Researchers find potential biological control for island snake plague
University of Queensland researchers have discovered a group of blood parasites with potential as biological control agents for a snake plague on Guam.
Biological control, they say, would be a far more effective eradication method than the present $2.6 million eradication program on Guam involving workers chopping snakes' heads off with machetes.
Anatomical Sciences Department senior lecturer Dr Joan Whittier and Parasitology Department senior lecturer Dr Peter O'Donoghue compared blood and faecal parasites infecting Brown Tree Snakes in native habitats in Australia, Papua New Guinea and the Solomon Islands with those in introduced Brown Tree Snakes on Guam.
The snake was accidentally introduced to Guam. It stowed away on warships and aeroplanes more than 50 years ago and has now reached plague proportions, spreading to 10 other Central and South Pacific Islands.
Guam had an estimated population of 5000 snakes per square kilometre and as many as 20 could be found stacked up against fences at night, Dr Whittier said. While the snake reached a maximum length of about 1.5 metres in Australia, three-metre-long specimens had been found on Guam, she said.
Even though their bite had only the equivalent toxicity to a wasp sting, it could require hospitalisation for people with allergies or young children, she said.
A territory of the United States, Guam lies in the western Pacific Ocean with an area of 541 square kilometres and serves as a traffic hub for both military and commercial purposes.
Recently the snake, which had decimated native bird populations, frightened tourists, bitten infants in their cribs and even caused black-outs because of its habit of winding itself around power lines on Guam, had been found on Hawaii causing great alarm to authorities there, Dr Whittier said.
In 1996, this led to a US$60,000 Hawaiian Department of Agriculture grant to the researchers to investigate parasites as a potential biological control agent for the snake.
Dr Whittier is recognised as a world expert on the snake and has been comparing native snake populations to those on Guam for the past six years. A colleague and recent visiting scholar at the University of Queensland, Dr Robert Mason, from Oregon State University, has focused his research on the Guam snakes.
She said the grant allowed research assistant Eric vanderduys with the help of Queensland Museum herpetologists to take blood and faecal samples from 6000 snakes and lizards in the Torres Strait, the Northern Territory, Northern Queensland, the Solomon Islands, and Central and South-West Queensland.
These samples were then analysed in the laboratory by University of Queensland researchers with the aim of discovering what pathogens and pests plagued Brown Tree Snakes in their native habitats and whether these were exclusive to the snakes.
Dr O'Donoghue said a parasite affecting more than just Brown Tree Snakes would not be useful as a biological control agent.
The researchers found that while Brown Tree Snakes had a relatively high incidence of parasitic infection in native habitats, they were completely free of parasites on Guam, Dr Whittier said.
"These preliminary results suggest a group of single-celled blood parasites related to malarial protozoas may be the best biological control method for the Guam snakes," Dr Whittier said.
"However, the research is still in its early stages and any potentially suitable parasite will have to be rigorously tested for use as a biological control agent."
For more information, contact Dr Whittier (telephone 07 3365 2536) or Dr O'Donoghue (telephone 07 3365 2584).
