Non–Tuberculous Mycobacteria Isolated from Slaughter Pigs in Uganda

There was a high prevalence of non–tuberculous mycobacteria infections among slaughter pigs in Mubende district in central Uganda. The most prevalent was M. avium, and outdoor systems and valley dam water were factors associated with higher prevalence, according to a team of international researchers based in Kampala and in Norway and the USA. This is an important public health issue, they add, because of the high prevalence of HIV/AIDS in the region.

16 May 2012

4 minute read

By: Jackie Linden

The importance of infections caused by non-tuberculous mycobacteria (NTM) in animals and humans has gained considerable recognition during the past few years, reports Adrian Muwonge of the Norwegian School of Veterinary Science and co-authors there and at Makerere University in Kampala, Uganda, the Norwegian Veterinary Institute and the University of Arizona, US.

In a paper published in BMC Veterinary Research, the authors explain that in the developed world, where pig production is extensively practised, studies on mycobacterial infections and related control strategies have received increasing attention. The infections are reported to be caused by a wide spectrum of NTM. Unfortunately, these infections have been less recognised in sub–Saharan Africa owing to lack of awareness and systematic studies.

In this study the scientists aimed to isolate and identify species of mycobacteria involved in causing infections in slaughter pigs in Mubende district of Uganda. Furthermore, they wanted to identify factors associated with infection prevalence in the study area.

A total of 363 lymph nodes were collected and cultured for the presence of mycobacteria. Isolates were identified by 16S rDNA gene sequencing. A questionnaire survey was administered to identify production related factors associated with infection prevalence. Data were assembled and analysed using descriptive statistics and mixed effects logistic regression analysis.

Mycobacteria were detected in 39 per cent (143/363) of the examined lymph nodes, 63 per cent (59/93) of lymph nodes with gross lesions typical of mycobacteriosis and 31 per cent (84/270) of lymph nodes with no visible lesions. Nineteen per cent of the isolated mycobacteria were identified as Mycobacterium avium, of these 78 per cent and 22 per cent were M. avium sub sp. Hominissuis and avium, respectively. Other mycobacterial species included M. senuense (16 per cent), M. terrae (seven per cent) and M. asiaticum (six per cent).

This study found free–range systems (OR=3.0; P=0.034) and use of water from valley dams (OR=2.0; P=0.049) as factors associated with high prevalence of mycobacteria in slaughter pigs.

This study demonstrated a high prevalence of NTM infections among slaughter pigs in Mubende district of Uganda, concluded Muwonge and co–authors. M. avium was the most prevalent of all NTM isolated and identified. Free–range system of pig management and valley dam water were the most significant factors associated with NTM prevalence in Mubende district.

These findings could be of a major public health concern given that it is in a predominantly pork–consuming population with 18 per cent HIV/AIDS prevalence. Therefore, stringent post-mortem inspection at the slaughter houses is of paramount importance to reduce human exposure, the researchers added.

Reference

Muwonge A., C. Kankya, T.B. Johansen, B. Djønne, J. Godfroid, D. Biffa, V. Edvardsen and E. Skjerve. 2012. Non-tuberculous mycobacteria isolated from slaughter pigs in Mubende district, Uganda. BMC Veterinary Research, 8:52. doi:10.1186/1746-6148-8-52