What is the issue?
Mycobacterium ulcerans (M. ulcerans) is a bacterial infection which causes slowly developing painless nodules or papules which can become destructive skin ulcers. These are variously known as the Buruli ulcer or Bairnsdale ulcer.
M. ulcerans infection was first diagnosed in the Bairnsdale area in the 1930s. Since then a growing number of cases have been reported in the Bellarine Peninsula and since 2012, the Mornington Peninsula – particularly in Rye and surrounding townships of Sorrento and Blairgowrie. Recently a small and growing number of cases have been seen in residents of other bayside areas. In 2015 there were 106 cases notified in Victoria, with 46 cases notified so far this year compared with 40 cases for the same time last year.
When recognised early, testing is straightforward and treatment can significantly reduce skin loss and tissue damage.
Who is at risk?
Everyone is susceptible to infection. Although the source of the infection is unknown, this environmental organism appears to be associated swampy or stagnant water, and/or coastal vegetation. It is possible that infection may occur weeks to months after direct exposure of broken skin to the environment or through the bite of a mosquito or
other insect, which was in turn in contact with an animal reservoir. Individuals who visit endemic areas are
considered at greatest risk. M. ulcerans is not known to be readily transmitted from one person to another. People
aged 60 years and over have a higher rate of notification with M. ulcerans in Victoria.
Symptoms and transmission
Although the incubation period has not been clearly defined, it is thought to vary from weeks to several months,
with a median of 4-5 months. There is a peak in diagnoses in Victoria between June and November each year,
however cases are diagnosed year round.
The first sign of M. ulcerans infection is usually a painless, non-tender nodule or papule. It is often mistaken for an
insect or spider bite and is sometimes itchy. The lesion may occur anywhere on the body but it is most common on
exposed areas of the limbs. In one or two months the lesion may become fluctuant and ulcerate, forming a
characteristic ulcer with undermined edges.
Ordinarily there is no regional lymphadenopathy, fever or systemic manifestations, because the bacterium
produces a unique toxin known as mycolactone that inhibits the immune response whilst leading to tissue damage.
If left untreated, extensive ulceration can occur, requiring surgical management. Occasionally the disease may
present as a firm, painless elevated plaque or an entire limb or area may be indurated by oedema without an ulcer.
Transmission pathways are net well understood. Both mosquitoes and possums have been implicated in the
transmission pathway. Most cases report some form of skin trauma, including insect bites, prior to development of
Prevention and treatment
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. Although not confirmed, it is possible that M. ulcerans may be transmitted by mosquito bites, therefore
the use of insect repellent when outdoors during warmer months is recommended.
Dry swabs (or pre-moistened with sterile saline) from beneath the undermined edges of the lesion or a biopsy
should be sent for staining for acid-fast bacilli (AFBs), PCR and culture. Although the same swab or biopsy may be
used for all three procedures if performed in the same laboratory, it is recommended to send two separate swabs
or a swab and a biopsy, especially if a specimen is being referred to the Victorian Infectious Diseases Reference
Laboratory (VIDRL) for PCR and culture. It is essential that there is visible clinical material on the swab. Please
state 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.
A biopsy of suspicious lesions which have not ulcerated can be sent for histology. The suspected diagnosis should
be mentioned and a request made for AFB staining, specific PCR and mycobacterial culture. The PCR test is only
performed at VIDRL and can confirm the diagnosis in a few days. Culture usually takes 8–12 weeks.
Under the Public Health and Wellbeing Regulations 2009, M. ulcerans infection is a Group B disease and must be
notified in writing by medical practitioners and persons in charge of laboratories within five days of diagnosis.
Referral for treatment to doctors experienced in the management of this condition is recommended. The current
mainstay of treatment is rifampicin-containing combination oral antibiotic therapy. Surgery may be used in
combination with antibiotic therapy where indicated.
Chief Health Officer Advisory: Changing pattern of Mycobacterium ulcerans infection in Victoria 3
Buruli ulcer in Australia
The Blue Book – Guidelines for the control of infectious diseases
Better Health Channel – Bairnsdale Ulcer
For further information please contact the Communicable Disease Prevention and Control section at the Department of Health on 1300 651 160.