Bartonellosis

Definition

Bartonellosis is an infectious bacterial disease with an acute form (which has a sudden onset and short course) and a chronic form (which has more gradual onset and longer duration). The disease is transmitted by sandflies and occurs in western South America. Characterized by a form of red blood cell deficiency (hemolytic anemia ) and fever, the potentially fatal acute form is called Oroya fever or Carrion's disease. The chronic form is identified by painful skin lesions.

Description

The acute form of the disease gets its name from an outbreak that occurred in 1871 near La Oroya, Peru. More than 7,000 people perished. Some survivors later developed a skin disease, called verruga peruana (Peruvian warts ). These skin lesions were observed prior to the 1871 outbreak-perhaps as far back as the pre-Columbian era-but a connection to Oroya fever was unknown. In 1885, a young medical researcher, Daniel Carrion, inoculated himself with blood from a lesion to study the course of the skin disease. When he became ill with Oroya fever, the connection became apparent. Oroya fever is often called Carrion's disease in honor of his fatal experiment.

The bacteria, Bartonella bacilliformis, was isolated by Alberto Barton in 1909, but wasn't identified as the cause of the fever until 1940. The Bartonella genus includes at least 11 bacteria species, four of which cause human diseases, including cat-scratch disease and bacillary angiomatosis. However, bartonellosis refers exclusively to the disease caused by B. bacilliformis. The disease is limited to a small area of the Andes Mountains in western South America; nearly all cases have been in Peru, Colombia, and Ecuador. A large outbreak involving thousands of people occurred in 1940–41, but bartonellosis has since occurred sporadically. Control of sandflies, the only known disease carrier (vector), has been credited with managing the disease.

Causes and symptoms

Bartonellosis is transmitted by the nocturnal sandfly and arises from infection with B. bacilliformis. The sandfly, Lutzomyia verrucarum, dines on human blood and, in so doing, can inject bacteria into the bloodstream. The sandfly is found only in certain areas of the Peruvian Andes; other, as-yet-unidentified vectors are suspected in Ecuador and Colombia.

Once in the bloodstream, the bacteria latch onto red blood cells (erythrocytes), burrow into the cells, and reproduce. In the process, up to 90% of the host's erythrocytes are destroyed, causing severe hemolytic anemia. The anemia is accompanied by high fever, muscle and joint pain, delirium, and possibly coma.

Two to eight weeks after the acute phase, an infected individual develops verruga peruana. However, individuals may exhibit the characteristic lesions without ever experiencing the acute phase. Left untreated, the lesions may last months or years. These lesions resemble blood-filled blisters, up to 1.6 in (4 cm) in diameter, and appear primarily on the head and limbs. They can be painful to the touch and may bleed or ulcerate.

Diagnosis

Bartonellosis is identified by symptoms and the patient's history, such as recent travel in areas where bartonellosis occurs. Isolation of B. bacilliformis from the bloodstream or lesions can confirm the diagnosis.

Treatment

Antibiotics are the mainstay of bartonellosis treatment. The bacteria are susceptible to several antibiotics, including chloramphenicol, penicillins, and aminoglycosides. Blood transfusions may be necessary to treat the anemia caused by bartonellosis.

Prognosis

Antibiotics have dramatically decreased the fatality associated with bartonellosis. Prior to the development of antibiotics, the fever was fatal in 40% of cases. With antibiotic treatment, that rate has dropped to 8%. Fatalities can result from complications associated with severe anemia and secondary infections. Once the infection is halted, an individual can recover fully.

Prevention

Avoiding sandfly bites is the primary means of prevention. Sandfly eradication programs have been helpful in decreasing the sandfly population, and insect repellant can be effective in preventing sandfly bites.

KEY TERMS

Acute— Referring to the course of a disease, or a phase of a disease, the short-term experience of prominent symptoms.

Chronic— Referring to the course of a disease, or a phase of a disease, the long-term experience of prominent symptoms.

Erythrocytes— Red blood cells.

Hemolytic anemia— A form of erythrocyte deficiency caused by the destruction of the red blood cells.

Host— The organism that harbors or nourishes another organism (parasite). In bartonellosis, the person infected with Bartonella basilliformis.

Vector— An organism, such as insects or rodents, that can transmit disease to humans.

Resources

BOOKS

Daly, Jennifer S. "Bartonella Species." In Infectious Diseases, edited by Sherwood F. Gorbach, John S. Bartlett, and Neil R. Blacklow, 2nd ed. Philadelphia: W. B. Saunders Co., 1998.