EPIDEMIOLOGY OF HUMAN AND BOVINE TUBERCULOSIS IN THE FEDERAL CAPITAL TERRITORY AND KADUNA STATE OF NIGERIA

Abstract

The epidemiology of bovine and human tuberculosis (TB) was studied in the Federal Capital Territory and Kaduna state of Nigeria using four diagnostic methods; tuberculin test, culture and acid-fast stain of milk, animal (cattle) tissue and human sputum. Two PCR-based molecular techniques (Spoligotyping and Variable Number Tandem Repeat) were used to identify the species and strains of the isolates, while IS61 10-RFLP molecular method was optimised and applied on few samples to deten-nine the efficacy of the method. Of the 967 lactating cows from 57 herds tested for TB, 14.6%, 4% and 81.4% were positive, inconclusive and negative reactors respectively. Tuberculin test also showed that mycobacterial infection was prevalent iii the two management systems studied (nomadic and semi-nomadic), but the effect of management on the prevalence of infection was not significant. However, age was found to play a significant role in the prevalence infection where more positive cases were observed among the older age groups. It was also observed that control policy is either not in place or inadequately implemented in the study area. Of the 156 milk samples collected, 12.6% and 23% were culture and acid-fast positive respectively, while out of the 250 tissue samples 17.3% and 20% were culture and acid-fast positivc respectively. Thii s findiInIIg confirmed a definite relationship between the disease in live and slaughtered cattle. Comparing the three diagnostic methods in 4 detecting mycobacterial infection in cattle, the smear method was found to have detected more positive cases than the tuberculin and culture tests. Of the 900 suspected human TB patients investigated, 27% and 21 A% were culture and acid-fast positive respectively. This trend of high prevalence of TB among human patients in the area is similar to the trend observed among cattle populations; thus indicating a relationship between the disease in human and infection in cattle. In addition, a significant difference in the prevalence of the disease was observed between male and female patients with more positive cases observed among male patients. The prevalence of the disease was aslso found to be significantly higher in patients who did not have BCG vaccination in the past than those who had. It was also observed that the disease was higher in patients who consume raw milk and milk products. The supporting questionnaire survey among herdsmen, abattoir managers and patients further points that there is high possibility of transmitting the disease from cattle to humans. By DNA fingerprinting, strains of M. bovis, M. tuberculosis and M. qtýicanum were identified in cattle and humans respectively; thus indicating a typical animal-to-human and human-to-animal transmissions respectively. Combining the two molecular techniques in this study has vastly improved the level of discrimination of the isolates where of the 71 isolates typed, 49 pattems were produced by the two methods combined together, instead of only 23 and 41 types by spoligotyping and VNTR typing respectively. Of the 21 strains of M. mberculosis obtained in this study, only 5 strains have been descnbed previously in the international databases searched, out of which only 2 of them have been descnbed previously in Nigeria. The result in this study has valuable epidemiological and public health significance and calls for prompt and decisive action fron-i the govemment of Nigena towards controlling this deadly discase in both humans and animals.