Preliminary Outbreak Investigation and Spatial Epidemiology of Rabbit Hemorrhagic Disease Outbreak in Nigeria

The outbreak of highly contagious transboundary rabbit hemorrhagic disease (RHD) in Nigeria has a severe socio-economic impact on the rabbit industry. We present the outbreak investigation and spatial epidemiology of the first confirmed RHD outbreak in Nigeria from a field survey of 28 stochastic outbreaks in Kwara State, north-central Nigeria. A total of 1,639 rabbits died from 2,053 susceptible rabbits. The serotype RHDV-2 was detected in tissue samples from some of the outbreaks. The case fatality rate of the RHDV-2 outbreak was 79.8%. The source of the outbreak is still unknown. Most (71.4%) of the farmers had introduced new rabbits into their farms 1-2 weeks before the outbreak. Most of the farmers practiced biosecurity measures such as farm fencing (83.1%) and routine disinfection of the farm materials (53.6%). However, only 17.8% of the farmers enforced movement restrictions into their farms. Some of the farmers (42.8%) had restocked their farms after being affected by the RHD outbreak and 75% of all those farmers that have restocked had used the RHD vaccine. There was no statistically significant association between adherence to biosecurity measures and the RHD outbreak in affected farms (p = 0.408). However, the introduction of new rabbits into rabbit farms significantly pre-disposed farms to the RHD outbreak (p < 0.001). There is a need for active surveillance of RHD across the country to ensure efficient and effective tracking, monitoring, and control of the disease. Equally, understanding the genetic diversity of the Lagoviruses in Nigeria that cause RHD to aid vaccine development is of utmost importance to prevent future RHD outbreaks.

Automated summary

The outbreak of highly contagious transboundary rabbit hemorrhagic disease (RHD) in Nigeria resulted in significant socio-economic impacts on the rabbit industry, with a high case fatality rate. The introduction of new rabbits was a significant predisposing factor for the outbreak, despite most farmers practicing some biosecurity measures. Active surveillance and understanding genetic diversity of Lagoviruses in Nigeria for vaccine development are crucial for preventing future RHD outbreaks.