curative antihelmnithic treatment available
- interupt transmission by filtering water through nylon cloth
