Bartonella in Cats: Causes, Symptoms, and Treatment

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Fleas are infamous for passing diseases to their animal hosts. They can even pass dangerous bacteria, such as Bartonella, onto unsuspecting cats.

Bartonella is the name for several similar bacteria that can infect cats and lead to illness in people known as “cat scratch disease” or “cat scratch fever.” In this article, you’ll learn what Bartonella is and the effects it may have on both cats and people.

Other Names: Bartonellosis, Cat Scratch Disease, CSD, Cat Scratch Fever

Common Symptoms: Many cats are asymptomatic. Some may develop a fever, enlarged lymph nodes, neurologic disease, and retinal (eye) disease

Requires Ongoing Medication: No

Vaccine Available: No

Treatment Options: For sick cats where Bartonella infection is proven, antibiotics for up to 6 weeks. Several antibiotics have been used, there is not a proven or preferred one.

Home Treatment: Bartonella is transmitted by fleas; Regular use of flea prevention products and keeping cats indoors is the best prevention for cats. For people, always wash any cat scratch or bite wounds. Always seek care with a cat bite. If you feel sick after a cat scratches you, seek care from a human health provider.

What Is Bartonella in Cats?

There are several similar bacteria with the Bartonella name. Bartonella henselae is the most common Bartonella species carried by cats.^[4] It has also been known to cause cat scratch disease in people.

While there are 14 species of Bartonella that can cause diseases in people, only five are carried by cats. Besides Bartonella henselae, Bartonella clarridgeiae may also be involved. The other three species carried by cats rarely cause infection.

Causes of Bartonella in Cats

Bartonella is primarily transmitted to cats by fleas (Ctenocephalides felis). The bacteria can be present inside the flea. When the flea bites a cat, the bacteria can be transmitted into a cat’s bloodstream. Ticks may also be a potential vector. Tick transmission has not been studied as well, but is thought to be much less common.^[9]

The bacteria can also be present in flea dirt, which is another name for flea feces. Flea dirt is essentially digested blood that the flea excretes after feeding on a host animal like a cat. If flea dirt enters an open wound, this is another way Bartonella can infect a cat.

While a rare cause, a cat could also get infected with Bartonella if given a blood transfusion with blood from a cat that already carries the bacteria in their bloodstream.

Symptoms of Bartonella in Cats

Most cats that have been infected with Bartonella show no symptoms. Some studies estimate that up to 30-60% of cats in the US may be asymptomatically infected at some point in their lives.^[2]

Bartonella henselae especially is very host-adapted to the cat. This means that it can infect a cat without causing any signs of disease.

If a cat does get sick from a Bartonella infection, the most common result will be a temporary fever lasting 2–3 days.^[7]

Kittens less than six months of age are more likely to develop an active Bartonella infection compared to adult cats.^[2] Cats less than 2–3 years of age are more likely to have bacteremia, or Bartonella bacteria, in their bloodstream. Many of them will show no signs of illness.^[9]

It is possible for cats to carry the bacteria actively in their bloodstream for several months or even years at a time.

Complications of Bartonella

While rare, a cat may show more serious clinical signs of illness when infected with Bartonella. These signs can include:

• Fever
• Vomiting
• Diarrhea
• Lethargy
• Decreased appetite/anorexia
• Eye inflammation
• Enlarged lymph nodes
• Muscle aches or pain
• Reproductive failure
• Neurologic disease
• Endocarditis (bacterial deposits on heart valves causing heart disease)

Diagnosis of Bartonella in Cats

Your veterinarian will conduct a thorough exam to confirm a Bartonella diagnosis. Shutterstock.com

Diagnosis of Bartonella in cats can be tricky. There are a couple of different tests that can be used that provide different information.

1. Blood Culture

A blood culture is the most definitive way to detect Bartonella bacteria since they reside in the bloodstream. Cultures can also be obtained from an abnormal lymph node or an affected heart valve.

But the bacteria in infected cats may not always be detectable in the bloodstream. The cat may have Bartonella but the bacteria is not in sufficient quantities in the bloodstream to be detected. So it is possible for a culture to have a false negative result.

Culture samples can also be difficult to obtain and may take at least several days to return results.

2. Polymerase Chain Reaction (PCR)

Another method is by PCR. This method detects actual Bartonella DNA. This means the PCR is only likely to be positive if the bacteria is actually present. PCR is much less invasive, results return faster, and it is still a very sensitive test method.

However, a disadvantage to PCR is that, like the blood culture, a false negative result may occur if a cat does not currently have sufficient numbers of Bartonella bacteria in the bloodstream to detect.

3. Immunofluorescent Antibody (IFA)

IFA is a way of detecting antibodies that a cat’s body has produced in response to Bartonella infection. This method works very well for detecting cats that have been exposed to Bartonella.

However, a cat that has produced antibodies is not necessarily currently infected with bacteria in the bloodstream. Cats with really early infection may also have negative IFA testing because sufficient antibodies haven’t been produced yet.

IFA testing is best for ruling out Bartonella as a concern for infection or transmission to people. So while a cat with a positive antibody test may or may not have an active infection, a cat with a negative antibody test is very unlikely to have Bartonella currently or previously at all.

Treatments for Bartonella in Cats

Treating cats for Bartonella is somewhat controversial. Most cats infected with Bartonella exhibit no signs of illness and are otherwise healthy. A majority of those who do get sick have a mild, temporary illness lasting less than a week.

The one exception where treatment would be considered is a cat with one or more serious signs of illness where Bartonella has been proven to be the cause through testing.

In this case, treatment with one of several antibiotics may be recommended. There is no one antibiotic proven best for treating Bartonella, but ones that have been used include:

• Doxycycline
• Tetracycline
• Erythromycin
• Amoxicillin/clavulanic acid (Clavamox)
• Rifampin
• Enrofloxacin
• Azithromycin

Sometimes a combination of two antibiotics may be used. Antibiotic therapy for Bartonella in cats is longer than for some other infections. Treatment for 4-6 weeks is typical.^[8]

When treating a cat, the goal is to significantly reduce the presence of Bartonella bacteria in the bloodstream. This may lead to an improvement in some symptoms with the exception of more serious forms of disease.

It may not be possible to completely eliminate Bartonella from a cat’s body. There is no specific antibiotic, antibiotic dose, or length of treatment that has proven to completely clear infection. Cats that have been treated with antibiotics may develop relapses where Bartonella multiplies in the bloodstream again at a later time.

Because of this and because Bartonella can quickly develop resistance to antibiotics being used, prophylactic or empirical treatment of a healthy cat with Bartonella is rarely advised.

Cat Scratch Disease in People

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Cat scratch disease can be transmitted to a person if a cat scratches them with claws contaminated with Bartonella bacteria. It is also possible for a bite to cause this if Bartonella bacteria is present in the mouth. It could even happen if a cat licks an open wound on a person’s skin.

In healthy people, the area where the scratch occurred will develop a small swelling called a papule that appears red and crusty. Within another two weeks, lymph nodes closest to that area will swell and become painful. A fever also typically develops, lending to the alternate name “cat scratch fever”.

While uncomfortable, these Bartonella signs typically resolve on their own and most people make a complete recovery. Lymph node swelling may persist for a few months.^[6]

In people with a compromised immune system, cat scratch disease can have more severe consequences that include:

• Neurologic disease (encephalitis, seizures, paraplegia)
• Eye problems (retinitis, conjunctivitis)
• Spleen enlargement
• Endocarditis (infection of heart valves)

Antibiotics are usually only prescribed for people who have a compromised immune system and risk of more severe disease.

Cat Care Tips

In most cases, cats with Bartonella show no signs of illness and no special care is required. Even a cat confirmed to have Bartonella or previous exposure may need no treatment if there are no signs of illness.

If cats develop any signs of more serious illness, having this evaluated by a veterinarian is very important. Many of the more serious symptoms of Bartonella in cats can also be seen with other illnesses. It is important for a veterinarian to help you rule out other causes.

Prevention of Bartonella in Cats

To keep your cat and your family at a lower risk of contracting Bartonella, consider the following tips:

• Keep your cat indoors
• Use an appropriate flea prevention medication year-round
• Keep your cat’s nails trimmed (at least for indoor cats)
• Wash any fresh cat scratches on your skin immediately with soap and water
• If you develop any signs of illness after getting scratched by your cat, seek medical attention