VECTOR FITNESS AS A FUNCTION OF INFECTIVITY STATUS ALTERS DISEASE DYNAMICS.

Authors: Sisterson, Mark; Chen, Jianchi

Submitted to: American Phytopathological Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/16/2006
Publication Date: 6/1/2006
Citation: Sisterson, M.S., Chen, J. 2006. Vector Fitness as a Function of Infectivity Status Alters Disease Dynamics. Phytopathology 96:S108.

Interpretive Summary:

Technical Abstract: The spread of insect vectored plant pathogens is highly dependent on the population dynamics of the vector. Epidemiology models typically assume that the birth and death rates of pathogen-free and inoculative vectors are equal. However, empirical evidence indicates that in many cases birth and/or death rates of pathogen-free and inoculative vectors differ due to direct or indirect effects of the plant pathogen. Here a series of simple and general epidemiology models were used to determine how differences in birth and death rates of vectors based on their infectivity status influence disease dynamics. With unequal death rates of pathogen-free and inoculative vectors, the death rate of pathogen-free vectors was more important in determining total vector density than the death rate of inoculative vectors. Thus, increasing the death rate of pathogen-free vectors reduced the proportion of plants infected as vector density was reduced. Increasing the death rate of inoculative vectors also reduced the proportion of plants infected. However, as the death rate of inoculative vectors did not influence total vector density, the mechanism by which this effect occurred differed from that of pathogen-free vectors. In the case of inoculative vectors, increasing their death rate increased the rate at which inoculative vectors were replaced by pathogen-free vectors, thereby reducing the proportion of vectors which were inoculative and in turn the proportion of plants infected. With unequal birth rates, variation in the birth rate of inoculative vectors had little influence on the proportion of plants infected provided that the birth rate of pathogen-free vectors was much greater than their death rate. However, when the birth rate of pathogen-free vectors was only slightly greater than their death rate, large increases in the birth rate of inoculative vectors increased total vector density and in turn the proportion of infected plants. The results indicate that assumptions about the birth and death rates of vectors based on infectivity status can alter expected level of disease incidence.