Costs of bot fly infection in white-footed mice: energy and mass flow
We quantified the impact of bot fly larvae (Cuterebra fontinella) on the energy budget of their small-mammal hosts (white-footed mice, Peromyscus leucopus). We estimated the fluxes of water from the host to the parasite and from the parasite to the host by injecting infected hosts (or bot fly larvae) with tritiated water and measuring the uptake by the parasite (or the host). Using these fluxes, we then constructed a fluid flux budget for the host–parasite system, and estimated that a bot fly larva receives ca. 1% of the host's nutrient budget. We also found a 5% increase in the metabolic rate of infected hosts in the laboratory, but no such effect in the field. No effect of bot fly larvae on digestive efficiency or food consumption was detected; however, infected mice lost body mass during a field trial. We conclude that bot fly larvae have a relatively modest effect, although energetically stressed individuals, such as lactating females, could suffer substantially.