Peste des Petits Ruminants Virus Infection at the Wildlife-Livestock Interface in the Greater Serengeti Ecosystem, 2015-2019

Abstract

Peste des petits ruminants (PPR) is a viral disease of goats and sheep that occurs in Africa, the Middle East and Asia with a severe impact on livelihoods and livestock trade. Many wild artiodactyls are susceptible to PPR virus (PPRV) infection, and some outbreaks have threatened endangered wild populations. The role of wild species in PPRV epidemiology is unclear, which is a knowledge gap for the Global Strategy for the Control and Eradication of PPR. These studies aimed to investigate PPRV infection in wild artiodactyls in the Greater Serengeti and Amboseli ecosystems of Kenya and Tanzania. Out of 132 animals purposively sampled in 2015-2016, 19.7% were PPRV seropositive by ID Screen PPR competition enzyme-linked immunosorbent assay (cELISA; IDvet, France) from the following species: African buffalo, wildebeest, topi, kongoni, Grant's gazelle, impala, Thomson's gazelle, warthog and gerenuk, while waterbuck and lesser kudu were seronegative. In 2018-2019, a cross-sectional survey of randomly selected African buffalo and Grant's gazelle herds was conducted. The weighted estimate of PPRV seroprevalence was 12.0% out of 191 African buffalo and 1.1% out of 139 Grant's gazelles. All ocular and nasal swabs and faeces were negative by PPRV real-time reverse transcription-polymerase chain reaction (RT-qPCR). Investigations of a PPR-like disease in sheep and goats confirmed PPRV circulation in the area by rapid detection test and/or RT-qPCR. These results demonstrated serological evidence of PPRV infection in wild artiodactyl species at the wildlife-livestock interface in this ecosystem where PPRV is endemic in domestic small ruminants. Exposure to PPRV could be via spillover from infected small ruminants or from transmission between wild animals, while the relatively low seroprevalence suggests that sustained transmission is unlikely. Further studies of other major wild artiodactyls in this ecosystem are required, such as impala, Thomson's gazelle and wildebeest.

Keywords: Kenya; PPR; Tanzania; epidemiology; eradication; goats; sheep; surveillance; transboundary animal disease; wild animals.

Figure 1

Map of the Greater Serengeti and Amboseli ecosystems showing protected areas and surrounding districts and counties in Tanzania and Kenya. Inset: map of Africa (Source: Map data © 2021 Google). The red dot indicates the location of the Greater Serengeti Ecosystem in northern Tanzania and southern Kenya.

Figure 2

Wet season distribution of: (a) African buffalo; (b) Grant’s gazelle in the Greater Serengeti ecosystem, 2014. Source of data: Tanzania Wildlife Research Institute and Kenya Wildlife Service aerial surveys and census data. Dots represent sightings of one or more animals: blue = African buffalo, green = Grant’s gazelle.

Figure 3

Map of Serengeti National Park showing locations where wildebeest faecal samples were collected in western Serengeti National Park and Grumeti Game Reserve, 2018.

Figure 4

Map of Ngorongoro District showing 2015 wildlife sampling sites in Loliondo Game Controlled Area (blue symbols), 2014 wildlife sampling sites in Ngorongoro Conservation Area (black symbols) [45] and locations of confirmed PPRV in domestic flocks in 2014 (purple dots) [45] and 2015 (red dots) [46].

Figure 5

Maps of the 2016 wildlife sampling sites in Kenya: (a) the Mara ecosystem; (b) the Amboseli ecosystem. Sampling sites of seropositive animals are shown by red symbols.

Figure 6

Peste des petits ruminants virus serology results by age, Kenya and Tanzania purposive wild animal sampling 2015–2016 (n = 123).

Figure 7

Distribution of peste des petits ruminants virus competitive enzyme-linked immune scheme 2018. (a) African buffalo; (b) Grant’s gazelle; (c) impala; (d) Thomson’s gazelle.

Figure 8

Map of sampling sites for the cross-sectional survey 2018–2019 indicating the proportion of cELISA positive animals at each site: (a) African buffalo; (b) Grant’s gazelle. Positive animals are those with percentage inhibition <50 (interpretation 1).

Figure 9

Map of the Greater Serengeti and Amboseli ecosystems showing locations of peste des petits ruminants virus (PPRV) positive and negative investigations of PPR-like disease reports in sheep and goat flocks, in relation to the 2018–2019 cross-sectional survey sampling sites and PPRV seroprevalence for African buffalo and Grant’s gazelle. Positive disease investigations were defined as at least one animal positive by PPRV rapid detection test and/or real-time reverse transcription-polymerase chain reaction.