The role of African wildlife in the occurrence of vector-borne infections in domestic
animals has gained renewed interest as emerging and re-emerging infections
occur worldwide at an increasing rate. In Africa, biodiversity conservation and
the expansion of livestock production have increased the risk of transmitting
vector-borne infections between wildlife and livestock. The indigenous African
pathogens with transboundary potential, such as Rift Valley fever virus, African
horse sickness virus, bluetongue virus, lumpy skin disease virus, African swine
fever virus, and blood-borne parasites have received the most attention.
There is no evidence for persistent vector-borne viral infections in African wildlife.
For some viral infections, wildlife may act as a reservoir through the inter-epidemic
circulation of viruses with mild or subclinical manifestations. Wildlife may also
act as introductory or transporting hosts when moved to new regions, e.g. for
lumpy skin disease virus, Rift Valley fever virus and West Nile virus. Wildlife may
also act as amplifying hosts when exposed to viruses in the early part of the warm
season when vectors are active, with spillover to domestic animals later in the
season, e.g. with bluetongue and African horse sickness.
Some tick species found on domestic animals are more abundant on wildlife hosts;
some depend on wildlife hosts to complete their life cycle. Since the endemic
stability of a disease depends on a sufficiently large tick population to ensure
that domestic animals become infected at an early age, the presence of wildlife
hosts that augment tick numbers may be beneficial. Many wild ungulate species
are reservoirs of Anaplasma spp., while the role of wildlife in the epidemiology
of heartwater (Ehrlichia ruminantium infection) has not been elucidated. Wild
ungulates are not usually reservoirs of piroplasms that affect livestock; however,
there are two exceptions: zebra, which are reservoirs of Babesia caballi and Theileria equi, and buffalo, which are reservoirs of Theileria parva. The latter
causes Corridor disease when transmitted from buffalo to cattle, but this appears to
be a self-limiting condition, at least in southern Africa. Wild animals are important
reservoirs of tsetse-transmitted Trypanosoma spp. infection. The distribution and
abundance of some tsetse species, e.g. Glossina morsitans and G. pallidipes, are
closely related to the occurrence of their preferred wildlife hosts.