Asian longhorn tick, (AKA, East Asian, Scrub or Bush Tick)

Newly Discovered Invasive Tick in the United States

Species:
Haemaphysalis longicornis
Neumann


Asian Longhorn Tick
Comparative size of nymph (left) and adult female (right) on a dime. Photo courtesy of the Centers for Disease Control and Prevention (CDC).

Asian Longhorn Tick
Bottom side of adult female longhorn tick, H. longicornis. Photo courtesy of the Centers for Disease Control and Prevention (CDC).

Description:
Adult ticks in this Genus are relatively small (easily overlooked), inornate ticks with overall light-to-dark brown coloration.  Shape of the female scutum is rounded.  They are without eyes.  The basis capituli is rectangular, and the head region is “bell shaped” due to the wide expansion of the palps, especially palp article 2.  The anal groove is behind the anus.  At the species level, H. longicornus has a 5:5 apical hypostomal dentition, and with palp article 3 each possessing an elevated dorso-median spur (suggesting the appearance of a pair of  “horns”) and a ventral spur that is broadly triangular in the male, and more acutely pointed in the female.  Also see https://www.smsl.co.nz/site/southernmonitoring
/files/NZB/Ha%20longicornis%20Profile.pdf

LST DistributionDistribution:
This tick is known from Asia, Japan, Australia, New Zealand and other locations in Pacific.  As of June 6th 2018 this tick has been found in New Jersey (Hunterdon, Mercer, Middlesex and Union counties), Virginia (Albemarle and Warren counties), West Virginia  (Hardy Co.), Maryland (Washington Co.), North Carolina (Polk Co.), New York (Westchester Co.), Pennsylvania (Centre Co.), and Arkansas (Benton Co.).  It may have entered the U.S. as early as 2013. 

Hosts: Literature includes cattle, sheep, goats, horses, pigs, deer, rabbits, opossums, rodents, kiwi, wallabies, dogs, cats, humans, and a variety of birds.  To-date in the U.S. known hosts include cattle, horse, sheep, goat, white-tailed deer, opossum, raccoon and dog.

Biology: Haemaphysalis longicornis is a 3-host tick found in wide-ranging climates from tropical to semi-arid.  It is capable of behavioral diapause through the life stages enabling it to occupy and survive in a wide range of climatic zones.  It also has the capacity to reproduce without male ticks, a process called parthenogenesis.  Though this tick has not been studied in the Western Hemisphere, ecological studies of tick activity in New Zealand indicate seasonal peaks occur for each of the developmental stages and there is evidence that in some locales it may produce more than one generation per year.

Primary Associated Disease Pathogens in the Eastern Hemisphere (US associations not established):

Similar Species: In the U.S., Haemaphysalis leporispalustris is associated with rabbits and H. cordeillis with birds.  These ticks can be separated from H. longicornis by differences in hypostomal dentition, structures on palp article 3, basis capituli and coxal spurs.