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Lecture 5


What is the intestinal nematode that looks like a “white snake”? Ascaris lumbricoides
Which nematode is the major cause of anemia? Ancylostoma duodenale and Necator americanus (hook worms)
Which nematode autoinfectsand causes life-threatening “hyperinfection” with HTLV-1 coinfection, steroid treatment or other immunocompromise? Stronglyoides stercoralis
Which nematode is nearest eradication? Onchocercia volvulus
What causes “river blindness?” Onchocerca volvulus
What three things determine how much helminths compromise health? 1. Host susceptibility 2. Helminth virulence 3. Worm burden
Which worms cause autoinfection? Strongyloides stercoralis, Capillaria philippinensis, and Hymenolepis nana
Which drug has the broadest spectrum against intestinal helminths? Albendazole
Why is Mebendazole used less than albendazole for intestinal helminths? It has a similar spectrum but less favorable pharmacodynamics
What is the drug of choice for infection with Strongyloides stercoralis? Ivermectin
How is infection with Ascaris lumbricoides diagnosed? 1. Ova in stool 2. Adult worms may be seen in stool, sputum or nasal secretions 3. Worms in biliary tree, pancreas or appendix by ultrasound
What are the symptoms of migrating Ascaris larvae in the lungs? fever, cough, chest pain, dyspnea, wheezing. High eosinophil count in sputum and blood. Chest xray may show opacities.
How is Ascaris lumbicoides transmitted? Consuming food contaminated with egss
Describe the life cycle of Ascaris lumbricoides. Embryonated egg is ingested. larvae hatch in bowel, migrate through wall to bloodstream and lung. larvae are coughed up and swallowed, mature to adults in bowel. Eggs are excreted in feces, are fertilized and go through cleavage over two weeks in soil.
What is Loeffler's syndrome? Pulmonary eosinophilia
How does Ascaris lumbricoides get to the lungs? larvae migrate through the blood stream to the lungs
How to Ascaris lumbricoides larvae infect the bowel? 1. Ingested eggs hatch into larvae in the bowel 2. pulmonary larvae ascend airways to the glottis and are swallowed.
How long after infection does the host begin shedding eggs? about 2 mo and for about 1 yr.
How many eggs do adult worms produce? about 200,000 per day
What are the symptoms of Ascaris lumbricoides infection of the bowel? obstruction, malnutrition. With heavy infection, worms may migrate to obstruct biliary or pancreatic ducts causing biliary colic, cholangitis or pancreatitis. Can cause acute appendicitis
True/False: heavy infection with Ascaris or other intestinal helminths have been associated with malnutrition and mental cognitive retardation. True
what are the medical treatments for Ascaris lumbricoides? 1. albendazole including mass treatment programs 2. Mebendazole 3. Pyrantel pamoate 4. ivermectin 5. Piperazine paralyzes worm but is toxic
How is biliary ascariasis treated? Endoscopic extraction and sphincteroplasty or medical treatment
What are the two hookworms? Ancylostoma duodenale and Necator americanus
How are humans infected? Contact with fecally contaminated soil, and infectious filariform larvae invade their skin
How is hookworm diagnosed? Identification of ova in stool
What is the treatment for hookworm? Albendazole or alternatively: mebendazole, pyrental pamoate but NOT ivermectin.
What is the life cycle for hookworms? filariform larvae penetrate intact skin or gut, larvae migrate to lungs through bloodstream, coughed up and swallowed. adults live in bowel, eggs are excreted in stool, rhabditiform larvae develop in soil over 7-10d
How big are hookworms in the gut? about 1cm.
How long do hookworms live in the gut? 1-9 yrs
What do hookworms live on? 0.03-0.2ml blood/day
What symptoms do hookworms cause? acute: abdominal pain chronic: anemia Also: migrating larvae elicit fever, cough, chest pain, dyspnea, eosinophilia,
How do hookworms infect neonates? Through breastmilk.
What determine the level of anemia in hookworm infected people? number of adult worms, amount and bioavailability of iron in diet.
Where is Strongyloides stercoralis endemic? southeaster US, tropical and subtropical developing areas
True/False: Strongyloides stercoralis is more prevalent than Ascaris lumbricoides, hookworms or Trichuris trichiura False
What makes Strongyloides stand out among the other intestinal nematodes? It has the capacity for autoinfection
How large are adult Ascaris lumbricoides worms? up to 30 cm. look like earthworms
How long do Ascaris lumbricoides adults live? 1-2 years
How is pulmonary infection with Strongyloides stercoralis different than the other intestinal nematodes? They travel through the VENOUS system to the lungs.
Describe the life cycle of Strongyloides stercoralis. Filariform larvae enter betw toes, venous travel to lungs, coughed up and swallowed, larvae mature into adults in gut and produce LARVAE. Pass in stool, sexual reprod of eggs grow to rhabditiform larvae in stool or autoinfection.
How do persons infected with Strongyloides stercoralis present? cough, dyspnea, wheezing, gastrointestinal symptoms, migrating skin larvae and/or eosinophilia
How do patients with hyperinfection of Strongyloides stercorali present? Colitis, polymicrobial sepsis, pneumonitis, meningitis
What is the likely protective mechanism for Ascaris lumbricoides infection? titers of parasite specific IgE correlate with resistance to infection
Describe autoinfection with Strongyloides stercoralis. filariform larvae penetrate perianal skin or bowel mucosa and cause pruritic larva currens and eosinophilia
How are immunocompromised persons additionally affected by Strongyloides stercoralis? Larger numbers of filariform larvae develop and can disseminate causing hyperinfection.
How is diagnosis of Strongyloides stercoralis made? Larvae in stool, tissue or secretions. Most sensitive is the agar plate method. 2. anti-strongyloides antibodies suggests active OR prior infection.
What is the drug of choice for Strongyloides stercoralis? Ivermectin. not all persons are cured even after multiple doses
Where is Enterobious vermicularis endemic? temperate and tropical climates
What age range is Enterobious vermicularis most prevalant? 5-10 yrs
What are the three way Enterobious vermicularis eggs are expelled by adult females? 1. Uterine contraction, death and disintergration of adult worm 3. Disruption of worms during scratching
How does the ovum of the pinworm adhere to objects? It has a thick outer albuminous layer
How do people become infected by Enterobious vermicularis (pinworm)? Ingestion of ova
What is the most important consequence of pinworm infection? Irriation/infection of perianal and perineal skin.
How are girls additionally affected by Enterobius vermicularis? They can develop vulvovaginitis when worms migrate to the vagina. Also they can develop urinary tract infection
Where do female pinworms go at the time of oviposition? They migrate out through the anus to the perianal or perineal skin.
If this worms causes a granulomatous reaction in the peritoneum, it may be confused with metastatic carcinoma. Dead worms or eggs from Enterobious vermicularis can cause granulomatous reactions resulting in peritoneal nodules. Can also be seen in vulva, vaginal wall, cervix, endometrium, salpinx, and ovaries, as well as in the liver and epididymis
Who gets eosinophilic enteritis from E. vermicularis? Persons with AIDS
How are humans infected by Trichinella spiralis? Ingestion of inadequately cooked meat containing infective larvae.
Which Trichinella species is endemic in the arctic regions? T. native
This worm can cause infection after ingestion of poorly cooked pork, sausage, wild boar, bear, walrus, cougar, horse and others Trichinella spiralis
What is the initial phase of trichinosis? larval invasion of the intestinal mucosa causes nausea, vomitin, abdominal pain, diarrhea
How long after infection with Trichinella spiralis does the systemic phase start? 1-3 weeks after ingestion of contaminated meat
What are the symptoms of the systemic phase of trichinosis? fever, myalgias, facial or periorbital edema, headache, conjunctivitis, and occasionally a rash. Extraocular muscles often affected. sometimes cardia and CNS involvement
How is trichinosis different amon the native Inuit of northern Canada? Prolonged diarrhea is the dominant symptom in reinfected persons
How is trichinosis diagnosed? 1. presentation and history 2. Creatinine phosphokinase elevation 3. anti-Trichinella antibodies 3wks after infection 4. muscle biopsy rarely necessary
What is the treatment for trichinosis? Mebendazole or Albendazole Also corticosteroids for severe symptoms. bedrest, NSAIDs for relief of fever/myalgias
How do you prevent trichinosis? Cook pork or potentially contaminated meat to at least 76.6C (170F) Also freezing can kill Trichinella spp. except T. nativa
Name two nematodes that cause cutaneous larva migrans Ancylostoma braziliense and caninum. Hookworms of dogs and cats
Describe the dermatitis associated with cutaneous larva migrans. serpiginous, papulovesicular, erythematous, pruritic lesions
What causes the rash of cutaneous larva migrans? It is a consequence of migrating larvae of intestinal nematodes of animals that cannot complete their life cycle in humans.
Where is cutaneous larva migrans prevalent? Tropical and subtropical areas of the Caribbean, Africa and Latin America. In North America: along Gulf of Mexico and southern Atlantic coasts.
How are people get cutaneous larva migrans? contact with infected soil in playgrounds, beaches or crawl spaces
What is the treatment for cutaneous larva migrans? ivermectin or albendazole or topical thiabendazole
What is the hookworm found to be a cause of eosinophilic enterits? A caninum, the dog hookworm
What are the findings of someone with eosinophilic enteritis? Eosinophilic infiltration of intestinal wall, aphthous ulceration of the ileum, regional lymphadenopathy, eosinophilia
How is the diagnosis of eosinophilic enteritis made? Finding an isolated sexually immature adult worm on endoscopy or positive serology for A. caninum.
What is the treatment for A. caninum causing eosinophilic enteritis? Albendazole or mebendazole
What are the organisms that cause visceral larva migrans? Toxocara canis or toxocara cati
How are people infected with the worms that cause visceral larva migrans? Ingestion of ova originating in animal feces.
What historical clues would make you suspect a pt has visceral larva migrans? People with PICA or history of eating clay
What causes the symptoms in visceral larva migrans? The helminthes are unable to complete their life cycle in humans so their larvae wander through various organs
What are symptoms of visceral larva migrans? Fever, cough, abdominal pain, arthralgia, oligoarticular arthritis, urticaria, neurologic symptoms.
What are physical exam findings for visceral larva migrans? Hepatomegaly, pneumonitis or dermatitis
T/F Ocular toxocariasis can present with an intraocular mass suggestive of retinoblastoma. True
What are lab findings for visceral larva migrans? Eosinophilia, elevated IgE
What is the characteristic pathologic lesion of visceral larva migrans? Granulomatous inflammatory response with eosinophils.
What is the triad highly suggestive for visceral larva migrans? eosinophilia, hepatomegaly, and hypergammaglobulinemia
High levels of isohemagglutinins against AB blood group antigens are frequently observed in which helminth disease? Visceral larva migrans
How is visceral larva migrans diagnosed? MR or ultrasound for hepatic granulomas, anti-Toxocara antibody detection, isohemagglutinins against AB blood group antigens
What is the treatment for visceral larva migrans? Diethylcarbamazine. albendazole and thiabendazole are alternatives. Corticosteroids for severe cases
What are preventative strategies against Toxocara cani/cati infections? Deworming dogs, covering sandboxes, and preventing defecation of dogs in areas where children play.
Created by: UVAPATH4
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