Thinning herds of white-tailed deer could go a long way in reducing cases of Lyme disease in areas where the disease is common, according to a new 13-year-long study. White-tailed deer are the major carriers of the adult blacklegged tick (deer tick, or Ixodes scapularis), which causes Lyme disease. White-tailed deer are the main carriers of the adult blacklegged tick.
The authors surveyed 90% to 98% of the permanent residents of one community in Connecticut. (Connecticut is the state where Lyme disease was originally discovered.) They surveyed the residents six times from 1995 to 2008. The researchers looked for exposure to tick-related disease and how often the residents had seen deer in the area.
After a controlled hunting program, the number of deer observations and the frequency of Lyme disease cases were greatly reduced. For example, a reduction in deer density to 5.1 deer per square kilometer brought a 76 percent reduction in tick abundance, and an 80% reduction in cases of Lyme disease reported by residents.
"Reducing deer populations to levels that reduce the potential for ticks to successfully breed should be an important component of any long-term strategy seeking to reduce the risk of people contracting Lyme disease," the authors conclude.
According to the Centers for Disease Control and Prevention, the blacklegged tick spreads the disease in the northeastern, mid-Atlantic, and north-central United States; the western blacklegged tick (Ixodes pacificus) spreads the disease on the Pacific Coast.
Ticks can attach to any part of the human body but are often found in hard-to-see areas such as the groin, armpits, and scalp. In most cases, the tick must be attached for 36-48 hours or more before the Lyme disease germ can be transmitted. The tick bite typically causes a "bulls-eye" rash that looks like a target.
Most humans are infected through the bites of immature ticks called nymphs. Nymphs are tiny (less than 2 millimeters, or about the size of the head of a pin), and are difficult to see. They feed during the spring and summer months.
Adult ticks can also transmit the Lyme disease bacteria, but they are much larger and may be more likely to be discovered and removed before they have had time to transmit the bacteria. Adult Ixodes ticks are most active during the cooler months of the year.