Waterfowl Diseases:Duck Viral Enteritis

Waterfowl Diseases: Duck Viral Enteritis

Duck Viral Enteritis is not a common disease in the UK. It seems to be more prevalent in S E Asia- possibly because of the climate and environmental conditions; possibly because large flocks of ducks are kept commercially. Nevertheless, there is the odd case in the UK which causes a lot of grief. Information is hard to come by because the incidence of the disease is rare, so we thought that the information gained from last year's enquiries, and research for solutions, could be useful on the web pages.

Cases from the UK
The cases that we have been aware of in the last few years have been in Scotland, Lancashire and Eastern England. The incidence of DVE is perhaps most likely where there is a large migrant bird population, and/or large numbers of mallard. The disease tends to arrive in spring and may be associated with migrant birds. The disease is viral, and can affect, and be carried by, geese (Anser anser), ducks (Anas p.platyrhynchos) and the Muscovy duck (Cairina moschata). It also affects wildfowl.
Strangely, in the limited number of cases reported in the UK, not all of the waterfowl flock is affected. In one case the heavy ducks had high mortality, but the Call ducks and geese were all right. In another the light ducks died and the Call ducks also survived. Perhaps the unaffected birds had natural immunity, Muscovies are generally thought to be at greatest risk, and are probably an early indicator that something is wrong. Worryingly, it is reported that affected birds which survive can be carriers of the disease. In these carriers, there may be a 'cold sore' lesion under tongue (hence the term herpes virus). The sore may be intermittent; also oral swabs for testing may find the virus, but on other occasions the virus may not be found (from a sample page from Wildpro).

In a case reported from Taiwan, 50-95% of the infected ducklings died. Death occurred within 3-4 days of the first appearance of the symptoms, and survivors were stunted; some showed physical abnormalities. In the first reported case, only young ducklings were affected. Adults presumably were over the time the disease spread (Y K Liao et al., The Outbreak and Control of Duck Viral Disease in Taiwan, 1989-90, Provincial Research Institute for Animal Health, Tanssui, R.O.C on Taiwan).

Symptoms
Reported from Taiwan: Ducks lose their appetite and stand around with ruffled feathers. Watery diarrhoea is excreted. Birds become unable to stand; some have tremors of the head, neck and body. Birds fall on their side, occasionally paddle with their legs, and die with their heads drawn back.

In addition to this, other writers describe a greenish-yellow diarrhoea which is sometimes blood-stained. Birds are sensitive to light, and thirsty. They may stand at the water's edge. The bill may turn blue. Feathers around the eyes may be sticky, and the eyes stuck shut. In laying ducks, there is a marked drop in egg production. Dead birds have blood-stained feathers around the vent and blood dripping from the nostrils. Internally, there are haemorrhages throughout the body. Note that some birds may just die suddenly with no obvious external symptoms.

What can you do?
If you think it's DVE - get the vet. A post mortem at the local pathology lab with confirm initial diagnosis, but it might take several days to get a final result. In the meantime, organise how to obtain the vaccine, as this can be time consuming.

The vaccine is manufactured in Holland. So if there are no supplies in the UK, it will have to obtained by your vet through Intervet from Holland. The problem with the DVE vaccine is its availability. It has a very short shelf life, the demand is very small and unpredictable and Intervet UK cannot afford to keep it in stock in large quantities. Intervet UK recommends that vets can purchase the product direct for their clients if they wish.

The vaccine is intended for protection of healthy flocks of ducks and geese, but can be used for the vaccination of apparently healthy birds, where the disease is present, to limit further spread. Vials consist of 500 or 1000 doses of the live, freeze-dried vaccine. The vial is supplied with a reconstituting agent, and the vaccine has to be reconstituted immediately prior to use. Once the vaccine has been reconstituted it has to be used within 6 hours. The reconstituted vaccine is given by subcutaneous or intramuscular injection. Birds can be vaccinated from day old onwards where risk is high. Organisation of people and birds has to be good, however, to vaccinate all birds within the 6 hour time span.

Birds which have acquired immunity from a vaccinated parent should be re-vaccinated after maternal antibody levels have declined after 4 weeks of age or later. (That's easier said than done if the vaccine is difficult to obtain).

For further information on the use of veterinary medicines please contact your Vet or visit the website of the Veterinary Medicines Directorate www.vmd.gov.uk who are the regulatory authority for veterinary medicines in the UK.