New research has shown that people are in danger of becoming infected from a worm which causes blindness simply by stroking a dog which carries the parasite.
The worm, Toxocara canis, lives in canine intestines and until now it was only thought to be transmissible to humans through contact with canine faeces which contain the parasite's eggs or with faeces-tainted soil.
The risk of toxocara infection is statistically remote but the results can be horrific. The worm can grow in the back of the eyeball, causing lesions which, in the severest cases, can lead to blindness or it can migrate to the liver and lungs, causing a debilitating lethargy called toxocariasis.
Those most at risk are young children who touch the faeces or soil and then suck or lick their fingers. After ingestion, the eggs hatch in the intestine and the larvae are carried to other parts of the body by blood circulation.
British veterinarians have now discovered T. canis eggs in dog hair in addition to canine faeces, according to next Saturday's edition of New Scientist.
Of 60 dogs which they examined, a quarter had worm eggs in their hair, the British weekly says.
Seventy-one eggs were found, a quarter of which had begun to develop embryos. Three of those were found to contain embryos which were mature enough to infect humans.
The vets, Ian Wright and Alan Wolfe, say theirs is the first study to examine the coats of dogs as a source of toxocara infection. "We looked mainly at the anal region and the backs of legs," Mr Wright says in the magazine.
The eggs are just a millimetre (0.04 inches) long and are sticky, which means they could easily be picked up by someone stroking the animal.
Dog-owners should give worming pills to puppies every fortnight for the first three months, then once a month for the following three months, says Mr Wright. After six months, dogs develop some immunity and only need worming every six months and washing every fortnight.
His most important advice is for people to wash their hands with soap and water before meals and after giving the dog a good stroke and for families to be big on hygiene if infants and babies share their home with a dog.
In the US, about 10,000 people a year are infected with toxocara. In Britain, fewer than 20 people a year are infected in a population of 60 million, partly because many of the population have developed immunity to the parasite through exposure. - (AFP)