5 out of every 1,000 daily car trips in the Metropolitan Area of Barcelona during the summer carries a tiger mosquito

  • A team of scientists from the citizen science project Mosquito Alert, supported by Obra Social “la Caixa”, together with the Mosquito Control Service of Baix Llobregat and Pompeu Fabra University, has shown that unwitting transport of tiger mosquitos in private vehicles is a clear mechanism for their dispersal.
  • The researchers inspected vehicles at random in checkpoints at tollbooths and vehicle inspection stations, and also gained data from alerts made by citizens using the Mosquito Alert app.
  • Barcelona is the province which exports the most mosquitoes to other Spanish provinces. On the other hand, the province of Madrid currently has the highest risk of invasion by the mosquito due to his high road connectivity with the rest of the country.
Photos of tiger mosquitos inside the cars taken by citizen with the app. Author: Mosquito Alert CC-BY

Photos of tiger mosquitos inside the cars taken by citizen with the app. Author: Mosquito Alert CC-BY


The zone of exploration of an adult tiger mosquito is only a few hundred meters. However, these mosquitos are found in places far away from their breeding sites, where arrival would be impossible were it not for some external aid.  A team of researchers from the Mosquito Alert project, supported by Obra Social “la Caixa”, including experts from the Mosquito Control Service of Baix Llobregat, Pompeu Fabra University, CREAF and CEAB-CSIC, has published a study in Scientific Reports where it is reported that during the summer in the Metropolitan Area of ​​Barcelona, each day between 12,000 and 71,000 cars make trips with a tiger mosquito inside. Based on this evidence, the scientists have evaluated to what extent cars may be advantageous for the tiger mosquito when it comes to colonizing new areas. In addition, for the first time, the study has quantified such passive transport of tiger mosquitoes between provinces Spanish by car through a ranking of the main provinces exporting and receiving the mosquito. With these data, scientists can make predictions about the patterns of colonization based on this method of dispersal.

To date, some layman’s observations and indirect evidence has already indicated that, throughout history, humans have involuntarily helped mosquitoes travel hundreds of kilometers through modes of transportation such as ships or airplanes. “Now we have numbers that show that traveling by car is a mechanism of dispersion in Spain, and knowing this will help us improve the monitoring and control of the species,” explains Roger Eritja, entomologist of the Baix Llobregat Mosquito Control Service and member of Mosquito Alert. The evidence will also improve the prediction of epidemiological risk since “the tiger mosquito is a vector of diseases; the more we understand about the diversity of mechanisms for dispersal and the real extent of their capacity, the lesser will be the risk to public health,” says Frederic Bartumeus, ICREA researcher at CEAB-CSIC and CREAF and director of Mosquito Alert.

Fotos de mosquito tigre dentro de los coches enviadas por los ciudadanos con la app Mosquito Alert. Autor: Mosquito Alert CC-BY

Photos of tiger mosquitos inside the cars taken by citizen with the app. Author: Mosquito Alert CC-BY


However, the researchers note that “we still do not know what proportion of the hitchhiker mosquitoes survive during the trip or at their destinations,” explains Roger Eritja. In this case, the litmus test will fall to genetics.  “Parallel to this study we are doing several DNA analyses to see if the mosquitoes that are in different regions, some very far from each other, are relatives,” says David Roiz from the Montpellier Center of Infectious Diseases and Vectors (MIVEGEC).

The researchers had the help of the Catalan police, vehicle inspection depots, and citizen science

During the summer of 2015, 770 cars chosen at random were inspected in the Barcelona Metropolitan Area. “Using a special vacuum for catching mosquitos we vacuumed the inside of the cars following a specific protocol and giving special attention to the darkest and most difficult areas to access such as below the seats, which is where they tend to hide,” says Isis Sanpera from the Baix Llobregat Mosquito Control Service. One part of the car inspection was done with the collaboration of the Catalan police, the Mossos, in different parts of the Baix Llobregat road network, and the search was incorporated into routine police inspection posts.  The remaining inspections were done at different technical vehicle inspection depots in the Barcelona area.  “In addition to vacuuming the cars we also carried out a survey with the drivers to know their trip’s origin and destination along with other questions,” says Roger Eritja. All of these samplings were coordinated by the Baix Llobregat Mosquito Control Service and were part of a national research project led by the Mosquito Alert team, with funding from the Ministry of Economy and Competitiveness.

Técnicos del Servei de Control de Mosquits de Baix Llobregat inspeccionando vehículos en un peaje con los Mossos. Autor: Consell Comarcal Baix Llobregat

Technicians from Servei de Control de Mosquits de Baix Llobregat doing inspections inside the cars in collaboration with the Catalan police. Author: Consell Comarcal Baix Llobregat


The researchers also used alerts made by citizens using the Mosquito Alert app in order to estimate the quantity of tiger mosquitos in the Spanish provinces. “Together with data on human movement and the estimate of mosquito transport by car we calculated the movement of these mosquitos between provinces. The combination of citizen science at larger scales with scientific experimentation at local scales is quite powerful and in the near future will permit addressing epidemiological problems on a global scale,” says Bartumeus. In an anecdotic sense, the Mosquito Alert data have also shown mosquito transport by car. “We have received photos from the app where the mosquitos are clearly seen in the interior of vehicles. In order to refine the results we surveyed the participants through their mobile phones in order to know if they had seen tiger mosquitos in their cars during their daily trips and how many kilometers they had travelled. In the future, hope to be able to formally incorporate this new format of citizen data on mosquito transport into our models on mosquito movement,” says Bartumeus.

Barcelona is the province which exports the greatest number mosquitoes to other Spanish provinces

The scientists created a mathematical model with these data at its core in order to predict the movement of tiger mosquitos between Spanish provinces and in cars. “Barcelona is the greatest mosquito-exporting province,  followed by Tarragona, Valencia, Alicante, and Murcia. Madrid, on the other hand, is still free of the tiger mosquito, and is the area which is most likely to have new arrivals of these stowaway mosquitos. According to the model, it is most likely that they will arrive from Barcelona, Valencia, or Malaga,” says John Palmer,  Marie Skłodowska-Curie researcher (the EU programme supporting researchers at all stages of their career) in the Department of Politics and Social Sciences at UPF.

Llista de províncies exportadores i importadores de mosquits tigre. Font: Eritja et al. (2017) CC-BY

List of the interprovinces flow of tiger mosquitos between provinces. Source: Eritja et al. (2017) CC-BY


The mathematical model predicts that the months between July and October are those with the greatest amount of mosquito transport between provinces. It is during these months that there are the greatest number of car trips made by vacationers – 6.5 million according to official Spanish sources – and it is also the period of greatest activity of the tiger mosquito.  However, John Palmer says that “this model does not take into account variations in traffic during holidays, where there are often massive movements of cars which don’t occur during the rest of the year. For this reason we want to study transportation patterns and, using the model, be able to extrapolate the predictions to any place, year, and season. Then we will have a better understanding of how this insect is dispersed and be able to propose measures to halt the invasion.”

Paper reference:

Eritja, R., Palmer, J. R., Roiz, D., Sanpera-Calbet, I., & Bartumeus, F. (2017). Direct Evidence of Adult Aedes albopictus Dispersal by CarScientific Reports7(1), 14399.

[Data set]. Zenodo.

Citizen science is a useful and reliable tool for studying the mosquitoes driving global epidemics

  • A study published today in Nature Communications led by researchers at the CREAF, CEAB-CSIC and Pompeu Fabra University shows that citizen cooperation is valuable for studying disease-carrying mosquitos. The study uses the citizen science project Mosquito Alert, supported by Obra Social “la Caixa”, as an example. Researchers from the Universities of Zaragoza and Murcia also collaborated in the study.
  • To study global disease-carrying mosquitos, citizen participation has allowed the researchers to cover much more geographic space in comparison to traditional methods, reducing the economic cost of the two-year study eight-fold.
  • The scientists hope to scale up this citizen science system to a world-wide scale and design new studies on the risk of disease transmission within the contexts of globalization, climate change, and increasing social inequality.
Voluntarios con la app. Mosquito Alert CC-BY

Participants using the app. Mosquito Alert CC-BY


If someone had said to Luis P., a participant of the Mosquito Alert platform supported by Obra Social “la Caixa”, that the picture of the tiger mosquito sent with his mobile phone from Aragon would be a great scientific discovery, he never would have believed it.  The same goes for Jordi S., who found the tiger mosquito in the Catalan pre-Pyrenees for the first time and also raised the alert about its presence using the app. More and more researchers are interested in citizen participation in order to obtain massive data. But is this information of sufficient quality to be used in research? Today, Nature Communications has published a study which highlights how citizen science can revolutionize the monitoring of global disease vectors like the tiger mosquito.

The study, led by researchers at CREAF, CSIC-CEAB and UPF, with the collaboration of researchers at the Universities of Zaragoza and Murcia, shows that when official monitoring and control of disease-transmitting mosquitos is carried out with the aid of the Mosquito Alert collaborative platform, supported by the Obra Social “la Caixa”, the costs and needed efforts are reduced. Using data from 2014 and 2015, the authors calculated that citizen participation with mobile devices reduced the cost of traditional scientific methods by up to eight times. Traditional methods are based on setting traps in strategic areas where female mosquitoes lay eggs.

Map of new tiger mosquito detections in Spain during 2014 and 2015, depending on citizen science source, ovitraps or both. Credits: Palmer et al. (2017) CC-BY

Map of new tiger mosquito detections in Spain during 2014 and 2015, depending on citizen science source, ovitraps or both. Credits: Palmer et al. (2017) CC-BY


Map of new tiger mosquito detections in the Spanish region of Andalucia during 2014 and 2015, depending on citizen science source, ovitraps or both. Credits: Palmer et al. (2017) CC-BY

Map of new tiger mosquito detections in the Spanish region of Andalucia during 2014 and 2015, depending on citizen science source, ovitraps or both. Credits: Palmer et al. (2017) CC-BY


But the real surprise for the scientists was when they confirmed that the citizen alerts made through the app were just as useful as those made by experts for modelling the tiger mosquito’s distribution and predicting its expansion. “The key is to collect information necessary for removing errors and accounting for sampling bias” points out John Palmer, Marie Skłodowska-Curie researcher (the EU programme supporting researchers at all stages of their career) in the Department of Politics and Social Sciences at UPF and first author of the study. The Mosquito Alert platform relies on a team of expert entomologists to validate the citizen scientist reports, which are assigned to categories according to reliability. “Every citizen receives the expert assessment of their photo directly to their mobile phone a few hours after sending it, and this way the citizens learn to recognise tiger mosquito quickly. In a short amount of time we have achieved high quality scientific data, as shown in this study”, explains Frederic Bartumeus, ICREA researcher at CREAF and CEAB-CSIC and director of Mosquito Alert.

The study authors also say that, thanks to citizen science, the tiger mosquito monitoring area within Spain has been expanded. “We now have a large network of volunteers distributed throughout the country who are willing to collaborate with science. This is much better than having to rely on a team of experts who have to travel hundreds of kilometers”, explains Aitana Oltra, scientific coordinator of Mosquito Alert. Beginning in 2014, the project has received more than 3,600 confirmed alerts of tiger mosquitos from throughout Spain, and some of these have been exceptional.ña.gif

Animated daily municipal tiger mosquito report probabilities in Spain using Mosquito Alert app, among April and November of 2014 and 2015. Credits: Palmer et al. (2017) CC-BY


For instance, thanks to the platform’s participants, first sightings were made in Andalucia, the Catalan pre-Pyrenees, Aragon, and Lleida.  What is common to these sightings is that they are in areas far from the coastal zone where the tiger mosquito invasion began.  “The tiger mosquito spreads very fast locally, but also makes long distance jumps; without the help of all of these volunteers raising alerts, it would have taken us much more time to make these key discoveries, especially in remote places where traditional mosquito surveillance tools are not already in place”, says Roger Eritja, entomologist of the Baix Llobregat Mosquito Control Service and head of the team of experts carrying out validation at Mosquito Alert.  All of these early sightings made by citizens have been scientifically validated in collaboration with the Universities of Murcia and Zaragoza, and this will lead to more inspections and the development of country-level public health protocols.

Globalization, climate change and rising social inequalities as risk factors

With new technologies, the scientific world is increasingly connected to people’s daily lives. This connection is vital to address challenges arising from globalization and climate change. “Now we can go even further and calculate the probability that a given person will encounter a mosquito and, as a result, better understand better patterns of disease transmission, and place these patterns in their environmental and social context”, explains John Palmer. In fact, the researchers are already preparing new work to assess the risk of epidemic outbreaks of Zika, Dengue and Chikungunya in Spain using the data provided by citizen scientists using Mosquito Alert. These diseases have an important impact on society and exacerbate problems of poverty and inequality.

Mosquito Alert, increasingly global

Currently, the reports made through Mosquito Alert are an aid to planning pest control measures in areas where the tiger mosquito has been present for many years, such as in the cities of Barcelona and Valencia, as well as in more rural areas such as the province of Girona. Also, thanks to the accumulated experience of studying the tiger mosquito with citizen alerts, the Mosquito Alert team has begun pilot projects in other cities such as Hong Kong (China) and Barranquilla (Colombia). Mosquito Alert also co-leads an international consortium aiming at launching these types of tools to the global scale, with participation of the United Nations Environment Programme, the World Health Organisation, citizen science associations of Europe, America, Australia, Asia and Africa, and prestigious international institutions such as the Wilson Center and Johns Hopkins University in the United States.



John R.B. Palmer, Aitana Oltra, Francisco Collantes, Juan Antonio Delgado, Javier Lucientes, Sarah Delacour, Mikel Bengoa, Roger Eritja and Frederic Bartumeus. (2017). Citizen science provides a reliable and scalable tool to track disease-carrying mosquitoes. Nature Communications8(1), 916.

DOI: 10.1038/s41467-017-00914-9

Coordination between epidemiologists, public health professionals, entomologists and microbiologists: key for minimizing the risk of Zika transmission in Barcelona

  • The Barcelona Public Health Agency (ASPB) has published a sociodemographic, epidemiological, clinical study which also recounts mosquito control efforts carried out following detections of Zika in the city since 2016.
  • To date, no cases of Zika transmission have been documented in Barcelona, but this does not mean that the risk does not exist. With this in mind, the ASPB has made improvements to the response protocol to further reduce any risk of transmission.
Mosquit tigre. Foto: Pixabay CC0 PD

Tiger mosquito. Photo: Pixabay CCO PD


Since the first detection of Zika in Spain in December 2015, the Barcelona Public Health Agency has included vigilance for this virus in its Tiger Mosquito Control and Monitoring Program, and carries out comprehensive studies of each detected case. As explained in the study published in the journal Frontiers in Microbiology, monitoring for the disease and the insect that transmits it are essential for preventing the local transmission of arboviruses – the group of viruses transmitted by arthropods – helping to avoid dire impacts on public health. This is made possible by good coordination among epidemiologists, clinicians, entomologists and microbiologists.

In February 2016, the World Health Organization (WHO) declared Zika as an emerging disease threatening public health worldwide as a result of its rapid expansion and associated illnesses which include Guillain-Barré syndrome and microcephaly in newborn babies. In fact, Spain is one of the European countries with the highest risk of local transmission of Zika; in a city like Barcelona, ​​where the tiger mosquito is established and there are large fluxes of human migration, tourism and global trade, the risk continues to increase.

More travelers from Zika-affected countries

Since 2000, the number of people of Latin American origin residing in Spain has increased considerably. Countries including the Dominican Republic, Venezuela, Nicaragua and Colombia are those most visited by travelers originating in Barcelona, whatever the motives for the visit (to visit family, work, for tourism), and these are precisely the places where the Zika virus is endemic. With this significant movement of humans, it is only more likely that the disease will be imported.

In Spain, all cases of Zika, Chikungunya and Dengue infections are reported to the public health authorities and to the main epidemiology units. In 2016, there were 118 cases of Zika in Barcelona, ​​all of which were due to infections which occurred outside of Spain. Zika cases are classified as probable, confirmed, imported or local depending on the patient’s symptoms in addition to other clinical and socio-demographic data (age, sex, country of origin, etc.).

Esquema dels passos protocolaris que es segueixen quan es detecten casos importats de Zika. Font: ASPB

Scheme of the protocolary steps followed when imported Zika cases are detected. Source: ASPB


The most effective measure to avoid local transmission of Zika is to control the vector

Zika is a virus that is transmitted between infected and healthy people through the bite of the yellow fever mosquito – currently not present in Spain – or the tiger mosquito. The Mediterranean is vulnerable to local transmission since the tiger mosquito is present or established in many areas. It is therefore essential to set up surveillance and prevention protocols to avoid local transmission, using individual and community prevention measures to prevent mosquito breeding and biting. In fact, the published study shows that the periods of year with the most mosquitos – April, August and September – coincide with number of imported Zika cases and therefore a greater risk of local transmission.

In the case of an infection, the city’s epidemiology service instructs the patient on the use of preventive measures to reduce additional infections. The goal is to minimize the risk of Zika transmission through mosquito bites in the area where the infected person lives. At the same time, inspections are carried out to detect if there are mosquitoes or mosquito breeding sites either in the infected person’s home or in the surrounding neighborhood. In most cases, insecticidal treatments are applied in areas with standing water in order to kill any larvae.

Mapa de la ciudad de Barcelona con la localización de los diferentes casos de arboviosis y los resultados de las inspecciones entomológicas. "Risk zonas" (azul): inspecciones mensuales. "Citizen incidencia" (verde): avisos hechos por la ciudadanía que se han hecho durante el estudio de 2016.

Map of the city of Barcelona, with the location of different cases of arbovirosis and entomology inspeccions. “Risk zones” (blue): monthly inspections. “Citizen incidences” (green): reports made by citizen during 2016.


In relation to such preventive measures, new technologies have sweep areas for tiger mosquito presence. Specifically, citizen participation with the Mosquito Alert app has led to the detection of breeding sites close to the homes of infected persons, and this technology has facilitated vector surveillance and control in the city. During 2016, the Barcelona Public Health Agency made entomological inspections at 19 homes of people infected by Zika, 34 public spaces, and carried out 134 follow-up and control tasks associated with cases of imported Zika.

In short, the Barcelona Arbovirus Surveillance Program is an example of how reducing the risk transmission arboviruses such as Zika should be tackled in a multidisciplinary manner. The study was carried out by the principal Spanish public health entities as well the Public Health Agency of Barcelona, ​​CIBER Epidemiology and Public Health, Lokímica Laboratories, Doñana Biological Station, The Microbiology Department of Vall de Hebron Hospital, Hospital Clínico of Barcelona, ​​ISGlobal, and the Mosquito Alert community as part of the Barcelona Zika Working Group.

Renferenced article:

Millet, J. P., Montalvo, T., Bueno, R., Romero-Tamarit, A., Prats-Uribe, A., Fernandez, L., … & Zika Working Group in Barcelona (2017). Imported Zika Virus in a European city: how to prevent local transmission?. Frontiers in Microbiology, 8, 1319.

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