Regional level risk factors associated with the occurrence of African swine fever in West and East Africa

Karanina J. Honer,Willem F. de Boer,Zheng Y. X. Huang,Marc Naguib,Frank van Langevelde

doi:10.1186/s13071-016-1953-z

Karanina J. Honer, Willem F. de Boer + Show 3 more

Open Access

https://doi.org/10.1186/s13071-016-1953-z

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Abstract

BackgroundAfrican swine fever (ASF) causes severe socio-economic impacts due to high mortality and trade restrictions. Many risk factors of ASF have been identified at farm level. However, understanding the risk factors, especially wild suid hosts, determining ASF transmission at regional level remains limited.MethodsBased on ASF outbreak data in domestic pigs during 2006–2014, we here tested, separately for West and East Africa, which risk factors were linked to ASF presence at a regional level, using generalized linear mixed models.ResultsOur results show that ASF infections in the preceding year was an important predictor for ASF presence in both West and East Africa. Both pig density and human density were positively associated with ASF presence in West Africa. In East Africa, ASF outbreaks in domestic pigs were also correlated with higher percentages of areas occupied by giant forest hogs and by high-tick-risk areas.ConclusionsOur results suggest that regional ASF risk in East Africa and in West Africa were associated with different sets of risk factors. Regional ASF risk in West Africa mainly followed the domestic cycle, whereas the sylvatic cycle may influence regional ASF risk in East Africa. With these findings, we contribute to the better understanding of the risk factors of ASF occurrence at regional scales that may aid the implementation of effective control measures.

Highlights

African swine fever (ASF) causes severe socio-economic impacts due to high mortality and trade restrictions
For West Africa, the results of stepwise model selection (Table 4) showed that ASF occurrence in domestic pigs was positively associated with previous infection status (PreInf, Odds ratio (OR) = 4.63, 95% Confidence interval (CI): 3.92–5.46, P < 0.001), pig density (Pig, OR = 1.32, 95% CI: 1.19–1.46, P = 0.007) and human population density (Human, OR = 1.36, 95% CI: 1.23–1.51, P = 0.002), though many variables were significantly correlated with ASF presence in the univariate analysis
Our study showed that the factors that play an important role in ASF transmission at farm level, like previous infection status and domestic pig density, link to ASF disease dynamics at regional level

Summary

Introduction

African swine fever (ASF) causes severe socio-economic impacts due to high mortality and trade restrictions. Understanding the risk factors, especially wild suid hosts, determining ASF transmission at regional level remains limited. African swine fever (ASF), caused by a DNA virus of the genus Asfivirus, is a highly contagious disease for domestic pigs. It can have severe socio-economic impacts due to high mortality and trade restrictions [1]. The sylvatic cycle has been documented in some Eastern and Southern African countries [7, 9,10,11,12] It involves wild suids as the host, including the common warthog (Phacochoerus africanus), and is spread via soft ticks (Ornithodoros moubata) to domestic pigs making the virus persistent [13]. A recent study assessed the suitability of these two transmission

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