Larval cestodes who cause diseases to humans

Larval cestodes who cause diseases to humans

1. Larval cestodes Lecture Jan. 2020 Prof D.S.Tarimo

2. Introduction to larval cestodes 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.

3. Pseudophyllidean larva: plerocercoid (solid larva) of Spirometra spps, also called sparganum. Usually Cyclops (1 st I.H) with procercoid larvae (1st stage) are ingested by small & subsequently larger fresh water fishes (2 nd I.Hs). If man is accidentally infected by swallowing Cyclops (1 st I.H) with procercoid larvae in drinking water, plerocercoid larvae (Spargana) (2 nd stage) will develop in man (2 nd I.H). The spargana will develop & cause pathology in sub-cutaneous or muscular tissues (swellings). Important spps include Spirometra mansoni , S.proliferum & S.mansonoides .

4. 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 – Externa l, 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).

5. 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.

6. 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

7. Cysticercosis

8. Cerebral cysticercosis Cysticercosis : Disease

9. Cardiac cysticercosis Cysticercosis : Disease Ocular cysticercosis

10. 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

11. Clinical Manifestations presentation is 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

12. Cysticercosis : Diagnosis CNS and/or symptoms involving other organs History of ingesting food with T.solium eggs Radiographic localization of cysticercal lesions in tissues

13. Genus Echinoccocus: Two species – 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).

14. 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.

15. Genus Multiceps: Important spps - 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).