Models describing the transmission of vector-borne diseases are useful for identifying regions at risk of vector-borne disease transmission, predicting dynamics of disease epidemics, and determining effectiveness of control strategies. However, a potential problem with all of these models is that they are based on the unrealistic assumption that vectors experience a constant daily mortality rate, or in other words, that their probability of death does not change with age. Because vector mortality is the most sensitive component of these disease transmission models, assuming constant mortality could significantly affect the accuracy of model predictions. Therefore, we tested the assumption of constant mortality by recording the deaths of >100,000 laboratory reared Aedes aegypti. The resulting mortality pattern was age-dependent, with mortality rates increasing as mosquitoes aged. We used this mortality pattern along with several other standard mortality models to model the impact of different patterns of mortality on predicted pathogen transmission rates. We found that age-dependent mosquito mortality patterns impact transmission of mosquito-borne pathogens in three specific ways, by altering (1) population age structure, (2) survival through the extrinsic incubation period, and (3) life expectancy once infectious. These parameters significantly affect the ability of a mosquito population to transmit pathogens by determining (1) the proportion of older, potentially infectious mosquitoes in the population, (2) the percentage of mosquitoes that will survive long enough to become infectious and (3) the number of infectious bites mosquitoes are expected to take in their lifetime. Current models of vector-borne disease transmission that assume constant mortality ignore the complex interactions between mosquito age, mortality patterns, and pathogen transmission rates. Including age-dependent mortality patterns in these disease transmission models would lead to an improved understanding of pathogen transmission dynamics and significantly improve the accuracy of model predictions.
Species 1: Diptera Culicidae Aedes aegypti (yellow fever mosquito)
Keywords: mortality patterns, models
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA