Risk Factors of BTB in Nigeria

A host of risk factors influence the occurrence and spread of the disease in the Nigerian cattle population. They do not all equally apply to the different manage­ment systems, but they do play a substantial role in each of the specific situations.

Peri-Urban and Rural (Pastoral) Animal Husbandry Reports about the cases of BTB in private herds in urban centers in Nigeria (Manley 1929; Ibrahim et al. 2012; Cadmus 2010) support the contention that intensive husbandry is a major risk factor for BTB. Cases of BTB, however, have also been reported in pastoral herds (Cadmus

2010). Over the years, with a fast-growing population, Nigeria has been faced with an increasing demand for animal protein. In the same vein, because of the huge socio-economic pressure on the middle class, there has been a quest for increased personal wealth. This has led to a gradual, but steady shift of animal husbandry from the traditional pastoral system to peri-urban and urban dairy production (mostly operated by civil servants with animals that are reared in living quarters in a semi- intensive management system, and graze within the confines of the owners’ properties).

Poor Animal Health Infrastructure and Services Due to limited financial resources and other higher priorities, the livestock sector has received very little attention from the Nigerian government, and livestock production in Nigeria remains underdeveloped. Consequently, almost 95% of the cattle population remains in the extensive management system practiced by the Fulani pastoralists, a group of people that is poorly exposed to modern animal health services, and disease prevention and control strategies. Consequently, routine chemo-prophylactic measures and vacci­nation efforts are not often embraced. Therefore, BTB surveillance, prevention, and control activities involving the TST are seldom performed and viewed with serious mistrust by the pastoralists, and in several cases prohibited.

Laboratory Infrastructure Currently, in Nigeria, only about two to three labo­ratories have the infrastructure required to carry out laboratory procedures such as culture and molecular identification of M. bovis. These facilities also have limited capabilities to carry out modern techniques like the MIRU-VNTR, single nucleotide polymorphisms (SNPs) and whole genome sequencing (WGS). Therefore, labo­ratory facilities to carry out prompt and correct confirmation of BTB in infected animals are highly limited and still in their rudimentary stages of development.

Personnel Due to limited governmental support and the lack of funding for BTB surveillance in Nigeria, very little research work is carried out. Additionally, we do not have adequately trained human resources to effectively carry out TSTs of Nigerian cattle herds. In the same vein, there are very few meat inspectors who are employed to carry out the necessary meat inspection services. Hence, tuberculous carcasses and contaminated meat from slaughter slabs and abattoirs are sold to the unsuspecting public.

Non-tuberculous Mycobacteria (NTM) Being unable to accurately differentiate between cases of BTB and those infected with NTMs during meat inspection compounds the problem of BTB in Nigeria. Cases of NTM infections have been reported following preliminary investigations in Nigerian abattoirs (Ejeh et al.

Infection of Cattle with Other Strains of the M. tuberculosis Complex Of particular importance is the emerging recognition that cattle across Nigeria are susceptible to infection by other members of the MTC (Cadmus et al. 2006; Abubakar 2007; Raufu and Ameh 2010). Cases of M. tuberculosis (Cadmus et al. 2006; Raufu and Ameh 2010) and M. africanum infection (Abubakar 2007; Raufu and Ameh 2010) in different parts of the country have been reported. These findings make the epidemiology of BTB in Nigeria more intriguing and complex given the public health implications created by these infections.

Lack of BTB Control Policies In general, there are limited funding and policy guidelines from the government to support the livestock sector. There are no formal operational guidelines or codes of conduct dealing with the registration of cattle herds, their physical location, bio-security, or minimum health standards. Thus, issues relating to surveillance of trans-boundary animal diseases of economic and public health importance, compulsory vaccination to control major epidemics, and a test-and-slaughter policy to eradicate diseases are given little or no attention. Con­sequently, surveillance measures to monitor BTB in the Nigerian cattle herds and trade animals (especially those imported into the country), and prevention of its introduction and spread within the country have not been established. This has led to several illegal/unwholesome activities and practices in the Nigerian cattle industry. Consequently, animal movement in and out of Nigeria, across and within different states, and between healthy and infected herds is unrestricted, and there is practically no policy or coordinated effort to control BTB (Cadmus 2010). Likewise, dairy animals are also imported into the country without prior screening for or providing a valid record of their BTB status.

Additionally, there is no national TST program to assess the overall burden of BTB in Nigerian cattle herds. To worsen the situation, the numbers of trained veterinarians and meat inspection officers available in most abattoirs/slaughter slabs are insufficient to conduct adequate meat inspection. Therefore, the data generated on BTB are not comprehensive, and often poorly analyzed, and are inadequate to inform government on the burden of the disease. This makes it difficult to formulate a long-term control policy, as currently it would be based mostly on anecdotal information. Consequently, poor control and policy measures against BTB, including the lack of compensation to butchers, affect all stakeholders (Ejeh et al. 2014a) and result in the ongoing exposure of the public to M. bovis- infected carcasses.

International and Intra-country Movement of Animals There is no official BTB control policy in Nigeria or in its neighboring African countries. Because of the unrestricted and uncontrolled continuous in-flow of animals, Nigeria has become a large receptacle of M. bovis-infected cattle from neighboring countries, and local cattle herds are at an increased risk of being infected with M. bovis. As a result, diverse strains of M. bovis are isolated from tuberculous cattle originating from Niger, Mali, Chad, and Cameroon that are slaughtered at abattoirs around the country (Cadmus et al. 2006; Muller et al. 2009).

Cultural Values and Practices The traditional Fulani pastoralists, who own the bulk of the cattle in Nigeria, engage in practices that expose their animals to adverse health conditions due, largely, to their transhumant lifestyle. Each year, the animals are driven over several hundred to thousands of kilometers in search of pasture and water. During this migration, in most instances, the animals are poorly fed, they lack veterinary care, and they are often fatigued, making them more vulnerable to contracting various diseases including BTB.

Lack of Awareness and Illiteracy Due largely to the poor knowledge by the general public about the health risks associated with BTB, and the high level of illiteracy among major stakeholders in the livestock industry, several risky practices that foster the spread of BTB persist in the livestock production chain in Nigeria (Cadmus 2010):

• For example, the uncontrolled movement of cattle over long distances and their comingling around the few watering and salt lick points without any biosafety measures constitute some of the major drivers of the spread of BTB in those herds.

• Another very important risk factor is the intensification of cattle production by individuals in urban areas (mostly government employees) who rear them in their backyards for fattening and sales to generate an extra income. Sadly, some traders in the livestock market keep their animals within their living areas, oblivious of the risk posed by their close association with cattle infected with M. bovis.

Cumulatively, these practices lead to cross-contamination and the spread of infection within the cattle populations, and in some instances, to zoonotic transmis­sion (Cadmus et al. 2006).

Eating Habits Consumption of unpasteurized milk and milk products has been identified as the major route of human infection with M. bovis. In Nigeria, some of the milk consumed is skimmed, soured, and consumed unpasteurized (Alhaji 1976). There are several reports about the presence of M. bovis in cows’ milk being drunk directly after it was expressed from the udder (Cadmus et al. 2008), and from milk sold on the open markets in Northern (Abubakar 2007) and South-western Nigeria (Cadmus et al. 2008).

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