East Asian Longhorned Tick
The longhorned tick (Haemaphysalis longicornis), widely known as an invasive species in New Zealand and Australia, has now made an appearance in the U.S. Although believed to have been in the U.S. since around 2010, it has only recently been “rediscovered” in 2017 on a farm in New Jersey. Since then, there have been additional confirmed sightings in West Virginia, Virginia, Maryland, North Carolina and Arkansas.
While not much is known about this species of tick and how it behaves in the U.S., this three-host tick tends to prefer livestock such as cattle, sheep and horses, however has been known to also bite humans, especially those tending livestock. As larvae and nymphs, as with many ticks, Longhorned ticks tend to prefer birds and small mammals such as white-footed mice.
Most commonly found in the habitats of white-footed mice as well as livestock, Longhorned ticks are predominantly found in meadows and surrounding grassy areas and pastures located near forests.
Like all hard ticks, Longhorned tick larvae emerge from eggs laid in the soil and have three active developmental stages. 6-legged larvae, 8-legged nymphs, and 8-legged adults, all feeding exclusively on vertebrate blood. Also as with most ticks, they move on and off hosts as many as two to three times, as the blood meal is a necessary preamble to molting to the next stage and eventually for egg development. The invasive form of the Longhorned tick is parthenogenic (females lay viable eggs without mating), and so males are extremely rare.
Adult females can easily lay up to ~2,500 eggs, with higher egg counts in parthenogenetic females. The eggs hatch into larvae in late summer-early fall, then larvae crawl onto the grass to quest and attach to passing hosts, feeding on blood for 3-5 days. Afterwards, they drop off the host onto the pasture, where they molt to become a nymph and then become inactive during the winter.
During springtime, nymphs become active again, find a new host on which to attach and feed on for 5-7 days, drop off and molt to adults, which are still relatively small (~2 mm). Adults attach to a host, feed for 7-14 days, by which time they are the size of a pea (10 mm), then drop off and digest the blood as they develop eggs. The females lay the eggs (completing the life cycle) and die.
Pathogens of human and veterinary medical importance that has clearly been shown capable to transmit or repeatedly found infected with, and the associated parts of the world, include:
• Sheep theileriosis (veterinary)
• Canine babesiosis (veterinary)
• Babesiosis (veterinary)
• Anaplasmosis (veterinary)
• Ehrlichiosis (veterinary)
• SFTSV (human, veterinary)
• JSF (human)
• Powassan (human)
• HYSV (human)
The Longhorned tick is a confirmed transmitter of bovine theileriosis and parasites that cause babesiosis infection in animals. Bovine theileriosis can reduce dairy production on cattle farms and occasionally kill calves. The ticks themselves can also cause anemia in sheep and cattle when densities are high.
In Asia, field-collected Longhorned ticks can harbor pathogens that are also present, or very closely related to those found in the US. These include Anaplasma phagocytophilum, Ehrlichia chaffeensis, Babesia, and Powassan virus.
The capacity of this tick to act as a vector for these pathogens to humans has not been studied enough to make a definitive determination as to whether or not the tick is considered a viable transmission vector. This species is also considered a possible vector for Thrombocytopenia Syndrome Virus (SFTSV) in China, an emerging infectious disease with a reported human mortality rate of up to 12%.
Important Note: As of July 2018, NONE of the Longhorned ticks collected in the U.S. have tested positive for any pathogens that effect either humans or livestock.
There are also a few pathogens that have been recovered from collected Longhorned ticks, but only rarely, such as Anaplasma ovis, Anaplasma marginale, Anaplasma platys, Ehrlichia ewingii, Ehrlichia canis, Bartonella sp., Rickettsia sibirica, Orientia tsutsugamushi, TBEV and Hepatozoon canis.
The longhorned tick (Haemaphysalis longicornis), is naturally endemic to Asia (China & Japan primarily), and is also widely known as an invasive species in New Zealand and Australia. It has now also made an appearance in the U.S., and although they are believed to have been in the U.S. since around 2010, it has only recently been “rediscovered” in 2017 on a farm in New Jersey. Since then, there have been additional confirmed sightings in West Virginia, Virginia, Maryland, North Carolina and Arkansas.