Thursday, August 6, 2009

PS 66-110: Vector-borne diseases spread more quickly with increasing environmental temperature

Joshua P. Hecker and Melanie E. Moses. University of New Mexico

Background/Question/Methods   

Predicting the spread of vector-borne pathogens such as West Nile Virus (WNV) requires estimating characteristics of the mosquito vector, the pathogen and the hosts. This work focuses on estimating the length of the vector reproduction cycle, vector lifespan, and viral growth rate as a function of environmental temperature. These estimates are incorporated into a Susceptible Infected Recovered (SIR) model to predict how rates of disease spread depend on temperature. Previous research shows that temperature affects all three parameters. In this poster we use data from the literature to quantify the relationship between temperature and vector reproductive rate, vector lifespan, and viral growth rate in the vector. We determine whether these three processes have similar dependence on temperature and whether that dependency is consistent with predictions of the Metabolic Theory of Ecology (MTE).
Results/Conclusions   

We compared the natural log of time to complete a reproductive cycle, lifespan and time for the vector to become infective to environmental temperature. Preliminary results show a strong linear relationship in all three cases, consistent with MTE predictions. Specifically, we observe an approximate 5-fold decrease in all three times as temperature increases from 18 to 32 C. When these results are incorporated into an SIR model, it predicts that a given population size of vectors would transmit WNV 5 times faster as environmental temperature increases over this range. This result has important implications for how rapidly vector-borne diseases spread given increases in environmental temperature due to climate change.