Stroking a dog could infect a child with a parasitic worm that leads to blindness, a Somerset-based veterinary surgeon says.

It had been assumed by vets that direct contact with dog faeces was needed to pass on the Toxocara Canis worm.

But the new research suggests it might be much simpler to pick up the parasite.

Ian Wright, a vet practising in Burnham-on-Sea, and colleague Alan Wolfe found that of 60 dogs they examined, 25% had Toxocara eggs in their fur.

Up to 180 eggs were discovered in a gram of dog hair - a much higher density than found in the soil.

A quarter of the 71 eggs analysed contained developing embryos, and three were mature enough to infect humans.

'Good cuddle'

The millimetre-long eggs are very sticky and could easily be picked up by someone stroking an animal, say the vets.

Mr Wright told New Scientist magazine the findings pointed to Toxocara infection being a dog ownership problem.

"It has probably got very little to do with dogs fouling public places," he said.

His advice to anyone handling dogs was "wash your hands before meals, and after a good cuddle".

Mr Wright, whose findings were reported in the Veterinary Record, said the risk of picking up Toxocara was still low.

Fewer than 20 people were infected each year in Britain, he said.