Trichinellosis (trichinosis) is caused by nematodes (roundworms) of the genus Trichinella. In addition to the classical agent T. spiralis (found worldwide ...SkipdirectlytositecontentSkipdirectlytopageoptionsSkipdirectlytoA-ZlinkParasites-Trichinellosis(alsoknownasTrichinosis)SectionNavigationCDCHomeFacebookTwitterLinkedInSyndicateBiologyMinusRelatedPagesCausalAgents:Trichinellosis(trichinosis)iscausedbynematodes(roundworms)ofthegenusTrichinella.InadditiontotheclassicalagentT.spiralis(foundworldwideinmanycarnivorousandomnivorousanimals),severalotherspeciesofTrichinellaarenowrecognized,includingT.pseudospiralis(mammalsandbirdsworldwide),T.nativa(Arcticbears),T.nelsoni(Africanpredatorsandscavengers),T.britovi(carnivoresofEuropeandwesternAsia),andT.papuae(wildanddomesticpigsofPapuaNewGuineaandThailand).TrichinellazimbabwensisisfoundincrocodilesinAfricabuttodatetherearenoknownassociationsofthisspecieswithhumandisease.LifeCycle:Dependingontheclassificationused,thereareseveralspeciesofTrichinella:T.spiralis,T.pseudospiralis,T.nativa,T.murelli,T.nelsoni,T.britovi,T.papuae,andT.zimbabwensis,allbutthelastofwhichhavebeenimplicatedinhumandisease.Adultwormsandencystedlarvaedevelopwithinasinglevertebratehost,andaninfectedanimalservesasadefinitivehostandpotentialintermediatehost.AsecondhostisrequiredtoperpetuatethelifecycleofTrichinella.Thedomesticcyclemostofteninvolvedpigsandanthropophilicrodents,butotherdomesticanimalssuchashorsescanbeinvolved.Inthesylvaticcycle,therangeofinfectedanimalsisgreat,butanimalsmostoftenassociatedassourcesofhumaninfectionarebear,mooseandwildboar. Trichinellosisiscausedbytheingestionofundercookedmeatcontainingencystedlarvae(exceptforT.pseudospiralisandT.papuae,whichdonotencyst)ofTrichinellaspecies.Afterexposuretogastricacidandpepsin,thelarvaearereleasedfromthecystsandinvadethesmallbowelmucosawheretheydevelopintoadultworms.Femalesare2.2mminlength;males1.2mm.Thelifespaninthesmallbowelisaboutfourweeks.After1week,thefemalesreleaselarvaethatmigratetostriate