Limitations and Opportunities for the Use of Molecular Epidemiological Tools in Africa
8.8.1 Limitations
8.8.1.1 Lack of or Inadequate Disease Control and Eradication Policies
Having a well-thought-out and achievable livestock disease control policy is critical not only for achieving maximum benefits from the livestock industry but also for safeguarding consumers’ health and the national economy.
Disease control and prevention policies pertinent to infectious diseases need to embrace, among other mitigations:1. Mandatory isolation and quarantine measures
2. Strict import and export regulations
3. Restriction of uncontrolled movement of animals between farms and locations
4. Establishing surveillance and monitoring activities including keeping records of animal health status
5. Identification of individual animals
6. Adequate biosecurity and maintenance of sanitation
Distinctive features of BTB that include its high economic impact, zoonotic transmission, involvement of multiple hosts, complex ecology, chronic course of infection, and difficulty to diagnose unquestionably demand special consideration in designing and implementing a sustainable national BTB control policy.
However, to date, only few countries in Africa have adopted and implemented a functional national BTB control policy. According to an assessment by Cosivi et al. (1995), BTB control is almost nonexistent in the majority of dairy and other cattle on the African continent. The BTB control policy gap in Africa extends across all activities, including the absence of regular tuberculin testing, slaughtering of testpositive animals, extensive uncontrolled movement of livestock, lack of contact tracing, and absence of abattoir surveillance. It is perplexing to conduct an epidemiological investigation of BTB under these circumstances since the findings are ultimately shelved and not implemented, due to the absence of an appropriate disease control policy.
8.8.1.2 Absence of a Continental Reference Database and Laboratory Capacity for Mycobacterial Genotype Characterization
Because of the lack of control policies, there is an inherent disparity and weakness in surveillance standards among countries, which compromise the source and quality of specimens from which M. bovis could be isolated for molecular epidemiological discourse. There has been some work carried out in laboratories in Africa on the presence and distribution of M. bovis, funded by the European Research Council, but it is critical to note that there is not an established central collaborative laboratory in Africa as is the case for other continents. The current situation is probably also responsible for the lack of a critical mass of professionals required to sustain the discipline of molecular epidemiology in Africa.
8.8.1.3 Weak Transdisciplinary and Interlaboratory Collaboration
The discipline of molecular genetics gendered enormous support and collaboration by a wide range of disciplines to unravel the intricate interaction between host, pathogen, and environment and the resultant diseases and complications that threaten the existence of humans and animals. Unlike with conventional epidemiology, with molecular epidemiology there is extensive collaboration with various professionals such as statisticians, environmental experts, industrial hygienists, clinicians, biochemists, molecular biologists, geneticists, pathologists, and immunologists (Schulte and Perera 1993). This interdisciplinary network in most African countries is in its nascent stage, and it is not robust enough to generate the critical mass required to sustain this discipline.
The distinctive pathobiological features of BTB, including its chronic course, an almost unlimited host range, various routes of transmission, lack of an effective vaccine, difficulty to accurately diagnose the infection, and its impacts on both animal and human health, support the case for transdisciplinary collaboration between veterinarians, physicians, economists, microbiologists, and public health and environmental science experts.
8.8.2 Opportunities
Most African countries do not have state-of-the-art veterinary diagnostic facilities to routinely make definitive diagnoses, but they rely on submitting samples or isolates to laboratories in Europe or the United States to confirm certain diseases or conditions.
Although this has some drawbacks, such collaboration also has benefits that allow technology transfer, producing skilled professionals and establishing laboratory facilities to do molecular typing of mycobacteria, in addition to providing invaluable insight into the molecular genetics and epidemiology of mycobacterial diseases, especially of the MTC organisms. A good example of the outcome of such a joint venture is the recent identification of the two major clonal complexes of M. bovis strains, Africa 1 (Af1) and Africa 2 (Af2). The typing process involved collecting M. bovis isolates from various countries in Africa and transporting them to a number of laboratories abroad, including the Animal Health and Veterinary Laboratories Agency (VLA), Weybridge, United Kingdom, for molecular typing (spoligotyping, VNTR typing, deletion analysis, and IS6110 RFLP typing). In addition to creating further opportunities for collaboration, the findings of the study revealed important insights into the phylogeography of M. bovis including the detection of distinct clonal complexes in Western (Af1) and Eastern Africa (Af2).There is a need to emphasize the weak capacity in pathobiological diagnostics of disease, as this is likely to attract the much-needed funding to complement clinical- and public health-based research at the animal-human interface. Investment in pathobiological capacity would inherently lead to the development of biobanks of pathogens from animals and humans at the human-animal interface. This would give most African countries better opportunities to collaborate and share their experiences allowing them to build and strengthen technical capacity that include skilled manpower and facilities to conduct molecular typing and epidemiologic analyses of the causes of the mycobacterial diseases. Furthermore, such a resource will serve many purposes including innovation in diagnostic and vaccination technologies, standardization of genotyping methods to support the long-term goal of controlling, and eradicating TB both from animals and humans on the African continent.
8.8.3 Future Challenges
The contribution of zoonotic TB to human TB is poorly investigated particularly in sub-Saharan Africa, where a combination of endemic BTB, an expanding humananimal interface, an expanding dairy industry, the lack of appropriate diagnostic tools, and cultural norms that discourage health-seeking behavior present considerable challenges to poor communities. This complex of the drivers of the disease is likely to hamper progress toward achieving the World Health Organization’s ambitious goal of eliminating TB by 2035. This, in effect, means that now more than ever, it is imperative to be able to make a definitive diagnosis in each case when dealing with TB, regardless of the causative agent, as each individual case matters if eradication is to be successful. Without the much-needed investment in developing faster and cheaper molecular assays, it will be difficult to properly understand this ever-changing landscape of TB in general, but specifically, BTB and zoonotic TB in Africa.
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