Elsevier

Acta Tropica

Volume 149, September 2015, Pages 38-44
Acta Tropica

Selective breeding: The future of TB management in African buffalo?

https://doi.org/10.1016/j.actatropica.2015.05.012Get rights and content

Highlights

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    High BTB prevalence in buffalo has economic, ecological and public health impacts.

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    Test and cull methods to reduce BTB may not be feasible in free-range wildlife systems.

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    Breeding for BTB resistance may be a viable alternative method of management.

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    We discuss selective breeding methods and consider their suitability for buffalo.

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    We address the challenges of this approach and present implications for management.

Abstract

The high prevalence of bovine tuberculosis (BTB) in African buffalo (Syncerus caffer) in regions of southern African has a negative economic impact on the trade of animals and animal products, represents an ecological threat to biodiversity, and poses a health risk to local communities through the wildlife-cattle-human interface. Test and cull methods may not be logistically feasible in many free-range wildlife systems, and with the presence of co-existing BTB hosts and the limited effectiveness of the BCG vaccine in buffalo, there is a need for alternative methods of BTB management. Selective breeding for increased resistance to BTB in buffalo may be a viable method of BTB management in the future, particularly if genetic information can be incorporated into these schemes. To explore this possibility, we discuss the different strategies that can be employed in selective breeding programmes, and consider the implementation of genetic improvement schemes. We reflect on the suitability of applying this strategy for enhanced BTB resistance in African buffalo, and address the challenges of this approach that must be taken into account. Conclusions and the implications for management are presented.

Section snippets

Resistance vs tolerance

Resistance and tolerance are the two main aspects of defence against pathogens, and together determine disease severity (Råberg et al., 2007). Whilst resistance involves limiting the bacterial burden and has been shown to exhibit substantial genetic variation in animal models, tolerance is the restriction of the harmful consequences caused by the bacteria (Stear et al., 2001, Råberg et al., 2007). Resistance and tolerance have been shown to be negatively correlated in infectious disease, with a

Types of selective breeding

Selective breeding programmes seek to identify individuals with a particular trait of interest, and preferentially utilize those individuals for breeding. Over time, the trait variant will become more prevalent in a particular population. Selection for health and reproductive traits has occurred in breeding programs for centuries, but disease traits have been incorporated only recently. Despite relatively low heritability estimates, breeding programs have been successfully implemented for

Implementing genetic improvement strategies

One of the most crucial parameters in any selective breeding programmes is heritability, as it provides an indication of the potential success of this strategy for a particular trait. The higher the heritability score, the greater the role that genetics plays in determining the phenotype and the more potentially enhanceable the trait is through selective breeding (Falconer and Mackay, 1996). The heritability of resistance to BTB infection in cattle and wildlife species has been calculated in a

Application of selective breeding in African buffalo

To date, selective buffalo breeding in South Africa has been based on phenotypic merit. In order to increase the improvements seen thus far, genetic information could be incorporated into breeding values, using either a marker-assisted or genomic selection approach. Buffalo genetic research in the past has predominantly focused on population genetics, although studies in disease genetics have become more frequent. A recent association study tested 69 SNPs in immune-related genes in buffalo for

Challenges and considerations

Selective breeding programmes operate optimally with additional management practices, such as frequent testing and status monitoring, quarantine and treatment of sick animals with antibiotics, but these practices are not possible in a free-ranging environment, such as national parks. In order to implement these practices, wildlife populations such as buffalo would need to be maintained in a fenced environment under controlled conditions, similar to that of cattle. This practice has other

Conclusions

The African buffalo is a species of great importance in southern Africa, particularly in the tourism, hunting and commercial game farming industries. This creates a constant demand for buffalo, and prices have continued to increase accordingly. The market value of buffalo within South Africa varies according to disease status, with ‘disease-free’ buffalo valued at approximately 10 times that of their counterparts at auction; in 2013, the Cape buffalo ‘Mystery’ was sold at a game auction in

Management implications

While selective breeding for enhanced BTB resistance in African buffalo may offer increased protection, this strategy is unlikely to confer complete resistance to BTB. As such, management strategies should be designed to incorporate selective breeding as a publicly acceptable and feasible method of control, in conjunction with other disease management efforts, such as test and cull programmes. In addition, as M. bovis is capable of infecting numerous species other than buffalo, decisions must

Conflict of interest

The authors have no conflict of interest to declare.

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