Rainwater tanks have been identified as a potential cause for the spread of mosquito-borne infectious diseases in Australia.

New research reveals that unsealed rainwater tanks and modifications made to the tanks provide a hospitable environment for the breeding of the Aedes aegypti mosquito, which can expose millions of Australians to dengue fever.

The Aedes aegypti mosquito infects hundreds of millions of people across the globe each year with dengue, Zika, chikungunya and yellow fever. In Australia the mosquito is found mostly in North Queensland but also exists in a number of towns in the Wide Bay region closer to Brisbane.

According to CSIRO scientist Dr Brendan Trewin, previous research had led them to understand that conditions in Brisbane were inhospitable for the species during winter; however, their findings now show that rainwater tanks could provide year-long protection for the Aedes aegypti mosquito in Brisbane and other sub-tropical areas of Australia.

With more than 40 percent of Brisbane properties having rainwater tanks, the risk is real.

“The last time Brisbane had significant Aedes aegypti and dengue epidemics they also had a lot of unsealed rainwater tanks, and our research suggests it was the decision to remove these tanks in the 1950s that was one of the keys to driving the disease-carrying mosquito out of the city,” Trewin said.

Given the risk of an infectious disease outbreak, homeowners must ensure their rainwater tanks are maintained properly. Failure to do so may see the return of the Aedes aegypti and other exotic disease vectors to Southern Australia, with potentially serious implications for Australian public health, he added.

People often make modifications to their rainwater tanks, which exacerbate the risk. These modifications include removing the sieve that collects leaves from the roof and gutters, or adding modified downpipes.

"People need to check to make sure their water tanks are compliant, fully sealed and not capable of allowing mosquitoes in or out of their tanks," says Trewin.

In tests conducted in rainwater tanks and buckets using simulated Brisbane winter conditions, the researchers found that 70 per cent of mosquito larvae survived to adulthood in water tanks, and 50 per cent in buckets.

QIMR Berghofer Medical Research Institute associate professor Greg Devine said that hundreds of people infected with dengue and other infectious diseases arrived in Australia each year, with the diseases further transmitted by the Aedes aegypti.

“These noncompliant tanks pose a real risk of becoming Aedes aegypti habitats and breeding sites, which could lead to outbreaks of dengue, chikungunya and Zika to a population that has no immunity to these diseases,” Devine said.

One of CSIRO’s priorities is to continuously monitor for disease carrying vectors like mosquitoes that could cause an infectious disease epidemic, while at the same time planning for how Australia would respond if one did occur.

“As Australia’s national science agency, CSIRO is working on a range of tools to help safeguard Australia, from real time alert systems, quicker and smarter diagnostic tools, and sterilisation technology that eradicates the mosquito,” Trewin added.

Mosquito proofing rainwater tanks

  • Check for sieves at the entrance and overflow; ensure there are no gaps
  • Check for cracks in plastic tanks
  • Make sure the sieves aren’t rusting and there are no holes
  • Mosquitos feed on broken down leaves so keep gutters leaf free
  • Check that first flush devices are draining