Health officials Oct. 9 confirmed the West Nile virus had reached the Northwest after two domesticated racing pigeons in north Marana were found to be infected with the disease.
The Pima County Health Department and state health officials are also investigating reports that seven horses in the county, including some in Marana, may also be infected with the virus.
West Nile, which is transmitted to humans and horses by mosquitos that feed on birds, produces few if any symptoms in healthy adults. Only an estimated 20 percent of people infected with West Nile ever develop any symptoms or illness.
People 50 years old or older are at risk of more severe symptoms.
In rare cases, about one in 150 infections of humans, the virus can lead to encephalitis or meningitis and can be potentially fatal, according to a fact sheet distributed by the Centers for Disease Control in Atlanta.
The pigeons, which were euthanized Sept. 29, were owned by a family living in the Valley of the Sun Mobile Home and RV Park, 13377 N. Sandario Road.
The two 9-year-old pigeons had been ill and eventually became paralyzed. West Nile was suspected by a veterinarian who treated the birds and contacted county health officials, one of the birds' owners said,
The family asked not to be identified because they feared neighbors would shun them or object to their hobby of raising racing pigeons.
"Some people don't understand the nature of the disease. They might think they can get it from us or something," said one of the family members.
The disease can only be transmitted by the bite of an infected mosquito, said Dr. Elizabeth MacNeil, chief medical officer for the county's health department.
"So far in Pima County, we've confirmed the virus in three birds, including the two pigeons and one horse. We're still investigating the seven other horses, some of which are in Marana, but most of which are on Tucson's southwest side. No infections have been confirmed in any mosquitos or humans," MacNeil said.
The other bird carrying the virus was a crow found Sept. 23 in Robles Junction, west of Tucson.
The horse, an 11-year-old thoroughbred, was stabled on Tucson's east side and was euthanized Sept. 26.
No vaccine exists to protect humans from the virus, MacNeil said. A vaccine to protect horses is available through veterinarians. The disease is lethal to 20 percent to 50 percent of horses that contract the disease.
The symptoms of mild West Nile Fever in humans include fever, headache, and body aches occasionally accompanied by a rash on the trunk of the body and swollen lymph glands.
Symptoms of severe infection, or West Nile encephalitis or meningitis, include headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, and paralysis, according to the CDC.
As of Oct. 9, the CDC reported 4,249 cases of humans infected with West Nile nationwide. The milder West Nile Fever accounted for 65 percent of the cases, 29 percent were the more severe West Nile encephalitis and meningitis, and 6 percent of the confirmed instances were unspecified or unknown.
Marana Town Manager Mike Reuwsaat said the town found out about the infected pigeons through the owners, rather than from the county health department.
"We met with the county officials and asked that we be kept informed of developments in the future," Reuwsaat said. "If something like that comes up, they should be letting us know."
Marana had already been taking steps to try to reduce or eliminate areas of standing water that can serve as mosquito breeding grounds. Town officials met with Pima County Administrator Chuck Huckelberry and Sharon Bronson, chair of the Pima County Board of Supervisors, Oct. 8 to discuss moving the county's tire dump outside the town limits, Reuwsaat said.
The dump, located on Ina Road between Interstate 10 and the Santa Cruz River, has been a source of concern for nearby residents worried about West Nile.
Marana is trying to persuade the county to use bond funds to pay for the dump's relocation if voters approve a bond measure scheduled to be considered in May.
"The site that they are looking at is an old sewer plant site up by Pinal Air Park. Even if that site doesn't work, they've assured us they'll look at more places," Reuwsaat said. "It will cost about $2 million to move the facility somewhere else, and so we may recommend that as part of the bond issue, they include $2 million for relocation."
Health officials are urging people to limit their exposure to mosquitos and take steps to eliminate their habitats. Precautions recommended by the CDC include:
€ Apply insect repellant sparingly to exposed skin. Also spray clothing, as mosquitos can bite through thin material.
€ Whenever possible, wear long-sleeve shirts and long pants when outdoors.
€ Place mosquito netting over infant carriers when infants are taken outdoors.
€ Consider staying indoors at dawn, dusk and in the early evenings, which are peak times for mosquito bites.
€ Install or repair window and door screens so mosquitos cannot get indoors.
€ At least once or twice a week, empty water from flower pots, pet food and water dishes, birdbaths, swimming pool covers, buckets, barrels and cans.
€ Check for clogged rain gutters and clean them out.
€ Remove discarded tires and other items that collect water.
€ Be sure to check for containers or trash in places that may be hard to see, such as under bushes or under your home.