Assessing the spatial extent of African swine fever spread in Nigeria

Abstract

Abstract African swine fever (ASF) is the most important disease of pigs due to its rapid spread and high mortality. ASF has been enzootic in Nigeria since its introduction in 1997, and understanding the spatial spread of the disease is important for devising effective control measures. Hence, this study assessed the spatial extent of ASF spread in selected States of Nigeria, namely: Adamawa, Benue, Cross-River, Delta, Kaduna, Lagos, Ogun, Plateau, and Taraba States. This assessment was based on three aspects: (i) ASF prevalence using tissue and sera collected from pig farms and abattoirs/slaughter slabs (ii) data collection from veterinary authorities and pig farmers using interviews, and (iii) field observation of farmer practices in relation to ASF spread. The results of tissue samples analyzed by polymerase chain reaction revealed an overall ASF prevalence of 10.21% (100/979), with the highest State-level prevalence recorded in Plateau (32.09%), followed by Cross River (25.47%), Kaduna (6.25%), and lowest in Benue (4.26%) States. Farms under the extensive husbandry system (6.98%) had a higher prevalence compared to farms under intensive husbandry system (2.09%). Abattoir samples had a higher positivity rate (16.70%) compared to pig farm samples (4.58%). Analyzed sera revealed an ASF seroprevalence of 17.03% (87/511), with the highest seroprevalence in Benue (42.9%), followed by Lagos (36.69%), Taraba (34.8%). Plateau (10.25%) and the lowest in Ogun (5.9%) State. Husbandry system-wise, a higher seroprevalence was recorded in extensive husbandry systems (20.74%), compared to intensive systems (14.29%). Data collected from veterinary authorities and farmers revealed mixed results. In some States, ASF was alluded to be major concern, while in others, they stated otherwise. Finally, unregulated pig movement and pigs with clinical signs suggestive of ASF were observed in majority of the States during this study. In conclusion, based on the three aspects of this study, ASF may be widespread in Nigeria.