A critical study carried out by Murdoch’s College of Veterinary Medicine has found evidence that more than 40 per cent of Western Australian free-range pigs have been exposed to the Influenza A virus at some stage during their lives.

Veterinary student Isabelle Campbell’s 18-month research into free-range piggeries found that a high proportion of pigs in WA have been infected with Influenza A virus (IAV). This result is comparable to other parts of the world.

The pork industry is of significant importance to the Western Australian economy and brings an estimated 1,700 jobs to the State.

The presence of flu virus strains in commercial pigs in WA has never been officially recognised, and Ms Campbell’s research is the first reported study of its kind in Australia.

Risk of transmission from birds to pigs

“Free-range piggeries are at a greater risk of Influenza A virus exposure, because the animals roam and can have contact with wild birds,” Ms Campbell said. “As we know, some wild birds are the natural carrier of Influenza A strains. There have been many reports of wild birds transmitting the virus to pigs.”

When pigs are infected with multiple viruses simultaneously, new Influenza A strains can be created – which is what happened in 2009 when a novel strain of the H1N1 strain killed 75,400 people worldwide, according to the Centre for Disease Control.

Ms Campbell started her research in response to commercial piggery operators expressing concerns about how the IAV, and its variations, could affect the health of their animals and their industry.

The research project was overseen by Murdoch Senior Lecturer in Production Animal Health Dr Michael Laurence and Portec Veterinary Services’ Dr Vanessa Morris.

The Australian pig industry breeds more than 1.3 million animals per year, with 11 per cent of those in WA, concentrated mainly in the southwest region of the State. However, the IAV has historically been considered ‘exotic’, or rare, in this region of the world.

Virus could trigger economic losses

“Influenza A is a common cause of respiratory disease and economic losses in the free-range pig industry,” Ms Campbell said. “It causes flu-like symptoms in pigs – including fever, discharge from the eyes and nose, coughing, lethargy and anorexia.

“These symptoms can persist for up to seven days, at the end of which the majority, if not all, of the herd have become infected.”

Although the mortality rate is often low and the duration of disease is short, it increases the risk of outbreaks of more severe respiratory disease and higher death rates.

Treating pigs infected with the flu is costly for commercial operations, and leads to reduced weight gains, triggering further economic losses.

Ms Campbell says official recognition of IAV could lead to the development of a vaccine to help farmers protect their herds and livelihoods.

She will present her findings, which includes the positive detection of strains of the IAV in 41.9 per cent of cases tested, at the Annual Pig Vet Conference in Glenelg, South Australia from October 17-19.