into the respiratory tract, says Annelies Michiels, technical service manager at animal health company Hipra. Flu plus M. hyo will therefore have a much more profound effect on vital- ity and technical results. And flu plus App and PRRSv or M. hyo will create a respiratory disease complex causing a dip in performance at any time of the year.
Symptoms and reproduction problems Influenza can be chronic or acute. It is often chronic on a pig farm, with the piglet houses being the main home for the vi- rus. In that case, virus is then permanently present at the farm and will produce clinical signs to a certain degree. Reduced vitality of animals, sometimes fever, coughing and reproduc- tive problems are clinical signs that return regularly. The virus, however, can also come in a more acute form. Then pigs dis- play fever, coughing, heavy breathing, reduced appetite and general depression. Influenza can also lead to reproductive problems. That can occur in various forms, like returns-to-service, abortions (after day 35 post-insemination) or early births, as is also known with PRRS. Michiels says that it’s predominantly the fever that will affect unborn piglets. Even the pandemic form, which has emerged since 2009, could be the onset of fertility issues.
Transfer and prevention The most effective type of virus transfer takes place during animal-to-animal contact, more specifically nose-to-nose contact. That’s why it is very useful to review management practices in both the lactation area as well as grower pig house. Especially when animals are mixed, animal disease can be spread. But also when piglets are being processed it is vital to work hygienically to prevent virus transmission. Ideally, farm staff will change gloves between each litter. In addition,
the virus can also spread through pig house air, in minuscule droplets. Airborne transmission is not as smooth as with PRRSv or M. hyo. Nevertheless spread is possible for distances up to possibly 4 m, says Michiels – even without fans. The biggest risk for bringing the virus into the pig house is when new gilts are introduced. By limiting the number of in- troduction instances and by strictly applying quarantine and adaptation regulations, the impact of the introduction can be limited. For prevention it is therefore essential to leave out all actions that could potentially stimulate virus transfer. Those are characterised in the Box. A good separation between sow and piglet house is very important to block virus transfer. That should be followed by strictly separating age groups on a sow farm. In addition, working under the all-in, all-out principle is ideal.
A nose swab is taken to check for the presence of influenza viruses.
How can influenza be prevented?
It is possible to reduce the impact of influenza through good management. Some tips: • Internal farm hygiene should be optimal; • New pigs should be vaccinated and introduced after six weeks’ quarantine only; • Mixing pigs should be limited and only happen 24 hours after birth; • Sows should be vaccinated properly, depending on the virus strains available; • In the lactation house, proper manual hygiene should be applied between pro- cessing different litters;
• It is unwise to mix age groups in the grower pig house; • All-in, all-out is the preferred strategy; • A good climate is essential – at the transfer from grower to finisher house, the pens should be warm and dry;
• The presence of other pathogens should be limited. ▶ PIG PROGRESS | Volume 37, No. 10, 2021 17
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