December 28, 1997
The bug is known as Bartonella, according to a report in the current issue of The New England Journal of Medicine. One particular type, B. henselae, is carried by fleas and can cause cat scratch disease, a relatively mild illness that strikes 40,000 people in the U.S. every year. It causes swollen lymph nodes, fever and malaise after a cat bite or scratch.
A second strain, known as B. quintana, is carried by lice, and is found more often in homeless individuals and others exposed to head or body lice.
B. quintana can cause "trench fever," a relapsing fever that earned its name from an epidemic that struck thousands of soldiers during World War I.
And either strain spells disaster for people with HIV/AIDS or anyone with a compromised immune system who gets infected, the study says. In that case, the bacteria can cause bacillary angiomatosis, a Kaposi's sarcoma-like disease where lesions form in the skin, bone and brain; or bacillary peliosis, where lesions form in the liver or spleen.
Indeed, it wasn't until people with AIDS began coming down with the disorders, that doctors discovered that B. henselae was the cause of cat scratch disease.
In a new study of people with the bacillary angiomatosis or peliosis, those with bone lesions were almost always infected with the lice-associated B. quintana, and all people with liver lesions were infected with B. henselae. The study included 49 people, 45 of whom were HIV-positive.
The new study sheds light on the mysterious Bartonella organisms, which are extremely difficult to grow in the laboratory, and can cause a variety of symptoms depending on the infected person's immune status.
The researchers found that B. quintana outbreaks occurred simultaneously in Seattle and San Francisco in 1993. However in Seattle, predominantly Native American, non-HIV infected men developed blood infections, while in San Francisco, the mainly white, HIV-infected patients developed bacillary angiomatosis.
The study confirms the importance of the human body louse as a carrier of B. quintana, noted Dr. Lucy Tompkins in an editorial accompanying the study. And with the cat now the most popular pet in the U.S., more B. henselae infections might be expected.
"Even though most cases of cat scratch disease resolve spontaneously (without treatment), there are sometimes serious consequences and substantial morbidity," wrote Tompkins, of the Stanford University Medical Center in California. "Although uncommon, bacillary angiomatosis-peliosis may be life threatening if it is not recognized early and treated promptly with antibiotics."