• Ticks are scientifically classified as Arachnida (a classification that includes spiders). The fossil record suggests ticks have been around at least 90 million years.
• Most tick bites do not transmit harmful microbes.
• 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 depend on the particular microbe 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 (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.
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 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. 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.
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.
What are tick bite symptoms and signs?
Unfortunately for the purpose of detection, the tick bite is usually painless and remains that way even after the tick stops the blood meal and falls off of the skin. Later, the bite site may develop itching, burning, redness, and rarely, localized intense pain (some soft tick bites) in some individuals. A few individuals may be sensitive or allergic to tick bites (tick saliva secretions) and develop rash, shortness of breath, swelling, numbness, or paralysis. However, the majority of individuals with tick bites develop no symptoms, and many people do not remember getting bitten.
Some immediate symptoms that infrequently or rarely develop during or immediately after a tick bite may be fever, shortness of breath, weakness, vomiting, swelling, weakness or paralysis, headache, confusion, or palpitations. Individuals with these symptoms should be seen immediately by a doctor.
Recently, researchers have found that the tick bite (mainly the saliva produced by the lone star tick) has caused thousands of people to become allergic to red meat (beef, pork, venison, and occasionally, milk). People can eat poultry (chicken, turkey) and have no allergic reactions. When they eat red meat, they develop swelling and hives. Some may develop anaphylaxis. The reaction is thought to be due to an alpha-gal antigen in the tick’s gut and/or saliva that stimulates an immune response that results in an allergic reaction when red meat is consumed.
What diseases do ticks transmit (act as vectors) to humans?
Although most tick bites do not transmit pathogens, some bites do. It is not possible to determine if a tick is carrying pathogens visually. The following is a list of all of the major tick-borne diseases, the usual tick vector(s), and the pathogen(s) the tick transmits that may occur in the United States.
• Tularemia — Dermacentor variabilis (American dog tick; several species are also known as a wood tick) (hard tick) and Amblyomma americanum or lone star tick (hard tick) — vectors for Francisella tularensis bacteria
• Anaplasmosis (human granulocytic anaplasmosis or HGA) — Ixodes species (hard tick) — vectors for Anaplasma phagocytophilum bacteria
• Colorado tick fever — Dermacentor andersoni (hard tick) — vectors for Coltivirus, a RNA virus
• Powassan encephalitis — Ixodes species and Dermacentor andersoni (both hard ticks) — vectors for Powassan encephalitis virus, an RNA arbovirus
• Babesiosis — Ixodes species (hard ticks) — vectors for Babesia, a protozoan
• Ehrlichiosis — Amblyomma americanum or lone star ticks; see photo below with “lone star” mark on the dorsal surface (hard ticks) — vectors for Ehrlichia chaffeensis and Ehrlichia ewingii bacterial species
• Rocky Mountain spotted fever — Dermacentor variabilis (American dog tick, see picture below) and Rocky Mountain wood tick (Dermacentor andersoni) (hard tick) are the primary vectors and occasionally the brown dog tick (Rhipicephalus sanguineus); Amblyomma cajennense (hard tick) is the vector in countries south of the U.S. — vectors for Rickettsia bacteria.
• Lyme disease — Ixodes species including deer ticks or also known as black-legged ticks (hard ticks, see photo below) — vectors for Borrelia species of bacteria
• Heartland virus — a viral disease discovered in 2012 transmitted by Amblyomma americanum or lone star tick
• Tick-borne relapsing fever — Ornithodoros moubata or African tick; see illustration below (soft tick) — vectors for Borrelia species of bacteria
• Q fever — Rhipicephalus sanguineus, Dermacentor andersoni and Amblyomma americanum (all three are hard ticks) — vectors for Coxiella burnetii, a bacterium
• Southern tick-associated rash illness (STARI) — Amblyomma americanum or lone star tick (hard tick) — infectious agent not yet identified according to U.S. Centers for Disease Control and Prevention (CDC)
This list shows that some ticks (for example, Ixodes) can transmit more than one type of pathogenic microbe (virus, bacteria, and protozoa). It is possible to transmit more than one pathogen in a single tick bite, although this rarely occurs. Outbreaks of tick-related illnesses follow seasonal patterns (about April to September in the U.S.) as ticks evolve from larvae to adults.
How is a tick bite diagnosed?
No tests exist that either identify tick bites or the type of tick once the tick dislodges from the host’s body. However, doctors can examine the entire body, looking for ticks still attached, rashes, or signs of a tick-caused disease. If a tick is identified, the physician can better choose what additional tests should be done because some ticks are likely to transmit certain pathogens. Again, the web citations below have photos of ticks that can help distinguish ticks from biting insects, such as fleas, mites, or bedbugs.
Identification of the tick genus and species may help the physician determine what further tests may be scheduled. For example, blood tests for diseases such as Lyme disease, Rocky Mountain spotted fever, Ehrlichiosis, and tularemia are generally not positive for weeks after the exposure, even though symptoms may be present. Knowledge of the type of tick that caused the bite can help narrow the physician’s possible diagnoses and even allow the physician to proceed with early therapy before a positive diagnosis is made.
Exams and tests should be done if an individual exhibits symptoms after a tick bite. Most tick bites do not have symptoms. If symptoms develop after a tick bite, the determination of which tests need to be performed can be optimized in consultation with an infectious-disease specialist.
What are the symptoms and signs of diseases transmitted by ticks?
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 example, erythema migrans (a rash that is occasionally resembles a “bull’s eye”) is often the first sign of Lyme disease transmitted by a tick bite. Other symptoms can include weakness, nausea, fever, vomiting, palpitations, rash, joint pain, swelling, numbness, and confusion. This is not an all-inclusive list, and other symptoms and signs can develop depending on the pathogen transmitted by the tick bite. More than one disease may be transmitted with tick bites; for example; some individuals may be infected with Lyme disease and babesiosis at the same time.
What is the treatment for a tick bite?
For all tick bites, local cleansing and antibiotic cream may be applied. If the bite area develops itching, preparations containing diphenhydramine (Benadryl) are recommended. These Benadryl compounds can be applied directly to the skin for itching or administered orally by tablets. This is usually the only treatment needed.
However, treatment of the pathogens that the tick may pass to a person depends on other factors, such as the type of tick, length of time of attachment to the host, diseases in the community, and symptoms developed by the patient. Specific treatment is based on the identity of the pathogen transmitted. For example, oral antibiotics may be prescribed for some patients with tick bites if they live in an area where Lyme disease is endemic. With more significant symptoms, antibiotics may need to be given intravenously and the patient may need to be hospitalized. The best approach to treatment is to diagnose which pathogen has been transmitted to the patient (for example, Borrelia species of bacteria) and then use the specific treatment recommended to reduce or kill the pathogen.
How is a tick removed from the skin?
The following is a step-by-step method that is suggested for safe and effective removal of all types of ticks. Web citations 2 and 3 show a diagram of how to place tweezers to remove a tick.
1- Wear hand protection such as gloves so you don’t spread pathogens from the tick to your hands; use forceps or tweezers to grab the tick at skin level.
2- Grasp the tick firmly with the tweezers as close to the skin as possible without crushing the tick. Apply gentle pulling motion upward until the tick comes free. Twisting or turning the tick does not make removal easier because the mouthparts are barbed; in fact, such actions may break off the head and mouthparts, thereby increasing the chances for infection. The second web citation illustrates the proper removal of a tick.
3- Once the tick is removed, don’t crush the tick because it may release pathogens. Consider keeping it in a tightly closed jar or taped to a piece of paper. Show the tick to the doctor if the person bitten becomes ill after the tick bite. Flush any removed ticks not kept for identification down the toilet or sink.
4- The area of the bite should leave a small crater or indentation where the head and mouthparts were embedded. If portions of the head or mouthparts remain, they may be removed by a doctor.
5- Thoroughly cleanse the bite area with soap and water or a mild disinfectant. Observe the area for several days for development of a reaction to the bite (rash or signs of infection). Apply antibiotic cream to the area as a precaution. Application of an antibiotic to the area may help prevent a local infection but usually does not affect the chance of developing diseases transmitted by the tick.
6- Wash hands thoroughly after handling any tick or instruments that touched a tick. Clean and disinfect any instruments that were used.
Other ways to remove ticks, such as using a hot match head or painting the tick with nail polish, gasoline, or other materials, are not advised. Such treatments can cause the tick to release more fluids back into the bite and increases the chance to transmit disease before the tick releases itself from the skin.