Another bumper crop year for ticks

"Yes, they are every bit as monstrous, scary and potentially dangerous as you were afraid they might be. Better to stay safe inside, binging on Netflix with a fat bowl of Cheetos and a 2 liter bottle of Mountain Dew. On the other hand, if you're not the sort to spend all your free time boxed in a room staring at a screen—if the out-of-doors calls you—what might you like to know about…ticks?" These last paragraphs were lifted from a piece I wrote on tick biology back in 2020. But since this year's tick season is proving to be especially bad—last week, Deb and I each pulled three ticks off our skin—I thought it might be helpful to offer a mini-refresher course on these irritating and potentially dangerous parasites. Ticks are not insects but arachnids and like most other members of that group (such as spiders, scorpions and mites), adult ticks have four pairs of legs and a pair of specialized mouthparts called chelicerae. In spiders, the chelicerae are hollow, poison injecting fangs but that's not at all how tick chelicerae work. Worldwide, there are some 900 species of ticks, about 700 of which are the "hard ticks" (Family Ioxididae) and the remainder are the "soft ticks" (Family Argasidae). As their name suggests, the pumpkin seed-shaped hard ticks, including Ohio's three most medically important (to humans) species—the American dog, black-legged (or deer), and lone star ticks—have a hard plate on their upper surface called a scutum. In males, the scutum covers almost the entire back, but in females it looks more like a short bib just in back of a head-like structure called the capitulum. Among other differences, soft ticks have a leathery body (without a scutum), but from here on, we'll focus on hard ticks since they are the forms most often encountered in our area and are the ones most likely to transfer pathogens to humans. If, out of morbid curiosity, you were to look through a hand lens at the capitulum at the front end of one of these ticks, you'd see a pair of barrel-like structures pressed tightly to a strip of something in between. These are the palps. It's their job is to protect the feeding structures until the tick is ready to dine, at which point they rotate off to the side revealing the chelicerae, which look all the world like a pair of harpoons covered with backward-pointing hooks. And instead of acting as fangs (as in spiders) they start jackhammering their way into the skin. For a fascinating and totally creepy video on the how ticks feed, take four minutes to view a YouTube video with the great title, "How ticks dig in with a mouth full of hooks." Once far enough in, a straw-like structure, the hypostome, extends into the blood from between the chelicerae which now serve to anchor the mouthparts to the skin for the several days it takes the tick to obtain a full meal. Hard ticks go through three stages after hatching from an egg—the larva, nymph and adult—each of which needs to obtain a blood meal before metamorphosing into the next phase. In most species, an individual tick will parasitize a different host during each stage of its life. We typically hear a fair bit about deer (black-legged) ticks of wooded and brushy habitats because of their association with the bacterium causing Lyme disease. Nationwide, over 63,000 confirmed cases were reported to the CDC in 2022, although other data suggests over 475,000 people receive treatment for the disease (whether or not they actually had it) each year. While deer ticks and Lyme disease have been increasing in Ohio, only 80 cases had been reported for 2024 to the Department of Health as of May 9 of this year, mostly from the eastern and southeastern counties. Throughout the State (and most places east of the Rockies) American dog ticks are the most commonly encountered tick. They live in areas of tall grass and in clearings with little tree cover. While feeding on mice as larvae and nymphs, the adult stage prefers to parasitize dogs, although they will readily feed on other medium and large mammals, including us, as opportunity allows. They are the principal vector of Rocky Mountain spotted fever, which can be fatal if not treated soon enough. The U.S. sees 250-1,200 cases each year mostly in the Southeast and South-Central states. Ohio reported 27 cases last year. But here's the thing: Ticks don't go dormant when it gets cold. With the mild winters we've been seeing—and are likely to continue experiencing—they have more opportunity to breed and build up their populations, so that by the spring and summer, we've got another bumper crop of the little beggars to deal with.