Re-monitoring of a hyperendemic focus of Angiostrongylus vasorum infections in native gastropod populations in Southern Germany

Abstract text

Introduction

The metastrongyloid nematode Angiostrongylus vasorum causes severe cardiovascular and pulmonary disease in domestic dogs. Geographically, canine A. vasorum infections typically show a patchy distribution pattern with hyperendemic foci alternating with low-prevalence or infection-free regions. The life cycle of A. vasorum obligatory includes gastropods as intermediate hosts. In 2018, we identified a hyperendemic focus with high gastropod A. vasorum prevalences in southern Germany (Obrigheim, Federal State of Baden-Wuerttemberg). To assess whether this hot spot indeed is stable and may therefore bear a significant risk of infection for resident dogs, we decided to perform a long-term follow-up study on A. vasorum infections in gastropod species in the area.

Objectives

Aim of the current study was to re-test and potentially confirm the hot spot of A. vasorum infections in native gastropod population in Obrigheim, and thereby to start a long-term monitoring to deduce eventual infections risks for resident dogs.

Material and methods

In the summer of 2022, 221 gastropods [215 slugs (Arion spp.) and 6 snails (Helix pomatia)] were manually collected at the hot spot meadow in Obrigheim. Gastropods were artificially digested and microscopically analysed for the presence of metastrongyloid larvae.

Results

We here confirmed a high prevalence for A. vasorum infections in gastropods, since 26.3% (58/221) of specimen were found infected. Of note, comparison to data from summer 2018 (13.6 %) revealed an almost doubling of gastropod A. vasorum prevalence in 2022. Thus, a stable A. vasorum hot spot may indeed be assumed for this specific meadow. Interestingly, hardly any other metastrongyloid infection was detected. Thus, Crenosoma spp. larvae were just found in 0.9% (2/221) of gastropods. All lungworm-infected gastropods belonged to the slug species Arion sp., whilst all Helix pomatia snail samples proved negative for metastrongyloid larvae. Overall, the larval burden varied from 1 to 241 larvae per slug.

Conclusion

Overall, we here confirmed the presence of an A. vasorum "hotspot" in gastropods of Obrigheim. As consequence, resident veterinarians were informed on current findings but hardly showed interest in A. vasorum infections. Furthermore, an information board was mounted on the meadow allowing interested dog owners to obtain A. vasorum-related information and to fill in an online questionnaire via QR-code scanning.