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

PlanariansFree-living Flatworms

Dugesia sp., Marine Flatworms, Bipalium sp.

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)

Adult Worms

Ovum

Miracidium

Snail & Redia

Cercaria & Metacercaria

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 = break the life cycle

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 = 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 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?

Contrast the life cycles, ecology, and diagnosis of the 3 liver flukes of ruminants we have discussed.

In-Class Discussion