Ticks are blood-feeding parasites that are often found in tall grass and shrubs where they will wait to attach to a passing host. Physical contact is the only method of transportation for ticks. Ticks do not jump or fly, although they may drop from their perch and fall onto a host.
Changes in temperature and day length are some of the factors signaling a tick to seek a host. Ticks can detect heat emitted or carbon dioxide respired from a nearby host. They will generally drop off the animal when full, but this may take several days. In some cases, ticks will live for some time on the blood of an animal. Ticks have a harpoon-like structure in their mouth area, known as a hypostome, that allows them to anchor themselves firmly in place while feeding. The hypostome has a series of barbs angled back, which is why they are so difficult to remove once they have penetrated a host.
Ticks are second only to mosquitoes as vectors of human disease, both infectious and toxic. Hard ticks can transmit human diseases such as Lyme disease, Rocky Mountain spotted fever, tularemia, equine encephalitis, Colorado tick fever, and several forms of ehrlichiosis. Additionally, they are responsible for transmitting livestock and pet diseases, including babesiosis, anaplasmosis and cytauxzoonosis. Hyalomma ticks are known to transmit Congo fever. Soft ticks transmit tick-borne relapsing fever spirochetes such as Borrelia turicatae, Borrelia parkeri and Borrelia hermsii.
Generally, tick-borne diseases correspond to a specific tick-host combination, and are limited in their geographical extent. 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.
The life cycle of the hard tick requires one to three years to complete, and may require one, two or three different host animals. The following describes the three-host lifecycle
1 - An adult female tick drops off her final host, lays her eggs and dies.
2 - Tiny six-legged larvae congregate on grasses or other leaves and stems not far from ground level. Lucky individuals complete that stage after attaching to a host, feeding, and dropping off. The larval stage can cause intense itching on humans, but does not transmit disease.
3 - Larvae molt and emerge as the nymph stage, about 1.5 mm long and again climb a grass stem to await a host. The nymph stage also causes intense itching in humans.
4 - Engorged nymphs drop off, molt to the adult stage, approximately 3 mm long, mate, and again climb a stem to await a host. Adults are amazingly stealthy on humans in spite of their size, and may not be noticed until they have been attached for a considerable time.
Ticks reproduce sexually, use internal fertilisation and are oviparous. Ticks produce a lot of young but the young are not nurtured.
Tick is the common name for the small arachnids in superfamily Ixodoidea that, along with other mites, constitute the Acarina. Ticks are ectoparasites (external parasites), living by hematophagy on the blood of mammals, birds, and occasionally reptiles and amphibians. Ticks are important vectors of a number of diseases, including Lyme disease. According to Pliny the Elder, ticks are "the foulest and nastiest creatures that be.
The major families of ticks 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. A third family, Nuttalliellidae, contains one rare African species, Nuttalliella namaqua. 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, like most other arachnids, typically have eight legs but may have six depending on their developmental stage. Tick bites look like mosquito bites, but can also sometimes bruise or resemble a bullseye.
