PRRS: The "almost" global swine disease

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PRRS: The "almost" global swine disease

With the exception of Brazil, unfortunately any country with a relevant pig census is infected by the Porcine Reproductive and Respiratory Syndrome.

Nowadays, in the worldwide pork industry there are large numbers of movements between countries or continents. In Europe for instance, one piglet can be born in Denmark, be reared in Poland and go to the slaughterhouse in Germany, and these movements facilitate the spread of disease.

 

Although breeder suppliers, genetic companies, producers and veterinarians have implemented biosecurity measures to prevent the spread of the disease, the reality is quite different because the PRRS virus is present today in 4 continents, with Oceania remaining free of the disease. The earliest evidence of PRRS virus comes from retrospective serological studies; antibodies were detected in serum as early as 1979 (Canada), since then the disease has spread very quickly.

Where and when did the PRRS virus first appear? Curiously, we are facing a disease caused by one virus with two different strains (genotypes) that appeared almost simultaneously on two different continents. The explanation behind this phenomenon is unclear. Two genotypes have been identified (type 1 or European, and type 2 or North-American); type 1 is the predominant genotype in Europe while type 2 is the most prevalent in America and Asia. Within type 1, at least 4 different subtypes have been reported; subtype I is predominant in Western Europe whereas subtypes II, III and IV have been isolated only in countries to the East of Poland. Regarding type 2, two clades have been described.

Nevertheless, both type 1 and 2 are disseminated worldwide; they can be found in almost all pig-producing countries, with the exception of Australia, New Zealand, Scandinavia and some South American countries that are PRRS virus-free.

 

The highly-pathogenic PRRS virus which emerged in China belongs to type 2. It spread rapidly throughout Asia. In a region where more than 50% of the global swine population is concentrated, this is crucial. In the summer of 2006 China, Vietnam, the Philippines and Thailand were affected and continuously re-infected by the atypical highly virulent strains of Porcine Reproductive and Respiratory Syndrome. The map below shows the development and spread of outbreaks to the rest of the affected countries in South East Asia. The colour scale shows the number of outbreaks by year and region.

 

In an ultra-connected world, in general (with some exceptions) we must acknowledge that as regards PRRS status, there are no commercial barriers between either countries or areas. Why not, if everyone agrees that PRRS is the most economically important viral disease worldwide for the swine industry?

Here there are some open and difficult questions that come to mind…
Does it make sense to limit movements between areas, countries, companies, etc?
Could we do that from a realistic point of view?
Are the professionals willing to do that?
How crucial is PRRS´ epidemiology among countries?

 
The global swine industry is starting to answer these questions.