Amazonian Fungi Demonstrate Success in Combatting Disease-Spreading Mosquitos

The Aedes aegypti mosquito (A. aegypti), known for transmitting diseases like dengue, chikungunya, Zika virus, and yellow fever, has been progressively adapting and spreading illnesses in many tropical and subtropical regions worldwide. The rising number of these diseases has urged scientists to investigate new methods of controlling these mosquitos.

A recent study from the Federal University of Acre (UFAC) has identified multiple fungal strains from the Brazillian Amazon rainforest that demonstrate promising efficacy in managing the populations of A. aegypti larvae. This discovery opens up the possibility of utilizing organic and environmentally friendly larvicides as a sustainable alternative to chemical pesticides.

Controlling a global health threat

The A. aegypti mosquito is originally from Africa but has spread to the tropical regions of over 120 countries. They have evolved to thrive in urban environments because of abundant sites of still water where they can lay their eggs. The multiple viral diseases that the species carries are a major public health concern, affecting millions of people worldwide.

Because there aren’t many available vaccines and treatments for these viruses, the primary means of reducing transmission is through the elimination of their breeding sites and the use of chemical insecticides. However, many mosquito populations have developed a resistance to insecticides, and the frequent use of these chemicals can have detrimental effects on the environment and non-target species. 

Mosquito-borne diseases, especially dengue, are a growing threat to public health in Brazil. In 2019, Brazil reported 2.2 million cases of dengue, making up around 70% of the total recorded cases in the Americas. As the number of diseases and cases continues to rise, there is an urgent need for more effective methods of mosquito control. The UFAC study may offer a promising solution to this conflict.

Study background

Because the Amazon rainforest contains around 25% of the planet’s terrestrial biodiversity, the researchers of the study wanted to look into the potentially useful microorganisms from there as a means to control A. aegypti populations (1). They specifically targeted fungi because of their known biological properties and history of potential as a natural pesticide.

To do so, they isolated thirty-six different fungi from various water sources to explore a wide range of the Amazon’s microbial wealth. They prepared extracts from both fungal mycelium and culture medium. The extracts were tested under controlled conditions for their larvicidal capabilities against A. aegypti. The larvae were exposed to eight different concentrations of the fungal extracts to determine the appropriate lethal concentration. 

Major findings

The results of the study found little success with the mycelium extracts. However, fifteen culture medium extracts showed larvicidal activity at a 50% mortality rate, with six of these killing 100% of the larvae within only 72 hours of exposure and three that were lethal in less than 24 hours. These promising results suggest that some of the fungal strains are able to kill A. aegypti larvae due to metabolites that they secrete (2).

The findings of this study contribute to a larger effort to control mosquito-borne diseases through naturally derived products. Although more research is required to solidify this method as a means of treatment, the findings showcase the immense potential of Amazonian fungi as a biological control agent.

The approach would have several advantages over traditional chemical larvicides, as the fungal extracts are safer on the environment and reduce the risk of impacting non-target organisms. The next steps would involve optimizing the extraction process and conducting field trials to further analyze the practicality of these fungal extracts for mosquito control on a larger scale. 

References

1. Malhi, Y., J. T. Roberts, R. A. Betts, T. J. Killeen, W. Li, and C. A. Nobre. 2008. “Climate Change, Deforestation, and the Fate of the Amazon.” Science 319 (5860): 169–72. https://doi.org/10.1126/science.1146961.
2. Oliveira, Marta Rodrigues de, Ricardo de Melo Katak, Gilvan Ferreira da Silva, Osvaldo Marinotti, Olle Terenius, Wanderli Pedro Tadei, Afonso Duarte Leão de Souza, and Antonia Queiroz Lima de Souza. 2021. “Extracts of Amazonian Fungi with Larvicidal Activities against Aedes Aegypti.” Frontiers in Microbiology 12 (December). https://doi.org/10.3389/fmicb.2021.743246.