Survey of porcine reproductive and respiratory syndrome virus in cattle egrets (Bubulcus ibis) on Oʻahu

Abstract

Porcine reproductive and respiratory syndrome (PRRS) drastically affects the profitability of pig production by causing reproductive and respiratory difficulties. The virus can infect pigs directly and indirectly. Airborne transmission is suspected, but controlled experiments have yielded mixed results. The ability of animals to transmit virus bad been demonstrated in MaI1ard ducks, houseflies and mosquitoes. On some hog farms worldwide and on O'ahu where PRRS occur despite strict biosecurity, the route of transmission remains a mystery. The objective of this project was to determine the PRRS status of cattle egrets, who are frequent visitors to livestock farms. Sera from 24 cattle egrets and 2 spotted doves (incidentally) culled by the USDA in West O'ahu were tested fur PRRS virus antibodies. Blocking enzyme-linked immunosorbent assay results fur 2S serum samples were negative and I dove sample was borderline positive with percent inhibition at 17.34% (positive ~17%). Fluorescent focusing neutralization resu1ts on 21 serum samples yielded eight negatives «1:4 dilution), 10 borderlines (1:8 dilution), and 3 low positives (1: 16 dilution). Western blotting and reverse transcription polymerase chain reaction were unable to detect viral antibodies or nucleic material, respectively. Low positives in serological tests due to cross-reactions with other viruses and false negatives in the polymerase chain reaction due to variation in strains of PRRS virus cannot be ruled out. These results do not provide evidence that cattle egrets are potential carriers of the PRRS virus, but a controlled challenge study should be considered. Identifying and controlling routes of transmission of PRRS is vital in protecting Hawai'i's pork industry.