Bovine Tuberculosis in African Wildlife Species
Although BTB in wildlife in Africa has been diagnosed in South Africa as long ago as the mid-1920s, the extent of the infection, and the ability of some of these infected species to act as maintenance hosts of the disease, only transpired recently.
The full extent of the infection in wildlife in Africa and the role that these infected species play in the epidemiology of the disease in cattle are unknown, but it is assumed that it is an increasingly expanding infection as is seen in wildlife in South Africa, where buffaloes, at least, appear not to have been infected before the mid-1950s in the KrugerNational Park (KNP) from where BTB spread to other species in the Park and in the surrounding areas.The slow, progressive nature of tuberculosis is characteristic of the development of the disease in individual animals, and of its relentless and progressive spread in free-ranging wild animal populations. The disease becomes established in an ecosystem only once a wildlife species with the ability to maintain the infection independently, and to transmit the infection to other susceptible animals within the specific ecosystem becomes infected. Many of the species that become infected are incidental (dead-end or spillover) hosts, and they are likely to play a very limited role in the epidemiology of BTB in these infected ecosystems.
In Africa, BTB both in cattle and in wildlife is underdiagnosed and underresearched, and its prevalence is largely unknown (de Garine-Wichatitsky et al. 2013; Ayele et al. 2004; FAO 2012). There is a substantial body of evidence suggesting that free-ranging wildlife species contracted BTB from cattle in many
Table 5.1 Notification and control status of BTB in countries in Africa that reported M. bovis in wildlife (2014)
| Country | BTB status cattle | BTB status wildlife | Notifiable cattle | Control cattle | Notifiable wildlife | Surveillance wildlife |
| Cameroon | + | + | Yes | Yes | No | No |
| Ghana | + | + | Yes | Yes | Yes | No |
| Mauritius | + | + | No | Yes | No | No |
| Mozambique | + | + | Yes | N/A | No | No |
| Nigeria | + | + | bgcolor=white>YesS | No | No | |
| South Africa | + | + | Yes | Yes | Yes | No |
| Sudan | + | + | Yes | N/A | Yes | Yes |
| Tanzania | + | + | Yes | S | Yes | Yes |
| Togo | + | + | Yes | N/A | No | No |
| Uganda | + | + | Yes | N/A | No | No |
| Zambia | + | + | Yes | No | No | No |
| Zimbabwe | Last reported 1996 | + | Yes | S | Yes | No |
+, BTB infection or disease present; N/A no information available, S surveillance
different countries including in Africa, and that this spillover infection often remains undetected for decades (Palmer et al.
2012). It is therefore not surprising that all 12 countries in Africa that reported M. bovis infection in wild animals between 2000 and 2014, also reported BTB in cattle, although not always concurrently (Table 5.1). The actual number of African countries in which BTB occurs both in cattle and wildlife is likely to be higher as no information is available for many of these countries (OIE 2017a). In addition, widespread intermingling of livestock and wildlife at the wildlife/livestock interface is common in large parts of Africa, and this is known to enhance the transmission of M. bovis especially during times when there is competition for limited pastures and water (Caron et al. 2013). A lack of diagnostic facilities to confirm the infection in remote wildlife areas is a further impediment to accurate reporting and the inadequacy of the available information.Of the 54 countries in Africa, BTB in cattle was reported in 89% (34/38) of those reporting disease information to the World Organization for Animal Health (OIE) between 2000 and 2014. No information was available for 13 countries, while one country reported absence and three countries had their last outbreak before 2000. Only those that reported the disease listed BTB as a notifiable disease in cattle and only nine of them require notification of BTB in wildlife (Table 5.2). Only 11 African countries have national BTB disease control policies and/or culling strategies (OIE 2017b) but prevention and control are often poorly implemented due to political, economical, and sociological constraints (Abdalla and Nganwa 2014; Awah- Ndukum et al. 2012).
In many countries, there are no regulations requiring the reporting of BTB outbreaks in wildlife. This is a hazardous practice since once the disease has established itself in a wildlife host, disease notification, surveillance, and monitoring to
Table 5.2 African wildlife species (excluding maintenance hosts) infected with Mycobacterium bovis
| Common name | Scientific name | Location | References |
| Common duiker | Sylvicapra grimmia | Agricultural farmland | Paine and Martinaglia (1929) |
| Lion | Panthera leo | GKNPC and other game parks, South Africa | Keet et al. (1996), Michel et al. (2006) and Hlokwe et al. (2011) |
| Cheetah | Acinonyx jubatus | GKNPC, South Africa | Keet et al. (1996) |
| Leopard | Panthera pardus | GKNPC, South Africa | De Vos et al. (2001) and Michel et al. (2006) |
| Lesser kudu | Tragelaphus imberbis | Northern Tanzania | Cleaveland et al. (2005) |
| Topi | Damaliscus lunatus | Northern Tanzania | Cleaveland et al. (2005) |
| Chacma baboon | Papio ursinus | GKNPC and other parks | Keet et al. (1996, 2000a) |
| Yellow baboon | Papio cynocephalus | Ruaha ecosystem, south-central Tanzania | Clifford et al. (2013) |
| Olive baboon | Papio cynocephalus anubis | Kenya | Tarara et al. (1985) |
| Kirk’s dik-dik | Madoqua kirkii | Ruaha ecosystem, south-central Tanzania | Clifford et al. (2013) |
| Vervet monkey | Chlorocebus pygerythrus | Ruaha ecosystem, south-central Tanzania | Clifford et al. (2013) |
| Honey badger | Mellivora capensis | GKNPC | Michel (2002) and Michel et al. (2006) |
| Large spotted genet | Genetta tigrina | GKNPC Ruaha ecosystem, south-central Tanzania | De Vos et al. (2001) and Clifford et al. (2013) |
| African civet | Civettictis civetta | Serengeti ecosystem, Tanzania | Katale et al. (2017) |
| Warthog | Phacochoerus africanus | Uganda South Africa (multiple locations) | Woodford (1982a, b), Kalema- Zikusoka et al. (2005) and Michel et al. (2009) |
| Bush pig | Potamochoerus larvatus | Hhluhluwe-iMfolozi Park, South Africa | Michel et al. (2009) |
| Impala | Aepyceros melampus | GKNPC South Africa Ruaha ecosystem, south-central Tanzania | Michel et al. (2006) and Clifford et al. (2013) |
| Bushbuck | Tragelaphus scriptus | GKNPC, South Africa | Hlokwe et al. (2014) |
(continued)
Table 5.2 (continued)
| Common name | Scientific name | Location | References |
| Eland | Taurotragus oryx | South Africa | Michel et al. (2006) |
| Blue wildebeest | Connochaetes taurinus | GKNPC, South Africa Northern Tanzania | Hlokwe et al. (2014) and Clifford et al. (2013) |
| Banded mongoose | bgcolor=white>Mungos mungoGKNPC, South Africa | Bruns et al. (2017) | |
| Giraffe | Giraffa camelopardalis | GKNPC, South Africa | TM Hlokwe, unpublished data (2013) |
| African wild dog | Lycaon pictus | GKNPC, South Africa | A Michel, unpublished data (2016) |
| Nyala | Tragelaphus angasii | South Africa | Hlokwe et al. (2014) |
| Black rhinoceros | Diceros bicornis | GKNPC, South Africa | Miller et al. (2017) |
| White rhinoceros | Ceratotherium simum | GKNPC, South Africa | P Buss, personal communication (2016) |
GKNPC Greater Kruger National Park Complex
determine spread of the disease in wildlife are needed to effectively manage the epidemic, and to protect livestock populations from spillback from the wildlife hosts. No information about the nature of the infection is available in most of the countries that reported BTB in wildlife to the OIE, as very few of the data have been published in scientific journals.
To date, BTB has been confirmed by culture in 29 free-ranging African wildlife species. Of those only African buffaloes (Syncerus caffer), greater kudus (Tragelaphus strepsiceros), and Kafue lechwe (Kobus leche kafuensis) are established maintenance hosts (Michel et al. 2006, 2015; Renwick et al. 2007; Munyeme et al. 2010; Clifford et al. 2013), but there are strong indications that warthogs (Phacochoerus africanus) and lions (Panthera leo) also have the potential to become maintenance hosts (Michel et al. 2015). The remainder of the species is considered to be spillover species (Table 5.2).
The characteristics of BTB in the maintenance hosts, and those that have the potential to become maintenance hosts are described in this chapter.