The effect of climate on melioidosis incidence in Townsville, Australia: a dry tropical region.

BACKGROUND: Townsville is in the dry tropics in Northern Australia and an endemic region for melioidosis. Melioidosis is an infectious disease caused by Burkholderia pseudomallei, a soil dwelling organism. The incidence of melioidosis is associated with high levels of rainfall and has been linked to multiple weather variables in other melioidosis endemic regions such as in Darwin. In contrast to Townsville, Darwin is in the wet-dry tropics in Northern Australia and receives 40% more rainfall. We assessed the relationship between melioidosis incidence and weather conditions in Townsville and compared the patterns to the findings in Darwin and other melioidosis endemic regions. METHOD: Performing a time series analysis from 1996 to 2020, we applied a negative binomial regression model to evaluate the link between the incidence of melioidosis in Townsville and various weather variables. Akaike's information criterion was used to assess the most parsimonious model with best predictive performance. Fourier terms and lagged deviance residuals were included to control long term seasonal trends and temporal autocorrelation. RESULTS: Humidity is the strongest predictor for melioidosis incidence in Townsville. Furthermore, the incidence of melioidosis showed a three-times rise in the Townsville region when >200 mm of rain fell within the fortnight. Prolonged rainfall had more impact than a heavy downpour on the overall melioidosis incident rate. There was no statistically significant increase in incidence with cloud cover in the multivariable model. CONCLUSION: Consistent with other reports, melioidosis incidence can be attributed to humidity and rainfall in Townsville. In contrast to Darwin, there was no strong link between melioidosis cases and cloud cover and nor single large rainfall events.

The epidemiology of melioidosis in Townsville, Australia.

BACKGROUND: Melioidosis in an infection caused by Burkholderia pseudomallei, an organism endemic to tropical and subtropical regions. METHODS: This study describes the epidemiology of melioidosis in Townsville, QLD, Australia, as well as clinical features, risk factors associated with the disease, the burden of infection on the Aboriginal and Torres Strait Islander (ATSI) community and patient outcomes over time. RESULTS: From 1997 to 2020, 128 patients were admitted to Townsville University Hospital. The total annual incidence of infection was 3.2 cases per 100 000 compared with 15.3 per 100 000 in the ATSI population. The majority of cases (n=82 [64%]) were male. Alcohol excess (55%) and diabetes mellitus (48%) were the most common risk factors. Bacteraemia occurred in 87 (70%) patients and pneumonia was the most common focus of infection in 84 (69%). The case fatality rate was 23%, with no difference for the ATSI population (6/32 [19%]). The presence of malignancy was the risk factor most associated with mortality (relative risk 2.7 [95% confidence interval 1.4-5.1], p=0.005). CONCLUSIONS: The ATSI community was overrepresented in this study, however, there was no significant difference in adverse outcomes. The case fatality rate was higher than in other regions in Australia. This discrepancy may relate in part to the different risk groups seen in these settings coupled with potential organism variability.

Melioidosis: Laboratory Investigations and Association with Patient Outcomes.

Melioidosis is an infection caused by the bacterium Burkholderia pseudomallei. The most common presentation is bacteremia occurring in 38-73% of all patients, and the mortality rate ranges from 9% to 42%. Although there is abundant data representing risk factors for infection and patient outcomes, there is limited information regarding laboratory investigations associated with bacteremia and mortality. We assessed a range of baseline and diagnostic investigations and their association with patient outcomes in a retrospective cohort study in Townsville, Australia. 124 patients' medical and laboratory records were reviewed between January 1, 1997 and December 31, 2020. Twenty-seven patients died and 87 patients were bacteremic. The presence of lymphopenia (< 1.5 × 109 cells/L) was the highest risk for bacteremia (relative risk [RR] 2.2; 95% CI: 1.3-3.7, P < 0.001). Factors associated with mortality included lymphopenia, (RR: 1.4; 95% CI: 1.2-1.6, P = 0.004); uremia (RR: 1.7; 95% CI: 1.1-2.5, P = 0.03); and an elevated international normalized ratio (RR: 1.5; 95% CI: 1.2-2.0, P = 0.006). Median incubation to positive blood culture result was 28 hours with 15/82 (18%) positive in ≤ 24 hours. For serological testing during admission only 53/121 (44%) were indirect hemagglutination assay positive, 67/120 (56%) enzyme immunoassay IgG positive, and 23/89 (26%) IgM positive. Simple baseline investigations at time of presentation may be used to stratify patients at high risk for both bacteremia and mortality. This information can be used as a decision aid for early intensive management.

A retrospective analysis of the prevalence and clinical outcomes of vitamin D deficiency in myeloma patients in tropical Australia.

PURPOSE: The aim of this descriptive study was to assess the prevalence of vitamin D deficiency in patients on active therapy for multiple myeloma in a tropical climate. We also tested for the association of vitamin D status on clinical outcomes. METHODS: This was a single centre, observational study performed in Townsville, Australia, which has a sunlight heavy, tropical climate. Patients on active therapy for multiple myeloma underwent testing of serum 25-hydroxyvitamin D (25(OH)D). Information on disease stage, skeletal morbidity and symptoms of peripheral neuropathy were collected from medical records and self-reported patient questionnaires. RESULTS: A total of 41 patients were included. With a median disease duration of 38 months, 27% were found to be vitamin D deficient. Patients with vitamin D deficiency had a higher likelihood of peripheral neuropathy compared with their non-vitamin D counterparts (73% vs. 33%, P = 0.03). Although those with vitamin D deficiency had more skeletal morbidity, this was not statistically significant (73% vs 50%, P = 0.19). Reduced 25(OH) D was associated with a poor performance status (P = 0.003). There was no association between vitamin D status and stage of myeloma. CONCLUSION: There is a relatively high prevalence of vitamin D deficiency in patients with myeloma in our study. This is despite a sunlight heavy, tropical climate. We report an association between vitamin D deficiency and peripheral neuropathy. Prospective interventional trials are required to further assess this.