Vets say they have seen an increase in foxes infecting pet dogs with a potentially lethal illness.

They believe the infected foxes are visiting gardens in search of food and leaving parasitic mange mites behind for pets to pick up.

Market Harborough in particular, in the heart of what was fox hunting country, has seen a large rise in the number of cases in the past 18 months.

Vet Tim Murphy, of Town and Country Veterinary Centre, in the town, said: "There has been a marked increase. In the past, we might get one or two cases every six months.

"Now, we are getting two a week.

"I have no doubt it is linked to the increase in the suburban fox population.

"I would urge people not to encourage foxes by feeding them.

Mr Murphy said: "There has been an increase in sightings of mangy foxes which look very ill."

He urged dog owners to be on the lookout for mange on their animals and take action if they see them scratching violently.

The mange mite eats the skin of the dog or fox causing the animal to suffer an allergic reaction, which increases if untreated.

If the animal is not given medication it can die because its system will become so run down.

The mite, which is difficult to detect, is restricted to the dog family, although it can cause skin irritation for owners.

Veterinary surgeon and skin specialist David Bentley, based in Leicester Forest East, has had cases of mange referred to him from around Leicester and the county.

He said: "There has been a definite increase in mange in dogs over the past 15 years, coinciding with the increase in the urban fox population.

"Cases in pet dogs are now regular, much more so than a few years ago.

He said: "If an infected fox gets into a garden and sleeps under a shed and a family pet dog does the same, then the dog will get infected."

Market Harborough resident Red Williams owns two border collies, Rio and Izzy, who contracted mange a few weeks ago.

Mr Williams, 52, said: "I have never seen any foxes in our garden but I take the dogs into the nearby fields."

He said 14-year-old Rio was the first to show discomfort, followed by 18-month Izzy.

"Rio had a bit of mange on one of her legs which was sore and which she scratched all the time. It's an evil condition which spreads quickly."

Both dogs have started to recover after being given steroids and ointment to combat the inflammation.