Gut bacteria neutralizes disease-carrying tsetse flies

Yale School of Public Health Research Scientist Brian Weiss, Ph.D., has identified a bacterium that can colonize the gut of tsetse flies and help stop the spread of African trypanosomes, the parasites responsible for causing human sleeping sickness, a potentially fatal disease that threatens millions of people in sub-Saharan Africa every year.

These protozoan parasites can also infect domesticated animal populations, in which they cause a related disease called ’nagana’. Nagana presents an enormous socio-economic burden across the region.

Weiss’s research, published today in the peer-reviewed journal PLOS Pathogens, augments existing insect control practices that rely on releasing sterilized male tsetse flies to reduce the potential disease-carrying fly population. The irradiated male flies outcompete their wild counterparts for female mates, resulting in the production of non-viable offspring.

But one of the concerns with this approach is that male tsetse flies (like females) feed exclusively on vertebrate blood, which is the source of the dangerous sleeping sickness parasites. Releasing irradiated males into a target area, therefore, means also releasing millions of potentially new disease-carrying vectors.

To address this problem, Weiss and colleagues in Professor Serap Aksoy’s lab in the Department of Epidemiology of Microbial Diseases, identified a bacterium, Kosakonia cowanii Zambiae, which they successfully introduced into the gut of male tsetse flies. This bacterium has no impact on the fly’s survival or ability to mate, but it does alter the pH in the fly’s midgut, which is where the disease-carrying parasitic trypanosomes live and grow once the fly ingests them.

The Kosakonia bacteria increases the acidity of the fly’s gut to the point of making it less hospitable for the disease-causing trypanosomes. Taken together with the insect sterilization technique, the use of Kosakonia bacteria could greatly enhance the effectiveness of currently employed tsetse control programs, the researchers said.

The full study can be found at journals.plos.org/pl­ospathogens/article’id=10.1371/journal.ppat.1007470