Melioidosis: Uncovering a Neglected Tropical Disease

By Stephen Taylor

The ASM Biothreats Melioidosis Panel on Tuesday, February 7th, shed light on a largely ignored infectious disease that runs rampant in developing Southeast Asian countries. The speakers, Dr. Direk Limmathurotsakul, the Head of Microbiology at Mahidol-Oxford Tropic Medicine Research Unit, and Dr. Frances Daily, of Diagnostic Microbiology Development Programme, brought a wealth of first-hand knowledge and experience diagnosing and treating this disease in Thailand and Cambodia.

Melioidosis is an infection caused by Burkholderia pseudomallei, a bacterium often found in soil and water.  It is known to cause fever, arthritis, and abscesses of vital organs.  Once inoculated with bacteria, carriers typically experience an incubation period between 1 and 21 days before melioidosis symptoms appear.  Humans acquire B. pseudomallei by inhaling contaminated dust, ingesting contaminated water, or coming into contact with contaminated soil.

In the United States, B. pseudomallei is classified by Health and Human Services and the U.S. Department of Agriculture as a Tier 1 Select Agent, meaning it poses a significant threat to human and animal health and safety and presents a great potential for deliberate misuse.  The Soviet Union and the United States are both believed to have studied B. pseudomallei as a potential biological warfare agent in the 1940s.

In his extensive work caring for patients in northeast Thailand, Dr. Limmathurotsakul documents numerous cases of melioidosis on an annual basis, many of them fatal.  Thailand’s Bureau of Epidemiology, however, only documents about 12 melioidosis deaths per year.  Dr. Limmathurotsakul chalks up the disparity to a poor public health surveillance apparatus and cultural barriers in reporting.  Public health laboratories in Thailand are poorly equipped for diagnostics. Furthermore, physicians in Thailand are not well trained to utilize laboratory diagnoses, nor are they well versed in the transmission and symptoms of melioidosis.  When local health professionals do detect outbreaks of the disease, they are hesitant to report them to the Bureau of Epidemiology for fear of being stigmatized as the only locale to have a significant melioidosis outbreak.

Dr. Daily has encountered similar problems working in Cambodia.  Due to climate change, the rainy season in Cambodia lasts longer every year and with it, the number of melioidosis outbreaks detected by her team also grows.  The Cambodian government, however, is unable to respond effectively to these outbreaks due to a lack of diagnostic capability, patient data, and funding.  Treatment for the infection, which averages a cost of 65 USD, is expensive compared to the Cambodian per capita income of just over 1,100 USD.  Many families struggle to pay for treatment, often going into debt or selling property to afford it.

What can be done to improve detection and treatment of melioidosis?  All of the panel members recommended improving the education and training of the public health and medical workforce.  Knowledge of melioidosis needs to be integrated into training for public health workers in laboratory diagnosis.  Protocols for diagnosis and treatment of melioidosis should be incorporated into medical school curricula.  The speakers also expressed hopes that Thailand and Cambodia would be able to build their capacity to detect and report infectious diseases. Combining his limited data on melioidosis with predictive modeling algorithms, Dr. Limmathurotsakul has estimated that there are 165,000 cases of melioidosis worldwide each year, 89,000 of which result in death.  He hopes the estimates will spur melioidosis researchers worldwide to compile confirmed-case data and paint a more accurate picture.  Then national and international policymakers will have better information to support clinicians and public health officials in their local efforts to fight the disease.

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