Bartonella is a modern microbiologist’s dream. This gram-negative bacterium has the ability to cause human disease in many different ways. In fact, prior to 1990, Bartonella was known to cause only two diseases. Today at least eight Bartonella species cause a wide range of symptoms, with more species being identified regularly. Many are geographic-specific, however, meaning they all don’t occur everywhere.
Bartonella infection is responsible for these human diseases and syndromes:
- Bacillary angiomatosis and peliosis hepatitis
- Carrión’s disease (includes both Oroya fever and verruga peruana)
- Cat scratch fever
- Chronic fatigue syndrome
- Endocarditis – inflammation of the heart valves
- Erythema multiforme – pink-red skin blotches
- Erythema nodosum – inflammation of fat cells under the skin
- Recurrent bacteremia — bacteria in the blood
- Uveitis – eye inflammation
- Thrombocytopenic purpura – low blood platelets
Bartonella can live in many different host animals without causing significant disease. Each host animal has one or more species of Bartonella that is particularly fond of it. For example, cats tend to carry B. henselae and B. clarridgeiae. Wild rats harbor B. doshiae B. grahamii, B. taylorii, and B. tribocorum.
Since household pets like cats, dogs, and even rabbits are natural reservoirs for Bartonella, human infection usually begins with close contact with an infected animal (hence the name. Ticks, fleas, sand flies, and lice are also presumed carriers of the disease. In addition intravenous drug users who share needles may pass the infection to each other.
Once in the human bloodstream, Bartonella uses its tail-like flagellum to seek out and burrow inside red blood cells. There it replicates, releasing a molecule that helps produce more red blood cells. While B. quintana and B. henselae naturally exist in cat red blood cells, in humans these bacteria prefer to invade the lining of blood vessels, called endothelial cells.
The effects of these bacteria depend on the status of the patient’s immune system. An infected person with a healthy immune system may have minor symptoms that disappear in a short time. But people with compromised immune systems may have high numbers of bacteria that persist in the blood and tissues and cause symptoms for much longer. This is often the case with people who have Lyme Disease and other Lyme co-infections.
Symptoms of Infection
The symptoms of bartonellosis depend on the particular species of bacteria and the immune status of the patient. The most common diseases are:
Cat scratch disease – Also known as cat scratch disease. Usually begins with an enlarged lymph node near the scratch that may extend to many other lymph nodes later in the illness. A skin bump typically develops that is filled with fluid or pus. Other characteristic symptoms include fever, fatigue, and malaise.
Trench fever – The first symptom is fever, soon accompanied by alternating chills and copious sweats. Trench fever is also associated with achy muscles, headache, and eye inflammation with pain. In immunocompromised individuals particularly, the persistent presence of bacteria in the blood indicates that the heart valves have been infected, a condition known as endocarditis.
Carrión’s disease – Oroya fever causes fever, chills, sweating, aches, and shortness of breath along with neurological problems such as headache, mental status changes, and even seizures. Verruga peruana is a skin disease that occurs in people who had Oroya fever but were not effectively treated. Skin lesions in verruga peruana contain many blood vessels so they bleed easily and tend to leave scars if they break. Originally identified in Peru, Ecuador, and Colombia, this disease is now showing up elsewhere.
Diagnosis of bartonellosis begins with a detailed history and physical examination. The physician must first suspect that a Bartonella bacterial infection is the cause. Diagnostic workup includes blood tests and perhaps a CT scan. A positive blood test means the patient is infected. However, a negative test doesn’t mean a person isn’t infected. If a doctor still suspects Bartonella, the blood can be stained and viewed under a microscope for the presence of actual bacteria. CT scans may show swollen lymph nodes or even granulomas in body organs. Tissue or skin biopsies may also show the infection.
In patients with intact immune systems, the infection usually lasts a few weeks until the body clears it. In fact, some doctors believe it’s not necessary to treat patients with mild disease. Most patients do receive treatment, however, to prevent complications. Fairly aggressive antibiotic treatment is needed for immunocompromised patients, such as those with HIV/AIDS, and for those with endocarditis.
A number of antibiotics are suitable for treating Bartonella. Some species are more sensitive to some antibiotics than others. Azithromycin, doxycycline, ciprofloxacin, Bactrim (trimethoprim and sulfamethoxazole), and gentamicin are most commonly used.
If the heart valves are damaged from endocarditis, the valves may need to be repaired or replaced surgically. Large granulomas may also need to be treated surgically if they cause pain or affect organ function.
Usually bartonellosis is a self-limited disease. The infection tends to go away on its own—even faster when antibiotics are given. Bacteria may return in the blood from time to time, though, for reasons that are not yet clearly understood.
In rare instances, Bartonella spreads to the liver, causing granulomas (a ball of immune cells). The illness may also cause Parinaud oculoglandular syndrome, similar to “pink eye.” About 3% of infected individuals develop encephalopathy (brain dysfunction), which causes a number of neurological problems. If neuroretinitis occurs, patients may suddenly lose their vision; however this usually resolves (at least in people with intact immune systems). The bones may also be affected (osteomyelitis).
For patients with Lyme Disease, the picture is usually complicated by multiple infections, which makes treatment and prognosis more difficult.
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