First documented cases of cat-to-human transmission of TB

Siouxsie Wiles has alerted Sciblogs readers to the first documented cases of cat-to-human transmission of TB.

She refers to a paper just published in the Veterinary Journal which documents the first cases of transmission of Mycobacterium bovis (the bacterium responsible for TB in cattle and many other species) to humans.

She also advises:

Before anyone get’s into a panic, it was a year ago.

The article is behind a paywall, but according to the free abstract a vet practice in Newbury, in the UK, diagnosed nine domestic moggies with M. bovis infection between December 2012 and March 2013.

The nine cats ‘belonged’ to different households and six of them resided within a 250 metre radius.

The animals presented with varying symptoms and severity and 6 were euthanased or died, while the three surviving animals were responding well to treatment. At the time of the article, no new cases had been detected in local cats since March 2013.

As people can become infected with M. bovis, Public Health England offered to screen 39 people identified as having come into contact with the infected moggies. 24 people accepted their offer; 2 people were found to have active M. bovis TB (this means they would be infectious), while another 2 people were found to be latently infected (and therefore not infectious). All are reported to be responding to treatment.

Molecular analysis has shown that the M. bovis isolated from the infected cats and people with active TB infection were indistinguishable, indicating transmission of the bacterium from an infected. The same strain has also been found in cattle from nearby herds, although according to Professor Noel Smith, Head of the Bovine TB Genotyping Group at the UK Animal Health and Veterinary Laboratories Agency, the cats are unlikely to have caught if directly from the cattle but from infected wildlife. He probably means badgers.

Pet dogs, pigs and even a few ferrets also have been diagnosed with TB.

Wiles puts the numbers in perspective, citing DEFRA data showing the number of cattle compulsorily slaughtered in 2013 alone because they tested positive for M. bovis, or are direct contacts of positive animals, as reactors or direct contacts was 32,620.

The cats therefore are just a drop in the ocean. But the case does show though the versatility of M. bovis, when it comes to picking a host. It also shows that we share our microbes with our pets, for better and worse, Wiles concludes.

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