ASF outbreak investigations and sample collection
Between 2016 and 2018), 37 ASF outbreaks were reported in domestic pigs
in 8 States of Nigeria (Fig 1). One hundred ten (110) outbreak samples
were collected consisting of whole blood and tissue (liver, spleen, and
lymph nodes) from 147 pig farms. The affected States were Abia, Benue,
Enugu, Kaduna, Imo, Lagos, Plateau, and Taraba States (Fig. 1, Table 1).
Samples were collected at intensive pig farms and free-roaming pigs in
the affected States of the country. Laboratory diagnosis was carried at
the ASF National Reference Laboratory (NRL) at the National Veterinary
Research Institute (NVRI), Vom, Nigeria. Epidemiological investigations
were carried out in all affected States. In 2016, ASF was reported in
three States of Nigeria including: Benue, Kaduna, and Plateau States.
One of the ASF outbreaks in Plateau State was reported in an
institutional farm and the source of viral introduction was through farm
workers. Three States (Abia, Imo, and Enugu) in Eastern Nigeria with
contiguous common border reported ASF outbreaks in 2017. ASF outbreak in
Imo State occurred due to the introduction of pigs from the Republic of
Cameroon. The outbreak affected a cluster of seven intensive pig farms
with a herd size of 60-1000 pigs and recorded mortality of 73%
(2168/2930). A similar outbreak of ASF also occurred in neighbouring
Abia State in a cluster of nine farms and a mortality rate of 80%
(845/1050) was recorded in exotic breeds of pigs. The ASF outbreak
started in one of the farms and it spread to other farms through the
activities of butchers who also kept pigs. The ASF outbreak in Enugu
State was also in an intensive small-holder pig farm. Similarly, ASF
outbreaks were reported in 2018 in 3 Northern States (Benue, Taraba, and
Plateau) with common boundaries (Fig 1). The outbreak started in Plateau
State and was reported between April and November 2018 in small-holder
intensive pig farms mostly in Jos-South Local Government Area (LGA) (Fig
1). Also in September 2018, the disease was reported in Zing, Taraba
State, ASF affected 101 pig farmers with recorded mortality of 45.6%
(3354/7360) pigs. Affected animals were mainly free-roaming Nigerian
indigenous pig (NIP) breeds. In addition, widespread ASF outbreaks were
reported in four major locations of Gboko, Otukpo, Yandev, and Makurdi,
all in Benue State from June to December 2018. The affected pig farms
were breeder and smallholder intensive farms. Lastly, in southwestern
Nigeria, Lagos State recorded ASF outbreak close to the Nigeria-Benin
republic international border in an intensive pig farm in 2018 with 75%
(40/60) mortality.