Mosquito Boom in Spain: Risks, Diseases & Prevention 2024

As warmer temperatures arrive in the Iberian Peninsula alongside one of the wettest winters in recent years, conditions are becoming ideal for a significant increase in mosquito populations. This rise brings with it associated public health risks, particularly concerning the spread of arboviruses – diseases transmitted by mosquitoes. Experts anticipate a notable proliferation of mosquitoes in urban areas, fueled by increased rainfall and milder weather.

Increased Rainfall and Warming Temperatures: A Perfect Breeding Ground

Jordi Figuerola, a Research Professor at the Spanish National Research Council (CSIC)’s Doñana Biological Station, explains that the heavy rainfall is a key factor. “It’s logical that as temperatures begin to rise, mosquito populations will similarly increase,” he states. He notes that a similar pattern was observed last year following a rainy spring, leading to a surge in mosquito numbers during the summer months. MSN reports on this anticipated increase.

Laura Soldevilla, a researcher at the Foundation for the Fight Against Infections, highlights the health implications. “Mosquitoes bring with them the problem of arbovirosis, that is, diseases that they transmit,” she explains. “In recent years, we have been seeing several cases, and we have species in our territory that transmit them.”

Urban Environments and Water Accumulation: Key Concerns

The combination of rainfall and warmer temperatures isn’t just increasing mosquito numbers; it’s also changing where they breed. Figuerola points out that recent storms have created water accumulations in areas where they wouldn’t normally be found. “This is a problem when it happens in urban areas or exceptionally close to them, because we are going to have mosquitoes breeding there,” he says. Standing water, even in small containers, provides ideal breeding grounds for these insects.

However, experts caution against overreaction. Figuerola emphasizes that not all flying insects are mosquitoes. “We have seen images in Doñana of clouds of flying insects: in that case, they are chironomids, which do not bite.” He clarifies that these insects pose no public health risk, and their rapid population increases are distinct from the concerns surrounding disease-carrying mosquitoes.

Identifying Mosquito Species and Associated Risks

If you’re being bitten by mosquitoes during the day, particularly around the ankles and arms, it’s likely the Asian tiger mosquito, Aedes albopictus. This species is easily identifiable by its black color with white stripes and is most active during daylight hours. It’s currently prevalent in the Levante and Andalusia regions of Spain and is expanding into Extremadura and even parts of Galicia.

Other species of concern include Culex pipiens, the common house mosquito, and Culex perexiguus, which transmit the West Nile virus. Culex perexiguus thrives in freshwater environments, so minimizing standing water around homes is crucial. Culex pipiens is present throughout Spain, except for the highest peaks, whereas Culex perexiguus is primarily found in Andalusia and Extremadura.

Aedes caspius, another locally abundant species, can cause significant nuisance bites but doesn’t transmit serious diseases. It breeds in intertidal zones, such as the margins of the Guadalquivir River.

Emerging Threats: Dengue, West Nile, Chikungunya, and Zika

The West Nile virus is currently the only arbovirus circulating endemically in parts of Spain, specifically the southwest peninsula. However, cases of dengue, Zika, and chikungunya have been linked to imported infections. The changing climate is creating conditions that could allow these tropical diseases to become established in Spain.

Soldevilla explains that the West Nile virus often presents with mild or no symptoms, making it difficult to track its true prevalence. Severe cases can lead to encephalitis, a serious infection of the central nervous system. Dengue fever, with its multiple serotypes, poses a risk of severe illness if someone is infected with a different serotype after a previous infection.

While Zika virus cases are currently limited to imported infections, it poses a significant risk to pregnant women due to its potential to cause microcephaly in the fetus. Transmission can also occur sexually.

Currently, chikungunya is the most pressing concern. Outbreaks are occurring in Italy and France, raising the likelihood of its establishment in Spain. This virus causes severe joint pain that can be debilitating for months or even years. A vaccine for chikungunya is available for travelers to endemic areas, and studies are underway to assess its potential use in outbreak settings.

Enhanced Surveillance and Artificial Intelligence

To combat the increasing threat, Spain is leveraging technology to improve mosquito surveillance. The ‘Mosquito Alert’ initiative has implemented a new system based on artificial intelligence (AIMA) to identify invasive species in under five minutes by analyzing images submitted by the public. Mosquito Alert reports that this system has already helped detect the tiger mosquito in 156 Spanish municipalities since 2023, and the Japanese mosquito in 10 northern municipalities.

Citizen participation is crucial, with over 27,000 observations received in the last two years. This data strengthens the capacity to respond to emerging risks like dengue and West Nile virus. A recent study, as reported by InfoSalus, has mapped the distribution of the tiger mosquito, yellow fever mosquito, and Japanese mosquito, revealing their presence in 22% of Spanish municipalities (1,813 out of 8,132).

Preventive Measures and Public Health Recommendations

Both experts emphasize the importance of preventative measures at both the public health and individual levels. Figuerola highlights the need for municipalities in Andalusia to maintain robust vector control programs, tailored to the specific risks in their area. He stresses the importance of adapting these programs based on lessons learned from previous years.

Individual prevention strategies include eliminating standing water around homes, using mosquito repellent, and wearing long sleeves and pants, even lightweight options. The Mosquito Alert app is a valuable resource for identifying mosquito species and reporting sightings.

Soldevilla underscores the importance of public awareness campaigns to educate people about water management and personal protective measures. She also stresses the need for healthcare professionals to consider arboviruses when diagnosing patients with flu-like symptoms, even in the absence of recent travel.

As the climate continues to change, proactive measures and ongoing vigilance are essential to mitigate the risks posed by increasing mosquito populations and the diseases they carry. The focus must be on adapting to the new reality and implementing effective strategies to protect public health.