Limited Awareness of Melioidosis in High-risk Populations Despite an Increasing Incidence of the Disease in Far North Queensland, Australia

ABSTRACT.

The incidence of melioidosis, an opportunistic infection caused by Burkholderia pseudomallei, has recently doubled in Far North Queensland (FNQ), Australia. This contrasts with the local burden of dengue, which is nearing elimination, and the stable incidence of leptospirosis. This questionnaire-based study assessed the awareness of melioidosis among people in FNQ with risk factors for the disease, using awareness of leptospirosis and dengue as comparators. There were 427 respondents; 361 (85%) reported one or more risk factors for melioidosis. Only 69 of 361 (19%) had heard of melioidosis compared with 301 of 361 (83%) who had heard of dengue (P < 0.001) and 137 of 361 (38%) who had heard of leptospirosis (P < 0.001). In FNQ, Australia, there is an increasing local incidence of melioidosis, but there is limited awareness of the disease among high-risk individuals. Greater community awareness of melioidosis is necessary to implement strategies to prevent disease and expedite the presentation of patients with this life-threatening infection.

Burkholderia pseudomallei is an opportunistic, environmental Gram-negative bacterium that causes the disease melioidosis. People living with specific comorbidities, particularly diabetes mellitus, hazardous alcohol use, chronic lung disease, and chronic kidney disease are most at risk of developing the disease.¹ Although one model estimated that melioidosis may kill 89,000 people annually, it remains a neglected disease.^2,3

In Far North Queensland (FNQ), tropical Australia, melioidosis is a disease of socioeconomic disadvantage that disproportionately affects First Nations Australians.⁴ Between 1998 and 2019, the annual incidence of melioidosis doubled in FNQ, with a 10-fold increase in Cairns, the region’s main city.⁵ The growing burden of disease has been associated with significant morbidity and mortality; between January 1, 2017, and June 30, 2021, 185 cases of melioidosis were managed in the FNQ public health system, of which 41 (22%) required intensive care unit (ICU) support and 18 (10%) died.⁶

The increasing local incidence of melioidosis contrasts starkly with trends in the incidence of other endemic tropical infections such as dengue and leptospirosis. A multifaceted public awareness campaign and introduction of the wMel strain of Wolbachia into local Aedes aegypti mosquitoes has resulted in a rapid decrease with near elimination of locally acquired dengue.^7,8 From 2017 to 2021, the region has only seen 17 cases of locally acquired dengue, which last occurred in 2018. The incidence of leptospirosis, meanwhile, has remained stable and is largely isolated to areas of high-intensity banana, sugar cane, and cattle farming.⁹ Although the absolute number of leptospirosis and melioidosis cases in FNQ are similar, only 12% of local leptospirosis cases require ICU support, and 0.5% are fatal.^10,11

However, despite the recent increase in the local incidence of melioidosis, public health measures to highlight the disease have been limited. In 1999, an education program, posters, and pamphlets were produced with the aim of informing First Nations Australian communities of the disease.¹² Since then, ongoing health promotion has only consisted of articles in local newspapers timed to coincide with the start of the region’s wet season. This study was performed to assess the current awareness of melioidosis in people with risk factors for the disease with the aim of providing a foundation for a public health campaign to increase recognition of melioidosis in the region.

This study was performed at Cairns Hospital, a tertiary referral hospital in tropical Australia. A one-page questionnaire was designed to assess awareness of melioidosis in people with risk factors for the disease, with awareness of dengue and leptospirosis used as comparators (Supplemental Figure 1). The paper questionnaire was provided to patients attending specialist outpatient clinics at four areas within the hospital: the diabetes, renal, hepatology, and respiratory clinics. The questionnaire was available to patients attending these clinics from December 1, 2019 to April 30, 2020, and December 1, 2020 to April 30, 2021. These dates were chosen because they coincide with the region’s wet season during which almost 80% of melioidosis cases occur.¹ The questionnaire was designed to be completed anonymously and included questions on age, gender, and area of residence. Respondents were asked if they identified as an Australian First Nations person. Respondents were also asked if they had diabetes, chronic lung disease, chronic kidney disease, required renal dialysis, and if they consumed, on average, more than 2 alcoholic drinks per day.¹³ Respondents were asked if they had heard of dengue, leptospirosis, or melioidosis, and which of the three infections they felt most at risk of acquiring. Both completed and partially completed questionnaires were included in the analysis; because some individuals occasionally failed to answer all of the questions the number of respondents for each question varied slightly. The responses were entered into an electronic spreadsheet (Microsoft Excel) and analyzed using statistical software (Stata ver. 14.2). Groups were compared using the chi-square test. The Far North Queensland Human Research Ethics Committee provided ethical approval for the study (LNR/2019/QCH/58737–1394 QA).

A total of 427 adults returned a questionnaire, of which 361 (85%) reported one or more risk factors for melioidosis. The median age of these 361 respondents was 62 (interquartile range [IQR] 52–71) years; 190 of 360 (53%) were male. Most respondents lived in Cairns (278 of 361; 77%)) and 96 of 357 (27%) identified as an Australian First Nations person. Most (301 of 361; 83%) respondents had heard of dengue, but only 69 of 361 (19%) had heard of melioidosis (Table 1).

Table 1.

Awareness of dengue, leptospirosis and melioidosis in people living with risk factors for melioidosis in Far North Queensland, Australia

	Total respondents	Heard of dengue	Heard of leptospirosis	Heard of melioidosis	P*
		n (%)	n (%)	n (%)
All respondents	361	301 (83%)	137 (38%)	69 (19%)	< 0.0001
First Nations Australian	96	75 (78%)	30 (31%)	22 (23%)	< 0.0001
Diabetes mellitus	154	124 (81%)	52 (34%)	25 (16%)	< 0.0001
Hazardous alcohol use	48	40 (83%)	21 (44%)	11 (23%)	< 0.0001
CKD	251	219 (87%)	105 (42%)	52 (21%)	< 0.0001
CKD requiring dialysis	54	45 (83%)	17 (31%)	10 (19%)	< 0.0001
Chronic lung disease	70	58 (83%)	29 (41%)	11 (16%)	< 0.0001

CKD = chronic kidney disease

^*Proportion who had heard of melioidosis compared with those who had heard of dengue.

Of the three infections, most (181 of 353; 51%) respondents with risk factors for melioidosis thought they were most likely to acquire dengue, with 37of 353 (10%) thinking they were most likely to acquire leptospirosis; only 19 of 353 (5%) thought they were most likely to acquire melioidosis. There were 139 of 353 (39%) respondents who were unsure which of the infections they were most at risk of developing.

Individuals who were resident in Cairns were less likely to have heard of melioidosis than those residents outside of Cairns (44 of 278 [16%] versus 25 of 83 [30%], P = 0.004) despite the recent increase in Cairns cases. There was no difference in awareness of melioidosis among First Nations Australians and non–First Nations Australians (22/96 [23%] versus 47/261 [18%], P = 0.30) despite the higher incidence of melioidosis in First Nations Australians.

This study shows that in FNQ, tropical Australia, there is limited awareness of melioidosis among people with comorbidities that increase the risk of acquiring the disease. Awareness was particularly low in people living in Cairns, an area with a greater than 10-fold increase in the incidence of melioidosis since 1998. The consistently low awareness of melioidosis across all high-risk groups suggests that attempts to raise public awareness have had limited success. This is concerning because although there have been significant improvements in the clinical outcomes of patients with melioidosis in Australia, 30% of cases require ICU support, and the case-fatality rate in Australia’s well-resourced health system is still approximately 10%.¹⁴

It is important to note that although this study suggests an opportunity to improve awareness of melioidosis in FNQ, it is difficult to know to what extent public health measures will be effective in preventing the disease. In Australia, people with risk factors for melioidosis are advised to stay indoors when it is raining and to wear shoes outdoors. Additionally, gloves are recommended when in contact with soil or mud, and a face mask is recommended if using a pressurized water hose.^15,16 Although these measures seem logical, their impact has not been evaluated, and it is uncertain whether following this advice results in a reduction in the risk of acquiring melioidosis. Adherence to this advice—particularly staying indoors during periods of rainfall—is challenging in a region where monsoonal rains fall for approximately 5 months of the year. In Thailand, a multifaceted prevention program that targeted people with diabetes and involved a small-group intervention including advice to wear rubber boots failed to show a reduction in cases of melioidosis.¹⁷ Chemoprophylaxis is also unlikely to have a significant role.¹⁸ It may be that highlighting the disease—and its life-threatening potential—will encourage patients at risk of developing the infection to present earlier for care.

It was notable that the respondents had a high awareness of dengue. This is likely due to well-documented outbreaks in the region, although local transmission last occurred in 2018.¹⁹ A wide-reaching public awareness campaign that included radio and television advertising, social media and targeted promotional events may also be responsible. However, the hugely successful introduction of Wolbachia mosquitoes, resulting in near elimination of dengue in the region, may reduce the need for such a comprehensive ongoing awareness campaign.

Respondents in this study were also more aware of leptospirosis than melioidosis. This is surprising because in FNQ, approximately 90% of leptospirosis cases occur in rural farming areas with 85% of cases reporting occupational exposure.¹⁰ Accordingly, there is mandatory education about leptospirosis for people working in the local banana plantations, but there have been no public health awareness campaigns addressing leptospirosis promulgated in the general population. The higher rate of awareness may, however, be partly explained by education provided to dog owners who are encouraged to vaccinate their pet against leptospirosis in the region.²⁰

This study has several limitations. The questionnaire required individuals to read and respond to multiple questions independently without accounting for literacy and understanding of what was being asked. The questionnaire also relied on people self-reporting their predisposing comorbidities; these reports may have been inaccurate. Disease names were used that may not have reflected respondents’ awareness of colloquial names for the infections. The study was conducted in a hospital outpatient setting and although the respondents are likely to also have a general practitioner, patients who rely solely on hospital subspecialists to manage their health issues may forgo holistic care provided by general practitioners that includes strategies to prevent infections.

In conclusion, in FNQ, tropical Australia, there is limited awareness of melioidosis despite an increasing disease incidence. These data provide a starting point for a public health campaign that aims to reduce disease incidence and highlights that, even in high-income settings, melioidosis remains a neglected disease, despite its life-threatening potential.

Note: Supplemental materials appear at www.ajtmh.org.