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Overview
Melioidosis is caused by the environmental bacterium Burkholderia pseudomallei (B. pseudomallei). Infection typically occurs through direct contact with contaminated soil or water via subcutaneous inoculation, ingestion, or inhalation. Melioidosis may present as a localised infection, pneumonia, bacteraemia, or disseminated infection.
Disease epidemiology
The disease is endemic to Southeast Asia and Northern Australia where B. pseudomallei is found in soil and water. Cases have been reported in Singapore and other parts of the world, including Asia, the Pacific, the Americas, the Caribbean, and the Middle East.
Pathogen(s)
Burkholderia pseudomallei.
Transmission
Transmission of melioidosis occurs through:
Direct inoculation of contaminated soil or water through small cuts or abrasions
Inhalation of contaminated soil dust
Ingestion or aspiration of contaminated water
Incubation period: Typically 9 days; range is 1 to 21 days. May remain latent for months to years before symptoms develop.
Infectious period: Not considered contagious; person-to-person spread is extremely rare.
Clinical features
The presentation of Melioidosis is variable and can mimic many other conditions (e.g. tuberculosis). Melioidosis infections can be subclinical. Common presentations include:
Pneumonia
Localised skin ulcers or abscesses
Osteomyelitis
Meningoencephalitis
It should also be considered as a differential in a patient presenting with visceral abscesses (e.g. liver, spleen, kidney, or prostate). Patients are often bacteraemic and can develop a fulminant infection with septic shock. The mortality rate is high in these cases. Some patients may experience relapses even after appropriate antibiotic therapy has been administered for the initial infection.
Risk factors
Risk factors include:
Exposure to soil or surface water in occupational (e.g. military, farming, or construction work), or recreational (e.g. adventure travellers) activities
Comorbidities such as diabetes mellitus, chronic renal disease, or chronic lung disease
Diagnosis
Melioidosis is diagnosed when a laboratory test detects B. pseudomallei in samples from blood, respiratory specimens such as sputum, throat swabs, wound specimens, urine, or fluid obtained from infected site, via PCR or bacterial culture.
Serology (e.g. indirect haemagglutination test) is not a reliable method of diagnosis.
Treatment and management
Patients generally require long courses of antibiotics.
Abscesses should be drained when possible.
Precaution, prevention, and control
Standard precautions apply in healthcare settings.
Patients with known risk factors should cover all cuts and minimise contact with soil and surface water. Protective clothing (gloves and boots) is recommended for those with occupational exposure to soil and water. In endemic areas, skin wounds that have become contaminated with soil or surface water should be immediately and thoroughly cleaned.
There is no available vaccine for Melioidosis.
Notification
Melioidosis is a notifiable disease under the Infectious Diseases Act.
Who should notify:
Laboratories
When to notify:
Laboratories – upon laboratory confirmation
How to notify:
Please refer to the Infectious Disease Notification for more information.
Notification timeline:
Within 72 hours
Resources
Please refer to the Weekly Infectious Diseases Bulletin for the numbers of confirmed Melioidosis cases in Singapore.
For more information on Melioidosis, please refer to the Centers for Disease Control and Prevention website.
For general travel advisory, please refer to Health Advice for Travellers.