Download Duck Viral Enteritis (Duck plague) Duck viral enteritis (DVE) is an

Duck Viral Enteritis
(Duck plague)
Duck viral enteritis (DVE) is an acute, highly contagious disease of
ducks, geese, and swans of all ages, characterized by sudden death,
high mortality (particularly among older ducks), and hemorrhages and
necrosis in internal organs. It has been reported in domestic and wild
waterfowl in Europe, Asia, North America, and Africa, resulting in
limited to serious economic losses on domestic duck farms and
sporadic, limited to massive die-offs in wild waterfowl .
Etiology, Epidemiology, and Transmission :
Field strains of the causative herpesvirus are antigenically similar but
vary considerably in pathogenicity. The virus is relatively sensitive to
heat and pH; lipid solvents, trypsin, and chymotrypsin inactivate it. It
causes intranuclear inclusion bodies in infected tissues and in
inoculated cell cultures. In nature, the virus is mainly transmitted from
infected to susceptible ducks by direct contact or water and is acquired
mainly by the oral route. Parenteral, intranasal, or oral administration of
infected tissues can establish experimental infection. Recovered birds
may remain carriers, serving as uncontrolled sources of the virus for
susceptible ducks .
Clinical Findings :
The incubation period is 3-7 days. Sudden high and persistent mortality
is often the first sign of the disease. Mortality varies from 5-100%
depending on the virulence of the infecting viral strain. Adult ducks
usually die in higher proportions than young ones, increasing the
economic significance of the disease. Dead males may have prolapse of
the penis. Photophobia, inappetence, extreme thirst, droopiness, ataxia,
nasal discharge, soiled vents, and watery or bloody diarrhea may be
seen. Adult ducks may die in good flesh. In contrast, ducklings
frequently show dehydration and weight loss, as well as blue beaks and
blood-stained vents. In laying flocks, egg production may drop sharply .
Lesions :
Hemorrhages in various tissues and free blood in body cavities indicate
severe damage to blood vessels throughout the body. Petechial and
ecchymotic hemorrhages on the heart (“paint brush” appearance), liver,
pancreas, mesentery, and other organs are characteristic. Specific
mucosal eruptions, found in the oral cavity, esophagus, ceca, rectum,
and cloaca, undergo progressive alterations during the course of the
disease. Macular hemorrhages initially develop into elevated, yellowish,
crusted plaques and organize into green, superficial scabs, which may
coalesce into large, patchy, diphtheritic membranes. The mucosal
lesions align parallel with the longitudinal folds in the esophagus and
with the annular bands in the intestines. All lymphoid organs are
affected; necrosis and hemorrhages are apparent. A lesion that can be
easily detected on necropsy is a clear, yellow fluid that infiltrates and
discolors the subcutaneous tissues from the thoracic inlet to the upper
third of the neck. Ruptured yolk and free blood may be found in the
abdominal cavity of laying ducks .
Diagnosis :
Presumptive diagnosis is based on disease history and lesions.
Definitive diagnosis requires laboratory work. Isolation of the virus from
liver, spleen, or kidney tissues may be attempted in various cell cultures
(preferably primary Muscovy duck embryo fibroblasts or Muscovy duck
embryo liver cultures), duck embryos, or ducklings. Inoculating the
chorioallantoic membrane of 9- to 14-day-old embryonated Muscovy
duck eggs may result in isolation of the virus, but this method is not as
sensitive as intramuscular inoculation of day-old ducklings. Muscovy
ducklings are more susceptible than White Pekin ducklings.
Neutralization with specific antiserum in these systems confirms the
identity of the virus. Fluorescent antibody test can demonstrate DVE
viral proteins, and PCR, using DVE virus-specific primers, can amplify
the viral DNA in duck tissues or inoculated cultured cells. Serologic
tests have little value in the diagnosis of acute infections .
Differential diagnoses include duck viral hepatitis, pasteurellosis,
necrotic and hemorrhagic enteritis, trauma, drake damage, and various
toxicoses. Newcastle disease, avian influenza, and fowlpox may cause
similar lesions but are rarely reported in ducks. Established cases
should be reported to the appropriate regulatory agency .
Prevention, Treatment, and Control :
There is no treatment. Contact with wild, free-flying waterfowl and direct
or indirect contact with contaminated birds or material (free-flowing
water) should be avoided. Control is effected by depopulation, removal
of birds from the infected environment, sanitation, and disinfection.
Prevention is based on maintaining susceptible birds in a disease-free
environment or immunization. A chicken-embryo-adapted, modified live
virus vaccine has been approved for use in domestic ducks, in
zoological aviaries, and by private aviculturists. A 0.5 mL dose is
administered subcutaneously or intramuscularly to domestic ducklings
>2 wk of age with a booster inoculation a year later. The vaccine is not
approved for use in wild ducks. An inactivated vaccine, which appears
to be efficacious as the modified live vaccine, has not been tested on a
large scale and is not currently licensed .