Updated 2:13 PM ET August 23, 2000 LONDON (Reuters) - Spanish scientists have developed a vaccine to immunize rabbits against two diseases that were developed by man to keep the rabbit population down, the New Scientist reported Wednesday. The vaccine, developed by Juan Torres and colleagues at the Center for Investigation into Animal Health in Madrid, protects rabbits against myxomatosis and rabbit hemorrhagic disease (RHD), both of which were released to control rabbit populations.

The discovery could boost rabbit numbers in countries where their population is dwindling, but it has stirred unease in countries that consider them pests.

"This self-propagating vaccine is not a development that sits easily with rabbit control in Australia," Brian Cooke of Australia's national research organization CSIRO said in the magazine.

"Myxomatosis and RHD, although repugnant from an animal welfare perspective, nevertheless have great benefits for agriculture," he added.

British scientists also were worried about the implications of the new vaccine.

"They are basically creating a new disease. I'd want to be very convinced about its safety and species specificity before it was released," David Cowan of Britain's Central Science Laboratory in York said in the New Scientist.

The vaccine spreads from one rabbit to the next. Torres is conducting a trial involving 300 rabbits on a small island.

"Myxomatosis and RHD are endangering not only the survival of the rabbit, but also their natural predators," Torres said.