Walking On Volume 6, Issue 6, June 2019 | Page 10

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