Abstract
BackgroundThe 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.MethodsA 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.ResultsMycobacteria 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.ConclusionsThis 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.
Highlights
The importance of infections caused by non-tuberculous mycobacteria (NTM) in animals and humans has gained considerable recognition during the past few years
This study found that mycobacteria were present in 39% of cultured lymph nodes from slaughtered pigs in Mubende district of Uganda
Sixty three per cent were from lymph nodes with macroscopic lesions compatible with mycobacteriosis and 31.4% were from those without lesions
Summary
The importance of infections caused by non-tuberculous mycobacteria (NTM) in animals and humans has gained considerable recognition during the past few years. The infections are reported to be caused by a wide spectrum of NTM These infections have been less recognized in sub-Saharan Africa owing to lack of awareness and systematic studies. Unlike members of the Mycobacterium tuberculosis complex (MTC) that are highly pathogenic, the majority of NTM have been regarded as non-pathogenic. This opinion is changing as more NTM have been associated with several human compromised patients and M. terrae isolated from patients with urinary tract infections and chronic tenosynovitis [4]. There are few studies documenting the prevalence of NTM in developing countries especially in sub-Saharan Africa, available reports indicate that the problem could be more comprehensive than previously documented [10,11,12]
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