Montse Torremorell, Marie Culhane, Gustavo Lopez, Chong Li
Influenza, aka flu, is a frustrating disease caused by influenza A viruses. Pigs with the flu may cough, sneeze, and get pneumonia. Many piglets are flu positive at weaning making their start in the nursery a bit rough, to say the least.
Control of flu can be complicated. Different viruses can be found in herds at the same time, a finding that is called co-circulation. In addition to having co-circulating viruses, additional problems come up when the viruses keep changing, or new viruses are introduced.
The current vaccines may not always protect well against new viruses. Even if the vaccines do work well in the sows, the maternal antibodies that the piglets have may wane when they are needed the most, and there may be management practices that help spread infections in breeding herds, especially in the farrowing rooms.
But none of these factors should stop us from trying to improve flu control! After all, flu is costly to producers, a main driver for antibiotic use, especially when other diseases such as PRRS and Mycoplasma are present, and flu can infect people too.
Silent spreaders of flu Our group has focused on understanding flu infections in piglets before weaning. Piglets are born “flu-free;” but in herds that have flu positive sows and gilts, many of the piglets born become infected soon after they come out and many more pigs are weaned flu positive. Piglets may be infected but may not show any signs of disease, and as a result, are silent spreaders of flu. Weaning a flu-negative pig is attractive to many producers.
So, how do we go from having flu-positive pigs headed to the nursery to actually weaning flu-negative pigs? Is there a successful game plan for flu control that can help us reach that goal?
Recent studies at the University of Minnesota have shown that having strict internal biosecurity practices during the pre-weaning period may not be enough to fully prevent the direct transmission and spread of flu by limiting direct contact between pigs.
Even when trying to minimize pig movement after processing by not using nurse sows and changing gloves when handling pigs of different litters, these changes were not enough to completely prevent flu transmission and spread.
At most, when we looked at non-vaccinated farms with a high number of flu-positive pigs at the start of the project, we saw that the transmission was delayed and there were sometimes fewer flu-positive pigs at weaning.
Strict biosecurity and vaccinations We then wanted to see what happens if similar strict internal biosecurity practices are implemented in herds that do vaccinate sows. Vaccinations and good immunity in the sows usually help protect the piglets from infection and severe disease. If vaccinations were combined with strict internal biosecurity practices, we believed that this would help decrease exposure of flu to piglets.
And YES, when we combined them, we did find that pigs were more likely to be weaned flu-negative. Indeed, we observed this in three of five farms, and in another farm there was a significant decrease in flu prevalence. These are encouraging results that need to be further explored by repeating the studies in more farms.
Another interesting observation from our research is that we realized just how much indirect transmission of flu can occur in the pre-weaning period when pigs are allowed to having contact with contaminated clothing, tools, or people, all of which can act as fomites, that is objects that have flu on their surfaces.
Flu can be found on the hands and coveralls of workers after handling infected pigs, especially when pigs are picked up for vaccination and weaning. Flu can also be found on the surfaces of the carts, tools, and instruments used to move and handle pigs. At the very least, we need to consider protocols that promote hand washing or changing disposable gloves frequently and even changing coveralls after vaccination and loadout of pigs at weaning.
The next time you start thinking about tackling flu in piglets, and that time should be now, please consider a game plan, or farm plan, that combines of sow vaccination and protocols that enhance internal biosecurity procedures.
Montse Torremorell and Marie Culhane are both professors in the veterinary population medicine department; Gustavo Lopez and Chong Li are graduate research assistants, all with the University of Minnesota.
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