Humans aren’t the only ones who can contract the flu.
Influenza A viruses can also affect pigs and their piglets, which is why, just like in human populations, pig populations are commonly vaccinated against the flu.
The idea behind vaccination is to create herd immunity. Herd immunity exists when a swine herd has little to no disease risk; meaning vaccine-receiving pigs are protected for a long period of time and enough pigs have been immunized (or are naturally immune) to keep unvaccinated pigs disease-free. Herd immunity helps to keep as many pigs as possible in the best possible health, resulting in lower production costs, lower pork retail prices, lower risk of flu-spread to humans and all-around healthier pigs.
Last week, University of Minnesota researchers published a new mathematical model addressing how swine producers approach vaccinating their pigs. Their publication is a unique collaboration between mathematical modelers and swine experts.
“Vaccination certainly helps control influenza A in swine,” said study co-author Montserrat Torremorell, D.V.M., Ph.D., Allen D. Leman Chair in Swine Health and Productivity and head of the Swine Disease Eradication Center at the U of M College of Veterinary Medicine. “But it’s not as effective at controlling spread as we previously thought.”
While there’s no immediate cause for alarm as swine influenza vaccines still provide protection against disease, there is significant room for improvement.
“What was surprising is that the model found current vaccination strategies don’t completely eliminate influenza … even with homologous vaccination,” said study co-author and U of M infectious disease ecologist Meggan Craft, Ph.D.
Results published in the journal PLOS ONE outline how homologous vaccines (made from the same flu virus circulating in a herd) worked to prevent flu transmission among adult swine, but not among piglets. Heterologous vaccines (made from a different, flu-fighting virus) are known from previous swine research to reduce the occurrence of flu-related symptoms, but, interestingly enough, did not prevent disease transmission among any group of swine in this study.
This information in hand, Craft and Torremorell propose a few opportunities for improving flu management strategies at the commercial swine breeding facilities modeled in this research:
- Develop new and improved vaccinations. Not all vaccines prevent disease transmission equally. Torremorell notes vaccine companies are already largely cognizant of the continuing need to develop new vaccines. This research rescores the need for a continued focus on innovation.
- Rethink vaccination timing. When a vaccination is given can matter. Targeting certain stages in a pig’s breeding cycle may help boost herd immunity.
- Target groups for vaccination. Instead of vaccinating all facility swine at once, choosing to vaccinate different groups of pigs (all adult animals, sows, piglets, etc.) could help improve herd health.
- Improve facility pig flow. Because susceptibility to the flu is influenced by a pig’s age, flu immunity, vaccination status and immunity passed down through the mother, altering the flow of a pig facility can influence how the virus is transmitted.
- Improve biosecurity to minimize the introduction of new flu viruses. From footbaths to the isolation and testing of new animals, tweaking biosecurity measures on swine farms can have a big impact.
“We hope the new understanding will help producers and veterinarians make decisions on how to vaccinate pigs and stimulate development of better vaccines,” said Torremorell. Opportunities to utilize the full spectrum of flu management tools to improve pig health exist as well, added Craft.
The flu is one of the nation’s most costly and deadly diseases capable of jumping from animals to humans and vice versa. Dedicating resources to improved pig health is a key tool in reducing the risk of flu arriving in humans by way of the farm.
Funding for this research was provided by the U of M Institute on the Environment and the U.S. Department of Agriculture.
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