Notification requirement for Mycobacterium ulcerans infection
Mycobacterium ulcerans infection is a ‘routine’ notifiable condition and must be notified by medical practitioners and pathology services in writing within 5 days of diagnosis.
This is a Victorian statutory requirement.
Primary school and children’s services centres exclusion for Mycobacterium ulcerans infection
School exclusion is not required.
Infectious agent of Mycobacterium ulcerans infection
M. ulcerans is a member of the Mycobacteriaceae family of acid-fast bacilli. The mycobacteria that cause tuberculosis and leprosy and many other environmental mycobacteria belong to this family. M. ulcerans typically causes skin ulcers, otherwise known as Buruli ulcer. Previously, it was known as Bairnsdale or Daintree ulcer.
Identification of Mycobacterium ulcerans infection
The first sign of M. ulcerans is usually a painless, non-tender nodule or papule. It is often thought to be an insect bite. The lesion may occur anywhere on the body but is most common on exposed areas of the limbs, commonly overlying joints. Some patients complain that the lesion is itchy. In 1–2 months, the nodule may become fluctuant and erode, forming a characteristic ulcer with undermined edges. Ordinarily, there is no regional lymphadenopathy, fever or systemic manifestation associated with the disease. If it is left untreated, extensive ulceration and tissue loss can occur.
Occasionally, the disease may present as a firm, painless elevated plaque with irregular edges, or an entire limb or area may be indurated by oedema without an ulcer being present. The oedematous form may be associated with fever.
Swabs from beneath the undermined edges of the lesion or a biopsy should be sent for staining for acid-fast bacilli (AFBs). Two other swabs should be taken: a dry swab for a polymerase chain reaction (PCR) test and another for culture should be placed in transport medium. Bacterial culture or a specific PCR should be performed to confirm the diagnosis. It should be stated on the request form that M. ulcerans is suspected.
A positive smear for AFBs makes the diagnosis likely. Culture or PCR is required for confirmation. A negative smear does not exclude the diagnosis.
The PCR test is performed at the Victorian Infectious Diseases Reference Laboratory. This test can give rapid confirmation of the diagnosis within a few days. Culture of the organism usually takes 8–12 weeks.
A biopsy of suspicious lesions that have not ulcerated can be sent for histology. The suspected diagnosis should be mentioned and a request made for AFB staining, specific PCR and bacterial culture. Biopsy specimens usually show extensive necrosis, especially of fat. Granulomatous inflammation is usually present in more chronic lesions. AFBs are frequently seen in large numbers.
Incubation period of Mycobacterium ulcerans
The incubation period has not been clearly defined but is thought to be quite long (weeks to a couple of months).
Public health significance and occurrence of Mycobacterium ulcerans infection
After tuberculosis and leprosy, M. ulcerans is the most common mycobacterial disease, and incidence is on the rise. The disease exists or is suspected in 31 countries. The majority of the cases occur in foci in West and Central Africa, where large, severe, disabling ulcers may result in severe contractures or death from extensive skin loss.
In Australia, the disease exists in Far North Queensland around the Mossman area and in parts of coastal Victoria, including East Gippsland (where it was first described in Bairnsdale and so named), Cowes on Phillip Island, the Mornington Peninsula and the Bellarine Peninsula, where it is now firmly entrenched. Although M. ulcerans is not a common cause of ulcers in Australia, it is important that it be considered in patients from endemic areas, as early diagnosis and treatment are important to minimise tissue damage.
Reservoir for Mycobacterium ulcerans
The organism appears to be associated with swampy or stagnant water. The exact reservoir remains unclear. An association with mosquito bites has been proposed.
Mode of transmission of Mycobacterium ulcerans
The exact method of transmission of M. ulcerans infection is unclear. Exposure to contaminated water, soil or vegetation in areas where the disease is known to occur is thought to be required. The bacteria may enter through a break in the skin. Exposure to aerosols of contaminated water has been hypothesised to be a method of acquisition. Recently, some insects that live in water have been shown to contain the bacteria, and they may play a role in vector transmission. The one established risk factor for contracting the disease is to live in a Buruli-endemic area.
Period of communicability of Mycobacterium ulcerans infection
M. ulcerans infection is not known to be transmissible from one person to another..
Susceptibility and resistance to Mycobacterium ulcerans infection
Everyone is susceptible to infection.
Control measures for Mycobacterium ulcerans infection
Early recognition and diagnosis are important to minimise the disabling and disfiguring effects of this disease. Referral for treatment by doctors experienced in the management of this condition is recommended. Simple precautionary measures such as wearing appropriate protective clothing when gardening and undertaking recreational activities in identified risk areas may assist in preventing infection. Cuts and abrasions should be cleaned promptly, and exposed skin contaminated by suspect soil or water should be washed following outdoor activities.
BCG vaccination has no role.
Control of case
It is recommended that ulcers be kept covered and thorough handwashing be performed following dressing changes. Safe disposal of infected material should also occur.
Until recently, treatment has been with wide surgical excision of affected skin and surrounding normal tissue; antibiotics were avoided due to previous unsuccessful trials. A number of antibiotics have now been found to be active against the organism in vitro. They include clarithromycin, rifampicin, azithromycin and amikacin. Favourable in vivo studies have led to combinations of those antibiotics being used as first-line therapy in early and limited disease. Surgery is now reserved for refractory or severe cases with adequate (but not excessive) clearance of the undermined edges of the ulcer. Primary closure is possible with small lesions, but skin grafting of the area may be required for larger ulcers.
Heat may be used as an adjunctive treatment. Continuous local heating promotes healing but care must be taken to prevent burning. The organism grows at 32 °C, and heat up to 40 °C has been used with some effect.
Occasionally, small lesions have been reported to heal spontaneously.
Control of contacts
Control of environment
Outbreak measures for Mycobacterium ulcerans infection
Clusters of cases are investigated, looking for a common source for which an intervention, including health or public alerts, may be feasible and advisable.