A NEW weapon in the war against mosquito-borne diseases has been discovered - and it involves the bloodsuckers' poo.

James Cook University researchers have found that diseases such as Ross River Fever, Japanese encephalitis, West Nile virus, and Murray Valley encephalitis can be detected in the faeces of mosquitoes.

The discovery could help public health officials save money and time trying to detect disease in local mosquito populations, which would otherwise involve labour-intensive screening of the bloodsuckers and other wildlife.

JCU Cairns researcher Dr Dagmar Meyer, from the Australian Institute of Tropical Health and Medicine, said like all animals, mosquitoes excreted their waste.

"If you imagine any living being, it needs food, and that food gets circulated, and does different things in your body - mainly giving you energy," Dr Meyer said. "You also have waste material.

"The same happens in mosquitoes, except it is microscopic, and can range in colours, from having a red, brown or yellow tinge, depending on whether the mosquito has fed on blood."

To attract mosquitoes to specially designed traps laid in Cairns and Darwin, the JCU researchers used honey with blue and red food dyes.

Pinhead-sized mozzie poos inside the traps were put under the microscope.

Ross River Fever, a common disease spread by mosquitoes, was detected in Cairns, with the mozzie borne viruses West Nile and Murray Valley encephalitis identified in Darwin.

"You can detect these diseases early, and especially cheaper," Dr Meyer said. "You don't need new equipment.

"Most public health authorities that are doing mosquito surveillance and sampling, they already have some kind of traps.

"With what we've done, they can very cheaply amend those traps without buying new material or traps."