Duck Virus Enteritis
(DVE, duck plague)
Duck virus enteritis (DVE) is a highly contagious disease of waterfowl caused by a herpes virus that causes internal bleeding and severe diarrhea and kills many infected birds. Reproductive impairment may also occur, causing further losses in the population. Domestic and wild ducks, geese and swans are susceptible. DVE does not infect humans.
It has been characterized as an acute disease; however, chronic or latent infections must be considered as a possibility. Susceptibility to DVE seems to vary with age, management practices and the presence of concurrent disease agents.
DVE, also known as duck plague, was first diagnosed in the western hemisphere in 1967 from a concentrated commercial duck producing area in Suffolk County, N.Y. DVE had been frequently recorded in the Netherlands where it first appeared in 1923. It has been suspected in France and China, and known to occur in Belgium and India.
The first epizootic of DVE in wild waterfowl in the U.S. occurred in January and February 1973, in the vicinity of Lake Andes National Wildlife Refuge, South Dakota. The Lake Andes epidemic struck with devastating swiftness and severity. Approximately 40% of 100,000 wintering waterfowl, mostly mallards, were lost. During the peak of the die-off, daily losses exceeded 1,000 birds.
All species of waterfowl present at Lake Andes suffered some mortality. Included were Canada geese, mallards, black ducks, pintail-mallard hybrids, American widgeon, wood ducks, American goldeneyes, redheads, common mergansers, a Muscovy duck and a Pekin duck. Birds that survived the Lake Andes epidemic have dispersed widely over North America. Blood samples taken from survivors at Lake Andes indicated that about 30% of the population were exposed to the virus. These birds are potential carriers of DVE, capable of triggering future outbreaks.
In Michigan, DVE has been reported in 1979 in Muscovy and mallard ducks.
Transmission and Development
Some scientists think DVE is usually spread by infected waterfowl that shed the virus in their droppings. It survives in water and may persist in polluted, stagnant and slow-moving pools, ponds and waterways. Waterfowl pick up the disease by drinking or swimming in polluted water or by eating contaminated food. The virus may enter susceptible birds through the mouth, nose, cloaca or breaks in the skin. Birds that are exposed but survive the disease may become carriers, which maintain the infection between outbreaks and release the virus at some future time and location.
The death rate from DVE has reached 60% of infected waterfowl in some domestic flocks. In other flocks, only a few of the infected ducks have died. DVE may occur at any season but most occur in April, May, and June. Many outbreaks are associated with extremes of weather and the breeding season and the stress these factors place on susceptible birds.
Clinical Signs and Pathology
Susceptible ducks may show signs of DVE in 3 to 7 days after they are exposed. Infected birds become listless, lose their appetites, may have a bloody discharge from the bill and vent, develop a great thirst and exhibit a watery diarrhea. Occasionally, other signs that are seen are swollen eyelids and drooping wings. Sometimes ducks are found dead without any previous clinical signs.
DVE may be diagnosed tentatively by the appearance of the gross lesions. However, positive diagnosis can only be made by virus isolation and identification.
Treatment and Control
No successful treatment for DVE has been developed.
The U.S. Fish and Wildlife Service regards DVE as a potentially devastating disease which could drastically reduce the continental waterfowl population through direct losses and impaired reproductive capability. Enlisting the support and cooperation of other state and federal agriculture and wildlife interests, it has developed a monitoring and control plan for DVE.
Control consists of attempts to thoroughly sanitize sites of outbreaks depopulating the flock (captive birds); by removing and disposing of infected carcasses; quarantining of epidemic areas; chlorinating affected waters; and disinfecting contaminated soil. Exact treatment would have to be individually tailored to the specific conditions of site, time of year, and numbers and types of species involved. As there is a national DVE monitoring system, state and federal agricultural and wildlife specialists would be called in to take charge of controlling any DVE outbreak.
DVE is highly contagious, and has produced 60% mortality in susceptible flocks of domestic waterfowl. In outbreaks among domestic ducks, egg production has dropped 25-40%. There is a heavier mortality in flocks under the stress of egg production as compared to immature breeders. Most outbreaks have occurred in commercial duck flocks in the East. Apparently, captive waterfowl in the U.S. acquire DVE from migratory waterfowl.
DVE may cause extensive losses in wild waterfowl populations, as evidenced by the Lake Andes die-off. In most cases however, a small number of wild waterfowl have been affected.
DVE is not infectious to humans.
For questions about wildlife diseases, please contact the Michigan DNR Wildlife Disease Laboratory.