Bartonellosis Infection (Cat Scratch Fever) Symptoms, Causes, Diagnosis And Treatments

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Bartonellosis in Cats – Definition

Bartonellosis, also referred to as feline bartonellosis or cat scratch disease in people, is an emerging world-wide disease caused by rod-shaped bacteria in the genus Bartonella. Bartonella henselae is the most common cause of feline bartonellosis and cat scratch fever.

The infective bacteria are carried in the saliva and feces of infected fleas and possibly other external parasites, which are called “vectors”. The vectors transfer the bacteria to cats in their feces and to dogs in their saliva while they feed.

Most cats with bartonellosis don’t actually get sick, or at least don’t show outward signs of illness; this makes them asymptomatic carriers of the infection. They do, however, frequently transmit Bartonella bacteria to humans through scratches (from infected flea or other parasite feces under the cat’s nails) and bites (through infected parasite feces in the cat’s mouth from licking and grooming).

Causes & Preventin Feline Bartonellosis Infection

How Cats Become Infected

Most companion cats are infected with Bartonella. There are five or more different types of Bartonella bacteria that are known to infect cats, the most common of which is Bartonella henselae.

It used to be thought that cats became infected with Bartonella through the saliva of inflected fleas after they fed. More recently, the consensus is that cats usually get Bartonella infection from the feces of infected Ctenocephalides felis fleas and possibly other external parasites, while dogs are thought to become infected from the saliva of infected ticks.

Ticks and fleas, which are considered “vectors” or carriers of this disease, become infected by feeding on animals that have Bartonella organisms in their bloodstream. When the vectors eliminate, their feces contains live Bartonella bacteria. Flea feces, also known as flea dirt, can be gathered under a cat’s claws while the cat scratches, and in its mouth from licking and grooming.

How the Disease is Transmitted

Many cats carry these bacteria without ever showing any noticeable symptoms of being sick. However, when cats are very young, elderly or have a suppressed or weakened immune system (such as cats with FIV or FeLV), or if they are in especially stressful, overcrowded environments or situations, they can become clinically ill from this disease.

Bartonella have a propensity to infect red blood cells, which are called erythrocytes, and certain cells of the skin. The bacteria are covered by small finger-like structures called pili, which help them stick to and then enter their target cells. Once the bacteria are inside, they disrupt the cells’ normal functions.

Potential Danger to Humans

Feline bartonellosis is not exactly a contagious or zoonotic disease. However, because the Bartonella bacteria can be transferred from cats to people in flea feces as a result of cat scratches and bites, it should be treated as a transmissible illness.

In most cases, people are resistant to developing infections from exposure to Bartonella henselae. However, those that have compromised immune systems definitely have an increased chance of developing so-called “cat scratch fever.”

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People who get cat scratch fever typically develop a raised red sore at the site of the scratch, lick or bite 3 to 10 days after exposure. The sore may progress to a red streak extending outward. Lymph nodes in the person’s neck, groin, armpits and/or elsewhere become tender and enlarged, which can persist for many months.

Symptoms of Feline Bartonellosis Infection

Effects of Bartonellosis on Cats – From the Cat’s Point of View

Feline bartonellosis, which involves infection with a genus of bacteria called Bartonella, can cause a variety of symptoms, although most affected cats don’t actually develop observable signs of being sick.

In many cases, the disease is confused with some disorder of the cat’s immune system – these are called “immune-mediated diseases.” Those cats that do get sick from this disease typically develop vague symptoms which mimic those of other non-specific disorders.

Kittens under one year of age, older cats and cats with weak or suppressed immune systems are the most likely to become ill from Bartonella infection. When symptoms do develop, this disease usually affects multiple bodily systems, with inflammation being the most consistent and widespread problem.

Some areas of a cat’s body that can be affected by bartonellosis include the respiratory system, digestive system, neurological system and cardiovascular system, as well as the mouth, skin and especially the lymph nodes.

The cat’s mouth and gastrointestinal lining may become swollen and inflamed, and it may experience breathing difficulties such as shortness of breath and labored breathing.

Still, most cats infected with Bartonella won’t show any signs of being sick, and their owners probably will never know that they have these bacteria circulating in their bloodstream.

Symptoms of Bartonellosis in Cats – What the Owner Sees

Bartonella organisms tend to invade red blood cells and some other cells. While most cats are asymptomatic, which means that they don’t show outward symptoms of illness, when symptoms do occur they typically show up in more than one area of the cat’s body. This can happen suddenly, slowly or sporadically.

Owners of cats with clinical feline bartonellosis disease may notice one or more of the following coming on all at once, showing up gradually or waxing and waning over time:

  • Enlarged lymph nodes (lymphadenopathy; extremely common in cats that are sick from bartonellosis; the veterinarian will need to rule out lymphoma/lymphosarcoma as a cause of this condition)
  • Gingivitis (inflammation, swelling, redness, pain and bleeding of the gums)
  • Ulcers (sores) in the mouth; sloughing of necrotic or dying inflammatory oral tissue
  • Stomatitis (inflammation of the mucosal lining of the mouth)
  • Diarrhea (usually chronic; may be intermittent)
  • Vomiting (usually chronic; may be intermittent)
  • Lack of appetite (inappetance; anorexia; refusal to eat normally)
  • Weight loss
  • Sinusitis (inflammation of the nasal sinus passageways)
  • Rhinitis (inflammation of the mucosal lining of the nose)
  • Difficulty breathing (dyspnea); shortness of breath; labored breathing
  • Lethargy
  • Weakness
  • Reproductive difficulties; infertility
  • Fever
  • Swollen, weepy eyes
  • Eye infections
  • Conjunctivitis (inflamed conjunctiva; eye redness)
  • Hepatitis (inflammation of the liver)
  • Heart murmurs
  • Endocarditis (uncommon in cats)
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Once symptoms of feline bartonellosis appear, they may slowly worsen or suddenly get worse within a matter of days to weeks, depending on how the cat’s immune system and organs respond to the infectious Bartonella organisms.

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Diagnosing Feline Bartonellosis Infection

Initial Evaluation

Veterinarians presented with a cat showing non-specific signs of lethargy and enlarged tender lymph nodes, possibly also with digestive and/or respiratory symptoms, will take a thorough history from the cat’s owner and conduct a complete physical examination.

The initial evaluation probably will include taking blood and urine samples and performing routine blood work and a urinalysis on those samples. While the results of these tests can be helpful to ruling in or out other causes of the cat’s symptoms, unfortunately they usually don’t show consistent abnormalities in cats that have bartonellosis.

Diagnostic Procedures

Several different advanced diagnostic tests can be used to identify the presence of Bartonella henselae or anti-Bartonella henselae antibodies in cats. These include immunofluorescent assay (IFA), polymerase chain reaction (PCR), blood cultures and Western blot, among others.

All of the blood tests, except for the blood cultures, check for the presence of antibodies to the Bartonella bacteria. If a sufficient number of antibodies are present, then a positive diagnosis usually will be made.

Currently, a Western Blot Test known as FeBart is one of the more popular diagnostic tests for bartonellosis in cats. However, even if a cat tests positive on one or more of these tests, it doesn’t necessarily confirm that Bartonella infection is the cause of the cat’s clinical problems, because so many cats are infected with Bartonella without showing any signs of being sick.

In addition, some cats that harbor Bartonella don’t produce antibodies to the bacteria; blood tests will not catch the infection in those cases. Multiple blood samples are necessary to accurately test for bartonellosis using blood cultures; even when a number of separate blood cultures are conducted, the bacteria still may be missed.

Additional tests are usually conducted to check the cat’s overall health status; these may include testing for FIV (feline immunodeficiency virus infection), FIP (feline infectious peritonitis) and FeLV (feline leukemia virus infection).

Special Notes

Because it is so difficult to confirm that Bartonella organisms are the real cause of symptoms in a particular cat, and also because so many domestic cats are infected with Bartonella, many veterinarians will start treating the cat for bartonellosis even before they have made a definitive diagnosis that the cat actually is infected.

Unfortunately, there currently is no reliable treatment protocol that successfully eliminates a cat’s infection with these organisms. The most common “treatment” is to administer oral antibiotics for several months and then reevaluate to see if the animal’s symptoms have subsided.

Treatment of Feline Bartonellosis Infection

Goals of Treating Bartonellosis in Cats

There currently is no uniform consensus among veterinarians about how to treat feline bartonellosis. It is well-accepted that the vast majority of domestic cats in the United States (and probably elsewhere world-wide) carry the Bartonella bacteria but show no signs of illness, and that these cats don’t need to be treated.

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It is also fairly well-accepted that cats with symptoms as a result of their infection probably do need to be treated to resolve their symptoms, hopefully eliminate the Bartonella infection, prevent reinfection and restore them to a comfortable, pain-free quality of life. The confusion is about what that treatment should entail.

Treatment Options for Feline Bartonellosis

Treating bartonellosis in dogs, and cat scratch fever in people, relies primarily upon antibiotic therapies, follow-up testing to ensure that the treatment successfully eliminated the infection and taking steps to prevent reinfection.

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Unfortunately, no one antibiotic protocol has yet been shown to reliably clear cats of infection with Bartonella. By looking at the treatments that have been successful in humans and sometimes in dogs, it is possible that long-term administration of azithromycin, doxycycline, tetracycline, erythromycin and/or rifampin – or some combination of those antibiotics – could be helpful in treating or at least managing feline bartonellosis.

However, the safety and effectiveness of using these drugs in cats with observable signs of bartonellosis has not been established. Moreover, prolonged use of antibiotics can lead to antibiotic resistance, which has become an increasingly serious problem in both veterinary and human medicine.

Nonetheless, many veterinarians will treat a cat showing signs of bartonellosis with azithromycin for up to 6 weeks even if a specific diagnosis hasn’t been made, in hopes of reducing or resolving its symptoms.

Once a cat has been treated for this disease, it’s important to take steps to prevent the symptoms from coming back – even though current medical therapies are unlikely to clear the Bartonella from the cat’s bloodstream.

Flea and tick control are especially important, both inside and outside the home, since the infective organisms are transmitted to cats in the feces of those parasites. Other cats in the household should be tested for the presence of Bartonella; if they test positive (as the vast majority of them will), the veterinarian may recommend that they be given a course of antibiotics to reduce the risk of re-infecting the other cat or cats that they live with.

Supportive care, including a high-quality nutritious diet and a safe, warm, quiet living environment, are also important, especially if a cat has severe symptoms.

Prognosis for Cats with Bartonellosis

The outlook for cats with noticeable symptoms of feline bartonellosis is highly variable. However, in cases where treatment delayed, or if the cat is seriously affected by the infection, the prognosis is more guarded.

Preventative measures such as flea and tick control and testing other cats in the household for Bartonella are important to managing this disease.

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