The changing epidemiology worldwide of Mycobacterium ulcerans

Abstract

Mycobacterium ulcerans is recognised as the third most common mycobacterial infection worldwide. It causes necrotising infections of skin and soft tissue and is classified as a neglected tropical disease by the World Health Organization (WHO). However, despite extensive research, the environmental reservoir of the organism and mode of transmission of the infection to humans remain unknown. This limits the ability to design and implement public health interventions to effectively and consistently prevent the spread and reduce the incidence of this disease. In recent years, the epidemiology of the disease has changed. In most endemic regions of the world, the number of cases reported to the WHO are reducing, with a 64% reduction in cases reported worldwide in the last 9 years. Conversely, in a smaller number of countries including Australia and Nigeria, reported cases are increasing at a rapid rate, new endemic areas continue to appear, and in Australia cases are becoming more severe. The reasons for this changing epidemiology are unknown. We review the epidemiology of M. ulcerans disease worldwide, and document recent changes. We also outline and discuss the current state of knowledge on the ecology of M. ulcerans, possible transmission mechanisms to humans and what may be enabling the spread of M. ulcerans into new endemic areas.

Keywords: Buruli ulcer; Mycobacterium ulcerans; epidemiology; spread; transmission.

Fig. 1.

A severe Mycobacterium ulcerans lesion on the knee of an 11-year-old boy.

Fig. 2.

Map of countries reporting Buruli ulcer cases, stratified by year of first report. Note that each country is represented by its administrative area and that Buruli ulcer did not occur throughout each country. France is represented for its overseas department French Guiana – there has been no case in metropolitan France.

Fig. 3.

Number of Buruli ulcer cases worldwide reported to the WHO from 2002 to 2016.