A mystery illness is spreading among dogs in some parts of the US, baffling vets who are can’t work out what is causing it. 

Cases of the disease – which can be fatal – started appearing in Oregon, in the Pacific northwest, in August.

The state has now recorded more than 200 cases, according to the Oregon Department of Agriculture (ODA).

Other cases have been reported in the states of Colorado, Illinois and New Hampshire, on the east coast.

The cases seem to share a viral cause but so far testing for common respiratory illnesses has drawn a blank.

Symptoms include coughing, sneezing, nasal and eye discharge, and lethargy.

Dog owners in the US are advised to take their dog to the vet if they develop any symptoms.

The illness often presents as a cough that can last eight weeks or longer, which may not respond to typical treatments.

Dogs may also develop pneumonia, which again may not respond to treatment.

In some cases, pneumonia “rapidly becomes severe”, the ODA said, and “often leads to poor outcomes in as little as 24-36 hours”.

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Most of the dogs who become ill have been mixing with other dogs through boarding kennels or training schools.

ODA advised “caution rather than worry” among dog owners in the US.

It said dog owners can protect their animals by keeping them away from large numbers of unknown dogs, avoiding communal water bowls, making sure vaccinations are up to date and reducing contact with any dogs that appear sick.

Vets and specialists at Oregon State University and the Oregon Veterinary Diagnostic Laboratory (OVDL) are working with the Department of Agriculture’s National Veterinary Services Laboratory (USDA NVSL) to try to work out the cause of the illness.

They are sequencing viral samples from ill dogs.

The ODA is also working with a rescue shelter that had several cases of the illness to collect samples. This will hopefully narrow down the pool of potential causes of the illness, the American Medical Veterinary Association said.

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