Cases of melioidosis likely to rise with temperature

By Nicola Garrett

31 May 2018

Cases of the infectious disease melioidosis are likely to rise in Australia as global warming and severe weather events become the norm, an expert warns.

Speaking to ANZAN 2018 delegates Professor Bart Currie from the Menzies School of Health Research in Darwin said the Burkholderia pseudomallei organism that causes the tropical disease originated in Australia before being introduced to Southeast Asia, with subsequent spread to Africa and the Americas.

Over the last three decades cases had been relatively steady in the Northern Territory, with 102 culture positive cases and and 132 deaths over a 28.5 year period.

“Our mortality rate is now around 12.5%, having come down from an initial mortality of around 30 percent,” Professor Currie told delegates.

However, at the end of the last decade the Northern Territory had seen a doubling of cases which was likely to be the result of an unprecedented wet season.

In 2009 and 2010 the population-based annual incidence of melioidosis was 50.2 cases per 100 000, compared with a prior mean annual incidence of 19.6 per 100 000.

Furthermore, the annual incidence of melioidosis in the Top End Indigenous population in these years was 102.4 cases per 100 000.

“1 out of every 1,000 Indigenous Australians had clinical melioidosis in that 12-month period … this is not just a statistical extrapolation… it’s a reality,” Professor Currie said.

“With our epidemiology we know that when there are severe weather events that melioidosis cases start coming in, the critically severe ones, within a week after severe rain.”

“In February this year we had five patients at one time in ICU, three on ventilators… It’s a massive resource because sometimes these patients need to be ventilated for quite a few weeks”.

Nevertheless, healthy people rarely die from the infectious disease if they are diagnosed early and given the correct treatment, Professor Currie said.

The clinical nature and severity of the illness is closely linked to the risk factors of the host. For instance, 129 of the fatalities in the NT  had at least one risk factor such as diabetes, hazardous alcohol use, kidney or lung disease. Age also played a role, with the remaining deaths occurring in the elderly.

“We really should be thinking about melioidosis as an opportunistic infection,” Professor Currie said.

He added that there were strong statistical associations between the frequency of recorded melioidosis cases and the nature and timing of rainfall related events.

“This suggests a future rise in the sea surface and ambient temperature may lead to increased melioidosis,” he warned.

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