Detection of the IS2404 insertion sequence and ketoreductase produced by Mycobacterium ulcerans in the aquatic Heteroptera in the health districts of Dabou and Tiassalé in Côte d'Ivoire

Abstract

Buruli ulcer (BU) disease, caused by Mycobacterium ulcerans, is a major public health problem in Côte d'Ivoire. Until now, the mode of BU transmission was unknown, but recent studies implicate aquatic Heteroptera in the chain of transmission. This study was launched in Côte d'Ivoire to search for specific genetic markers for M. ulcerans in these bugs, including the insertion sequence IS2404 and ketoreductase (Kr), both involved in the synthesis of mycolactone, a toxin produced by these mycobacteria. Samples of aquatic Heteroptera were collected monthly with deep nets from ponds near villages in the health districts of Dabou and Tiassalé. After identification and enumeration of the bugs, batches of the same taxon underwent real-time PCR to search for the IS2404 target and Kr. Saliva of 69 specimens of Diplonychus sp randomly selected in the samples was also analyzed by PCR. In all, 283 single-taxon batches were created. Thus, PCR identified 26 batches belonging to the families of Belostomatidae, Naucoridae, Corixidae, Ranatridae, and Nepidae as positive for both targets. The IS2404 insertion sequence and Kr were present in 6 of the 69 samples analyzed in the saliva of Diplonychus sp. These aquatic Heteroptera suspected of infection by M. ulcerans might release it into the environment because of their ability to fly. They might thus be the source of human contamination.