Ticks are small arachnids. Ticks require blood meals to complete their complex life cycles. Ticks are scientifically classified as Arachnida (a classification that includes spiders). The fossil record suggests ticks have been around at least 90 million years. There are over 800 species of ticks throughout the world, but only two families of ticks, Ixodidae (hard ticks) and Argasidae (soft ticks), are known to transmit diseases or illness to humans. Hard ticks have a scutum, or hard plate, on their back while soft ticks do not. Tick-borne diseases occur worldwide.
Ticks have a complex life cycle that includes eggs, larvae, nymphs, and adult male and female ticks. The larvae, nymphs (also termed seed ticks), and adults all need blood meals. Usually, the female adult (hard tick) is the one causing the most bites as males usually die after mating. Ticks do not jump, fly, or drop. They simply reach out with their legs and grab or crawl onto a host. Although ticks will die eventually if they do not get a blood meal, many species can survive a year or more without a blood meal. The hard ticks tend to attach and feed for hours to days. Disease transmission usually occurs near the end of a meal, as the tick becomes full of blood. It may take hours before a hard tick transmits pathogens. Soft ticks usually feed for less than one hour. Disease transmission can occur in less than a minute with soft ticks. The bite of some of these soft ticks produces intensely painful reactions.
Ticks are transmitters (vectors) of diseases for humans and animals. Ticks can transmit disease to many hosts; some cause economic harm such as Texas fever (bovine babesiosis) in cattle that can kill up to 90% of yearling cows. Ticks act as vectors when microbes in their saliva and mouth secretions get into the host’s skin and blood.