The large, brown, flying American cockroach is already found in 90% of the Spanish territory. Its presence, previously exclusive to the Levante coast, is now common in the center of the peninsula and is even displacing the black cockroach. It is expanding, according to the study “Current distribution and history of the colonization of the American cockroach”, recently published and reported by the Spanish Association of Entomology. «The heat lengthens the breeding season and allows more laying. The cockroach is the insect with the greatest presence in the country,” says the text.
In Spain There are three species of cockroaches: the Germanic or kitchen cockroach (Blattella germanica); the American or red one (Periplaneta Americana); and the oriental or black (Blatta orientalis). «Germanic is typical of cuisines and is also called blonde because of its color; The American one is the largest, reddish in tone and capable of flight. It is found mainly in Mediterranean cities, because slightly drier climates are more difficult for it, but little by little it has also conquered the interior, displacing the black cockroach in the sewers. The American variety was recorded in the last quarter of the last century in the Canary Islands because the climate of the islands was very favorable to it, but we can place its most striking period of expansion in the last decade,” explains Manuel García Howlett, general director of the National Association of Environmental Health Companies (Anecpla).
Cockroaches can transmit different types of gastroenteritis, dysentery or salmonellosis by transporting the microorganisms that cause these diseases in their body. However, it is not the only pest that seems to be increasing due to high temperatures. Preventive actions also begin earlier because the reproductive cycles of the “bugs” are advancing. «This year there has been a particularly problematic combination: a start to summer with high humidity and rapidly warm temperatures. There is more activity from mosquitoes, cockroaches, ants and wasps. Furthermore, in recent years we have also observed a worrying trend in the increase of rodents, mice, but especially rats,” says García, who also refers to the resurgence of other pests for reasons that go beyond heat, like globalization. This is the case of bed bugs, whose presence decreased during the pandemic at the same time as traveler movements did.
ticks
Ticks are also one of those common pests during the summer. They transmit Crimean-Congo hemorrhagic fever (in Salamanca a man died a few days ago from this disease). In fact, Lyme disease, which is also transmitted by ticks, is becoming a public health problem. The Carlos III Health Institute published in 2022 a study on the increase in hospital burden due to this disease between 2005 and 2019. The work speaks of a 192% increase in incidence in all autonomous communities except Extremadura.
Also in the last few hours, two cases of West Nile fever, one in Alicante and another in Seville. It is a virus of concern because it is capable of causing encephalitis and is transmitted by mosquitoes. In 2026, human cases rise to 34. “Most people become infected during hot or humid seasons, when mosquitoes reproduce,” says Raúl Rivas González, professor of Microbiology at the University of Salamanca and member of the Spanish Society of Microbiology, in an article published in The Conversation.
Vectors
Mosquitoes are, par excellence, the pest that we associate with summer. And with summers getting hotter and longer, these disease vectors are of growing concern. «As the warm period extends, the reproduction window lengthens. But the increase in temperature not only affects the dynamics of the vector, in this case mosquitoes, but also the dynamics of transmission of viruses such as dengue, Zika or chikungunya. Especially in the case of dengue, increasing the temperature shortens the time the virus needs to replicate inside the mosquito. It is, so to speak, the time the virus needs to reach a concentration high enough for that mosquito to be able to transmit it to another person. At lower temperatures, below 25, this period is usually quite long, approximately five days. When temperatures are above 25 and even 30 degrees, that time is usually shortened to two or three days. This means that the probability increases that this vector, before dying, can transmit the virus,” says Leonardo López, researcher in Climate, Air Pollution, Nature and Urban Health at the Barcelona Institute for Global Health (ISGlobal).
As an expert in climate-sensitive and vector-borne diseases, López recalls that “in cities, what is most commonly found are mosquitoes of the Aedes genus. Of them, Aedes albopictus (tiger mosquito) is the most frequent and widespread vector worldwide. Transmit dengue, zika and chikungunya. In other parts of Europe it is beginning to be very present Aedes aegypti, I wouldn’t say it is more dangerous, but it is more effective in transmitting viruses because it feeds exclusively on humans. In addition, it is a vector that is moving increasingly northward.
Summer pest map
If a map of the pests associated with summer had to be drawn, Anecpla would do it in the following way. The Mediterranean arc and part of the Andalusian coast would be the areas most prone to pests due to that combination of high population density and good climatic conditions. «The islands are also areas prone to pests due to their mild temperatures in winter. In all of them there is more activity of cockroaches, mosquitoes and rodents. Large inland cities, although they have drier heat, also generate, due to the agglomeration of people, refuges with higher humidity where insects and other pests can develop well. Lastly there would be the Cantabrian coast, where, since the warm temperatures of the Mediterranean are not recorded, rodents have more weight than insectsmore typical of Mediterranean areas. “The advantage lies in places with colder winters or located at altitude,” says Manuel García.
Resistors
In general, say those surveyed, in Spain we must be especially attentive to such common species as the Culex pipiens (common mosquito), because it is transmitting West Nile fever.
We must also be attentive to resistance, another of the challenges that have been experienced in recent years. Rodents or cockroaches. «They are generating some worrying resistance. And it is not only those that have to do with the functioning of an active substance but also adaptive resistances that appear, that is, these pests generate an aversion to certain attractive compounds present in the products we use, which is why they avoid them. Resistance is a factor to take into account, but it is difficult for us to know how much weight it has. In reality, we lack information and data, scientifically based studies to fully understand where we are. Everything we handle now, especially in the association, which is still the National Association of Environmental Health Companies, comes to us through associates and their activity indicators: the workloads, the notices they respond to,” explains Manuel García.