New Tick Species

[Paul J Hetzler]

Water-Skiing With Invasive Ticks

Years ago I read an author interview, and while I don’t recall her name, an image she raised has stayed with me—something to the effect that writing ought to feel as if you were water skiing behind your work. Usually, I find this to be the case. However, when I tried to water-ski behind a new invasive tick that reproduces without mating, drains the blood from livestock, and potentially carries an Ebola-like disease, something changed. A few topics whip across the water. Most pull me at a leisurely pace. But this one made me drop the towline and swim for my life. Turns out there’s a limit to how far a happy image will get you. And to how long a writer should be allowed to spend alone in a room with the same metaphor.

The invasive species, Haemaphysalis longicornis, is called the bush tick or longhorned tick (which is confusing since a few invasive wood-boring beetles also bear the name “longhorned”). Native to parts of Central and East Asia, as well as to New Zealand, Australia, Hawaii and other Pacific islands, it was first identified in North America in November 2017 in New Jersey. A lone pet sheep had been critically weakened from blood loss due to the estimated thousand longhorned ticks which were found attached.

How the tick got there remains a mystery, since the sheep had reportedly never been off the property, but birds can give ticks free air miles. As of this month, it is in eight US states, including NY. Customs officials had occasionally seen the tick on quarantined animals as long ago as 1969, but this is the first time it has been found in the wild. Experts believe it may have been in the US since 2013.

It’s light to dark brown, and lacks visible “longhorns,” which can only be seen under magnification. It is roughly half as big as a dog or wood tick—the same size as a blacklegged or deer tick, but more rounded in outline. A Texas fact sheet offers this helpful tip: “[It] has a 5:5 apical hypostomal dentition, with an elevated dorso-median spur on palp article 3.” OK, a web-image search might be better.

To be fair to the longhorned tick—which is more than it deserves—on this continent it has not yet been proven to carry human pathogens. In its home range it transmits several species of Borrelia spirochete bacteria that cause Lyme, as well pathogens which cause Babesiosis, spotted-fever rickettsia, Erlichiosis, Anaplasmosis, Powassan virus and other types of tick-borne encephalitis. A relatively new illness with symptoms like those of Ebola, called “severe fever with thrombocytopenia syndrome” or SFTS, is also spread by the longhorned tick in its native area.

In the wild it prefers rodents and other small mammals, in addition to deer, bear, canines and hares. In domestic herds it travels fast, and can overwhelm and kill young livestock, and those weakened by internal parasites or other stresses. Female ticks reproduce without mating, laying about 2,000 eggs each after a blood meal. All tick hatchlings are female as well, a strategy known as parthenogenesis.

The fact that female longhorned ticks can churn out young without the fuss of Tinder to find a guy may give them an edge on population growth, but it also makes them vulnerable. The high degree of genetic variation which comes with sexual reproduction is what helps organisms adapt to change. Since longhorned ticks hail from a temperate climate, an extreme cold snap such as February 2013’s “polar vortex” might decimate their numbers without selecting for cold-hardiness in the species.

The public is advised to continue with precautions they already use against deer ticks, especially the use of DEET (20% or stronger) on exposed skin, and the use of permethrin-treated clothes and gear. Since all ticks are ferried by rodents throughout rural, urban and suburban landscapes alike, using tick tubes such as the Damminix brand can help reduce tick populations greatly. Pets should be treated for ticks from April through December, and during unseasonably warm winters too.

It’s no fun writing about bad news, but there are times when knowing is important. Get outdoors often, but keep your eyes peeled, and clothing, exposed skin, and pets treated appropriately. And water ski as much as possible—it remains a tick-free activity.

[Brett Chedzoy]

Thanks for updating us on this latest bad bug, Paul.  I would like to think that this new tick won't reach the crisis levels that native ticks have - but experience suggests otherwise.