First two people contract TB from cats
Public Health England says the risk of M. bovis passing from cats to humans is "very low".
Two people in England have developed tuberculosis after contact with an infected domestic cat, health officials have confirmed.
Public Health England (PHE) says these are the first known cases of cat-to-human TB transmission.
AHVLA testing confirmed the cat was infected with Mycobacterium bovis (M. bovis) - the bacterium that causes TB in cattle and other species.
Last year, the AHVLA and PHE investigated nine cases of TB in domestic cats in Berkshire and Hampshire.
As a precaution, TB screening was offered to 39 people who had contact with the cats. Of the 24 people to take up the offer, two had latent TB - meaning they had been exposed to TB but did not have the active disease - as well as the two cases of active TB.
Cattle herds in the same area with confirmed cases of TB have been placed under movement restrictions to prevent the spread of disease.
Both people infected with TB are responding to treatment and PHE says the risk of M. bovis passing from cats to humans is "very low".
The bacterium is passed from animals to humans by inhaling or ingesting bacteria shed by the animal, or contamination of open cuts in the skin while handling animals.
Professor Noel Smith, AHVLA's head of bovine TB genotyping group said testing of nearby cattle herds found a small number of infected animals with the same strain of M. bovis as the cats.
"Direct contact of the cats with these cattle was unlikely considering their roaming ranges," he explained. "The most likely source of infection is infected wildlife, but cat-to-cat transmission cannot be ruled out."
No further cases of TB in cats have been reported in Berkshire or Hampshire since March 2013.
Findings from the animal health aspects of the investigation have been published in the Veterinary Record.
According to the report, AHVLA testing shows M. bovis isolated from the infected cats and the human cases of active TB were indistinguishable. This indicates the bacterium was transmitted from an infected cat.
In the cases of latent TB, it was not possible to determine the source of the exposure, or if the TB was caused by M. bovis.
Local animal and human health professionals remain vigilant for further cases of disease in humans, cats and any other pet or livestock species.
Chief veterinary officer Nigel Gibbens has offered advice to veterinary surgeons in a letter published in the Veterinary Record.
For public health reasons, Mr Gibbens recommends euthanasia of cats diagnosed with culture-confirmed M. bovis infection, due to the lack of effective licensed drugs in the UK.
RCVS Knowledge has called on vet practices to audit their post-operative neutering outcomes.
