The Aftermath of the Western Australian Melioidosis Outbreak.

The 1997 outbreak of septicaemic melioidosis in a remote northwestern Australian community marked a watershed in public health microbiology response to bacterial infections in regional WA. This was the first time we attempted to put a scratch team together to provide immediate disease control measures, on-site environmental microbiology assessment and follow up with molecular epidemiology. This post looks at the aftermath of the melioidosis outbreak.

Much has been learned in almost a decade and a half since the event; most notably the role of the drinking water supply as a means of distribution of the causal agent, Burkholderia pseudomallei. Though we still don’t know exactly what the final means of exposure was, the disease control measures introduced in a hurry just before Christmas 1997 and the additional measures rolled out when we identified contamination of the water treatment installations a year later appear to have worked. There have been no further septicaemic cases attributable to exposure after the original outbreak in the last decade. It therefore looks like we may have stumbled upon an unexpected method of melioidosis control. Certainly not the only effective method, but at least it’s a start.

The other big insight has been the potential for occasional long distance movement of the causal agent, B. pseudomallei as a result of severe weather events. We’ve known for some time that severe weather in northern Australia coincides with an increased occurence of melioidosis cases, but the incidental observation that peak years for the infection in WA are when tropical cyclones approach the state from a landward direction. At this point the association is based on 10 years’ data generated as a result of disease notification in WA. It will be interesting to see how this shapes up over a longer period.

Disease notification has already alerted us to possible effects of climate change on the epidemiology of melioidosis. It should also allow monitoring of the results of agricultural and mining development in the State’s north. Clearly we need to keep a close eye on the impact of industrial cultivation of rice in the Kimberley, since melioidosis is a disease of rice farmers in Southeast Asia. Mine sites and other large scale industrial developments significantly alter soil conditions and bring workers into contact with the soil. This may also change the melioidosis risk in tropical WA.

Carefully organised and effectively targeted surveillance will help pin-point the risk and deliver disease workable control measures. Lessons learned in the aftermath of the 1997 melioidosis outbreak may bring wider benefits to the booming norther part of the State.

About melioidosis.

References:

• The Aftermath of the Western Australian Melioidosis Outbreak.

MicroGnome, 6-JUN-11.

Socrates

Notes for last week’s four-lecture marathon can be found via the following links:

• Epi 1:  travel-associated infection risks: Tropical medicine masterclass, CDC Yellow book
• Epi 2: Priobes & the principles of aetiology: Principia ætiologica paper
• Diagnostics: identification & characterisation of biological agents of disease. Sepsis detectives, introduction to language of infection, substantives, verbs
• Melioidosis resource centre

Additional support materials are available to members of the University of Western Australia through WebCT.

The MicroGnome was busy in Queensland last week, revisiting his roots in soil microbiology at the 19th World Congress of Soil Science. His lecture on environmental aspects of melioidosis can be found on the Priobe Net via this link.

Other recent material on melioidosis and its corresponding priobe can be found either here on the Priobe Net or the MicroGnome site.

An editorial on melioidosis was posted recently by our colleagues at Life in the Fastlane.

Happy digging!

Once again melioidosis is in the news. Queensland Health’s Dr Jeff Hanna has highlighted the melioidosis hot spot recently identified in the vicinity of Townsville, and Darwin melioidosis export Prof Bart Currie fronts up on the ABC’s 7.30 Report tonight.

Changing climate conditions in the north, particularly in the northwest, are thought to be responsible for some of the apparent increase in cases that can be blamed on severe weather events. But occupational activities as diverse as expansion of farming, the mining industry and even the local film industry could all contribute to an increase in meaningful encounters with a contaminated environment, and therefore subsequent cases of infection.

For a recent on-line review on melioidosis, see Life in the Fast Lane.

An update on how to treat melioidosis has just been posted by one of the open-source, on-line journals. This article provides a handy summary of current treatment options in a Table, dividing treatment into three phases of infection: 0, 1 and 2.

Melioidosis is a complex bacterial infection, treatment of which combines the urgency of treating rapidly fatal Gram negative septicaemia with the need for eradication of long-term persistent disease in pulmonary, soft tissue, skeletal and other organ systems. Incremental improvements in treatment have been made as a result of multicentre collaboration across the main endemic region of Southeast Asia and northern Australia.

There is an emerging consensus on the three main patterns of antimicrobial chemotherapy; initial (Phase 1) treatment, subsequent eradication (Phase 2) therapy and most recently post-exposure (Phase 0) prophylaxis. The combination of agents used, duration of therapy and need for adjunct modalities depends on the type, severity and antimicrobial susceptibility of infection. New antibiotic and adjunct therapies are at an investigational stage but on currently available data are unlikely to make a significant impact on this potentially fatal infection.

This treatment guide has been added to our FAQ page. The entire article can be obtained via the journal’s website.

More information on melioidosis

Reference:

Inglis, T.J. The Treatment of Melioidosis. Pharmaceuticals 2010, 3, 1296-1303 [Reference]

Here are a few questions to tickle the grey cells while you kick back and prepare for another week battling germs. You might even want to use the comment option to fire back dot point, short notes style answers:

1. Give a brief account of the Burkholderias
2. Explain the differences in virulence among Burkholderia species
3. Describe recent changes in the epidemiology of melioidosis
4. Why is melioidosis often considered a tropical disease?

Have a look around the site for clues before you finalise your answer.

μgnome, 20th March