Mild energy restriction alters mouse–nematode transmission dynamics in free-running indoor arenas

Abstract

Energy restriction reduces Heligmosomoides polygyrus (Dujardin, 1845) (Nematoda) infection by reducing transmission-related behaviours but prolongs parasite survival by suppressing immune responses in individually housed mice. To determine the relative importance of these two processes in accumulation of worms in mouse populations, 10 female CD1 mice were housed in each of eight indoor arenas with ad libitum access to either an energy-sufficient (ES) diet or an energy-restricted (ER) diet with 20% less metabolizable energy (four arenas per diet). After 3 weeks, H. polygyrus transmission was initiated by introducing larvae onto damp peat trays. Mice adapted to the ER diet through increased food intake and nesting and reduced overall activity; after 6 weeks, nutritional and immunological measures were comparable between diet groups. With continuing exposure to parasite larvae, mice in both ER and ES arenas developed resistance to the incoming larvae; however, mice in the ER arenas accumulated lower worm burdens than mice in the ES arenas despite their increased contact with peat. We suggest that the comparable immunocompetence of mice in the ER and ES arenas enabled the ER mice exposed to higher transmission rates to more rapidly reject the parasites, leading to lower final worm numbers, a pattern frequently observed in other helminth infections.