Introduction of the rabbit flea, Spilopsyllus cuniculi (Dale), to a subantarctic island (Kerguelen Archipelago) and its assessment as a vector of myxomatosis

Introductions of the rabbit flea, Spilopsyllus cuniculi (Dale), were made on an island (3.1 km(2)) of the Kerguelen subantarctic archipelago in January and December 1987. Despite a small founding population, the species succeeded in establishing itself. Three years after introduction, the rate of spread was 614 +/- 133 m (between 1990 and 1993). Despite the subantarctic climate of Kerguelen, the burdens were similar to those noted in habitats favourable to this ectoparasite. The flea burden of adult rabbits after colonisation of the whole island was higher for pregnant females (182 +/- 21, n = 98) than for non-pregnant ones (85 +/- 16, n = 68) or males (20 +/- 3, n = 116). The circulation of myxoma virus, present on this island for several decades, has been favoured by the flea. As a result, the proportion of rabbits with antibodies rose from 34% before introduction of the flea to 85% in 1998. Moreover, the introduction of fleas has changed the relative proportions of both adult males and females with antibodies. Those proportions were not different before the introduction but more males than females showed antibodies when the flea colonised the whole island. Finally, the prospects of the introduction of Spilopsyllus cuniculi on the main island of the archipelago are discussed.