Argentine scientists test an original preventive strategy to combat dengue

Although in recent years the dengue has been giving public health a “breath”, many experts warned that in the coming summer periods the chances of its return grow up. “In general, outbreaks are recorded every three or five years,” said Pablo Bonvehí, head of Infectious Diseases at the University Hospital. comic. And he recalled that the last two outbreaks were in the summers of 2015-2016 and 2019-2020. In addition, from the north, the infections have been spreading towards the central area of ​​the country with cases in Córdoba, Santa Fe and the AMBA, originating from the very high population density and climate change. Faced with this phenomenon that is here to stay, science is testing various preventative options, from vaccines to reduce infections to original alternatives to reduce the population of mosquitoes responsible for transmitting the virus. In this path is inscribed a original initiative: Stock ponds, pools, fountains, reservoirs and other bodies of stagnant water with fish, where mosquitoes lay their larvae so that they hatch in the warmer times of the year. The idea is that the shoals inserted in these waters feed on the larvae and contribute to effective biological control of mosquitoes.

“It is a project that is already underway and the central idea is to distribute these fish, in the necessary quantities, and free of charge, to any association or entity that requests them and wants to use them to plant them in bodies of water, in order to control the disappearance of mosquito larvae in those places, in a safe and ecological way”, he explained to PROFILE Alejandro Koko Lopez, professor of the chair of Aquaculture from the Faculty of Agronomy of the UBA (Fauba).

Normally in the houses, the preventive task against the dengue concentrates on the messed up so that there is no accumulation of stagnant water. However, there are spaces that cannot be emptied either because they contain a large volume of water or because they are used for viewing. Or even pools. “The initiative that we carry out from the chair aims to use the biological control of the mosquito in waters for productive or recreational use,” explained López, who added: “Dengue is present in Argentina. In 2016, for example, there were 42,000 cases, and in 2020, almost 60,000.”

For now, they explain from Fauba, they began to make deliveries of copies, informally, to some schools and associations that have already requested. But, thanks to a subsidy for the extension of scientific knowledge they received from the national Ministry of Science, “we are climbing the project in order to be able to deliver in greater quantities and also to be able to adequately supervise the implantations of fish that are being carried out, in order to be able to verify animal welfare”.

Control. The idea of ​​biological control is not new and is well documented in the scientific literature. But the Fauba team gave it a couple of twists. After analyzing various alternatives, aquaculture experts they chose two species of local fish to act as “biological controller”: Jenynsia lineata and Cnesterodon decemmaculatusmore commonly called “little mothers”.

“We made this choice because both meet several important requirements for this task: being native they are very well adapted to the local environment, so it is not necessary to use – as was done in the past – exotic species, something that usually causes ecological problems. In addition, he is studying that the two resist a great diversity of environmental conditions and water cycles and therefore the shoals require very little maintenance effort”. And they are also small animals, easy to reproduce in quantity in captivity, which makes it easier to meet an eventual high demand for specimens with preventive fines.

On the other hand, his habitual diet is the microfauna of aquatic ecosystems and this implies that in their new “home” the fish does not require supplementary feeding and the size of the new populations is self-controlled based on the available food. And, while they live, they can keep the number of mosquito larvae in check in small aquatic environments. Finally, the voracity of these animals also contributes to its effectiveness: “an adult ‘madrecita’ can consume up to one hundred larvae per day,” López highlighted.

Finally, the aquaculture expert concluded: “This type of planting is an effective control strategy for larvae in the long term. It helps to reduce the use of chemical products and larvicides and is a relatively simple practice, which can be adapted to all regions of the country where there is stagnant water and risk of diseases transmitted by mosquitoes”, concluded the specialist.

towards the schools

The project provides an extra social side: “We formed an associative nucleus and trained the students from a secondary school specializing in Natural Sciences that is in Villa Soldati. Thus, in the near future, it is these students who will carry out the breeding of specimens, receive the orders and schedule the deliveries of fish to be able to carry out the sowings in a systematic way and supplying schools, clubs, associations, companies, that have this type of reservoirs, fountains or tanks where mosquitoes can leave larvae”, highlighted the Fauba professional.

In addition, the project also contemplates some unprecedented aspects: for example, carrying out controls and subsequent visits to the original stocking of fish to check the effectiveness control task, verifying that there are no larvae in stagnant water. And also reviewing the welfare conditions of these animals, an ethical issue that is becoming increasingly relevant.

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