Development of Aelurostrongylus abstrusus in hibernated vs non-hibernated Cornu aspersum snails

INTRODUCTION. The angiostrongylid Aelurostrongylus abstrusus inhabits the alveoli/alveolar ducts and bronchioles of domestic cats worldwide. First stage larvae (L1) are shed via the faeces in the environment, where they develop to the infectious third larval stage (L3) in gastropod intermediate hosts, i.e. slugs and snails (Morelli et al., 2021 Pathogens 10:454). Knowledge on factors influencing the larval developmental rate (LDR) inside mollusks is poor. Recent experiments have suggested that temperature has an impact on survival, vitality, infectivity and/or LDR to L3 of feline lungworms inside mollusks (Morelli et al., 2020 Vet. Parasitol. 282:109123; Napoli et al., 2020 J. Helminthol. 94: e113). The present study has investigated the effect of temperature on the LDR of A. abstrusus inside the land snail C. aspersum. The results are compared with those of a recent similar study on the crenosomatid Troglostrongylus brevior, which has shown that T. brevior increases its LDR in hibernated snails (Morelli et al., 2020 Vet. Parasitol. 282:109123). MATERIALS AND METHODS. Overall, 300 farm-bred snails were infected with 500 L1 of A. abstrusus and kept in vivaria at 25 ± 2 °C. On day 15 post infection (D15), 20 snails were digested to assess the overall LDR to L3 (0.8%) and randomly divided in 2 groups, i.e. 180 kept in vivaria at 25 ± 2 °C (G1) and 100 hibernated at 4 ± 2 °C (G2). On D30 i) 20 snails from each group were digested to evaluate the LDR to L3 and ii) another batch of 80 snails were selected from those living in the vivaria and hibernated at 4 ± 2 °C, setting up the group 3 (G3), i.e. snails hibernated on D30. The LDR was determined digesting 20 snails from each group on D45, D60 and D75. RESULTS AND CONCLUSIONS. An overall higher LDR of A. abstrusus was detected in G1, i.e. 2.8%, 1.4%, 6.0%, 5.0% (mean 3.8%), compared to G2, i.e. 3.2%, 2.8% 1.0% and 0.6% (mean 1.9%) on D30, D45, D60 and D75, respectively, and to G3, i.e. 2.0%, 3.5%, 1.5% (mean 2.3%) on D45, D60 and D75. These results indicate that the LDR of A. abstrusus is positively influenced by the increase of temperature. The larvae may also develop at low temperatures, though less efficiently than T. brevior. Overall, this study further corroborates the hypothesis that angiostrongylids may have lower cold-resistance abilities than crenosomatids (Morelli et al., 2020 Vet. Parasitol. 282:109123).