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1Presented by: Lauren Hannan and Chloe Jensen Trichinella spiralisPresented by: Lauren Hannan and Chloe Jensen
2Taxonomy Kingdom: Animalia Phylum: Nematoda Class: Adenophorea Order: TrichuridaFamily: TrichinellidaeGenus: TrichinellaSpecies: T. spiralis
3IntroductionTrichinella spp. is the smallest nematode parasite of humans, which has the most unusual life cycle, and is one of the most widespread and clinically important parasites in the worldWorlds largest intracellular parasiteT. spiralis is actually several strains – 8 “sibling species” are recognizedNo morphological differences among the different kinds of TrichinellaGeographic distribution: worldwide
4MorphologyMales are about 1.4 mm – 1.6 mm long, and are flat anteriorly and posteriorlyHave a large copulatory pseudobursa on each sideFemales are about twice the size as malesVulva is found near the esophagusThe single uterus of the female is filled with developing eggs in the posterior portion, while the anterior portion contains the fully developed juveniles.
5Hosts Definitive Intermediate hosts Accidental hosts Carnivorous and omnivorous animals, such as pigs or bearsIntermediate hostsPrimarily rodentsAccidental hostsHumans
6Life cycleTrichinellosis is acquired by ingesting meat containing cysts (encysted larvae) of TrichinellaOnce larvae enter the stomach and are exposed to digestive enzymes such as gastric acid and pepsin, the larvae burst out of the cysts and invade the small intestine, where they develop into adultsLive for about 4 weeks in the small intestineAfter 1 week, females release larvae that migrate to the striated muscles and encyst – alter gene expression of the host cell!Complete encystment takes about 4-5 weeksEncysted larvae can remain viable for several years
7Life cycle continuedLife cycle traditionally considered to be two epidemiologically distinct types: a domestic (involving pigs and rats, around human habitation), and a sylvatic (involving wild animals)Rodents are primarily responsible for maintaining the endemicity of this infectionCarnivorous/omnivorous animals, such as pigs or bears, feed on infected rodents or meat from other animalsHumans become accidentally infected when eating improperly processed meat of these animals (or when eating food contaminated with such meat)
9Pathogenesis Causes Trichinosis Three stages of pathogenesis: Stage 1: penetration of adult females into the mucosa:12 hours – 2 days after infectionLow grade infectionWorms migration in intestinal epithelium causes:Traumatic damage to the host tissuesInflammationNausea, vomiting, diarrhea,SweatingRespiratory difficultiesRed skin blotchesStage ends with facial edema and fever
10Pathogenesis Continued Stage 2: migration of juveniles:Damages blood vessels, creating:Localized edemaPneumonia, pleurisyEncephalitis, meningitis, nephritis, peritonitisDeafness, brain/eye damageSublingual hemorrhageDeath from myocarditis may occurDon’t stay in the heart, migrate through causing necrosis and infiltration of leukocytes
11Pathogenesis Continued Stage 3: Juvenile penetration of muscle fibers:Symptoms are varied and vagueIntense muscle painDifficulty breathing/swallowingMasseter muscle swellingWeakening pulse and blood pressure, heart damageVarious nervous disordersDeath by heart failure, respiratory complications, and kidney malfunctionHeavy infection causes:Reduced heart muscle contractionReduced stress, work, and power output
12Diagnosis Most cases go undetected Routine exams rarely detect juvenilesMuscle biopsy is the most accurate form of diagnosisDigestion of the muscle in artificial gastric enzymes for several hours
13Treatment No treatment Just relieve symptoms Thiabendazole Analgesics and corticosteroidsPurges during beginning symptoms can dislodge wormsThiabendazoleEffective in animalsHuman trials have been variable
14Control Cook pork and meats properly and freeze unused meat Watch out for “backyard butchering”Don’t used uncooked garbage for pig foodKeep pig pens cleanProper hygiene and sanitation
15Review What is the geographic range of this parasite? What kind of hosts are humans?T/F: Males are larger than femalesAfter the larvae leave the small intestine, where do they migrate to? How long can they survive there?What is the treatment method?Name a control methodWhat is the most effective diagnosis method?How does death typically occur?