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This study assessed the effect of whole-herd porcine reproductive and respiratory syndrome (PRRS) modified-live virus (MLV) vaccination on herd-level reproductive performance, PRRS virus (PRRSV) viremia, and antibody in a subset of females in a 1,200-sow commercial herd in Thailand. Following a PRRSV outbreak, the entire herd was vaccinated with PRRS MLV twice at 3-week intervals and at 3-month intervals, thereafter. Reproductive performance data over a 3-year period were available for analysis. Serum samples were collected before and after vaccination and tested by PRRSV ELISA and reverse transcription-polymerase chain reaction. Vaccination was statistically associated with a lower abortion rate (1.4 vs. 1.6 %), farrowing rate (83.8 vs. 90.0 %), total born (10.6 vs. 11.4 piglets/litter), liveborn (10.0 vs. 10.3 piglets/litter), stillbirths (4.6 vs. 7.0 %), mummies (0.7 vs. 1.6 %), and a higher return rate (11.3 vs. 5.9 %) when compared with the period before the PRRSV outbreak. Pregnant females vaccinated during early gestation farrowed fewer liveborn and more mummies than the comparison group, whereas females vaccinated during late gestation had a lower farrowing rate. In this herd, PRRS whole-herd vaccination had neutral, positive, and negative effects on reproductive performance. Thus, the decision to implement whole-herd vaccination should be balanced between the benefits derived from reproductive performance improvements, e.g., fewer abortions, stillborn piglets, and mummified fetuses, and the effect of vaccination on pregnant females.

Reproductive performance of gilts and sows in a swine commercial herd following an outbreak of porcine epidemic diarrhea virus (PEDV) were investigated. A PEDV outbreak was observed in March 2008 in a swine herd in Thailand. The disease was diagnosed by clinical symptoms, gross and histopathology and viral detection using reverse transcriptase-polymerase chain reaction assay. The intestines of the infected piglets were collected, minced and fed to all of the gilts and sows within 2 weeks after the onset of the PEDV outbreak. Reproductive data were collected during a period from January 2007 to July 2008 and were retrospectively evaluated. The farrowing rate (FR), return rate (RR), abortion rate (AR), number of total piglets born per litter (TB), number of piglets born alive per litter (BA), percentage of stillbirth piglets per litter (SB), percentage of mummified fetus per litter (MM) and piglet's birth weight (BW), before and after the PEDV outbreak were compared. It was found that the impact of PEDV infection on the reproductive performance of gilts and sows depended on the period of pregnancy when the females were exposed to the pathogen, and parity number. The pregnant females infected with PEDV during the first 30 days of pregnancy had a 12.6 percentage point decrease of FR (91.1% vs. 78.5%, P=0.003), a 5.7 percentage point increase of RR (3.5% vs. 9.2%, P=0.01), a 1.3 percentage point increase of AR (2.1% vs. 3.4%, P=0.01) and a 2.0 percentage point increase of MM (3.5% vs. 5.6%, P<0.001). SB increased in the pregnant females that were infected with PEDV during 91-120 days of pregnancy (1.8 percentage points, 4.5% vs. 6.2%, P=0.01). The impacts of PEDV infection on subsequent reproductive performance were more severe in the pregnant gilts than the pregnant sows. PEDV infection during the first 30 days of pregnancy resulted in a decrease of TB by 1.4 (11.7 vs. 10.3 piglets/litter, P<0.001) and a decrease of BA by 2.2 (10.7 vs. 8.5 piglets/litter, P<0.001) in the gilts' litters, while the influence of PEDV infection on TB and BA was not significant in sows (P>0.05). It was concluded that natural infection of PEDV in the pregnant gilts and sows caused a reduction of subsequent reproductive performance., (Copyright © 2010 Elsevier B.V. All rights reserved.)