In a paper published in Nature Microbiology last week (11 January), researchers say that melioidosis is likely to be present in most of the tropics, including 34 countries where it has never been reported.
The disease is transmitted by Burkholderia pseudomallei, a bacterium that is known to be commonly found in the soil in South-East Asia and Australia, especially in rural areas. It results in a wide range of symptoms including shortness of breath and fever, and kills half those it infects.
“The disease is mostly misdiagnosed [as tuberculosis] and treated with inappropriate antibiotics.”
Chiranjay Mukhopadhyay, Manipal University, India
The researchers say the disease is poorly known, hard to diagnose and resistant to most antibiotics.
“There had never been a case of melioidosis reported in Laos until 1999,” when a laboratory was set up, says David Dance, a clinical microbiologist at the Lao-Oxford-Mahosot Hospital Wellcome Trust Research Unit in Laos. “Since then, 934 cases of the disease have been diagnosed in the country,” adds Dance, who cowrote the paper.
Chiranjay Mukhopadhyay, a microbiologist at Manipal University in India, says: “The disease is mostly misdiagnosed [as tuberculosis] and treated with inappropriate antibiotics.”
India has recently set up lab facilities to identify cases, the paper says. But the country urgently “needs a national policy to estimate the disease burden, and also a guideline to diagnose the cases and treat them”, according to Mukhopadhyay.
To estimate the number of melioidosis cases worldwide, the scientists compiled all confirmed cases in humans and animals, and mapped places where the bacteria is found. They modelled the most favourable conditions for B. pseudomallei — such as specific soils and high rainfall and temperature — to establish everywhere it is likely to be found.
Countries where melioidosis is known or likely
The evidence provided in the paper is “comprehensive” and the projections “realistic”, says Natkunam Ketheesan, a microbiologist and immunologist at James Cook University in Australia, who edited a 2012 book on melioidosis to mark the 100th anniversary of its discovery. “Type 2 diabetes, a major risk factor for melioidosis, is also increasing globally and will impact on the burden of melioidosis,” he says. He wants policymakers to make the disease a health priority.
Anastácio Sousa, an infectious disease researcher at the Federal University of Ceará in Brazil, agrees the estimates are convincing.
“In places where the disease is studied rigorously, the figures are much higher. Does Australia have lots more cases than Brazil? Probably not, but they detect, diagnose and register melioidosis there. I hope this paper will help healthcare professionals and the health authorities take the disease more seriously.”