Why is the risk of transmission low after a tick bite?
Lyme disease is actually the most common tick-borne infection in the United States as well as in Europe. It is caused by a microscopic organism called Borrelia burgdorferi, which is transmitted by the deer tick, Ixodes scapularis, to a human host. Borrelia burgdorferi is present in about 20-40 percent of deer ticks. It lives in the gut of the tick and must work its way to the salivary glands, through which it leaves the tick as the tick feeds and it enters the human host. This process takes about 36 hours at which time the tick may start to become engorged with the host’s blood. Only about 20 percent of bitten patients will develop Lyme disease even after 72 hours of tick attachment, by which time the ticks are highly engorged. Therefore, it is very unlikely to develop Lyme disease from a tick that is not engorged, especially if it has been attached for less than 36 hours. Interestingly, although the transmission rate of Lyme disease by adult ticks is much higher than by ticks in the n
