One of the deadliest species known to man is Aedes aegypti, also known as the Yellow Fever mosquito. This species of mosquito is capable of carrying and spreading diseases such as chikungunya, zika, yellow fever, and dengue fever to more than half of the world’s population. These diseases are the cause for millions of deaths every year and have increased substantially in the last 30 years.(1)
To prevent further spread of these diseases, attempts have been made to control the mosquitoes’ habitats, however, the breeding grounds are often difficult to locate and eradicate.(2) Pesticides are also effective in controlling the mosquito population, but the incorrect use of these chemicals is a concern to public health and the environment.(2)
Alternatively, development of vaccines for these deadly viruses are either still in process, or are heavily regulated by the Food & Drug Administration. In May of 2019, the FDA approved the first vaccine to treat dengue fever. The vaccine, Dengvaxia, is intended for children that are 9-16 years old that have already contracted the disease previously.(5) As the second infection with dengue is often much more severe than the first, the FDA’s approval of this vaccine will help protect people previously infected with dengue virus from subsequent development of dengue disease. However, the vaccine increases the risk of severe infection in children who have never been exposed to dengue.(5)
Aside from the invention of drugs and therapies to treat existing disease, another large organization has taken on efforts to reduce A.aegypti populations in order to prevent disease. Alphabet Inc., a parent company of Google, formed the biological research organization called, Verily. In 2016, Verily attempted to prevent mosquito-borne disease on a global scale with their Debug project.(3)This project uses the Sterile Insect Technique (SIT) to control local populations of A. aegypti in rural and remote locations. This was accomplished by the mass propagation of the male A. aegypti which has been infected with a type of bacteria called, Wolbachia.
This is an idea that’s been around since the 1950s. It’s called the Sterile Insect Technique (SIT), and it has worked on other kinds of bugs, like fruit flies, screwworms, and codling moths. The idea is simple: raise sterile males and release them into wild insect populations. When a wild female mates with a sterile male, her eggs won’t hatch. The population gets smaller with each generation.
Wolbachia spp. are gram-negative bacteria that infect arthropods and cause reproductive sterility.(6) The Debug project focuses on infecting the male A. aegypti with Wolbachia in a controlled setting and then releasing them into the environment. The male A. aegypti was chosen because these species lack the ability to bite and spread disease.The infected male mosquitoes subsequently mate with the female population, and produce infertile eggs.(2) Over time, the mosquito population is expected to decrease, as will the spread ofthese infectious diseases.
Recent studies have shown that at a test site in Fresno,California, a reduction was observed in female A. aegypti,after releasing over 20 million infected males annually, by up to 68% in 2017, 95% in 2018, and 84% in 2019.(4)
Although Verily’s first field study has come to a close, the experience and technological gains have been transferred to programs in other locations where this mosquito species is endemic.(4) With larger scale implementation of this project, mosquito-borne infectious disease may eventually be a concern of the past.
written by Gabriel Garza, Technical Support Specialist at Hardy Diagnostics