Which of the following parasite can cause 'duodenal stricture'?
Ans. b (Strongyloides stercoralis) (Ref. H- 16th ed., p 1235, 1258; Table 192-2; Table 201-1)The Strongyloides stercoralis larvae inhabit duodenum of humans, attaching themselves to mucous membrane, causing inflammation, and eventually duodenal stricture results.SpeciesDisease/OrgansForm/ TransmissionDiagnosisTreatmentNecator americanus(New World hookworm)Hookworm infectionLung migration - pneumonitisBloodsucking - anemiaFilariform larva penetrates intact skin of bare feetFecal larvae (up to 13 mm) and ova; oval, transparent with 2-8 cell stage visible insideFecal occult blood may be presentMebendazole and iron therapyAncyclostoma brazilienseAncylostoma canium(dog and cat hookworms)Cutaneous larva migrans intense skin itchingFilariform larva penetrates intact skin but cannot mature in humansUsually a presumptive diagnosis, exposureThiabendazoleStrongyloides stercoralisThreadworm strongyloidiasis;Early: pneumonitis, abdominal pain, diarrheaLater: malabsorption, ulcers, bloody stoolsFilariform larva penetrates intact skin, autoinfection leads to indefinite infections unless treatedLarvae in stool, serologyThiabendazoleTrichinella spiralisTrichinosis: larvae encyst in muscle - painViable encysted larvae in meat are consumed: wildgame meatMuscle biopsy; clinical findings: fever, myalgia, splinter hemorrhages, eosinophiliaSteroids for severe symptoms and mebendazoleSTRONGYLOIDIASIS# S. stercoralis is distinguished by its ability--unusual among helminths--to replicate in the human host. This capacity permits ongoing cycles of autoinfection as infective larvae are internally produced.# Life cycle- Humans acquire strongyloidiasis when filariform larvae in fecally contaminated soil penetrate the skin or mucous membranes.0- The larvae then travel through the bloodstream to the lungs, where they break into the alveolar spaces, ascend the bronchial tree, are swallowed, and thereby reach the small intestine.# Clinical Features- Recurrent urticaria, often involving the buttocks and wrists, is the most common cutaneous manifestation.- Migrating larvae can elicit a pathognomonic serpiginous eruption, larva currens ("running larva")--a pruritic, raised, erythematous lesion that advances as rapidly as 10 cm/h along the course of larval migration.- Adult parasites burrow into the duodenojejunal mucosa and can cause abdominal pain, which resembles peptic ulcer pain except that it is aggravated by food ingestion.0 It causes duodenal stricture.- Eosinophilia is common, with levels fluctuating over time.- Abrogation of host immunity (glucocorticoid therapy/immunosuppressive agents), leads to hyperinfection, with the generation of large numbers of filariform larvae.- Strongyloidiasis is a frequent complication of infection with human T cell lvmphotropic virus type I. but disseminated strongyloidiasis is not common among patients infected with HIV.# Diagnosis- In uncomplicated strongyloidiasis, the finding of rhabditiform larvae in feces is diagnostic.- The eggs are almost never detectable because they hatch in the intestine.- If stool examinations are negative, Strongyloides can be assayed by sampling of the duodenojejunal contents by aspiration or biopsy.6- ELISA for antibodies to excretory-secretory or somatic antigens of Strongyloides is a sensitive method.# Treatment- Even in the asymptomatic state, strongyloidiasis must be treated due to the potential for fatal hyperinfection. Ivermectin (Single 0.2 mg/kg dose yields highest cure rates) ) is more effective than albendazole (400 mg x3 days,repeated at 2 wks).- For disseminated strongyloidiasis, treatment with ivermectin should be extended for at least 5 to 7 days.Additional Educational Points:# STRING TEST to sample duodenal contents is sometimes necessary to detect Giardia lamblia, Cryptosporidium, and Strongyloides larvae.# Alternative tests for detection of Strongyloides larvae include duodenal aspirate or jejunal biopsy; serology; sputum or lung biopsy for filariform larvae in disseminated disease.# Some species, including Strongyloides stercoralis and Enterobius vermicularis, can be transmitted directly from person to person, while others, such as Ascaris lumbricoides, Necator americanus, and Ancylostoma duodenale, require a soil phase for development.# Strongyloides stercoralis is a gastrointestinal parasitic infection that has a pattern of endemic distribution similar to that of HTLV-I.# Ivermectin is active at low doses against a wide range of helminths and ectoparasites. It is the drug of choice for the treatment of onchocerciasis, strongyloidiasis, cutaneous larva migrans, and scabies.PARASITIC NEMATODESFeatureAscaris lumbricoides (Roundworm)Necator americanus, Ancylostoma duodenale (Hookworm)Strongyloides stercoralisTrichuris trichuria(whipworm) (pinworm)Enterobius vermicularisGlobal prevelance in humans (millions)1273127750902300Endemic areasWorld wideHot, humid regionsHot, humid regionsworldwideWorldwideInfective stageEggFilariform larvaFilariform larvaEggEggRoute of infectionOralPercutaneousPercuteneous or auto-infectionOralOralGastrointestinal location of wormsJejunal lumenJejunal mucosaSmall-bowel mucosaCecum, colonic mucosaCecum, appendixAdult worm size15-40 cm7-12 mm2 mm30-50 mm8-13 mm (female)Pulmonary passage of larvaeYesYesYesNoNoIncubation period (days) 60-7540-10017-2870-9035-45Longevity1yN.americanus: 2-5 yA. duodenale: 6-8 yDecades (owing to autoinfection)5y2 monthsFecundity (eggs/ day/ worm)240,000N.americanus 4000-10,000A.duodenale:50005000-10,0003000-70002000Principal symptomsRarely gastro- intestinal or biliary obstructionIron-deficiency anemia in heavy infectionGastrointestinal symptoms: malabsorption or sepsis in hyperinfectionGastrointestinal symptoms, anemiaPerianal pruritusDiagnostic stageEgg in stoolEgg in fresh stool, larva in old stoolLarvae in stool or duodenal aspirate; sputum in hyperinfectionEgg in stoolEggs from perianal skin on cellulose acetate tapeTreatmentMebendazoleAlbendazolePyrantel pamoateMebendazolePyrantel pamoateAlbendazole1. Ivermectin2. Albendazole3. ThiabendazoleMebendazoleAlbendazoleMebendazolePyrantel pamoateAlbendazole
Ascaris lumbricoides
Strongyloides stercoralis
Chlonorchis sinensis
Ankylostoma duodenale
Infection