Buruli ulcer in Africa: Geographical distribution, ecology, risk factors, diagnosis, and indigenous plant treatment options - A comprehensive review

Abstract

Buruli ulcer (BU), a neglected tropical disease (NTD), is an infection of the skin and subcutaneous tissue caused by Mycobacterium ulcerans. The disease has been documented in many South American, Asian, and Western Pacific countries and is widespread throughout much of Africa, especially in West and Central Africa. In rural areas with scarce medical care, BU is a devastating disease that can leave patients permanently disabled and socially stigmatized. Mycobacterium ulcerans is thought to produce a mycolactone toxin, which results in necrosis of the afflicted tissue and may be involved in the etiology of BU. Initially, patients may notice a painless nodule or plaque on their skin; as the disease progresses, however, it may spread to other parts of the body, including the muscles and bones. Clinical signs, microbial culture, and histological analysis of afflicted tissue all contribute to a diagnosis of BU. Though antibiotic treatment and surgical removal of infected tissue are necessary for BU management, plant-derived medicine could be an alternative in areas with limited access to conventional medicine. Herein we reviewed the geographical distribution, socioeconomic, risk factors, diagnosis, biology and ecology of the pathogen. Complex environmental, socioeconomic, and genetic factors that influence BU are discussed. Further, our review highlights future research areas needed to develop strategies to manage the disease through the use of indigenous African plants.

Keywords: Herbal medicine; NTDs; Neglected tropical diseases; Putative vectors; Skin and subcutaneous tissue infections; Treatment and management options.

Fig. 1

A schematic diagram showing the methodology followed during the review.

Fig. 2

A map depicting the distribution of Buruli ulcer across Africa. Source: Adapted from [29].

Fig. 3

Spearman correlation scatter plots (linear regression [blue line] with its confidence interval [light gray area]) for the year vs. the number of Buruli ulcer cases in different countries: a) Benin, b) Guinea, c) Cameroon, d) Nigeria, e) Togo, f) Liberia, g) South Sudan, h) Uganda, i) Ivory Coast, j) Ghana, k) Gabon, l) Congo, m) Democratic Republic of Congo, n) Sierra Leon, and o) the overall cases in Africa from 2002 to 2021, as measured by the World Health Organization. Upper left corner with r, Spearman correlation coefficient and p, associated p-value. Data from Ref. [29]. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

Fig. 4

Possibly transmission pathways of Mycobacterium ulcerans in humans. Generally, aquatic habitats harbour insects such as water bugs which are capable of transmitting M. ulcerans to humans and other animals including mice. Host-to-host transmission also occurs between humans and other animal reservoirs. Moreover, transmissions by other insect vectors such as mosquitoes have been reported.

Fig. 5

Flow chart summarizing the various steps involved in the drug discovery from plants.

Fig. 6

A 3D structures of malate synthase (a) and isocitrate lyase (b) a key enzymes of mycobacterium's glyoxylate shunt. Structures were obtained from Protein data bank.