cat scratch disease

Cat scratch disease is a bacterial infection transmitted to humans by cat scratches or bites.

Cat scratch disease is also called benign inoculation lymphoreticulosis. It is a zoonosis, that is to say a disease transmissible from an animal (in this case a cat) to a human being. Mostly benign, cat scratch disease may in some cases require the initiation of antibiotic treatment.

Definition and symptoms

What is cat scratch disease?

Cat scratch disease is a bacterial infection initially present in cats and transmitted to humans by scratching or biting, hence its name.

cat scratch

Cat scratch disease is present all over the world. Contrary to popular belief, it affects both domestic cats and wild cats.

To know ! Children are much more often affected by cat scratch disease than adults. Indeed, children easily tend to play with the cat and stroke it, sometimes abruptly, which increases the risk of scratches. The disease can also be transmitted by licking a wound, possibly present on the arms or legs of the child and easily accessible to the cat.

What are the symptoms of cat scratch disease?

Most of the time, symptoms appear after one to three weeks after contamination by an infected cat. This is the incubation period.

The symptoms are essentially local:

  • At the level of the scratch or bite, a papule, in other words, a small red pimple-shaped lesion appears. It usually leaves room for a pustule then a scab ;
  • The lymph nodes present near the scratch or bite area begin to swell in response to the infection, this is called one or more lymphadenopathy. The affected lymph nodes depend on the scratch area. For example, if the person is scratched on the arm, the lymph nodes that will swell are preferentially the axillary lymph nodes, located under the armpit. If the person is scratched on the leg, it is the groin glands, located at the level of the crotch, which will be affected.

More general symptoms are possible:

  • Fatigue ;
  • Decreased appetite;
  • Headache ;
  • Sore throat ;
  • Fever ;
  • Muscle and joint pain.

Infectious complications are rarer but also more serious, neurological, cardiovascular or even pulmonary. Patients must benefit from appropriate care to avoid the appearance of sequelae or even the death of the patient.

One example relates more particularly to persons suffering from valvular disease and/or wearing a valvular prosthesis. Indeed, cat scratch disease can lead to endocarditis in these people, that is to say an infection of the inner lining of the heart.

At last, Parinaud’s oculo-glandular syndrome is a particular form of cat-scratch disease, during which the bacteria are inoculated into the eye, for example when the person rubs their eyes with contaminated hands. Parinaud’s oculo-glandular syndrome combines conjunctivitis, swelling of the eyelid and swollen glands near the ear.

To know ! In people with a very weakened immune system, for example suffering from acquired immunodeficiency syndrome (AIDS), cat-scratch disease risks spreading and even leading to death in the absence of appropriate treatment.


What causes cat scratch disease?

Cat scratch disease is caused by a Gram-negative, intracellular bacterium called Bartonella henselae. This bacterium is present in the oral cavity of the cat and then settles on the coat and on the claws thanks to the licking carried out by the cat when grooming.


Cats are very often infected but show no symptoms. This is transmitted from one cat to another by fleas.

To know ! Kittens are the main reservoir of the bacteria Bartonella henselae. This is explained in particular by the fact that kittens are less often treated against fleas than adult cats.

Diagnosis and treatment

How to diagnose cat scratch disease?

The diagnosis of cat scratch disease is clinical in front of a typical form of the disease, including cat contact, scratching, or biting, as well as swollen glands. In this case, no additional examination is necessary.

To confirm the diagnosis, the doctor can prescribe a serology. This test checks the blood for the presence of antibodies against the bacteria. Bartonella henselae. If antibodies are present, it means the person is infected and their immune system is defending itself against the bacteria.

cat scratch

Other blood or imaging tests are performed on a case-by-case basis, depending on symptoms and/or patient profile.

To know ! Swollen glands, or adenopathies, can be a sign of other diseases, infectious or not. Thus, when a lymphoma (cancer of the lymphatic system) is suspected, a biopsy followed by a laboratory analysis can confirm or invalidate the diagnosis.

How to treat cat scratch disease?

Most of the time, cat scratch disease heals spontaneously, without treatment and without sequelae, after only a few weeks. On the other hand, the lymph nodes remain swollen sometimes for several weeks or even several months, some of them can evolve towards suppuration, that is to say the formation of pus.

No vaccine can prevent the disease. On the other hand, certain antibiotics can be prescribed to treat the infection in severe forms. Several antibiotics can be used against Bartonella henselaesuch as azithromycin. Respecting the rules for the proper use of antibiotics helps to guarantee their effectiveness: in particular, respecting the dosages and durations of treatment.

Several preventive measures can be put in place on a daily basis to avoid cat scratch disease:

  • Wash your hands after contact with a cat;
  • Brush your cat regularly;
  • Wash the lesions with soap and water, then disinfect with a local antiseptic ;
  • Consult urgently in case of eye damage;
  • Consult in the event of the appearance of local or general symptoms, so that a doctor confirms the diagnosis, verifies the tetanus vaccination and prescribes analgesics and/or antibiotics if necessary.

Children should be made particularly aware of cat scratch disease and the various preventive measures. However, it is useless or even harmful to separate them from their favorite animal.

To know ! It is important to treat your cat against external parasites and in particular against fleas because these can transmit microbes such as the bacterium Bartonella henselae. To do this, obtain external parasiticides adapted to the age and/or weight of the animal, in the form of pipettes, sprays or even collars. Apply pest control regularly because infestations can occur at any time of the year. Do not hesitate to seek advice from your veterinarian or pharmacist.

Florence D.-L., Doctor of Pharmacy


– Cat scratch disease. Accessed October 27, 2021.
– Cat scratch disease and other bartonellosis. Accessed October 27, 2021.
– Cat scratches. Accessed October 27, 2021.

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