Serological profile of offspring on an intensive pig farm affected by porcine reproductive and respiratory syndrome

ObjectiveTo evaluate/predict the offspring serum profile of antibodies against Porcine reproductive and respiratory syndrome virus (PRRSV) in an affected intensive herd, whereas sows are vaccinated, and determine the better sample time using pigs as sentinels.MethodsSerum samples were collected from a total of 66 offspring pigs from a PRRSV endemic herd, whereas only sows were vaccinated. Six animals per grouped age were randomly selected with 0 (at perinatal time), 1, 2, 3, 6, 9, 12, 15, 18, 21 and 24 weeks of age. Individual and three pooled samples were tested by ELISA and PCR, respectively.ResultsThe proportion of seropositive animals was 75.0% (18/24), 33.3% (6/18) and 95.8% (23/24) at farrowing (0–3 weeks), nursery (6–12 weeks) and growing/finishing (15–24 weeks) phases, respectively. It was 46 times more likely (P < 0.01) to observe seropositive pigs on the growing/finishing than on nursery phase. European PRSSV strain was detected on serum of 6, 9 and 15-weeks-old pigs. Polynomial fit degree 4 regression between sample-to-positive (S/P) ratios and age of pigs (r = 0.78; R2 = 0.60; P < 0.001) estimated a quickly decrease of maternal antibodies, above 0.4 S/P value (cut off), until the 6th week following by a progressive increment of humoral immunity until 21st week of age, when it declines.ConclusionsThe results indicate that the piglets can present viremia early at nursery, and the 18th – 21st weeks are the best time to sample offspring pigs, as sentinel, from PRRSV contaminated intensive herds.