Bartonella Infection in Dogs

Bartonella infections are caused by a gram-negative intracellular bacterium that take up residence in the host red blood cells. There are several subspecies of Bartonella, and bartonella infections may also be known as Cat Scratch Disease, Carrion’s Disease, and Trench Fever. Treatment with antibiotics is recommended for animals with clinical symptoms. This is a zoonotic bacteria that can affect many species, including human. It is known that Bartonella can be transmitted from cats to humans but thus far canine to human transmission is theoretically possible but unconfirmed.

Bartonella is the designation of a zoonotic family of gram-negative intracellular bacterium that can cause diseases such as Cat scratch disease, Carrion’s disease, and Trench Fever.

Many canines with a Bartonella infection show few if any clinical signs of the disease. If symptoms do develop they can be varied depending on the strain of Bartonella and the specific susceptibility of the host. The infected canine may present with any of the following symptoms:

• Collapse
• Depression
• Diarrhea 
• Enlarged spleen, lymph nodes or liver
• Fever
• Heart murmurs or arrhythmias
• Inflammation of the membranes around the heart, brain and spinal cord
• Lack of appetite or weight loss 
• Lameness
• Lethargy
• Nasal discharge and bleeding
• Seizures 
• Sudden death
• Vomiting
• Weakness

Types

There are six Bartonella species that are known to infect canines; B. henselae, B. vinsonii, B. clarridgeiae, B. elizabethae, B. woshoensis, and B. quintana. The most common reported species infecting dogs is B. henselae, which is responsible for Cat Scratch Fever. There is lower incidence of infection among cats than dogs however, dogs are more likely to develop symptoms. 

The main mode of transmission for Bartonella to and from host animals is through fleas, lice, and ticks, with ticks being the most likely vector for canines. Herding and hunting dogs seem to be at an increased risk for developing Bartonella although this may be because of their increased chance of exposure to ticks in the environment rather than a genetic predisposition. Small and toy breeds seem to have a lower incidence of infection but this may again be environmental influence rather than predisposition. Dogs with weakened immune systems have an increased chance of infection. 

Symptoms related to Bartonella will prompt your veterinarian to get the full health history of your dog, taking particular note of what common infection vectors your dog may have been exposed to in the last few weeks. Typically, a general physical examination will be given and a complete blood count and chemistry profile, as well as a urinalysis will be completed. Blood abnormalities, such as low levels of red blood cells and high levels of white blood cells, may be uncovered and elevated liver enzymes may also be present. Immunofluorescence assays performed on blood samples may confirm whether or not a dog was exposed to Bartonella, but it is not able to clarify which species of Bartonella bacterium is present. Polymerase chain reaction tests are able to distinguish between species, however if the number of bacteria present in the system is low, a false negative can occur. Placing the samples in enrichment cultures followed by the PCR testing has proven to be more diagnostically accurate than PCR testing alone.

If the infection has developed to the point that clinical symptoms are occurring those symptoms will first be addressed and supportive care will be given depending on the situation. This could include pain medications, anti-inflammatories, and IV fluids to support and balance their systems. An antibiotic, or a combination of antibiotics, are likely to be prescribed at that point. The duration of treatment by antibiotics for Bartonella infections is greatly increased compared to many other bacterial diseases and it is recommended that antibiotics are given for at least four to six weeks. Even the longer durations of aggressive antibiotic treatment may not be able to clear Bartonella from the system entirely and relapses frequently occur. Due to concerns about the development of antimicrobial resistance because of the lengthy treatment required to clear the bacteria from the host system the CDC only recommends treatment if clinical signs have developed in your pet. Bartonella disease has been known to spontaneously resolve after several weeks or even months.

The prognosis of dogs with this disease is highly variable, depending on the clinical symptoms that are presenting, as well as the severity of the infection. Ensuring that your pet completes the full measure of their antibiotic medication is the best thing you can do to protect their health with this disease. In the case of Bartonella, it is imperative that the antibiotics are given to your pet for the full four to six weeks or longer. Using an appropriate flea and tick prevention method during the months when fleas, lice, and ticks are especially prevalent will decrease your dog’s likelihood of contracting the disease.