By John Newell, former Science Editor, BBC World Service
CAN dogs be trained to diagnose cancer? The experience of ordinary people suggests that they can and that the remarkable known power of dogs, sense of smell, could be put to work to diagnose other diseases.
Dognoseis, as this canine diagnosis might be called, first attracted attention in the medical journal The Lancet in 1989. The letters page described the case of a woman whose dog's repeated sniffing at a lesion on one thigh had led her to seek her doctor's advice. The lesion was subsequently diagnosed as a malignant melanoma.
The dog (a bitch which was a cross between a border collie and a dobermann) had shown no interest in other moles on the patient's body but frequently spent several minutes every day sniffing the malignant mole, sometimes through the patient's trousers.
After several months of this the dog tried to bite off the mole while the patient was wearing shorts and this led her to seek medical advice, after which a malignant melanoma was diagnosed.
"The dog may have saved her owner's life by forcing her to seek medical advice while the mole was still at a thin (non-invasive) stage," said Dr Hywel Williams and Dr Andrew Pembroke, of the Dermatology Department at King's College Hospital in London, in their letter to The Lancet.
They went on to say that in their view: "The use of animals with highly developed sensory modalities in cancer diagnosis is worth considering."
Several years later Dr Williams - who had remained interested in the potential of dogs as cancer diagnosticians - and Oxford orthopaedic surgeon John Church, who is studying the potential of a number of living organisms for diagnosing and treating disease, together reported another case of "dognoseis".
This time a man aged 66, with a long-established patch of eczema on one leg that had been treated with creams and anti-fungal agents without success, found his labrador dog persistently pushing its nose against the eczema through his trousers.
This prompted the man to return to his doctor and the patch was removed. Later it was found to have been cancerous and after surgery the dog showed no further interest in the leg.
In a third case a young dalmatian showed a determined interest in a fleck of pigmentation on one leg of a 20- year-old woman, sniffing at it until a doctor was consulted, who referred the patient on, to a skin specialist. The doctor found a malignant melanoma and removed the fleck and tissue around it - since when there has been no recurrence. It is likely that the dog saved the young woman's life.
After seeing one of these reports, Dr Armand Cognetta, a United States dermatologist in Florida, started work with a retired police dog handler, Duane Pickel, to train dogs to locate and retrieve tissue samples of melanoma which had been removed surgically from patients and stored in bottles.
A trained dog named George was used to test a patient who had been declared cancer-free. But the dog's obsessive sniffing at one particular mole finally led to its removal and to it being found to be malignant.
Dogs have shown their value in giving warning of at least one other disease state.
Neuropsychiatrist Dr Steven Brown of Plymouth University, southern England, has shown that dogs can reduce the frequency of epileptic seizures by 40 per cent in those prone to them because the presence of the friendly animal reduces the stress that helps to bring on an attack.
If a seizure is approaching, a trained "seizure alert dog" can then give warning even 40 minutes before a seizure. A young Welsh woman affected by epilepsy and who has been provided with such a dog by the charity Support Dogs, says the dog's insistent warnings never fail to be accurate.
As well as training seizure-alert dogs to respond to and alert individual owners to an imminent epileptic seizure, the charity is carrying out research with Dr Brown to measure the effects of the dogs on the quality of life for people with epilepsy.
In addition the project will investigate whether or not some types of epilepsy respond better than others to the seizure-alert dog solution.
Support Dogs can also train "disability assistance" dogs to undertake a remarkable range of tasks for disabled people, such as opening and closing doors, helping their owner to dress, acting as a steadying support, operating control buttons or light switches, picking up and carrying items, bringing the phone when it rings, and even loading and unloading a washing machine and running shopping errands.
Where medical diagnosis is concerned, John Church believes we have only begun to exploit the power of a dog's nose.
A research group headed by Professor Donald Broom - of the Department of Clinical Veterinary Medicine at the University of Cambridge, with his colleague Dr Barbara Somerville, an expert on the sense of smell in mammals -is applying for funding to set up a project to try to train selected dogs to recognise prostate cancer in urine samples. Church and Dr Williams are also involved. "Prostate cancer is a good target because it so often is missed and it is such a big killer of men today," said surgeon John Church. If a dog could recognise the early signs in a urine sample then the kind of embarrassing screening men dislike and avoid might be largely avoided."
Other diseases, too, are being targeted. "If TB bacteria in saliva samples could be detected by trained dogs then their use might replace that of hard-to-obtain medical equipment and scarce trained staff in and around refugee camps, in situations like those in Afghanistan today," he said.
