Nematoda
Triploblastic Bilateral Cuticle (secreted) Longitudinal Muscles only Psuedocoelomate Dioecious Complete Digestive Tract Cylindrical body
Platyhelminthes
Triploblastic Bilateral Syncytial Tegument Longitudinal & Circular Muscle Layers Acoelomate (=> Parenchyma) Hermaphroditic = Monoecious (Except Blood Flukes are Dioecious) Incomplete Digestive Tract (Absent in Cestodes) Dorso-ventrally Flattened
Platyhelminthes Groups
Class Turbellaria = Planarians Class Trematoda = Flukes
Subclass Subclass
Aspidogastrea Digenea
Class Monogenea = Mongeneans Class Cestoda = Tapeworms
Planarians
Free-living Flatworms
Dugesia sp., Marine Flatworms, Bipalium sp.
Aspidogastrean Trematodes Ecto-Parasites of Molluscs, Fish, & Reptiles
Aspidogaster sp., Cotylogaster sp.
Monogeneans Flukes: Ecto-Parasites of Fish
Group of Veterinary Importance
Gyrodactylus sp., Polystomum sp., Benedinia sp.
Digenean Trematodes Flukes: Endo-Parasites of Vertebrates
Group of Veterinary Importance Fasciola sp., Paragonimus sp., etc.
Cestodes Tapeworms: Endo-Parasites of Vertebrates
Group of Veterinary Importance Taenia sp., Anoplocephala sp., etc.
Digenean Trematodes 1. 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 Trematodes Morphology 1. 2. 3. 4.
General Flatworm Characteristics Suckers and/or holdfast organs Incomplete gut Reproductive organs (testes, ovary, vitellaria)
Digenean Trematodes Complex Life Cycle 1. Definitive Host a. Adult Worms (Sexual Reproduction) 2. Environment a. Ovum (Distribution) b. Miracidium (Distribution) 3. Molluscan 1st Intermediate Host a. Sporocysts and/or Rediae (Asexual Reproduction) 4. Environment a. Cercaria (Distribution) 5. 2nd Intermediate Host or Environment a. Metacercaria (Transmission)
Adult Worm & Ova
Miracidium
Snail & Redia
Cercaria & Metacercaria
Digenean Groups In general, flukes are grouped by location in definitive host.
Large Animals Liver Flukes or Bile Duct Flukes Fasciola (ruminants) Fascioloides (ruminants) Dicrocoelium (ruminants) Intestinal Fluke Lecithodendrid Fluke (bat/horse)
Small Animals Bile & Pancreatic Duct Flukes Platynosomum (cats) Eurytrema (cats) Lung Fluke
Paragonimus (dogs, cats) Intestinal Fluke Nanophyetus (dogs) Blood Fluke
Heterobilharzia (dogs)
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)
Aquatic or Semi-aquatic Vegetation (metacercaria)
Cercaria 2nd Intermediate Host (= Environment) Young & Adult Flukes
Young flukes migrate from intestine via peritoneal cavity to the liver Young flukes migrate throughout liver parenchyma (= Acute DZ) before maturing in 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 Stenosis & Calcification of Bile Ducts Results in liver condemnation
Pathogenesis
Chronic (Due to adults in bile ducts)
Anemia
Bile duct stenosis (fibrosis)
Hemorrhage (Blood feeding adults) Hemolysis (Proline excreted by adult worms) 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
Clinical Signs:
Acute: Negative Chronic: Positive 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
Ivomec Plus
Clorsulon @ 7mg/kg PO for cattle
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 = break the life cycle
Control
Snail Control (unrealistic)
Grazing Control
molluscicides adequate drainage of pastures 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
Ova (Prepatent period = 9 months) Miracidia Snail 1st Intermediate Host
Metacercaria Aqautic or Semi-aquatic Vegetation
Young & Adult Flukes
Pond / Puddle snails (aquatic) Sporocysts and Redia
Cercaria 2nd Intermediate Host (or Environment)
Cervids (deer, elk)
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 southwest NC
Pathology
Wild Cervids
Sheep, Goats, & Camelids
Minor pathology, unless very heavy infection
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)
Albendazole (Valbazen Suspension PI)
24 mg/kg 26 mg/kg
Domestic Ruminants
No good treatment
Control = break the life cycle
Control Snail Control (unrealistic)
molluscicides adequate drainage of pastures
Grazing Control
Restrict access to wet areas Restrict wild cervid access to pastures
Zoonosis
NONE
Dicrocoelium dendriticum
Lancet Fluke Translucent, lancet-shaped bile duct flukes. Ventral sucker in anterior half of body. Glodular Tandem Testes Posterior to the Ventral sucker, Globular Ovary posterior to testes.
Notes
Definitive Hosts & Distribution
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
Albendazole in sheep
pigs, cervids, etc.)
Pathology
Small Ruminants (Sheep & Goats) Variety of Hosts (cattle, camelids, rabbits, Widely Distributed around the World Northeast US & Canada
Treatment Control
(15-20 mg/kg),
Eradicate Ant hills
Yes - a few human cases
Zoonosis
Praziquantel in llamas
In-Class Discussion 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 You’re 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
Contrast the life cycles, ecology, and diagnosis of the 3 liver flukes of ruminants we have discussed.
