Hungary has been fighting the PRRS virus. And with success. Thanks to strict policies, Hungary manages to keep this viral disease, which was long considered ineradicable, under control, certainly at regional level. What valuable lessons can be learned from the ‘Hungarian approach’ for the Dutch and Belgian pig farming industry?
In an earlier article, veterinarian István Szabó explained why he personally prefers the depop-repop method. At the same time, the veterinarian – chairman of the PRRS eradication committee in Hungary – understands that this method is experienced as very drastic by pig farmers. Fortunately, he says, there are also several other ways to get a grip on the PRRS virus, but these other methods require more time.
During his presentation at the annual MSD Animal Health symposium for veterinarians, Hungarian Szabó emphasized several times the importance of good biosecurity measures in the management of PRRS. “You have to take – and keep – both your internal and your external biosecurity to the highest level to get rid of PRRS and to prevent new infections. If you do not want to work with the depop-repop method, it is very important to build up immunity in time. For this it is necessary that you know exactly which vaccine strain or field strains you are dealing with and when they come into play. Sequence analyzes are an extremely valuable tool in this regard. In addition, it is important to find out which other diseases affect your company. Based on that knowledge, you can determine a vaccination strategy.”
In addition to the moment of vaccination, the vaccine itself also plays a major role, Szabó has discovered. “It is extremely important that you choose a stable vaccine, because a modified form of the PRRS virus is used when administering a vaccine. After all, this ensures that the immune system is provoked and the animal builds up immunity. It is important that the vaccine virus is broad enough to target as many field strains as possible, without recombining and taking on a life of its own. We have seen differences in this in Hungary. We have done many laboratory studies and it has clearly shown that a vaccine that spreads a short time after vaccination gives the least genetic variation and is therefore the most stable vaccine.”
Rarely by air
The PRRS virus is known to spread even through the air. However, in practice, according to Szabó, this turns out not to be too bad. “We have done about 3,000 blood tests in Hungary. PRRS was re-diagnosed in 40 of the 165. The majority of those infections appeared to have entered via transport, i.e. via the vehicles. In only two cases, the virus presumably entered the company through the air. That in itself is a pleasant science: after all, you have little influence on it via the air, but the transport and import of PPRS-free animals is something that you can certainly influence with good biosecurity measures.”
Reinfection or new infection?
Another important finding from the blood tests we did in Hungary is that the farms that eradicated PPRS using the depop-repop method and became re-infected were not the same strain previously found on the farm. “In all cases, these were new infections. Further questioning revealed that animals had been purchased from non-certified companies or that the virus had entered through another ‘leak’. In the case of PPRS after depop-repop, it is therefore better not to speak of reinfections, but of a new infection of the population.”
You can read more about PRRS, its diagnosis, sequence analysis and biosecurity here page.
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