Abstract:
Mycobacterium ulcerans disease (Buruli ulcer) is increasing worldwide but there is currently no effective chemotherapeutic treatment. Prevention and control has also not been possible because the mode of transmission remains illusive and at best speculative. Recent investigation however points to the possible involvement of aquatic bugs belonging to the familily Naucoridae in the transmission process. In the laboratory, infected Naucorid species have been shown to transmit the bacterium through their bites. However, to establish that insects of this group are the vectors of Buruli ulcer disease pathogen, it is more important to understand if the insects are naturally infected in their natural environment in the wild. Although considered of much importance for prevention and control, the distribution and ecological determinants of the distribution of these insects are lacking. Naucorid species were collected in three endemic and three non-endemic areas of Buruli ulcer in the Ga District using a D- net and coordinate of collection points were recorded using GPS. Eighteen water bodies were surveyed in this District to study the distribution of Naucorid species. 15 physico chemical parameters of water habitats were analyzed in water samples where Naucorid species were found and where there were not found. A total of 2181 insects were identified as Naucorid species. It was observed that Naucorid species were widespread across all the study areas. Mean distributions were not significantly different between endemic and non-endemic areas of Buruli ulcer. Statistical analysis using binary logistic regression revealed dissolved oxygen, PH and turbidity to be the most significant water parameters that influences the distribution of Naucorid species in a given habitat. The prevalence of infection of the bugs was detected using polymerase chain reaction (PCR) with already published oligonucleotide primers MU1, MU2, PGP3 and PGP4. Out of a total of 1513 of the insects examined by PCR to detect the presence of M. ulcerans, (4.4%) were positive for the bacterium. The infection rates of Naucorid species between water bodies ranged from 2- 7%. This result indicated that there were natural infections in the insects in the wild at all the study areas where the insects were examined. The prevalence of infections of Naucorids between endemic and non- endemic areas was not significantly different P > 0.05. Whereas, the prevalence of infection of the bugs between dry and wet season showed a significant difference P < 0.05. The occurrence of infection in these bugs and their ubiquitous nature suggest that they may play an important role in the transmission of M. ulcerans than presently understood.
