Buruli ulcer (Mycobacterium ulcerans infection)

Notification requirement for Buruli ulcer

Buruli ulcer is a ‘routine’ notifiable condition and must be notified by medical practitioners and pathology services in writing within five days of diagnosis.

This is a Victorian statutory requirement.

Primary school and children’s services centres exclusion for Buruli ulcer

School exclusion is not required.

Infectious agent of Buruli ulcer

Buruli ulcer is a skin infection caused by the bacterium Mycobacterium ulcerans (M. ulcerans). 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 has been known as Bairnsdale or Daintree ulcer.

Identification of Buruli ulcer

Clinical features

The first sign of Buruli ulcer is usually a painless, non-tender nodule or papule. It is often thought to be an insect bite and is sometimes itchy. The lesion may occur anywhere on the body but is most common on exposed areas of the limbs. Over weeks to months, the lesion typically ulcerates, forming a characteristic ulcer with undermined edges. If it is left untreated, extensive ulceration and tissue loss can occur.

Some people initially develop a painful lump, limb swelling (oedema) or cellulitis without an ulcer. Occasionally people develop severe pain and fever.

In patients with a slow healing lesion or cellulitis that does not respond as expected to usual antibiotics, the diagnosis of Buruli ulcer should be considered, especially in those with reported exposure to an endemic area. Early recognition, diagnosis and treatment are important to minimise tissue damage.

Diagnosis

If an ulcer is present or if a scabbed lesion can be deroofed, two dry swabs (or pre-moistened with sterile saline) from beneath the undermined edges of the lesion should be sent for staining for acid-fast bacilli (AFB), M. ulcerans PCR and culture. It is essential that there is visible clinical material on the swab. The key to accurate diagnosis is that M. ulcerans is found in the subcutaneous fat layer. This can only be accessed with a swab if an ulcer has already formed.

If an eschar cannot be deroofed or in the event of atypical presentation with plaque, oedema and/or cellulitis, a swab will likely return a false negative and will not be useful. In these cases, fine needle aspirate (FNA), a punch biopsy, or skin biopsy will be required for diagnosis. Repeat testing or punch biopsy should be undertaken if initial PCR is negative and clinicians have a high clinical suspicion for M. ulcerans. The biopsy should be sent for histology, and fresh tissue should be sent for AFB staining, M. ulcerans PCR and mycobacterial culture.

Please specify on the specimen request form that Buruli ulcer or M. ulcerans is suspected so that one swab is reserved for PCR testing by the public health reference laboratory for Victoria, the Victorian Infectious Diseases Reference Laboratory (VIDRL) and not split for other laboratory testing such as culture.

The PCR test is performed at VIDRL or at Melbourne Pathology. This test can give rapid confirmation of the diagnosis within a few days and is free for patients (a handling fee may still apply for private pathology collection services). General practitioners should include their patient’s Medicare details so that the test can be bulk billed. Public hospitals can also test for Buruli ulcer free of charge. Culture of the organism usually takes 8–12 weeks.

Incubation period of Buruli ulcer

The average incubation period is estimated to be between 4 and 5 months (Range 1 to 9 months).

Public health significance and occurrence of Buruli ulcer

Buruli ulcer has been reported in 33 countries worldwide, and the main burden of disease occurs in sub-Saharan 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, Northern Territory and in parts of Victoria. In Victoria, the disease is being identified in an increasing number of geographic areas, both coastal and non-coastal. These locations include:

• Mornington peninsula region
• Bellarine peninsula region
• Westernport region
• Frankston/Langwarrin region
• South Eastern Bayside suburbs
• East Gippsland
• Phillip Island (particularly Cowes), although much less common now
• Aireys Inlet and the Surf Coast
• Several suburbs of Greater Geelong, in particular Belmont, Highton, Newtown, Wandana Heights, Grovedale and Marshall
• Inner Melbourne suburbs of Essendon, Moonee Ponds, Brunswick West, Pascoe Vale South and Strathmore

Reservoir for Buruli ulcer

The exact reservoir remains unclear. In Victoria, there is now evidence that possums (mainly ringtail but less commonly brushtail species) are a major reservoir and amplifying host. The bacteria has been isolated from possum excrement in areas with human cases and ringtail possums in these areas frequently have M. ulcerans lesions themselves.

Mode of transmission of Buruli ulcer

The exact method of transmission of Buruli ulcer is incompletely understood. Buruli ulcer is an infection acquired from the environment. There is increasing evidence from local research that mosquitoes and possums play a key role in transmission in Victoria based on data from laboratory, epidemiological and field research. However is not yet known exactly how humans become infected with the bacteria.

The one established risk factor for contracting the disease is exposure to a Buruli-endemic area. The highest risk for infection is during the warmer months, but transmission can occur at any time of the year.

Period of communicability of Buruli ulcer

Buruli ulcer is not known to be transmissible from one person to another.

Susceptibility and resistance to Buruli ulcer

Everyone is susceptible to infection. Disease can occur at any age, but Buruli ulcer notifications are highest in people aged 60 years and above in Victoria. The risk of contracting Buruli ulcer, however, is still considered low.

Control measures for Buruli ulcer

Preventive measures include:

• Reduce mosquito breeding sites around houses and other accommodation by reducing areas where water can pool (including pot plant containers, buckets, open tins or cans, discarded tyres, and other untreated, freshwater pools).
• Mosquito proof your home by securing insect screens on accommodation.
• Avoid mosquito bites by:
  • Using personal insect repellents containing diethyltoluamide (DEET) or picaridin
  • Covering up by wearing long, loose-fitting, light-coloured clothing
  • Avoiding mosquito-prone areas and vector biting times, especially at dusk and dawn.
• When gardening, working or spending time outdoors,
  • Wear gardening gloves, long sleeved shirts and trousers
  • Wear insect repellent on any exposed skin
  • Protect cuts and abrasions with a dressing
  • Promptly wash any new scratches or cuts you receive with soap and apply a topical antiseptic and dressing.
• Exposed skin contaminated by soil or water should be washed following outdoor activities.

Control of case

It is recommended that ulcers be kept covered and thorough handwashing be performed following dressing changes. Soiled dressings and other materials can be disposed of in regular clinical waste.

Referral for treatment to infectious diseases doctors experienced in the management of this condition is strongly recommended, without delay.

The mainstay of Buruli ulcer treatment is oral antibiotic therapy for approximately 8 weeks which is recommended for most lesions unless contraindicated, not tolerated or declined by the patient. Treatment may be prolonged if the lesion involves deeper structures (e.g. bone or joint) or in the case of severe paradoxical reactions, and should be guided by an infectious diseases physician. The Therapeutic Guidelines should be consulted.

Surgery may be required in some patients, in addition to antibiotic treatment, to remove necrotic tissue or repair large defects. Primary excision alone without antibiotics may sometimes be curative but the risk of relapse is significantly reduced if antibiotics are also prescribed. Healing of ulcers is usually slow with full healing often taking many months and up to 12 months after starting antibiotic therapy. Occasionally, small lesions have been reported to heal spontaneously.

Control of contacts

Not applicable as person-to-person transmission has not been demonstrated for M. ulcerans.

However, household members of people with Buruli ulcer should self-monitor for any non-healing skin lesions and seek early medical assessment as they may have been exposed to the same environmental source.

Control of environment

Refer to the preventive measures listed above in relation to reducing mosquito breeding sites around homes.

Outbreak measures for Buruli ulcer

If surveillance or follow up of cases indicate intense clustering of cases or a suspected new area of local transmission, these are investigated and the appropriate level of public health response considered.