Bartonellosis (Cat-scratch Disease)
Overview of Cat-scratch Disease
Cat-scratch Disease (CSD), also known as Rochalimaea henselae or Bartonella henselae, is an infection in humans that most often occurs after prolonged contact with a young cat. When diagnosed in cats this disease is called feline bartonellosis. It is caused by a bacteria called Bartonella henselae.
Below is an overview of Bartonellosis (Cat-scratch Disease) followed by detailed in-depth information on the diagnosis and treatment of this disease.
All ages, breeds, and sexes of cat are susceptible; however, kittens under one year of age, kittens or cats infested with fleas, and feral cats or former strays are more likely to have the bacteria in their bloodstream. Fleas are believed to play a major role in cat-to-cat and possibly cat-to-human transmission. Cats can be infected with the organism for months, or even years, and never show any clinical signs.
Children and immunocompromised people may suffer severe disease when infected by these bacteria. Cats are considered the major reservoir for these bacteria, although fleas and some other mammals have also been shown to play a role in the disease transmission.
What to Watch For in Cats
Bartonella is not known to cause serious disease in most cats. Most cats will have no clinical signs of illness. Some cats may exhibit:
- Lack of appetite (anorexia)
- Reproductive difficulty
- Lymphnode enlargement
- Red eyes (uveitis)
What to Watch for in Humans
Signs of human disease include raised skin lesions that are red to purple in color. Anywhere from a few to over 100 may be found on the face, trunk, arms and legs. If cat scratch disease spreads internally, it can cause fever, weight loss and vomiting. Upon examination, the liver and spleen may be enlarged. Humans with immunodeficiency problems are at higher risk for disease.
Diagnosis of Bartonellosis
In people, definitive diagnosis generally requires a biopsy for microscopic examination and culture.
Other tests to diagnose the organism in cats might include:
- Blood culture
- Polymerase chain reaction (PCR)
- Complete blood count (CBC)
- Serum biochemical profile
- Feline leukemia virus testing (FeLV)
- Feline Immunodeficiency Virus Testing (FIV)
Treatment of Bartonellosis
Cats with no clinical signs of disease do not require treatment. Cats that have clinical signs of disease may be treated with antibiotics and supportive care as needed. There is not a lot of information about treating this disease in cats and much of the information about treatment is extrapolated from studies in human medicine.
In people, cat scratch disease responds to several different oral antibiotics, such as erythromycin, clarithromycin, azithromycin and doxycycline. Antibiotics are usually given for 2 to 3 months unless there is bloodstream or internal organ involvement. In advanced HIV (AIDS) disease, long-term management with lower doses is usually necessary to prevent relapse.
Home Care and Prevention
There is no home care for bartonellosis. Preventive care is based on maintaining good hygiene. Wash your hands after handling pets and wash scratches or bites thoroughly. Never let a cat lick an open wound, and maintain meticulous flea control. Preventative flea and tick control is recommended. For more information read , flea and tick control programs
Blood cultures and serology should be performed on pets belonging to immunocompromised people.
In-depth Information on Feline Bartonellosis
There are several Bartonella subspecies that can infect humans. Bartonella organisms cause a wide range of clinical diseases in people including the following:
Bartonella henselae is the causative agent of cat-scratch disease in humans.
Bartonella vinsonii, Bartonella elizabethae, Bartonella washoensis may cause endocarditis in humans.
Bartonella clarridgeiae may cause cat scratch disease in humans.
Bartonella bacilliformis may cause Carrion’s disease, Oroya fever and/or verruca peruana in humans.
Bartonella quintana may cause endocarditis, bacillary angiomatosis and or trench fever in humans.
Children and immunocompromised people may suffer severe disease when infected by these bacteria. Cats are considered the major reservoir for these bacteria, although fleas and some other mammals have also been shown to play a role in the disease. Most cats do not show clinical signs of illness when infected.
Cat-scratch disease was first described in 1950, but it was only in 1992 that the cause of the disease was identified. The organism responsible for the disease was called Rochalimaea henselae initially, but the organism was renamed Bartonella henselae shortly afterward.
In a study in 1993, children aged 5 to 14 years had the highest incidence of disease. Children younger than 18 made up 54 to 80 percent of CSD cases. The incidence of CSD is slightly higher in the southern United States and slightly lower in the western states. Sixty percent of cases occur from September through January.
Most cases of CSD begin with a cat scratch, although some cases have occurred in people who insist they haven’t been exposed to cats or other animals. The variables most strongly associated with CSD include owning a kitten, owning a kitten with fleas, and/or being scratched by a kitten. There are a few reports in which dog scratches were implicated, and one case that may have occurred after a monkey scratch.
After a cat scratches a person, a small blister may appear 3 to 30 days later, and may or may not persist for as long as 5 months before healing. Five to 50 days after the scratch, lymph nodes near the region of the scratch enlarge and become painful. The enlargement may persist for as long as 4 months and is the main reason that people seek medical care. Atypical forms of CSD can also occur, including tonsillitis, encephalitis, and pneumonia, although this is fairly uncommon and occurs in only 5 to 8.5 percent of cases.
Neurologic signs occur more commonly in children. These usually begin with a headache, and can progress to delirium. Many patients have seizures. Recovery is usually rapid, and long-term neurologic deficits are rare. HIV-positive individuals are more likely to show signs of dementia after infection.
Bartonella organisms can cause other diseases in people. Bacillary angiomatosis and bacillary peliosis hepatis are two examples. Bacillary angiomatosis is a vascular disease of the skin that appears as multiple blood-filled cysts. It resembles Kaposi’s sarcoma clinically. Bacillary peliosis hepatis is a vascular disease of the internal organs, causing fever, chills, vomiting and weight loss. These disorders tend to occur in people with advanced AIDS, and they tend to be refractory to treatment. One-third of patients with bacillary angiomatosis report no contact with cats. Studies have shown, however, that owning a cat and/or being scratched, bitten or licked by a cat are risk factors associated with both of these syndromes.
The prevalence of Bartonella infection in cats varies throughout the world. Twenty-five to 40 percent of pet cats are estimated to be healthy carriers of the organism. Feral cats have the highest likelihood of testing positive. Cats with a heavy flea burden are also more likely to test positive. Cats who test positive for the Feline Leukemia Virus or the Feline Immunodeficiency Virus are not more likely to test positive for bartonellosis.
Cats can have high levels of the Bartonella organism in their bloodstream and not show any clinical signs of disease. In experimental circumstances, mild clinical signs have been produced in cats after inoculating them with the organism. The signs seen were mild fever and lymph node enlargement that went away on its own.
Exactly how the organism is transmitted is still puzzling. Cats seem to get infected by flea infestation, or by blood transfusion from another infected cat. Fleas from cats who have the organism in their bloodstream have cultured positive for the organism as well. Pregnant cats that are infected do not seem to transmit the infection to their kittens transplacentally. Because fleas may carry the organism, human infection with Bartonella from fleas is theoretically possible; however, this has not yet been documented. Live Bartonella organisms are excreted in flea feces, and very recent research has shown that flea feces is the major transmitting agent from an infected and susceptible cat.
Cats rarely show signs of illness related to bartonellosis, and therefore are rarely tested for the disease. Testing is more likely to be performed on people suspected of the disease, although the same tests are applicable to cats.
- Blood culture. Culture of the blood for Bartonella organisms may be performed on humans as part of the evaluation of suspected cases of CSD. It may also be performed on cats suspected of harboring the organism. Blood culture can be difficult and prolonged.
- Serology. Serologic tests detect antibodies to Bartonella and imply exposure or infection with the organism.
- Polymerase chain reaction. This test is currently limited to special institutes and research laboratories, although it promises to be the most specific test for bartonellosis, and can distinguish between all of the Bartonella species.
- Complete blood count (CBC) is often normal in most cats. A mild anemia may be present in some cats.
- Serum biochemical profile is normal in most cats.
- Urinalysis is normal in most cats.
- Feline leukemia virus testing (FeLV) may be recommended to determine if coinfection exists or this disease is a cause for the underlying symptoms.
- Feline Immunodeficiency Virus Testing (FIV) may be recommended to determine if coinfection exists or this disease is a cause for the underlying symptoms.
Treatment in Cats
- Antibiotics. For cats that are symptomatic, antibiotics are recommended. The most commonly used antibiotic is Azithromycin (Zithromax®) although tetracycline, Erythromycin, Rifampin (Rifadin®, Rimactane®), Doxycycline (Vibramycin®) or a combination of these antibiotics has been used effectively in cats. Treatment for 4 to 5 weeks is often recommended. There is no known treatment that clears infection in cats.
- Supportive care including intravenous fluids and drugs to control vomiting may be needed.
Treatment in Humans
Treatment of Bartonella-related disease in people depends on the severity of the disease and the immune status of the patient. Cat-scratch disease is usually self-limiting and will resolve on its own in weeks or months.
- Antibiotics. If a secondary bacterial infection is present, or if the patient is immunocompromised, antibiotic therapy is prescribed. Treatment is for 4 to 8 weeks in people with competent immune systems, and is extended to 8 to 12 weeks in people who are immunosuppressed. HIV positive people may require treatment for many months, and sometimes for life.
Follow-up Care for Cats with Cat Scratch Disease
Optimal treatment for your pet requires a combination of home and professional veterinary care. Follow-up can be critical, especially if your pet does not rapidly improve. Administer all prescribed medications as directed. Alert your veterinarian if you are experiencing problems treating your pet. Preventative flea and tick control is recommended. For more information read , flea and tick control programs
Because of the uncertain effectiveness of these antibiotics, it is recommended that affected pets have cultures performed at two to four week intervals to determine drug effectiveness. Cultures should also be taken three weeks after discontinuation of antibiotics.
Because domesticated cats are a major source of the bacteria, common sense and good hygiene should be practiced, such as washing hands after handling pets. Scratches or bites should be cleaned thoroughly, and cats should never be allowed to lick a person’s open wounds.
Cat-scratch Disease is uncommon. Most people will never develop illness due to Bartonella henselae, and people with competent immune systems do not need to follow special precautions with their pets.
Although routine blood cultures and serologic testing is not widely available, it should be considered for pet cats whose owners are immunocompromised. Currently, the veterinary schools at the University of Georgia, Louisiana State University, Purdue University, North Carolina State University and Texas A & M University offer some method of diagnostic testing for cats. If a cat tests negative for Bartonella antibodies, it is unlikely to have the organism in the bloodstream, and may be a good criterion for choosing a pet for an immunocompromised person. Flea control may be the most important factor in reducing cat-to-cat and cat-to-human transmission, and is highly recommended for all pet cats.