Evidences of the Low Implication of Mosquitoes in the Transmission ofMycobacterium ulcerans, the Causative Agent of Buruli Ulcer

Abstract

Background Buruli ulcer (BU) continues to be a serious public health threat in wet tropical regions and the mode of transmission of its etiological agent, Mycobacterium ulcerans (MU), remains poorly understood. In this study, mosquito species collected in endemic villages in Benin were screened for the presence of MU. In addition, the ability of mosquitoes larvae to pick up MU from their environment and remain colonized through the larval developmental stages to the adult stage was investigated. Methods 7,218 adults and larvae mosquitoes were sampled from endemic and nonendemic villages and screened for MU DNA targets (IS2404, IS2606, and KR-B) using qPCR. Results. MU was not detected in any of the field collected samples. Additional studies of artificially infected larvae of Anopheles kisumu with MU strains revealed that mosquitoes larvae are able to ingest and host MU during L1, L2, L3, and L4 developmental stages. However, we noticed an absence of these bacteria at both pupae and adult stages, certainly revealing the low ability of infected or colonized mosquitoes to vertically transmit MU to their offspring. Conclusion The overall findings highlight the low implication of mosquitoes as biological vectors in the transmission cycle of MU from the risk environments to humans.

Community-based geographical distribution of Mycobacterium ulcerans VNTR-genotypes from the environment and humans in the Nyong valley, Cameroon

“…Before DNA extraction, MU-free fecal materials from domesticated Capra aegagrus hircus (a female goat) were spiked with MU Agy99 pure culture strain and tested for MU-extraction protocol and validation. Contaminations and controls were managed as described previously [17,37].…”

“…Quantitative PCR analysis MU molecular DNA-diagnosis targets (IS2404, IS2606, and KR-B) were screened from genomic DNA-extracts using the TaqMan qPCR protocol described by Fyfe et al [38]. Positivity for MU and the cycle threshold cutoffs were defined using the Cts-method (ΔCts [IS 2606 -IS 2404 ]) as established previously [37,38]. Multilocus VNTR typing and sequence analysis were also performed as additional confirmatory tests for MU.…”

Buruli Ulcer: a Review of the Current Knowledge

“…A few experimental laboratory studies also failed to confirm the implication of mosquitoes as biological agents for the transmission of M. ulcerans [ 38 , 39 •]. In a study by Djouaka et al, ingestion of M. ulcerans was observed during the larvae stage of the mosquitoes but not during both pupae and adult stages, revealing the low ability of infected or colonized mosquitoes to vertically transmit M. ulcerans to their offspring [ 40 ]. Interestingly, a recent study by Wallace et al demonstrated and proposed that a micro-puncture in the skin from any cause, whether from insect bites, injuries, or other natural means, has the potential to inject M. ulcerans from the environment into the skin and generate ulcers [ 39 •].…”

Aquatic Hemiptera in Southwest Cameroon: Biodiversity of Potential Reservoirs of <em>Mycobacterium ulcerans</em> and Multiple <em>Wolbachia</em> Sequence Types Revealed by Metagenomics

“…ulcerans in the aquatic environment primarily infects humans via existing minor skin trauma but could be inoculated mechanically by insect vectors through either infected arthropod saliva or transfer of M. ulcerans on the skin surface into the bite wound. However, except perhaps for sporadic cases [32], evidence for a vector role for biting aquatic bugs (or mosquitoes [103]) in BU transmission in nature is weak [23]. flight.…”