If you live in one of the 9 million French households with a feline, and your last attempt at petting ended in a paw, beware of cat scratch disease. This zoonosis (pathology affecting animals) is caused by a bacterium called Bartonella henselae, which is very common in cats.
It is estimated that between 20 and 30% are infected in France, kittens being particularly at risk. For the animal, no problem, this contamination is asymptomatic but, consequently, it is impossible to detect its presence, notes Gilbert Greub, director of the Institute of Microbiology at the University of Lausanne and specialist in zoonoses. Estimates indicate a rare disease of 1.8 to 9.3 cases per 100,000 population.
On the occasion of a scratch or a bite, this germ will be inoculated under the skin and carried by the lymphatic vessels. It is also a swelling of the lymph nodes (adenopathy) which should alert and lead to consultation with a general practitioner. This inflammation can last up to several months, and if it is very acute or prolonged, an antibiotic will be prescribed.
In 5-10% of cases there may be more severe complications. Gilbert Greub sees patients who may have, for example, heart valve diseases, bone infections or retinal infections. This happens if the bacteria has spread through the blood and reached these different organs.
When the specialists receive a patient for whom they suspect this disease, the confirmation will be done by PCR test; we will highlight a DNA sequence specific to Bartonella henselae. The principle of the test is the same as that, well known and very widely used, to diagnose Covid-19. Serology is also performed to look for specific antibodies to this type of bacteria. It is also possible to carry out a culture in the laboratory. This is not the preferred method, because this germ does not grow well in culture, which explains why it was only identified as responsible in 1983.
Once the pathogen has been clearly identified, and if the infection is severe, antibiotics are administered intravenously for four to six weeks. While the treatment can be cumbersome, it usually works very well, and the patient recovers.
Cat scratch disease is part of a larger family called bartonellosis, all of which are caused by bacteria of the Bartonella genus. Each species has a specific reservoir (dog, rodent, human) and can be transmitted either by direct contact or by a vector, such as the louse. It was via this parasite that trench fever weakened hundreds of thousands of soldiers during the two world wars. It is still present today among disadvantaged people, especially the homeless.
One might think that a simple prophylactic solution against bartonellosis would be to treat reservoir species, such as our pets, but since they do not show any particular symptoms following an infection, this would amount to administering doses of antibiotics. very regularly. This would be totally counterproductive by facilitating the phenomenon of antibiotic resistance. So let’s be careful if you’re dealing with a cat that’s a little too aggressive!
