Surveillance of Dirofilaria immitis (Rhabditida: Onchocercidae) in mosquitoes (Culicidae) 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. Extracted DNA from 320 pools of 3,459 mosquitoes was tested by PCR with D. immitis-specific and panfilarial primers. In summer 2023, two pools of mosquitoes collected at the zoo were positive for D. immitis, and two additional pools tested positive with panfilarial primers. In summer 2024, 1,999 mosquitoes were collected from trapping at 11 locations across Salt Lake Valley, but none of the 71 pools were D. immitis positive. 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.