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Open Access Research article

Non-tuberculous mycobacteria isolated from slaughter pigs in Mubende district, Uganda

Adrian Muwonge1*, Clovice Kankya12, Tone B Johansen3, Berit Djønne3, Jacques Godfroid4, Demelash Biffa5, Vigdis Edvardsen3 and Eystein Skjerve1

Author Affiliations

1 Centre for Epidemiology and Biostatistics, Norwegian School of Veterinary Science, P.O. Box 8146 Dep, 0033, Oslo, Norway

2 Department of Biosecurity, Ecosystems and Public Health (BEP), College Of Veterinary Medicine, Animal Resources & Biosecurity Makerere University, P.O. Box 7062, Kampala, Uganda

3 Norwegian Veterinary Institute, P.O. Box 750, N-0106, Oslo, Norway

4 Section for Arctic Veterinary Medicine, Norwegian School of Veterinary Science, Stakkevollveien 9010, Tromsø, Norway

5 College of Medicine, University of Arizona, 1656 E. Mabel St, P.O. Box 245221, Tucson, AZ, 85724, USA

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BMC Veterinary Research 2012, 8:52  doi:10.1186/1746-6148-8-52

Published: 7 May 2012

Abstract

Background

The importance of infections caused by non-tuberculous mycobacteria (NTM) in animals and humans has gained considerable recognition during the past few years. In the developed world, where pig production is extensively practiced, 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 recognized in sub-Saharan Africa owing to lack of awareness and systematic studies. In this study we aimed at isolating and identifying species of mycobacteria involved in causing infections in slaughter pigs in Mubende district of Uganda. Furthermore we wanted to identify factors associated with infection prevalence in the study area.

Methods

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.

Results

Mycobacteria were detected in 39 % (143/363) of the examined lymph nodes, 63 % (59/93) of lymph nodes with gross lesions typical of mycobacteriosis and 31% (84/270) of lymph nodes with no visible lesions. Nineteen per cent of the isolated mycobacteria were identified as Mycobacterium (M) avium, of these 78% and 22% were M. avium sub sp. Hominissuis and avium respectively. Other mycobacterial species included M. senuense (16%), M. terrae (7%) and M. asiaticum (6%). 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.

Conclusions

This study demonstrated a high prevalence of NTM infections among slaughter pigs in Mubende district of Uganda. 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% HIV/AIDS prevalence. Therefore, stringent post-mortem inspection at the slaughter houses is of paramount importance to reduce human exposure.