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Melioidosis – and its Wet Season connection

10 Dec 2022

Dr Ella Meumann from Menzies School of Health Research discusses melioidosis, a predominantly wet season disease caused by the soil-dwelling bacterium Burkholderia pseudomallei. Ella works with Professor Bart Currie on the Darwin Prospective Melioidosis Study, which has tracked all culture-confirmed cases of melioidosis in the Top End since 1989. She acknowledges the role of her colleagues, including Dr Kay Hodgetts, who was involved with research into the Katherine region.

Hi Ella, thanks for join­ing us. What melioi­do­sis symp­toms should nurs­es be look­ing for?

Melioi­do­sis has wide-rang­ing clin­i­cal man­i­fes­ta­tions. Pneu­mo­nia is the most com­mon pre­sen­ta­tion, and symp­toms may include fever, short­ness of breath, cough, puru­lent spu­tum pro­duc­tion, and pleu­rit­ic chest pain.

Many patients have blood­stream infec­tion, and may have sep­sis or sep­tic shock.

Any organ sys­tem in the body can be involved. Pro­sta­t­ic abscess is com­mon in men, pre­sent­ing with fever and uri­nary reten­tion. B. pseudo­ma­llei can cause abscess­es in the liv­er or spleen, and bone and joint infec­tions. Encephalomyelitis is a rare but poten­tial­ly dev­as­tat­ing presentation. 

Some cas­es have a chron­ic pre­sen­ta­tion, with cough, weight loss, and a cav­i­tary lung lesion mim­ic­k­ing tuber­cu­lo­sis. Oth­ers have a chron­ic non-heal­ing skin ulcer. Such patients may be sys­tem­i­cal­ly well. 

Melioi­do­sis should be con­sid­ered a pos­si­ble diag­no­sis in cas­es of patients with sep­sis, par­tic­u­lar­ly dur­ing the wet sea­son, and par­tic­u­lar­ly in patients with risk factors.

Which risk fac­tors exactly?

Through the Dar­win Prospec­tive Melioi­do­sis Study (DPMS), we’ve iden­ti­fied some key risk fac­tors, includ­ing dia­betes, haz­ardous alco­hol con­sump­tion, chron­ic kid­ney dis­ease, and immuno­sup­pres­sion, for exam­ple can­cer chemotherapy.

From the research, it emerged that nine patients con­tract­ed melioi­do­sis because of Kather­ine Riv­er flood­ing in Jan­u­ary 1998. Of the nine, five recalled an inoc­u­lat­ing injury. Patient his­to­ry seems high­ly rel­e­vant as well?

We think most cas­es are acquired either by per­cu­ta­neous inoc­u­la­tion through skin trau­ma, or by inhala­tion of aerosolised bac­te­ria dur­ing severe weath­er events. It’s not uncom­mon for melioi­do­sis patients to recall a par­tic­u­lar event, such as an injury sus­tained while gar­den­ing, or being caught in a severe storm. 

Some peo­ple may have occu­pa­tion­al expo­sures through their work out­doors. Oth­ers may under­take recre­ation­al activ­i­ties that increase their expo­sure. Most peo­ple exposed to B. pseudo­ma­llei do not get melioi­do­sis – it is those with comor­bidi­ties affect­ing the immune sys­tem who are most at risk.

What sort of incu­ba­tion peri­od are we deal­ing with?

Based on the time between inoc­u­lat­ing injury and symp­tom onset for patients in the DPMS, the incu­ba­tion peri­od is between one to 21 days.

How is melioi­do­sis diagnosed?

Diag­no­sis requires cul­ture of B. pseudo­ma­llei from clin­i­cal spec­i­mens. We rec­om­mend col­lect­ing blood cul­tures, ide­al­ly two sets from dif­fer­ent sites at dif­fer­ent times, throat and rec­tal swabs in Ashdown’s medi­um if that’s avail­able, and oth­er spec­i­mens depend­ing on the site of infec­tion; for exam­ple, spu­tum, urine, skin swabs, and pus spec­i­mens. If melioi­do­sis is sus­pect­ed or there are par­tic­u­lar envi­ron­men­tal expo­sures, please doc­u­ment this on the pathol­o­gy request form as it will inform spec­i­men pro­cess­ing in the laboratory.

Light­ning over the sea in Dar­win – Wire­stock Cre­ators – stock​.adobe​.com

Melioi­do­sis is under­stood to be asso­ci­at­ed with severe weath­er events. What role will cli­mate change play in the spread of melioidosis?

In the Top End, the vast major­i­ty of cas­es occur dur­ing the wet sea­son from Novem­ber to April. 

Spikes in cas­es, as seen in the Kather­ine study, can occur fol­low­ing severe weath­er events such as cyclones, high rain­fall, and high winds. 

It is pre­dict­ed that as the cli­mate changes there will be an increase in the fre­quen­cy and sever­i­ty of extreme weath­er events such as cyclones, and it is like­ly that melioi­do­sis cas­es will increase in asso­ci­a­tion those changes.

Is there also a chance it will head fur­ther south, as weath­er pat­terns shift? 

Yes. The regions of its endemic­i­ty are pre­dict­ed to expand fur­ther south in Australia. 

How far south has it been found up until now?

There have been occa­sion­al cas­es report­ed in Cen­tral Aus­tralia and in South­east Queens­land, in asso­ci­a­tion with peri­ods of heavy rainfall.

What sort of health pro­mo­tion mes­sages should remote clin­ics focus on?

Health pro­mo­tion should tar­get those at great­est risk of becom­ing unwell with melioi­do­sis – indi­vid­u­als with dia­betes, haz­ardous alco­hol con­sump­tion, chron­ic kid­ney dis­ease, or oth­er immunosuppression.

Dur­ing the wet sea­son it is rec­om­mend­ed that peo­ple wear shoes, and gloves while gar­den­ing. Peo­ple with risk fac­tors should stay indoors dur­ing storms. This advice could be incor­po­rat­ed into a health check, for example.

Cul­tur­al con­sid­er­a­tions and social dis­ad­van­tage may mean it is less like­ly for pro­tec­tive footwear to be worn in some remote areas. There’s clear­ly some com­plex­i­ty here?

More work needs to be done to under­stand the most effec­tive ways of pre­vent­ing melioi­do­sis. It is like­ly that bar­ri­ers exist to enact­ing the pre­ven­tive mea­sures described above. Some peo­ple may have hous­ing inse­cu­ri­ty, which may mean sleep­ing rough and increased B. pseudo­ma­llei expo­sure – address­ing high home­less­ness rates in remote north­ern Aus­tralia is vital. Treat­ment and pre­ven­tion of dia­betes, chron­ic kid­ney dis­ease, and haz­ardous alco­hol con­sump­tion are also very impor­tant. All of this requires ade­quate fund­ing and com­mu­ni­ty partnerships.

Rain­clouds over the high­way – tota­jla – stock​.adobe​.com

What does treat­ment look like, and what’s the role of the remote area nurse in all of this?

Treat­ment includes an inten­sive phase of at least two weeks of intra­venous antibi­otics, and an erad­i­ca­tion phase of at least three months of oral antibi­otics. The dura­tion of each phase depends on the sever­i­ty of the infec­tion and the body site that is involved, with treat­ment deci­sions made in con­sul­ta­tion with the infec­tious dis­eases team. 

Nurs­ing staff play a key role. Remote area nurs­es recog­nise sep­sis, col­lect appro­pri­ate spec­i­mens for cul­ture, and start man­age­ment with flu­ids and empir­ic sep­sis antibi­otics (as out­lined in the CARPA Stan­dard Treat­ment Man­u­al) – all of that can be life-saving. 

Like­wise once a patient returns to a com­mu­ni­ty, remote area nurs­es play an impor­tant role in sup­port­ing that per­son through the erad­i­ca­tion phase of treat­ment so that they don’t have relapse of infection.

Hos­pi­tal-based nurs­es also play an extreme­ly impor­tant role. In the Emer­gency Depart­ment, the Inten­sive Care Unit, and on the wards, they pro­vide expert man­age­ment of sep­sis. The Hos­pi­tal In The Home nurs­es play a key role in sup­port­ing com­ple­tion of intra­venous treatment.

How impor­tant is fast treatment?

It can take 48 hours for B. pseudo­ma­llei to be iso­lat­ed from clin­i­cal spec­i­mens and for the diag­no­sis of melioi­do­sis to be made. If some­one is crit­i­cal­ly unwell, there may not be time to wait for that infor­ma­tion. The rec­om­mend­ed antibi­otics out­lined in Top End sep­sis guide­lines includ­ing the CARPA Stan­dard Treat­ment Man­u­al have activ­i­ty against B. pseudomallei.

Any take­away mes­sages for our readers?

I’d just like to thank all the nurs­es involved with the care of melioi­do­sis patients in the Top End – you do a won­der­ful job!

Want to learn more about wet-weath­er dis­eases? Read the sec­ond part of our Decem­ber wet-weath­er dis­ease fea­ture on Japan­ese encephali­tis virus.