Australians, water-starved and currently reeling under a severe heat wave, are told tanks set up to collect rainwater could breed more and more mosquitoes.
It is indeed a catch-22 situation. Damned if you, but damned if you don't too. Australians, water-starved and currently reeling under a severe heat wave, are told tanks set up to collect rainwater could breed more and more mosquitoes that carry dengue fever by 2050.
AdvertisementWhen the model included a scenario in which every household in Australia had a water tank that mosquitoes could get into, it predicted that the mosquitoes could complete up to 30 breeding cycles in Darwin in the Northern Territory, and six to eight in Melbourne in the south of Australia.
"It made the difference between the mosquitoes being restricted to a few very wet areas in Queensland to most of populated Australia," says Kearney. The pattern matched the range of the dengue mosquito in the late 19th century before piped water replaced rainwater tanks.
Kearney emphasises that this is a worse-case scenario - the model doesn't take into account all factors that affect mosquito survival. But, he says, "the model shows the potential of dengue mosquitoes to become more widespread if we are not careful about how we store water around the home in response to drought."
Australia is also in the grip of a dengue fever outbreak now, although this is being put down to high temperatures, humidity, and rainfall in the north of Queensland rather than rainwater tanks.
Cairns, has had at least 200 cases since the beginning of November when the "index case", a person travelling from Indonesia, bought the virus in, according to medical entomologist Scott Ritchie of James Cook University in Cairns and the Queensland health department.
"We have some very ill people, with 20% hospitalised. There is the potential for the worse outbreak since the 50s," says Ritchie, who is also a member of the Kearney team.
"We've never seen an outbreak like this. By the time we find out about a case, they've already spread it. The virus has a shorter incubation period in the mosquito than normal, so it's very fast. It's wild."
For the last two or three decades, dengue had been on the rise throughout the tropics, possible due to urbanisation, and increased movement of people.
It may be noticed that as less water is drawn off to flush more-efficient toilets, and showers replace baths, water sits in household pipes for longer. That allows the disinfectant chloramine - sometimes used in water treatment - to break down to form substances that can corrode pipes and potentially release lead, which is particularly dangerous to young children. Bacteria can also multiply in these conditions, forming another potential health risk,, writes Rachel Nowak in New Scientist.
Besides evolutionary changes in response to climate change will allow the mosquitoes to go through up to six more breeding cycles compared to current conditions, vastly increasing the range of the bug.