Flashcards
L8 Helminths 2
Cards in this deck (21)
- 1Cestode features 8• aka “tapeworms”
• Flat, ribbon-like parasitic worms
• Adults live in gut tract of vertebrates
• Larval stages live in tissue of vertebrates and invertebrates
• No gut tract – absorb all their nutrients through their surface!
• Hermaphroditic
• Length can be a few mm to metres and metres!!
• Cysticercosis and echinococcosis are the two main burdensome cestode associated diseases. - 25 cestode structure• Adults have segmented bodies
• With a head (scolex) attaching to the intestinal wall
• A neck (germinal region) which produces the segments (proglottids) which make up the body (strobila) - 33 species humans are definite hosts for, 2 where humans are intermediate hostsHumans definite hosts for some taenia, dibothriocephalus/diphyllobothrium and hymenolepis species
Humans intermediates for echinococcus, t. solium. - 4taenia types 2• Beef tapeworm = T. saginata
• Pork tapeworm = T. solium - 5Life cycle taenia 6Adult lives in gut of human, sheds proglottids from its body
Proglottids either rupture in gut and releases eggs or passed whole (dx)
Cows (T. saginata) or pigs (T. solium) ingest food contaminated by eggs or whole proglottids (containing 50-100,000 eggs!)
Eggs hatch, penetrate gut, larval stages move to muscle and encyst as cysticerci
Humans ingest undercooked meat with live cysts
Cysts hatch in human gut and develop into adults - 63 symptoms and 5 features of taenia saginata• Humans are the definitive host for adult worms
• Cows are the intermediate host
• Eggs only infective to cattle
• Intestinal infection by adults = taeniasis
• May be asymptomatic
• Or cause diarrhoea, bloating, abdominal pain - 74 features of taenia solium, 2 manifestations and why there are 2• Humans are the definitive host for adult worms
• Pigs are the intermediate host
• But - eggs also infective to humans, who can also be intermediate hosts
Can give rise to either taeniasis (if adult) or cysticercosis (if larva)
• Endemic in most of southern africa, asia. - 86features of cysticercosis• Caused by human ingestion of T. solium eggs (NB: not meat!)
• May be from unwashed vegetation, or faeco-oral (human-human)
• Can get autoinfection from intestinal taeniasis!
• Dormant cysts form in any tissue
• Eventually die and calcify if not ingested
• Problematic areas are brain and eyes - 96 Neurocysticercosis features:• The most important medical consequence of cysticercosis
• Cysticerci encyst in brain
• Total infected estimated by WHO to be 2.5-8.3 million
• 1.9m DALYs lost
• Causes epilepsy and occasionally hydrocephalus
• Can be cause of 30-70% of epilepsy cases in endemic regions - 102 dx taeniasis• Stool microscopy for eggs (unable to distinguish between T. solium and T. saginata
• Examination of proglottids – speciation by number of uterine branches - 11Dx Cysticercosis: CNS, Muscle, Eye, SerologyCNS: neuroimaging, CSF
Muscle: biopsy, imaging
Eye: ophthalmic examination, imaging (US)
Serology - 122 tx taeniasisTx Taeniasis:
Praziquantel
Niclosamide - 136 tx cysticercosis• If asymptomatic, limited need for treatment
• Symptoms from CNS infection: antihelminthics (albendazole or praziquantel) +/- antiepileptic medication
• Seizure control is the priority!
• Give with steroids to minimise inflammation
• May need surgery if obstructing ventricles
• Ocular infection: need screening and surgery prior to treatment, as inflammatory reaction can be blinding! - 14taenia control and prevention 7• Basically want to prevent eggs entering into environment
• Health education
• Understand transmission and importance of washing food/hands
• Need to cook meat thoroughly
• Sanitation and hand hygiene
• Test sentinel animals
• Treat animals
• Test and treat human carriers of Taenia
• Avoid pig toilets! - 154 fts hydratid diseaseCaused by echinococcus
Two main species: granulosus (dog tapeworm) and multilocularis (fox)
Disease from larval stages - 167 echinococcus granulosus fts• Dog tapeworm
Causes cystic echinococcosis
Cysts may form in all tissues, but predominantly liver > lungs > other site
Cysts have a germinal layer and produce internal “daughter cysts
Symptoms due to pressure from cysts - Obstruction in liver, SOB in lungs
Can be asymptomatic until large enough to cause symptoms
May rupture w trauma/surgery - 177 e multilocularis featuresE Multilocularis
Fox tapeworm
Causes alveolar echinococcosis
Cysts may form in all tissues, but most likely lung or liver
Causes similar symptoms due to mass lesions
Risk of anaphylaxis if cyst ruptures
Cysts multilocular and can metastasise to distant sites
Much harder to treat and much worse outcomes – progressive disease without treatment - 188 life cycle echinococcus• Eggs ingested by intermediate host (sheep=granulo or rat=multiloc)
• Humans infected when they accidentally ingest eggs that were embryonated and present in feces.
• Penetrate intestinal wall and form cysts in tissues (commonly liver or lung, liver if multiloc, liver/lung if granulosus)
• Cysts contain germinal cells which produce numerous protoscolices in one cyst
• Cysts/protoscolices ingested by definitive host and attaches to intestine
• Protoscolex evaginates to become a scolex
• Scolex attaches to intestinal wall and produces proglottids
• Eggs shed in faeces - 19dx of echinococcus 2Serology (ELISA)
Imaging - US, CT, MRI, daughter cysts may be visible - 204 tx echinococcus• Medical:
• Albendazole
• Prolonged courses necessary unless some surgical intervention, especially if E. multilocularis
• Surgical:
• PAIR: Percutaneous Aspiration, Injection [with scolicide], Re-aspiration
Surgery for cysts in locations at risk of pressure effects (e.g. brain) or at risk of rupture - 214 control measures for echinococcus• Health education
• Cook food well
• Prevent dogs feeding on carcasses of intermediate hosts (careful choice of food, remove IH carcasses to prevent scavenging)
• Treating dogs in endemic areas
• Control dog population
• Hard to control for E. locularis due to hosts
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- IC2 Tropical Medicine Flashcards on L8 Helminths 2, created by Molly O'Dea on 01/09/2020.
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