Epidemiology of Toxocara canis in red foxes (Vulpes vulpes) from urban areas of Bristol.

A descriptive epidemiological survey was undertaken of the ascarid nematode Toxocara canis in 521 red foxes (Vulpes vulpes) during the period January 1986 to July 1990. Age-prevalence and age-intensity profiles show that worm burdens are significantly higher in cubs than in subadult or adult foxes and higher in subadult than in adult foxes. Seasonal variations in worm burdens occur, with the highest prevalences and intensities being found during the spring, when cubs are born, and in the summer months. Prevalences and intensities then decrease during the autumn and winter months in both subadult and adult foxes, but, during this period, prevalences are significantly higher in male than in female foxes. Variations in worm burdens in the fox population are likely to be related to the reproductive cycle of the fox, with a high proportion of cubs becoming infected in utero. The role of the fox in the transmission of T. canis in the urban environment is discussed.