The London Underground during World War II was considered one of the safest means of protecting people in a high-density area of the capital. An estimated 170,000 people sheltered in the tunnels and stations during the War. My Aunt was one of those, and happily regaled me with her childhood memories of her nights sleeping in the Holborn to Aldwych London Underground (a short section of the line was closed to trains).
Yet her most vivid memories were not of the noise of the Blitz bombing or the tube canteens that supplied her & my grandparents with endless cups of tea – but the incessant high pitched whine (and itchy bites) of mosquitoes!
Yes, the London Underground mosquito (Culex pipiens f. molestus) has a voracious bite and has adapted to living in this network of warm, dark tunnels under the city. Unlike Culex pipiens – above ground mosquitoes (that you’ll find breeding in standing water in water butts, watering cans & ponds) subterranean mosquitoes breed all year round, but cannot tolerate the cold, so do not usually spread above ground.
The millions of commuters, Londoners and visitors using the tube daily leave behind nutrient rich organic material such as skin cells and sandwich crumbs. These gather in small pools of stagnant water where Underground mosquitoes lay their eggs. The larvae then grow big and strong in the nutrient rich pools, to emerge as adults ready to feed on whatever is available in the tube tunnels – rats, mice and humans.
In the UK these Underground mosquitoes can be a serious nuisance, but are not know to transmit disease. However similar subterranean colonies further south in the Mediterranean, North Africa and Middle East are vectors for disease.
In the past decade Malaria carrying mosquitoes have spread to Greece and West Nile Virus carrying mosquitoes have reached areas of Eastern Europe. Warmer UK temperatures in the future could provide ideal conditions for the Asian tiger mosquito (Aedes albopictus), which spreads the viruses that cause dengue and chikungunya.
Mosquito borne diseases are no longer the distant plight of faraway countries. In our ever more globalised world, international travel and trade have unknowingly given mosquitoes the opportunity to extend their reach and unwary travelers the misfortune to suffer infected mosquito bites.
On 25th April World Malaria Day will bring back into focus the fact that disease carrying mosquitoes make every day a potential malaria day for half the worlds population.