Ecoepidemiology of Angiostrongylus cantonensis in Mediterranean rats: spatial heterogeneity, low genetic diversity and precipitation-driven transmission

Angiostrongylus cantonensis is a neurotropic zoonotic nematode that has recently expanded into Mediterranean Europe, with reports from Mallorca, Valencia, and Naples. On Mallorca, the parasite circulates in gastropods and wildlife, yet no autochthonous human cases have been reported to date. In this context, information on its dynamics in definitive hosts remains limited. We conducted a 2.5-year surveillance study of A. cantonensis in rats on the Mediterranean island of Mallorca (Spain), integrating spatial, host-related, ecological, climatic, seasonal, and genetic data. Using a volunteer-assisted sampling strategy, 287 rats (Rattus rattus and R. norvegicus) were collected across 22 municipalities. Overall prevalence was 6.27%, with pronounced spatial heterogeneity: some municipalities showed no infection, whereas local prevalence exceeded 40% in others. Generalized linear models identified precipitation as the only environmental variable significantly associated with infection, whereas no clear seasonal pattern was detected. Host-related traits and habitat showed limited influence on infection probability, suggesting limited ecological structuring at the analysed scale. Genetic analyses revealed a single mitochondrial haplotype circulating in Mallorca, identical to one of the two haplotypes previously reported in Europe, consistent with low genetic diversity in the Mediterranean region. Together, these findings indicate heterogeneous and focal circulation of A. cantonensis in rats from Mallorca and underscore the limitations of relying solely on definitive hosts for surveillance. This study advances understanding of the ecoepidemiology of A. cantonensis in emerging European foci and highlights the value of integrative surveillance approaches in recently affected regions to detect shifts in prevalence, spatial distribution, and transmission dynamics over time.