Presence of Newcastle Disease in Vaccinated Indigenous Chicken from Farms in Selected Regions in Kenya- a Cross Sectional Study

Abstract

Indigenous chicken farming is an important source of livelihood for rural families in Kenya. However, the farmers experience challenges including infections from poultry diseases such as Newcastle disease. Vaccination has been used over the years to provide immunity in flocks against disease outbreaks. However, Newcastle diseases virus (NDV) outbreaks are still reported among vaccinated flocks. This study examined the presence of Newcastle disease virus among vaccinated indigenous chicken (IC), in relation to weather (temperature, rainfall, humidity, wind speed), production system, and interspecies interaction. Samples were collected from flocks of indigenous chicken vaccinated with NDV vaccine from 68 households in six counties in Kenya (Bomet, Baringo, Kilifi, Nakuru, Kakamega, and Machakos). Some of the households (n=5 (9%) reported previous ND outbreaks. All the households had other mixed species of birds (ducks, geese, turkey, wild birds). The total number of samples collected was n=1210, oropharyngeal swabs-650, cloacal swab-650. The total number of the pooled sample was 246 pools. The samples were analysed by RT-qPCR targeting the NDV matrix gene. NDV matrix gene was detected in the pooled samples n=177(72%). Out of the positive samples, n=56(32%) were from vaccinated flocks, 91(51%) were from the cloacal swab and 86(49%) from the oropharyngeal swab. The samples were collected during varying weather (temperature, rainfall, humidity and wind speed). There was a statistical significance on the relationship between the presence of NDV and the Vaccination history (p=0.034); production system, (p=0.004), and month of sample collection (p<0.0001). However, there was no significance on the relationship between the presence of NDV and the interaction of IC and other birds. Failure to vaccinate IC results in the presence of the NDV. The free-range production system can have many cases of NDV due to the lack of biosecurity measures. Therefore, farmers should be advised to vaccinate their IC.