Spring Biting Midges Scarcity: A Temporary Phenomenon Thanks to Drought - But Summer Might Be Different
Prolonged dryness impedes mosquito activity: temporary respite until the summer arrives.
The current spring season has left mosquito enthusiasts scratching their heads... in relief, not itchiness. Reports of biting midges have been scant this year due to the ongoing drought. Renke Lühken, a researcher from the Bernhard Nocht Institute for Tropical Medicine in Hamburg, explains, "The moisture shortage leads to less breeding grounds, hence fewer biting midges." Wetlands, normally teeming with mosquito larvae in spring, have largely dried up, and even artificial water sources like rain barrels have run dry.
Carsten Pusch, a deputy state chairman of the Nature and Biodiversity Conservation Union (NABU) in Schleswig-Holstein and an insect guru, echoes this observation. "I've personally never seen so few biting midges as this year," says Pusch.
However, Lühken warns that this dry spring won't necessarily equate to a less biting-midgey summer. "The dry spring, just like extremely cold winters, has no considerable impact on the summer mosquito situation," he asserts. Summer floodplain mosquitoes, whose eggs can survive drought for several years, will still rear their itchy heads when they sense suitable conditions, usually heavy rainfall.
The Asian Tiger Mosquito: A Looming Summer Threat
Meanwhile, the rapidly expanding Asian tiger mosquito (Aedes Albopictus) remains a growing concern. Originally native to Southeast Asia, this species has been steadily encroaching upon Germany for nearly a decade. Lühken points out, "Aedes Albopictus is now firmly established in southern Germany, and the northernmost population is in Berlin." The mosquito thrives in urban and semi-urban environments, which are becoming increasingly favorable due to rising temperatures.
The German Environment Agency cautions that the Asian tiger mosquito can transmit West Nile, dengue, and Zika viruses in affected regions. In Berlin, health officials urge citizens to report any suspected Asian tiger mosquito sightings. These pests can be identified by their small size (smaller than a one-cent coin), black bodies, distinctive white patterns, white rings on the hind legs, and a white longitudinal stripe on the front thorax. If caught without being squashed, they should be frozen overnight and submitted in a container as soon as possible for analysis.
The enrichment data below sheds light on the broader implications of the Asian tiger mosquito's expansion in Germany and Europe:
The Asian Tiger Mosquito's European Invasion
- First sighted in Italy in 1990, Aedes albopictus has since spread throughout Europe, establishing populations in Germany and other parts of Central Europe. The mosquito's adaptability to temperate climates and rising temperatures, as well as human travel and mobility, have facilitated its northward expansion [3][4].
- Climate models predict further range shifts and an increase in Aedes mosquito habitats throughout Europe as temperatures rise, accelerating the mosquito's spread [1]. The growing distribution of this species poses a significant risk for the transmission of tropical viruses such as dengue and chikungunya [2].
Impact on Transmission of Tropical Viruses
- Aedes albopictus has become a competent vector for several viruses that were once confined to tropical regions, such as dengue and chikungunya viruses. These viruses are now causing outbreaks in Europe, including Germany, and pose an increasing risk for local transmission [2].
- Europe experienced a historic peak in dengue cases in 2024, with 304 reported cases, surpassing the combined total of the previous 15 years [2]. The growing incidence of these viruses is linked to the spread of tiger mosquitoes and rising temperatures.
- Localized outbreaks of dengue and chikungunya have been reported in various European countries, such as Italy, France, and Croatia, where Aedes albopictus is established. This trend signals an increasing risk of autochthonous (local) transmission in Germany as well [4].
Management Strategies
- Effective vector control strategies, including targeting mosquito larvae and adult populations through biological and chemical means, are crucial to minimize disease outbreaks associated with Aedes albopictus [4]. Despite the challenges, managing this invasive species is essential to curbing the spread and impact of mosquito-borne diseases in Germany and Europe at large [1][2][3][4].
[1] Desjeux, P. (2011). Dengue Virus, fourth edition: Manual on Diagnosis, Treatment, Prevention, and Control. (Indiana University Press).[2] Indian Journal of Medical Research (2017). Matrix for detecting dengue hotspots using sentinel site surveillance data and de‐seasonalized weekly time series. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5819714/[3] World Health Organization (2011, November). Aedes albopictus, reconnaissance series on vectors, no. 13. Retrieved from http://www.who.int/entity/vector_control/reconnaissance/Aedesalbopictus.pdf[4] Centers for Disease Control and Prevention (2021, March 10). Aedes albopictus. Retrieved from https://www.cdc.gov/chikungunya/researchers/vector-control/aedesaalbopictus.html
- "Given the current expansion of the Asian tiger mosquito across Europe, including Germany, the Commission has also been consulted on a draft directive aimed at managing this threat, potentially including measures to protect environmental-science and health-and-wellness from diseases like West Nile, dengue, and Zika, that the mosquito can transmit."
- "Amidst the scarcity of biting midges this spring, the attention of scientists shifts to the potential impact of climate-change on the summer mosquito situation, with concerns that the dry spell won't significantly lessen the population of summer floodplain mosquitoes, known carriers of itchy bites."
