For the Health of It
Asian Longhorned Tick
(Haemaphysalis longicornis):
Challenges from an Invasive Ixodid Tick
Reprinted with permission from Equine Disease Quarterly, Volume 27, Number 4
Asian longhorned ticks (ALT) have small, red-
dish-brown bodies with no distinctive markings to fa-
cilitate quick recognition. In addition, unfed adults are
smaller (3 to 4 mm long) than the familiar commonly
encountered hard ticks. The initial confirmed identi-
fication of ALT in the USA was based on specimens
collected from a heavily-infested sheep in New Jersey
in 2017. This was thought to be the first detection of a
new tick species in the USA in 50 years. However, sub-
sequent investigation revealed that specimens removed
from a dog in New Jersey in 2013, which were initially
identified as the
native rabbit tick
Haemaphysalis
leporispalustris,
were also ALT.
Consequently,
the species has
been present for
several years and
has spread. As
of August 2018,
this invasive tick
has been found in at least one location in Arkansas,
Connecticut, Maryland, New Jersey, New York, North
Carolina, Pennsylvania, Virginia, and West Virginia
(Figure 1). Reported hosts have included cattle, a dog,
a horse, an opos- sum, and white-tailed deer.
Native to China, Korea, and Japan, the ALT became
established in Australia and New Zealand, where it
feeds on a variety of wild and domestic animals and
humans. This species does best in moist, warm envi-
ronments. However, it can withstand temperatures
from its developmental threshold of ~12oC to a lethal
high temperature of 40oC. Adults and particularly lar-
val stages of the species appear to have a relatively low
tolerance of dehydration, which may play an important
role in its ultimate distribution in the USA.
The ALT is a three-host tick with a life cycle that
10 • Walking On
takes about a year. While males and females occur in
approximately equal numbers over its
native habitat, very few males have been found in
the USA. Apparently, parthenogenesis (female repro-
duction without the need of fertilization by a male) is
a significant feature of its biology in the USA (Figure
2). Females can deposit about 2,000 eggs, all females,
so local populations can grow rapidly following es-
tablishment. This can result in significant blood loss
and stress to infested hosts. While the initial intro-
duction(s) of this tick is unknown, genetic mapping
has identified three mitochondrial DNA lineages. This
points to at least three distinct females lineages. Par-
theno- genesis would allow relatively rapid selection
for biotypes in response to environmental factors in its
new habitat.
Collections of ALT from sheep in China in- dicate
the ears and periocular areas are preferred attachment
sites. Specimens collected and tested in the USA have
not been shown to carry any diseases, but ALT are
competent disease vectors in Asia contributing to thei-
leriosis and babesiosis in cattle in Australia and New
Zealand and anaplasmosis in Korea. Severe fever with
thrombocytopenia syndrome (SFTS) is an emerging
hemorrhagic fever in East Asia caused by SFTS virus
(SFTSV), a newly discovered phlebovirus. The Haema-
physalis longicornis tick has been suspected to be the
vec- tor of SFTSV. Time will tell the story of its vector
potential in North America. Preserved specimens of
suspected Asian longhorned ticks should be sent to the
National Veterinary Services Laboratories in Ames,
Iowa for identification.
CONTACT:
Lee Townsend, MS, PhD
ltownsen@uky .edu, (859) 257-7455
Department of Entomology
University of Kentucky Lexington, KY