Mosquito (Diptera: Culicidae) surveillance for Dirofilaria immitis (Rhabditida: Onchocercidae) using a zoo as a focus for operational detection in central Utah.

Across the United States, Dirofilaria immitis (Leidy), commonly known as dog heartworm, poses a significant threat to common pets, including dogs, ferrets, and cats, but also to exotic and feral animals. This study focused on surveillance of D. immitis in mosquitoes collected in the Salt Lake Valley of Utah, with an emphasis on animals housed at a local zoo. Mosquitoes (Diptera: Culicidae) from the genera Culex, Culiseta, and Aedes were collected, identified, sorted, and subjected to DNA extraction. In the summer of 2023, extracted DNA from 320 pooled samples of 3,459 mosquitoes was tested by PCR with D. immitis-specific and panfilarial primers. Two samples collected at the zoo were positive for D. immitis, and 2 additional samples tested positive with panfilarial primers, though the precise filarial species could not be determined. In the summer of 2024, an additional 71 samples of 1,999 mosquitoes were collected from trapping at 12 locations across Salt Lake Valley, but none were positive for D. immitis. This study confirmed the presence of D. immitis-infected mosquitoes in the Salt Lake Valley, prompting the zoo to expand prophylaxis for at-risk animals and underscoring the importance of ongoing surveillance efforts. Further monitoring is recommended to assess and manage ongoing threats posed by mosquito-transmitted heartworm.