Ask the doctors 8/8

Dear Doctor: I heard about a place in Australia where there’s suddenly a whole bunch of cases of flesh-eating bacteria. What kind of bacteria is this? Can it occur in the United States?

Dear Reader: You’re referring to an outbreak of a tropical disease called Buruli ulcer, which has been centered along a portion of Australia’s southern coast. The disease is caused by a pathogen known as a mycobacterium. That’s the same genus of microorganisms that cause tuberculosis and leprosy, among other illnesses.

For fellow science nerds, the organism that causes Buruli ulcer is the mycobacterium ulcerans. It’s named for Buruli county in Uganda, which is where scientists first identified the collection of symptoms as a specific condition. The organisms that cause the disease release a unique toxin known as mycolactone. It not only damages the tissues it inhabits, but also is able to prevent the immune system from mounting a defense.

Buruli ulcer usually begins quietly, often with a small and painless raised lesion, a patch of thickened skin or an area of swelling just below the skin. Within the next four or five weeks, the organisms create a wound that, if left untreated, will grow in size. Although damage is usually limited to the skin and the tissues just below the skin, in some cases the bone can be affected. This can lead to deformities. About half of cases of Buruli ulcer are found on the lower limbs, about one-third appear on the arms and the rest develop in other regions of the body. How the disease is transmitted is not yet known.

Even though health care providers familiar with the disease can often make a diagnosis from viewing the damage caused by the microorganism, it’s important to conduct a thorough examination to rule out other potential causes. This includes taking the person’s medical history and learning about all recent travel. Tissues from suspected sores and lesions are gathered, either with a swab or a biopsy, and are then tested in a laboratory. In its early stages, the condition is occasionally mistaken for boils, fatty tumors known as lipomas or a fungal infection. Several of the people in Australia who became infected with the mycobacterium initially thought the resulting nodules were insect bites. The disease is treated with a combination of several different antibiotics and wound care.

Buruli ulcer has been identified in 33 different countries, but historically has been most common in certain tropical regions of west and central Africa. Outside of Africa, the largest number of cases each year are reported in Australia. The number of cases worldwide fluctuates. Reports have ranged from a height of 5,000 cases per year to a low of about 1,900 cases, in 2016. Now, as with the outbreak in Australia, cases appear to be on the rise again. As for whether or not the disease can become a problem in the U.S., it’s unlikely. Only a few cases have been reported here over the years, and each was linked to travel in a region where the organism that causes the disease is regularly found.

Send your questions to askthedoctors@mednet.ucla.edu.