Serologic Evidence Of Equine H7 Influenza Virus In Polo Horses In Nigeria

Abstract

As part of ongoing influenza virus surveillance in Nigeria, eighty serum samples and forty nasopharyngeal swabs were randomly obtained from polo horses from across the country during the 2004 annual polo tournament in Lagos and analyzed serologically. Forty serum samples each were analyzed by haemagglutination inhibition (HI) and Viral Neutralization (VN) tests for antibodies against the A/eq/Sao Paulo/76 (H7N7) equine-1 influenza virus while Virus isolation was carried out from the sterile nasopharyngeal swabs using 10-11 day old fertile embryonated hen eggs and African green monkey (Vero) monolayer cells. High HI and VN antibody titres of 640 - 20,480 and 320 - 5120 respectively were found in majority (>62%) of the test sera while no virus was isolated in eggs and tissue culture. These findings showed high immunological response to the equine-1 virus thought to be innocuously circulating in Nigeria and in view of the cross reactivity of influenza virus subtypes among different host species, it is probable that these horses are being exposed to avian H7 viruses. More studies are therefore needed to isolate and characterize H7 influenza viruses that may prove to be pathogenic to horses.