Dog owners are being alerted to a deadly tick-borne disease that has been found in the UK for the first time.
According to reports, one dog has died and several have been taken seriously ill after contracting babesiosis, caused by a parasite carried in the ticks.
There are now fears the disease could spread from the area of Essex where the dogs were walked, despite measures to contain it.
Speaking to the BBC, Clive Swainsbury, a vet at the Forest Veterinary Centre in Harlow, said he had seen some of the four infected dogs.
The parasite leads a host dog's immune system to attack its own blood cells, causing severe anaemia that requires blood transfusion to treat.
Mr Swainsbury warned that the disease will be hard to detect as vets in the UK are not used to it.
At the same time, efforts to contain the spread could be thwarted by wild animals.
He said: "At present we have a very well-defined area.
"The problem in the future is that every female tick will lay a couple of thousand eggs and all those offspring from that disease will also carry the disease.
"As mammals move around they will start spreading the disease. Although you can advise dog walkers not to go there, it's possible that foxes and other animals will transport these ticks."
In a message to dog owners, Harlow Council said the ticks concerned were "extremely rare" in Britain, but urged them to protect their pets with anti-tick treatments and check for the bugs regularly.
The council has also signposted the area thought to contain the ticks.
Harlow councillor Mark Wilkinson, portfolio holder for environment, said the area was popular with dog walkers, however he sought to reassure pet owners that the alert was "purely precautionary" at this point.
He added: "Further tests are going to be carried out on the land once the weather improves and if necessary further advice will be issued.
"The council is also in contact with the Department for Environment Food and Rural Affairs and is seeking any further advice from them."
According to website PetMD.com, owners are advised to do a thorough body check of their dog to find ticks, which are visible to the naked eye but can be drawn to dark, hidden areas of the animal's body such as ears, groin and between the toes.
Signs of ticks include dogs excessively scratching or licking a particular area.
To remove a tick, owners are advised to use tweezers to grip the tick by the head and pull it straight out, and not to twist, burn or apply anything to the skin.
To kill the tick once it has been removed, put it in a small amount of alcohol, rather than squash it.