A Model of the Transmission of Dengue Fever with an Evaluation of the Impact of Ultra-Low Volume (ULV) Insecticide Applications on Dengue Epidemics

Abstract

We have developed a deterministic susceptible, exposed, infectious, resistant or removed (SEIR) model of dengue fever transmission that enables us to explore the behavior of an epidemic, and to experiment with vector control practices. Populations of both host and vector are divided into compartments representing disease status (susceptible, exposed, infectious, and, for humans, resistant), and the flow between compartments is described by differential equations. Examination of the equilibrium points leads to a formulation of the basic reproduction rate (z 0 ) of the disease. With a base set of parameters, z 0 = 1.9 and the model realistically reproduces epidemic transmission in an immunologically naive population. Control of adult mosquitoes by ultra-low volume (ULV) aerosols is simulated by an abrupt decrease in vector densities, followed by gradual recovery of the vector population. The model indicates that ULV has little impact on disease incidence, even when multiple applications are made, although the peak of the epidemic may be delayed. Decreasing the carrying capacity of the environment for mosquitoes, and thus the basic reproduction rate of the disease, by source reduction or other means, is more effective in reducing transmission.

High potential risk of dengue transmission during the hot-dry season in Nha Trang City, Vietnam

“…3). The number of dengue cases does not increase at the beginning of the high-temperature period in the city (May and June); however, previous studies have reported that dengue epidemics take several months to reach a level where they can be recognized as the result of previous conditions (Guzman et al, 2000;Newton et al, 1992). Our results indicated that an extensive reduction in and the management of Ae.…”

Hot temperatures can force delayed mosquito outbreaks via sequential changes in Aedes aegypti demographic parameters in autocorrelated environments

“…In fact, it could be argued that insect outbreaks have underpinned the wider ecological discussion on whether populations undergo density dependent-regulation (Chaves & Koenraadt 2010;Nicholson 1958). In the applied context of disease control, vector outbreaks are of major importance given density-dependence implications for different control measures, such as larviciding (Agudelo-Silva & Spielman 1984;Wilson et al 1990), insecticide spraying (Newton & Reiter 1992;Oki et al 2011), and more recently, the field release of genetically modified mosquitoes (Legros et al 2009;Magori et al 2009). …”

Dengue and Dengue Hemorrhagic Fever

“…Prevention and control of dengue and DHF currently depends on controlling the mosquito vector, A. aegypti, in and around the home, where most transmission occurs. Space sprays with insecticides to kill adult mosquitoes are not usually effective (38,107,115) unless they are used indoors. The most effective way to control the mosquitoes that transmit dengue is larval source reduction, i.e., elimination or cleaning of water-holding containers that serve as the larval habitats for A. aegypti in the domestic environment (38,115,137).…”