Concern as "aggressive" mosquito found in Australia's Queensland State

News about: Australia

Date: Fri 4 Nov 2009
Source: BrisbaneTimes.com.au [edited]
<http://www.brisbanetimes.com.au/queensland/new-mozzie-find-triggers-brisbane-dengue-threat-20091204-ka7v.html>

An "aggressive" species of dengue [virus]-carrying mosquito has been found in Queensland, with concerns it could bring the disease to southern parts of the state. Larvae of the Asian tiger mosquito, _Aedes albopictus_ were discovered in the tiny Cape York town of New Mapoon this week. Health authorities say it has the ability to carry dengue, a blood-borne virus that can be fatal in some cases. The mosquito can also transmit yellow fever [virus].

Queensland's Chief Health Officer Jeannette Young said more concerning was its ability to survive in cooler climates and the potential for it to establish itself in the state's south-east, including Brisbane. Until now, dengue fever has been confined to only tropical regions in the north. "The Asian tiger mosquito has the potential to transmit dengue [virus], but is not as effective a carrier as the _Aedes aegypti_ mosquito, which is already established in northern and central Queensland," Dr Young said. "However, we do have some concerns about its spread as it survives at cooler temperatures than _Ae. aegypti_, so it could become established further south."

[Earlier] this year, Queensland experienced its worst dengue outbreak in 50 years, with more than 1000 people infected and one woman killed. The spread throughout regional cities including Cairns and Townsville was so rampant, experts held a dengue summit, summoning experts from all over the world.

Queensland Health says none of the larvae found in New Mapoon tested positive for dengue, and population health experts say the likelihood the Asian tiger mosquito had already spread south was slim, as Cape York is still in dry season. [Dengue virus would be expected to be found in adult mosquitoes, rather than larvae. - ProMed Mod. TY]

_Aedes albopictus_ was 1st found in the Torres Strait in 2005, however, this is the 1st time it has been discovered on Australia's mainland [not so; see comment below]. Dr Young said Queensland Health would work with local and federal authorities on a control program to deal with the Asian tiger mosquito and limit its spread. She said potential breeding sites would be removed "and the community warned about mosquito control methods."

Further investigations into how large the population is on Cape York cannot begin until it receives decent rainfall and the mosquito's eggs become detectable. The Asian tiger mosquito prefers fresh water and breeds in similar conditions to the _Ae. aegypti_, in natural containers in the bush, including cut bamboo, banana trees and coconut shells.

"_Ae. albopictus_ mosquitoes are considered to be aggressive invaders and more cold-tolerant than _Ae. aegypti_ mosquitoes, so may therefore spread more easily throughout Australia," according to Queensland Health advice. "_Ae. albopictus_ mosquitoes can carry dengue fever, yellow fever and other arborviruses." [Byline: Christine Kellett]
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[The 1st reports of _Ae. albopictus_ mosquitoes on the mainland were in 1999 in Darwin in northernmost Northern Territory, imported in a shipment of mining equipment from Indonesian West Timor, and Sydney, in New South Wales, way to the south, imported in a shipment of tires from Japan. See image of _Ae. albopictus_ mosquito at:
<http://www.animalpicturesarchive.com/Arch04/1140055440.jpg> - ProMed Mod.JW.]

[Dengue virus is again (November 2009) being transmitted locally in 2 instances in northern Queensland (see ProMED archive number 20091201.4109), so concern about _Ae. albopictus_ becoming an additional dengue virus vector is real. It is curious that the risk of introduction of chikungunya virus (CHIKV) and transmission by _Aedes albopictus_ was not mentioned in this report, given the introduction of this virus into Italy triggering an outbreak with transmission by _Ae. albopictus_ in 2007. CHIKV was introduced by an infected traveler coming from India, where an outbreak was ongoing at the time (see ProMED archive number 20071031.3534, below). Even this year (2009) CHIKV infected travelers coming from Sri Lanka and Singapore arrived in Italy and France, but apparently without ongoing virus transmission. However, there would be an open question about whether the adaptation of CHIKV and _Ae. albopictus_ in Australia would be sufficient to provide efficient transmission.

Professor EA Gould provided an interesting commentary emphasizing the importance of adaptation of CHIKV to _Ae. albopictus_, with the risk of wide geographic spread to areas where this mosquito has become established (see ProMED-mail archive number 20080910.2829). Given the extensive travel between CHIK virus-endemic countries in South and Southeast Asia with Australia, the risk of importation and spread of CHIKV into northern Queensland seems substantially greater than does yellow fever (YF) virus introduction coming from isolated jungle YF cases in South America or Africa.

[An interactive of Queensland showing the locations of Townsville and Cairns (where dengue cases occurred) and New Mapoon (where _Ae. albopictus_ was detected) can be accessed at:
<http://www.maplandia.com/australia/queensland/brisbane/brisbane/>

A HealthMap/ProMED-mail interactive map of Australia showing the state of Queensland can be accessed at:
<http://healthmap.org/promed/en?v=-25.7,134.5,4>.

Cape York sticks up out of the north coast like a sore thumb. Zoom in to Trunding on the cape's west coast to find Mapoon, just north of it. - ProMed Mod.TY/JW]

Source: ProMed Newsgroup Date: 06-Dec-2009 18:04:06