Dave Fahrner of Pittsburgh writes, "Have you heard of an increase in the deer tick population this year? Last fall, my dog and I came home from several outings, and I picked many ticks from each of us. I haven't seen as many ticks in my entire life as I have recently. Have you heard similar reports?"
Yes, I've had numerous phone calls and emails about ticks recently. This is shaping up to be a big tick year, thanks to the unusually mild winter we have had. A good hard winter usually controls ticks that can overwinter in egg, larval or adult form. This year we just have not had that prolonged big freeze.
The dog and deer tick life cycles require three hosts and can take several years to complete, depending on the supply of hosts. Adult females lay eggs in the fall. The eggs that survive winter hatch in the spring. Tiny six-legged larval ticks work their way on to the tips of ground vegetation. There they wait, sometimes for months, and "quest" for a small mammal, usually a deer mouse.
The larval tick holds on to the grass with its rear legs and with its outstretched front legs waits for a mouse to wander by. When it hitches a ride, it quickly attaches to a thin piece of skin for its first blood meal.
The larva then drops to the ground and molts into the tiny, eight-legged nymph stage and waits for its next host, usually a medium sized mammal, such as a raccoon or fox. After hitching this ride and enjoying another blood meal, the nymph drops off and molts into the eight-legged adult tick.
Deer ticks can acquire the Lyme disease bacterium during any life stage, and once infected, they carry the bacterium for life. Most humans are infected by bites from the nymphs because nymphs are tiny (less than two millimeters) and difficult to detect. Adult deer ticks are easier to detect and remove simply because they are larger and more visible.
After molting into the adult form, ticks wait for a deer or human to wander by. This host provides the blood that enables female ticks to manufacture up to 4,000 eggs. After depositing the eggs on the ground, the female dies. The entire life cycle of deer and dog ticks takes two years to complete.
Fortunately, most eggs do not usually survive the winter, and most immature ticks fail to find all three required hosts, so they starve. Enough, however, survive to make life miserable for humans and dogs.