Ticks

There are 889 species of tick world wide, and 23 British species. Ticks transmit a greater number and variety of disease causing organisms that any other arthropod in the world. However fewer than a quarter of the species spread disease, but those that do tend to have a wide range of hosts.

Transmission of disease usually occurs through a bite. The disease organism will be located in the salivary glands of the tick, and enters the host when the tick returns excess fluids back into the host. However transmission of disease can also arise from the tick's body secretions, waste products, or even its squashed body.

There are 4 stages to the tick lifecycle:

  1. egg
  2. 6 legged larva
  3. 8 legged larva or nymph, during this stage they may moult a number of times
  4. 8 legged adult

To complete their life cycle ticks must eat three meals from three separate hosts. After eating a blood meal a tick can be 3 cm in length.

Tick transmitted diseases that most commonly affect humans

  • Lyme disease. This is caused by the bacterium Borrelia burgdorferi, and is transmitted by quite a few species including Ixodes ricinus, I. gibbosus, I. pacificus, I. scaularis, Haemaphysalis punctata, Dermacentoer reticulatus, Argas reflexus. Initial symptoms are headache and flu-like, and may be accompanied by a rash. Early treatment is effective and is usually by a course of antibiotics.
  • Boutonneuse fever, also known as Marseilles or Mediterranean fever. Found in southern Europe, but is spreading northwards, also found in Asia and Africa. 2.5% of cases are fatal. It is transmitted by Rhipicephalus sanguineus, Dermacentor sp., Ixodes sp. and R. conorii (a tick usually found on dogs).
  • Q Fever or Queensland fever. This disease is not confined to Australia, but is found worldwide. It is caused by the bacterium Coxiella bournetti, and is spread by many tick species.
  • Tick-borne encephalitis. This is caused by a Flavovirus and is spread by many tick species. It has a mortality rate of 1 - 5 %.
  • Human babesiosis. The disease is caused by the protozoans Baberia divergens and B. microti, and is spread by Ixodes ricinus among others. The symptoms are malaria-like.
  • Tick paralysis, also known as Toxicosis. This is caused by toxins in the tick's saliva that are injected into the host's bloodstream during feeding.

Right is Ambylomma sp., a hard tick which sucks blood from various animals.

Amblyomma sp.

Dermacentor variabilis, American dog tick

Dermacentor variabilis, the American dog tick or wood tick

On the left is Dermacentor variabilis, the American dog tick or wood tick. It can transmit Rocky Mountain spotted fever and tularemia. It is found east of the Rocky Mountains and on the Pacific coast. Its preferred host is the dog, but it will feed on other large mammals, including man. It can reach 1.5 cm in length after a full meal.

Ixodes ricinus, castor bean tick, sheep tick

Ixodes ricinus, sheep tick, castor bean tick

 

Ixodes ricinus, the castor bean tick or sheep tick

Left and below are Ixodes ricinus, the castor bean tick or sheep tick. In the photograph below the bars are in mm. The top tick had just been taken off my dog where it had been sucking her blood, and the bottom tick is either male or had not yet started to suck. A female is just 1 - 2 mm long before feeding, but 10 mm long after feeding.

This tick needs high humidity, and is commonly found on rough, undrained grazing land where there is a mat of decaying vegetation under which the ticks have the humidity they need to survive.

This is one of the most common ticks in the UK, and will suck the blood of anything warm blooded. The mouthparts are a little like a harpoon with backward-curving teeth making it difficult to pull out once it has pierced the skin. Only the female has the hugely extendible skin enabling her to swell up with a large blood meal.

Lifecycle

The lifecycle takes 3 years. When the egg hatches the larva has just 6 legs. Next spring the young tick climbs up grass or other vegetation to wait for a passing host. The tick dries out quickly, so if a host doesn't pass soon it will drop to the moist ground before trying again.

After feeding on the host it drops to the ground where it moults into an 8 legged larva/nymph resembling the adult.

Next spring it climbs vegetation and attaches to a host yet again for a blood meal. It feeds for several days, then again it drops to the ground and moults into an adult.

Next spring it again climbs vegetation to suck blood. The female takes in a huge blood meal increasing her size greatly. Each blood meal takes around 5 - 6 days.

Mating may take place on the host or after dropping to the ground. The males die after mating. The eggs are laid in the summer in crevices in the ground. The female lays around 2000 eggs. Each egg is covered with a waterproof layer of wax. After the female lays eggs she, too dies.

Where to find ticks on dogs

The most common place to find ticks on your dog are on and behind the ears and between the claws.

Treatment/removal

I found these ticks on my dog. I used to treat her with Frontline, but this year the ticks are very bad and Frontline does not seem to be working.

I got the ticks out with a small, plastic tick remover I got at the local vet's. I was a bit skeptical at first, but it worked really well and was very easy to use. It is much easier than vaseline, and cheaper than whisky.

It is important to get all the tick out and the tick remover does this very well.

I will be trying Advantix on my dog next to see if that works better.

Yes, Advantix works well, and she's never had ticks since I used it on her. Apparently it depends on the area where you live. Ticks on upper Deeside are just tough to kill.

Ticks should be removed as soon as possible, even though it is difficult to get them out when they are really small, because they can transmit the bacteria that cause Lyme disease through their saliva.

Ticks on humans

This is from personal experience. The tick was on my elbow and looked just like a small black speck (it could not have been there for more than 12 hours). It was fairly easily removed with the tick removal tool I got for my dog. Then I bathed the area with alcohol.

It is important to get the tick out as soon as you can, as the longer you leave it feeding the more chance there is of it passing on the Lyme disease bacteria. Vaseline will suffocate it, and whisky or other alcohol will kill it, but hauling it out is quickest if you have a tick tool.

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