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Nematoda Triploblastic Bilateral Cuticle (secreted) Longitudinal Muscles only Psuedocoelomate Dioecious Complete Digestive Tract Cylindrical body
Triploblastic Bilateral Syncytial Tegument Longitudinal & Circular Muscles Acoelomate (=> Parenchyma) Hermaphroditic = Monoecious
(Except Blood Flukes are Dioecious) Incomplete Digestive Tract
(Absent in Cestodes) Dorso-ventrally Flattened
Platyhelminthes
FlatwormsRoundworms
Platyhelminthes Groups
Class Turbellaria = Planarians Class Monogenea = Mongeneans Class Trematoda = Flukes Subclass Aspidogastrea Subclass Digenea
Class Cestoda = Tapeworms
MonogeneansFlukes: Ecto-Parasites of Fish
Group of Veterinary Importance Gyrodactylus sp., Polystomum sp., Benedinia sp.
Aspidogastrean TrematodesEcto-Parasites of Molluscs, Fish, & Reptiles
Aspidogaster sp., Cotylogaster sp.
Digenean TrematodesFlukes: Endo-Parasites of Vertebrates
Group of Veterinary ImportanceFasciola sp., Paragonimus sp., etc.
CestodesTapeworms: Endo-Parasites of Vertebrates
Group of Veterinary ImportanceTaenia sp., Anoplocephala sp., etc.
Digenean Trematodes1. Flatworms 2. Complex Life Cycles
a. digenea ==> (di = two), (genea = beginnings) b. Sexual Reproduction => Adult worms in
definitive host c. Asexual Reproduction => Larval worms in
snail host
Digenean TrematodesMorphology
1. General Flatworm Characteristics 2. Suckers and/or holdfast organs3. Incomplete gut4. Reproductive organs
(testes, ovary, vitellaria)
Digenean TrematodesComplex Life Cycle
1. Definitive Hosta. Adult Worms (Sexual Reproduction)
2. Environmenta. Ovum (Distribution)b. Miracidium (Distribution)
3. Molluscan 1st Intermediate Host a. Sporocysts and/or Rediae (Asexual Reproduction)
4. Environmenta. Cercaria (Distribution)
5. 2nd Intermediate Host or Environmenta. Metacercaria (Transmission)
Digenean Groups
Large AnimalsLiver Flukes or Bile Duct FlukesFasciola (ruminants)Fascioloides (ruminants)Dicrocoelium (ruminants)
Intestinal FlukeAcanthatrium (bat/horse)
Small AnimalsBile & Pancreatic Duct FlukesPlatynosomum (cats)Eurytrema (cats)
Lung FlukeParagonimus (dogs, cats)
Intestinal FlukeNanophyetus (dogs)
Blood FlukeHeterobilharzia (dogs)
In general, flukes are grouped by location in definitive host.
Fasciola hepatica
Large, leaf-like, liver/bile duct flukes Small anterior suckers Dendritic Intestines, Testes & Ovary
Life Cycle -- aquatic Definitive Hosts -- Cattle, Sheep, Goats & Camelids Ova develop & hatch in water Miracidia penetrate snail host Snail 1st Intermediate Host
Pond / Puddle snails (Sporocysts and Redia) Cercaria 2nd Intermediate Host (= Environment)
Aquatic or Semi-aquatic Vegetation (metacercaria) (survive 6-10 months) Young & Adult Flukes
Young flukes migrate from intestine via peritoneal cavity to the liver Young flukes migrate throughout liver parenchyma (= Acute DZ) Adult worms live in the bile ducts ( Chronic DZ) Prepatent period: 2 months Entire Life Cycle: 3-6 months Longevity: up to 11 years
Geographic Distribution
Florida, Puerto Rico Gulf Coast States (LA, MS, AL,TX)
Pacific Northwest (WA, OR, CA, ID, MO, NV, UT)
Eastern Canada Not endemic in North Carolina (WHY?)
Pathology
Acute Due to migration of young flukes through liver Severe liver damage, hemorrhage, inflammation May precipitate "black disease" (clostridial infection); usually
results in sudden death, especially in sheep
Chronic Due to adults in bile ducts Loss of condition, weakness, anemia, hypoproteinemia Liver fibrosis, cholangiohepatitis Fibrosis & Stenosis of Bile Ducts, eventual calcification Results in liver condemnation
FYI only - for Path Heads
Chronic (Due to adults in bile ducts) Anemia
Hemorrhage (Blood feeding adults) Hemolysis (Proline excreted by adult worms)
Bile duct stenosis (fibrosis) Physical irritation (Worm spines, feeding, & activity) Chemical irritation (Proline excreted by adult worms)
Hypoproteinemia (=> edema) Protein Loss (Blood feeding adults) Protein Leak (fibrotic bile ducts have increased permeability) Liver dysfunction (decreased globulin / albumin production)
Diagnosis Fecal Sedimentation
Acute DZ: Negative Chronic DZ: Positive
Clinical Signs: Acute: abdominal pain, unwilling to move,
sudden death Chronic: Loss of condition, weakness, signs of
anemia, edema (bottle-jaw). Necropsy Herd History
Treatment Clorsulon (Curatrem & Ivomec Plus)
Curatrem Clorsulon @ 7mg/kg PO for cattle
Ivomec Plus Ivermectin + Clorsulon @ 1ml / 50 kg SC for cattle
Not licensed for breeding dairy cattle 8 day pre-slaughter withdrawal time
Albendazole (Valbazen Suspension PI) Cattle - 10 mg/kg Sheep - 7.5 mg/kg Goats - 10-15 mg/kg
Not licensed for breeding dairy cattle 27 day pre-slaughter withdrawal time
Control Snail Control (unrealistic)
molluscicides adequate drainage of pastures
Grazing Control Restrict access to wet areas
Strategic Drug Control Ivermectin + Clorsulon (Ivomec Plus) Early fall in Southern US
Zoonosis Human Fascioliasis
Europe, Africa, Cuba, South America Halzoun (accidental zoonosis)
Ingestion of raw liver Adult flukes attach to naso-pharynx Middle East
Fascioloides magna
Very Large, leaf-like, liver flukes Small anterior suckers Dendritic Intestines, Testes & Ovary
Life Cycle -- aquatic Definitive Hosts
Cervids (deer, elk) Ova (Prepatent period = 9 months) Miracidia Snail 1st Intermediate Host
Pond / Puddle snails (aquatic) Sporocysts and Redia
Cercaria 2nd Intermediate Host (or Environment)
Metacercaria Aqautic or Semi-aquatic Vegetation
Young & Adult Flukes Young flukes migrate through liver parenchyma before maturing in cysts with
connections to bile ducts Dead-end Hosts
Sheep, Goats, Camelids: migration of young flukes cause liver damage & death Cattle: Adult worms walled off in fibrotic cysts.
Geographic Distribution
Scattered throughout US Prevents goat & sheep production
in Minnesota & Michigan Sporadic in white-tailed deer in
North Carolina Recent Camelid infections in south-
west NC
Pathology Wild Cervids
Minor pathology, unless very,very heavy infection (118 flukes from 1 deer, but not debilitated) (Pursglove et al. 1977)
Sheep, Goats, & Camelids Severe liver damage, hemorrhage, inflammation May precipitate "black disease" (clostridial infection) Usually results in sudden death
Cattle Minor damage, unless very heavy infection Liver Condemnations
Diagnosis
Wild Cervids Fecal Sedimentation Necropsy
Domestic Ruminants (non-patent) Necropsy Swampy pastures shared with wild cervids.
Treatment
Wild Cervids Clorsulon (Curatrem)
24 mg/kg Albendazole (Valbazen Suspension PI)
26 mg/kg
Domestic Ruminants No good treatment
Control
Snail Control (unrealistic) molluscicides adequate drainage of pastures
Grazing Control Restrict access to wet areas Restrict wild cervid access to pastures
Dicrocoelium dendriticum
Lancet Fluke Translucent, lancet-shaped flukes of the bile ducts. Ventral sucker in anterior half of body. Glodular Tandem Testes Posterior to the Ventral
sucker, Globular Ovary posterior to testes.
Notes Definitive Hosts & Distribution
Small Ruminants (Sheep & Goats) Variety of Hosts (cattle, camelids, rabbits, pigs, cervids, etc.) Widely Distributed around the World Northeast US & Canada
Pathology Non-pathogenic in younger animals Bile duct hyperplasia, hepatic cirrhosis Slow chronic progressive disease, cachexia (wasting). decreased productivity in older animals (ewes)
Diagnosis Edema & emaciation in older stock Ova in sedimentation
Treatment Albendazole in sheep (15-20 mg/kg), Praziquantel in llamas
Control Eradicate Ant hills
Zoonosis Yes - a few human cases
It is early November when you take a job as a large-animal vet in southern Florida. One of your first cases involves a long time shepherd that has recently begun to loose sheep. The sheep have been presenting with pale mucus membranes, lethargy, bottle-jaw, and some deaths.
In-Class Discussion
Worm differentials?
Compare & contrast each worm?
Speculate on why the long time shepherd is having issues now.
You are a large-animal vet in eastern North Carolina. An accountant, recently turned cattleman, is very concerned that he has lost much profit because of the condemnation of his cattle’s livers. He was told by the abattoir meat inspector that many of his steers had “flukey livers”.
In-Class Discussion
Worm differentials?
Contrast herd history, diagnostics, & farm visit?
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