Tuberculosis in cattle and humans in Plateau State, Nigeria

Abstract

Bovine tuberculosis (bTB) is a disease in cattle caused mainly by Mycobacterium bovis. Human tuberculosis (TB) is communicable among people and mainly caused by Mycobacterium tuberculosis. Humans are also susceptible to zoonotic tuberculosis caused by M. bovis. Both pathogens can be transmitted between animals and humans in either direction.
Retrospective records of routine post-mortem examination of cattle slaughtered in Jos Abattoir, Plateau State, Nigeria from 2001 to 2016 were analysed using logistic regression models to determine the prevalence of suspected TB lesions in slaughtered cattle and investigate possible associated risk factors. Similarly, retrospective laboratory records of TB tests on humans at the Jos University Teaching Hospital (JUTH) from 2001 to 2015 were analysed using logistic regression models to determine the prevalence TB in human patients presenting for testing.
Further studies were conducted to determine the current prevalence of suspected TB lesions in slaughtered cattle based on data obtained from detailed post-mortem examination of carcasses at the Jos Abattoir and to isolate and characterise mycobacterial agents from suspected TB lesions in these cattle slaughtered using real-time polymerase chain reaction.
Finally, knowledge attitudes and practices relating to zoonotic TB among livestock workers including abattoir workers and Fulani pastoralists in Plateau State were investigated by means of structured questionnaire surveys.
The retrospective observational study revealed that from 2001-2016, the overall prevalence of TB in slaughtered cattle examined routinely in the Jos abattoir was 4.0%. Multivariable logistic regression analysis of data on TB in these cattle revealed year, month, gender, age group, and location to be statistically significant (all p-values < 10^-9) factors in explaining TB prevalence.
The retrospective data on humans tested for TB at JUTH from 2001 to 2015 revealed an overall prevalence of TB of 14.2% and multivariable logistic regression analysis of revealed year, month, age group, and location to be to be statistically significant (all p-values < 10^-9) factors in explaining TB prevalence.
Detailed post-mortem examination of 500 carcasses of cattle slaughtered at the Jos Abattoir showed the true prevalence of TB in cattle to be almost five times higher (19.6%). Out of these 500 slaughtered cattle, 98 cattle had lesions suspected to be TB. Tissues with lesions were collected for DNA extraction and molecular analysis. Real-time PCR tests revealed 79 of the isolates to be M. tuberculosis. Two lesions contained 4 species (Mycobacterium africanum, Mycobacterium caprae, Mycobacterium pinnipedii, Mycobacterium microti) and seven isolates were unidentified mycobacteria. No M. bovis nor M. bovis BCG were found in any of the isolates.
Analysis of the questionnaire revealed that the majority of respondents were aware of TB, but there were knowledge gaps especially on the zoonotic nature of the disease. Age group, level of education and years of working with livestock were strong determinants of bTB knowledge, while occupation type, age group, and level of education were strong determinants of zoonotic TB preventive practices. The study also revealed risky practices including cohabiting with cattle, not using personal protective equipment, consumption of unpasteurised raw milk or “nunu”, a yogurt-like milk product produced by Fulani pastoralists, and consumption of meat with TB lesions. These are indications of potential risks for zoonotic TB transmission.
In conclusion, the current study confirms that there is high prevalence of TB in humans and cattle in Plateau State and underestimation of the occurrence of TB in cattle. Identification of M. tuberculosis is an unusual and important finding in cattle and potentially of greater concern than the more common finding of M. bovis because it indicates a possibility of both human-to-cattle and cattle-to-cattle transmission of M. tuberculosis in Plateau State. The existence of risky practices could potentially expose individuals to zoonotic TB. These findings suggest collaborative efforts between the veterinary and public health sectors are required to design effective strategies to control the transmission of tuberculosis at the human-animal interface, including routine screening of livestock personnel in close contact with cattle.

Date of Award	9 May 2023
Original language	English
Awarding Institution	University of Bristol
Supervisor	Mark C Eisler (Supervisor), Euan D S Bennet (Supervisor), Katherine Mary Elizabeth Turner (Supervisor) & Ed G M van Klink (Supervisor)