The Potential Role of Nocturnal Biting Insects in the Transmission of Mycobacterium Ulcerans in the Akuapem-South District

Abstract

Several hypotheses have been made about the possible mode of transmission of Mycobacterium ulcerans (M. ulcerans) and one of these is the role of insects as possible vectors. Although studies have been conducted extensively on aquatic insects and mosquitoes, limited work has been done on the prevalence of M. ulcerans in other insects. This study investigated the potential role of nocturnal biting insects as vectors of M. ulcerans. Nocturnal insects were sampled from Buruli Ulcer endemic and non-endemic communities in the Akuapem-South district of Ghana and identified. DNA extracts of pools of the insects captured were run against IS2404 target to detect the presence of M. ulcerans. IS2404 target positive samples were then run using other multiplex real time PCR targeting IS2606 & KR sequences as probable confirmation of M. ulcerans DNA. A total of 1330 insects were captured, identified and pooled according to insect family levels. In all nine orders of insects were recorded including arthropods from the class Arachnida. The highest percentage of insects caught belonged to the order Diptera (71.44%) followed by Hymenoptera and Lepidoptera which were 13.79% and 6.33% respectively. The other orders recorded below 5%. Of the 110 pooled samples extracted which consisted of 93 pooled insect samples and 17 controls, 3 tested positive for IS2404 target but not IS2606 & KR targets. Samples which tested positive belonged to insects of the order Diptera and Coleoptera. Two out of the three pools which tested positive belong to families of insects with biting mouthparts. Two out of the three positive samples were from non-endemic communities and one from endemic communities. The study indicated that nocturnal biting insects may play a role in M. ulcerans transmission through direct contact and may be involved in the complex food web for maintenance of M. ulcerans in the ecosystem within the district.