A mare or mares imported from North America to Victoria are believed to be at the center of the latest outbreaks of the equine herpes virus or Equine Rhinopneumonitis virus (EHV-1) in Australia.
As the Australian Thoroughbred breeding season officially got under way on Sept. 1, at least a dozen farms were quarantined. Most are in Victoria but several in New South Wales have also been isolated.
At the latest count there are 30 confirmed cases of mares aborting foals in the latter stages of pregnancy. Infected mares can abort within five months after conception, but the majority of cases occur from the eighth to the 11th month. The NSW incidents are believed to have occurred after the movement of mares from Victoria amid the general flurry of activity in July.
Breeding authorities hope the spread has been contained by the tactics of 30-day quarantining and the awareness of breeders, which has resulted in a vast reduction in the movement of pregnant mares.
Thoroughbred Breeders Australia has recommended that wherever possible, owners keep foaling mares at home and move them and the foal later. TBA president Richard Turley suggests the increased incidence could be in part due to a more responsible reportage by breeders in the wake of protocols put in place after the 1989 outbreak.
Professor Michael Studdert of the University of Melbourne's school of veterinary science described the EHV outbreak as the worst seen in Australia.
There have been viral abortion epidemics of similar scope in 1989, 1994 and 2000 but with less farms effected, particularly in the latter two occurrences.
Professor Studdert and his university team are responsible for the creation of an EHV-1 vaccine in 1996. He rates the vaccine, developed from a killed virus, as effective in 80 per cent of cases. No commercially available treatment can provide total protection.
Foals and yearlings can develop the respiratory form of the herpes virus. Older horses can become infected but these are more likely to be carriers and not show any signs of the disease. The symptoms are mild fever, coughing, and a nasal discharge.
It remains dormant in the system of and can be activated in mares with a 'viral awakening' after they begin breeding. She could also lose her foetus anywhere within seven months or as little two weeks after contracting the virus.
The EVH outbreaks played in the background as Australia had its first brush with the West Nile Virus.
Canadian standardbred pacer Astreos was believed to have been infected by mosquito bite before being transported to Australia. He displayed symptoms associated with the disease five days after his arrival at the Eastern Creek Quarantine Center, west of Sydney.
Samples subsequently sent to the Canadian Department of Agriculture laboratories and Australia's main Animal Heath Laboratory at Geelong, confirmed the presence of WNV. As the Little Brown Jug winner had recovered and the virus is non-transferable, except by Culex spp mosquitoes, he and almost 50 Thoroughbred shuttle stallions were released Aug 30.