Preliminary Study on the Prevalence of Bovine Tuberculosis and Risk Factors among Pastoralists in Gombe State, North Eastern Nigeria

Abstract

A cross-sectional study was conducted in GombeState (North- eastern, Nigeria) from March, 2011 to April 2013 to estimate the prevalence of bovine tuberculosis (BTB) based on single caudal intradermal tuberculin test (SCITT), questionnaire and an abattoirs survey. The study was conducted among 250 households (100 household with a history or confirmed case of pulmonary tuberculosis and 150 households who had no history or confirmed case of pulmonary Tb), who raised 217 herds comprising of 2,245 herds of cattle. Questionnaire administration and Bioline® analysis of sputa collected from all pastoralists who were suspected to have TB and were smear positive were also conducted. Herd prevalence of SCITT was 13.87% and was higher than in herds of the negative households. At least one human Tb case was observed among 25% of the households interviewed, whereas 48% had reactor cattle. However, there was no statistically significant association (P>0.05) between the human Tb cases observed and the presence of reactor cattle. Similarly, fourty (40) isolates of Mycobacteria spp were obtained from the cultured sputa collected from the pastoralists, and were subjected to Ziehl-Nelson (ZN) and Bioline® analysis, where sixteen (16) of the (40%) were found to be M. tuberculosis complex (MTC) and the remaining 24 (60%) were members of Non- tuberculous Mycobacteria (NTM). All the isolates obtained (both sputum and tissues) which were identified as MBTC, were subjected to genotype MBTC ® Hain assay PCR analysis in order to differentiate them in to their various species of the MBTC isolates from the tissues, 8 (4.0%) were found to be M. bovis, 5(2.5%) wereM.tb and the remaining 5(2.5%) were unidentified using the standard banding patterns. The 40MBTC from sputum were analyzed as follows, 30 (75%) as M.tb, 6(15%) were M. bovis and 3(7.5%) were M. africanum. The remaining 1(0.4%) were unidentified using the standard banding patterns. All the isolates obtained (both sputum and tissues) which were identified as MBTC, were subjected to genotype MBTC ® Hain assay PCR analysis in order to differentiate them in to their various species of the MBTC isolates from the tissues, 8 (4.0%) were found to be M. bovis, 5(2.5%) wereM. tb and the remaining 5(2.5%) were unidentified using the standard banding patterns. The 40MBTC from sputum were analyzed as follows, 30 (75%) as M.tb, 6(15%) were M. bovis and 3(7.5%) were M. africanum. The remaining 1(0.4%) were unidentified using the standard banding patterns. However, a significant difference (p>0.05) was observed among the cattle age group, cattle over five (5) years were seen to have higher odds for tuberculin reactivity compared to those below the age of five (5). Out of the total cattle population (57,943) subjected to post mortem examination at the abattoir, 205 were found to be positive for gross Tb lesions, where a large proportion (50%) of the lesions were recorded in the respiratory pathway, digestive system (21%) and prescapular lymph nodes (18.6%). In spite of all these findings, it was observed that 70% (175 out of 250) of the respondents had knowledge of the existence of the disease but did not know the zoonotic implication. Also, all the potential risk factors of the disease transmission between cattle and human (milk consumption, livestock husbandry and presence of Tb positive cattle) were not statistically significantly (P< 0.05). In conclusion, it was observed that cattle belonging to the pastoralists who were positive for Mycobacterium species were more affected than those who were negative and lack of zoonotic awareness of the households. Therefore, further study to differentiate the MTC (Mycobacterium tuberculosis complex) using molecular analysis, collaboration between physicians and veterinarians and creation of awareness about the zoonotic nature of the disease were recommended.