A large mite specialized as a blood-feeding, external parasite of terrestrial vertebrates; fangs modified for cutting skin; cuticle typically elastic, stretching to accommodate blood meal; can transmit diseases of humans and domesticated animals. (Order: Acari. Family: Ixodidae.)
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Ixodidae - Hard ticks |
Tick is the common name for the small arachnids that, along with mites, constitute the order Acarina.
Characteristics
The major families of tick include the Ixodidae or hard ticks, which have thick outer shells made of chitin, and Argasidae or soft ticks, which have a membraneous outer surface. Soft ticks typically live in crevices and emerge briefly to feed, while hard ticks will attach themselves to the skin of a host for long periods of time.
Ticks as disease vectors
Ticks are second only to mosquitoes as vectors of human disease, both infectious and toxic.
Hard ticks can transmit human diseases such as relapsing fever, Lyme disease, Rocky Mountain spotted fever, tularemia, equine encephalitis, Colorado tick fever, and several forms of ehrlichiosis. Hard ticks may remain attached to the skin of a host for long periods of time. For example, nearly 90% of all Lyme disease(caused by the Borrelia burgdorferi bacterium) cases have been reported in the Northeastern part of the US, only specific deer ticks carry that disease. According to the Rhode Island Department of Health, roughly 70% of people who develop Lyme disease in that part of North America catch it from ticks in their own yard.
Location
Ticks are blood-sucking parasites that are often found in tall grass, where they will rest themselves at the tip of a blade so as to attach themselves to a passing animal or human. It is a common misconception that the tick can jump from the plant onto the host.
Population Control
A method of reducing deer tick (Ixodes Scapularis/Dammini) populations - Damminix - may be cited.
The parasitic Ichneumon wasp Ixodiphagus hookeri has long been investigated for its potential to control tick populations.
Another "natural" form of control for ticks is the Guineafowl.
Life cycle
Deer (black-legged) tick
The deer (or black-legged) tick, and the related western black-legged tick, are the primary known transmitters of Lyme disease in the United States. Like all species of ticks, deer ticks and their relatives require a blood meal to progress to each successive stage in their life cycles.
The life cycle of the deer tick comprises three growth stages: the larva, nymph and adult. In both the northeastern and mid-western U.S., where Lyme disease has become prevalent, it takes about two years for the tick to hatch from the egg, go through all three stages, reproduce, and then die.
Larva
Eggs laid by an adult female deer tick in the spring hatch into larvae later in the summer.
If the host is already infected with the Lyme disease spirochete from previous tick bites, the larva will likely become infected as well. In this way, infected hosts in the wild (primarily white-footed mice, which exist in large numbers in Lyme-endemic areas of the northeast and upper mid-west) serve as spirochete reservoirs, infecting ticks that feed upon them.
Because deer tick larvae are not born infected, it is believed that they cannot transmit Lyme disease to their human hosts.
Nymph
Most larvae, after feeding, drop off their hosts and molt, or transform, into nymphs in the fall. If not previously infected, the nymph may become infected if its host carries the Lyme disease spirochete from previous infectious tick bites. Peak activity for adult deer ticks occurs in late October and early November.
As winter closes in, adult ticks, unsuccessful in finding hosts, take cover under leaf litter or other surface vegetation, becoming inactive when covered by ice and snow. Generally, winters in the northeast and upper mid-west are cold enough to keep adult ticks at bay until late February or early March but not when temperatures begin to rise.
Adult female ticks that attach to deer, whether in the fall or spring, feed for approximately one week.
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