Two people in England have developed tuberculosis (TB) after contact with pet cats in the first ever recorded cases of cat-to-human transmission, officials have said.
The two human cases are linked to nine cases of the Mycobacterium bovis infection in cats in Berkshire and Hampshire last year, according to Public Health England (PHE).
Both people were responding to treatment.
Veterinarians believe domestic cats could be catching the disease by venturing into badger setts or from rodents that have been in badger setts.
According to PHE, transmission of the bacteria from infected animals to humans can occur by inhaling or ingesting bacteria shed by the animal or through contamination of unprotected cuts in the skin while handling infected animals or their carcasses.
However, PHE said it believed the risk of transmission from cats to humans was “very low”.
Professor Danielle Gunn-Moore, a researcher in feline medicine who has been studying the presence of TB in cats, warned that people had become complacent about watching for the warning signs of the disease because there have been relatively few cases in recent years.
“We’ve all become rather complacent because we haven’t been seeing TB for so many years but bovis is back with a little bit more significance,” she said.
“It’s important we don’t get blinkered and think it’s only badgers and cattle that get infected. This is a bacteria that is not very fussy about who it infects.”
She said she had dealt with cases in which dogs had also passed on Mycobacterium bovis to humans.
Nine cases of Mycobacterium bovis infection in domestic cats in Berkshire and Hampshire were investigated by the Animal Health and Veterinary Laboratories Agency (AHVLA) and PHE last year.
PHE said it had offered TB screening to 39 people identified as having had contact with the nine infected cats.
Of these, 24 people accepted screening. Two were found to have active TB and there were two cases of latent TB, which means they had been exposed to TB at some point but did not have an active infection.
Both people with active TB disease have confirmed infection with Mycobacterium bovis.
PHE said there have been no further cases of TB in cats reported in Berkshire or Hampshire since March 2013.
Analysis of the samples of active TB from the humans and the infected cats by the AHVLA showed the Mycobacterium bovis was “indistinguishable”.
This “indicates transmission of the bacterium from an infected cat”, PHE said.
In the cases of latent TB infection, it was not possible to confirm if they were caused by Mycobacterium bovis.
Dr Dilys Morgan, head of gastrointestinal, emerging and zoonotic diseases department at PHE, said: “It’s important to remember that this was a very unusual cluster of TB in domestic cats.
‘M. Bovis is still uncommon in cats – it mainly affects livestock animals.
“These are the first documented cases of cat-to-human transmission and so, although PHE has assessed the risk of people catching this infection from infected cats as being very low, we are recommending that household and close contacts of cats with confirmed M. Bovis infection should be assessed and receive public health advice.”
Professor Noel Smith, head of the bovine TB genotyping group at AHVLA, said: “Testing of nearby herds revealed a small number of infected cattle with the same strain of M. Bovis as the cats.
“However, direct contact of the cats with these cattle was unlikely considering their roaming ranges. The most likely source of infection is infected wildlife, but cat-to-cat transmission cannot be ruled out.”
Cattle herds with confirmed cases of bovine TB in the area have all been placed under movement restrictions to prevent the spread of disease.
Figures show that TB caused by Mycobacterium bovis is diagnosed in fewer than 40 people in the UK each year.
The majority of cases are in the over-65s, most likely due to a latent infection acquired years earlier becoming active again.