Aedes Vexans and Aedes Sierrensis (Diptera: Culicidae): Potential Vectors of Dirofilaria Immitis in Tehama County, Northern California, USA1

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Abstract
Two sites in Tehama Co., northern California, USA, were studied during May–July 1980 to determine potential mosquito vectors of canine heartworm (Dirofilaria immitis). Aedes vexans and Ae. sierrensis predominated at a town site and Ae. sierrensis at a sparsely inhabited woodland site. Both Aedes species entered field-placed kennels housing a D. immitis-infeclecl dog and engorged. Of 52 Ae. vexans and 10 Ae. sieirensis collected, filariae completed development in 7 (13.5%) and 6 (60.0%), respectively, after 13–28 days of extrinsic incubation at ambient temperatures in an open laboratory. Mosquitoes collected from uninfected dogs in and outside kennels and from CO2-baited light traps were examined for wild Dirofilaria infection. Eight (3.1%) of 256 Ae. vexans examined from the town site harbored filariae, presumably D. immitis; infection rates up to 10.5% were found in individual collections. Filariae were not observed in the 61 Ae. sieirensis examined from both sites. Vector potential of Ae. vexans is considered high, based on its suitability as an intermediate host, recovery of Dirofilaria from wild mosquitoes, ecological association with clogs and seasonal abundance. Ae. sieirensis was a suitable host fory D. immitis and was associated with dogs; however, its vector potential may be limited in Tehama Co. by a short season of adult activity.