Ixodes scapularis

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Ixodes scapularis
Ixodes scapularis.jpg
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Chelicerata
Class: Arachnida
Subclass: Acari
Superorder: Parasitiformes
Order: Ixodida
Family: Ixodidae
Genus: Ixodes
Species: I. scapularis
Binomial name
Ixodes scapularis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Ilan Dock, B.S.

Overview

Ixodes scapularis is commonly known as the deer tick or blacklegged tick (although some people reserve the latter term for Ixodes pacificus, which is found on the West Coast of the USA), and in some parts of the USA as the bear tick.[1] It is a hard-bodied tick (family Ixodidae) of the eastern and northern Midwestern United States. It is a vector for several diseases of animals, including humans (Lyme disease, babesiosis, anaplasmosis, Powassan virus disease, etc.) and is known as the deer tick owing to its habit of parasitizing the white-tailed deer. It is also known to parasitize mice,[2] lizards,[3] migratory birds,[4] etc. especially while the tick is in the larva or nymph stage.

Life Cycle

General Tick Life Cycle

This image displays an example of the tick lifecycle, based on stages and the months that they are most likely to occur during.
  • A tick's life cycle is composed of four stages: hatching (egg), nymph (six legged), nymph (eight legged), and an adult.
  • Ticks require blood meal to survive through their life cycle.
  • Hosts for tick blood meals include mammals, birds, reptiles, and amphibians. Ticks will most likely transfer between different hosts during the different stages of their life cycle.
  • Humans are most often targeted during the nymph and adult stages of the life cycle.
  • Life cycle is also dependent on seasonal variation.
  • Ticks will go from eggs to larva during the summer months, infecting bird or rodent host during the larval stage.
  • Larva will infect the host from the summer until the following spring, at which point they will progress into the nymph stage.
  • During the nymph stage, a tick will most likely seek a mammal host (including humans).
  • A nymph will remain with the selected host until the following fall at which point it will progress into an adult.
  • As an adult, a tick will feed on a mammalian host. However unlike previous stages, ticks will prefer larger mammals over rodents.
  • The average tick life cycle requires three years for completion.
    • Different species will undergo certain variations within their individual life cycles. [5]





Spread of Tick-borne Disease

  • Ticks require blood meals in order to progress through their life cycles.
  • The average tick requires 10 minutes to 2 hours when preparing a blood meal.
  • Once feeding, releases anesthetic properties into its host, via its saliva.
  • A feeding tube enters the host followed by an adhesive-like substance, attaching the tick to the host during the blood meal.
  • A tick will feed for several days, feeding on the host blood and ingesting the host's pathogens.
  • Once feeding is completed, the tick will seek a new host and transfer any pathogens during the next feeding process. [5]

Description

  • When the deer tick has consumed a blood meal its abdomen will be a light grayish-blue color, whereas the tick itself is chiefly black.
  • In identifying an engorged tick it is helpful to concentrate on the legs and upper part of the body
  • Most images of Ixodes scapularis that are commonly available—show an adult that is unengorged, that is, an adult that has not had a blood meal.
  • Ticks are generally removed immediately upon discovery to minimize the chance of disease.
  • However, the abdomen that holds blood is so much larger when engorged and looks so different from the rest of the tick that it would be easy to assume that an engorged specimen of Ixodes scapularis is an entirely different tick (see photo below).

Behavior

  • I. scapularis has a two-year life cycle, during which time it passes through three stages: larva, nymph, and adult.
  • The tick must take a blood meal at each stage before maturing to the next.
  • Deer tick females latch onto a host and drink its blood for four to five days.
  • Deer are the preferred host of the deer tick, but it is also known to feed on small rodents.[6]
  • After she is engorged, the tick drops off and overwinters in the leaf litter of the forest floor.
  • The following spring, the female lays several hundred to a few thousand eggs in clusters.[7]
  • Transtadial (between tick stages) passage of Borrelia burgdorferi is common. Vertical passage (from mother to egg) of Borrelia is uncommon.
  • I. scapularis may be active even after a moderate to severe frost, as daytime temperatures can warm them enough to keep them actively searching for a host.
  • In the spring, they can be one of the first invertebrates to become active.
  • Deer ticks can be quite numerous and seemingly gregarious in areas where they are found.

Ixodes scapularis Transmitted Diseases

  • Co-infections complicate Lyme symptoms, especially diagnosis and treatment.
  • It is possible for a tick to carry and transmit one of the co-infections and not Borrelia, making diagnosis difficult and often elusive.
  • The Centers for Disease Control's emerging infectious diseases department did a study in rural New Jersey of 100 ticks, and found 55% of the ticks were infected with at least one of the pathogens.[12]

Geographic Distribution

  • Northeastern and upper Midwestern United States
Blacklegged tick.jpg

Genome sequencing

Genomic information
NCBI genome ID523
Ploidydiploid
Genome size1,765.38 Mb
Number of chromosomes15 pairs
Year of completion2008
  • The genome of I. scapularis has been sequenced.[13]

Prevention

Limiting tick exposure

Tuck pants into socks

It is unreasonable to assume that a person can completely eliminate activities that may result in tick exposure. Therefore, prevention measures should emphasize personal protection when exposed to natural areas where ticks are present:

  • Wear light-colored clothing which allows you to see ticks that are crawling on your clothing.
  • Tuck your pants legs into your socks so that ticks cannot crawl up the inside of your pants legs.
  • Apply repellents to discourage tick attachment. Repellents containing permethrin can be sprayed on boots and clothing, and will last for several days. Repellents containing DEET (n, n-diethyl-m-toluamide) can be applied to the skin, but will last only a few hours before reapplication is necessary. Use DEET with caution on children. Application of large amounts of DEET on children has been associated with adverse reactions.
  • Conduct a body check upon return from potentially tick-infested areas by searching your entire body for ticks. Use a hand-held or full-length mirror to view all parts of your body. Remove any tick you find on your body.
  • Parents should check their children for ticks, especially in the hair, when returning from potentially tick-infested areas.
  • Ticks may also be carried into the household on clothing and pets and only attach later, so both should be examined carefully to exclude ticks.[14]


The best way to remove a tick

  1. Use fine-tipped tweezers or notched tick extractor, and protect your fingers with a tissue, paper towel, or latex gloves. Persons should avoid removing ticks with bare hands.
  2. Grasp the tick as close to the skin surface as possible and pull upward with steady, even pressure. Do not twist or jerk the tick; this may cause the mouth-parts to break off and remain in the skin. (If this happens, remove mouth-parts with tweezers. Consult your health care provider if illness occurs.)
  3. After removing the tick, thoroughly disinfect the bite site and wash your hands with soap and water.
Tick removal process
  • Do not squeeze, crush, or puncture the body of the tick because its fluids may contain infectious organisms. Skin accidentally exposed to tick fluids can be disinfected with iodine scrub, rubbing alcohol, or water containing detergents.
Removal of an embedded tick using fine-tipped tweezers
  • Save the tick for identification in case you become ill. This may help your doctor to make an accurate diagnosis. Place the tick in a sealable plastic bag and put it in your freezer. Write the date of the bite on a piece of paper with a pencil and place it in the bag. [15]

References

  1. Drummond, Roger (2004). Ticks and What You Can Do about Them (3rd ed.). Berkeley, California: Wilderness Press. p. 23. ISBN 0-89997-353-1.
  2. PMID 7799148 (PMID 7799148)
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  3. PMID 9439111 (PMID 9439111)
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  4. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2268299/
  5. 5.0 5.1 Life Cycle of Ticks that Bite Humans (2015). http://www.cdc.gov/ticks/life_cycle_and_hosts.html Accessed on December 30, 2015
  6. "Westport Weston Health District". 2004. Retrieved 2013-09-26.
  7. Suzuki, David; Grady, Wayne (2004). Tree: A Life Story. Vancouver: Greystone Books. p. 110. ISBN 1-55365-126-X.
  8. Brownstein, John S.; Holford, Theodore R.; Fish, Durland (2005). "Effect of Climate Change on Lyme Disease Risk in North America". EcoHealth. 2 (1): 38–46. doi:10.1007/s10393-004-0139-x. PMC 2582486. PMID 19008966.
  9. McNeil, Donald (19 September 2011). "New Tick-Borne Disease Is Discovered". The New York Times. pp. D6. Retrieved 20 September 2011.
  10. Steere AC (July 2001). "Lyme disease". New England Journal of Medicine. 345 (2): 115–25. doi:10.1056/NEJM200107123450207. PMID 11450660.
  11. G. P. Wormser (June 2006). "Clinical practice. Early Lyme disease". New England Journal of Medicine. 354 (26): 2794–801. doi:10.1056/NEJMcp061181. PMID 16807416.
  12. Varde S, Beckley J, Schwartz I (1998). "Prevalence of tick-borne pathogens in Ixodes scapularis in a rural New Jersey County". Emerging Infectious Diseases. 4 (1): 97–99. doi:10.3201/eid0401.980113. PMC 2627663. PMID 9452402.
  13. Ixodes scapularis genome sequence at VectorBase
  14. General Tick Disease Information. Centers for Disease Control and Prevention (2015). http://www.cdc.gov/ticks/symptoms.html Accessed on December 30, 2015
  15. Tick Removal. Centers for Disease Control and Prevention (2015). http://www.cdc.gov/ticks/removing_a_tick.html Accessed on December 30, 2015

External links

Please read to protect yourself from Deer ticks that may cause Lyme disease. Public Health Fact Sheet: Lyme Disease

Gallery

  • Common name: blacklegged tick, deer tick
  • Scientific name: Ixodes scapularis
  • Reservoir: small mammals and birds (larvae and nymphs); rodents and mammals (adult ticks)
  • Geographic distribution: northeastern and upper midwestern United States
  • Disease transmitted: anaplasmosis, babesiosis, Lyme disease

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