A real-time search strategy for finding urban disease vector infestations

Abstract

Containing domestic vector infestation requires the ability to swiftly locate and treat infested homes. In urban settings where vectors are heterogeneously distributed throughout a dense housing matrix, the task of locating infestations can be challenging. Here, we present a novel stochastic compartmental model developed to help locate infested homes in urban areas. We designed the model using infestation data for the Chagas disease vector species Triatoma infestans in Arequipa, Peru. Our approach incorporates disease vector counts at each observed house, and the vector's complex spatial dispersal dynamics. We used a Bayesian method to augment the observed data, estimate the insect population growth and dispersal parameters, and determine posterior infestation probabilities of households. We investigated the properties of the model through simulation studies, followed by field testing in Arequipa. Simulation studies showed the model to be accurate in its estimates of two parameters of interest: the growth rate of a domestic triatomine bug colony and the probability of a triatomine bug successfully invading a new home after dispersing from an infested home. When testing the model in the field, data collection using model estimates was hindered by low household participation rates, which severely limited the algorithm and in turn, the model's predictive power. While future optimization efforts must improve the model's capabilities when household participation is low, our approach is nonetheless an important step toward integrating data with predictive modeling to carry out evidence-based vector surveillance in cities.Controlling the spread of disease vectors in real time requires locating and treating 2 infested households before the vectors infest other houses. Vector-borne epidemics 3 increasingly occur in cities worldwide, and detecting populations of disease vectors in 4 large urban environments is especially complex [1,2]. In order to manage factors that 5 are unique to a metropolis such as contiguous and dense housing, patchy vector 6 distribution, and urban sprawl, vector detection methods must be tailored for cities. 7In the city of Arequipa, Peru, the ministry of health is nearing the end of a 8 campaign to eliminate Triatoma infestans, the local vector species of Trypanosoma 9 cruzi. The parasite is the etiological agent of Chagas disease, a chronic condition that 10 can lead to serious gastrointestinal and cardiac complications. In the T. infestans 11 elimination campaign, over 70,000 households were treated with insecticide during the 12 'attack' phase of this effort, and are now in a community-based surveillance phase. In 13 this phase, residents are encouraged to report suspected T. infestans infestations, which 14 are then verified by a trained entomological inspector. If T. infestans are found in or 15 around the home, the area will be treated with insecticide, along with all neighboring 16 homes. To complement the community based efforts, trained vector control personnel 17 also proactively inspect...