Larval cestodes who cause diseases to humans

Larval cestodes who cause diseases to humans

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  Larval cestodes Lecture Jan.2020 Prof D.S.Tarimo
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  Introduction to larvalcestodes • Normally presence of adult cestodes causes mild to moderate pathology in man. • If man harbours larval stages get serious / severe pathology. • This happens when man becomes the I.H • Both Pseudophyllidean &Cyclophyllidean larval stages may occur in man.
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  Pseudophyllidean larva: plerocercoid (solidlarva) of Spirometra spps, also called sparganum. • Usually Cyclops (1st I.H) with procercoid larvae (1st stage) are ingested by small & subsequently larger fresh water fishes (2nd I.Hs). • If man is accidentally infected by swallowing Cyclops (1st I.H) with procercoid larvae in drinking water, plerocercoid larvae (Spargana) (2nd stage) will develop in man (2nd I.H). • The spargana will develop & cause pathology in sub-cutaneous or muscular tissues (swellings). Important spps include Spirometra mansoni, S.proliferum & S.mansonoides.
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  Cyclophyllidean larvae: Genus Taenia(Larval taeniasis) • Only T.solium larval stage (Cysticercus cellulosae) can accidentally occur in man, causing disease called CYSTICERCOSIS. • Normally man is the DH for T.solium (harbour the adult worm) and Pork the IH (harbour Cysticercus cellulosae). Man may accidentally become I.H for T.solium in: • Auto-infection – External, in which eggs in faeces are directly swallowed by the same person (poor hygiene) or Internal, when retroperistalisis occur and gravid segments burst - thousands of eggs in SI. • Heteroinfection - person-to-person infn: ingestion of eggs in water, vegetables or food (normal contaminative way).
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  Larval taeniasis contd.. •The eggs hatch in SI - Cysticercus cellulosae, penetrate mucosa - blood system - muscles & sub-cutaneous tissues, & CNS. • Common sites – tongue, thoracic cage, eye, brain & skin forming granulomas (except the eye). • In brain - serious pathology, get S & S of intracranial space occupying lesion – fits, loss of consciousness, paralysis etc.
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  Disease States • Taeniasis= adult tapeworm in small intestine – Usually asymptomatic (eggs or proglottids in feces) – Vague abdominal symptoms occasionally report • Cysticercosis = T. solium larvae in human tissues (eg, muscle) – Usually asymptomatic – Painless subcutaneous nodules in arms and chest • Neurocysticercosis (NCC) = cysts in the central nervous system – Most severe manifestation
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  Cysticercosis
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  Cerebral cysticercosis Cysticercosis: Disease
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  Cardiac cysticercosis Cysticercosis: Disease Ocular cysticercosis
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  Pathogenesis of Cysticerci •larva (cysticercal cysts) survive up to 5 years • living larva produce little inflammation • death of larva leads to inflammation and edema resulting in symptoms • cellular reaction eventually destroys parasite and leaves a calcified nodule
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  Clinical Manifestations • presentationis varied—depends on stage, number, size and location of cysts • seizures/convulsions most common symptoms • blocked circulation of CSF can lead to intracranial hypertension or hydrocephalus • occasionally large cysts can mimic tumors • can also cause a variety of mental and motor changes
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  Cysticercosis: Diagnosis • CNS and/orsymptoms involving other organs • History of ingesting food with T.solium eggs • Radiographic localization of cysticercal lesions in tissues
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  Genus Echinoccocus: Twospecies – E.granulosus & E.multilocularis (alveolar / multilocular hydatid disease). • E.granulosus (Unilocular hydatid disease): DH - usually dog (carry adults); IH - usually sheep, pig, goat, cattle, horse & MAN (accidental infection). • The DH discharge eggs - ingested by IH (MAN) - hatch in SI releasing onchospheres - penetrate mucosa - blood system - liver & lungs: hydatid cysts (bladder worms). Disease - pressure symptoms or anaphylactic shock due to hydatid fluid (rupture of cyst).
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  Genus Echinoccocus contd.. •E.multilocularis (alveolar / multilocular hydatid disease): Usual DHs - Dogs, cats, foxes; usual IH - Mouse, rat, MAN (accidental infection). • Eggs ingested by MAN release onchoshperes - penetrate mucosa - blood system to liver, lungs bones etc. forming budding cysts; disease due to pressure symptoms.
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  Genus Multiceps: Importantspps - M.multiceps also called Coenurus infection. • M.multiceps: Dogs & other wild canines usual DHs (harbour the adult worm). Usual I.Hs (carry larval stages) are sheep, goat, cattle & horses; and MAN as accidental infection. In sheep said to cause staggering or giddiness hence called gidworm. • Eggs accidentally ingested by man release onchospheres that penetrate mucosa - blood system - brain or spinal cord causing CNS symptoms. • Thus have Coenurus cerebralis (M.multiceps), C.glomeratus (M.glomeratus) & C.brauni (M.brauni).