SALT LAKE CITY (AP) — Officials say mosquitoes carrying the West Nile virus were found in three Utah counties.

KUTV-TV reports mosquitoes with the West Nile virus were reported in Davis, Box Elder and Uintah Counties this week.

Officials say the Salt Lake City Mosquito Abatement District has been working all summer to control the mosquito population in the city.

The district researches the most effective means of abatement.

Assistant Manager Greg White says the bugs can become resistant to pesticides so the team closely monitors the effectiveness of different chemicals.

White says he prefers to control the mosquito population through biological means as a first resort. That can include releasing small fish that eat mosquito larvae.