Researchers planning to SIT disease carrying mosquitoes

To combat prevalence of the Aedes Aegypti mosquito in Jamaica, local researchers are looking to sterilise the vector’s male population to help reduce the species’ overall population.

Johann Antoine, research scientist at the International Centre for Environmental and Nuclear Sciences (ICENS), and Dr Sheena Francis, senior lecturer and research fellow at the Natural Products Institute, both spoke to the ongoing research being conducted at the recent staging of the Science for Today public lecture series hosted by The University of the West Indies’ (UWI) Faculty of Science and Technology, titled ‘Killing the Buzz: The Fight against Dengue and other Mosquito-borne Diseases’.

Antoine revealed that the research intends to utilise the sterile insect technique (SIT), which is a biologically based method for the management of key insect pests of agricultural and medical or veterinary importance. It is a component of an area-wide integrated pest management programme.

Francis said the aim of the experiment is to explore how successful sterile male mosquitoes are at competing with the wild male mosquito population to mate with a wild female mosquito population.

It also seeks to answer the question of whether the sterilisation of the male mosquitoes can help to reduce the insect’s population through use of radiation to disrupt the female mosquito’s breeding mechanism.

Meanwhile, Antoine stated that, essentially, the primary objective is to eradicate the mosquitoes as they are a vector for numerous diseases. Some diseases that are transmitted by mosquitoes to humans include the Zika virus, West Nile virus, Chikungunya virus, dengue, yellow fever and malaria.

The male Aedes Aegypti mosquito is essential for breeding and maintaining the species, while the female mosquito is the sole carrier of diseases.

AREA OF FOCUS

Francis said this experiment was in its initial stages and that her area of focus is the rearing of the mosquitoes, the morphology and survival of the mosquitoes, their precopulatory behaviour and their mating success.

“The sterilisation technique has been used on many other insect populations other than mosquitoes. However, it’s been shown to be quite effective at decreasing other insect population but its application in mosquitoes is relatively new,” she said.

As such, Francis noted that there were challenges and so, researchers such as herself were working on addressing some of these challenges to see how best the technology and techniques could be advanced.

Speaking to the dosage distribution of gamma radiation that would be used to induce sterility in the males, Antoine stated that dosage optimisation was important as if it was not the correct amount it could lead to a dominant lethal mutation.

He continued that, if too high of a dosage is received, the males would become uncompetitive, reducing the effectiveness of the programme by requiring a greater number of sterile insects to be released.

Antoine further explained that the principle of SIT includes the need for mass rearing of mosquitoes to take place in special facilities and that this is where the assistance of the Ministry of Health and Wellness comes in.

Then the male and female mosquitoes will be separated, and ionizing radiation will be used to sterilise the male ones.

After this, the sterile males will be released over towns and cities with the assistance of the health ministry again, where the males will be allowed to compete with wild male mosquitoes to mate with the female ones.

The female mosquitoes would then lay eggs that are infertile and bear no offspring, reducing the mosquito population and disease transmission.

Antoine stated that no chemicals or residue will be used that will affect the environment. He continued that the SIT is species specific and would not harm other species in the environment. He further said that the sterile males produced will not be radioactive.

For the successful implementation of this programme, Antoine said the specifies needed to exclusively produce sexually. Mass rearing procedures must be available; the release of sterile insects must present adequate dispersion; sterilisation must not compromise the competitiveness of the male mosquitoes; female mosquitoes must preferable mate only once or irradiated sperm must be very competitive and the population density of the target species must be low, making the release of a dominant population of sterile males over an extended period economically viable.