PACIFIC WESTERN BLACKLEGGED TICK PHE

  1. INTRODUCTION
    This tick receives the common name Pacific because it is found in the Pacific Coastal states, that of blacklegged from having black legs in contrast to a reddish brown body, and western because it is only found in the western United States. Although not a structural pest, this tick is of medical importance as the prime vector of Lyme disease in the west, and transmits the agent for human granulocytic anaplasmosis (HGA).”
  2. Distributed in the Pacific Coast states from British Columbia, Canada and into Mexico, but also in Arizona, Nevada, and central and western Utah.
  3. RECOGNITION
    Unengorged adult female about 1/8" (2.64 mm) long, male about 1/16" (2.2 mm); engorged female up to 3/8 (9 mm) long, 1/8" (3 mm) wide. Body oval, dorsoventrally flattened (top to bottom), not hard-shelled. Color reddish brown with black legs, capitulum (mouthparts and their base), and scutum (dorsal shield), becoming dull gray when engorged. Scutum (dorsal shield just behind mouthparts) restricted to front half of dorsum in female and almost round (subcircular), almost completely covering dorsum in male. Eyes lacking. Capitulum (mouthparts and their base) visible from above, hypostome (toothed median mouthpart) with apex blunt. 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).
  4. Unengorged 1st instar larvae about 1/64" (0.5 mm) long, with 6 legs; 2nd instar nymphs about 1/32" (1 mm) long, with 8 legs.
  5. SIMILAR GROUPS
    (1) Blacklegged/deer/bear tick (Ixodes scapularis) with scutum (dorsal shield) longer than wide.
  6. (2) Other ixodid ticks (non-Ixodes) with anal groove behind anus, indistinct, or absent, festoons often present.
  7. (3) Soft ticks (Argasidae) lack a scutum and with capitulum (mouthparts and their base) ventral, not visible from above.
  8. BIOLOGY
    The following data are from ticks reared in the laboratory on guinea pigs at about 64-68°F (18-20°C) and about 90% RH. Female ticks feed for about 10-11 days. Then the engorged female drops off the host and seeks a sheltered place to lay her eggs. After an 11-16 day preoviposition period, she begins and continues to lay eggs for about 33-40 days; total eggs laid ranges from 355-1,301. Egg hatch occurs in about 53-57 days. Larvae feed for about 4-10 days, detach, and molting requires 37-38 days (range 30-61 days). Nymphs feed an average of 9 days (range 7-11 days), and about 30 days are required to molt into adults. The life cycle (egg to egg) requires about 7 months. Females die within 3-4 months if unfed.
  9. The Pacific tick is the primary vector of Lyme disease (caused by the spirochete bacterium Borrelia burgdorferi) in the western states, and transmits the agent for human granulocytic anaplasmosis (HGA); see this section on the blacklegged/deer/bear tick (3.20.3-4) for a detailed description of Lyme disease. They have been found on 55 different host species of which 40 species were mammals, 6 species were birds and 9 species were lizards. Of the mammal hosts, most were found on humans with dogs a close second, and deer and cattle were the next most often attacked. The Pacific tick also transmits the agent for anaplasmosis or human granulocytic anaplasmosis/HGA which is caused by the bacterium Anaplasma phagocytophilum.
  10. HABITS
    Larvae and nymphs of this tick feed primarily on lizards such as the western fence lizard, Sceloporus occidentalis Baird and Girard, but will occasionally attack small warm-blooded mammals, such as deer mice, Peromyscus maniculatus (Wagner), and pinion mice, P. truei (Shufeldt). The adults prefer medium to large-bodied mammals such as humans, deer, dogs, cats, horses, cattle, and sheep; the primary deer is the Columbian black-tailed deer, Odocoileus hemionus (Rafinesque).
  11. The larvae and nymphs attach almost exclusively to the lateral nuchal pockets of the lizards. However, lizards have not been found carrying the Lyme disease spirochete but the infection rate could have been too low to be detected. Hence, the small mammals probably serve as the main spirochete reservoir.
  12. Adult females are found year round but more commonly in the spring and again in the late summer. Larvae are found primarily in the spring. Nymphs also are found primarily in the spring but also into the late autumn. As a rule, these ticks are usually not found during the dry summer period or only in very low numbers.
  13. Great care should be exercised when removing embedded ticks because their long mouthparts make removal difficult. The mouthparts are often broken off during removal which typically results in secondary infection.
  14. PACIFIC WESTERN BLACKLEGGED TICK
    the prime vector of BLANK in the west, and transmits the agent for human granulocytic anaplasmosis (HGA).
    Lyme disease
  15. PACIFIC WESTERN BLACKLEGGED TICK
    the prime vector of Lyme disease in the west, and transmits the agent for BLANK
    HGA
  16. PACIFIC WESTERN BLACKLEGGED TICK
    Of the mammal hosts, most were found on
    humans with dogs a close second, and deer and cattle were the next most often attacked.
  17. PACIFIC WESTERN BLACKLEGGED TICK
    Larvae and nymphs of this tick feed primarily on
    lizards such as the western fence lizard, Sceloporus occidentalis Baird and Girard, but will occasionally attack small warm-blooded mammals, such as deer mice, Peromyscus maniculatus (Wagner), and pinion mice, P. truei (Shufeldt).
  18. PACIFIC WESTERN BLACKLEGGED TICK
    The adults prefer medium to large-bodied mammals such as
    humans, deer, dogs, cats, horses, cattle, and sheep; the primary deer is the Columbian black-tailed deer, Odocoileus hemionus (Rafinesque).
  19. PACIFIC WESTERN BLACKLEGGED TICK
    The larvae and nymphs attach almost exclusively to the
    lateral nuchal pockets of the lizards.
  20. PACIFIC WESTERN BLACKLEGGED TICK
    However, lizards have not been found carrying the Lyme disease
    spirochete but the infection rate could have been too low to be detected.
  21. PACIFIC WESTERN BLACKLEGGED TICK
    Hence, the small mammals probably serve as the main
    spirochete reservoir.
  22. PACIFIC WESTERN BLACKLEGGED TICK
    Adult females are found year round but more commonly in
    the spring and again in the late summer.
  23. PACIFIC WESTERN BLACKLEGGED TICK
    Larvae are found primarily in the
    spring.
  24. PACIFIC WESTERN BLACKLEGGED TICK
    Nymphs also are found primarily in the spring but also into the late
    autumn.
  25. PACIFIC WESTERN BLACKLEGGED TICK
    As a rule, these ticks are usually not found during the
    dry summer period or only in very low numbers.
Author
ianquinto
ID
351390
Card Set
PACIFIC WESTERN BLACKLEGGED TICK PHE
Description
PACIFIC WESTERN BLACKLEGGED TICK PHE
Updated