What is Bartonella bacilliformis?

Bartonella bacilliformis, also known as South American Bartonellosis, refers to a rod-shaped bacterium belonging to the genus Alphaproteobacteria. The pathogen has so far only been found in the Andes between 3,000 and 10,000 feet altitude in western South America. Most cases of the disease have been reported in Peru, but also occur in Ecuador and Colombia. Bartonella bacilliformis is the causative agent of the so-called Carrion disease. Carrion's disease is the term used for a symptomatic Bartonella bacilliformis infection. This usually occurs in two phases and first manifests itself as acute orya fever and then develops into Peruvian warts (verruga peruana).

How is Bartonella bacilliformis transmitted?

Bartonella bacilliformis is transmitted by sandflies (more precisely by the genus Lutzomyia).

How does a Bartonella bacilliformis infection develop?

Through the bite of the sandfly infected with the Bartonella bacilliformis pathogen , the bacteria enter the human capillaries. After an incubation period of about 21 days, the bacteria progress to the red blood cells and usually trigger severe intravascular haemolytic anaemia. This phase of the disease can take on life-threatening proportions for the patient and is accompanied by high fever. In addition, there is anaemia and temporary immunosuppression. This acute phase, also called Oroya fever, lasts between two and four weeks. The second phase of the disease, the so-called verruga peruana, occurs when the bacterium penetrates further into the endothelial cells.

What are the symptoms of a Bartonella bacilliformis infection?

A Bartonella bacilliformis infection occurs rather rarely and goes through two different phases of illness:

• Oroya fever:In this first phase, fever, abdominal pain, headache as well as muscle pain and severe anaemia may occur.In up to 70 percent of all cases of the disease, complications may occur in the form of secondary infections and/or cardiopulmonary complications such as heart failure, accumulation of fluid between the pericardium and the pericardial sac (pericardial effusion), pulmonary oedema and/or cardiogenic shock.
• peruvian warts (verruga peruana):During this later stage of the disease, growths form under the skin . These can develop into red to purple vascular sores (angiomatous tumours) that tend to become sore or bleed. these angiomatous tumours are a benign rash that can cause a general feeling of discomfort.

What complications can occur due to a Bartonella bacilliformis infection?

Bartonella bacilliformis infections can lead to endocarditis, just like other Bartonella species. This is an infection of the heart valves. Since in many cases of illness the diagnosis can also be negative through a blood culture (culture-negative endocarditis), it is not always possible to diagnose endocarditis without problems.

In addition, a so-called thrombocytopenia can occur due to a Bartonella bacilliformis infection. This is the presence of a reduced number of blood platelets, the so-called thrombocytes. Neurological impairments, such as neurobartonellosis, have also been reported. However, the prognosis for neurobartonellosis, which causes impaired consciousness and paralysis, is poor.

However, a Bartonella bacilliformis infection can also lead to so-called superinfections. These can be caused by salmonella or parasites (for example Toxoplasma gondii and Pneumocystis) .

How can you protect yourself from a Bartonella bacilliformis infection?

When travelling to South American countries where the Bartonella bacilliformis pathogen is widespread, it is recommended to use insect repellents that have an EPA-registered symbol. In addition, long-sleeved shirts and long trousers should be worn to prevent sandfly bites. Since sandflies are most active at dawn and dusk in particular, outdoor activities should be avoided within this time period.

How is a Bartonella bacilliformis infection diagnosed?

A Bartonella bacilliformis infection is usually detected by a blood culture or by culturing from skin lesions. Specific antibodies and/or molecular biological pathogen detection, for example by a PCR test, are to be diagnosed by serological detection.

In addition, direct observation of the bacteria in peripheral blood smears is possible. The latter diagnostic procedure takes place during the acute phase of the infection, i.e. the Oroya fever. For this purpose, a microscopic detection of intraerythrocytic pathogens in the blood smear is examined by means of the Giemsa stain. The detection of a Bartonella bacilliformis infection through a biopsy is also generally possible by means of silver staining of the bacteria by the so-called Warthin-Starry method.

How is a Bartonella bacilliformis infection treated?

A Bartonella bacilliformis infection is treated with antibiotics. The following antiobiotics can be prescribed for this purpose. These antiobiotics are usually not only effective for a Bartonella bacilliformis infection, but also for other Bartonella pathogens:

• Aminoglycosides,
• Cephalosporins,
• Penicillins,
• Tetracyclines.

 
However, some doctors prefer quinolones. This is because infections by enterobacteria can occur with the antibiotics mentioned above .

Depending on the severity of the disease and the symptoms that occur, more than one antibiotic can be used at the same time . For treatment, it is advisable to consult a specialist for infectious diseases. Usually, only Oroya fever requires medical treatment in any case. However, the lethality of Oroya fever is just under 10 percent, even with adequate therapy. If the infection is not treated at all, the mortality rate is between 40 and 85 percent.

The Verruga peruana can be treated with the antibiotic rifampin. However, since cases of disease also occurred in which rifampin led to resistance, macrolides can be used as an alternative. It promises a similar effectiveness as rifampin.