Production losses five months after outbreak with a recombinant of two PRRSV vaccine strains in 13 Danish sow herds

Abstract

Background In July 2019, a PRRSV-negative boar station was infected with a recombinant of two PRRSV vaccine strains, which subsequently spread to at least 36 herds that had received semen from the boar station. In the following months, all the infected herds reported reduced productivity. The aim of the present study was to evaluate the impact of the PRRS outbreak. Results Production data were collected from 13 of the herds. The average levels of farrowings/week, liveborns/litter, stillborns/litter, pre-weaning mortality and weaned pigs/litter were compared for the five-month period after infection and the preceding 7 months before infection with the new variant of PRRSV-1. Twelve herds experienced a decrease in farrowings/week (0.1–10.8% fewer farrowings/week), and all herds experienced fewer liveborns (0.8–4.8 fewer liveborns/litter) and more stillborns (0.6–2.6 more stillborns/litter). Pre-weaning mortality nearly doubled in half of the herds. Overall, the 13 herds were missing 2.4–6.5 pigs/litter at weaning during the 5 months after infection compared to the seven preceding months before infection. Conclusion In this study, the impact of this new PRRSV-1 variant on productivity exceeded that typically seen in Danish herds infected with PRRSV-1.

Impacts of Quarterly Sow Mass Vaccination with a Porcine Reproductive and Respiratory Syndrome Virus Type 1 (PRRSV-1) Modified Live Vaccine in Two Herds

“…Following an acute outbreak of PRRSV, most producers aim to establish a "positive stable" sow herd [2,3], whereby all breeding animals are immunised prior to first service followed by repeated sow mass vaccination (SMV) up to four times yearly [4][5][6]. In Denmark, 98.8 percent of the PRRSV-1 vaccines sold for breeding animals in 2020 were MLV vaccines (https://vetstat.fvst.dk/vetstat/, accessed on 5 April 2021), which is in accordance with the situation in other countries.…”

Challenge of Naïve and Vaccinated Pigs with a Vaccine-Derived Recombinant Porcine Reproductive and Respiratory Syndrome Virus 1 Strain (Horsens Strain)

“…Overall, these data indicate that PRRSV outbreaks caused by the “Horsens” strain may be efficiently controlled by MLV vaccines containing a heterologous strain, but there may be differences in the level of protection between vaccines. It should be noticed that some of the herds that experienced outbreaks with the Horsens strain in 2019 managed to control the outbreak by employing mass-vaccination also with the Porcilis PRRS vaccine [ 3 ].…”

“…A recent paper on the “Horsens” recombinant strain revealed losses in infected herds exceeding those normally seen in Danish herds in connection to PRRSV-1 outbreaks [ 3 ]. In addition, infection of pregnant sows in the last trimester induced severe reproductive failures, however, to a lesser extent than those seen following another well-characterized PRRSV-1 strain (Olot91) [ 4 ].…”

“…Follow-up in 13 of the affected herds revealed production losses twice of what is normally observed in Danish herds infected with PRRSV-1 [ 3 ]. The clinical signs included sustained reproductive failures and high piglet mortality.…”

First Study to Describe the Prevalence of Porcine Reproductive and Respiratory Syndrome Virus and Porcine Circovirus Type 2 among the Farmed Pig Population in the Hong Kong Special Administrative Region

“…In pig farming systems, respiratory and reproductive diseases cause productivity and consequential economic losses [1][2][3][4]. Respiratory disease is of particular importance in intensive pig production systems [1,5], especially those with natural ventilation systems [6], such as farms in the Hong Kong Special Administrative Region (HKSAR).…”