Energy deficiency alters behaviours involved in transmission ofHeligmosomoides polygyrus(Nematoda) in mice

Abstract

Independent studies have shown that animal behaviour is affected by nutritional deficiency and that host behaviour influences parasite transmission. The objectives of this study were to determine whether energy deficiency alters the behaviour profile of mice and the rate of exposure of mice to naturally acquired Heligmosomoides polygyrus (Nematoda) larvae. Outbred CF-1 and CD-1 female mice were fed either a control or an energy-deficient (65% of control) diet for 7 days, after which time, the mice fed the deficient diet had consumed signficantly less energy, had lower rectal temperatures, and lower masses (CD-1 mice only) compared with control mice. On day 7, mice were placed individually in natural transmission arenas containing damp peat moss and parasite larvae for 6 h, during which time, each mouse was observed 60 times and her behaviour recorded. All mice were then returned to standard caging and fed the energy-sufficient diets to eliminate confounding effects of energy deficiency on the host immune response over the following 8 days. At necropsy, parasite numbers were significantly lower in the energy-deficient mice of both strains. The behaviour profile differed significantly between diet groups and between strains; deficient mice of both strains groomed less and dug in the peat substrate less than control mice. The frequency of grooming was positively correlated with worm burden in both strains, the frequency of mouthing the peat moss and of sleeping were positively associated with worm burden in CD-1 mice, and the frequency of standing and walking low was positively associated with worm burden in CF-1 mice. These results indicate that grooming and contact with the peat moss are important behaviours in transmission of H. polygyrus, that energy deficiency causes a decrease in the frequency of these behaviours, and that these behavioural changes may contribute to reduced parasite transmission in mice fed the energy-restricted diet.