Ticks (Tick Bites)

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Tick facts

  • Ticks are scientifically classified as Arachnida (which includes spiders). The fossil record suggests ticks have been around at least 90 million years.
  • Most tick bites do not transmit pathogens.
  • There are a variety of tick-borne diseases.
  • There is a wide range of symptoms that usually develop days to weeks after the tick bite. The symptoms that become manifest depend on the particular microbe (pathogen) that is transmitted.
  • For all tick bites, local cleansing and antibiotic cream may be applied.
  • There are safe and effective methods for the removal of all types of ticks.

What are ticks?

Ticks are small arachnids. Ticks require blood meals to complete their complex life cycles. Ticks are scientifically classified as Arachnida (which 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.

Ticks have a complex life cycle that includes eggs, larvae, nymphs, and adult male and female ticks. The larvae, nymphs, 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 or fly. They simply reach out with their legs and grab or crawl onto a host. Although some larvae have preferred hosts, most ticks in the nymph or adult phase will attach a get a blood meal from several different kinds of animals, including humans. Except for a few species of larval ticks, the immature phases (larvae, nymphs) usually are even less selective about where they get a blood meal and are known to bite snakes, amphibians, birds, and mammals. Larvae are very small (about 1/32 of an inch with six legs), while nymphs are about 1/16-1/8 inch with eight legs and adults about 3/16-1/4 inch with eight legs. The complex life cycles are described in the last web citation below, and all of the web citations include pictures of various species of ticks. 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 vectors (transmitters) 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 pathogens in their saliva and mouth secretions get into the host's skin and blood. Ticks were understood to be vectors of disease in the mid-1800s, and as investigative methods improved (microscopes, culture techniques, tissue staining), more information showed the wide variety of diseases that could be transmitted by ticks.

Picture of a tick
Picture of a tick

There are many common names for various ticks (for example, dog tick, deer tick, and African tick), and these names appear in the scientific literature, too. Most common names represent a genus of ticks (see below). However, the common name "red" may be used by people to describe almost any tick that has had a blood meal.

Medically Reviewed by a Doctor on 7/25/2012

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Lyme Disease on Rise

Medical Author: William C. Shiel Jr., MD, FACP, FACR

Lyme diseaseis caused by infection with a bacterium called a spirochete(Borrelia burgdorferi) and is transmitted to humans by infected ticks (Ixodes scapularis and I. Pacificus). Patients with early stage Lyme disease have a characteristic rash(erythema migrans) accompanied by nonspecific symptoms (for example, fever, malaise, fatigue, headache, myalgia, and arthralgia). Lyme disease can usually be treated successfully with standard antibiotics.

The U.S. Centers for Disease Control and Prevention (CDC) released the results of a six-year survey study of Lyme disease from 1992 to 1998. During this period, a total of 88,967 cases of Lyme disease were reported to CDC by 49 states and the District of Columbia, with the number of cases increasing from 9,896 in 1992 to 16,802 in 1998. The researchers concluded that the increase in reported cases is probably a result of both a true increase in incidence within known high-risk areas as well as more complete reporting as a result of enhanced Lyme disease surveillance. They noted that surveillance capabilities and public awareness of Lyme disease have increased during this period.

Researchers also note that Lyme disease remains underreported with an estimated seven to 12 cases for each reported case.

Picture of characteristic rash of Rocky Mountain spotted fever

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