Ticks and Tickborne Diseases
Spring and summer bring warm temperatures, just right for walking in the woods and other outdoor activities. Warm weather also means that ticks become active, and this can lead to the transmission of tickborne disease.
The tickborne diseases most often found in MD-DC-VA are Lyme disease, Rocky Mountain spotted fever and ehrlichiosis.
One important point to remember is that less than 1% of ticks are infected with any disease. And if the tick is infected, it still takes several hours after it attaches to you to be able to infect you (experts usually quote three hours).
Lyme disease, first identified in 1975 in Lyme, Connecticut, is a bacterial illness transmitted by a tick bite. Although the disease is found more frequently in the North and the upper Midwest, cases have been reported in MD-DC-VA since 1982. For the past 5 years an average of 77 cases have been reported annually, mainly from the eastern and central parts of the state.
The deer tick (Ixodes scapularis, previously called Ixodes dammini) is the most common carrier of Lyme disease in the eastern United States. Ticks complete their life cycle from eggs to adults in approximately two years. The adult deer tick feeds and mates on the white-tailed deer in the fall and winter. In the spring the tick drops off to lay eggs which hatch into larvae. During the summer, the larvae feed on small rodents, most commonly the white-footed mouse. If the rodents are carrying the Borrelia burgdorferi bacteria that cause Lyme disease, the tick larvae can become infected. Once they feed, the larvae molt into nymphs which are dormant during the winter and become active the following spring and summer. If the larvae were infected, the nymphs also will contain the bacteria.
Transmission usually occurs when the nymph is active and feeds on small and large animals, and occasionally on humans. At this stage, the tick is about the size of a pinhead. By fall nymphs become adults which also may transmit the disease. Transmission by the nymph or adult usually does not occur until the tick has been attached for over 1 to 2 days.
The Department of Health has been monitoring animals, ticks, and the number of human Lyme disease cases in MD-DC-VA. Most of the human Lyme disease cases reported in MD-DC-VA occur in coastal areas. MD-DC-VA studies have identified areas on the Eastern Shore and near the York and Potomac Rivers where deer tick populations are established. B. burgdorferi bacteria have been found in some of these ticks and in some rodents in the same areas. The percentage of MD-DC-VA ticks and animals that are infected is much lower than the infection rates seen in the northeastern United States where many more human cases are reported. Deer ticks also have been found in other parts of MD-DC-VA, but may not be established there or contain the infective organism.
Within 2 days to a few weeks after being bitten by an infected tick, 60 percent of people develop a circular or oblong rash, called erythema migrans or EM, at the site of the bite. The EM rash usually increases to 2 to 3 inches in diameter and sometimes to as large as 20 inches. As it enlarges, the center clears giving it a “bull’s-eye” appearance. Sometimes multiple rashes occur. Because it does not itch or hurt, EM may be hard to detect.
In addition to, or instead of the EM, a feeling of tiredness, headache, fever, stiff neck, muscle aches, joint pain and swollen lymph nodes can occur. If left untreated, Lyme disease can cause chronic arthritis or heart and nervous system complications in a small percentage of infected people several weeks to several months after exposure.
Because the deer tick is so small in its nymph stage, many people are not aware of its bite. If you have been in an area that may contain ticks and experience any of these symptoms, contact your doctor. State that you may have been bitten by a tick. This is extremely important because the diagnosis of Lyme disease is usually based on symptoms and history of tick exposure. The available blood tests are often negative. On the other hand, recent studies have shown that many people who think they may have the late stages of Lyme disease, actually suffer from other maladies and have blood tests that are falsely positive.
A vaccine is available, but is only recommended for people at high risk of acquiring Lyme disease. Your risk depends on whether you spend a lot of time outdoors where there are infected ticks. MD-DC-VA is generally a low risk state for Lyme disease, but parts of eastern MD-DC-VA do have infected deer ticks. People between the ages of 15 and 70, who live in those areas and spend large amounts of time in wooded, brushy or overgrown areas where ticks live may consider the vaccine. The vaccine, however, is not 100 percent effective, and people who get the vaccine should still use personal protective measures. At present, the vaccine is given as an injection in three doses over a year’s time. Consult with your physician about the risks and benefits of using the vaccine.
When detected early, Lyme disease can be mild and easily treated with oral (by mouth) antibiotics such as tetracycline or penicillin. Even in the late stages, Lyme disease usually can be treated successfully with antibiotics, but the treatment lasts longer and is more involved.