September 23, 2020

This spring has registered the highest number of tiger mosquitoes in the last five years


The high temperatures and constant rains of the spring of 2020 are the ideal conditions for the reproduction of the tiger mosquito. This situation is evidently reflected in the observations received in Mosquito Alert, a app citizen science, during the first semester of the year.

Spring 2020 has been the fourth hottest in Spain since 1965, according to the State Meteorological Agency based on data from June, and the fifth wettest in the 21st century. In addition to favorable climatic conditions, confinement by COVID-19 may also have contributed to the increase in mosquitoes, which has prevented the care of numerous second homes on the Mediterranean coast.

The number of tiger mosquitoes registered in Mosquito Alert in the first half of 2020 represent an increase of 70% compared to 2018, which was the year with the most insects observed at the beginning of the season. However, the season with the most mosquitoes observed as a whole remains that of 2015.

Accumulated observations of tiger mosquitoes between 2020 and 2015 show that the figures for the current year triple in May and June, above the value of any of the previous years, except for 2018. The development of the 2020 season from now on it is difficult to predict since, according to experience, the spring trend cannot be extrapolated to summer.

Taking into account that the biological cycle of the tiger mosquito is about 15 days, its future density is largely linked to the availability of water throughout the summer, which offers them the opportunity to reproduce.

Climatic variables

The Mosquito Alert research team is currently studying the effect of climatic variables on the reproductive explosion of mosquitoes in spring. Knowing this relationship will allow us to predict what the beginning of the insect season will be like. For this, it will be necessary to consider not only the temperatures and precipitations of spring, but also the environmental conditions of winter. If the winter season is mild, more of the eggs laid in late autumn will survive to hatch in spring.

The ideal in the future is to be able to forecast the start of the mosquito season, just as we are able to do today with the weather. However, the evolution during the summer is difficult to predict, since it is conditioned by specific episodes of summer storms and by human behavior, such as, for example, artificial irrigation.

ORaccumulated reservations

The cumulative observation curves are based on the observations obtained in the app Mosquito Alert but corrected for sampling effort. This data is estimated from the number of people in a specific area and day with active application, as well as by modeling their propensity to make observations that day.

This correction is important in order to estimate the abundance of the insect: it is not the same to record 10 observations in an area where there are five people with the app activated, that 10 observations in an area with 20 people. To carry out this correction, Mosquito Alert needs to know how many people are in a specific area with the active app, a fact that is always obtained by guaranteeing their Privacy.

In order to fit abundance data into models, the digital application collects information about the approximate position of the user’s device at random intervals. Therefore, the data is not of exact position, but is rounded to a 2 × 2 km grid, which is equivalent to knowing that a device is within an area of ​​2 million square meters. The information obtained by the Mosquito Alert server indicates that in a specific grid there was a device at a particular moment.

To guarantee greater privacy for users, the locations of the app are linked to a randomly generated identifier, which prevents any relationship with other data that would allow their personal identification. Despite the importance of these records to be able to calculate the abundances of mosquitoes, users can, at any time, disable this function of the app.

Citizen surveillance

Mosquito Alert is a non-profit cooperative citizen science project, coordinated by the CEAB-CSIC, he CREAF, he ICREA and the Pompeu Fabra University (UPF). Currently receiving the boost from the Obra Social “la Caixa”, European Research Council (ERC), from the European Commission and the Barcelona City Council. Its early years was also co-financed by Dipsalut (Public Health Agency of the Diputación de Girona) and by the Spanish Foundation for Science and Technology (FECYT). Its objective is to fight the spread of invasive mosquitoes and transmitters of infectious diseases that are either re-emerging, or appearing for the first time in Europe.

The main tool that makes it available to people is the Mosquito Alert application, which allows you to send photos of insects and points with standing water where they usually deposit eggs. The application collects the GPS position of the insect in addition to other data, which is processed by a team of experts.

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