The fight against disease vectors, a priority for Europe
Technical note of edition 8 on the fight against disease vectors, a priority for Europe, with a focus on diagnosis, prevention and criteria applicable to professional pest management.
Vector-transmitted diseases such as dengue or chikungunya were, until a few years ago, tropical arboviruses that few people thought could have a severe impact in Europe. But everything changed with the arrival of Aedes aegypti (currently established in Madeira) and Aedes albopictus (widely distributed in more than twenty countries on the continent). In 2012 we witnessed more than 1,000 cases of indigenous transmission of dengue in Madeira due to the hematophagous action of Aedes aegypti, while the tiger mosquito (Ae. albopictus) has also caused outbreaks of chikungunya and/or dengue in countries such as Italy, Croatia, France and Spain in recent years.
Figure 1. Female Aedes albopictus or tiger mosquito.
This new context has meant that numerous companies in the pest control sector have had to increase their degree of specialization in vector control in order to offer adequate services that minimize the health risks of these diseases for the human population. Entomologists specialized in the biology and control of this type of insects that are so plastic in their behavior, and technicians with a strong base in data analysis and Geographic Information Systems (GIS) to be able to guide surveillance actions and conFigure 2. Process of capturing larvae in natural breeding sites (tree cavities) of the tiger mosquito and taxonomic identification under laboratory conditions. control towards the most critical work areas, are nowadays essential in any company that wants to dedicate itself to large-scale vector control. Focusing on the problem of the vector that is probably most worrying today in Europe, the tiger mosquito, we can say that its arrival and establishment has caused a before and after in the development of vector control programs in the vast majority of the affected cities of the old continent. Basically because until the arrival of these Aedes, there was almost no experience in the management of urban mosquitoes that are so annoying to citizens and capable of adapting to the practice of water microenvironments that can be generated in a city.
Figure 3. Distribution map of the tiger mosquito in Europe (Source: ECDC. Updated as of January 2019). before and after in the development of vector control programs in the vast majority of the affected cities of the old continent. Basically because until the arrival of these Aedes, there was almost no experience in the management of urban mosquitoes that are so annoying to citizens and capable of adapting to practically all of the water microenvironments that can be generated in a city. From the point of view of its control, precisely the main peculiarity of the species is that it is capable of breeding in micro-puddles of water, small water collections of very small dimensions. So that a multitude of small domestic containers
Focusing on the problem of the vector that is probably most worrying currently in Europe, the tiger mosquito, we can say that its arrival and establishment has caused a
Figure 4. Collection of immature specimens of the tiger mosquito in artificial containers in the home and oviposition traps for vector monitoring.
(buckets, drums, animal water troughs, etc.), simple holes in trees or rocks that hold water for a long time, and even waste (cans, bottles, etc.) or structures with insufficient maintenance (clogged gutters, drains that do not drain, etc.), can enable the proliferation of dozens of specimens of the tiger mosquito. Properly managing this problem requires close public-private collaboration, since the population must be trained and informed about this aspect of the biology of the tiger mosquito in order to avoid as much as possible the possibilities of sheltering potential breeding sites for the species in the private sphere. For all these reasons, we usually say that the tiger mosquito is an eminently urban species or, rather, synanthropic, that is, strongly linked to man and the use of the small water resources that we leave available for reproduction. Within the framework of insecticidal applications, it is important to highlight that in Europe there is a scenario delimited by the European Biocides Directive that strictly regulates the typology and method of use of insecticides that can be applied to control mosquitoes. The pest control sector in general in Europe advocates the preferential use of larvicidal products that prevent mosquitoes from reaching the adult stage, biting and causing damage. Within these larvicidal products, we can currently find duly registered biological products (based on bacteria that specifically affect mosquito larvae and not other insects that share their habitat) such as Insecticide Growth Regulators (IGRs). As far as adulticidal products are concerned, only a few pyrethroids and pyrethrins resist as authorized biocides for the control of winged mosquito populations, although their use is subject to very restricted conditions of safety and mitigation of possible environmental risks. This new collaborative scenario between vector control professionals and epidemiological services has also caused pest control companies to have had to take the technology a step further. cation of its qualified personnel. Nowadays, any pest control company that wants to grow hand in hand with the administration in the execution of these vector control tasks of enormous responsibility, must also be required to have basic notions of infectious and clinical-epidemiological behavior among its technical managers. It is time to take a step forward in our sector and position ourselves as what we really are, essential professionals to improve people's Public Health through the design and execution of effective and efficient vector control programs.
Figure 6. Use of entomological aspirators to capture blood-fed female tiger mosquitoes in the vicinity of imported cases of arbovirus (dengue, Zika or chikungunya), for subsequent molecular analysis in order to demonstrate the possible infection of the vector and thus determine the type of intervention to be carried out.