By Paul Donovan
It’s not always the big critters you have to watch out for…
They often say “It is the little things which can do us the most harm”, and this is especially true when it comes to ticks. Ticks are external parasites which latch onto their host and suck blood. As if blood-sucking wasn’t enough, they can also act as vectors (transmitters) of some very nasty diseases.
Ticks are classified as Arachnids (relatives of spiders, scorpions, mites) as they have eight legs and two parts to the body; and they are further divided into soft ticks (Argasidae) and hard ticks (Ixodidae). Soft ticks have a tough leathery skin and several nymphal stages during their development. Hard ticks have a ‘hard’ skin. In males of the latter type, this covers the entire upper surface, while in the females, the nymphs and larvae it covers just a small area behind the head. Hard ticks undergo several nymphal stages and are responsible for spreading more diseases than soft ones.
A tick’s lifecycle
Before we look at the ins and outs of tick bites, how to prevent them, and how to deal with a tick when it is latched onto your leg, it is important that we understand their lifecycle, as this will have a bearing on how we can prevent bites.
The lifecycle of a hard tick is complex, and has four stages: Egg, six-legged larva, eightlegged nymph (soft ticks have several nymphal stages, whereas hard ticks have a single one), and finally, eight-legged adult.
After the ticks mate, the engorged female drops off the host where, after a few days, she then lays several thousand eggs − either on the ground, amongst tree bark, or on the underside of a leaf − and then dies. A few weeks or months later (depending on temperature and/or rainfall), the eggs hatch into small six-legged larvae. These climb grass stems and wait for a host to pass by. They hold onto the grass with their third and fourth pairs of legs, leaving the first pair free to grab onto the host.
When a host passes by, the tick will try to attach itself to the skin, where it will then insert its feeding tube and begin sucking blood. The feeding tube may have barb-like extensions which enable the tick to hold onto its host.
As the tube pierces the skin, it releases a small amount of saliva that contains anticoagulants, anti-inflammatories, immunosuppressants and anaesthetic properties. These are used to ‘hide’ the tick so that you are oblivious to its presence as it sucks away at your blood. The larva then moults into an eightlegged nymph and eventually into an adult. These adults then mate, and after becoming engorged on blood, the female drops off to begin the cycle all over again.
This is an over-simplification of the lifecycle of a hard tick, which for some species may require multiple intermediate hosts at varying stages of its development before it can fully mature. For example, the sheep tick Ixodes ricinus will make use of chickens, pigs, cats, dogs, rodents, snakes and humans in this cycle.
As primitive as ticks may appear, those which are hostspecific (use a single host) could be regarded as being more ‘advanced’ than the multiple-host species. The reason I say this, is that such ticks are capable of identifying their host with the aid of complex sensory organs that not only detect minute traces of carbon dioxide given off by it, but also its body odours, heat, moisture, vibrations and even shadows. From this, the tick can ‘evaluate’ where the host is, and how far away it is. The tick may also identify and move towards pathways used by the host animals before ascending a stem of grass and waiting for it to pass by.
Vectors for disease
If the tick is a vector for a disease, it can either introduce the disease into the host as it begins to draw blood, or pick it up from the host. Without interference, a tick can remain sucking away on the host for anywhere between six and 20 days (depending on the species and lifecycle stage) before it detaches itself and falls to the ground. Here it can wait for days, if not months, before a new host arrives on the scene.
How to remove a tick
There are right and wrong ways to remove a tick. First, let me tell you how NOT to do it. The age-old technique of burning it with a match, cigarette, or dabbing it with petrol, alcohol, nail varnish, etc., in the hope that this will make the tick release its grip, should be avoided. It won’t. What this is more inclined to do is to make the tick regurgitate fluids back into your flesh, releasing any potential diseases it may be carrying before it would otherwise have done so.
As repulsive as they may be, a tick should be removed with care. Don’t forget, it has barbs on its mouthparts which hold it in place, so simply grasping the body and yanking it off may leave the head in your flesh where it could create an infection. It is better to grasp the tick with a pair of tweezers as close to the skin as possible. Apply gentle pressure and slowly begin to pull the tick upwards until it releases its grip naturally.
The area of the bite should be washed with warm soapy water, a mild disinfectant or an alcohol wipe. Pat the bite dry to avoid irritation. Apply an antibiotic or antihistamine cream and observe the bite for several days for signs of swelling or rash.
Should any symptoms develop such as fever, headache, tiredness, joint pain, or a lingering rash which does not go away, see a doctor immediately as you could be suffering from a tick-borne disease. Inform the doctor that you have been bitten by a tick.
What are tick-borne diseases?
In simple terms, these are diseases that are spread from a tick to an animal or human. The tick may be carrying any number of viruses, bacteria, protozoa or other pathogens. A tick can pick up the parasite as it feeds on the blood of a sick animal, or on an otherwise healthy animal that is a carrier of the parasite. The tick then becomes the main spreader (vector) for the disease.
As the tick feeds on an infected animal, drops off and finds another host to feed on, a disease can spread quickly. However, in a species-specific tick, the movement of any parasites will be contained within that group of animals. The problem arises when the tick is non-selective, as it can spread a disease through many different host groups. For example, it could feed on a sheep and then a human. A disease that can cross barriers between animal and humans is called a zoonotic disease.
What disease can be spread to humans by ticks?
Ticks are second only to mosquitoes when it comes to spreading disease, and the diseases that they can transmit are wide-ranging, depending on the country of origin. Some of the more common are Lyme disease, relapsing fever, tick paralysis, rocky mountain fever, Colorado tick fever, Q fever, Babesiosis, Bartonella, Boutonneuse fever, and tickborne encephalitis.
Not every tick will be a vector for a particular disease. In Lyme disease, the most common of the diseases transmitted from tick to humans, fewer than 3% of people will actually catch the disease, as only a small number of ticks will be carriers. As Lyme disease is possibly the most common disease you are likely to catch from a tick bite, let us just spend a few moments discussing what the symptoms of this disease are. I am not a doctor, but having caught the disease once, I talk from experience.
The tick carries the Lyme disease bacteria in its gut where it will remain until optimum time for dispersal. The bacteria will move towards the mouth of the tick, and then into the host, only after the tick has become engorged (bloated) with blood. This usually takes about 24 hours, although it can be significantly sooner if the tick is already partially engorged.
Once the bacteria is in the bloodstream, it begins to multiply. The first sign that something may be amiss is a rash spreading outwards from the bite area. This can take anywhere up to a month to show itself. The rash increases in size over several days. As it progresses, the skin nearest the bite become pale in colour. The rash is not itchy; in fact, I didn’t even know it was there until someone pointed it out; it was at the back of my knee, and the only reason that I knew it was from a tick bite, was because of its shape. I put some antihistamine cream on it, and the rash disappeared in just over a week-and-a-half.
The point at which I knew I had Lyme disease was when I developed a headache (which I never have usually), and my joints began to ache. I felt as if I were heading for a severe bout of flu. I associated this with the rash and paid a visit to the pharmacist, who prescribed a course of antibiotics. (I have known people who have had the rash without developing further symptoms, so Lyme disease can manifest itself, or not, in variable ways.)
If left untreated, Lyme disease can progress to more serious complications, affecting the nerves, heart and brain. If you wish to know more about tickborne diseases, I suggest you visit one of the many websites on the internet.
There has been a lot of talk about taking antibiotics as a ‘precaution’ when travelling in, or to, areas where Lyme disease is known to be prevalent. This is probably not a good idea, as many bacterial infections are becoming ever more resistant to antibiotics.
Preventing tick bites
Limiting ones exposure to ticks is the name of the game, and there are various ways in which this can be achieved. The first (although this may be the hardest because we like spending our time in the bush) is to avoid long grassy areas during the tick season, particularly where there is a lot of livestock and game about.
Although it is nice to wear shorts during the summer months, in tick areas these should be discarded in favour of long trousers tucked into your socks or boots, and a longsleeved shirt.
Although many people will tell you to wear ‘light-coloured trousers’, I don’t think that there is much difference between lightand dark coloured clothing. Light was advocated because it was easier to spot ticks if you picked any up, and the belief was that dark clothing attracted them. I have found just as many ticks on dark clothing as I have light. You could say the jury is out on that one.
What is more important than the colour of the clothing is to impregnate it with some sort of insect repellent. There are many repellents on the market which you can use for this purpose, but look for one containing DEET (N,N-diethyl-m-toluamide). Permethrin can also be used; some people apply it to the skin, but this is not a very effective as the oil in our skin deactivates it − and it’s not very good for the skin, anyway. Personally, I have found repellents containing permethrin to be more effective than DEET for preventing tick bites, although DEET is really good at repelling mosquitoes.
When you get home after spending time in the wilderness, have a shower and thoroughly check your body. In particular, check the back of your legs behind the knees, as this seems to be a favourite hiding spot for ticks − although they can occur just about anywhere, even in the hair. If you take your dog with you, don’t forget to inspect him or her as well.
Although ticks can be a problem, and you are bound to get one or two on you at some time or other while in the bush, a degree of sensible precaution will reduce the chances of picking up a disease. And ticks should by no means reduce your enjoyment of the outdoors.