An epidemiological study of African swine fever (ASF) was conducted between
March 2006 and September 2007 in a rural area adjacent to the Gorongosa National
park (GNP) located in the Central Mozambique. Domestic pigs and warthogs were
sampled to determine the prevalence of antibodies against ASF virus and the salivary
antigens of Ornithodoros spp. ticks, while ticks collected from pig pens were
tested for the presence of ASFV. In addition, 310 framers were interviewed to gain a
better understanding of the pig value chain and potential practices that could
impact on the spread of the virus. The sero-prevalence to ASFV was 12.6% on
farms and 9.1% in pigs, while it reached 75% in warthogs. Approximately 33% of
pigs and 78% of warthogs showed antibodies against salivary antigens of ticks. The
differences in sero-prevalence between farms close to the GNP, where there is
greater chance for the sylvatic cycle to cause outbreaks, and farms located in the rest
of the district, where pig to pig transmission is more likely to occur, were marginally
significant. Ornithodoros spp. ticks were found in only 2 of 20 pig pens outside
the GNP, and both pens had ticks testing positive for ASFV DNA. Interviews carried
out among farmers indicated that biosecurity measures were mostly absent.
Herd sizes were small with pigs kept in a free-ranging husbandry system (65%).
Only 1.6% of farmers slaughtered on their premises, but 51% acknowledged allowing
visitors into their farms to purchase pigs. ASF outbreaks seemed to have a
severe economic impact with nearly 36% of farmers ceasing pig farming for at least
1 year after a suspected ASF outbreak. This study provides the first evidence of the
existence of a sylvatic cycle in Mozambique and confirms the presence of a permanent
source of virus for the domestic pig value chain.