Lyme disease is an infection caused by a bacterium called Borrelia burgdorferi. In the western United States it is transmitted to humans through the bite of the Western Black-Legged Tick (Ixodes pacificus). The disease is named after the town of Old Lyme in Connecticut, where some of the first human cases were detected in the early 1970's. It is not new to the U.S., it had simply never been diagnosed in people with symptoms, which had been attributed to something else. The bacterium has been found in humans, dogs, horses, cattle and in wild animals such as mice, squirrels and other small mammals, but rarely in cats. Ticks pick up the disease when they feed on mice and woodrats, which serve as hosts or reservoirs for the bacterium and do not become ill. In this way, ticks spread the disease from animal to animal and to people by biting and feeding.
Lyme disease was first reported in California in 1978. It is now the most common tick-borne disease in California and the United States and is the most commonly reported vectorborne illness in the U.S. In 2014, it was the fifth most common nationally notifiable disease in the U.S. However, the disease does not occur nationwide and is concentrated most heavily in the northeast and upper Midwest, which account for over 96% of cases reported to the Centers for Disease Control (CDC). Studies by the CDC estimate that around 300,000 people are diagnosed with Lyme disease each year in the U.S.
Western Black-Legged Ticks have been found in 56 out of the 58 counties in California. It can be found in the Sierra Nevada foothills and the coastal range, mostly above elevations of 500-700 feet. In Yuba County, these ticks are commonly dispersed throughout the foothills. In Sutter County, they can be found in the Sutter Buttes, but only at the highest elevations. In some areas of the U.S. where Lyme disease is more common (mainly the northeast), between 15% and 25% of deer ticks (Ixodes scapularis, which do not occur in California) can carry the bacterium. In California, only about 1% to 2% of adult Ixodes pacificus ticks and 2% to 15% of the nymphal ticks, on average, are infected with Borrelia burgdorferi. In some areas north of the San Francisco Bay area, infection rates in ticks can be as high as 5%. In foothill areas of eastern Butte County, up to 1 in 4 collected ticks have been found to be infected with the bacterium. Some areas can have very high rates of infected ticks, such as Mendocino County with 41% of nymphal ticks infected. Infection rates will vary somewhat from year to year.
The life cycle of the tick has 4 stages: egg, larva, nymph and adult. Adult ticks are most active in the fall and early spring, when days are cooler and humidity is higher. They sit on the tips of long blades of grass or on the ends of branches of shrubs waiting for a host to come by (this is known as questing). Ticks do not fly, jump, run or drop from trees. They wait on vegetation with their legs outstretched hoping to snag a ride with their next host. Claws on the tips of their legs help them grab onto and crawl around on an animal or person. They can be found along hiking trails or animal trails. Once a tick finds a place to bite on its host's skin, they insert their mouthparts into the skin and slowly draw blood into their body. They use protein rich blood to help develop their eggs. Nymphal ticks are usually present from early spring to late summer. They must take bloodmeals in order to grow. Nymphal ticks are responsible for most Lyme disease transmission. Ticks of all stages except the egg stage are active and can bite whenever outdoor temperatures are above 40°F. However, most bites occur between May and August because people are more active outdoors during those months.
Early recognition of Lyme disease is very important. Ticks need to be feeding and attached to your skin for 24 hours or more before the bacterium will leave the tick and enter your body. If you can remove the tick within 24 hours of attachment, it may reduce your chances of contracting Lyme disease. Sometimes tick bites go unnoticed, so it is important to watch for early symptoms. One of the first symptoms is a rash that slowly enlarges, usually at the site of the bite, from about the size of a half dollar or larger to a large circular rash with a clear area in the center that may have a bull's-eye appearance. It may appear in 7 to 10 days or sometimes up to 30 days after the tick bite, and will only appear in about 60% of cases. Some people with Lyme disease never report seeing any kind of rash. This rash should not be confused with redness or an allergic reaction to the bite, which may appear within minutes or a few hours at the site of the bite. This is usually not a sign of Lyme disease. In addition to the rash, flu-like symptoms such as fever, body aches, vomiting and fatigue may be experienced. If you have been to an area where ticks occur or have found a tick attached to your skin, or believe you have been bitten by a tick and have any symptoms of Lyme disease, you should visit your physician immediately.
When possible, recover and save the tick so that it can be identified. Put it in a small jar with 70% rubbing alcohol, do not freeze it. If you are not comfortable removing the tick, you could seek treatment at your physician's office or an urgent care facility. To remove a tick from your skin, grasp it with a tissue or preferably with a good pair of tweezers. Try to grasp the tick near its head, as you do not want parts of the tick to break off or crush and stay in your skin. Pull the tick slowly but firmly straight out from the skin. Do not yank the tick out. The tick should eventually come loose. If not, a trip to your doctor's office might be in order. Never handle a tick with your bare hands, especially a crushed one. Do not twist the tick or use a burning cigarette or match, petroleum jelly, nail polish, bleach or kerosene in an attempt to remove it. After removal, wash the area with warm soapy water. Also, if you have a rash, take pictures of it. Early recognition of Lyme disease is very important, especially in relation to treatment options.
Most Lyme disease cases can be successfully treated with antibiotics if treatment is started early. If the disease goes untreated, later stages can be difficult to treat. As time goes by, migratory pain in the joints, tendons, muscles and bones may occur. Long term complications may develop weeks to months later and can include disorders of the heart and nervous system. Months to years after contracting Lyme disease, intermittent joint pain (Lyme arthritis) may become chronic, causing erosion of cartilage and bone.
You can protect yourself from Lyme disease. When outdoors in tick country, stay in open areas or on cleared maintained trails. Avoid grassy areas. When a tick manages to get on you, it will climb upwards searching for skin. Tucking pantlegs into socks or boots can help keep ticks away from your skin. Wearing light colored clothing will help you spot ticks more easily. Use an insect repellent containing DEET on bare skin and clothing. Follow label directions closely. Pets allowed in areas where ticks are present should be thoroughly checked every day.
Other tick-borne diseases such as Human Granulocytic Ehrlichiosis, Babesiosis and Rocky Mountain Spotted Fever occur in California and the U.S. but are much less prevalent than Lyme disease, especially in California.