COMMON NAME: Blacklegged/deer/bear tick
SCIENTIFIC NAME: Ixodes scapularis Say
CLASS/ORDER/FAMILY: Arachnida/Acari/Ixodidae
METAMORPHOSIS: Simple


INTRODUCTION

The common name blacklegged refers to their dark legs which are in contrast to the paler body and that of deer because the preferred adult host is the white-tailed deer; in the midwest, it is called the bear tick. This tick is of medical importance because it is an important vector of Lyme disease. Blacklegged ticks are found primarily in the northeastern, midwestern, and southeastern states in the United States, but extend into Mexico. In error, this tick was described in 1979 as the new species Ixodes dammini by Spielman, Clifford, Plesman & Corwin; this error was corrected by Olivier, Jr., et. al. in 1993.

RECOGNITION

Unengorged female about 118" (2.7 mm) long, male smaller (about 1/16"12 mm). Body oval, dorsoventrally flattened (top to bottom), not hard-shelled. Color orangish brown except legs, mouthparts and scutum (dorsal shield just behind mouthparts) dark reddish brown but abdomen darker when engorged; male body reddish brown overall. Scutum present, longer than wide, almost completely covering dorsum in male. Eyes lacking. Capitulum (mouthparts and their base) visible from above; hypostome (toothed median mouthpart) with apex sharply pointed. Coxa I (1st pair of legs) with internal spur (projection from coxal base) overlapping coxa II (2nd pair of legs). Abdomen with anal groove in front of anus; lacking abdominal festoons (rectangular areas divided by grooves along posterior margin).

Unengorged 1st instar larvae about 1/32" (0.7-0.8 mm) long, with 6 legs; 2nd instar nymphs about 1/16" (1.1-1.8 mm) long, with 8 legs.

SIMILAR GROUPS

(1) Pacific/western blacklegged tick (Ixodes pacificus) with scutum (dorsal shield) almost round (subcircular); (2) Other ixoda ticks (non-Ixodes) with anal groove either behind anus, indistinct, or absent, festoons often present; (3) Soft ticks (Argasidae) lack a scutum (dorsal shield), with capitulum (mouthparts and their base) ventral, not visible from above.

BIOLOGY

Although the life cycle (egg to egg) can be completed in 2 years in nature, it may be extended to 4 years it hosts are scarce. Adult ticks feed during the winter primarily on the white-tailed deer, Odocoileus virginianus (Zimmermann). Here they mate, with the male dying shortly after mating and the female remaining on the host. In the spring, the female drops off the host and deposits about 3,000 eggs. The 6-legged larvae hatch out in several weeks (48-135 days) and can be found June through September. They feed for 3-9 days but only once, usually on small mammals such as mice, chipmunks, voles, etc. but the preferred larval host is the white-footed mouse, Peromyscus leucopus Rafinesque. Larvae feeding before September molt promptly and overwinter as 8-legged nymphs; those which feed later, overwinter engorged and molt into nymphs the following spring. Nymphs feed for 3-8 days but only once during the summer, usually on mice or larger mammals such as squirrels, raccoons, opossums, skunks, dogs, and humans, or on birds. Nymphs can be found from April through August, with the population usually peaking in June or July. These fed nymphs then require 25-56 days to molt into adults in the autumn. The adults attach primarily to the white-tailed deer, engorge, and mate. The male dies after mating but the female continues to feed until egg development is completed and remains on the deer until spring when she drops off to lay eggs. Shortly after her eggs are laid, the female dies.

If adults do not feed during their first season (autumn through spring), they die before summer's end. If nymphs do not feed their first season (summer), most die off but they can survive through 2 seasons (May through August of the next year); they develop into adults in the same year in which they feed. Unfed larvae survive less than one year, they usually survive the winter but die during the following year.

Lyme disease is caused by the spirochete, Borrelia burgdofferi Johnson, Schmid, Hyde, Steigerwalt & Brenner, which is a corkscrew-shaped bacteria. Its primary wild reservoir is the white-footed mouse which is infected by the spring-feeding, pathogen-infected blacklegged/deer tick nymphs. These white-footed mice then serve to infest the later-feeding blacklegged/deer tick larvae, which keeps the disease cycle going. Tick eggs don't contain the spirochete, so it is acquired via feeding.

It is the pathogen-infected blacklegged/deer tick nymphs, which are most active in mid-summer (May-July) and use a wide variety of hosts, that are primarily responsible for Lyme disease in humans in the northeast and midwest. Larvae and nymphs have been collected on 29 species of mammals in 7 orders, and from 49 species of birds (23 species being migratory birds) in 17 different families.

In the west, the primary Lyme disease vector is the Pacific/western blacklegged tick, Ixodes pacificus Cooley and Kohls, while in the south the vector(s) is suspected to be the lone star tick, Amblyomma americanum (Linnaeus).

HABITS

Blacklegged/deer ticks climb grass and shrubs to wait for a passing host, and move very little laterally. They concentrate on such vegetation located in transitional areas/zones such as where forest meets field, mowed lawn meets unmowed fence line, a foot/animal trail through high grass or forest, etc.Because these transitional areas or edge habitats are where most animals travel sometime each 24-hour period, this is where the ticks are mostly likely to acquire a host.

The other habitat most likely to harbor ticks is the den, nest, or nesting area of its host such as that of skunks, raccoons, opossums, but especially the white-footed mouse. The white-footed mouse prefers woody or brushy areas. It nests in any place that gives shelter such as below ground, in stumps, logs, old bird or squirrel nests, woodpiles, buildings, etc.

A favorite feeding area for these ticks on humans is at the back of the neck, at the base of the skull; long hair makes detection more difficult. However, the ticks will usually wonder about for up to 4 hours or so before they attach. Then, a tick has to be attached for a period of 6-8 hours before a successful transmission can take place.

CONTROL

The reduction of these ticks is a 6-step process. The first 2 are sanitation and personal protection, which are the responsibility of the homeowner or occupant(s) but usually require education by the PCO.

1. Sanitation, consists of the following: (a) keep grass cut low including around fence lines, sheds, trees, shrubs, swing sets and other difficult to cut locations; (b) remove weeds, woodpiles, and other debris which are attractive to mice as nesting areas, and leaf litter which is attractive to ticks, especially the nymphs; (c) keep garbage can lids on tightly to discourage opossums, raccoons, and skunks from coming into the yard to raid garbage cans for food because these animals all harbor the ticks which transmit the Lyme disease pathogen; (d) discourage feeding birds because the seeds attract deer mice, the major reservoir host for the Lyme disease pathogen; and (e) install a chimney screen to keep squirrels, raccoons, and birds away.

2. Personal protection, consists of: (a) use deet or permethrin containing repellent and tuck pants into socks or boots when going into suspect areas; (b) check children for ticks when they come into the house because it takes up to 4 hours, possibly longer, for the tick to start feeding; (c) wear light colored clothing which makes spotting ticks easier; (d) pets which go outdoors may increase the chance of the occupant's encounter with these ticks, especially cats; and (e) encourage the vet to check any pet's blood to determine if they are carrying the Lyme disease spirochete.

3. Inspection, is done by performing a tick drag on a routine basis in areas where the ticks have been reported or for homes adjacent to heavily wooded or uninhabited areas. The drag consists of light colored heavy duty cloth, 7 feet long by 2 feet wide, which is securely weighted at both ends. A rope is attached to one end and this drag is walked around the suspect property.

4. Treat the perimeter of the property or the entire property with an appropriately labeled pesticide if ticks show up on the drag. Wettable powder and microencapsulated formulations work best.

5. Do an exterior perimeter rodent control program using PVC pipe with a glue board placed inside.

6. Use the product which has cotton balls treated with a residual pyrethroid placed inside open cylinders as per label directions. The cotton is harvested by mice as a nesting material and when ticks come in contact with it, they die.

LYME DISEASE

The symptoms are usually divided into 3 stages, and they mimic several different commonly occurring diseases.

Symptoms: Spreading rash, fever, flu-like symptoms, aches.

1. Stage 1: Expanding rash (Erythema migrans or EM rashes). 3-30 days after bite.

o Ringlike/bullseyelike appearance to rash.
o One or more rash sites.
o May or may not have flu symptoms.
o May come and go or persist.

2. Stage 2: Complications or disorders of the heart or nervous system.

o Heart. Varying degrees of blockage of the heart muscle.
o Nervous system. Meningitis, encephalitis, facial paralysis.
o "Bell's palsy," other conditions involving peripheral nerves.
o Migratory pain in joints, tendons, muscles, and bones, often without joint swelling or redness.

3. Stage 3: Months to years after disease onset.

o Arthritis that appears and disappears intermittently for several years.
o Enlarged knee joints.
o Erosion of cartilage and bone.

Treatment notes:

1. Once bitten by a blacklegged/deer tick possessing the spirochete, it may not produce antibodies in the victim for up to 6 weeks. Therefore, it takes time to verify that one has Lyme disease.

2. Oral medications for Lyme disease can destroy the spirochetes in the blood and give an antibody reading that the person is "cured." However, the spirochete may persist in the brain and reappear in the person 5-10 years later. Therefore, intravenous treatment is advised over oral medications by some physicians considered experts in this area, especially for persons showing Stage 2 and Stage 3 symptoms.

Tick Removal:

1. The best way to remove a tick found attached to a person or pet is to firmly grasp it with a pair of tweezers as close to the skin as possible.

2. Pull firmly but gently backwards until the tick pulls free.

3. Do not touch the tick, but save it in rubbing alcohol for later identification.

Epidemiological Notes:

1. Epidemiologists have isolated an unidentified type of spirochete from ticks collected in southeastern Missouri which appears to be different from Borrelia burydofferi.

2. Initial studies show that infection by this "new/different" spirochete can result in the expanding rash (EM) but that it is less often followed by multiple skin lesions than with Lyme disease.

3. Therefore, more than one species of tick may be the vector. It is best to characterize the Missouri victims as suffering from a "Lyme-like" illness rather than Lyme disease.

Information about Pests ©2002 - NPMA All rights reserved.
National Pest Management Association Inc.,
8100 Oak Street, Dunn Loring, VA 22027
(703) 573-8330, (703) 573-4116 Fax

 

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