PPR Infection crossing between domestic and wild hoofed mammals: Does this matter for virus eradication?

The epidemiological role of wildlife in peste des petits ruminants (PPR) has been recently confirmed by (1) emerging evidence for infection and epidemics in wild populations, especially following spillover of virus from domestic to wild species at the wildlife and livestock interface; (2) extensive evidence for PPR-induced pathology in wildlife species; and (3) spread of virus across landscapes independently of livestock. However, the pathogenesis of the virus in wildlife species and risk factors for disease remain poorly understood, whilst its impact on wildlife populations should not be underestimated and adds justification for its eradication. Nowadays, with a few exceptions, susceptible wildlife species mostly occur in remnant small populations, surviving in protected areas or remote isolated pockets, amounting to rarely more than tens of thousands of individuals, a situation that contrasts with the ubiquitous abundant domestic sheep and goat populations which occur in billions. In the context of an appropriate intensive small ruminant vaccination programme, infected wildlife should therefore not prevent the elimination of the virus from ecosystems. Exceptionally, some wildlife populations might provide an alternative transmission pathway for the virus to, and between, small domestic ruminants and potentially be part of the maintenance community for the virus (i.e. PPR episystems). In these cases, wildlife may be required to be incorporated more specifically into strategies for eradication using approaches that limit impacts on wildlife species conservation. In fact, wildlife and perhaps some atypical domestic animal hosts will provide useful sentinels during the process of eradication and should be a part of surveillance activities for PPR, enhancing the process to elimination. Before this can be done effectively, validated test protocols for identifying PPR antibodies in the sera of wildlife and atypical domestic host species need to be established. Whether the situation will be similar to rinderpest, where wildlife disease was not controlled and burned out in the absence of virus spillover from livestock, remains uncertain, whilst evidence is building to support this hypothesis. Eradication campaigns should move as rapidly as possible along the pathway for both reasons of livestock economy and conservation of biodiversity.