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Largest study of bovine tuberculosis in sub-Saharan Africa reveals disease diversity in Cameroon

Cameroon is often called ‘Africa in miniature’ due to its geographical and cultural diversity. It now can also claim the highest M. bovis genetic diversity on the continent so far reported.

Cows in Cameroon

Bovine tuberculosis is an infectious disease in cattle and is caused by Mycobacterium bovis, which is endemic in Cameroon. Livestock keepers, abattoir workers and consumers are unknowingly at risk of transmission through contact with infected animals and consumption of infected products.

Given the high costs of existing control tools, most countries in Africa do not have very robust strategies for controlling the disease. Dr Adrian Muwonge and Professor Mark Bronsvoort from The Roslin Institute and colleagues from the UK, Cameroon, Nigeria and Chad conducted the largest molecular epidemiological study of bovine tuberculosis in a sub-Saharan African country to understand the incidence and diversity of the disease throughout Cameroon.

They collected 499 samples from 380 cattle with and without bovine tuberculosis-like lesions at abattoirs in four different cities across Cameroon. Unlike most bacteria, M.bovis evolves slowly by losing genetic material producing a highly clonal population. By exploiting this aspect the scientists were able to use methodology previously developed for human tuberculosis epidemiology to infer how and to what extent the pathogen was transmitted.

Bovine tuberculosis is rather dynamic in Cameroon but region specific i.e. the disease is characterised by limited evidence of transmission but high prevalence of unique genotype in the Adamawa region which is a product of constant additions from the Great Sahel transhumance movement. On the other hand the North West region is characterised by high transmission and a local endemic expansion.

There is an obvious need for a control system in Cameroon (e.g. disease-free zones and restricting animal movement) that can be aligned with the World Health Organization’s “END-TB” strategy aims of eliminating human tuberculosis as a public health challenge by 2035.

Original publication

N. F. Egbe, A. Muwonge, L. Ndip, R. F. Kelly, M. Sander, V. Tanya, V. Ngu Ngwa, I. G. Handel, A. Novak, R. Ngandalo, S. Mazeri, K. L. Morgan, A. Asuquo & B. M. de C. Bronsvoort. Molecular epidemiology of Mycobacterium bovis in Cameroon. Scientific Reports 7, 4652 (2017). doi:10.1038/s41598-017-04230-6