Mycobacterium ulcerans Persistence at a Village Water Source of Buruli Ulcer Patients

Abstract

Buruli ulcer (BU), a neglected tropical disease of the skin and subcutaneous tissue, is caused by Mycobacterium ulcerans and is the third most common mycobacterial disease after tuberculosis and leprosy. While there is a strong association of the occurrence of the disease with stagnant or slow flowing water bodies, the exact mode of transmission of BU is not clear. M. ulcerans has emerged from the environmental fish pathogen M. marinum by acquisition of a virulence plasmid encoding the enzymes required for the production of the cytotoxic macrolide toxin mycolactone, which is a key factor in the pathogenesis of BU. Comparative genomic studies have further shown extensive pseudogene formation and downsizing of the M. ulcerans genome, indicative for an adaptation to a more stable ecological niche. This has raised the question whether this pathogen is still present in water-associated environmental reservoirs. Here we show persistence of M. ulcerans specific DNA sequences over a period of more than two years at a water contact location of BU patients in an endemic village of Cameroon. At defined positions in a shallow water hole used by the villagers for washing and bathing, detritus remained consistently positive for M. ulcerans DNA. The observed mean real-time PCR Ct difference of 1.45 between the insertion sequences IS2606 and IS2404 indicated that lineage 3 M. ulcerans, which cause human disease, persisted in this environment after successful treatment of all local patients. Underwater decaying organic matter may therefore represent a reservoir of M. ulcerans for direct infection of skin lesions or vector-associated transmission.

Mycobacterium ulcerans Disease (Buruli Ulcer): Potential Reservoirs and Vectors

“…An indication for an aquatic niche environment was given in a recent longitudinal study reporting the persistence of M. ulcerans DNA in a village water site located in the BU endemic Mapé basin of Cameroon. Underwater detritus at a localized position of the water hole was repeatedly tested positive for M. ulcerans-specific DNA sequences over a period of more than 2 years after all local BU cases had been treated [45], suggesting that M. ulcerans has adapted to survive in a restricted niche environment. Several studies have indicated that M. ulcerans is unlikely to be free-living and may persist in the environment as a commensal, associated with another protective organism such as amoeboid protozoa or inhabitants of biofilms in stagnant water bodies [46][47][48].…”

“…Furthermore, the anatomical site of the lesions was shown to vary with both age and gender. While children tend to have a more dispersed distribution of lesions over the body, lesions seem to become increasingly confined to the limbs in adults [32,45,54,57], presumably because children cover their trunks less often compared to adults. The gender difference varies between studies and is thought to be influenced by behavioral factors and environmental contact patterns.…”

“…Contrary to the BU situation in Australia, where patients usually seek treatment at early stages of the disease, limited access to health facilities, economic limitations, traditional beliefs, and stigmatization often lead to a drastic treatment delay in Africa, with patients suffering for many months or years from large active ulcerative lesions, shedding the bacteria into the environment. Since recent studies indicated that M. ulcerans may persist for many months in under water decaying organic matter [45], infection may occur at contaminated water contact sites. In other studies, a conceptual model has been proposed, where M. ulcerans, present in the aquatic environment such as in detritus, mud, or plant biofilms, is concentrated by waterfiltering organisms and passed on to predatory aquatic vertebrates and invertebrates feeding on this prey [2,71].…”

Epidemiology and disease burden of Buruli ulcer: a review

“…However, shedding of M. ulcerans from ulcerative lesions of humans with active BU disease may play a role in the dissemination of M. ulcerans in the African BU endemic regions. [14][15][16] Since recent studies indicated that M. ulcerans may persist for many months in underwater decaying organic matter, 112 it may be considered that infection occurs at contaminated water contact sites. Seroepidemiological studies in Ghana and Cameroon have shown that children are much earlier exposed to malaria parasites than to M. ulcerans, indicating that an involvement of insect vectors commonly found close to the households is highly unlikely.…”

Buruli ulcer: wound care and rehabilitation

“…4,5 The disease usually manifests itself as a painless nodule, a firm plaque, or an edematous lesion, which soon ulcerates with characteristic undermined edges.…”