An assessment of the epidemiology and socio-economic impact of the 2019 African swine fever outbreak in Ngara district, western Tanzania

Authors: CC. Kivumbi, C.Yona, J.N. Hakizimana, G.Misinzo


African swine fever (ASF) is a contagious viral transboundary animal disease affecting domestic pigs caused by ASF virus (ASFV). This study was conducted in order to determine the genetic characteristics, risk factors and socio-economic impact of an ASF outbreak in 2019 in Ngara, western Tanzania. Tissue samples from dead domestic pigs with clinical picture suggestive of ASF infection were collected for ASF confirmation and genetic characterization of ASFV. Data on the risk factors and socio-economic impact associated with the ASF outbreak were collected from consenting farmers using a semi-structured questionnaire. Disease confirmation was done by detection of genomic ASFV DNA using polymerase chain reaction. Partial amplification of the ASFV genome, dideoxynucleotide sequencing of the PCR products followed by bioinformatics analyses was conducted to determine the ASFV genotypes. Phylogenetic reconstruction of the variable 3’-end of the B646Lgene clustered the ASFV isolate into genotype X. Analysis of the intergenic fragment sequences between 173R and 1329L genes showed that the viral strains TAN/19/Ngara and Kenya 1950 similarly lacked a 36 bp fragment that is present in strain Ken05/Tk1. Feeding pigs of uncooked swill was shown to be significantly associated with ASF spread (OR=3.08, C.I.95%=1.06-8.99, P=0.0009). Occurrence of ASF outbreak resulted in loss of income and investment as most farmers kept pigs for the purpose of income generation. Food security was disturbed due to high pig mortality following occurrence of ASF outbreak. A total of 93,630,000 Tanzanian shillings (approximately 41,065 USD) was estimated to be lost as a result of pigs’ mortality in 219 households. The findings of the present study associate ASFV genotype X with the 2019 ASF outbreak in Ngara and feeding pigs with uncooked swill with spread of the disease.

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