Microsporidia transmission in forest Lepidoptera

The impact of microsporidian infections on the population dynamics of forest insects is still not fully understood. Transmission is a key process in the interactions between insect pathogens and their hosts. Moreover, a detailed understanding of transmission is crucial when these pathogens are considered for use in biological control programs. The pathology of a microsporidiosis, as characterized by the life cycle, tissue specificity and virulence of the invading organism, cannot be interpreted without considering transmission. Different disease characteristics should affect key mechanisms for pathogen transmission. We propose to use gypsy moth, Lymantria dispar and three of its microsporidian pathogens, namely Vairimorpha sp., Nosema lymantriae, and Endoreticulatus schubergi as a model system to determine how microsporidia of terrestrial hosts are transmitted. These microsporidia utilize different host tissues for their reproduction and are hypothesized to utilize distinctly different transmission pathways. The study will produce experimental data on the role of feces, silk, and cadavers of infected hosts in the transmission of the three microsporidia. All potential mechanisms of spore release will be quantified for the three species. To assess the ability of the pathogens to persist in a population over several host generations, we propose to determine whether vertical transmission is involved as well as evaluate the capability of spores to survive winter conditions. The new, quantitative data will be used to improve a mathematical model that has been developed to describe horizontal transmission of another, closely related Nosema isolate in L. dispar. The model will also be adapted to explain the presumably different transmission mechanisms in Vairimorpha and Endoreticulatus. With the comparative, experimental work outlined in this proposal we may achieve the first detailed description of transmission of three microsporidia in the context of the distinct life histories of the pathogens in a forest lepidopteran model system.

The impact of microsporidian infections on the population dynamics of forest insects is still not fully understood. Transmission is a key process in the interactions between insect pathogens and their hosts. Moreover, a detailed understanding of transmission is crucial when these pathogens are considered for use in biological control programs. The pathology of a microsporidiosis, as characterized by the life cycle, tissue specificity and virulence of the invading organism, cannot be interpreted without considering transmission. Different disease characteristics should affect key mechanisms for pathogen transmission. We propose to use gypsy moth, Lymantria dispar and three of its microsporidian pathogens, namely Vairimorpha sp., Nosema lymantriae, and Endoreticulatus schubergi as a model system to determine how microsporidia of terrestrial hosts are transmitted. These microsporidia utilize different host tissues for their reproduction and are hypothesized to utilize distinctly different transmission pathways. The study will produce experimental data on the role of feces, silk, and cadavers of infected hosts in the transmission of the three microsporidia. All potential mechanisms of spore release will be quantified for the three species. To assess the ability of the pathogens to persist in a population over several host generations, we propose to determine whether vertical transmission is involved as well as evaluate the capability of spores to survive winter conditions. The new, quantitative data will be used to improve a mathematical model that has been developed to describe horizontal transmission of another, closely related Nosema isolate in L. dispar. The model will also be adapted to explain the presumably different transmission mechanisms in Vairimorpha and Endoreticulatus. With the comparative, experimental work outlined in this proposal we may achieve the first detailed description of transmission of three microsporidia in the context of the distinct life histories of the pathogens in a forest lepidopteran model system.