Land-use and altitude-dependent prevalence rates of Angiostrongylus vasorum and other parasites of red foxes (Vulpes vulpes)

In view of the role of foxes as a reservoir for Angiostrongylus vasorum , a cardiopulmonary nematode of dogs and foxes, its occurrence across Switzerland was examined by using a standardised sampling scheme for fox faecal samples. In 72 study areas consisting of three one square km grid cells, a total of 1481 samples were collected by walking transects following linear features in the terrain and analysed by a flotation-sieving method. The overall prevalence rate of A. vasorum in faecal samples was 8.8% (95% Confidence Interval, CI: 7.4-10.3%), being significantly higher in the Swiss Plateau (11.4%, CI: 9.4-13.8%) and in areas with less than 50% of cultivated land (p=0.043). Prevalence rates decreased with increasing altitudes being significantly higher below 400 m above sea level (20.6%, 95% CI: 15.2-26.9%), while all samples collected above 900 m asl were negative. Eggs of Toxocara sp. (12.1%) , Taeniidae (10.5%), Capillaria spp. (8.3%), Trichuris vulpis (5.5%) , hookworms (5.3%), Toxascaris (1.3%) , Strongyloides spp. (0.4%) were also identified. Taeniid eggs were positively and Capillaria spp. negatively associated with the portion of cultivated land. The grid-cell based sampling scheme with replicable transects for fox faeces collection proved to be a suitable, non-invasive method for large-scale parasite surveys providing information on the relative infectious pressure for the local dog population. Abstract In view of the role of foxes as a reservoir for Angiostrongylus vasorum , a nematode of the heart and lungs of dogs and foxes, its occurrence across Switzerland was investigated in foxes applying a standardized sampling scheme for fox faecal samples. In 72 study areas, which consisted of three one square km grid cells, a total of 1481 samples were collected by walking transects following linear features in the terrain and analysed by a flotation-sieving method. The overall prevalence rate of A. vasorum in faecal samples was 8.8% (95% Confidence Interval, CI: 7.4-10.3%), being significantly higher in the Swiss Plateau (11.4%, CI. 9.4-13.8%) compared to other bioregions, and more prevalent in areas with less than 50% of cultivated land (p=0.043). Prevalence rates increased with decreasing altitudes being significantly higher below 400 m above sea level (20.6%, 95% CI: 15.2-26.9%), while all samples collected above 900 m asl were negative. Eggs of Toxocara sp. (12.1%) , Taeniidae (10.5%), Capillaria spp. (8.3%), Trichuris vulpis (5.5%) , hookworms (5.3%), Toxascaris leonina (1.3%) and Strongyloides sp. (0.4%) were furthermore identified. Taeniid eggs were positively and Capillaria spp. negatively associated with the amount of cultivated land. The prevalence rates based on our faecal analyses were generally lower compared to previous studies from Switzerland which were based on fox necropsies. However, the grid-cell based sampling scheme with replicable transects for fox faeces collection proved to be a suitable, non-invasive method for parasitic large-scale surveys providing information on the relative infectious pressure for the local dog population. allowing the detection of endoparasites. The aim of this study was to investigate the large-scale distribution of A. vasorum and other helminths in the Swiss fox population, to identify environmental factors enhancing their presence and therewith to assess the threat of infection for the Swiss dog population.