Spring is usually the most anticipated season of the year. But the flip side comes with the reappearance of mosquitoes, including Aedes aegypti , which is a vector of diseases such as dengue, Zika, chikungunya and yellow fever.
To try to control its reproduction, the Faculty of Agronomy of the University of Buenos Aires (UBA) began using, based on innovative research, native fish in water reservoirs to feed on the larvae of the Aedes aegypti .
This solution is more natural, since it avoids the use of insecticides, which are not always 100% effective. And the fact that the fish, Cnesterodon Decemmaculatus (popularly known as water mothers), are native is not a minor fact either, as they collaborate in the preservation of the ecosystem.
“This is a university extension project, in which the Faculty transmits this knowledge about how to breed, sow and manage fish for biological control to other institutions. In this case we do it with an educational center, which is where the first demand came from, since they have orchards with irrigation tanks and other water reservoirs,” says Alejandro Koko López, professor of the Aquaculture department at FAUBA.
But demand can also come from social actors, not only public, but also from the private sector and individuals, such as, for example, owners of Australian fountains or tanks, even a disused recreational pool. “These fish can be placed there from spring, when the mosquito eggs begin to hatch, until December, which is when the pool usually begins to be used,” explains the teacher.
Regarding the effectiveness of water mothers in destroying the larvae, López is conclusive. “We are certain that, in the water reservoir in which we place these fish, no larvae survive. “That is confirmed.”
“In addition, there is no need to give them supplementary food, they eat what is there and their population expands only if they have greater food resources,” he adds.
That is to say, the water mothers, whose maximum size is between 2.5 and 3 cm, ensure, with their presence, the total absence of larvae since, unless the place runs out of water, the fish will reproduce. permanently.
It is worth clarifying that the delivery of fish for mosquito control is completely free, since the program is financed by the Ministry of Science, Technology and Innovation. To request them you can write to controlbiologic@agro.uba.ar.
“From there, the particular case is studied, a diagnosis is made and what type of planting is ideal is analyzed. It is on demand,” says the teacher.
Dengue, a latent epidemic
The problem of diseases transmitted by the Aedes aegypti mosquito is not minor. According to the Ministry of Health of the Nation, in the case of dengue alone, there went from about 40,000 cases in 2016 to almost 60,000 in 2020, taking into account the particularity of said year, with the appearance on the scene of Covid-19 and the subsequent quarantines, so the scenario could have been even worse.
And, only in the AMBA area, it is estimated that one in four adults would have been infected by the virus throughout their life, which is potentially dangerous, since "if a person who had dengue becomes infected again with "Another of the four strains of said disease, not with the same one, has greater risks of having more complicated effects than usual," says Sylvia Fischer, researcher member of the Mosquito Study Group (GEM) of the Faculty of Exact and Natural Sciences. from the UBA.
Part of the growth in these cases could be explained by the mosquito’s greater resistance to low temperatures. According to a study by the (GEM) the Aedes aegypti acquired a great adaptive capacity, which would explain the greater territorial expansion of this insect in Argentina, especially towards cooler and colder areas.
According to Fischer, this mosquito adaptation was mainly due to “diapause, something like an inhibition of the eggs from hatching during the winter months.” They can resume their reproduction and development with the arrival of the first days of heat and, when they do, they have a greater amount of lipids, which are the fats necessary as an energy reservoir.
Other adaptations that the Aedes aegypti made , compared to different species of mosquitoes, is that “it completes its development at lower temperatures than the others, being able to do so up to 12°C”, about 3 or 4 degrees less than others, describes the researcher. And, she adds that “the colder its origin, the greater its development.”
