Molecular Epidemiology of BTB in Nigeria

Despite the evidence of BTB being present in Nigeria from early 1929 (Alhaji 1976), some insight into the molecular epidemiology of the disease was reported only in 2004 (Cadmus et al.

Fig. 17.1 Map of Nigeria showing the different states where BTB investigations using different diagnostic methods have been conducted

370 S. I. B. Cadmus

related group of M. tuberculosis strains. It was further shown by deletion typing that approximately 10% of the human TB cases were caused by strains of M. africanum and 5% by M. bovis.

Earlier preliminary data had shown the circulation of similar strains of M. bovis in a private cattle herd in Ibadan, South-western Nigeria (Cadmus et al. 2004), re-affirming the usefulness of molecular epidemiology as a tool to track specific strains of pathogens to understand the transmission of disease in different populations.

To date, the majority of the MTC species isolated from cattle in Nigeria have been confirmed by spoligotyping to be M. bovis (Cadmus et al. 2006, 2011; Abubakar 2007), with the SB0944 strain being the most frequent spoligotype circulating in the country. Several strains of M. africanum (lacking spacers 8, 9, and 39) have also been isolated from tuberculous cattle (Cadmus et al. 2006, 2011; Abubakar 2007). Cadmus et al. (2006) and Abubakar (2007) also detected M. tuberculosis (intact spacers 39 through 43) in slaughtered cattle in Nigeria using molecular tools like spoligotyping, VNTR (Streicher et al. 2007) and deletion typing (Cadmus et al.

2006).

Molecular epidemiology, using VNTR and MIRU-VNTR, further showed a large diversity in the strains of M. bovis in Nigeria (Cadmus et al. 2006, 2011, 2008), although most M. bovis strains isolated in Nigeria belong to the African 1 (Af1) clonal complex. The Af1 clonal complex is a group defined by a specific chromo­somal deletion (RDAf1), and lacking spacer 30 using the standard spoligotype pattern (Muller et al. 2009), and its occurrence is limited to the West-Central African region compared to strains circulating in Eastern Africa and Europe (Muller et al.

2009). Though there have been several efforts to decipher the epidemiology of M. bovis in cattle and other animals in Nigeria using different molecular techniques (Cadmus et al. 2006, 2011; Abubakar 2007; Jenkins et al. 2011), there is still a huge information gap. Inadequate veterinary infrastructure, insufficient and inadequately trained personnel, and most importantly, the lack of funding to support animal health delivery are some of the factors militating against proper investigations into the molecular epidemiology of BTB in Nigeria.

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