Blacklegged Tick or Deer Tick – Ixodes scapularis

Blacklegged Tick or Deer Tick – Ixodes scapularis
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Class Arachnida / Order Ixodida / Family Ixodidae.  The blacklegged tick transmits the bacteria that causes Lyme disease. "As global temperature rises, so does the risk of Lyme disease." [3]
Blacklegged Tick or Deer Tick
According to the Centers for Disease Control, Lyme disease is now the most common vector-borne infection in humans in the United States. More than 16,000 cases of Lyme disease were reported to the CDC in 1999. Ninety-two percent of these were from the New England states. Some years the numbers are not as high, but according to the CDC Lyme disease is under-reported. Since its discovery in 1975, cases have been reported from Canada, Europe, Australia, Asia, and the USSR. Lyme disease has been reported in domestic animals, including dogs, horses, and more recently, cattle [2].

Borrelia burgdorferi, the bacteria causing Lyme disease is maintained in nature in I. scapularis and I. pacificus ticks and certain host species, chief of which is the white-footed mouse. A few bird species are also thought to be reservoir hosts. Crucial to maintenance of the cycle of B. burgdorferi between I. scapularis and reservoir hosts in the northeastern U. S., is the appearance of host-seeking nymphs (the second feeding stage) of one generation in late spring followed 2 months later by the host-seeking larvae (first feeding stage) of the next generation.

Thus, infected nymphs infect mice in May and June, and in July uninfected larvae of the next tick generation acquire B. burgdorferi from the recently infected mice. Uninfected nymphs can be infected by feeding on infected mice, and maintain the infection into the adult stage. Most adult I. scapularis feed on white-tailed deer which are not reservoir hosts, although important to the tick life cycle. Transmission of B. burgdorferi from an infected female tick to her offspring is apparently extremely limited [1].

"Ötzi the Iceman," a stone-age hunter of 5,300 years ago, discovered frozen in ice in the Alps in 1991, was found by DNA analysis to be suffering from Lyme disease. He was also found to be lactose-intolerant and to have been murdered with a bow and arrow. His is the earliest know evidence of the Lyme disease bacteria Borrelia burgdorferi.

Blacklegged Tick
Adult Blacklegged Tick, also commonly called a deer tick [1,5]

The symptoms of Lyme disease include a round or oval rash at the site of the tick bite. It may be solid red, or have a bull’s-eye appearance. If left untreated, the infection can cause paralysis of the face, severe headaches, neck stiffness (meningitis), heart palpitations, diziness, and intermittent bouts of arthritis with joint pain, inflammation and swelling, especially in the knees.

Lyme disease is often confused with Lupus, a long-term autoimmune disorder that may affect the skin, joints, kidneys, brain, and other organs. Lupus symptoms include many of the same players: fatigue and fever, joint pain, stiffness and swelling, butterfly-shaped rash on the face that covers the cheeks and bridge of the nose, fingers and toes that turn white or blue when exposed to cold or during stressful periods (Raynaud’s phenomenon), shortness of breath, chest pain, dry eyes, headaches, confusion, and memory loss [4].

Tick Life Cycle
Tick Life Cycle courtesy USDA

The blacklegged tick has 3 active life stages (larva, nymph and adult) that feed on a wide variety of vertebrate hosts, including birds and lizards, but larvae feed almost exclusively on white-footed mouse and adults feed on white-tailed deer. Having found a host, larvae and nymphs feed 3-5 days, and adult females about 1 week, then drop off the host. Although the life cycle of I. scapularis is about 2 years, each tick spends only about 2 weeks feeding on hosts. [1]

Engorged Female Deer Tick
Engorged Female Blacklegged Tick [5]
Prevention: Tick bite prevention can include personal protection and reduction of tick populations. Most cases of Lyme disease are the result of persons being bitten by nymphal I. scapularis. The vast majority of host-seeking nymphs and larvae of I. scapularis are found in leaf litter in and adjacent to woods. Nymphs are also frequently found on and about stone fences and fallen logs. Therefore, it is best to limit one's contact with leaf litter, and do not sit on stone fences or fallen logs. Wear light colored clothing so that it is easy to see ticks on it. 

Use repellents. Permethrin-based repellents should be used only on clothing. Deet-based repellents can be used on skin. PBESL in conjunction with the Chemicals Affecting Insect Behavior Laboratory, BARC and Walter Reed Army Institute of Research, Silver Spring, MD are evaluating the efficacy of tick repellents that can be used on human skin. Be careful about long hair that contacts shirt or coat collars. Ticks can crawl from collar to hair undetected. Examine yourself and children for ticks repeatedly after spending time in tick infested areas. You cannot depend on showering to remove ticks, especially attached ticks. Place clothing worn in tick infested areas in a closed plastic bag until washing it. Ticks can survive machine washing with cool water. Unlike mosquitoes, the process by which ixodid ticks feed is slow, lasting a few days. In the case of Lyme disease, 24-36 hours of attachment are needed before transmission of B. burgdorferi starts. Other disease causing agents can be transmitted more quickly.

Attached ticks should be removed as soon as possible. Tick removal: Attached ticks are best removed using forceps (tweezers) with slender points. The tick should be grasped with the forceps as close to the person's skin as possible. Grasping the tick farther from its mouthparts increases the chance of squeezing its gut contents into the person. Pull the tick from the skin slowly and firmly. Wash the bite area and apply a topical antibiotic to it.

Because the early symptoms of many tick-borne illnesses are like those experienced with other ailments, such as the flu, it is prudent to see a physician, if you notice headache, fever, muscle pains, or other symptoms after having had a tick bite. Lyme disease and other tick-borne illnesses caused by bacteria are generally respond to antibiotics, when treatments are started early. It is important that your physician knows about your tick bite. [1]

For details on "chronic Lyme disease" and long term treatment trials sponsored by NIH, visit the NIH Lyme Disease web site. For treatment guidelines developed by the Infectious Disease Society of America, IDSA Guidelines for Treatment of Lyme Disease."

See also
The lone star tick does not transmit Lyme disease
. Patients bitten by lone star ticks will occasionally develop a circular rash similar to the rash of early Lyme disease. The cause of this rash has not been determined; however, studies have shown that it is not caused by Borrelia burgdorferi, the Lyme disease bacterium.

The rash may be accompanied by fatigue, headache, fever, and muscle and joint pains. This condition has been named southern tick-associated rash illness (STARI).


  1. USDA, ARS, Animal Parasitic Diseases
  2. Centers For Disease Control, Learn About Lyme Disease
  3. The National Institutes of Health, National Institute of Allergy and Infectious Disease, Lyme Disease
  4. Mayo Clinic, "Symptoms of Lupus"
  5. Photos: Scott Bauer, USDA ARS,, under Creative Commons Attribution 3.0
Class Arachnida / Order Araneae: Spiders are the largest group of arachnids.  They are easily recognized by their eight legs, and there are few creatures great or small that elicit such irrational fear in mankind. The vast majority of spiders are completely harmless and offer beneficial services, chief of which is keeping the burgeoning insect population in check.
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