Factors affecting Dirofilaria immitis prevalence in red foxes in northeastern Spain

We determined the prevalence of Dirofilaria immitis (Nematoda, Filariidae) among 433 red foxes (Vulpes vulpes) in northeastern Spain, between 1990 and 1992. Forty-six (11%) of 433 foxes were infected; the intensity ranged from 1 to 36 (mean +/- SE; 4.39 +/- 0.92) nematodes per host. The prevalence of D. immitis was higher in foxes inhabiting riparian zones of the study area. This population has a very high juvenile/adult ratio. Heartworm prevalences did not differ among host sex, weight, or fat condition categories.