Managing disease outbreaks: The importance of vector mobility and spatially heterogeneous control

This work is licensed under a Creative Commons Attribution 4.0 International License.Management strategies for control of vector-borne diseases, for example Zika or dengue, include using larvicide and/or adulticide, either through large-scale application by truck or plane or through door-to-door efforts that require obtaining permission to access private property and spray yards. The efficacy of the latter strategy is highly dependent on the compliance of local residents. Here we develop a model for vector-borne disease transmission between mosquitoes and humans in a neighborhood setting, considering a network of houses connected via nearest-neighbor mosquito movement. We incorporate large-scale application of adulticide via aerial spraying through a uniform increase in vector death rates in all sites, and door-to-door application of larval source reduction and adulticide through a decrease in vector emergence rates and an increase in vector death rates in compliant sites only, where control efficacies are directly connected to real-world experimentally measurable control parameters, application frequencies, and control costs. To develop mechanistic insight into the influence of vector motion and compliance clustering on disease controllability, we determine the basic reproduction number R0 for the system, provide analytic results for the extreme cases of no mosquito movement, infinite hopping rates, and utilize degenerate perturbation theory for the case of slow but non-zero hopping rates. We then determine the application frequencies required for each strategy (alone and combined) in order to reduce R0 to unity, along with the associated costs. Cost-optimal strategies are found to depend strongly on mosquito hopping rates, levels of door-to-door compliance, and spatial clustering of compliant houses, and can include aerial spray alone, door-to-door treatment alone, or a combination of both. The optimization scheme developed here provides a flexible tool for disease management planners which translates modeling results into actionable control advice adaptable to system-specific details.Simons Foundation (426126)University of Kansas General Research Grant (2301-2105075)Department of Defense SERDP contract (W912HQ-16-C-0054

Increase in West Nile Neuroinvasive Disease after Hurricane Katrina

After Hurricane Katrina, the number of reported cases of West Nile neuroinvasive disease (WNND) sharply increased in the hurricane-affected regions of Louisiana and Mississippi. In 2006, a >2-fold increase in WNND incidence was observed in the hurricane-affected areas than in previous years

Battle of the Bites: The Effect of Sewage Effluent Exposure on Mosquitofish Biocontrol of Mosquitoes in Residential Louisiana

Mosquitofish, Gambusia affinis, are eponymous larval mosquito predators. Their ability to colonize and survive in habitats that are uninhabitable by other potential predators allows them to naturally manage larval mosquito populations in most ground pools they are present in. However, effluent from residential onsite wastewater treatment systems (OWTSs) appears to limit the presence of fish predators. This is especially problematic in Louisiana, where regulations allow the discharge of OWTS effluent into open drainage conveyances. To determine the effect of effluent on the capacity of mosquitofish for biocontrol in contaminated areas, we assessed the body condition metrics of populations from two effluent-exposed sites and two sites not exposed to effluent, determined the lethal effect of effluent-contaminated drainage water on fish, and measured the prey consumption rates in the presence of effluent. Female fish collected from effluent-impacted sites had a reduced somatic body condition and most females examined displayed masculinized anal fins resembling the male gonopodium structure. This trait was not seen in fish collected from the control sites and has not yet been documented in association with OWTSs or in the state of Louisiana. Fish from the control sites survived at effluent-contaminated water levels < 70%, and the prey clearance rates increased with dilution. Onsite wastewater treatment system effluent has significant effects on both the short- and long-term persistence of mosquitofish, their body composition, reproductive health, and larval mosquito consumption. These effects likely release mosquito larvae from suppression and may increase the threat of mosquito-transmitted pathogens in effluent-contaminated locations