The probability of acquiring Lyme disease depends on the type of tick, the geographic location where the tick was acquired, and the duration of attachment. In Ontario, the tick of concern is the blacklegged deer tick, Ixodes scapularis. Nymphs (immature ticks) and adult ticks can transmit the bacterium, B. burgdorferi. Nymphs are about the size of a poppy seed, and adults are closer in size to a sesame seed.
Tick attachment under 24 hours will usually not cause Lyme disease, as a tick must be attached for at least 36 hours before the bacterium can be transmitted. However, even with these time periods, the bacterium is still not usually transmitted within the first 48 - 72 hours of being attached. Thus, there is an increased risk if a tick has been attached for at least 72 hours. How much the tick is engorged can be used to estimate how long the tick may have been attached.
After a tick bite, a small red bump similar to a mosquito bite is common, but this is not a sign of Lyme disease and will usually disappear within 1-2 days. The difficulty surrounds symptoms of Lyme disease, which can vary depending on the stage of infection. If fever, facial paralysis, rash, or arthritis are present and occur after a tick bite, immediate medical attention should be sought.
Symptoms of Lyme disease:
- Single, local skin lesion called erythema migrans (EM)
General prevention includes using an insect repellant with 10-20% picaridin for those patients under 6 months of age for up to seven hours of protection; or 10% DEET for ages 6 months – 12 years for up to four hours of protection; or 20-30% DEET for patients under 12 years old for four to eight hours of protection. It’s recommended to wear a long-sleeved shirt, pants, socks and boots all tucked in when in risk areas. Skin should also be checked after possible exposure and patients should shower within two hours.
Overall, if signs of Lyme disease are suspected, timely treatment with antibiotics in the early stages can enable quick recovery. For information on tick removal, see these CDC instructions.