Vomiting and wasting disease
Haemagglutinating encephalomyelitis virus (HEV) infection, or vomiting and wasting disease, affects young pigs. Affected pigs show depression and nervous symptoms, vomit, waste and many die. Cats, rats, mice and birds do not harbour the virus, and pigs are the only naturally susceptible species common in Australia.
The disease was first detected in Canada in 1962 and in Europe in 1969. In Australia the disease was initially confirmed in Victoria in 1978, although there is evidence that HEV may have occurred as early as 1972. The first known Queensland outbreak was in 1979.
The virus affects the brain, causing symptoms such as:
These nervous symptoms are mainly seen in piglets 5 to 14 days of age, usually with 100% mortality.
Older affected piglets are unable to suckle properly and may withdraw from the sow and vomit the milk they have taken in. Some will begin to waste away 4 to 7 days after infection, while others also show the nervous symptoms. In affected litters, over half of the vomiting piglets die of dehydration or starvation and survivors are permanently stunted.
Infected piglets may sneeze or cough as an early sign. They huddle together looking pale and listless, often with arched backs. They may also grind their teeth and have swollen, gas-filled abdomens.
If piglets show these symptoms, it is important for the cause to be fully investigated because some of these signs are also seen in Aujeszky's disease (also called pseudorabies).
|Extent of the disease||
Generally speaking, the disease is short-lived. It affects all litters farrowed during the two or three weeks after the first case. Subsequent litters are protected by antibodies in their mothers' colostrum and are not affected.
Pigs become infected when they breathe the same air as infectious pigs, and older pigs carry the virus without showing any sign of the disease. Therefore isolating infected pigs from other pigs is the first line of defence.
In herds that have never been infected with HEV, incoming breeders should not share air with sows due to farrow within the following three weeks. Pregnant sows that become infected after this time will not have enough time to build-up adequate immunity to be passed to their litters through the colostrum.
When the disease occurs in herds that run sows in paddocks, it is advisable to bring sows into the farrowing shed earlier than normal to ensure exposure to the infection and subsequent build up of colostral immunity.
There is no commercial vaccine available and it is unlikely that one will be produced as the disease is so short-lived.