July 1st, 2013 by James Ayre
The asian tiger mosquito — Aedes albopictus or Stegomyia albopicta — is a species of large mosquito that is easily recognized by the distinct tiger-like stripes on its body. The species is native to Southeast Asia, but in recent years has invaded nearly ever other tropical region of the world — with the aid of humans of course. The tiger mosquito is a significant pest throughout much of its range thanks to its hardy nature, and is noted for its willingness to feed all throughout the day rather than just at dusk as most mosquito species do, and because it’s an epidemiologically important vector for the transmission of many dangerous viral pathogens — West Nile virus, Yellow fever virus, St. Louis encephalitis, dengue fever, Chikungunya fever, and also several parasitic nematodes, including Dirofilaria immitis.
Given the fact that species transmits so many dangerous pathogens it’s very unfortunate for humans that they are such great survivors, and have been rapidly expanding their range during the last couple of decades — largely thanks to the global shipping and travel industries. Though native to Southeast Asia, they have now successfully colonized much of Europe, the Americas, the Caribbean, Africa, and the Middle East. In warmer regions they re active year-round but in cooler ones they have successfully adapted to ‘hibernating’ over the winter.
“Eggs from strains in the temperate zones are more tolerant to the cold than ones from warmer regions,” suggesting a high selection pressure in the cooler regions for those with cold-weather hardiness, and also likely a great deal of genetic diversity within the species as a whole — leaving open the possibility for further rapid adaption. They are even capable of tolerating snow and temperatures below freezing — interesting when you consider that until recently they were confined to Southeast Asia.
While Aedes albopictus is now considered to be one of the 100 world’s worst invasive species — according to the Global Invasive Species Database — there to appear to be limits to its adaptability. Interestingly, while the species has been introduced to Australia multiple times it has yet to establish itself there — wonder why? Aridity perhaps? Something to do with native species?
With regards to those of us in the US — tiger mosquitos are now present throughout almost all of the southern USA, and along the East Coast as far north as Maine.
Some further information on the Asian Tiger Mosquito via Wikipedia:
The Asian tiger mosquito is about 2 to 10 mm length with a striking white and black pattern. The variation of the body size in adult mosquitoes depends on the density of the larval population and food supply within the breeding water.
The Asian tiger mosquito particularly bites in forests during the day and has been known as the forest day mosquito for this very reason. Depending upon region and biotype, there are differing active peaks, but for the most part they rest during the morning and night hours. They search for their hosts inside and outside of human dwellings, but are particularly active outside.
The Asian tiger mosquito was responsible for the Chikungunya epidemic on the French Island La Réunion in 2005–2006. By September 2006, there were an estimated 266,000 people infected with the virus, and 248 fatalities on the island. The Asian tiger mosquito was also the transmitter of the virus in the first and only outbreak of Chikungunya fever on the European continent. This outbreak occurred in the Italian province of Ravenna in the summer of 2007, and infected over 200 people. Evidently, mutated strains of the Chikungunya virus are being directly transmitted through Aedes albopictus particularly well and in such a way that another dispersal of the disease in regions with the Asian tiger mosquito is feared.
The tiger mosquito is also relevant to veterinary medicine. For example, tiger mosquitoes are transmitters of Dirofilaria immitis, a parasitic round worm that causes heartworm in dogs and cats.
Aedes albopictus also bites other mammals besides humans and they also bite birds. They are always on the search for a host and are both persistent and cautious when it comes to their blood meal and host location. Their blood meal is often broken off short without enough blood ingested for the development of their eggs. This is why Asian tiger mosquitoes bite multiple hosts during their development cycle of the egg, making them particularly efficient at transmitting diseases. The mannerism of biting diverse host species enables the Asian tiger mosquito to be a potential bridge vector for certain pathogens, for example, the West Nile virus that can jump species boundaries.
Pleasant information huh? With rising temperatures the species is likely to continue its spread northwards in the coming decades — exposing more and more people to the diseases that it carries. As has often noted by researchers in the field, one of the most devastating consequences of climate change is likely to be the northwards spread of important vectors such as various species of mosquito, including the Asian tiger mosquito.
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