Re-Evaluation of a Hyperendemic Focus of Metastrongyloid Lungworm Infections in Gastropod Intermediate Hosts in Southern Germany

The metastrongyloid nematodes <i>Angiostrongylus vasorum</i>, <i>Aelurostrongylus abstrusus</i>, and <i>Crenosoma vulpis</i> can cause severe cardiopulmonary and respiratory symptoms in domestic dogs and cats and free-ranging canids and felids (e.g., foxes, wolves, wild cats, lynxes). Recent data on the prevalence of <i>A. vasorum</i> infections in dogs and foxes and on the prevalence of <i>Ae. abstrusus</i> and <i>Troglostrongylus brevior</i> infections in free-ranging lynxes and wild cats revealed several endemic and hyperendemic foci in Germany. Nonetheless, long-term investigations on the prevalence of metastrongyloid larvae infecting gastropod intermediate hosts are still scarce for Germany. To fill this gap, we conducted an epidemiological survey on native slugs and snails in a selected meadow close to Obrigheim, previously identified as a hyperendemic focus for canine angiostrongylosis. To re-evaluate this location as a 'hotspot' of canine angiostrongylosis, terrestrial slugs and snails (<i>n</i> = 533) were collected in all seasons, artificially digested, and microscopically and molecularly analyzed for the presence of metastrongyloid lungworm larvae. Here, the prevalence ranged greatly between seasons. In summer, 27.46% (59/215) of gastropods were infected with metastrongyloid larvae. In fall, the prevalence dropped to 10.00% (16/160) and lowest infection rates were observed in both winter (5.65%) and spring (1.47%). In total, <i>A. vasorum</i> was detected in 12.01% (64/533), <i>Crenosoma</i> sp. in 0.94% (5/533), and <i>Ae. abstrusus</i> in 0.38% (2/533) of gastropod samples. Even though total <i>A. vasorum</i> infection levels were revealed to be considerably lower than in the prior study, this epidemiological survey in principle reconfirms Obrigheim as a stable hyperendemic focus and thereby as a location with high metastrongyloid infection risk for domestic dogs, cats, and wildlife throughout the year. These results call for continuous epidemiological studies on gastropod populations to better understand metastrongyloid lungworm spread and infection dynamics over the years.