Seroprevalence of brucellosis in cattle and selected wildlife species at selected livestock/wildlife interface areas of the Gonarezhou National Park, Zimbabwe
Introduction
Brucellosis is a disease of animals caused by bacteria of the genus Brucella, which comprises 11 species recognized according to their pathogenicity and host preference (Whatmore et al., 2014). In cattle, the main pathogenic species occurring worldwide is B. abortus, responsible for bovine brucellosis. However, B. melitensis may occasionally cause brucellosis in cattle that are co-managed with infected goats and/or sheep.The most important clinical sign of bovine brucellosis is abortion at first gestation. Usually, infected females will abort once, although they may remain infected for their entire life. The clinical diagnosis of brucellosis in cows on the basis of abortion is, however, equivocal since many pathogens can induce abortion. Hence, laboratory testing, especially culture and isolation of Brucella species is required to provide an unequivocal diagnosis of brucellosis. The economic importance of brucellosis is that when it is detected in a herd, flock, region, or country, international veterinary regulations impose restrictions on animal movements and traderesultingin huge economic losses. Additional economic losses occur due to decreased milk production, loss of calves and culling.
All Brucella species may also infect wildlife species. Classical Brucella species have been isolated from a great variety of wildlife species such as bison (Bison bison), elk (Cervus canadensis), wild boar (Sus scrofa), fox (Vulpes vulpes), hare (Lepus europaeus), and caribou (Rangifer tarandus) (Godfroid, 2002). In Southern Africa, Brucella species have been isolated from the African buffalo (Syncerus caffer), impala (Aepyceros melampus), eland (Tragelaphus oryx) and waterbuck (Kobus ellipsipymnus) among others (Condy and Vickers, 1969, Gradwell et al., 1977, Schiemann and Staak, 1971). In order to implement appropriate control measures to address wildlife brucellosis, it is very important to distinguish between a spill-over of infection contracted from domestic animals and a sustainable infection (Godfroid, 2002). In the latter case, the concern of the livestock industry is to prevent the re-introduction of the infection in livestock (spill-back), particularly in regionsthat are “officially brucellosis-free.”
Brucellosis is an established zoonosis with incidence of human brucellosis directly related to the prevalence of infections in animals. Although B. melitensis exhibits the highest pathogenicity, human infections are frequently attributed to B. abortus, followed by B. melitensis and B. suis, respectively, and occasionally B. canis. Studies from around the world indicate that elimination of the animal brucellosis reservoir has resulted in a substantial decline in the incidence of human disease (Pappas et al., 2006).
The Great Limpopo Transfrontier Conservation Area (GLTFCA) was created in 2002 to co-manage as one ecological unit, the several national parks, communal lands, and private lands located in Mozambique, South Africa and Zimbabwe (Cumming, 2004). In Zimbabwe, Gonarezhou National Park (GNP), a semi-arid ecosystem, and the communal areas on its periphery are part of the GLTFCA.Because of the low rainfall experienced in these interface areas, communities rely more heavily on livestock production for their livelihoods compared to rain-fed crop production. Livestock provide a vital source of milk, meat, income, draught power for land tillage, transport and manure, in addition to their use in numerous social and cultural roles (Muma et al., 2006). Production of livestock is however hampered by diseases that areinadequatelycontrolled by veterinary institutions (Caron et al., 2013, Ndengu et al., 2017) and often perceived by the communities to be originating from the adjacent wildlife (de Garine-Wichatitsky et al., 2013a), including infectious causes of abortions (Ndengu et al., 2017). The establishment of regional transfrontier wildlife conservation areas, such as the GLTFCA together with the disruption of fences erected as part of foot and mouth disease (FMD) control measures have resulted in increased livestock-wildlife contact and heightening the tension between humans and wildlife (de Garine-Wichatitsky et al., 2013b). Moreover, these communities often consume raw milk; handle abortion products without protection and hunt wildlife for consumption making them prone to zoonoses including brucellosis (Gadaga et al., 2016, Ndengu et al., 2017). The risk for human morbidity from brucellosis in the GLTFCA has been demonstrated, as previous research has highlighted the existence of brucellosis in some of these animal hosts including wildlife (Gomo et al., 2012a, Gomo et al., 2012b; Caron et al. 2013; Madison and Anderson, 1995; Motsi et al., 2013). Therefore, owing to the increased human-domestic animals-wildlife contact in these areas and the increased dependence of the communities on animals and animal products for food, it is imperative to understand animal brucellosis in order to highlight the associated public health risks. The results of such studies may help to advise on control programmes for both animal and human brucellosis, mitigate against human/wildlife conflicts and promote wildlife biodiversity conservation.
The aims of this study were:
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To determine the sero-prevalence and risk factors of cattle brucellosis in selected communities at the periphery of the GLTFCA.
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To determine the sero-prevalence and risk factors of brucellosis in some selected wildlife species in the Gonarezhou National Park which is part of the GLTFCA
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To establish if exposure to wildlife is a risk factor for cattle brucellosis by comparing the brucellosis sero-prevalence in cattle in the communities representing three distinct areas of unrestricted (porous), restricted by fencing (non-porous) livestock-wildlife interface and non-interface (absent) areas.
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To investigate if any such risk of cattle brucellosis due to exposure to wildlife is supported by wildlife seropositivity.
Section snippets
Study area
The study areas are located in the South East Lowveld (SEL) of Zimbabwe which lies in agro-ecological Natural Region Vthat is characterized by low elevations, high temperatures, and low and erratic rainfall (on average <600 mmper year) (Gandiwa and Zisadza, 2010). The selected study sites (Fig. 1) comprised of a livestock-wildlife interface where there is contact between domestic and wild animals and the non-interface areas where interaction between domestic and wild animals is absent as
Cattle seroprevalence
A total of 1011 cattle were sampled with 46.7% (472/1011) from the porous interface (Malipati), 28.2% (285/1011) from the non-porous interface (Chizvirizvi) and 25.1% (254/1011) from the non-interface area (Chomupani) (Table 1). The overall seroprevalence of brucellosis from all areas was 16.7% (169/1011; 95% CI: 14.5–19.2%). The porous interface recorded a significantly (p = 0.03) higher seroprevalence (19.5%; 95% CI: 16.1–23.4%) compared to the non-interface area (13.0%; 95% CI: 9.2–19.9%).
Discussion
In this paper, we report the serological evidence of brucellosis infection in cattle and wildlife on the Zimbabwean side of the GLTCA. The RBT is a very sensitive test for detection of antibodies against Brucella species in cattle while the CFT is very specific (OIE, 2016) thus reducing the possibility of false negative and false positive reactions, respectively. Both tests are OIE prescribed and therefore augment the reliability of our test results, especially given that a serial testing
Conclusions
Brucellosis is indeed prevalent in cattle and buffalo at the periphery of the GLTFCA as evidenced by this study. It is therefore incumbent upon all authorities including the Departments of Veterinary Services, Parks and Wildlife Management Authority and The Ministry of Health and Child Care to improve their surveillance systems and to disseminate information to other relevant stakeholders in order to curtail the negative effects of this important zoonosis. Further research is necessary to
Acknowledgements
We thank the Ministère Français des AffairesEtrangères for supporting Masimba Ndengu’s research through the FSP-RenCaRe project (FSP no2011/36). This work was conducted within the framework of the Research Platform ‘Production and Conservation in Partnership’ (http://www.rp-pcp.org). We thank the farmers from Malipati, Chomupani and Chizvirizvi, and the staff of the Veterinary Services and National Parks and Wildlife Management Authority (Gonarezhou NP) for their collaboration.
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