Buruli ulcer is an infectious disease characterized by the development of painless open wounds. The disease is limited to certain areas of the world, most cases occurring in Sub-Saharan Africa and Australia. The first sign of infection is a small painless nodule or area of swelling, typically on the arms or legs. The nodule grows larger over days to weeks, eventually forming an open ulcer. Deep ulcers can cause scarring of muscles and tendons, resulting in permanent disability.
Buruli ulcer is caused by skin infection with bacteria called Mycobacterium ulcerans. The mechanism by which M. ulcerans is transmitted from the environment to humans is not known, but may involve the bite of an aquatic insect or the infection of open wounds. Once in the skin, M. ulcerans grows and releases the toxin mycolactone, which blocks the normal function of cells, resulting in tissue death and immune suppression at the site of the ulcer.
The World Health Organization (WHO) recommends treating Buruli ulcer with a combination of the antibiotics rifampicin and clarithromycin. With antibiotic administration and proper wound care, small ulcers typically heal within six months. Deep ulcers and those on sensitive body sites may require surgery to remove dead tissue or repair scarred muscles or joints. Even with proper treatment, Buruli ulcer can take months to heal. Regular cleaning and dressing of wounds aids healing and prevents secondary infections.
Signs and symptoms
The first sign of Buruli ulcer is a painless swollen bump on the arm or leg, often similar in appearance to an insect bite. Sometimes the swollen area instead appears as a patch of firm, raised skin about three centimeters across called a “plaque”; or a more widespread swelling under the skin.
Over the course of a few weeks, the original swollen area expands to form an irregularly shaped patch of raised skin. After about four weeks, the affected skin sloughs off leaving a painless ulcer.Buruli ulcers typically have “undermined edges”, the ulcer being a few centimeters wider underneath the skin than the wound itself
In some people, the ulcer may heal on its own or remain small but linger unhealed for years. In others, it continues to grow wider and sometimes deeper, with skin at the margin dying and sloughing off. Large ulcers may extend deep into underlying tissue, causing bone infection and exposing muscle, tendon, and bone to the air. When ulcers extend into muscles and tendons, parts of these tissues can be replaced by scar tissue, immobilizing the body part and resulting in permanent disability. Exposed ulcers can be infected by other bacteria, causing the wound to become red, painful, and foul smelling. Symptoms are typically limited to those caused by the wound; the disease rarely affects other parts of the body.
Buruli ulcers can appear anywhere on the body, but are typically on the limbs. Ulcers are most common on the lower limbs (roughly 62% of ulcers globally) and upper limbs (24%), but can also be found on the trunk (9%), head or neck (3%), or genitals (less than 1%).
The World Health Organization classifies Buruli ulcer into three categories depending on the severity of its symptoms. Category I describes a single small ulcer that is less than 5 centimetres (2.0 inches). Category II describes a larger ulcer, up to 15 centimetres (5.9 in), as well as plaques and broader swollen areas that have not yet opened into ulcers. Category III is for an ulcer larger than 15 centimeters, multiple ulcers, or ulcers that have spread to include particularly sensitive sites such as the eyes, bones, joints, or genitals.
As Buruli ulcer most commonly occurs in low-resource settings, treatment is often initiated by a clinician based on signs and symptoms alone. Where available, diagnosis may then be confirmed by polymerase chain reaction (PCR) to detect M. ulcerans DNA or microscopy to detect mycobacteria.
Buruli ulcer is treated through a combination of antibiotics to kill the bacteria, and wound care or surgery to support the healing of the ulcer. The most widely used antibiotic regimen is once daily oral rifampicin plus twice daily oral clarithromycin, recommended by the World Health Organization. Several other antibiotics are sometimes used in combination with rifampicin, namely ciprofloxacin, moxifloxacin, ethambutol, amikacin, azithromycin, and levofloxacin. A 2018 Cochrane review suggested that the many antibiotic combinations being used are effective treatments, but there is insufficient evidence to determine if any combination is the most effective.
Prevention of Buruli Ulcer
Buruli ulcer can be prevented by avoiding contact with aquatic environments in endemic areas, although this may not be possible for people living in these areas.The risk of acquiring it can be reduced by wearing long sleeves and pants, using insect repellent, and cleaning and covering any wounds as soon as they are noticed.There is no specific vaccine for preventing Buruli ulcer. The BCG vaccine typically given to children to protect against tuberculosis offers temporary partial protection from Buruli ulcer.