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38 Cards in this Set
- Front
- Back
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Anatomy of a Cestode |
No mouth, no guts, no body cavity Proglottids continually produced from neck region below the scolex (sucker) Each proglottid (segment) is a hermaphrodite - become sexually mature as they pass down the strobila (e.g. Taenia) |
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How are eggs passed out in cestodes? |
Gravid proglottids packed full of eggs separate from strobila and pass out in feces - eggs then shed as proglottid disintegrates in environment = Cyclophyllidae family In Psueophyllidae, eggs not proglottids, are passed in feces |
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LIfecycle of cestodes |
Always indirect Predator-prey relationship Two or more hosts - Definitive hosts: GI tract - sexual reproduction - Intermediate host: various tissues - no reproduction or asexual reproduction |
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Eggs of Cyclophyllidae cestodes |
Hexacanth (6-hooked) embryo surrounded by two embryonic membranes Thick, dark, radially striated shell *Eggs are ingested by intermediate hosts! - travel through intestinal mucosa into blood or lymph (mammals) or body cavity (invertebrates) - then develops into metacestode |
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Metacestodes in Intermediate hosts (cyclophillidae) |
Hydatid cyst (1 egg produces many protoscolices) -> Cysticercus (single invaginated scolex, 1 egg= 1 scolex) -> Coenurus (numerous invaginated scolices) -> Cysticercoid (single evaginated scolex: invertebrate IH) -> Strobilocercus (1 egg = 1 strobilocercus) |
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Cestodes of ruminants as definitive hosts |
Moniezia benedeni (cattle) M. expansa (sheep/goats) Thysanosoma actinoides (sheep, goats, wild ruminants) Large tapeworms or small intestine! |
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Life cycle of Moniezia/Thysanosoma |
Proglottids in feces -> Egg with hexacanth larva -> Arthropod intermediate host - Moniezia use free-living oribatid mites -> develop to cysticercoid (6-16 weeks) -> Cysticercoid ingested by ruminant PPP = 5 weeks |
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Clinical signs of Moniezia |
Little effect on direct host - unthrifty (bison/muskoxen?) |
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Clinical signs of Thysanosoma |
blockage of bile/pancreatic ducts |
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Diagnosis of Moniezia and Thysanosoma |
Routine fecal flotation Proglottids in feces |
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Treatment of Moniezia and Thysanosoma |
NOT macrocyclic lactones (ivermectin) Fenbendazole (Safeguard, Panacur Albendazole |
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Important cestode in equines |
Anoplocephala perfoliata A. magna (long) Paranoplocephala mamillana (small) |
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Where does Anoplocephala perfoliata live? |
In intestine of horses - located at ileo-cecal junction = risk factor for colic Adult worms 3-8cm in length |
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Prevalence of A. perfoliata |
14-81% Higher prevalence at temperate climates |
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Lifecycle of Anoplocephala perfoliata |
very long! Live long in environment so may need to treat more than once PPP = 6-10 weeks Indirect lifecycle 1) Eggs passed in feces (will burst out of proglottid) - long-lived (months) 2) ingested by forage mite - intermediate host 3) Forms cysticercoid in mite - 8-20 weeks 4) infected mite ingested by horse 5) attaches to gut wall 6) adults at ileo-cecal junction |
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2 types of colic due to A. perfoliata
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Ileal impaction colic and Spasmodic colic - see ulceration, inflammation, diptheritic membrane at ileo-cecal valve - perforation, intussusception *Most common in weanling, yearling, young throughbreds |
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Diagnosis of A. perfoliata |
Fecal egg counts - sugar centrifugation best - variable sensitivity (11-61%) - relate poorly to infection intensities, more sensitive for A. magna Fecal PCR - multiplex Serology relates well to infection intensity ELISA test using scolex excretory-secretory antigens |
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Treatment of A. perfoliata |
Pyrantel pamoate (2x recommended doe) Praziquantel **remember the long lifecycle inside the mite (8-20weeks) so may need to treat again as they are out in the environment** |
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Taeniid lifecycle |
1) Eggs - immediately infection - eggs survival: high if cool and humid (>1 year) - low if hot and dry (<1 week) 2) Infects cattle etc - unsure of direct or intermediate host??? 3) Infects dogs - NA dogs and cat = 30% - clinical signs rare, mostly anal pruritus 4) Proglottid shedding - irregular but months to years |
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Adult vs larval stages of Taenia? |
Adult = Taenia Larva = cysticercus (single invaginated scolex) larva could also be coenurus (numerous invaginated scolices) |
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Taenia diagnosis in DH |
Flotation - eggs 25-40u, dark brown, hexacanth larvae, thick striated shell wall - false negatives Proglottids in feces - flotations may be negative if proglottids intact For dried segments - rehydrate! - single lateral pore/segment - examine eggs |
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Taenia Risk factors |
Predatory-prey cycle 1) hunting and freedom to roam 2) proximity to a farm with livestock |
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Control of Taenia |
Prevent infection (food web!) Anthelminthics in definitive hosts - Praziquantel (Droncit) - Fenbendazole |
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3 important Taeniids in production animals: |
T. saginata (cows) - zoonosis T. ovis (goats) - production loss T. solium (pigs) - zoonotic **DO NOT tend to cause problems in definitive hosts** |
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T. ovis lifecycle |
1) Eggs - immediately infective - pasture survival: 3-5 months 2) ingested by goats 3) Cysticercus - single invaginated scolex - lesions in muscles by 2 weeks 4) Dogs ingest goat meat 5) Proglottid shedding - irregular but months to hears PPP = 6-9 weeks |
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Taenia saginata lifecycle |
"beef" tapeworm - People are only definitive host 1) Eggs shed from human waste - eggs persist 6-10+ months 2) Cows ingest eggs from environment - intermediate host 3) become cysticercus bovis - 1 egg = 1 cyst - can persist 2+ years 4) humans ingest beef infected by it - live in intestine - human is definitive host - lifespan of 30-40 years PPP = 2-3 months **Reportable disease in canada! - herd quarantine, carcass condemnation etc |
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Diagnosis of Taenia saginata |
Slicing of heart, masseter, pterygoid muscles, tongue, esophagus, diaphragm Heart most frequently affected and highest cyst density |
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Control of Taenia saginata |
Control human infection and waste Also control wandering proglottids - they crawl out of the anus..... |
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Lifecycle of Taenia solium |
"pork tapeworm" Humans are definitive host 1) Humans ingest T solium eggs by fecal contamination - humans acting as intermediate host 2) Human cysticercosis OR 1) Pigs ingest T solium eggs or proglottids - pigs intermediate host 2) Porcine cysticercosis 3) humans ingest infected pork (poorly cooked) = Taeniasis |
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What is cysticercosis |
Infection by Taenia solium - most common parasitic infection of CNS in people globally Signs: - epilepsy - headaches - neurological disease = people acting as aberrant intermediate host |
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Risk factors for contracting cysticercosis (neurological signs) |
Association with people with taeniaisis (people shedding eggs) - not pigs!! Huge problem in developing nations - sporadic occurrence in NA |
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Diagnosis of T. solium |
People: 1) Taeniasis - fecals, history of tapeworm segments in feces 2) Cysticercosis- seizures/epilepsy - CDC Immunoblot (antibody) - MRI/CT (imaging) Pigs - Lingual palpation - ELISA - or similar to cows above, cut into meat |
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Prevention of T. solium |
Tx Taeniasis - targeted, not mass treatment, is preferred (exacerbate occult neurocysticercosis) Health education - very effective in Latin America, educate local leaders Pig control - prevent access to human feces - vaccination? - pig treatment is effective |
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Why do we think we can eradicate T solium? |
- Parasite requires human to complete its lifecycle - Tapeworms in humans are only source of infection for pigs - Authorities can control transmission from pigs to humans - No reservoir of infection in wildlife |
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Taenia serialis |
Canid-lagomorph (bunnies) - sylvatic cycle (wild-life) - coenurus stage in bunnies? |
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T. krabbei/T. hydatigena |
Canid-cervid Cysticercus in meat - in omentum, peritoneal cavity etc |
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How are Taenia related to immunosuppression? Which 3 Taenia does this happen with? |
Carnivores typically definitive hosts but occasionally play role of intermediate hosts - may be linked to immunosuppression T. serialis - cases of fatal cerebral coenurosis in cats = severe neurological disease T. pisiformis - hepatic cysticercosis in dogs T. crassiceps - subcutaneous cysticercosis in dogs |
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Taenia summary |
- 2 host cycle - large worms, scolex with hooks and suckers - rectangular proglottids - gravid proglottids shed in feces (or crawl out) - eggs generally fairly environmentally robust, immediately infective - larval stages: cysticercus (one), strobilocercus (elongating), coenurus (multiple), hydatid (cystic and alveolar) - canids/felids/ursids common definitive hosts - people = definitive and intermediate hosts, sometimes both for same worm (T. solium) - economic costs |
