Tick With Lyme Disease Discovered Just Across San Diego County Line : Health: Public warning confirms that an infected tick was found in San Clemente.

In a brushy San Clemente canyon near the San Diego County border, Orange County health officials have found a tick infected with debilitating Lyme disease.

That discovery marks the first such find in Southern California and the farthest south that an infected tick has ever been detected in California, local and state health officials said Friday.

Concerned about the discovery, Orange County health officials this week issued a public warning in their monthly Epidemiological Bulletin sent to more than 6,000 physicians.

But though it is now possible that Orange County residents can become infected with Lyme disease by native ticks, county health officials also stressed the risk was slight.

“There’s no reason for San Clemente people to be alarmed more than other people in a similar kind of environment,” said Dr. George Gellert, the county epidemiologist. “We are not expecting public health problems.”

Still, Gellert cautioned, “people who are involved with outdoor activities where they can have an exposure to ticks should take reasonable precautions.” He suggested that hikers wear long pants tucked into socks when walking through brush or high grass, and check their bodies frequently for ticks.

County public health biologist Jim Webb also called the find exciting but cautioned, “We don’t want to make it too much of a scary thing.”

Since March, 1989, Webb’s staff has found only one infected tick among more than 300 studied--a prevalance rate of only 0.3%. That contrasts with the rate in Northern California, where up to 3% of ticks carry Lyme disease, and the East Coast, where 70% to 100% of all ticks are infected, Webb noted. Ticks are most active in Southern California’s coastal canyons from October through May.

The disease was first identified in 1977 in Old Lyme, Conn., and more than 14,000 cases have been reported since then. The disease has become epidemic in the Northeast, Wisconsin, Minnesota and the Pacific Northwest, where thousands of people contract it each year.

Treatable with antibiotics, it often starts with a rash and flu-like symptoms (fever, headache and general malaise), but can progress to severe joint swelling resembling rheumatoid arthritis. In the Northeast, it is spread by the deer tick. On the West Coast, it is carried by the Western black-legged tick, also known as Ixodes pacificus .

In California, the disease has hit hardest in northern counties, where the climate is moist. Last year, Sonoma County reported 139 cases of Lyme disease, Trinity County 53 and Mendocino County 52. By contrast, Los Angeles County reported three cases last year, San Diego County four and Orange County five--but epidemiologists believe Southern California residents may have contracted the disease while visiting Northern California or the East Coast.

In July, 1989, the news media reported that a Laguna Beach woman had contracted the disease, apparently from a deer tick here, but additional blood tests by a UC Berkeley laboratory cast doubt on that diagnosis.

In the latest discovery, biologists from Orange County Vector Control on Feb. 21 found the infected tick in San Clemente along a small, stream-lined canyon near Cristianitos Road on the San Diego-Orange County border.

For those bitten by a tick, Gellert cautioned that it should be removed carefully, with a fingernail or, preferably, tweezers; if its head is torn, fluid from the tick could go directly into the skin.