Feline Bartonella: Beyond Cat Scratch Disease

The Bartonella genus of bacteria is a group of “bugs” rapidly developing a reputation as “stealth” pathogens. There are many different species worldwide, possibly 30 or more1, and cause such diverse diseases in different animal hosts that they may be overlooked in a sick cat. They may also be confused for other problems like Lyme Disease or immune mediated hemolytic anemia (which seem more common).

Even when Bartonella is suspected of making a dog, cat or person sick, the bacteria can be hard to confirm. Repeated testing of the blood or of affected organs is often needed to diagnose bartonellosis.

What makes Bartonella stealthy?
Bartonella organisms stay under the radar, and avoid being eliminated by the immune system by hiding inside circulating blood cells or blood vessels in relatively low numbers, and reproducing slowly. Infectious disease specialists believe that many vectors, such as ticks, fleas, lice or, even spiders, might be able to indirectly spread the infection between wildlife and pet animals or from animals to people. And they worry that veterinarians and physicians don’t often think about Bartonella when confronted with a sick patient.

What is cat scratch disease?
You may have heard of cat scratch disease: a mostly self-resolving illness causing fever and swollen lymph nodes in people. It’s caused by B. henselae and acquired from the scratch or bite of an infected cat, or possibly even from happy cat kisses or licks on broken skin. It is described here by the CDC. Cat scratch disease is a common Bartonella scenario and familiar to health care professionals, but Bartonella doesn’t always present this way. There are diverse syndromes in people, dogs and cats caused by atypical infections of this species and others, some of which may be fatal.

Infection with Bartonella sp. may cause:

  • Chronic pain and fatigue syndromes (people)
  • Memory loss, headache, insomnia (people)
  • Nervous system inflammation (meningitis, encephalitis)
  • Intermittent fever
  • Chronic lymph node inflammation and swelling (lymphadenitis)
  • Chronic joint swelling (polyarthritis)
  • Liver inflammation (peliosis hepatis, granulomatous hepatitis)
  • Bone infection (osteomyelitis)
  • Inflamed heart muscle or valves (endocarditis, myocarditis)
  • Severe skin rash (vasculitis)
  • Low blood platelets, anemia , high or low white blood cells
  • Red blood cell destruction (hemolytic anemia)
  • Tumors (oncogenic transformation)

Diagnosing Bartonella infection
Testing for most Bartonella related infections will begin with these basic tests:

  • A complete blood count (CBC) to screen for infection, inflammation, anemia, or low platelets
  • Chemistry and electrolyte tests to evaluate kidney, liver and pancreatic function, as well as sugar levels, salt and water balance
  • Urine tests to screen for urinary tract infections, protein loss and to evaluate the kidney’s ability to concentrate urine
  • Thyroid function tests
  • Routine screening for Feline Leukemia Virus (FeLV) and Immunodeficiency Virus (FIV)
  • Specialty cultures or PCR testing, if necessary, to confirm infection, as discussed below

The diagnosis of bartonellosis can be challenging. Veterinarians must submit blood or tissue samples for specialized testing. Diagnosis is further complicated by unreliable antibody production. Many apparently healthy cats have elevated antibody levels and carry the bacteria: 25-41% of cats will be culture or PCR positive for Bartonella depending on where they live1. As a natural “reservoir” host (the bacteria live without causing much illness) most cats are not expected to be sick, even if they are chronically infected. Testing and treatment is usually reserved only for sick cats (who are likely infected with a more aggressive or virulent strain of Bartonella).

Treatment of Bartonella infection
A long course of a combination of oral antibiotics is the treatment most often recommended for symptomatic bartonellosis. Patients with heart muscle, bone infections or other severe disease presentations may need in-hospital treatment with antibiotics given by injection and aggressive supportive care. Fortunately, cats with a healthy immune system should be able to recover if they respond well to treatment. For patients with concurrent infections, organ failure or cancer, the prognosis is more uncertain.

Prevention of Bartonella infection
Preventing these stealth infections begins with rigorous flea and tick control2. Many of the Bartonella group bugs thrive in a wildlife species, such as a rodent, rabbit or coyote. These reservoir hosts can carry the infection without getting very sick. Then fleas, ticks or other arthropods might transmit the infection to an “accidental” host such as a dog, cat or person, who is perhaps more likely to develop severe illness. Your veterinarian will be happy to discuss practices to limit the four- and two-legged family’s exposure to fleas and ticks. And she can recommend products that are working well in your community.

Flea feces (aka,” frass” or “dirt”) can transmit the Bartonella bacteria directly into broken skin, as can a tooth or tiny claw. Yep, flea feces can be dangerous, as well as gross! So cleaning any scratches or bites well and washing your hands after handling animals with fleas or contacting flea dirt is a good idea. (Finally, I have a reason to vacuum that I cannot ignore.) Since apparently healthy dogs and cats can also harbor the bacteria in their bloodstream, teeth and mouth, it’s good practice to avoid contact with their bodily fluids, including saliva. Unfortunately, that means limiting kisses and licks from your favorite furball. There’s nothing wrong with blowing kisses, though!

Ultimately, staying on top of your cat’s health status and the need for any detective work to find a stealth infection will be directed by regular preventive care visits to the vet. Your vet will be your partner in the quest for a happy, healthy pet-family.


  1. Proceedings of the Potomac Regional Veterinary Conference. Nov 7-9, 2014 Baltimore, MD in Cat Scratch Disease and Feline Bartonellosis presented by Edward Breitschwerdt.
  2. Chapter 52 Canine Bartonellosis, Edward B. Breitschwerdt and Bruno B. Chomel . P. 562 in Infectious Diseases of the Dog and Cat, 4th edition. Craig E Greene , 2012 St. Louis MO, Elsevier Saunders.

If you have any questions or concerns, you should always visit or call your veterinarian -- they are your best resource to ensure the health and well-being of your pets.


Cats living in areas where fleas or ticks are very common, and corresponding to about 30% to 50% of the total, are highly exposed to Bartonella bacteria, a zoonosis that is transmitted from cats to dogs and man. Bartonella Henselae is a single-celled gram-negative bacterium that attacks red blood cells, causing Bartonella infections or bartonellosis.[1].

Bartonella is transmitted to cats by a vector

Vector transmission occurs in two primary ways: inoculation of Bartonella-contaminated arthropod feces via animal scratches or bites or by self-inflected contamination of wounds induced by the host scratching irritating arthropod bites. [2].

The vector is usually a flea or tick, after the infection, cats can easily infect other species. This pathology is called Cat scratch disease (CSD), because that is how it is transmitted.

Bartonella infection is more likely to cause clinical symptoms in dogs compared to cats. Dogs develop a wide range of clinical and pathologic abnormalities, including: fever, endocarditis and myocarditis, granulomatous lymphadenitis, cardiac arrhythmias, granulomatous rhinitis, and epistaxis, while most cats infected with Bartonella, often appear clinically healthy[3].

Is there a therapy to treat Bartonella in dogs and cats?

There is no standardized antibiotic protocol for treatment of bartonellosis in cats or dogs, but doxycycline, amoxicillin, enrofloxacin, and rifampin given for a long duration (4-6 weeks) may be effective in reducing the level of bacteremia in the infected cats or dogs.[4].

Bartonella: from cats to dogs to humans

Being a zoonotic disease, it can be transmitted between animals and humans. This disease is not fatal for humans, but it can represent a great risk for immunocompromised patients, such as AIDS patients in whom severe disseminated disease may occur.
The infection is transmitted ever by a bite or a scratch and generally children are more affected. After 3-10 days from the bite or scratch, most patients develop an erythematous, crusty papule (rarely a pustule) at the site of the scratch, while within 2 weeks a regional lymphadenopathy develops.
A certain diagnosis can be obtained with a PCR test or lymph node biopsy.
The treatment of CSD in immunocompromised patients consists in the local application of heat and analgesics. If the lymphonode is floating, aspiration with a syringe usually relieves pain.
Antibiotic therapy does not give clear benefits and generally should not be given in localized infections in immunocompetent patients. [5]

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Causes and symptoms of CSD

This bacterium can be transmitted by an infected cat to a completely healthy one. Therefore, direct contact is the primary cause of the infection. The disease is also carried by fleas, which excrete it through their feces.

So, what that means is that even if your feline companion doesn’t come in contact with a cat that has a Bartonella infection, she can still get fleas from the outdoors, for example, and develop the disease.

Most cats don’t show any symptoms at all, which makes this zoonosis even more dangerous to humans as they might not even realize when they become infected. There are cats that present some clinical signs, and they consist of fever, swollen glands, and muscle aches.

The infection can be transmitted to other cats or humans through the animal’s saliva. Therefore, if you get bitten or scratched by a cat, you should keep in mind that you could develop Bartonellosis.

It’s important to note that CSD is more common in strays and kittens, as they are more susceptible to become bacteria carriers due to flea infestations. This bacteria can be found more predominantly in warmer regions, which make it more possible for fleas to thrive.

To date, it is estimated that approximately 40% of all cats can carry this bacteria at one point in their lives, especially when they are young. Fortunately, the infection is rarely fatal, in both cats and humans.

How do people become infected?

Since the bacteria can be transmitted through saliva, a cat bite is the most likely way of transmission. However, some cats can carry the germ under their nails, particularly after having fought with another outdoor cat, for instance. Therefore, even if your cat scratches you on a superficial level of the skin, you could still become infected.

The people that have the highest risk of becoming infected are those that have weakened immune systems, such as seniors and children younger than the age of 6.

While most people can be asymptomatic and the infection could resolve on its own, it can be quite problematic in certain categories of individuals who have a depressed immune system, such as those who have AIDS, those that have received a transplant, or those that have cancer or diabetes.

Even though the infection can be mild in most humans, the CDC estimates that approximately 12,000 individuals become infected with CSD in the United States alone over the course of a year. Out of these, around 500 end up being hospitalized. Many of those that are infected are children, as they’re more likely to play with strays or kittens that might bite or scratch them as part of their play behavior.

Symptoms in humans

After sustaining an injury such as a bite or a scratch, people can be asymptomatic for a period of one to two weeks. In some cases, it might take as many as eight weeks for the symptoms to become apparent.

Here are some of the typical clinical signs that infected people might show.

  • Red and round bumps or papulae at the site of the bite or scratch
  • Swelling of the lymph nodes
  • Swelling and the appearance of an infection at the bite site
  • Chills and fever
  • Lack of appetite
  • General malaise
  • Muscle pain

Around 11-12% of the patients develop more severe symptoms, which consist of conjunctivitis, a variety of neurologic manifestations (seizures, encephalopathy, paraplegia, and others), and very rarely, liver disease (hepatosplenic granulomatous disease).

Patients that have a history of heart disease can also develop endocarditis. Since one of the symptoms that we have mentioned is the inflammation of lymph nodes, we’d also like to note that it can take between 2 and 5 months for the lymphadenopathy to subside. Usually, it does so spontaneously and without any apparent reason.

How can the infection be treated?

It’s very likely that cats won’t show any symptoms at all or that the infection will resolve on its own without you even noticing anything. If you’re lucky enough not to be bitten or scratched by your feline companion or by a stray when they are still infectious, you might not develop the disease, either.

Even in humans, the infection is generally benign, and it typically disappears on its own over the course of a couple of months. The bumps or blisters can remain on the patient’s skin for up to three weeks, while the swollen lymph nodes take a while to recover, as we have previously mentioned.

However, since some of the symptoms associated with this disease are fever, muscle aches, and general malaise, go see your doctor as soon as you can. Some of the individuals that have more serious symptoms or those that are known to have a weakened immune system can receive treatment with antibiotics.

How to prevent CSD

If you know that you have an immunocompromised individual living in your home or if you have a weakened immune system yourself, you should get your cat tested before adopting her and bringing her home.

Indoor cats have a considerably lower risk of being Bartonella carriers, because they usually come in contact with no other animals that could infect them, neither are they exposed to flea feces if you practice good flea control.

If you have been bitten or scratched by a cat, you should disinfect the wound as soon as possible. Also, if you notice any symptoms such as fever or swollen glands in your cat, call your veterinarian, and schedule an appointment.

Keeping your home flea-free and making sure that your cat has trimmed nails are two other pieces of advice that we can give you. If you haven’t gotten your cat tested yet, avoid engaging in rough play with your feline companion, and more importantly, avoid playing with strays.

To date, there is no vaccine against this infection in both humans and cats.

Bartonella henselae and Bartonella charridgeidae are the cause of the cat-scratch disease (CSD). The bacteria are intracellular, fastidious, and gram-negative bacterium. The disorder is presumed to be flea transmitted.

Symptoms of Benign lymphoreticulosis

The most common symptoms of benign lymphoreticulosis are:

  • A small skin wound ( resembling an insect bite ) develops at Cat scratch’s site or ( less commonly ) a cat biting, followed within two weeks by swollen lymph nodes and sometimes a fever.
  • The illness is mild and self-limiting in most patients, although it may take a few months for the enlarged lymph nodes to return normal.
  • Occasionally, CSD may be associated with tonsillitis, encephalitis, hepatitis, pneumonia, and other serious illness.
  • Fatigue, headaches, and body ache in humans.

Less common symptoms of cat scratch disease are:

  • Anorexia.
  • Sore throat.
  • Weight loss.

Diagnosis of Bartonellosis in Cats

Diagnosis is made on the history of exposure to a cat and the presence of typical clinical signs. When a cat bites or scratch you, tell your vets, and they may diagnose you with the help of signs and symptoms. The best diagnosis method is available for a polymerase chain reaction (PCR), examining tissues, e.g., a biopsy of swollen lymph nodes.

Cat-scratch Disease Treatment

Your veterinarian should do treatment and testing. Your experts can tell you whether your pets required testing and treatment. In most cases, cat-scratch fever is self-limiting, and the disease does not require antibiotics therapy. if an antibiotic is select to treat the disease, Doxycycline or Enrofloxacin should be used for 2 to 4 weeks, and follow-up cultures should be taken to confirm its effectiveness.

Symptoms of cat scratch disease typically start around the location of the area where the scratch occurred (typically the hands or arms). Oftentimes, there will be swelling, redness and pain.

Symptoms may eventually progress symptomatically to include enlarged lymph nodes, fever, nausea and even neurological problems. While more common in elderly or immunocompromised individuals, everyone is susceptible to Bartonella infection and should seek medical intervention if noticing these symptoms.

Watch the video: What You Need to Know about Cat Scratch Disease (July 2021).