Experimental infection of pheasants with a velogenic chicken isolate of Newcastle disease virus

Newcastle disease (ND) is a highly contagious infection of many avian species, causing enormous losses in poultry production worldwide. The objective of this study was to reveal the clinical feature, virus shedding, and immune response following infection with a velogenic chicken isolate of Newcastle disease virus (NDV) in susceptible and vaccinated pheasants. Eighty day-old pheasant chicks were allotted to four groups. At 30 days of age, the birds in groups 1 and 3 were vaccinated with B1 strain via eye drop. Two weeks later, each bird in groups 1 and 2 was inoculated with 100 μL(50 μL/eye) of NDV-infected allantoic fluid containing 105 EID50 of viral inoculum. All groups were inspected daily for three weeks. Swab samples were taken at different time points and verifi ed for NDV infection by using reverse-transcription polymerase chain reaction (RT-PCR). Serological examination was also made by haemagglutination-inhibition assay. Clinically, watery mucoid feces was observed only in one case among the vaccinated challenged birds, whereas the unvaccinated challenged birds showed anorexia, mild depression and head deviation. Out of 20 birds in group 2, one case (5%) died. Based on RT-PCR, virus shedding was only observed among the unvaccinated birds from 5 to 14 days aft er challenge. The NDV was detected more in tracheal swabs (40%) than in cloacal swabs (30%). The infected birds showed a high seroconversion. In conclusion, the velogenic NDV circulating in Iranian chicken flocks has a low pathogenicity for pheasants, and ocular vaccination with B1 strain could provide a good protection.