Some considerations for the control of Aedes aegypti
Technical note on some considerations for the control of Aedes aegypti, with a focus on diagnosis, prevention and criteria applicable to professional pest management.
In recent years, the World Health Organization has been warning about the urgent need to articulate and manage a comprehensive approach to vector control, aimed at reducing the burden and threat of diseases transmitted by them. This approach must consider changes in the transmission and risk of diseases, linked to unplanned urbanization, the increase in the movement of people and belongings, changes in the environment, as well as biological difficulties such as the development of vector resistance in addition to the evolution of pathogen strains.
A few days ago, on September 24, the health ministers of the Americas agreed to strengthen actions to prevent health damage transmitted by vectors, based on an inclusive approach to access to quality health services considering that in most cases these are vulnerable populations and often far from health services with the capacity to resolve them. In relation to the plan on entomology and vector control, five axes of work have been proposed for the countries: 1. Strengthen multisectoral work at the level of various programs and sectors so that they collaborate in the prevention and control of vectors. 2. Engage and mobilize local governments and communities, including health services. 3. Improve vector surveillance and evaluation of control measures, including monitoring and management of insecticide resistance. 4. Evaluate and integrate proven or novel approaches to vector control and scale them up where possible. 5. Continuously train not only experts but also public health workers in entomology and vector control.
Oriented towards goal 3 of sustainable development, “Ensure healthy lives and promote well-being for all at all ages”, and in particular point 3. 3 in which reference is made to diseases transmitted by vectors, it is necessary, among many other things, to validate new tools, technologies and intervention approaches against vectors. In this context, considering the outbreaks of dengue, Chikungunya and Zica in recent years, the search for alternatives for the control of Aedes aegypti, in particular, is really a priority.
Regarding the entomological surveillance of this vector, the sensitivity and predictability of the indicators that are traditionally used to define transmission risk are discussed. The ability to infer a relationship between one or more of these indices and outbreaks has been questioned. The relevance of using more sensitive indicators such as the pupal index related to human population or area, as well as the use of indicators based on the spatial distribution of larvitraps, is being evaluated.
Likewise, the resistance of populations of Aedes aegypti to insecticides, demonstrated from colorimetric biochemical tests to detect enzymatic groups, molecular biology to detect mutations and exposure to active ingredients with mosquitoes from different locations, have forced us to intensify the search for new products and strategies.
Regarding alternative control methods, interesting possibilities have emerged, some of them already successfully implemented in several countries in the region. Spinosad, a natural product derived from bacteria Saccharopolyspora spinosa, a mixture of spinosyn A and spinosyn D, represents an alternative that is easy to use, as well as proven effective and residual. Studies carried out in several countries such as the USA, Panama, Mexico and Peru, with Clarke's NATULAR DT product (WHOPES 636/TC & 636DT), reveal a lethal effect for more than 60 days.
The action of the product is linked to the depolarization of neurons from the activation of nicotinic receptors, causing generalized hyperactivity in the nervous system, generating involuntary contractions, tremors and neuromuscular fatigue. Other options that are being evaluated include the use of the Wolbachia bacteria, which has gained relevance from studies that show that it prevents the development of the dengue virus. This strategy is based on the programmed release of mosquitoes carrying Wolbachia, which when released in the field mate with local insects, transmitting the bacteria from generation to generation.
An additional method under investigation involves the use of irradiated sterile males, a technique that has been developed by the International Atomic Energy Agency (IAEA) of the United Nations, and that is being replicated in several countries in the region with encouraging results.
It is urgent to promote basic and applied research aimed at generating innovative intervention approaches based on the cooperation of the state sector, academia and private companies. Last but not least, the development of skills and abilities in the personnel who carry out vector control tasks is of vital importance. To achieve this, establishing permanent training programs must be a priority.