Bartonella (Bartonella spp) is a gram-negative, single-celled bacteria that invade the red blood cells of dogs and their people causing bartonella infection or bartonellosis, an emerging zoonotic disease that manifests as cat scratch disease (CSD) aka cat scratch fever, trench fever, and carrion's disease. In humans, transmission is via infected domestic cats — natural reservoirs for the bacteria, thus "cat scratch fever"— although a scratch is not its only mode of transmission. The bacteria are carried by ectoparasites; fleas, lice, sand flies, and ticks, which are, by far, the most common vector of the disease in dogs. Dogs with impaired immune systems are most at risk for the infection.
What causes bartonella infection?
Six species of the bartonella bacteria can infect dogs: B. henselae, B. vinsonii, B. clarridgeiae, B. elizabethae, B. woshoensis, and B. quintana. B. henselae is the most commonly reported in dogs and the species responsible for cat scratch fever.
No proof exists that genetic predisposition is a factor, but herding and hunting dogs have an increased risk of exposure due to being around livestock and wild animals, as does any breed of dog that spends time in the rural outdoors. Conversely, small and toy breeds, who spend a vast majority of their time indoors, have a lower incidence of the infection.
Clinical signs and symptoms and how bartonella infection affects your dog.
Many dogs are asymptomatic with no clinical signs of infection. However, sudden death may occur in severe cases where earlier symptoms were undetected or overlooked. If your dog develops any of the following symptoms, seek veterinary care at once:
- Redness or a small, solid bump (papule) or scratch at the site of an insect bite.
- Loss of appetite.
- Weight loss.
- Irregular heartbeat (heart murmur, heart arrhythmia).
- Swollen or painful lymph nodes, especially near the site of the bite or infection.
- Muscle pain.
- Visible shivering (chills).
- Inflammation of the conjunctiva of the eye (pink eye).
- Nasal discharge.
- Bleeding from the nose.
- Seizures or altered consciousness.
How your veterinarian diagnoses a bartonella infection.
As soon as you see any clinical sign of bartonella infection, you should keep written notes of your dog's behavior, the duration of each symptom, as well as other symptom onsets until you can get to the veterinary hospital. To diagnose a bartonella infection, your veterinarian will carefully analyze the information you provide, and review your dog's complete health history, particularly in regard to ticks or other vectors of infection to which she's had exposure in the past couple of weeks. A history of flea or tick infestation will predispose your dog for a bartonella bacterial infection.
Your veterinarian will also perform a thorough physical examination and may discover the following additional symptoms of bartonella infection:
- Enlarged liver or spleen.
- Inflammation of the membranes around the heart, brain, and spinal cord.
- Inflammation of the brain.
A complete blood count, biochemistry profile, and urinalysis will then be conducted for laboratory analysis.
If bartonella infection is present, the blood work will reveal low levels of red blood cells and hemoglobin (anemia) and high levels of white blood cells. There may also be a decreased number of platelets — the cells required for blood clotting. Among the diagnostic tools used to decipher blood samples are Immunofluorescence Antibody Assay (IFA) in which fluorescent dyes indicate whether your dog was exposed to bartonella bacteria, but cannot identify the species. Blood samples are then placed in enrichment cultures to see if they test positive for growing or culturing the bacteria. Finally, a polymerase chain reaction (PCR) or DNA testing on tissue from the lesion is conducted to positively identify the species of bacteria, which results in a definitive diagnosis of bartonellosis. PCR testing without the enrichment culture is not diagnostically accurate since it may give a false negative if the number of bacteria in the system is low.
Biochemistry profiling may reveal elevated liver enzymes and a decreased concentration of the blood protein albumin.
Treating a bartonella infection.
Your dog's prognosis depends on the severity of the infection and is highly variable on the clinical symptoms. Also, in immunosuppressed dogs, the illness may be more difficult to treat. Typically, for healthy dogs, a course of antibiotics from four-to-six weeks is indicated, which in some cases may need to be longer-term. However, due to the relative newness of this disease, there is no well-established protocol of antibiotics for dogs and your veterinarian will prescribe antibiotics on an individual basis as symptoms warrant.
You'll need to closely monitor your dog after the initial round of antibiotics. Call your veterinarian at once if you see any new signs of infection or a recurrence of the initial symptoms. Unfortunately, even with treatment, the disease may not resolve due to the disease not fully described and understood as yet.
How to prevent a bartonella infection in your dog.
As with all bacterial infectious diseases caused by fleas and ticks, flea and tick medications for your dog are your first line of defense. Easy to apply topically, or given as a palatable treat every three months, for example, a variety of relatively affordable products are available through veterinary prescription and over-the-counter to keep your dog free of ticks and fleas, and give you peace of mind.
Flea control is also paramount inside the home once your dog and other pets are protected. Fleas don't live on your dog — they jump on dogs and cats for a blood meal, then go into hiding in upholstery and cracks and crevices throughout the home. Professional pest control is the best way to keep your home flea-free.
You can keep ticks off your property by keeping your lawns and foliage trimmed short, regular perimeter pesticide applications, and installing fencing to exclude wildlife who carry ticks, such as rodents and deer. Keep in mind, if a tick climbs onto your dog when she's in the yard, even if it doesn't bite her, it may be transported inside in your dog's fur, crawl onto a human member of the family, and bite. Ticks are the major vectors of pathogens and second after mosquitoes in spreading diseases to humans.
Routinely inspecting your dog to find and remove ticks after a walk through trails, wooded areas, and grasslands is a must in areas where ticks are reported.