Assessment of synthetic floral-based attractants and sugar baits to capture male and female Aedes aegypti (Diptera: Culicidae).

BACKGROUND: The viruses transmitted by Aedes aegypti, including dengue and Zika viruses, are rapidly expanding in geographic range and as a threat to public health. In response, control programs are increasingly turning to the use of sterile insect techniques resulting in a need to trap male Ae. aegypti to monitor the efficacy of the intervention. However, there is a lack of effective and cheap methods for trapping males. Thus, we attempted to exploit the physiological need to obtain energy from sugar feeding in order to passively capture male and female Ae. aegypti (nulliparous and gravid) in free-flight attraction assays. Candidate lures included previously identified floral-based (phenylacetaldehyde, linalool oxide, phenylethyl alcohol, and acetophenone) attractants and an attractive toxic sugar bait-based (ATSB) solution of guava and mango nectars. A free-flight attraction assay assessed the number of mosquitoes attracted to each candidate lure displayed individually. Then, a choice test was performed between the best-performing lure and a water control displayed in Gravid Aedes Traps (GAT). RESULTS: Results from the attraction assays indicated that the ATSB solution of guava and mango nectars was the most promising lure candidate for males; unlike the floral-based attractants tested, it performed significantly better than the water control. Nulliparous and gravid females demonstrated no preference among the lures and water controls indicating a lack of attraction to floral-based attractants and sugar baits in a larger setting. Although the guava-mango ATSB lure was moderately attractive to males when presented directly (i.e. no need to enter a trap or other confinement), it failed to attract significantly more male, nulliparous female, or gravid female Ae. aegypti than water controls when presented inside a Gravid Aedes Trap. CONCLUSIONS: Our findings suggest that the use of volatile floral-based attractants and sugar mixtures that have been identified in the literature is not an effective lure by which to kill Ae. aegypti at ATSB stations nor capture them in the GAT. Future trapping efforts would likely be more successful if focused on more promising methods for capturing male and female Ae. aegypti.

A Cost-Effectiveness Tool for Informing Policies on Zika Virus Control.

BACKGROUND: As Zika virus continues to spread, decisions regarding resource allocations to control the outbreak underscore the need for a tool to weigh policies according to their cost and the health burden they could avert. For example, to combat the current Zika outbreak the US President requested the allocation of $1.8 billion from Congress in February 2016. METHODOLOGY/PRINCIPAL FINDINGS: Illustrated through an interactive tool, we evaluated how the number of Zika cases averted, the period during pregnancy in which Zika infection poses a risk of microcephaly, and probabilities of microcephaly and Guillain-Barré Syndrome (GBS) impact the cost at which an intervention is cost-effective. From Northeast Brazilian microcephaly incidence data, we estimated the probability of microcephaly in infants born to Zika-infected women (0.49% to 2.10%). We also estimated the probability of GBS arising from Zika infections in Brazil (0.02% to 0.06%) and Colombia (0.08%). We calculated that each microcephaly and GBS case incurs the loss of 29.95 DALYs and 1.25 DALYs per case, as well as direct medical costs for Latin America and the Caribbean of $91,102 and $28,818, respectively. We demonstrated the utility of our cost-effectiveness tool with examples evaluating funding commitments by Costa Rica and Brazil, the US presidential proposal, and the novel approach of genetically modified mosquitoes. Our analyses indicate that the commitments and the proposal are likely to be cost-effective, whereas the cost-effectiveness of genetically modified mosquitoes depends on the country of implementation. CONCLUSIONS/SIGNIFICANCE: Current estimates from our tool suggest that the health burden from microcephaly and GBS warrants substantial expenditures focused on Zika virus control. Our results justify the funding committed in Costa Rica and Brazil and many aspects of the budget outlined in the US president's proposal. As data continue to be collected, new parameter estimates can be customized in real-time within our user-friendly tool to provide updated estimates on cost-effectiveness of interventions and inform policy decisions in country-specific settings.

Geographic variation in the relationship between human Lyme disease incidence and density of infected host-seeking Ixodes scapularis nymphs in the Eastern United States.

Prevention and control of Lyme disease is difficult because of the complex biology of the pathogen's (Borrelia burgdorferi) vector (Ixodes scapularis) and multiple reservoir hosts with varying degrees of competence. Cost-effective implementation of tick- and host-targeted control methods requires an understanding of the relationship between pathogen prevalence in nymphs, nymph abundance, and incidence of human cases of Lyme disease. We quantified the relationship between estimated acarological risk and human incidence using county-level human case data and nymphal prevalence data from field-derived estimates in 36 eastern states. The estimated density of infected nymphs (mDIN) was significantly correlated with human incidence (r = 0.69). The relationship was strongest in high-prevalence areas, but it varied by region and state, partly because of the distribution of B. burgdorferi genotypes. More information is needed in several high-prevalence states before DIN can be used for cost-effectiveness analyses.

One Health approach to identify research needs in bovine and human babesioses: workshop report.

BACKGROUND: Babesia are emerging health threats to humans and animals in the United States. A collaborative effort of multiple disciplines to attain optimal health for people, animals and our environment, otherwise known as the One Health concept, was taken during a research workshop held in April 2009 to identify gaps in scientific knowledge regarding babesioses. The impetus for this analysis was the increased risk for outbreaks of bovine babesiosis, also known as Texas cattle fever, associated with the re-infestation of the U.S. by cattle fever ticks. RESULTS: The involvement of wildlife in the ecology of cattle fever ticks jeopardizes the ability of state and federal agencies to keep the national herd free of Texas cattle fever. Similarly, there has been a progressive increase in the number of cases of human babesiosis over the past 25 years due to an increase in the white-tailed deer population. Human babesiosis due to cattle-associated Babesia divergens and Babesia divergens-like organisms have begun to appear in residents of the United States. Research needs for human and bovine babesioses were identified and are presented herein. CONCLUSIONS: The translation of this research is expected to provide veterinary and public health systems with the tools to mitigate the impact of bovine and human babesioses. However, economic, political, and social commitments are urgently required, including increased national funding for animal and human Babesia research, to prevent the re-establishment of cattle fever ticks and the increasing problem of human babesiosis in the United States.

The United States Department of Agriculture's Northeast Area-wide Tick Control Project: summary and conclusions.

From 1997 to 2002, the U.S. Department of Agriculture's Northeast Area-wide Tick Control Project used acaricide-treated 4-Poster Deer Treatment Bait Stations in five eastern states to control ticks feeding on white-tailed deer. The objectives of this host-targeted technology were to reduce free-living blacklegged (Ixodes scapularis Say) and lone star (Amblyomma americanum [L.]) tick populations and thereby to reduce the risk of tick-borne disease. During 2002 to 2004, treatments were suspended, and tick population recovery rates were assayed. Subsequently, the major factors that influenced variations in efficacy were extrapolated to better understand and improve this technology. Treatments resulted in significant reductions in free-living populations of nymphal blacklegged ticks at six of the seven sites, and lone star ticks were significantly reduced at all three sites where they were present. During the study, maximal significant (p < or = 0.05) efficacies against nymphal blacklegged and lone star ticks at individual sites ranged from 60.0 to 81.7 and 90.9 to 99.5%, respectively. The major environmental factor that reduced efficacy was the occurrence of heavy acorn masts, which provided an alternative food resource for deer. Although the 4-Poster technology requires 1 or more years to show efficacy, this host-targeted intervention was demonstrated to be an efficacious, economical, safe, and environment-friendly alternative to area-wide spraying of acaricide to control free-living populations of these tick species.

A Bayesian hierarchical model for the estimation of two incomplete surveillance data sets.

A model-based approach to analyze two incomplete disease surveillance datasets is described. Such data typically consist of case counts, each originating from a specific geographical area. A Bayesian hierarchical model is proposed for estimating the total number of cases with disease while simultaneously adjusting for spatial variation. This approach explicitly accounts for model uncertainty and can make use of covariates.The method is applied to two surveillance datasets maintained by the Centers for Disease Control and Prevention on Rocky Mountain spotted fever (RMSF). An inference is drawn using Markov Chain Monte Carlo simulation techniques in a fully Bayesian framework. The central feature of the model is the ability to calculate and estimate the total number of cases and disease incidence for geographical regions where RMSF is endemic.The information generated by this model could significantly reduce the public health impact of RMSF and other vector-borne zoonoses, as well as other infectious or chronic diseases, by improving knowledge of the spatial distribution of disease risk of public health officials and medical practitioners. More accurate information on populations at high risk would focus attention and resources on specific areas, thereby reducing the morbidity and mortality caused by some of the preventable and treatable diseases.

The clinical assessment, treatment, and prevention of lyme disease, human granulocytic anaplasmosis, and babesiosis: clinical practice guidelines by the Infectious Diseases Society of America.

Evidence-based guidelines for the management of patients with Lyme disease, human granulocytic anaplasmosis (formerly known as human granulocytic ehrlichiosis), and babesiosis were prepared by an expert panel of the Infectious Diseases Society of America. These updated guidelines replace the previous treatment guidelines published in 2000 (Clin Infect Dis 2000; 31[Suppl 1]:1-14). The guidelines are intended for use by health care providers who care for patients who either have these infections or may be at risk for them. For each of these Ixodes tickborne infections, information is provided about prevention, epidemiology, clinical manifestations, diagnosis, and treatment. Tables list the doses and durations of antimicrobial therapy recommended for treatment and prevention of Lyme disease and provide a partial list of therapies to be avoided. A definition of post-Lyme disease syndrome is proposed.

Spatial analysis of West Nile virus: rapid risk assessment of an introduced vector-borne zoonosis.

The distribution of human risk for West Nile virus was determined by spatial analysis of the initial case distribution for the New York City area in 1999 using remote sensing and geographic information system technologies. Cluster analysis revealed the presence of a statistically significant grouping of cases, which also indicates the area of probable virus introduction. Within the cluster, habitat suitability for potentially infective adult mosquitoes was measured by the amount of vegetation cover using satellite imagery. Logistic regression analysis revealed satellite-derived vegetation abundance to be significantly and positively associated with the presence of human cases. The logistic model was used to estimate the spatial distribution of human risk for West Nile virus throughout New York City. Accuracy of the resulting risk map was cross-validated using virus-positive mosquito sample sites. These new epidemiological methods aid in rapid entry point identification and spatial prediction of human risk of infection for introduced vector-borne pathogens.