Conquering Switzerland: the emergence ofAngiostrongylus vasorumin foxes over three decades and its rapid regional increase in prevalence contrast with the stable occurrence of lungworms

Angiostrongylus vasorum,Crenosoma vulpisandCapillaria aerophilaare the most common lungworms of domestic and wild canids. We investigated the short- and long-term lungworm prevalence changes in the Swiss fox population with a focus onA. vasorum. Between 2012 and 2017, lungs and hearts of 533 foxes from north-eastern Switzerland were necropsied and blood samples tested for circulatingA. vasorumantigen.Angiostrongylus vasorumprevalence increased steadily from 21.5% in 2012 to 81.8% in 2017. In contrast,C. aerophilaandC. vulpisprevalences fluctuated between 41.8 and 74.7%, and 3.6 and 14.9%, respectively. Based on 3955 blood samples collected between 1986 and 2017 from three geographic areas and during four time periods, antigen seropositivity increased from 2.4 to 62.0%. In north-eastern Switzerland, seropositivity was initially low (1.9 and 1.7% in the first two time periods) but increased in the following two decades to 22.2 and 62.0%, respectively. Our findings depict the spectacular expansion ofA. vasorumin the past three decades. Regionally, the prevalence in foxes increased 4-fold within 6 years in some regions. This underpins the important role of foxes as reservoir hosts, likely explaining the increasing number of cases of canine angiostrongylosis in Switzerland. Our findings are representative of central Europe and may help anticipating future developments in areas whereA. vasorumis present but (still) infrequent.