Spatial clustering of pathology submissions during the initial introduction and spread of avian influenza H5N1 in poultry in Nigeria in 2006-2007.

Abstract

Highly pathogenic avian influenza (HPAI) virus H5N1 spread throughout Nigeria between 2006 and 2007. Bird samples collected across the country were submitted through the free-of-charge (FOC) program to the National Veterinary Research Institute, Vom (NVRI-Vom) laboratory. The present article describes the spatial distributions and evaluated clustering of the FOC submissions from poultry farms at the global, local, and focal levels between 2006 and 2007 epidemic in Nigeria. Spatial statistics evaluating clustering of the FOC submissions were implemented using the Moran's I test, the purely spatial cluster analysis with the SaTScan Poisson model, and the Bithell's linear score test. A significant global clustering of the FOC submissions was observed. Significant local clusters of submissions were observed in the North-East, North-Central, and South-West zones. There was significant decline in FOC submissions with increasing distance from NVRI-Vom. These results indicated that the geographic area of influence of the FOC submission program in Nigeria was limited to regions closer to the diagnostic laboratory. This work provides a detailed insight into the surveillance activities during the HPAI outbreaks in Nigeria, and should assist policy-makers and field veterinarians to improve the effectiveness of national eradication plans in the face of any outbreak of animal diseases.