Comparison of Immunochromatographic Test (ICT) and Filariasis Test Strip (FTS) for Detecting Lymphatic Filariasis Antigen in American Samoa, 2016

Circulating filarial antigen (Ag) prevalence, measured using rapid point-of-care tests, is the standard indicator used for monitoring and surveillance in the Global Program to Eliminate Lymphatic Filariasis. In 2015, the immunochromatographic test (ICT) was replaced with the filariasis test strip (FTS), which has higher reported sensitivity. Despite differences in sensitivity, no changes in recommended surveillance targets were made when the FTS was introduced. In 2016, we conducted lymphatic filariasis surveys in American Samoa using FTS, which found higher Ag prevalence than previous surveys that used ICT. To determine whether the increase was real, we assessed the concordance between FTS and ICT results by paired testing of heparinised blood from 179 individuals (63% FTS-positive). ICT had 93.8% sensitivity and 100% specificity for identifying FTS-positive persons, and sensitivity was not associated with age, gender, or presence of microfilariae. Based on these findings, if ICT had been used in the 2016 surveys, the results and interpretation would have been similar to those reported using FTS. American Samoa would have failed Transmission Assessment Survey (TAS) of Grade 1 and 2 children with either test, and community prevalence would not have been significantly different (4.1%, 95% CI, 3.3-4.9% with FTS vs. predicted 3.8%, 95%, CI: 3.1-4.6% with ICT).

Efficacy of one-dose intramuscular rabies vaccine as pre-exposure prophylaxis in travellers

BACKGROUND

Current guidelines for rabies pre-exposure prophylaxis (PrEP) recommend multiple vaccine doses. Travellers sometimes present for pre-travel consultation with insufficient time to complete standard PrEP schedules. We investigated the efficacy of one-dose intramuscular (IM) vaccine in priming the immune system (as PrEP) by measuring antibody response to simulated post-exposure prophylaxis (PEP).

METHODS

A quasi-experimental pre-post intervention clinical trial was conducted at a specialist travel clinic in Australia. Adults (≥18 years) without a history of rabies vaccination were included. At Visit 1, seronegative status was confirmed and one dose of 0.5 ml IM rabies vaccine (Verorab®) administered. At Visit 2 (≥60 days after Visit 1), serology was repeated and a simulated PEP dose (0.5 ml IM) given on this day and again 3 days later (Visit 3). Serology was repeated at Visit 4 (7 days after Visit 2).

RESULTS

A total of 94 antibody-negative participants were included (<50 years [n = 50]; ≥50 years [n = 44]). At Visit 2, 38.0 and 31.8% of participants aged <50 and ≥50 years were antibody-positive (≥0.5 EU/ml). At Visit 4, all participants were antibody-positive; 82.0 and 47.7% of participants aged <50 and ≥50 years had antibody levels >4 EU/ml, respectively.

CONCLUSIONS

One-dose IM vaccine was effective as PrEP for priming the immune system in both age groups, resulting in rapid development of antibodies 7 days after commencing simulated PEP. If there is insufficient time to complete a standard PrEP schedule, one-dose IM could be considered as an alternative schedule for short trips, rather than not offering travellers any doses at all.Clinical trials registration: ACTRN12619000946112.

Efficacy of a 3-day pretravel schedule of tafenoquine for malaria chemoprophylaxis: a network meta-analysis

BACKGROUND

Chemoprophylaxis with weekly doses of tafenoquine (200 mg/day for 3 days before departure [loading dose], 200 mg/week during travel and 1-week post-travel [maintenance doses]) is effective in preventing malaria. Effectiveness of malaria chemoprophylaxis drugs in travellers is often compromised by poor compliance. Shorter schedules that can be completed before travel, allowing 'drug-free holidays', could increase compliance and thus reduce travel-related malaria. In this meta-analysis, we examined if a loading dose of tafenoquine alone is effective in preventing malaria in short-term travellers.

METHODS

Four databases were searched in November 2020 for randomized controlled trials (RCTs) that assessed efficacy and/or safety of tafenoquine for chemoprophylaxis. Network meta-analysis using the generalized pair-wise modelling framework was utilized to estimate the odds ratio (OR) of malaria infection in long-term (>28 days) and short-term (≤28 days) travellers, as well as adverse events (AEs) associated with receiving loading dose of tafenoquine alone, loading dose of tafenoquine followed by maintenance doses, loading dose of mefloquine followed by maintenance doses, or placebo.

RESULTS

Nine RCTs (1714 participants) were included. In long-term travellers, compared to mefloquine, tafenoquine with maintenance doses (OR = 1.05; 95% confidence interval [CI]: 0.44-2.46) was equally effective in preventing malaria, while there was an increased risk of infection with the loading dose of tafenoquine alone (OR = 2.89; 95% CI: 0.78-10.68) and placebo (OR = 62.91; 95% CI: 8.53-463.88). In short-term travellers, loading dose of tafenoquine alone (OR = 0.98; 95% CI: 0.04-22.42) and tafenoquine with maintenance doses (OR = 1.00; 95% CI: 0.06-16.10) were as effective as mefloquine. The risk of AEs with tafenoquine with maintenance doses (OR = 1.03; 95% CI: 0.67-1.60) was similar to mefloquine, while loading dose of tafenoquine alone (OR = 0.58; 95% CI: 0.20-1.66) was associated with lower risk of AEs, although the difference was not statistically significant.

CONCLUSIONS

For short-term travellers, loading dose of tafenoquine alone was equally effective, had possibly lower rate of AEs, and likely better compliance than standard tafenoquine or mefloquine chemoprophylaxis schedules with maintenance doses. Studies are needed to confirm if short-term travellers remain free of infection after long-term follow-up.

REGISTRATION

The meta-analysis was registered in PROSPERO (CRD42021223756).

HIGHLIGHT

Tafenoquine is the latest approved drug for malaria chemoprophylaxis. A loading dose of tafenoquine (200 mg/day for 3 days before departure) is as effective in preventing malaria in short-term (≤28 days) travellers as chemoprophylaxis schedules of tafenoquine or mefloquine with maintenance doses, allowing travellers to have a 'drug-free holiday'.

Transmission modelling of environmentally persistent zoonotic diseases: a systematic review

Transmission of many infectious diseases depends on interactions between humans, animals, and the environment. Incorporating these complex processes in transmission dynamic models can help inform policy and disease control interventions. We identified 20 diseases involving environmentally persistent pathogens (ie, pathogens that survive for more than 48 h in the environment and can cause subsequent human infections), of which indirect transmission can occur from animals to humans via the environment. Using a systematic approach, we critically appraised dynamic transmission models for environmentally persistent zoonotic diseases to quantify traits of models across diseases. 210 transmission modelling studies were identified and most studies considered diseases of domestic animals or high-income settings, or both. We found that less than half of studies validated their models to real-world data, and environmental data on pathogen persistence was rarely incorporated. Model structures varied, with few studies considering the animal-human-environment interface of transmission in the context of a One Health framework. This Review highlights the need for more data-driven modelling of these diseases and a holistic One Health approach to model these pathogens to inform disease prevention and control strategies.

Comparison of immunogenicity and safety of licensed Japanese encephalitis vaccines: A systematic review and network meta-analysis

INTRODUCTION

Annually more than 100,000 Japanese encephalitis (JE) cases and 25,000 deaths worldwide are caused by JE virus infection. More than 15 JE vaccines are currently in use worldwide. It is unknown whether any of the vaccines is superior to the others in terms of immunogenicity and safety.

METHODS

Four databases were systematically searched for randomised controlled trials that compared two or more types of JE vaccines. Vaccines were classified into four classes: inactivated mouse brain-derived (oldest class), inactivated Vero cell, live chimeric, and live attenuated. Network meta-analysis was used to generate mixed effect estimates against inactivated mouse brain-derived vaccines for seroconversion, and against placebo for adverse event (AE) and severe adverse event (SAE).

RESULTS

23 studies (38,496 participants) were included. All newer vaccine classes had better immunogenicity, the difference was statistically significant for inactivated Vero cell (OR = 2.98; 95 %CI: 1.02-8.65) and live chimeric (OR = 5.93; 95 %CI: 1.73-20.32) vaccines. Inactivated mouse-derived vaccines had the highest odds for AEs (OR = 2.27; 95 %CI: 1.59-3.23), the odds of AE of newer vaccines was not different to placebo. There was no difference in SAEs across vaccine classes.

CONCLUSIONS

All newer JE vaccines have comparable safety profiles, live chimeric and inactivated Vero cell vaccines are the most immunogenic among the newer vaccine classes.

Spatial prediction of malaria prevalence in Papua New Guinea: a comparison of Bayesian decision network and multivariate regression modelling approaches for improved accuracy in prevalence prediction

Background

Considerable progress towards controlling malaria has been made in Papua New Guinea through the national malaria control programme’s free distribution of long-lasting insecticidal nets, improved diagnosis with rapid diagnostic tests and improved access to artemisinin combination therapy. Predictive prevalence maps can help to inform targeted interventions and monitor changes in malaria epidemiology over time as control efforts continue. This study aims to compare the predictive performance of prevalence maps generated using Bayesian decision network (BDN) models and multilevel logistic regression models (a type of generalized linear model, GLM) in terms of malaria spatial risk prediction accuracy.

Methods

Multilevel logistic regression models and BDN models were developed using 2010/2011 malaria prevalence survey data collected from 77 randomly selected villages to determine associations of Plasmodium falciparum and Plasmodium vivax prevalence with precipitation, temperature, elevation, slope (terrain aspect), enhanced vegetation index and distance to the coast. Predictive performance of multilevel logistic regression and BDN models were compared by cross-validation methods.

Results

Prevalence of P. falciparum, based on results obtained from GLMs was significantly associated with precipitation during the 3 driest months of the year, June to August (β = 0.015; 95% CI = 0.01–0.03), whereas P. vivax infection was associated with elevation (β = − 0.26; 95% CI = − 0.38 to − 3.04), precipitation during the 3 driest months of the year (β = 0.01; 95% CI = − 0.01–0.02) and slope (β = 0.12; 95% CI = 0.05–0.19). Compared with GLM model performance, BDNs showed improved accuracy in prediction of the prevalence of P. falciparum (AUC = 0.49 versus 0.75, respectively) and P. vivax (AUC = 0.56 versus 0.74, respectively) on cross-validation.

Conclusions

BDNs provide a more flexible modelling framework than GLMs and may have a better predictive performance when developing malaria prevalence maps due to the multiple interacting factors that drive malaria prevalence in different geographical areas. When developing malaria prevalence maps, BDNs may be particularly useful in predicting prevalence where spatial variation in climate and environmental drivers of malaria transmission exists, as is the case in Papua New Guinea.

Triple-Drug Treatment Is Effective for Lymphatic Filariasis Microfilaria Clearance in Samoa

Following the first triple-drug mass drug administration (MDA) for lymphatic filariasis in Samoa in 2018, unexpected persistence of microfilaria (Mf) positivity in 18 (15%) of 121 antigen-positive persons was observed in a nationwide household survey 1–2 months later. Of the 18 Mf positive persons, 14 reported taking the MDA, raising concerns about MDA efficacy. In 2019, 5–6 months after the 2018 survey, a monitored treatment study was done to evaluate directly observed weight-based treatment in these Mf positive individuals. Mf presence and density were assessed before and 7 days after treatment, using 1 mL membrane filtered venous blood, and 60 uL thick blood films on slides prepared from venous or fingerprick blood. All 14 participants were still Mf positive on filters from venous blood pre-treatment samples, but two were negative by slide made from the same samples. Mf were cleared completely by day 7 in 12 of 13 participants followed up, and by day 30 in the remaining participant. Filtered blood using EDTA samples (to reduce clumping of Mf) is preferred over slides alone for improving the likelihood of detecting Mf and estimating their density. The triple-drug MDA strategy was effective at clearing Mf when given and taken at the correct dose.

Novel statistical approaches to identify risk factors for soil-transmitted helminth infection in Timor-Leste

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We compared logistic regression, recursive partitioning and Bayesian networks to identify risk factors for STH infection.

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Logistic regression identified fewest variables associated with STH infections compared with the two alternative methods.

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Recursive partitioning identified more demographic and WASH variables, and Bayesian networks more environmental variables.

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Model performance was similar across all three statistical techniques.

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Recursive partitioning can identify at-risk population subgroups, while Bayesian networks can run real-time scenarios.

Soil-transmitted helminths (STHs) are parasitic intestinal worms that infect almost a fifth of the global population. Sustainable control of STHs requires understanding the complex interaction of factors contributing to transmission. Identifying risk factors has mainly relied on logistic regression models where the underlying assumption of independence between variables is not always satisfied. Previously demonstrated risk factors including water, sanitation and hygiene (WASH) access and behaviours, and socioeconomic status are intrinsically linked. Similarly, environmental factors including climate, soil and land attributes are often strongly correlated. Alternative methods such as recursive partitioning and Bayesian networks can handle correlated variables, but there are no published studies comparing these methods with logistic regression in the context of STH risk factor analysis. Baseline cross-sectional data from school-aged children in the (S)WASH-D for Worms study were used to compare risk factors identified from modelling the same data using three different statistical techniques. Outcomes of interest were infection with Ascaris spp. and any hookworm species (Necator americanus, Ancylostoma duodenale, and Ancylostoma ceylanicum). Mixed-effects logistic regression identified the fewest risk factors. Recursive partitioning identified the most WASH and demographic risk factors, while Bayesian networks identified the most environmental risk factors. Recursive partitioning produced classification trees that visualised potentially at-risk population sub-groups. Bayesian networks helped visualise relationships between variables and enabled interactive modelling of outcomes based on different scenarios for the predictor variables of interest. Model performance was similar across all techniques. Risk factors identified across all techniques were vegetation for Ascaris spp., and cleaning oneself with water after defecating for hookworm. This study adds to the limited body of evidence exploring alternative data modelling approaches in identifying risk factors for STH infections. Our findings suggest these approaches can provide novel insights for more robust interpretation.

Adverse Events Following Immunization With Combined vs Concurrent Monovalent Hepatitis A and Typhoid Vaccines in Children

Combined hepatitis A and typhoid vaccine is available in Australia, but licensed for use from age 16 years; however it is used "off-label" in children. The combined vaccine is well tolerated in children aged 2-16 years and the risk of adverse events is similar to those receiving concurrent monovalent vaccines.

Interactions between timing and transmissibility explain diverse flavivirus dynamics in Fiji

Zika virus (ZIKV) has caused large, brief outbreaks in isolated populations, however ZIKV can also persist at low levels over multiple years. The reasons for these diverse transmission dynamics remain poorly understood. In Fiji, which has experienced multiple large single-season dengue epidemics, there was evidence of multi-year transmission of ZIKV between 2013 and 2017. To identify factors that could explain these differences in dynamics between closely related mosquito-borne flaviviruses, we jointly fit a transmission dynamic model to surveillance, serological and molecular data. We estimate that the observed dynamics of ZIKV were the result of two key factors: strong seasonal effects, which created an ecologically optimal time of year for outbreaks; and introduction of ZIKV after this optimal time, which allowed ZIKV transmission to persist over multiple seasons. The ability to jointly fit to multiple data sources could help identify a similar range of possible outbreak dynamics in other settings.

Has the effectiveness of Australia's travel bans against China on the importation of COVID-19 been overestimated?

In our re-analysis with adjusted assumptions, we found that a previous study substantially oversestimated the effectiveness of Australia’s complete travel ban against China in the introduction of SARS-CoV-2 into Australia.

Immunogenicity after pre- and post-exposure rabies vaccination: A systematic review and dose-response meta-analysis

BACKGROUND

There are a myriad of vaccine schedules for rabies pre- (PrEP) and post-exposure prophylaxis (PEP) that differ in the number and timedoses, number of visits, length of schedule, and route of administration. The objective of this study was to systematically review the evidence and investigate how thedifferences in schedules influence titres over time.

METHODS

Four databaseswere searched from inception to January 2020 for rabies PrEP and PEP studies. Adose-response meta-analysis was utilised to pool geometric mean titres (GMT) over time. Subgroup analyses by route of administration, age group, and schedule were conducted.

RESULTS

80 studies met the inclusion criteria and contributed with 191 datasets and 12,413 participants. Both intradermal (ID) and intramuscular (IM) PrEP/PEP produce adequate GMTs. Significantly lower GMT levels were achieved in older (>50yrs) compared to younger (<50yrs) participants. Short 1-week schedules were as effective as longer schedules that can take between 3 and 12 weeks to complete.

CONCLUSIONS

Several effective ID and IM schedules were identified, the selection of a schedule should take into account the patient's needs, costs, availability to return for subsequent doses, and the time required to complete the schedule. Older individuals warrant special attention as they develop lower antibody response.

Could intradermal be an economical alternative route of administration for Japanese encephalitis vaccines?

Highlight Uptake of Japanese encephalitis (JE) vaccine remains low among travellers, with cost of vaccines likely being one of the main hurdles. We found that smaller doses of JE vaccine administered via intradermal (ID) had similar effect on seroconversion than standard doses administered via subcutaneous. ID is a cheaper yet effective route of JE vaccine administration, and could potentially increase vaccination uptake among travellers.

Lymphatic filariasis epidemiology in Samoa in 2018: Geographic clustering and higher antigen prevalence in older age groups

BACKGROUND

Samoa conducted eight nationwide rounds of mass drug administration (MDA) for lymphatic filariasis (LF) between 1999 and 2011, and two targeted rounds in 2015 and 2017 in North West Upolu (NWU), one of three evaluation units (EUs). Transmission Assessment Surveys (TAS) were conducted in 2013 (failed in NWU) and 2017 (all three EUs failed). In 2018, Samoa was the first in the world to distribute nationwide triple-drug MDA using ivermectin, diethylcarbamazine, and albendazole. Surveillance and Monitoring to Eliminate LF and Scabies from Samoa (SaMELFS Samoa) is an operational research program designed to evaluate the effectiveness of triple-drug MDA on LF transmission and scabies prevalence in Samoa, and to compare the usefulness of different indicators of LF transmission. This paper reports results from the 2018 baseline survey and aims to i) investigate antigen (Ag) prevalence and spatial epidemiology, including geographic clustering; ii) compare Ag prevalence between two different age groups (5-9 years versus ≥10 years) as indicators of areas of ongoing transmission; and iii) assess the prevalence of limb lymphedema in those aged ≥15 years.

METHODS

A community-based cluster survey was conducted in 30 randomly selected and five purposively selected clusters (primary sampling units, PSUs), each comprising one or two villages. Participants were recruited through household surveys (age ≥5 years) and convenience surveys (age 5-9 years). Alere Filariasis Test Strips (FTS) were used to detect Ag, and prevalence was adjusted for survey design and standardized for age and gender. Adjusted Ag prevalence was estimated for each age group (5-9, ≥10, and all ages ≥5 years) for random and purposive PSUs, and by region. Intraclass correlation (ICC) was used to quantify clustering at regions, PSUs, and households.

RESULTS

A total of 3940 persons were included (1942 children aged 5-9 years, 1998 persons aged ≥10 years). Adjusted Ag prevalence in all ages ≥5 years in randomly and purposively selected PSUs were 4.0% (95% CI 2.8-5.6%) and 10.0% (95% CI 7.4-13.4%), respectively. In random PSUs, Ag prevalence was lower in those aged 5-9 years (1.3%, 95% CI 0.8-2.1%) than ≥10 years (4.7%, 95% CI 3.1-7.0%), and poorly correlated at the PSU level (R-square = 0.1459). Adjusted Ag prevalence in PSUs ranged from 0% to 10.3% (95% CI 5.9-17.6%) in randomly selected and 3.8% (95% CI 1.3-10.8%) to 20.0% (95% CI 15.3-25.8%) in purposively selected PSUs. ICC for Ag-positive individuals was higher at households (0.46) compared to PSUs (0.18) and regions (0.01).

CONCLUSIONS

Our study confirmed ongoing transmission of LF in Samoa, in accordance with the 2017 TAS results. Ag prevalence varied significantly between PSUs, and there was poor correlation between prevalence in 5-9 year-olds and older ages, who had threefold higher prevalence. Sampling older age groups would provide more accurate estimates of overall prevalence, and be more sensitive for identifying residual hotspots. Higher prevalence in purposively selected PSUs shows local knowledge can help identify at least some hotspots.

A community survey of coverage and adverse events following country-wide triple-drug mass drug administration for lymphatic filariasis elimination, Samoa 2018

The Global Programme to Eliminate Lymphatic Filariasis has made considerable progress but is experiencing challenges in meeting targets in some countries. Recent World Health Organization guidelines have recommended two rounds of triple-drug therapy with ivermectin, diethylcarbamazine (DEC), and albendazole (IDA), in areas where mass drug administration (MDA) results with two drugs (DEC and albendazole) have been suboptimal, as is the case in Samoa. In August 2018, Samoa was the first country in the world to implement countrywide triple-drug MDA. This paper aims to describe Samoa’s experience with program coverage and adverse events (AEs) in the first round of triple-drug MDA. We conducted a large cross-sectional community survey to assess MDA awareness, reach, compliance, coverage and AEs in September/October 2018, 7–11 weeks after the first round of triple-drug MDA. In our sample of 4420 people aged ≥2 years (2.2% of the population), age-adjusted estimates indicated that 89.0% of the eligible population were offered MDA, 83.9% of the eligible population took MDA (program coverage), and 80.2% of the total population took MDA (epidemiological coverage). Overall, 83.8% (2986/3563) reported that they did not feel unwell at all after taking MDA. Mild AEs (feeling unwell but able to do normal everyday things) were reported by 13.3% (476/3563) and moderate or severe AEs (feeling unwell and being unable to do normal everyday activities such as going to work or school) by 2.9% (103/3563) of participants. This study following the 2018 triple-drug MDA in Samoa demonstrated a high reported program awareness and reach of 90.8% and 89.0%, respectively. Age-adjusted program coverage of 83.9% of the total population showed that MDA was well accepted and well tolerated by the community.

Lymphatic filariasis is a disease caused by worms and transmitted between humans by mosquitoes. A global program underway aims to eliminate lymphatic filariasis as a public health problem by distributing two deworming drugs to the whole population once a year for at least five years. In some countries, including Samoa, this strategy has not been sufficient to eliminate transmission. A new drug has been added, and in 2018, Samoa was the first country in the world to distribute country-wide triple-drug mass drug administration (MDA) using ivermectin, diethylcarbamazine, and albendazole. This study reports on the coverage achieved (percentage of people who reported taking the drugs) and adverse events after taking the drugs. The study was a large community survey of over 4000 people, done 7–11 weeks after the distribution of the first round of triple-drug MDA. We found that the program reached and offered MDA to approximately 90% of the whole population, and approximately 80% of the whole population swallowed the drugs. We also collected data on whether people felt unwell after taking the pills, and found that 84% of people taking the pills did not feel unwell at all, while 13% reported feeling unwell afterwards but were able to do normal everyday activities, and 3% reported that they had felt unwell and that it stopped them doing normal everyday activities, such as going to school or work.

Supporting elimination of lymphatic filariasis in Samoa by predicting locations of residual infection using machine learning and geostatistics

The global elimination of lymphatic filariasis (LF) is a major focus of the World Health Organization. One key challenge is locating residual infections that can perpetuate the transmission cycle. We show how a targeted sampling strategy using predictions from a geospatial model, combining random forests and geostatistics, can improve the sampling efficiency for identifying locations with high infection prevalence. Predictions were made based on the household locations of infected persons identified from previous surveys, and environmental variables relevant to mosquito density. Results show that targeting sampling using model predictions would have allowed 52% of infections to be identified by sampling just 17.7% of households. The odds ratio for identifying an infected individual in a household at a predicted high risk compared to a predicted low risk location was 10.2 (95% CI 4.2-22.8). This study provides evidence that a 'one size fits all' approach is unlikely to yield optimal results when making programmatic decisions based on model predictions. Instead, model assumptions and definitions should be tailored to each situation based on the objective of the surveillance program. When predictions are used in the context of the program objectives, they can result in a dramatic improvement in the efficiency of locating infected individuals.

An evaluation of enhanced surveillance of hospitalised COVID-19 patients to inform the public health response in Victoria

Background

Public health surveillance is crucial for supporting a rapid and effective response to public health emergencies. In response to the coronavirus disease (COVID-19) pandemic, an enhanced surveillance system of hospitalised COVID-19 patients was established by the Victorian Department of Health and Human Services (DHHS) and the Victorian Healthcare Associated Infection Surveillance System Coordinating Centre. The system aimed to reduce workforce capacity constraints and increase situational awareness on the status of hospitalised patients.

Methods

The system was evaluated, using guidelines from the United States Centers for Disease Control and Prevention, against eight attributes: acceptability; data quality; flexibility; representativeness; simplicity; stability; timeliness; and usefulness. Evidence was generated from stakeholder consultation, participant observation, document review, systems review, issues log review and audits. Data were collected and analysed over a period of up to three months, covering pre- and post-implementation from March to June 2020.

Results

This system was rapidly established by leveraging established relationships and infrastructure. Stakeholders agreed that the system was important but was limited by a reliance on daily manual labour (including weekends), which impeded scalability. The ability of the system to perform well in each attribute was expected to shift with the severity of the pandemic; however, at the time of this evaluation, when there were an average 23 new cases per day (0.3 cases per 100,000 population per day), the system performed well.

Conclusion

This enhanced surveillance system was useful and achieved its key DHHS objectives during the COVID-19 public health emergency in Victoria. Recommendations for improvement were made to the current and future systems, including the need to plan alternatives to improve the system's scalability and to maintain stakeholder acceptability.

Intradermal rabies pre-exposure vaccination schedules in older travellers: comparison of immunogenicity post-primary course and post-booster

BACKGROUND

Intradermal (ID) rabies vaccination for pre-exposure prophylaxis (PrEP) has become increasingly popular; however, there is limited evidence about the effectiveness of different ID PrEP schedules in travellers aged > 50 years or their response to ID boosters. This study aimed to compare across different ID vaccine schedules and age groups the proportion of travellers who were seropositive after (i) primary course of ID PrEP and (ii) a booster.

METHODS

Travellers who received ID PrEP at a travel medicine clinic in South Australia from 2000 to 2016 were included. Three schedules were examined: 1IDx3 (1 × 0.1 ml on days 0, 7, 21-28), 2IDx2 (2 × 0.1 ml on days 0, 7) and 4IDx1 (4x0.1 ml on day 0). The 4IDx1 is a non-standard schedule that has been previously explored in research settings, but not endorsed by WHO for PrEP. Antibody titres of ≥0.5 IU/ml were considered seropositive. The proportion seropositive after a primary course or post-booster was estimated for each schedule and age category. Predictors of seronegative status after a primary course were examined using multivariable logistic regression models.

RESULTS

Overall, 835 travellers (median age 37.5 years; 37.1% > 50 years) were included in the analyses of seropositivity after a primary course. Another group of 771 travellers (median age 45.9 years; 43.5% > 50 years) was included in the analyses of seropositivity post-booster. The proportion seropositive after primary course was 92.5% (95%CI: 90.5-94.1%) and highest with the 1IDx3 schedule (93.4%; 95%CI: 91.4-95.0%). After adjusting for age and timing of the serology, the odds of seronegative status were four times higher (OR 4.17; 95%CI: 1.43-12.18) with the 4IDx1 schedule compared to 1IDx3. Overall, 98.7% (95%CI: 97.6-99.3%) were seropositive post-booster. Of 46 travellers who received a booster ≥3 years after PrEP, all were seropositive post-booster.

CONCLUSIONS

In older travellers, the 1IDx3 schedule was the most effective, and a high proportion were seropositive post-booster even many years after a primary course.

Genetic epidemiology of lymphatic filariasis in American Samoa after mass drug administration

Over 892 million people in 48 countries are at risk of infection by nematodes that cause lymphatic filariasis. As part of the Global Programme to Eliminate Lymphatic Filariasis, mass drug administration is distributed to communities until surveillance indicates infection rates are below target prevalence thresholds. In some countries, including American Samoa, lymphatic filariasis transmission persists despite years of mass drug administration and/or has resurged after cessation. Nothing is known about the population genetics of Wuchereria bancrofti worms in Polynesia, or whether local transmission is persisting and/or increasing due to inadequate mass drug administration coverage, expansion from residual hotspots, reintroduction from elsewhere, or a combination. We extracted DNA from microfilariae on blood slides collected during prevalence surveys in 2014 and 2016, comprising 31 pools of five microfilariae from 22 persons living in eight villages. We sequenced 1104 bp across three mitochondrial markers (ND4, COI, CYTB). We quantified parasite genetic differentiation using variant calls and estimated haplotypes using principal components analysis, F-statistics, and haplotype networks. Of the variants called, all but eight were shared across the main island of Tutuila, and three of those were from a previously described hotspot village, Fagali'i. Genotypic data did not support population genetic structure among regions or villages in 2016, although differences were observed between worms collected in Fagali'i in 2014 and those from 2016. Because estimated haplotype frequency varied between villages, these statistics suggested genetic differentiation, but were not consistent among villages. Finally, haplotype networks demonstrated American Samoan sequence clusters were related to previously published sequences from Papua New Guinea. These are, to our knowledge, the first reports of W. bancrofti genetic variation in Polynesia. The resurgent parasites circulating on the main island of American Samoa represent a single population. This study is the first step towards investigating how parasite population structure might inform strategies to manage resurgence and elimination of lymphatic filariasis.

Influence of climate variables on the rising incidence of nontuberculous mycobacterial (NTM) infections in Queensland, Australia 2001-2016

International reports indicate a rising incidence of nontuberculous mycobacterial (NTM) disease. Many infectious diseases have seasonal variation in incidence, and major weather events and climate change have been implicated. The aim of this study was to explore the relationship between climate variables and NTM incident cases in Queensland, Australia.

METHODS

NTM data were obtained from the Queensland notifiable conditions database for the period 2001-2016. Rainfall and temperature data were obtained from the Australian Bureau of Meteorology. Poisson regression models were used to assess notification rates (incidence cases per 100,000 population) over time and to estimate incidence rate ratios (IRR). Cross correlation coefficients were used to examine the relationship between rainfall and temperature data and NTM incidence over time in each Hospital and Health Service (HHS).

RESULTS

12,219 NTM cases were reported. The most common species was M. intracellulare (39.1%), followed by M. avium (9.8%), M abscessus (8.5%), M. fortuitum (8.3%), M. chelonae (3.3%), and M. kansasii (2.4%). The estimated incidence rate increased from 11.10 (95% CI 8.10-15.22) in 2001 to 25.88 (95%CI 21.78-30.73) per 100,000 in 2016. The estimated IRR increased for all common species, except M. kansasii. Although increased IRRs were observed for most NTM species, geospatial heterogeneity was observed. The effect of rainfall and temperature on NTM incidence differed between species and geographic regions.

CONCLUSIONS

The incidence of NTM infections increased between 2001 and 2016. Variations in temperature and rainfall may play a role in environmental exposure to some species of NTM. Spatial variation in IRR suggests that there may also be other environmental factors that influence transmission.

Emergence and spread of ciprofloxacin-resistant Neisseria gonorrhoeae in New South Wales, Australia: lessons from history

OBJECTIVES

Our aim was to investigate the emergence and spread of ciprofloxacin resistance in clinical Neisseria gonorrhoeae isolates in New South Wales, Australia, from the first reported case in 1991 until ciprofloxacin resistance was sustained at or above the WHO threshold for treatment change of 5% (1999), to inform future strategies for controlling gonococcal antimicrobial resistance.

METHODS

The index isolate and all subsequent clinical isolates of ciprofloxacin-resistant N. gonorrhoeae in New South Wales from 1991 to 1999 were genotyped using a previously described method on the Agena MassARRAY iPLEX platform. Region of acquisition data, where available, were used to determine whether cases were travel associated.

RESULTS

In New South Wales, of the 325 ciprofloxacin-resistant N. gonorrhoeae isolates reported from 1991 to 1999, 98% (320/325) were able to be recovered and 100% (320/320) were genotyped. There were 66 different genotypes, comprising 1-99 isolates each. Notably no single clone was found to account for ciprofloxacin resistance being sustained in the population, with considerable variability in genotype prevalence observed throughout the study period. A total of 65% (209/320) of genotyped isolates had information regarding the likely place of acquisition; of these, 44% (93/209) were associated with overseas travel or sexual contact with an overseas visitor. The first ciprofloxacin-resistant N. gonorrhoeae in New South Wales was associated with travel to Thailand. Index cases of each resistant genotype were significantly more likely to have been acquired overseas (51.5%), predominantly in Asia (45%, 30/66).

CONCLUSIONS

The continued importation of multiple genotypes, rather than the expansion of a single genotype, led to ciprofloxacin-resistant N. gonorrhoeae being established in New South Wales.