Entomological survey of Dirofilaria spp. in Sardinia (Italy). Molecular detection and mosquito species distribution

Background: Dirofilariosis, caused by Dirofilaria immitis and Dirofilaria repens, is expanding across Europe because of climate change, raising veterinary and zoonotic concerns. Among over 70 mosquito species considered to be implicated in their transmission, Culex pipiens and Aedes albopictus are recognized as major vectors. In Sardinia, where canine dirofilariosis is endemic, entomological information on Dirofilaria circulation was previously lacking. This study investigated mosquito species composition and assessed the presence of D. immitis and D. repens across five sites on the island. Methods: Mosquitoes were collected monthly from August 2022 to October 2023 using BG-Sentinel and CDC light traps. Specimens were morphologically and molecularly identified and screened for Dirofilaria DNA. Results: A total of 1219 mosquitoes were collected, including 945 females belonging to 13 species. The most abundant were Aedes caspius (31.4%), Aedes detritus (28.7%), Culex pipiens (19.5%), and Aedes albopictus (16.6%). Notably, among minor species, the presence of Culex perexiguus in Italy was confirmed for the first time by molecular analysis. Dirofilaria repens and D. immitis DNA were detected in 1.8% and 1.0% of mosquitoes, respectively, with C. pipiens and Ae. albopictus as the main vectors. Other species, including Ae. caspius, Ae. detritus, C. tarsalis, and C. perexiguus, also tested positive, suggesting a potential role in transmission. Conclusions: This study provides the first entomological report of Dirofilaria circulation in Sardinia, revealing a complex vector community and underscoring the need for continuous surveillance of dirofilariosis risk in the Mediterranean region.