Susan P. Jacups

Intensity of Rainfall and Severity of Melioidosis, Australia

In a 12-year prospective study of 318 culture-confirmed cases of melioidosis from the Top End of the Northern Territory of Australia, rainfall data for individual patient locations were correlated with patient risk factors, clinical parameters, and outcomes. Median rainfall in the 14 days before admission was highest for those dying with melioidosis (211 mm), in comparison to 110 mm for those surviving (p = 0.0002). Median 14-day rainfall was also significantly higher for those admitted with pneumonia. On univariate analysis, a prior 14-day rainfall of ≥125 mm was significantly correlated with pneumonia (odds ratio [OR] 1.70 [confidence interval [CI] 1.09 to 2.65]), bacteremia (OR 1.93 [CI 1.24 to 3.02]), septic shock (OR 1.94 [CI 1.14 to 3.29]), and death (OR 2.50 [CI 1.36 to 4.57]). On multivariate analysis, rainfall in the 14 days before admission was an independent risk factor for pneumonia (p = 0.023), bacteremic pneumonia (p = 0.001), septic shock (p = 0.005), and death (p < 0.0001). Heavy monsoonal rains and winds may cause a shift towards inhalation of Burkholderia pseudomallei.

Pulmonary Manifestations of Uncomplicated Falciparum and Vivax Malaria: Cough, Small Airways Obstruction, Impaired Gas Transfer, and Increased Pulmonary Phagocytic Activity

Despite recognition of acute respiratory distress syndrome in both falciparum and vivax malaria, disease-related changes in pulmonary function have not been defined, and underlying mechanisms are not well understood. Respiratory symptoms, pulmonary function, pulmonary phagocytic cell activity, and longitudinal changes were examined in 26 adults with uncomplicated falciparum, vivax, and ovale malaria after treatment. Self-limiting cough occurred in both falciparum (36%) and vivax or ovale (53%) malaria. In infection with each malaria species, admission measures of airflow and gas transfer were lower than predicted, and mean lung (99m)technetium-sulfur-colloid uptake was significantly increased. Changes were most evident in falciparum malaria, with treatment resulting in initial worsening of airflow obstruction and gas transfer. Altered pulmonary function in malaria is common and includes airflow obstruction, impaired ventilation, impaired gas transfer, and increased pulmonary phagocytic activity, and its occurrence in both vivax and falciparum malaria suggests that there may be common underlying inflammatory mechanisms.

Ross River Virus and Barmah Forest Virus Infections: A Review of History, Ecology, and Predictive Models, with Implications for Tropical Northern Australia

The purpose of the present article is to present a review of the Ross River virus (RRV) and Barmah Forest virus (BFV) literature in relation to potential implications for future disease in tropical northern Australia. Ross River virus infection is the most common and most widespread arboviral disease in Australia, with an average of 4,800 national notifications annually. Of recent concern is the sudden rise in BFV infections; the 2005-2006 summer marked the largest BFV epidemic on record in Australia, with 1,895 notifications. Although not life-threatening, infection with either virus can cause arthritis, myalgia, and fatigue for 6 months or longer, resulting in substantial morbidity and economic impact. The geographic distribution of mosquito species and their seasonal activity is determined in large part by temperature and rainfall. Predictive models can be useful tools in providing early warning systems for epidemics of RRV and BFV infection. Various models have been developed to predict RRV outbreaks, but these appear to be mostly only regionally valid, being dependent on local ecological factors. Difficulties have arisen in developing useful models for the tropical northern parts of Australia, and to date no models have been developed for the Northern Territory. Only one model has been developed for predicting BFV infections using climate and tide variables. It is predicted that the exacerbation of current greenhouse conditions will result in longer periods of high mosquito activity in the tropical regions where RRV and BFV are already common. In addition, the endemic locations may expand further within temperate regions, and epidemics may become more frequent in those areas. Further development of predictive models should benefit public health planning by providing early warning systems of RRV and BFV infection outbreaks in different geographical locations.

Operational Use of Household Bleach to "Crash and Release" Aedes aegypti Prior to Wolbachia-Infected Mosquito Release

ABSTRACT n Dengue (family Flaviviridae, genus Flavivirus, DENV) remains the leading arboviral cause of mortality in the tropics. Wolbachia pipientis has been shown to interrupt DENV transmission and is presently being trialled as a biological control. However, deployment issues have arisen on methods to temporarily suppress wild mosquito populations before Wolbachia-infected mosquito releases. By suppressing wild populations, fewer Ae. aegypti releases are required to achieve a sustainable Wolbachia density threshold. Furthermore, public distress is reduced. This study tests the application of domestic bleach (4% NaClO) to temporarily “crash” immature Aedes populations in water-filled containers. Spray application NaClO (215 ppm) resulted in a mean 48-h mortality of 100, 100, 97, and 88% of eggs, second-instar larvae, fourth-instar larvae, and pupae, respectively. In the field, NaClO delayed ovipositing by 9 d in cooler months, and 11 d in hotter months, after which oviposition resumed in treated receptacles. We found bleach treatment of pot-plant bases did not cause wilting, yellowing, or dropping of leaves in two ornamental plants species. Domestically available NaClO could be adopted for a “crash and release” strategy to temporarily suppress wild populations of Ae. aegypti in containers before release of Wolbachia-infected mosquitoes. The “crash and release” strategy is also applicable to other mosquito species, e.g., Aedes albopictus (Skuse), in strategies using released mosquitoes.

Arbovirus Models to Provide Practical Management Tools for Mosquito Control and Disease Prevention in the Northern Territory, Australia

ABSTRACT Ross River virus (RRV) causes the most common human arbovirus disease in Australia. Although the disease is nonfatal, the associated arthritis and postinfection fatigue can be debilitating for many months, impacting on workforce participation. We sought to create an early-warning system to notify of approaching RRV disease outbreak conditions for major townships in the Northern Territory. By applying a logistic regression model to meteorologic factors, including rainfall, a postestimation analysis of sensitivity and specificity can create rainfall cut-points. These rainfall cut-points indicate the rainfall level above which previous epidemic conditions have occurred. Furthermore, rainfall cut-points indirectly adjust for vertebrate host data from the agile wallaby (Macropus agilis) as the life cycle of the agile wallaby is intricately meshed with the wet season. Once generated, cut-points can thus be used prospectively to allow timely implementation of larval survey and control measures and public health warnings to preemptively reduce RRV disease incidence. Cut-points are location specific and have the capacity to replace previously used models, which require data management and input, and rarely provide timely notification for vector control requirements and public health warnings. These methods can be adapted for use elsewhere.

Evaluation of bifenthrin applications in tires to prevent Aedes mosquito breeding.

Abstract The efficacy of maximum label rates of bifenthrin applications to dry tires to prevent Aedes mosquito breeding was investigated by field colonization and bioassay trials in shaded and unshaded locations. Aedes notoscriptus and Culex quinquefasciatus larvae were the most abundant species present in the field colonization trial. Colonization and survival of Ae. notoscriptus larvae to the late instar occurred significantly earlier in treated tires in shaded compared with unshaded locations (P u200a=u200a 0.002). Bifenthrin applications in shaded tires only prevented early instar survival for ∼2.6 wk. Aedes notoscriptus late instars did not appear in the treated unshaded tires. Culex quinquefasciatus colonized treated tires from the 2nd wk in both shaded and unshaded treatments. In the bioassay, water from bifenthrin-treated tires, through extrapolation, was found to kill ∼100% of late instar Ae. notoscriptus for only ∼2.0–2.2 wk in shaded and unshaded tires. Under conditions optimal for Aedes breeding, such as shaded locations, high ambient temperatures, high relative humidity, and high amounts of leaf/organic matter accumulations, bifenthrin may not be effective as a larval control measure in tires for greater than 2.0–2.6 wk.

Bacillus thuringiensis var. israelensis Misting for Control of Aedes in Cryptic Ground Containers in North Queensland, Australia

In Australia, dengue is not endemic, although the vector mosquito Aedes aegypti is established in far north Queensland (FNQ). Aedes albopictus has recently invaded the Torres Strait region, but is not established on mainland Australia. To maintain dengue-free, public health departments in FNQ closely monitor introduced dengue infections and confine outbreaks through rigorous vector control responses. To safeguard mainland Australia from Ae. albopictus establishment, pre-emptive strategies are required to reduce its breeding in difficult to access habitats. We compare the residual efficacy of VectoBac WDG, Bacillus thuringiensis var. israelensis (Bti) formulation, as a residual treatment when misted across a typical FNQ bushland using a backpack mister (Stihl SR 420 Mist Blower) at two dose rates up to 16 m. Semi-field condition results, over 16 weeks, indicate that Bti provided high mortality rates (> 80%) sustained for 11 weeks. Mist application penetrated 16 m of dense bushland without efficacy decline over distance.

Efficacy of Alpha-Cypermethrin and Lambda-Cyhalothrin Applications to Prevent Aedes Breeding in Tires

Abstract The efficacy of alpha-cypermethrin (Cyperthor®) and lambda-cyhalothrin (Demand®) to prevent mosquito larval colonization of water-containing receptacles was investigated using 2 differing applications in disused car tires in Darwin, Australia. Insecticide treatments were applied uniformly to the inside surfaces of 2 categories of tires: 1) dry tires that were partially filled with water 24 h after spraying and 2) wet tires partially filled with water prior to spraying. All mosquito larvae, pupae, and dead adults were collected from the treatment and control tires weekly over the 24-wk study period and were later identified to species in the laboratory. Control tires were colonized by Aedes notoscriptus in wk 2 and by Culex quinquefasciatus in wk 4. Aedes notoscriptus failed to colonize any alpha-cypermethrin–treated tires until wk 22 and did not colonize any lambda-cyhalothrin–treated tires during the 24-wk trial. Culex quinquefasciatus colonized alpha-cypermethrin– and lambda-cyhalothrin–treated tires from wk 11 and wk 15, respectively. These results indicate both insecticides using either application method can prevent colonization of Ae. notoscriptus for at least 20 wk and demonstrate great potential for the prevention of breeding in receptacles for other receptacle-breeding Aedes species, such as the dengue vectors, Ae. aegypti and Ae. albopictus.

Psycho-social resilience, vulnerability and suicide prevention: impact evaluation of a mentoring approach to modify suicide risk for remote Indigenous Australian students at boarding school.

BackgroundThe proposed study was developed in response to increased suicide risk identified in Aboriginal and Torres Strait Islander students who are compelled to attend boarding schools across Queensland when there is no secondary schooling provision in their remote home communities. It will investigate the impact of a multicomponent mentoring intervention to increase levels of psychosocial resilience. We aim to test the null hypothesis that students’ resilience is not positively influenced by the intervention. The 5-year project was funded by the Australian National Health and Medical Research Council from December 2014.Methods/DesignAn integrated mixed methods approach will be adopted; each component iteratively informing the other. Using an interrupted time series design, the primary research methods are quantitative: 1) assessment of change in students’ resilience, educational outcomes and suicide risk; and 2) calculation of costs of the intervention. Secondary methods are qualitative: 3) a grounded theoretical model of the process of enhancing students’ psychosocial resilience to protect against suicide. Additionally, there is a tertiary focus on capacity development: more experienced researchers in the team will provide research mentorship to less experienced researchers through regular meetings; while Indigenous team members provide cultural mentorship in research practices to non-Indigenous members.DiscussionAustralia’s suicide prevention policy is progressive but a strong service delivery model is lacking, particularly for Indigenous peoples. The proposed research will potentially improve students’ levels of resilience to mitigate against suicide risk. Additionally, it could reduce the economic and social costs of Indigenous youth suicide by obtaining agreement on what is good suicide prevention practice for remote Indigenous students who transition to boarding schools for education, and identifying the benefits-costs of an evidence-based multi-component mentoring intervention to improve resilience.

Anthropogenic ecological change and impacts on mosquito breeding and control strategies in salt-marshes, Northern Territory, Australia.

Darwin, in the tropical north of Australia, is subject to high numbers of mosquitoes and several mosquito-borne diseases. Many of Darwin’s residential areas were built in close proximity to tidally influenced swamps, where long-term storm-water run-off from nearby residences into these swamps has led to anthropogenic induced ecological change. When natural wet–dry cycles were disrupted, bare mud-flats and mangroves were transformed into perennial fresh to brackish-water reed swamps. Reed swamps provided year-round breeding habitat for many mosquito species, such that mosquito abundance was less predictable and seasonally dependent, but constant and often occurring in plague proportions. Drainage channels were constructed throughout the wetlands to reduce pooled water during dry-season months. This study assesses the impact of drainage interventions on vegetation and mosquito ecology in three salt-marshes in the Darwin area. Findings revealed a universal decline in dry-season mosquito abundance in each wetland system. However, some mosquito species increased in abundance during wet-season months. Due to the high expense and potentially detrimental environmental impacts of ecosystem and non-target species disturbance, large-scale modifications such as these are sparingly undertaken. However, our results indicate that some large scale environmental modification can assist the process of wetland restoration, as appears to be the case for these salt marsh systems. Drainage in all three systems has been restored to closer to their original salt-marsh ecosystems, while reducing mosquito abundances, thereby potentially lowering the risk of vector-borne disease transmission and mosquito pest biting problems.