Simulation of rain enhances horizontal transmission of the microsporidium Nosema lymantriae via infective feces

Abstract

Larvae of the gypsy moth, Lymantria dispar, infected with the microsporidium, Nosema lymantriae, release infective spores with feces. We tested the effects of simulated light rain on transmission in cages, providing random contamination of host plant foliage with feces. Contamination by larvae in the intermediate stage of infection, 15-16days post inoculation, entailed transmission to a mean 4.4-16.7% of test larvae. Simulated rain significantly increased transmission to 30.0-57.3%. Transmission success significantly increased with disease progress. Experiments demonstrated that feces are a suitable source of spores and a likely transmission pathway in the field.

Keywords: Disease transmission; Gypsy moth; Microsporidia; Nosema lymantriae; Precipitation.