Impact of porcine epidemic diarrhea virus infection at different periods of pregnancy on subsequent reproductive performance in gilts and sows.

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.