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Of these zoonotic species, several may be transmitted to humans by companion animals (dogs and cats), typically through a bite or scratch. Human diseases that have been identified to be caused by one of the Bartonella spp bacteria include cat scratch disease ( Bartonella henselae ), Carrion’s disease ( Bartonella bacilliformis ), and trench fever ( Bartonella quintana ).

Bartonella spp have also been associated with diseases of the skin (bacillary angiomatosis), liver (peliosis hepatis), heart (endocarditis), eyes (neuroretinis), blood (bacteremia), and brain (encephalitis).

Bartonella infection does not always cause overt illness.

A number of studies have detected clinically healthy people that have tested positive (seropositive) for Bartonella but have no known history of typical Bartonella symptoms.

Those who do become ill usually develop mild disease that tends to end without treatment (self-limiting).

However, Bartonella can cause severe infection in some people.

Immunocompromised patients, such as those undergoing immunosuppressive treatments for cancer, organ transplant patients, and people with HIV/AIDS, are more likely to develop severe, life-threatening disease.

Alberto Barton discovered the organism that became named Bartonella bacilliformis . Diseases caused by Bartonella spp occur all over the United States and in all major regions of the world, with higher prevalence occurring in areas that harbor insect carriers (arthropod vectors).

Diseases in humans that have been identified to be caused by one of the Bartonella spp include cat scratch disease, Carrion’s disease, and trench fever.

Cat scratch disease (CSD): CSD, caused by Bartonella henselae ( B.

henselae ), is an infectious disease with symptoms that can vary from mild to severe.

Although in most patients the disease resolves spontaneously within 2-4 months without treatment, in people with severe cases and/or patients with a suppressed immune system, such as HIV/AIDS, antibiotic treatment is recommended. The major symptoms of cat scratch disease may not appear for several days or weeks after exposure. A red spot (macule) may appear on the skin at the site of infection, and may become raised (papule) 3 to 10 days after exposure.

It may become filled with fluid (vesicle), then crust over and heal with a scar similar to those left by chicken pox.

The papule persists for 1 to 3 weeks, but may go unnoticed or be attributed to an injury. Within 1-3 weeks, swelling of lymph nodes (lymphadenopathy) develops in a single node or group of regional nodes near the site of the bite or scratch. Swollen lymph nodes frequently occur under arms, on the neck, or in the groin regions.

These nodes usually become very tender and the surface of the skin may appear red and feel hot to the touch.

Pus may develop in the involved lymph nodes (suppuration) and become fluctuant. Lymphadenopathy remains regional and typically resolves within 2-4 months but may last up to 6-12 months.

Other symptoms of cat-scratch disease may include achiness and overall discomfort (malaise), fatigue, headache, and in some patients, fever. Less common symptoms include loss of appetite, sore throat, and weight loss. In some cases chills, backache, and/or abdominal pain have been reported.

Rare complications of Bartonella henselae infection more typically occur in people with immunocompromised conditions, such as those undergoing immunosuppressive treatments for cancer, organ transplant patients, and people with HIV/AIDS, although they are being increasingly reported in immunocompetent people, too. Increasingly these atypical manifestations have been reported in patients without the typical symptoms of CSD.

Children in particular appear to develop inflammation in the liver (granulomatous hepatitis) or spleen (splenitis) and bone infection (osteomyelitis). Other atypical manifestations of CSD include bacillary angiomatosis, encephalopathy (inflammation of the brain), neuroretinitis (inflammation of the retina and optic nerve of the eye),, Parinaud’s oculolandular syndrome (conjunctivitis), and endocarditis (infection of the heart valve),Bacillary angiomatosis, caused by B.

henselae , is a skin disorder that is characterized by reddish, elevated lesions that are often surrounded by a scaly ring and bleed easily. The condition may spread to produce a more widespread systemic disorder that can involve bone, liver, spleen, lymph nodes, the gastrointestinal and respiratory tracts, and bone marrow.

Bacillary angiomatosis has occasionally been reported in immunocompetent patients.

Bacillary peliosis, a form of peliosis hepatis, is a vascular condition caused by B.

It is characterized by presence of blood-filled cavities in the liver.

Parinaud’s oculoglandular syndrome, which affects the eye, presents in approximately 5% of patients with CSD. Symptoms include red, irritated, and painful eye (similar to conjunctivitis or “pink eye”), fever, general ill-feeling, and swelling of nearby lymph glands, often in front of the ear (preauricular lymphadenopathy). Neurologic complications occur in approximately 2% of infected patients, with encephalopathy being the most common presentation. Symptoms generally occur 2 to 3 weeks after the onset of lymphadenopathy, although some patients have been known to present with neurological symptoms without a CSD history.

Greater than 90% of these patients have complete, spontaneous recovery with no negative after-effects.

Other rare symptoms of bartonellosis may include swelling of the largest salivary gland (parotid gland), cardiac manifestation with inflammation of the lining of the heart and its valves (endocarditis), renal inflammation (glomerulonephritis), granulomatous inflammation of the liver (hepatitis), splenitis, and/or abscesses of the spleen.

In very rare cases, bartonellosis has been associated with atypical pneumonia, an inflammatory reaction to infection characterized by bumps on the lower legs (erythema nodosum), and/or a skin discoloration associated with a decreased blood platelet count (thrombocytopenia purpura). Carrion’s disease: Carrion’s disease, caused by Bartonella bacilliformi s ( B.

bacilliformis ), is a rare infectious disease that was originally thought to occur only in the Peruvian Andes. Other South American countries have more recently been included. New cases of the disease have been found in individuals who have traveled to other parts of the world.

In most affected individuals, Carrion’s disease is characterized by two well-defined stages: a sudden, acute phase known as Oroya fever and a chronic, benign skin (cutaneous) eruption consisting of raised, reddish-purple nodules known as

verruga

Oroya fever may be characterized by a sudden onset of high fever, profuse sweating, severe headache, chills, weakness, and paleness of the skin.

In addition, in many affected individuals, mental changes may develop, including confusion and disorientation or a coma.

Such abnormalities occur in association with rapidly developing reduced levels of red blood cells (erythrocytes) due to bacterial invasion and destruction of these cells (hemolytic anemia).

The first phase of the disease is very similar to malaria. Additional associated findings may include abdominal pain, severe muscle aches (myalgia) and arthralgia, lymphadenopathy, inflammation of the brain and its protective membranes (meningoencephalitis), seizures, and/or other abnormalities.

In addition, some affected individuals may develop chest pain due to insufficient oxygen supply to heart muscle (angina), thrombocytopenia, labored breathing (dyspnea), impaired digestive and liver function, and/or other abnormalities. Such findings are thought to result from severe hemolytic anemia and the abnormal formation of blood clots within small blood vessels (microvascular thrombosis), leading to an insufficient supply of oxygen to tissues (ischemia), impaired functioning of organs, and potentially life-threatening complications.

In addition, in some patients, the acute stage of Carrion’s disease may be complicated by and increased in severity due to the presence of other infections, such as salmonellosis or malaria (i.e., intercurrent infections). For further information on malaria, please choose “malaria” as your search term in the Rare Disease Database.) In its mildest form, Carrion’s disease may not be noted until the development of characteristic skin lesions (verruga peruana).

In such instances, it may have a gradual onset and initially be characterized by a fever that may be present for less than a week and be unrecognized as a manifestation of Carrion’s disease.

In those affected by Oroya fever, the period of recovery is typically associated with gradually reduced fever and disappearance of the bacterium as seen on microscopic examination of small blood specimens.

However, some individuals remain persistently infected for years; blood smear examination, although the historical standard diagnostic testin Peru, is a very insensitive test. Furthermore, some affected individuals may temporarily have an increased susceptibility to certain, subsequent infections, such as with Salmonella bacteria (salmonellosis).

Infection with certain strains of Salmonella bacteria may cause high fever, abdominal pain, bloody diarrhea, nausea, vomiting, rash, and/or other symptoms and findings. In addition, in some cases, without appropriate antibacterial therapy, B. bacilliformis may remain present in the blood (bacteremia) for months to years without apparent symptoms (asymptomatic), potentially resulting in continued spread of the disease to others (i.e., as a “reservoir” or an ongoing source of infectious disease).