Newsletter #173 What use are ticks?

Newsletter about nature and science

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M.P.Gerkema

Jun 15, 2025

What use are ticks?

What a peculiar question—ticks could of course ask the same about us. It’s understandable, though: besides drawing our blood, they also transmit very troublesome diseases, of which Lyme disease by far is the most common for us.

Ticks have been doing exceedingly well on earth for a very long time. A tick was found already on a 99-million-year-old dinosaur feather (entrapped in amber). These arachnids undergo a complex life cycle, from egg to six-legged larva to eight-legged nymph and adult. For their development they usually require blood from three different hosts, although some species make do with just one, as with the cattle tick. We are mainly troubled by the common or sheep tick, which—after feeding on small rodents, hedgehogs, and rabbits—also climbs onto cats, dogs, sheep, deer, wild boar, and humans from tall grass and vegetation. Beware: some 27,000 people in the Netherlands contract Lyme disease each year as a result.

Ticks, together with mites, belong to a separate group of arachnids. They lack the certain elegance of spiders, with their clear division between cephalothorax and abdomen. The front pair of their eight little legs bears an organ that detects changes in CO₂ levels, temperature, and humidity—and thus the presence of a potential host. There are some 900 species of tick worldwide, all dependent on the blood of vertebrates: amphibians and reptiles, but also birds and mammals, often specializing on a particular group, such as turtles. Many ticks drop down from vegetation onto a passing host, while others actively pursue them. The time needed to develop from egg to adult can vary enormously, from one to seven years—and larvae, nymphs, and adults must endure long periods without food (blood). Only nymphs and adults can transmit pathogens, including the corkscrew-shaped bacteria of the genus Borrelia that cause Lyme disease. The disease and the role of ticks in its transmission were described as early as 1764 by the Scottish professor Walker, but the name “Lyme disease” dates from an outbreak in Old Lyme, Connecticut, in 1975. The disease had already been present in Europe; Ötzi, who died in the Ötztal Alps at age 45 some 5,390–5,066 years ago, tested positive for Borrelia DNA. The best-known symptom of Borrelia infection is the red patch (erythema migrans) that appears a few days to a few months around the tick bite; by then the bacterium may already have spread through the body. Moreover, infection can occur without any visible rash. It is therefore important after a tick bite to watch carefully. If a red patch grows, or if one develops joint, skin, or nerve complaints—or fever and heart problems—one should see a general practitioner for an antibiotic course.

The long-term consequences of Lyme disease are serious: the central nervous system is often attacked. Each year in the Netherlands, 1.5 million people are bitten by ticks, 300,000 develop an infection, and 27,000 actually get Lyme disease. The ticks themselves, however, remain largely unfazed. The fact that so many tick species transmit such a variety of parasites seems merely incidental in the long and successful history of these blood-sucking creatures.

Five tips when it comes to ticks (with thanks to the RIVM):

When are you at risk of a tick bite?

Ticks climb up from grasses and shrubs onto animals and people. Stay on paths as much as possible, and avoid tall, shaded grass; dense undergrowth and shrubbery; and dead leaves around trees and bushes. Wear closed shoes, long sleeves, and long trousers; tuck your trouser legs into your socks. Light-coloured clothing makes ticks easier to spot. Wear clothing impregnated with the insect-repellent permethrin or spray your clothes with a repellent containing DEET (diethyltoluamide). Apply DEET-based repellent to exposed skin. Once on a host, ticks seek a suitable spot in the skin to attach: in people these are mainly the groin, backs of the knees, armpits, buttock crease, edges of underwear, behind the ears, and around the hairline at the nape (especially in children).

What to do after a tick bite

Remove a tick (which looks like a flat little spider—if it has already fed, an almost round one) as soon as possible! The longer the tick remains embedded, the greater the chance it will transmit pathogens. Do not apply alcohol, iodine, oil, soap, or other substances before removal. Grasp the tick with fine-tipped tweezers as close to the skin at its head as possible, and pull it out gently. If part of the head remains, that is harmless; it will come out by itself, like a splinter. Only then disinfect the bite site with 70 % alcohol or iodine. If using a commercial tick remover, follow the instructions. You may use a magnifying glass if needed. Note the date of the bite and its location on your body.

Does a red spot after a tick bite mean trouble?

No: a small red spot at the bite site in the first few days afterwards is a normal skin irritation. If it does not enlarge and disappears within a few days, the chance that it is Lyme disease is very small. If the spot enlarges, see a GP.

When according to the RIVM should you definitely see a GP after a tick bite?

A skin discoloration at the bite site that grows and may appear up to three months after the bite. Fever and possibly muscle and joint pain in the first weeks after the bite. Sometimes joint complaints, skin complaints, nerve complaints, or heart problems can occur—either if early Lyme symptoms were not treated with antibiotics, or as a first expression of the disease. Both early and late stages can be treated with antibiotics, but later stages may already have caused damage through inflammation. Therefore, contact a GP if you develop these symptoms.

Can ticks also transfer from pets to humans?

Yes—both nymphs and adult ticks can transfer. It is important to treat pets well against ticks (and it is advisable to remove any ticks found on your dog or cat, as they often cause itching).

Menno en Erwin about Nature and Science

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