An 'artificial skin' is being developed which could mean pesticides can be tested without using animals, writes Marina Murphy
A system that uses synthetic cow-hide to measure tick mortality could replace live animals in tests. A non-animal testing system would make testing pesticides simpler and much cheaper, according to Dr Patrick Guerin from the University of Neuchâtel in Switzerland.
Guerin, who is a native of Killarney, has been director of research at the university's institute of zoology since 1987. His main area of interest is disease-carrying insects such as ticks, mosquitoes, tsetse flies, sand flies and triatomine bugs.
The challenge is to develop a system on which ticks can feed and detach when full, while allowing other ticks to continue to feed without any bleeding from the sites of detachment, says Gurein. Any bleeding could drown the remaining ticks, but it is important to be able to remove the ticks sporadically to determine the effect of the treatment on feeding rates.
To this end, Guerin and his team have created an artificial membrane that more closely resembles real skin than any previously developed. "By mixing the appropriate amount of silicon and cellulose rayon fibre, we have managed to create a membrane with the elastic retraction forces of real skin," he says. These elastic forces allow penetration site closure no matter how many times ticks attach and reattach themselves.
The silicone is then decorated with cow hair to make the ticks feel more at home and inserted into an acrylic tube over a 2mm layer of cow's blood. Ticks were readily attracted to this faux-cow, and by coating the artificial skin with pesticide it is possible to observe its effect on tick-feeding rates and mortality.
Traditional testing uses more than 10,000 animals per year, including gerbils, rabbits guinea pigs and cattle. As well as greatly reducing the numbers of animals used, the new test is more sensitive, says Guerin.
In the case of the chemical fipronil, for example, researchers were able to measure effectiveness far earlier than the traditional methods because the system allowed them to observe "leg trembling" - a symptom of the hyperexcitation of the tick's central nervous system caused by the pesticide.
Ticks cost the agricultural industry billions every year, because they carry several serious diseases including Lyme disease and encephalitis. In Ireland, ticks are mainly responsible for spreading the Louping ill virus.
"But in developing countries, tick-borne diseases are so prominent they have effectively removed animals from farming activities, which is why you see pictures of people pulling ploughs and other machinery in those countries," explains Guerin.
The inexpensive nature of the artificial skin means that it could be used in these countries. "Practitioners in these regions could optimise the use of traditionally used materials against ticks. For example, plant extracts could be applied to the membranes to test for effects in inhibiting tick attachment and to optimise the dosing and storage of the natural products," he says.
"This research takes a simple idea and applies it to great effect, resulting in a potentially significant impact on animal use," says Vicky Robinson, chief executive of the National Centre for the Replacement, Refinement and Reduction of Animals in Research.
"Most importantly, it demonstrates that finding ways to reduce the use of animals in research and testing is as much about improving the science as it is about considering the welfare of animals," she says.