Kate Campbell, Assistant Editor, California Farm Bureau Federation
A Plumas County horse has tested positive for West Nile virus, the first equine case in California this year and the first equine case ever reported in Plumas County. Officials said the appearance of the virus in this rural county, which is in the northeast corner of the state, is cause for concern.
The area does not have a vector control system like other areas of the state, and it lacks the news media that more urbanized areas use to educate the public about the insect-borne disease threat and ways to protect against infection.
Plumas County, with a population of about 21,000 residents, has no local television stations and no daily newspapers. There are radio stations that some residents can pick up via satellite.
The county has more than 100 lakes, 1,000 miles of rivers and streams and 1 million acres of national forest that are not treated to control mosquitoes. There are no accurate estimates of the county's equine population.
The infected horse, which is recovering, is a 3-year-old quarter horse mare. The confirmed case was detected about a month earlier than the first equine case detected in California in 2004, which is further cause for concern.
"It's known that we have the virus here," said Plumas County Agricultural Commissioner Karl Bishop. "Several birds tested positive for the virus last year. Now that we have our first confirmed equine case, we really need to focus on the impact on the human population.
"While we don't have a particularly large population, during the summer months we have a large infusion of travelers, visitors and vacationers who could be exposed. This is especially true for urban and foreign visitors, who may not be fully aware of the risks of contracting the infection."
Loyalton rancher Dave Roberti, president of Plumas-Sierra County Farm Bureau, said, "We knew this was coming so it's not a surprise. Our local vets have been active in getting the word out. They've put notices up in post office windows and they've been going out to the ranches to talk with clients."
Roberti said he owns a few horses and they've been fully vaccinated against the infection for the past several years, in part because his veterinarian has been "pushing hard" to get the vaccinations done.
"But now that it's here, people had better get on the stick," Roberti said. "People need to be prepared. I have serious concerns about protecting my own family. I have a 2-year-old daughter and my dad, who is 80, is very active and out farming with us every day. He often does the flood irrigating and there's standing water and mosquitoes everywhere."
California became the focus for West Nile virus in 2004 with 540 confirmed clinical equine cases. More than 40 percent of those horses died or were euthanized.
In 2004, the virus was detected among wild birds, sentinel chickens, horses or humans in all California counties.
The U.S. Centers for Disease Control and Prevention has predicted that California will again be the epicenter for West Nile virus this year. Organizations like the California Farm Bureau Federation and the California Rice Commission have been working with government agencies, various task forces and their own members to reduce the threat of infection to humans and animals.
Historically, areas where West Nile virus is first found see increased outbreaks of the infection in humans, horses and susceptible birds during the following mosquito season. State public health biologist Stan Husted said that once the virus has settled into an area, it explodes the following year, based on research about how the virus has acted in other states.
The CDC reported that in 2003 California had only three human West Nile virus infections. In 2004, California had 819 human cases in 23 counties. There were 28 human fatalities last year in California, including people in Kern, Los Angeles, Orange, Riverside and San Bernardino counties.
Public health experts predict that California, with its population of about 35 million, could see as many as 24,000 human cases of infection and as many as 500 deaths this year. So far, there has not been a confirmed case of human infection in 2005.
The outlook for the state's horses is uncertain. Equine population statistics are sketchy and vaccination rates for horses are hard to determine; therefore, there is no prediction as to how many animals may become infected or die this year.
West Nile virus is a mosquito-borne virus that was first detected in the United States in 1999 in the New York City area. It may cause a wide range of clinical illnesses from mild, flu-like symptoms to encephalitis, which is an inflammation of the brain that can be fatal to both humans and horses.
Birds serve as the primary reservoir for harboring the disease. After feeding on infected birds, mosquitoes transmit the disease to humans and horses.
State Veterinarian Richard Breitmeyer said, "We continue to urge horse owners to vaccinate against West Nile virus. A very high percentage of the horses that have died from the disease were not vaccinated."
Signs of West Nile virus in horses include stumbling, staggering, loss of coordination, muscle twitching, circling and inability to stand. Once infected, horses do not spread the disease to other humans or horses. While horses are susceptible to the virus, many horses infected with the disease do not develop any illness and recover uneventfully.
Health experts warn farmers, ranchers and horse owners to prepare now to help minimize this looming human and animal health crisis. They emphasize that those living in rural areas and those who spend a lot of time outdoors are especially vulnerable to contracting the infection.
The California Department of Food and Agriculture urges horse owners to consult their veterinarian immediately to ensure each horse is current on West Nile virus vaccinations. It is also important to practice mosquito control methods to reduce mosquito-breeding sites.
For more information on West Nile virus in horses, call the Equine West Nile information line (800) 268-7378, e-mail WNVirus@cdfa.ca.gov or visit www.cdfa.ca.gov/ahfss/ah/wnv_info.htm
For human West Nile virus information, go to www.westnile.ca.gov or www.cdc.gov and click on "Diseases & Conditions."