There are many different types of ticks in the United States, some of which are capable of transmitting infections. Three species of ticks are commonly encountered in Missouri. Most common are the lone star tick (Amblyomma americanum)and American dog tick (Dermacentor variabilis). The deer tick, or blacklegged tick (Ixodes scapularis), is also common. The risk of developing these infections depends upon the geographic location, season of the year, type of tick, and for Lyme disease, how long the tick was attached to the skin.
Even though many people are concerned after being bitten by a tick, the risk of acquiring a tick-borne infection is very low, even if the tick has been attached, fed, and is actually carrying an infectious agent. Ticks transmit infection only after they have attached and then taken a blood meal from their victim. A deer tick that transmits Lyme disease must feed for >36 hours before transmission of the organism, a spirochete, which causes Lyme disease. The risk of acquiring Lyme disease from an observed tick bite is only 1.2 to 1.4 percent, even in an area where the disease is common. Take home point: Check your entire body daily if in a high tick exposure area, in southeast Missouri that is essentially any outdoor activity!!
The organism that causes Lyme disease, Borrelia burgdorferi, lies dormant in the inner aspect of the tick’s midgut. The organism becomes active only after exposure to the prolonged warm blood meal. Once active, the organism enters the tick’s salivary glands. As the tick feeds, it must get rid of excess water through the salivary glands. Thus, the tick salivates organisms into the wound, thereby passing the infection to the host.
If a person is bitten by a deer tick (the type of tick that carries Lyme disease), a healthcare provider will likely advise one of two approaches:
- Observe and treat if signs or symptoms of infection develop
- Treat with a preventive antibiotic immediately
There is no benefit of blood testing for Lyme disease at the time of the tick bite; even people who become infected will not have a positive blood test until approximately two to six weeks after the infection develops.
HOW TO REMOVE A TICK
The proper way to remove a tick is to use a set of fine tweezers and grip the tick as close to the skin as is possible. Do not use a smoldering match or cigarette, nail polish, petroleum jelly (Vaseline), liquid soap, or kerosene because they may irritate the tick and cause it to behave like a syringe, injecting bodily fluids into the wound.
The proper technique for tick removal includes the following:
- Use fine tweezers to grasp the tick as close to the skin surface as possible.
- Pull backwards gently but firmly, using an even, steady pressure. Do not jerk or twist.
- Do not squeeze, crush, or puncture the body of the tick, since its bodily fluids may contain infection-causing organisms.
- After removing the tick, wash the skin and hands thoroughly with soap and water.
- If any mouth parts of the tick remain in the skin, these should be left alone; they will be expelled on their own. Attempts to remove these parts may result in unnecessary skin trauma.
AFTER THE TICK IS REMOVED.
Need for treatment — The Infectious Diseases Society of America (IDSA) recommends preventive treatment with antibiotics only in people who meet ALL of the following criteria:
- Attached tick identified as an adult or deer tick
- Tick is estimated to have been attached for ≥36 hours (based upon how engorged the tick appears or the amount of time since outdoor exposure)
- The antibiotic can be given within 72 hours of tick removal
- The local rate of tick infection with B. burgdorferi is ≥20 percent (known to occur in parts of New England, parts of the mid-Atlantic states, and parts of Minnesota and Wisconsin)
- The person can take doxycycline (eg, the person is not pregnant or breastfeeding or a child <8 years of age)
If the person meets ALL of the above criteria, the recommended dose of doxycycline is a single dose of 200 mg for adults and 4 mg/kg, up to a maximum dose of 200 mg, in children ≥ 8 years.
If the person cannot take doxycycline, the IDSA does not recommend preventive treatment with an alternate antibiotic for several reasons: there are no data to support a short course of another antibiotic, a longer course of antibiotics may have side effects, antibiotic treatment is highly effective if Lyme disease were to develop, and the risk of developing a serious complication of Lyme disease after a recognized bite is extremely low.
MONITORING FOR LYME DISEASE
Signs of Lyme disease — Whether or not a clinician is consulted after a tick bite, the person who was bitten (or the parents, if a child was bitten) should observe the area of the bite for expanding redness, which would suggest erythema migrans, the characteristic rash of Lyme. Approximately 80 percent of people with Lyme disease develop erythema migrans so it is a fairly good predictor if Lyme disease is likely.
The erythema migrans rash is usually a salmon color although, rarely, it can be an intense red, sometimes resembling a skin infection. The lesion typically expands over a few days or weeks and can reach over 20 cm (8 inches) in diameter. As the rash expands, it can become skin-colored in the center. The center of the rash can then appear a lighter color than its edges or the rash can develop into a series of concentric rings giving it a “bull’s eye” appearance. This rash occurs typically one week to one month after a tick bite.
Components of tick saliva can also cause a localized rash or red area at the site of the tick bite that should not be confused with erythema migrans. This reaction usually does not expand to a size larger than a dime and needs no particular treatment.
Other symptoms may include fever, headache, fatigue, arthritis, meningitis, various neurologic problems, hepatitis, eye inflammation, and heart conduction problems. Many of these symptoms do not occur until weeks or months after a tick bite. Lyme disease is therefore occasionally found to be the cause for vague persistent illness.