According to the WHO, each year almost 4 billion people are at risk of contracting mosquito-borne diseases, such as dengue fever. Other types of mosquito-borne diseases include malaria, Zika, yellow fever, West Nile virus, and chikungunya.
However, there are some potentially promising ways of containing and reducing the transmission of these diseases, such as by utilizing Wolbachia, a bacterium that can infect many different kinds of invertebrates. In fact, scientists estimate it can be found in 6 out of 10 of all insects.
While they aren’t found in all types of mosquitoes, the bacteria can be introduced in a lab setting into Aedes aegypti, a species that carries dengue, yellow fever, and other mosquito-borne diseases. Scientists then release these mosquitoes into the wild, where they mate and pass it down to future generations.
But why should we care about these tiny microbes?
Because, as this Scientific American article puts it, “For our purposes, the most interesting characteristic of Wolbachia is that it appears to block the dengue virus from replicating in the tissues of mosquitoes.” It has also been shown to limit transmission of other mosquito-borne diseases, such as yellow fever and Zika.
However, in the grand scheme of things, this Wolbachia treatment is still relatively new and further studies are required to analyze some of the intricacies. For example, it’s not so simple as just releasing Wolbachia-infected mosquitoes into the environment and then letting nature take its course. In fact, the environment itself may impact how successful the Wolbachia replacement strategy is successful or not. This is especially noticeable in cities, as “complex urban environments where fine-scale heterogeneity in temperature and built environment may influence mosquito population dynamics.”
In a new Research Article entitled “Climate and landscape features associated with successful Wolbachia replacement in the municipality of Rio de Janeiro, Brazil” in Parasites & Vectors, available now as an Article in Press, Tiley et al. set out to “investigate how climate and landscape features are associated with heterogeneous Wolbachia replacement outcomes using wMel prevalence data from releases in the municipality of Rio de Janeiro, Brazil.”
To do this, the team broke the city down into 500-by-500-meter units and, across a 26-month timespan, analyzed how successful Wolbachia deployment was, exploring various associations, such as the temperature, elevation, rainfall, and building structure.
They found that the success of the Wolbachia introduction was related to warmer temperatures and fewer tall buildings, and negatively associated with high elevation and lower rates of rainfall. However, Tiley et al. did state that, “These associations may also reflect unmeasured socioeconomic or infrastructure variation.”
These results show that Wolbachia replacement strategies may struggle in drier urban environments with taller buildings. They speculate that when trying to introduce Wolbachia infected A. aegypti into these sorts of locations, researchers “may require higher release densities, targeted supplemental interventions, and more intensive monitoring,” though they note that these theories require further studies, pointing to potential directions for future research.
For the time being, strategies involving Wolbachia replacement remain works in progress, but they show great promise. Who knows. Maybe one day, as that Scientific American article puts it, we could defeat dengue.
Header image: Photo of Rio de Janeiro by chulhwan from PixaBay