Monkeys have been genetically engineered to contract Huntington’s disease in a controversial experiment that could aid the development of treatments for the brain disorder.

The rhesus macaque monkeys carry the mutant gene that causes Huntington’s in humans and are the first primate models of the disease.

Huntington’s causes mood swings, depression and memory loss, followed by progressive tremor, neurological damage and death. There is no cure, with five to ten people in every 100,000 who inherit the mutated gene invariably dying from the condition.

The use of genetic engineering to produce monkeys with so serious and distressing a disease has raised strong objections from animal rights groups. Of the five GM monkeys born, three were so severely affected by the mutant genes that they swiftly died.

Maggy Jennings, of the RSPCA, said: “The RSPCA completely condemns these experiments. We understand that medical research is vital, but there are many different ways of carrying out research on these diseases without using primates. The animal suffering involved, in our view, would be considerable.”

Anthony Chan, who led the study team at Yerkes National Primate Research Centre in Atlanta, the United States, said: “We believe it would be unethical not to use our expertise to develop a better model of Huntington’s disease, one in which we can better study the reasons for the disease and its progression.”

The two surviving monkeys with the mutation, he said, would be given the best possible care. His study is published in the journal Nature.

Huntington’s is caused by a dominant mutation in a gene called huntingtin (htt), and people with an affected parent have a 50 per cent change of inheriting both the defect and the disease. Symptoms typically begin between the ages of 30 and 50.

Mouse models of the disease are already available for research, but these do not completely match all the biological and symptomatic features of the disease in humans.

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