Cat Scratch Disease

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Cat Scratch Disease | Jean Dodds, DVM

The colloquial name for bartonellosis, cat scratch disease (CSD) typically caused by the bacterium, Bartonella henselae, is possibly the most mischaracterized description for any disease out there. Yes; scratches from cats that carry Bartonella spp. can cause bartonellosis in humans, but the name does not identify the actual vector source, namely – cat fleas. In fact, insects are the primary vectors of many Bartonella bacteria that infect humans. For example, Bartonella quintana causes trench fever and spreads through body lice. Bartonella bacilliformis causes Carrión’s disease and is transmitted through certain
sand flies in parts of South America.

It is also fascinating that each of these forms of bartonellosis can produce a skin reaction in humans. Trench fever causes a rash along with fevers and headaches. Phase two of Carrión’s disease creates lesions to appear under the skin as nodular growths, then emerge from the skin as red-to-purple vascular lesions that are prone to ulceration and bleeding. CSD can cause pustules in humans.

What about CSD symptoms in cats?

It is estimated that 40% of cats have Bartonella bacteria at some point in their lives. However, although the majority of infected cats are asymptomatic, they are subclinical carriers of CSD. If the disease progresses in cats, it is usually self-limiting (heals on its own) and transient, lasting approximately 48-72 hours. Extremely rare instances of more serious infection include symptoms such as  fever, vomiting, lethargy, red eyes, swollen lymph nodes, and/or decreased appetite.

By the way, cats and dogs can be infected with other Bartonella strains besides CSD, and dogs can also be infected with CSD. Specifically regarding CSD, dogs are more likely to present clinical symptoms as compared to cats, namely, fever, endocarditis and myocarditis, granulomatous lymphadenitis, cardiac arrhythmias, granulomatous rhinitis and epistaxis.

How do cats transmit CSD to humans?

Always remember that cat fleas are essential to transmit CSD to humans. B. henselae multiplies in a flea’s digestive tract. When the flea defecates, B. henselae bacteria will then survive for several days. So, when cats scratch their bodies and subsequently scratch someone, the person could now be infected with CSD. If a cat grooms and then bites someone, the same result is possible. Additionally, CSD transmission can occur if a flea infested cat licks an open wound.

CSD symptoms in humans

Please bear in mind that CSD in humans is usually self-limiting and progresses slowly. In fact, doctors only test for CSD when the disease is severe, and suspect s CSD based on the patient’s symptoms, medical history and immune system. Otherwise, CSD is typically not treated in healthy people.

After the skin is broken, infection can occur at the site of the scratch within 3-14 days. The site may appear swollen and red, have round lesions and be pus-filled. Fever could also be present as well as headache and poor appetite. Again, it is self-limiting the majority of the time.

If the disease progresses, a person’s lymph node(s) closest to the original scratch or bite can become swollen, tender, or painful.

Only in extremely rare cases does the disease progress to affect the brain, eyes, heart, liver or other internal organs. This is more likely to happen in children or people who are severely immunocompromised or have cancer. Regarding immunocompromised patients, their bodies usually cannot keep the bacteria contained to their regional lymph nodes, thereby allowing to spread to other parts of the body.

Incidence of CSD in humans

The Centers for Disease Control and Prevention (CDC) published a review of cases from 2005-2013.

  • 13,273 patients with a diagnosis of CSD: 12,735 outpatients and 538 inpatients.
  • Highest average annual CSD incidence for outpatients and inpatients was among children 5–9 years of age.
  • The largest proportion of diagnoses was made during January, followed by August–November.
  • Incidence was highest from Texas to Florida, Maryland and Kentucky being the most northern states affected.
  • Incidence was lowest in the more arid Mountain states.

Clearly, the statistical evidence shows a direct correlation between climate and flea load, which indicates the number of people who might be at risk to develop CSD.


Are you thinking you may want to have your cat declawed now? Please don’t. The CDC recommends washing the infected area after the scratching or biting incident occurred. If a child’s symptoms do develop, please go to your healthcare provider. Indeed, declawed cats are four times more likely to bite if they perceive danger. So, the chances of preventing CSD with the declawing option are really not decreased, and may create the opposite situation of increased exposure risk.

The CDC goes on to state for people who are immunocompromised:

If you’re HIV-positive, are being treated for cancer, or have any other condition that might disrupt your immune system, you can keep your cat. Just keep the following points in mind:

  • Keep the cat indoors.
  • Avoid rough play with cats and situations in which scratches are likely. Declawing is not recommended.
  • Promptly wash any cat scratches or bites with soap and water.
  • Avoid contact with fleas.
  • Treat the cat with a flea control product recommended by your veterinarian.
  • It’s not necessary to test or treat a healthy cat for Bartonella.
  • If you are getting a cat, make sure it’s at least a year old, in good health, and free of fleas (kittens are more likely to carry B. henselae). Avoid stray cats and cats with flea infestations.

New findings include the fact that ticks may also carry the B. henselae bacteria too. So, it really all comes down to flea and tick prevention.

W. Jean Dodds, DVM
Hemopet / NutriScan
11561 Salinaz Avenue
Garden Grove, CA 92843


Bartonella Infection (Cat Scratch Disease, Trench Fever, and Carrión’s Disease). Centers for Disease Control and Prevention, 21 Mar. 2016,

Chomel, Bruno, et al. “Bartonella Spp. in Pets and Effect on Human Health.” Emerging Infectious Diseases, vol. 12, no. 3, Mar. 2006, pp. 389–394., doi: https://10.3201/eid1203.050931.

Hofve, Jean. The Cat Lover’s Anti-Declawing Handbook. Vetwise Publishing, 2017,

Martell-Moran, Nicole, et al. “Pain and Adverse Behavior in Declawed Cats.” Journal of Feline Medicine and Surgery, vol. 20, no. 4, 1 Apr. 2018, pp. 280–288., doi:

Nelson, Christina, et al. “Cat-Scratch Disease in the United States, 2005–2013.” Emerging
Infectious Diseases
, vol. 22, no. 10, Oct. 2016, doi:

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