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Bret D Elderd, James R Reilly
While rising global temperatures are increasingly affecting both species and their biotic interactions, the debate about whether global warming will increase or decrease disease transmission between individuals remains far from resolved. This may stem from the lack of empirical data. Using a tractable and easily manipulated insect host-pathogen system, we conducted a series of field and laboratory experiments to examine how increased temperatures affect disease transmission using the crop-defoliating pest, the fall armyworm (Spodoptera frugiperda) and its species-specific baculovirus, which causes a fatal infection...
July 2014: Journal of Animal Ecology
Bret D Elderd, Greg Dwyer, Vanja Dukic
Estimates of a disease's basic reproductive rate R0 play a central role in understanding outbreaks and planning intervention strategies. In many calculations of R0, a simplifying assumption is that different host populations have effectively identical transmission rates. This assumption can lead to an underestimate of the overall uncertainty associated with R0, which, due to the non-linearity of epidemic processes, may result in a mis-estimate of epidemic intensity and miscalculated expenditures associated with public-health interventions...
September 2013: Epidemics
Bret D Elderd, Brian J Rehill, Kyle J Haynes, Greg Dwyer
Cyclic outbreaks of defoliating insects devastate forests, but their causes are poorly understood. Outbreak cycles are often assumed to be driven by density-dependent mortality due to natural enemies, because pathogens and predators cause high mortality and because natural-enemy models reproduce fluctuations in defoliation data. The role of induced defenses is in contrast often dismissed, because toxic effects of defenses are often weak and because induced-defense models explain defoliation data no better than natural-enemy models...
September 10, 2013: Proceedings of the National Academy of Sciences of the United States of America
Bret D Elderd
No abstract text is available yet for this article.
June 2013: PLoS Pathogens
Emma Fuller, Bret D Elderd, Greg Dwyer
Classical epidemic theory focuses on directly transmitted pathogens, but many pathogens are instead transmitted when hosts encounter infectious particles. Theory has shown that for such diseases pathogen persistence time in the environment can strongly affect disease dynamics, but estimates of persistence time, and consequently tests of the theory, are extremely rare. We consider the consequences of persistence time for the dynamics of the gypsy moth baculovirus, a pathogen transmitted when larvae consume foliage contaminated with particles released from infectious cadavers...
March 2012: American Naturalist
Benjamin J Parker, Bret D Elderd, Greg Dwyer
1. Studies of variability in host resistance to disease generally emphasize variability in susceptibility given exposure, neglecting the possibility that hosts may vary in behaviours that affect the risk of exposure. 2. In many insects, horizontal transmission of baculoviruses occurs when larvae consume foliage contaminated by the cadavers of virus-infected conspecific larvae; so, host behaviour may have a strong effect on the risk of infection. 3. We studied variability in the behaviour of gypsy moth (Lymantria dispar) larvae, which are able to detect and avoid virus-contaminated foliage...
July 2010: Journal of Animal Ecology
Bret D Elderd, Jonathan Dushoff, Greg Dwyer
The theory of insect population dynamics has shown that heterogeneity in natural-enemy attack rates is strongly stabilizing. We tested the usefulness of this theory for outbreaking insects, many of which are attacked by infectious pathogens. We measured heterogeneity among gypsy moth larvae in their risk of infection with a nucleopolyhedrovirus, which is effectively heterogeneity in the pathogen's attack rate. Our data show that heterogeneity in infection risk in this insect is so high that it leads to a stable equilibrium in the models, which is inconsistent with the outbreaks seen in North American gypsy moth populations...
December 2008: American Naturalist
Bret D Elderd, Vanja M Dukic, Greg Dwyer
Concerns over bioterrorism and emerging diseases have led to the widespread use of epidemic models for evaluating public health strategies. Partly because epidemic models often capture the dynamics of prior epidemics remarkably well, little attention has been paid to how uncertainty in parameter estimates might affect model predictions. To understand such effects, we used Bayesian statistics to rigorously estimate the uncertainty in the parameters of an epidemic model, focusing on smallpox bioterrorism. We then used a vaccination model to translate the uncertainty in the model parameters into uncertainty in which of two vaccination strategies would provide a better response to bioterrorism, mass vaccination, or vaccination of social contacts, so-called "trace vaccination...
October 17, 2006: Proceedings of the National Academy of Sciences of the United States of America
Bret D Elderd
Disturbances, such as flooding, play important roles in determining community structure. Most studies of disturbances focus on the direct effects and, hence, the indirect effects of disturbances are poorly understood. Within terrestrial riparian areas, annual flooding leads to differences in the arthropod community as compared to non-flooded areas. In turn, these differences are likely to alter the survival, growth, and reproduction of plant species via an indirect effect of flooding (i.e., changes in herbivory patterns)...
March 2006: Oecologia
D G MacKay, L Abrams, M J Pedroza
This experiment tested for age-linked asymmetries predicted under Node Structure theory (NST; D. G. MacKay & D. M. Burke, 1990) between detecting versus retrieving orthographic information. Older adults detected that briefly presented words were correctly spelled (e.g., endeavor) or misspelled (e.g., endeavuor) as readily as did young adults. However, they were less able than young adults to retrieve the correctly and incorrectly spelled words that they had seen. These age-linked asymmetries were not due to educational factors, stimulus characteristics, sensory-level factors, task complexity, floor or ceiling effects, general slowing, or cohort-related activities, but they were consistent with NST predictions and with similar asymmetries in a wide range of other studies...
March 1999: Psychology and Aging
Beissinger, Tygielski, Elderd
We examined whether the early onset of incubation serves to protect eggs from the dangers imposed by conspecifics in the green-rumped parrotlet, Forpus passerinus, a small neotropical parrot that lays a large clutch and begins incubation on the first egg. Nestboxes with eggs were installed and their fate was followed for 72 h to determine whether egg destruction and nest site take-overs occurred as predicted by the Egg Protection and Limited Breeding Opportunities Hypotheses, or whether additional eggs appeared in the boxes as predicted by the Brood Parasitism Hypothesis...
January 1998: Animal Behaviour
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