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31 Cards in this Set
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Major trematode genera of Cattle, Sheep and cervids |
Fasciola Dirocoelium (liver fluke cattle and sheep) Fascioloides (liver fluke of cervids, cattle and sheep dead end host) Paramphistomum (rumen fluke of cattle and sheep) |
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Fasciola hepatica overview |
Liver fluke - globally most important trematode of livestock - world wide Grey brown "leaf" shaped fluke in bile ducts of ruminants Can infect many species - cattle, sheep, goats - can be zoonotic **Fasciola gigantica: closely related fluke in tropical regions |
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Fasciola hepatica life cycle |
Adult worms inside definitive host -> eggs Eggs go to environment through biliary system Eggs hatch to produce miracidium - (very susceptible to desiccation; w/i days) Intermediate host: Snails (Lymnea or Galba) - infection by penetration ->Sporocyst -> Redia -> Cercaria Cercaria passes out into environment -> Metacercaria (on vegetation) - is infective stage for definitive host, can survive on pasture for months (years?) Infection by ingestion into definite host (cattle) |
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Intermediate host of fasciola hepatica |
Lymnea species of amphibious snail (also called Galba) Individual species depend on geographic region (L.humilis in N Am; L truncatula in Europe) Fasciola infection occurs where there is suitable snail habitat: muddy areas, slow moving shallow water, ditches, edges of ponds and streams |
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Fasciola hepatica Infection and development in intermediate host |
Time for development from Miracidium to Metacercaria is minimum of 6 weeks, but can take several months in cooler conditions - min temp of 10C needed for both snail breeding and parasite development Miarcidium (hatches from egg) Inside snail: ->Sporocyst -> Redia Enters environment ->Cercaria ->Encysts as metaceraria **two rounds of asexual repro in intermediate host: single marcidium can result in up to 600 cercaria |
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Fasciola hepatica Infection and development in definite host |
*Sexual reproduction Metecercaria ingested from herbage and hatch in intestine of host - juvenile flukes migrate through peritoneal cavity, penetrate liver capsule and tunnel through liver parenchyma, eventually reaching major bile ducts Prepatent period: - from ingestion of adult metacercia to mature adult fluke in bile ducts is 10-12 weeks Longevity of adult fluke: sheep: several years Cattle: up to a year |
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Pathogenesis and clinical syndromes of fasciola hepatica |
Sheep Acute and chronic fasciolosis - depends on number of metacercaria infection - >2000 = acute - < 1000= chronic Cattle Chronic fasciolosis only - sub-clinical infection more common than overt clinical disase - production loss significant in N Am |
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Acute Fasciolosis |
Sheep only Caused by: migration of juvenile flukes (occurs in sheep not cattle) Results in: liver damage and hemorrhage Manifests as: - sudden death - weak animals with pale mucous membranes - dyspnea - palpable liver - ascites - abdominal pain When: large numbers of juveniles migrating |
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Chronic Fasciolosis |
Sheep and Cattle Caused by: adult flukes feeding in bile ducts Results in: anemia, hypoalbuminemia, cholangitis, fibrotic liver/bile ducts ("pipestem leaver" Manifests as: progressive loss of condition, emaciation, pale mucous membranes, submandibular edema ("bottle jaw"), ascites Subclinical: - productivity losses - fertility problems - reduced weight growth in lambs/calves When: 4-5 months post-ingestion of several hundre metacercaria |
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Diagnosis of fasciola hepatica |
Sheep: - clinical signs/seasonal occurrence - PM/identification of flukes - eggs in feces (not present in acute fascioliasis; pre-patent infection) - eggs in feces can also be intermittent in patent infections Bovine: - clinical signs - eggs in feces; presence variable - elevated liver enzymes: glutamate dehydrogenase (early infection); beta glutamyl transpeptidase (chronic elevation) (ELISA serum or milk; Europe) |
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Fecal examination for fasciola hepatica eggs |
Large brown eggs with operculum 130-150µm by 63-90µm - similar to paramphistomum eggs (but these are clear) - shedding can be sporadic. important to test groups of animals and repeat tests - eggs don't float in standard flotation solutions: saturated NACl or sucrose. *can use flotation in ZnSO4 - mainly use sedimentation technique (flukefinder) |
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F Hepatica in N. America |
Not major problem in Canada, but important in US - transmission occurs where intermediate host is present (PASTURE!!) - no re-infection in feedlots Beef cattle: - negative impact on growth rates in calves taken from endemic regions Dairy cattle: Sheep: - significant clinical disease and production problems |
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Treatments for Fasciola hepatica |
Favourable areas: NW US and SE US Drugs available in N. Am (Clorsulon, Albendazole) not active against immature stages of fluke - therefore annual treatments are timed to occur when only adult flukes expected to be present based on epidemiology *this differs between regions |
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Fasciola hepatica epidemiology |
Revolves around breeding and expansion of snail populations, and development and multiplication of parasite in intermediate host 1) moisture required for snail habitat 2) temperature dependence - need mean minimum day/night temp >10C for snail breeding, parasite development in snail, egg development/hatching In north US: development of parasite in intermediate host usually occurs in summer In south US: development of parasite in intermediate host occurs in winter |
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F hepatica (and F gigantica) are foodborne zoonosis |
Mostly in rural areas of S. Am.; South and East Asia - transmission by eating contaminated raw veggies |
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Fascioloides magna overview |
Common names: - giant liver fluke - large liver fluke - deer liver fluke *Up to 8cm long Southern Alberta is one of the "hot-spots" |
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Life cycle of fascioloides magna |
Definitive host: Deer In the liver -> adults -> eggs Environment -> Eggs -> Miracidium Intermediate host (Lymnea/Galba): Infection by penetration ->Sporocyst -> Redia -> Cercaria Environment -> Cercaria -> Metacercaria (on vegetation) Enter definitive host by ingestion |
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Definitive hosts of Fascioloides Magna |
Cervids Juvenile flukes migrate through peritoneal cavity - penetrate liver capsule and tunnel through liver parenchyma to search for another fluke - become encapsulated and produce eggs - Cysts connected to bile system Prepatent period: 3 months to 1 year (or more) - flukes must meet another fluke to mature and mate Longevity of adult: > 5 years in definitive host **IF you see a black liver, it's fascioloides magna |
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F. magna life cycle |
Metacercaria on vegetation (shed by intermediate host snails) Infect cervids, produce eggs, go back to intermediate host = circle *Metacercaria can also be ingested by dead end hosts and aberrant hosts |
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Dead end and aberrant hosts of F magna |
Dead end hosts: cattle - migrating flukes become encapsulated and cyst walls surrounded by dense fibrous tissue - not connected to biliary system so infections do not become patent - play no role in transmission - infections generally well tolerated - leads to liver condemnations Aberrant hosts (sheep) - flukes cannot complete migration and continue to migrate around liver without forming cysts - causes significant tissue damage - flukes can also migrate around peritoneal cavity and to the lungs - aberrant hosts usually die within a few months of infection |
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F magna diagnosis |
Live definitive host: - detection of eggs in feces by sedimentation techniques - similar to F hepatica eggs but slightly bigger ~160µm by 95µm Dead end hosts: - usually on PM |
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F magna treatment and control |
Triclabendazole - used routinely for elk on game farms |
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F magna impact on cattle production |
No good data! - liver condemnations in endemic regions *relatively common P M finding in feedlots from cattle sourced from pastures in southern alberta and foothills - Effect on productivity and growth rates? - Control difficult (wildlife reservoir) *fence off wet/marshy areas |
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Dicrocoelium dendriticum overview |
- small liver fluke - <1cm - semi-translucent - located in bile ducts - sheep, cattle, deer, rabbits (humans) - worldwide distribution (but patchy) - well adapted to dry environments - invasive species in SE alberta |
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Dicrocoelium dendriticum life cycle |
Bizarre! 1) Embryonated eggs shed in feces 2) Eggs ingested by snail intermediate host -> Miracidia -> sporocysts -> cercariae 3) cercaria released from snail via respiratory pore in a slime ball 4) cercariae become metacercariae after being eaten by an ant **secondary intermediate host** 5) host becomes infected by ingestion of infected ants 6) adult in bile duct - metacercariae hatch in intestine and migrate up main bile duct to smaller bile duct of liver **eggs can survive for months on dry pasture |
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Intermediate hosts of dicrocoelium dendriticum |
Brown ants of genus Formica - at dusk they climb up vegetation and wait to be ingested |
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Pathogenesis of dicrocoelium dendriticum |
Very heavy burdens can occur (1000's of adults) - well tolerated in short term Over time bile ducts become fibrotic and extensive cirrhosis can occur - Can lead to productivity losses, ill thrift and fertility problems in sheep - reduces productive lifespan of ewes |
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Diagnosis of dicrocoelium dendriticum |
Detection of small, dark brown operculate eggs in feces (45 x 30µm) - contains fully developed miracidium Requires zinc sulphate flotations (high specific gravity of 1.3-1.4) |
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Paramphistomum overview |
Conical "maggot" shaped flukes of ruminants Adults in rumen and reticulum Worldwide - mainly cause issues in tropics and southern US About 1 cm long |
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Paramphistomum life cycle and pathogenesis |
Snail stages same as Fasciola (4 weeks) Aquatic snails as intermediate hosts Metacercaria are ingested and encyst in duodenum, where juveniles attach to intestinal wall and feed (6 weeks) Adults migrate to forestomachs: - PPP 7-10 weeks **Pathogenesis is due to juvenile intestinal phase of infection - attach to duodenal mucosa which causes necrosis and hemorrhage, erosion and ulceration of duodenal mucosa and edema *Adults cause little harm |
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Diagnosis of paramphistomum |
Clinical signs: - diarrhea! - anemia - hypoalbuminemia - intense thirst - anorexia Juveniles: - sometimes seen in diarrheic feces eggs in feces look like fasciola eggs but clearer **Confirmation of diagnosis on PM: juveniles and pathology in duodenum |
