JPC SYSTEMIC PATHOLOGY

DIGESTIVE SYSTEM

October 2024

D-V10

 

SIGNALMENT (JPC# 3071894): Muscovy duck 

 

HISTORY: This duck was one of 2 birds to die from a total of 75 ducks, and no clinical history was given.

 

HISTOPATHOLOGIC DESCRIPTION: Liver: Multifocally and randomly affecting 50% of the liver, there are variably sized foci of lytic necrosis characterized by a loss of normal hepatic architecture with discontinuity of hepatic cords, replaced by aggregates of eosinophilic cellular and karyorrhectic debris. Within these foci, remaining identifiable hepatocytes are shrunken with hypereosinophilic cytoplasm and a pyknotic nucleus (necrotic). Adjacent to these foci, hepatocytes are occasionally individualized, and are often swollen with either finely vacuolated, lacy cytoplasm (glycogen-type vacuolar change) or few large, discrete, clear, cytoplasmic vacuoles that displace the nucleus (lipid-type vacuolar change). Adjacent to areas of degeneration and necrosis, numerous hepatocytes and rare biliary epithelial cells contain a single, round, 3-8 µm diameter, eosinophilic, intranuclear viral inclusion body surrounded by a clear halo that marginates the chromatin. Multifocally, there are increased biliary ductule profiles (ductular reaction). Multifocally within periportal areas, there are few lymphocytes and plasma cells.

 

MORPHOLOGIC DIAGNOSIS: Liver: Hepatocellular necrosis, acute, multifocal, random, moderate, with hepatocellular degeneration, ductular reaction, and numerous hepatocellular and bile duct epithelial intranuclear viral inclusions, Muscovy duck (Cairina moschata), avian.

 

ETIOLOGIC DIAGNOSIS: Alphaherpesviral hepatitis 

 

CAUSE: Anatid herpesvirus 1 (Duck enteritis virus or duck plague virus)

 

CONDITION: Duck viral enteritis 

 

CONDITION SYNONYM: Duck plague

 

GENERAL DISCUSSION:

• Anatid herpesvirus is an enveloped icosahedral nucleocapsid, 150nm, dsDNA alphaherpesvirus that replicates within the host nucleus
• An acute, contagious disease of wild and domestic anseriforms (ducks, geese, swans)
• Causes sudden death and high mortality; characterized by vascular damage, tissue hemorrhages, GI mucosal eruptions and bleeding, necrosis of lymphoid organs, and degenerative changes in parenchymatous organs 
• Horizontally transmitted by direct contact or via contact with contaminated environment; vertical transmission only seen experimentally; wild ducks have demonstrated a carrier state with shedding under stress
• Worldwide, with the exception of Australia; causes significant outbreaks with up to 100% mortality rates among wild and domestic flocks; disease is frequent in captive waterfowl and infrequent in wild waterfowl
• Members of family Anatidae are natural hosts; susceptibility varies, mostly in adults; blue-winged teal and Muscovy ducks are most susceptible, pintail duck is least susceptible
• Most outbreaks occur from spring to early summer (breeding or nesting)
• This is an OIE List B reportable disease; not USDA reportable

 

PATHOGENESIS:

• Ingestion > viral replication in GI mucosal epithelial cells (especially esophagus) > epithelial degeneration and necrosis (enteritis) > viremia > infection of endothelial cells in various organs > vasculitis > necrosis and hemorrhage
• Destroys T and B lymphocytes in GALT, spleen, thymus, and bursa of Fabricius
• Secondary bacterial infections are common

 

TYPICAL CLINICAL FINDINGS:

• Peracute: Sudden death without clinical signs
• Acute: Polydipsia, weakness, photophobia, nasal discharge, lacrimation, anorexia, cyanosis, greenish-watery diarrhea, convulsions, tremors
• Sudden drop in egg production
• Prolonged illness in mature birds

 

TYPICAL GROSS FINDINGS:

• Hemorrhage at multiple sites (liver, GI tract, heart, pericardium, and ovary), with free blood in intestinal tract and body cavities
• Hemorrhage or necrosis of GALT in the intestine is characteristic and classic; hemorrhagic button-like ulcers in geese and annular band necrosis in ducks; pseudomembranous plaques at esophageal-proventricular junction and cloaca (this with GALT necrosis is almost pathognomonic)
• Severe enteritis; lesions begin as hemorrhages, then become elevated crusted plaques, finally resulting in coalescing, large areas of ulceration covered by diphtheritic membranes; similar crusting plaques are found in the esophagus, ceca, rectum, cloaca, and bursa of Fabricius
• Petechia, hemorrhage, and necrosis in lymphoid organs (spleen, thymus, bursa of Fabricius), liver, pancreas, lungs, kidney, and heart 
• Edema in the cervical region

 

TYPICAL LIGHT MICROSCOPIC FINDINGS:

• Hemorrhage and necrosis in affected organs
• Eosinophilic intranuclear viral inclusion bodies in hepatocytes and the epithelium of bile ducts, gastrointestinal epithelial cells (most notable in epithelial cells at esophageal/proventricular junction), lymphoid tissue, Harderian gland, and conjunctiva
• Intestinal mucosal sloughing with hemorrhage and luminal debris
• Severe lymphoid depletion in the bursa of Fabricius

 

ULTRASTRUCTURAL FINDINGS:

• 100 nm (nonenveloped) to 200 nm (enveloped) icosahedral virions
• Virions assembled in the nucleus become enveloped as they bud from the nuclear membrane

 

ADDITIONAL DIAGNOSTIC TESTS: 

 

DIFFERENTIAL DIAGNOSIS:

Hemorrhagic and necrotic lesions in anseriforms:

• Fowl cholera (Pasteurella multocida): Other species of birds affected; no inclusions 
• Riemerella anatipestifer: Fibrinous polyserositis, lymphoid necrosis
• Duck viral hepatitis (Picornaviridae, enterovirus): Usually only in ducklings <4 weeks of age; enlarged liver with multifocal hemorrhage
• Coccidiosis (Eimeria sp., Tyzzeria sp., and Wenyonella sp.) (D-P01, U-P06): Fibrinonecrotic and hemorrhagic enteritis
• Newcastle Disease (Paramyxoviridae, rubulavirus) (N-V10): Other species of birds affected (infrequent in anseriforms); prominent nervous system signs and lesions 
• Avian influenza (Orthomyxoviridae, influenzavirus) (D-V25): Other species of birds affected (infrequent in anseriforms); virus isolation 
• Goose herpesvirus: Similar to anatid herpesvirus-1

Intranuclear inclusions in hepatocytes of ducks:

• Lead 
• Anatid adenovirus-2

 

COMPARATIVE PATHOLOGY: 

Selected other significant alphaherpesviruses:

• Gallid herpesvirus 1 – Avian infectious laryngotracheitis (P-V11)
• Gallid herpesvirus 2 – Marek's disease (formerly classified as a gamma herpesvirus) (N-V08)

• Psittacid herpesvirus – Pacheco’s disease (D-V13, H-V03)

• Bovine herpesvirus 1 – Infectious bovine rhinotracheitis (R-V02)
• Bovine herpesvirus 2 – Bovine mammillitis/pseudo-lumpy skin disease
• Bovine herpesvirus 5 – Bovine herpes meningoencephalitis
• Porcine herpesvirus 1 – Pseudorabies/Aujeszky’s Disease (E-V01, N-V07)
• Equine herpesvirus 1 – Abortion, myeloencephalitis, rhinopneumonitis (P-V10, R-V01)
• Equine herpesvirus 3 – Equine coital exanthema
• Equine herpesvirus 4 – Equine rhinopneumonitis
• Canine herpesvirus 1 (U-V03)
• Feline herpesvirus 1 – Feline viral rhinotracheitis (P-V09)
• Macacine herpesvirus 1 – B virus of macaques; lethal in humans
• Saimiriine herpesvirus 1 – Herpes tamarinus/Herpes T of squirrel monkeys; lethal in owl monkeys (D-V14)
• Human herpesvirus 1 & 2 – Herpes simplex; lethal in owl monkeys and other new world monkeys

 

REFERENCES:

1. Bennett BT, Abee CR, Henrickson R. Nonhuman Primates in Biomedical Research: Diseases. San Diego, CA: Academic Press, Inc.; 1998:5-16.
2. Caswell JL, Williams KJ. Respiratory system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 2. 6th ed. St. Louis, MO: Elsevier; 2016:537-538.
3. Fenton HF, McManamon R, Howerth EW. Anseriformes, Ciconiiformes, Charadriiformes, and Gruiformes. In: Terio KA, McAloose D, St. Leger J, ed. Pathology of Wildlife and Zoo Animals, Cambridge, MA Academic Press; 2018: 707-709.
4. Mauldin EA, Peters-Kennedy J. Integumentary system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 1. 6th ed. St. Louis, MO: Elsevier; 2016:625-627.
5. Ojkic D, Sellers H. Viral diseases. In: Boulianne M, ed. Avian Disease Manual. 8th ed. Jacksonville, FL: American Association of Avian Pathologists, Inc; 2019:42-44. 
6. Schlafer DH, Foster RA. Female genital system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 3. 6th ed. St. Louis, MO: Elsevier; 2016:432-433.

 

 

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