The seven hundred or so species of ticks in the world form one group, Metastigmata, of the subclass Acari, which also includes the mites. Although these parasites are closely related to the mites they are usually considered separately because of their relatively large size.
There are about 73 species of tick in Australia. They are blood-feeding parasites which live on wild and domestic animals, birds, reptiles and man. They parasitize all kinds of vertebrates, except fish. Their mouth-parts are adapted for boring into the flesh and sucking blood or other fluids. The body is oval and has a leathery cuticle.
Many species of tick transmit a variety of diseases to man and animals. Those causing considerable problems include the Scrub Tick, Ixodes holocyclus, the Cattle Tick, Boophilus microplus, and Dog Ticks of the Ripicephalus species. The tick which most commonly attaches itself to people in Australia is the Scrub Tick.
Most ticks have two distinct patterns of life. There is the parasitic stage when they live on the body of the host and feed on its blood, and the non-parasitic stage when they drop to the ground to breed. The females lay their eggs on the ground, often in the lair of the host, and the immature ticks grow in a series of moults until they are stimulated by odor to seek out their host.
During the warmer months children and pets should be checked daily for ticks. The first symptom of tick bite is an intense itching which is usually sufficient to detect the parasite on humans. However, in animals the scratching may go unnoticed and no ill effect may be seen until the animal is unable to stand on its hind legs. By this time it is often too late to prevent death. Animals subjected to many small doses of the toxin will gradually build up an immunity and anti-tick serums are also available.
Tick bites are troublesome for two reasons. They allow bacteria to enter the skin, resulting in sores and ulcerations, and the tick itself may carry protistans which enter its host and cause disease. Ticks can survive for long periods, months, or even years, without food and the protistans they carry can fast for just as long. And the protistans pass into the tick's eggs and so are passed to the next generation.
In North America Texas fever is passed to cattle by the cattle tick. This has at times caused losses of millions of dollars a year. The disease is controlled by keeping cattle away from infested pastures. The female ticks die after laying their eggs. The larvae or seed ticks cannot live more than a few months if there are no cattle to feed upon.
Ticks have four stages in their life-cycle: the egg, a 6-legged larva and an 8-legged nymph and adult.
A typical tick's life is very simple. The female lays her 4 - 8 thousand eggs at random, usually on the ground. The six-legged larvae that hatch from these climb up plant stems or grasses and wait until an animal brushes past. Then they cling to the animal's skin, feathers or hair. The larva pushes its hypostome into the animal's skin and sucks the blood until it is gorged, then it pulls out its hypostome and falls to the ground. There it sheds its outer skin and changes to a nymph, which has four pairs of legs. This repeats the actions carried out by the larva, and in turn drops to the ground when gorged with blood. After another moult the adult stage is reached.
This is the only stage at which there is a difference between male and female, mainly in their size. A female's body swells as she feeds and becomes many times the size of a male's body. There is a tough shield that covers the whole of the body and limits the extent to which it can swell.
Argasid ticks usually lurk in the nests, lairs and dens of their hosts, feeding when these are present. Ixodid ticks may be one-host, two-host or three-host ticks. One-host ticks complete their life cycle, from larva to engorged adult, on the one individual. The larva and nymph of the two-host tick feed on one host; then the engorged nymph falls, moults to the adult stage and finds another host, often another species, on which to feed. Three-host ticks spend the larval, nymphal and adult stages on separate hosts which may be of different species. Ticks are damaging because heavy infestations rob the hosts of large quantities of blood. Many of them also transmit serious diseases. Host specificity is not strict, though ticks that live on cold-blooded vertebrates do not attack warm-blooded ones, and vice versa.
The most troublesome in Australia is the scrub tick (Lxodes holocyclus) present in eastern Australia and a considerable annoyance to dogs and man: the cattle tick (Boophilus mkroplus) can cause tick fever in cattle: and poisoning can be caused by the brown dog tick (Rhipicephalus sanguineus), in Queensland and northern NSW.
While many dogs in Australia are known to have died from tick bites, they can also be a hazard to children. A scrub tick can attach itself to human skin and the initial bite is painless; only after several days can a stiffness of the limbs be noticed.
Once a tick is attached there have been a number of methods proposed for their removal. Kerosene or a similar fluid can be applied (or even applying nail polish) to kill the tick and make it loosen its grip.
However, in most instances they may easily be removed by gently pulling the tick off with the fingers. Unfortunately this method of removing ticks may break off the mouthparts of some species with longer hypostomes. If only the body is pulled away, the head and poison glands may be left embedded in the flesh. When sterile instruments are available they can be removed by pulling on the tick to elevate the skin surrounding the site of attachment and then slipping the point of a needle or scalpel under the mouthparts. With gentle pressure the mouthparts can be removed with a minimum of tissue damage. Once the tick is removed an antiseptic should be applied.
If you're out in the bush without access to any of the aforementioned chemicals or equipment another method is to apply the lighted end of a cigarette to the back of the tick. Resulting in it curling up and dropping off.
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