Buruli Ulcer: Technical Information
World Health Organization (WHO) clinical case definition for Buruli ulcer divides the disease into two stages: active and inactive. The active form is characterized by non-ulcerative (papules, nodules, plaques, and edema) and ulcerative disease. The distinctive features of a Buruli ulcer include undermining edges, white cotton wool-like appearance, and thickening and darkening of the skin surrounding the lesion. The ulcers are generally painless and progressive; 85% are found on the limbs, with lower limb lesions twice as common as upper limb lesions. The inactive form is characterized by evidence of previous infection with a depressed stellate scar with or without sequelae.
The incidence of Buruli ulcer disease is not precisely defined primarily because of inadequate surveillance data and difficulty of laboratory confirmation. No cases of Buruli ulcer disease have been reported in the United States. More than 30 countries have reported cases of Buruli ulcer disease to the WHO, including countries in the Americas, Africa, the Eastern Mediterranean, Southeast Asia, and the Western Pacific. An up-to-date list of these countries is located at the WHO Buruli ulcer webpage.
Although mortality is low, morbidity is high. The healing process of ulcers, whether induced by surgery or self-healing, often results in severe contracture scaring and deformity.
Diagnosis and Confirmation
Buruli ulcer disease is diagnosed based on the WHO clinical case definition. Confirmation of disease is achieved through the use of two or more of the following laboratory tests: acid-fast bacilli (AFB) identified on microscopic smear stained by Ziehl-Neelsen technique, polymerase chain reaction (PCR), histopathology, and culture. With the exception of AFB smear, these tests are not suited for use in the remote rural areas where Buruli ulcer disease occurs most frequently. Confirmation, if acccomplished, typically occurs well after treatment has begun.
WHO recommends combination therapy with daily intramuscular streptomycin and oral rifampicin for 8 weeks for all stages of disease. Surgery to remove necrotic tissue and to correct deformities is recommended for more advanced disease. Disability prevention techniques are also recommended for all cases. Recent clinical trials have shown that early stages of disease respond well to treatment with combination anti-mycobacterial therapy, leading to high cure-rates without surgery.
Route of transmission remains unclear. One hypothesis is that M. ulcerans enters through a break in the skin, via insect bite, cut, or wound.
The disease has been associated with slow-moving, stagnant water and environmental changes including mining, deforestation, and irrigation. In West Africa, many cases are found in poor, rural farming communities. Socioeconomic status, gender, and race do not appear to be risk factors for disease. Children under the age of 15 are disproportionately affected. However, adults are also susceptible. HIV is not a known risk factor, although there are reports of HIV-infected individuals with Buruli ulcer.
Buruli ulcer disease is not a reportable disease in most affected countries. WHO encourages all endemic countries to perform surveillance.
There are reports of increasing incidence in several African countries.
The lack of knowledge surrounding the reservoir and route of transmission of M. ulcerans, diagnostic tests that can easily be performed in rural areas, and limited treatment options are major challenges to the prevention and control of Buruli ulcer disease.
Opportunities include increased surveillance for Buruli ulcer disease as a part of integrated disease surveillance, decrease in morbidity as a result of early diagnosis and treatment due the development of diagnostic tests, improved treatment and reduction of adverse sequellae of Buruli ulcer infection through use of anti-mycobacterial drug therapy, and interventions to reduce incidence of Buruli ulcer disease as a result of knowledge of reservoir and route of transmission of M. ulcerans.