**1. Introduction**

*Mycobacterium ulcerans* is the causative agent of the subcutaneous necrotic condition known as Buruli ulcer (**Figure 1**) [2, 3]. The bacillus is the third most common mycobacteria disease causing agent after *Mycobacterium tuberculosis* and *Mycobacterium leprae* [4].

*M. ulcerans* produces the toxin-Mycolactone (**Figure 2**), which plays a key role in the pathophysiological features of the disease [6–8]. Buruli ulcer has been reported in 34 countries (**Figure 3**), mainly in the tropics and subtropics [10]. Tropical countries include Benin [11], Cameroon [12–14], Ghana [15], Democratic Republic of Congo [16] and Nigeria [17, 18]. BU is also prevalent in Queensland [19], a subtropical region, and in Victoria, a temperate area, all within Australia [20].

The exact mode of the transmission remains unclear [10, 21]. However, *M. ulcerans* is believed to have an aquatic niche [22–26]. Aquatic insects, belonging to the Family: Belostomatidae and Naucoridae have been implicated as possible vectors in Africa [22, 27, 28]. In Australia, mosquitoes [20] and possum [29] have been suggested as vector and reservoir [20, 29] respectively. Initial diagnosis of BU is based on the

**Figure 1.** *A severe Buruli ulcer on the upper limb. Image was taken from WHO website [1].*

experience of the clinician [30], but PCR targeting the *M. ulcerans* DNA, IS*2404* [31], isolation and culture of the bacillus and histopathology are used for confirmation [32–34].

### **Figure 3.**

*Distribution of Buruli ulcer, worldwide, 2020 [9].*

In Africa, the disease is common in the rural setting where access to medical facilities and other infrastructure is limited [35, 36]. The opposite is true in Australia [10]. More cases have been reported among people living near wetlands [21, 37]. Gender is not a risk factor [10, 38], however age has been identified as a non-environmental risk factor [10, 38]. BU is prevalence among children between 5 and 15 age group in Africa [38]. Whereas in Australia the >60 age group are most susceptible [39–41]. This has been attributed to the ageing population in Australia, as well as immunosenescence [41–43].
