An Updated Review of Ornithodoros Ticks as Reservoirs of African Swine Fever in Sub-Saharan Africa and Madagascar

Abstract

This updated review provides an overview of the available information on Ornithodoros ticks as reservoirs and biological vectors of the ASF virus in Africa and Indian Ocean islands in order to update the current knowledge in this field, inclusive of an overview of available methods to investigate the presence of ticks in the natural environment and in domestic pig premises. In addition, it highlights the major areas of research that require attention in order to guide future investigations and fill knowledge gaps. The available information suggests that current knowledge is clearly insufficient to develop risk-based control and prevention strategies, which should be based on a sound understanding of genotype distribution and the potential for spillover from the source population. Studies on tick biology in the natural and domestic cycle, including genetics and systematics, represent another important knowledge gap. Considering the rapidly changing dynamics affecting the African continent (demographic growth, agricultural expansion, habitat transformation), anthropogenic factors influencing tick population distribution and ASF virus (ASFV) evolution in Africa are anticipated and have been recorded in southern Africa. This dynamic context, together with the current global trends of ASFV dissemination, highlights the need to prioritize further investigation on the acarological aspects linked with ASF ecology and evolution.

Keywords: East Africa; Southern Africa; argasid; distribution; ecology; endemic; p72 genotypes; sylvatic cycle; vector competency; warthog.

Figure 1

Photos of dorsal and ventral view of female (left) and male (right) Ornithodoros moubata (Source: F. Taraveau). Ticks are from the Neuchâtel strain (University of Neuchâtel, Switzerland), maintained at the insectarium from CIRAD (Montpellier, France) since 2008.

Figure 2

Map of South Africa representing the ASF controlled area and the locations where infected warthog and soft tick populations have been investigated and detected (Source: K. Rea).

Figure 3

Geographical localization of presence data for the Afrotropical soft tick vector of ASFV based on 574 occurrences published between 1873 and 2022 in East and Southern Africa. Species identification appears as referenced by the different authors (Source: H. Jourdan-Pineau).