Host preference of mosquitoes in Bernalillo County, New Mexico.

Host preference of mosquitoes was determined using animal-baited traps. Hosts used in the study were cattle, chickens, dogs, and horses. Ten mosquito species representing 4 genera were collected from the animal-baited traps. Aedes vexans, Aedes dorsalis, Culex quinquefasciatus. Culex tarsalis, and Culiseta inornata were used as indicator species for data analysis. Greater numbers of Ae. vexans, Ae. dorsalis, and Cs. inornata were collected from cattle and horses than from chickens or dogs. In addition, engorgement rates were higher on mammals than on chickens. Engorgement and attraction data for Cx. quinquefasciatus suggested a preference for chickens and dogs over cattle and horses. A slight preference for chickens and dogs was seen with Cx. tarsalis, but the degree of host preference of Cx. tarsalis was less than that in either Ae. vexans or Cx. quinquefasciatus.

Evaluation of cattle insecticide treatments on attraction, mortality, and fecundity of mosquitoes.

Attraction, engorgement, mortality, and fecundity were observed on host-seeking Aedes vexans and Psorophora confinnis given the opportunity to feed on insecticide-treated steers in stable traps. Individual steers were treated with Ectrin ear tags, Ectrin spray, Terminator ear tags, Saber ear tags, or Ivomec injection or were left untreated. Aedes vexans and Ps. confinnis accounted for over 98% of 20,738 mosquitoes collected. Relative attraction ranged from 0.45 with Saber ear tag to 0.84 with Terminator ear tag. Engorgement rates of mosquitoes from insecticide-treated steers ranged from 55 to 91%. Engorgement was reduced 18-45% by Terminator ear tag, Ectrin spray, and Saber ear tag treatments. Forty-eight percent mortality of unengorged Ae. vexans and 61% mortality of unengorged Ps. confinnis was observed at collection with the Saber ear tag treatment. Percentage of mortality of engorged mosquitoes of both species was generally much lower. Ivomec injection treatment showed the greatest effect on delayed (48-h) mortality of engorged mosquitoes, with 41 and 82% mortality for Ae. vexans and Ps. confinnis, respectively. No insecticide treatment had a significant effect on fecundity.

Potential mosquito vectors of Dirofilaria immitis in Bernalillo County, New Mexico.

The susceptibility of Aedes vexans, Culex quinquefasciatus, and Culex tarsalis to Dirofilaria immitis infections was evaluated in Bernalillo Co., New Mexico. Mosquitoes that had taken a blood meal from a D. immitis-infected dog were dissected and observed for developing larvae. Infection rates for Ae. vexans, Cx. quinquefasciatus, and Cx. tarsalis were 68.9, 40.6, and 30.2%, respectively. Infective D. immitis larvae developed after a minimum of 8 days in Ae. vexans vs. 14 days in both Cx. quinquefasciatus and Cx. tarsalis. Vector efficiency of Ae. vexans was 20.4%, with a mean of 5.9 infective larvae developing from a mean of 29 microfilariae ingested per mosquito. Vector efficiency in Cx. quinquefasciatus and Cx. tarsalis was 2.7 and 0.4%, respectively. These results suggest that Ae. vexans has the greatest potential for D. immitis transmission.