Sunday, September 9, 2018

Invasives: A New Tick Species Is Spreading

longhorned tick courtesy wikimedia user CommonsourceYears ago I read an author interview, and although I don’t recall her name, one of the images she raised has stayed with me. It’s not an exact quote, but she said something to the effect that writing ought to feel to an author as if they were water skiing behind their work, not towing it like a barge. In general, I find this to be the case. The hours or days of research which go into an article are hardly exhilarating, but the wave-jumping that comes after shrinking those pages of facts into 800 words makes it worth the effort.

However, when I tried to water-ski behind a brand-new invasive tick that can reproduce without mating, drain the blood out of livestock, and potentially carry ten or more human diseases, including one similar to Ebola, something changed. A few topics whip across the water at high speed. Most at least pull me at a leisurely pace. This one made me drop the whole water skiing idea and swim for my life. Turns out there is a limit to how many miles you can get out of happy imagery. 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 commonly called the Asian longhorned tick, or simply the longhorned tick, which is confusing since a number of invasive wood-boring beetles also bear the name “longhorned.” Native to parts of Central and East Asia, as well as to Fiji, New Zealand, Australia, Hawaii and other Pacific islands, it was first identified in North America in November 2017 in Hunterdon County, New Jersey. A lone pet Icelandic sheep had been critically weakened from blood loss due to the estimated thousand longhorned ticks which were found attached.

How the tick arrived in New Jersey remains a mystery, since the sheep had reportedly never been off the manicured, upscale property, but birds sometimes give ticks free air miles. Within a few months, authorities had confirmed it in several other states, and as of September 2018, it is believed to be in nine states total, including New York, where it has been found in Westchester County. While US Customs officials had occasionally found the longhorned tick on quarantined animals as long ago as 1969, this is the first time it has been found in the wild in North America. Given how far it has already spread, experts believe it has been here several years, perhaps as far back as 2013.

It is fairly nondescript, being light to dark brown, and lacking any visible “longhorns,” which can only be seen under magnification. It is also tiny, roughly the same size as the blacklegged or deer tick, and only half as big as a dog or wood tick. It is more rounded in outline than the deer tick, though, and a bit more textured. A Texas A&M University fact sheet offers these helpful details: “H. longicornus has a 5:5 apical hypostomal dentition, and with palp article 3 each possessing an elevated dorso-median spur.” On second thought, a web-image search might be better.

To be fair to the longhorned tick — which is more than it deserves — it is not at this time known to carry human pathogens here on this continent. In its home range it does transmit several species of Borrelia spirochete bacteria known to cause Lyme disease, as well pathogens which cause Babesiosis, spotted- fever rickettsia, Erlichiosis, Anaplasmosis, Khasan virus, Powassan virus and at least two 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 carried by the longhorned tick in its native area.

Another “good” point is that humans to not appear to be one of its primary hosts. 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 the ticks which hatch out are females as well, a reproductive strategy known as parthenogenesis.

Apparently, longhorned ticks may even have more than one generation per year.

The fact that female longhorned ticks can churn out young without the fuss of Tinder or Craigslist 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 be effective in reducing tick populations greatly. Pets should be treated for ticks from April through December, and during unseasonably warm winters too. For help identifying ticks found on humans, contact your nearest Health Department or Extension office.

It is no fun writing about bad news, but there are times when knowing is important. Spend time 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.

Photo of longhorned tick courtesy Wikimedia user Commonsource.

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A Canton, NY-based arborist, educator and writer, Paul Hetzler had intended to be a bear when he grew up, but failed the audition. He settled for an educator position instead, and serves as Horticulture and Natural Resources Educator at Cornell Cooperative Extension of St. Lawrence County.

His work has appeared in the medical journal The Lancet, as well as Highlights for Children Magazine. He is the author of Shady Characters: Plant Vampires, Caterpillar Soup, Leprechaun Trees and Other Hilarities of the Natural World.

You can reach Paul at the Cornell Cooperative Extension office in Canton at (315) 379-9192.




2 Responses

  1. Wally Elton says:

    Hoping for a very cold winter!

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