Rates of swine influenza in pig herds is much higher than previously thought, according recently published research.


Findings from The Royal Vet College and COSI Consortium discovered out of 20 pigs on each of the 146 farrow-to-finish farms involved in the study, at least one pig tested positive on 59% of the farms.

Researchers also discovered most common strain of swine flu in England, H1N1, was similar to avian flu.

This prevalence of swine flu was much higher than expected, explained RVC’s Barbara Weiland. “This highlights the importance of sub clinical infection, and the fact that swine influenza virus is a significant production disease that has been underestimated in the past.”

Those farms that tested positive for the swine influenza virus were also more likely to be infected with other pig pathogens, and had poor respiratory scores in slaughterhouse and monitoring programmes. And while the infection may not appear to have much effect on the herd, it does, said Merial vet advisor Ricardo Neto.

“The disease has significant economic effects and in some cases can be quite disastrous. It causes fever, apathy, anorexia and respiratory signs such as dyspnoea [shortness of breath] and sneezing, which affect both welfare and productivity. In sows it can affect return to oestrus, cause abortion, increase the number of still born piglets and decrease lactation. Therefore, there is a strong economic case for considering preventative treatment.”

Steve Youngs, who recently experienced an outbreak of swine influenza, reported that about 10% of sows on his farm aborted and there was a noticeable increase in weak and still born piglets. The farrowing rate on his farm reduced by about 10% from 85% down to 75%. Apart from the cost of treatment, the vet estimated that it cost him around 20 pence a kilo deadweight.