Physiological responses of insular wild black rat (Rattus rattus) to natural infection by the digenean trematode Fasciola hepatica.

Wild black rat Rattus rattus is regularly infected by the liver fluke Fasciola hepatica on Corsica. This report constitutes the only example of a murid rodent that plays an important epidemiological role for the Fasciolosis. We investigated the influence of such unusual parasite infection on black rat physiology by measuring its oxygen consumption at different ambient temperatures. Black rat energy requirements are influenced by body mass, temperature of the experiment and parasite infestation. The influence of the presence of F. hepatica was more pronounced for cold temperatures. The mean increase of 56% in oxygen requirements for infected rats is extremely high, indeed unexpected, according to previous knowledge. These high physiological constraints may be explained by the recent confrontation of the digenean and the rodent.