Contents lists available at ScienceDirect Veterinary Microbiology journal homepage: www.elsevier.com/locate/vetmic Use of processing fluids and serum samples to characterize porcine reproductive and respiratory syndrome virus dynamics in 3 day-old pigs Carles Vilalta a, ⁎ , Juan Sanhueza a , Julio Alvarez b,c , Deb Murray d , Montserrat Torremorell a , Cesar Corzo a , Robert Morrison a,1 a Veterinary Population Medicine Department, College of Veterinary Medicine, University of Minnesota, 1365 Gortner Ave., St Paul, MN 55108, United States b VISAVET Health Surveillance Center, Universidad Complutense, Avda Puerta de Hierro S/N, Madrid, 28040, Spain c Departamento de Sanidad Animal, Facultad de Veterinaria, Universidad Complutense, Avda Puerta de Hierro S/N, Madrid, 28040, Spain d New Fashion Pork, Jackson, MN, United States ARTICLE INFO Keywords: PRRSV Monitoring Processing fluids ABSTRACT Collection of serum samples of pigs at weaning to monitor for porcine reproductive and respiratory syndrome virus (PRRSV) has become a common practice to determine PRRSV herd infection status. Diagnostic sensitivity of this practice is low in herds undergoing PRRSV elimination once prevalence of infection is near zero. Thus, the goal of this study was to characterize the dynamics of PRRSV infection in 3 day-old pigs overtime using serum and serosanguineous fluids obtained as part of castration and tail docking practices (processing fluids (PF)). Secondary goal was to estimate sensitivity and specificity of PF in the 3 day old population. A 6000 breed-to- wean sow herd was monitored every three weeks for 23 weeks after a PRRSV outbreak by collecting both PF and individual serum samples from all pigs in the selected litters. Out of the 77 litters tested, 23 (29.8%) were identified as positive using the PF and the serum samples, with a Cohen’s kappa statistic of 0.81 (95% CI: 0.59–1) between the results obtained in each sample type. The sensitivity and specificity of the PF relative to the results in serum was 87% (95% CI: 66%–97%) and 94% (95% CI: 85%–99%) respectively. The percentage of PRRSV positive litters decreased over time and litters from gilts were more likely to test positive than those from older sows. Overall, the study demonstrates that PF can be a convenient and reliable specimen to monitor PRRSV infection in breeding herds. 1. Introduction Porcine reproductive and respiratory syndrome virus (PRRSV) continues to generate economic losses to producers (Holtkamp et al., 2013). In the last two decades, methods to eliminate PRRSV have been developed and optimized (Corzo et al., 2010; Torremorell et al., 2003). Despite the success to eliminate the virus through herd closure strate- gies, there are still unanswered questions on duration of closure pro- tocols and risk of newborn pigs as factors for prolonged infections in breeding herds (Allerson et al., 2014; Linhares et al., 2014). PRRSV infections during the third gestation trimester lead to the birth of viremic pigs which contribute to the dissemination of the virus during the suckling period (Cano et al., 2009). Cross-fostering of pigs, move- ment of contaminated fomites (i.e. needles and boots) and poor internal biosecurity can also contribute to endemic PRRSV infections in piglets (Otake et al., 2002a,b). Elimination of PRRSV from infected breeding herds is possible when PRRSV-free litters are born consistently and there are internal biosecurity measures in place to stop within-far- rowing barn viral transmission. In recent years, molecular diagnostic tests have become an im- portant tool to declare herds as stable (i.e. consistently weaning PRRSV- negative piglets) (Holtkamp et al., 2011). Traditionally, these tests have been used in due-to-wean pig serum samples to generate evidence of absence of viral replication and transmission in pigs prior to wean. The recommended sampling protocol consists of bleeding at least 30 due-to- wean pigs 30 days apart for a minimum of 90 days and testing them by RT-PCR in pools of 5 (Holtkamp et al., 2011). Pooling allows to test a larger number of animals, thus increasing herd-level sensitivity while keeping the diagnostic costs low (Rovira et al., 2007). However, cost- effective sampling approaches that can be integrated in the farm rou- tine procedures are needed. In pig production there are management practices (i.e. tail docking https://doi.org/10.1016/j.vetmic.2018.09.006 Received 10 July 2018; Received in revised form 12 September 2018; Accepted 13 September 2018 ⁎ Corresponding author. 1 Deceased on May 2, 2017. E-mail addresses: cvilalta@umn.edu, carlesvilalta@yahoo.es (C. Vilalta). Veterinary Microbiology xxx (xxxx) xxx–xxx 0378-1135/ © 2018 Elsevier B.V. All rights reserved. Please cite this article as: Vilalta, C., Veterinary Microbiology, https://doi.org/10.1016/j.vetmic.2018.09.006