Eradication of porcine reproductive and respiratory syndrome virus (PRRSV) from the pig population of Hungary started in 2014 on the basis of the territorial principle. In order to reach this goal it was crucial to render each fattening unit free of this disease, since fattening units play a significant role in spreading the virus all over the country. In 2015, 188 out of 307 large-scale fattening farms (61.2%) kept PRRS-positive animals. The main source of infection of these farms was the import of PRRS-infected fattening pigs. The following methods were used during the eradication from 2017: (1) Only pigs coming from PRRS-free farms were allowed to be used for fattening in Hungary; (2) Quarantine of all herds for 60 days; (3) PCR test for PRRS 48 hours after the arrival of the prefattening animals; (4) Serological test for PRRS at the end of the quarantine period. If any diagnostic test gave even one positive result and the result was confirmed by another test, the stock had to be sold for slaughter within 15 days or placed outside Hungary, so that the infected stock would not compromise the PRRS status of that area. PRRSV eradication on large-scale fattening units applying all-in/all-out operation was relatively simple, using the depopulation-repopulation method. On permanently operating farms, the infected herd was sold from time to time, without having to be repopulated until the last delivery. After cleaning, disinfection and restocking, the repopulation was done with PRRS-free animals. As the eradication progressed over the years, a ban on the import of infected fattening pigs was imposed. As a consequence of these measures, by the end of 2018, Hungarian large-scale fattening farms became free of PRRS. Maintaining the national-level PRRS-free status of large-scale pig fattening units contributes to eliminating a significant cost factor from the Hungarian pork production industry, and opens the way for a significant reduction in antibiotic consumption as well.

Porcine reproductive and respiratory syndrome (PRRS) causes significant losses to the swine industry worldwide, which leads to launching eradication programmes. The PRRS eradication programme in Hungary is based on the territorial principle, and it is obligatory for each swine farm irrespective of the number of animals kept there. Hungary has an exceptionally large herd size in large-scale pig farms. Large fattening farms operate as all-in/all-out or continuous flow systems. The large-scale breeding herds are predominantly farrow-to-finish types. In large-scale breeding farms, PRRS eradication was carried out by the depopulation-repopulation method in 33 farms, of which 23 received state compensation, 18 farm units either finished production or changed to producing fatteners only. Two farms used the test and removal method for eradication. One farm was classified as ‘vaccinated free’. At this farm the breeding animals are vaccinated continuously but there is no vaccination of the progeny at any age, and the PRRS-free status of the farm is strictly controlled and monitored. By 31 December 2019, all pigs in five euroregions of Hungary had become free from PRRS virus, while the PRRS eradication process is still ongoing in the remaining two regions.

In the EU Member States with a traditionally significant pig industry, the prevalence of PRRS infections is high. Therefore, the Pig Strategy of the Government of Hungary prioritises eradication of PRRSV in Hungary. For the first time among the EU Member States, a National PRRS Eradication Programme was introduced in order to reach a more efficient, economical and competitive international market position. Although its significance has decreased in recent decades, 20% of the Hungarian pig population is still kept on small-scale (backyard) farms (< 100 animals). The prevalence of PRRSV in backyard farms was 3.9% at the beginning of the programme. The present paper details the measures applied during the different phases of the programme in backyard farms. During all the phases, serological testing of the breeding animals of the registered small-scale herds was performed, including the highest number of individual animals. Seropositive individuals were tested by PCR and were removed from the backyard farm within the framework of official measures. By sequencing the identified PRRS strains, the possible epidemic relationships between small-scale and large-scale farms were continuously monitored. As a result of the programme, PRRS-free status of the small-scale herds was achieved by the end of 2015, and this status was maintained in 2016-2018.

Porcine reproductive and respiratory syndrome virus 2 (PRRSV-2) remains sporadic in Europe. In this study, we investigated the molecular epidemiology of PRRSV-2 infections encompassing 15 years in Hungary. Partial (423 bp long) ORF5 sequences (n = 44) from 20 Hungarian pig herds were analyzed. The study strains fell into two genetic lineages, L1 and L5, being L5 strains more prevalent (88.6 vs. 11.4%). Pairwise sequence identities within Hungarian representative PRRSV-2 strains ranged between 84.7 to 100% (nucleotide, nt) and 85 to 100% (amino acid, aa). When compared with reference strains, identity values fell between 87 and 100% (L1, nt 87–91%, aa 87–93%, reference strain IAF-exp91; L5, nt 87–100%, aa 88–100%, reference strain Ingelvac MLV). Epidemiologic examination implied that the majority of L5 strains were imported repeatedly from other European countries where Ingelvac MLV was approved for routine use. The emergence of L1 strains was thought to be associated with a single introduction and subsequent dissemination between pig farms of a large integrator. Results presented here contribute to a better understanding of the epizootiology of PRRSV-2 infections and shed light on the genetic diversity of viral strains in non-endemic countries.

Background: Porcine reproductive and respiratory syndrome (PRRS) is an infectious disease with widespread distribution and is currently a major cause of economic loss in pig production. In Hungary, a National PRRS Eradication Program was introduced in order to reach a more efficient, economic and competitive international market position. The EU also approved the program, but the resultant legal obligations placed a burden on Hungarian producers in order to comply with EU competition rules. The veterinary authorities carried out the implementation of the program with the consent, continuous support and monitoring by the organizations of the pig industry as well as a scientific committee. The PRRS eradication program in Hungary was based on a regional territorial principle and was obligatory for every swine farm within those regions. In Hungary large fattening farms operate as all-in/all-out or continuous flow system. The large-scale breeding herds are predominantly farrow-to-finish types. Although its significance has decreased in recent decades, 20% of the Hungarian pig population is still kept in small-scale (backyard) farms (< 100 animals). Each PRRS-infected large-scale farm had to develop a unit-adapted eradication plan, including external and internal biosecurity measures, vaccinations, etc. It was crucial to render each fattening unit free of the disease since fattening units play a significant role in spreading the virus across the country. Eradication efforts mainly implemented depopulation-repopulation methods, with some farms using the test and removal method instead. Results: As the eradication progressed over the years, the introduction of infected fattening pigs was restricted. Because of these measures, by the end of 2018, Hungarian large-scale fattening farms became free of PRRS. The PRRS-free status of the small-scale herds was achieved by the end of 2015, and this status was maintained from 2016–2021. By the 31st of December in 2021, all breeding pigs at large scale-farms in Hungary had become free of wild type PRRS virus. By the 31st of March in 2022, the total pig population of the country, including all backyard farms and fattening units, had achieved PRRS-free status. Conclusions: The future goal is to secure and maintain the PRRS free status of Hungary by strict import regulations of live animals combined with continuous and thorough screening of incoming and resident herds for the presence of the virus.