MISSISSIPPI STATE -- The fight to prevent West Nile Virus will likely be won on a personal level, with individual protection being the best defense against the disease.

James Jarratt, entomologist with Mississippi State University's Extension Service, said the West Nile Virus, a type of encephalitis, is being transmitted primarily by the Southern house mosquito, a Culex species found statewide.

"Not every mosquito that we see is a carrier of this disease," Jarratt said. "For every identifiable case of the disease that we see, there are probably 100 to 150 other cases where people get a mild form of the disease and never know what they had."

Mosquitos carry the disease after feeding on an infected animal. In the case of the West Nile Virus, the disease is found in birds, typically blue jays and crows. When a mosquito lands on a person to feed, it inserts its mouthparts and injects an anticoagulant into the skin, then cleans out its feeding channels into the person before eating.

"This is when the disease organism passes from the mosquito into the person," Jarratt said. "Since mosquitos pierce the skin to draw blood, they are able to inject the disease organism into the circulatory system."

Jarratt said other than birds, only humans and horses get the West Nile Virus. Personal protection against mosquito bites is the best protection against getting the virus.

"If you're outside early in the morning or late in the afternoon, wear long pants and long-sleeved shirts," Jarratt said. "Apply an insect repellant that contains DEET to all exposed skin."

He said to follow label directions when applying DEET and keep it out of the eyes. DEET is a repellant, not an insecticide, and keeps mosquitos from landing and feeding on people.

"DEET is the most effective product on the market," Jarratt said.

He said some other products have some mosquito repellency, but none as much as DEET. Citronella candles are popular outside repellants, but Jarratt said breezes reduce their effectiveness by diffusing the substance in the air.

To prevent mosquito bites indoors, keep the insects outside. Make sure screens fit snugly and have no holes, and don't leave doors or windows open.

"If you're going in or out, look around the door to see if there's any mosquitos. Wave your hand around to shoo away any that you find, and then quickly open and shut the door," Jarratt said. "The longer the door is open, the more opportunity mosquitos have to come in."

The same principle applies to cars. Jarratt recommended owners keep car doors and windows closed except when entering or exiting the vehicle.

Mosquitos that do make it into the house can be killed with household sprays containing Pyrethrin. This substance is sold under a variety of brand names and is used for flying insect control. Jarratt recommended leaving the room for 10 to 15 minutes after spraying, and to spray a bedroom one to two hours before bedtime.

Outdoors, reduce mosquito numbers by limiting standing water.

"When you consider the overall environment, it may seem a small thing to do to dump a few containers of standing water, but you don't want to grow your own mosquitos," Jarratt said.

He recommended dumping standing water whenever possible, and flushing every two to three days outdoor water supplies such pet water bowls and bird baths.

Small ponds or water features in gardens can be big mosquito breeding grounds. Jarratt's preferred mosquito treatment is to add predatory fish that feed on insect larvae. When this is not possible, he suggested using a substance known as Bti, sold under the trade name Mosquito Dunks. This substance kills mosquito larvae while not harming either fish or water plants.

More detailed information is available from the Extension Service at county offices.