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Ticks are blood feeding external parasites of mammals, birds, and reptiles throughout the world. Ticks belong to the order Acarina, which also contains mites. Approximately 850 species have been described worldwide. The soft ticks (Family Argasidae) are often associated with nests or resting places of animals. These ticks have a wrinkled appearance, like soft leather. The hard ticks, (Family Ixodidae), comprise the majority of Australian ticks and are distinguished by a hard dorsal plate in the shape of a fingernail and elongated mouthparts that have rows of backward pointing teeth. Most hard ticks secrete a cement-like substance produced by the salivary glands which literally glues the feeding tick in place; the substance dissolves after feeding is complete. Ticks transmit the widest variety of pathogens of any blood sucking arthropod, including bacteria, rickettsiae, protozoa, and viruses. Many hard ticks can go for several months without feeding if not unduly duressed by environmental conditions. Many soft ticks have an uncanny resistance to starvation, and can survive for many years without a blood meal.

The life stages of soft ticks are not readily distinguishable. Unlike hard ticks, many soft ticks go through multiple nymphal stages, gradually increasing in size until the final molt to the adult stage. The time to completion of the entire life cycle is generally much longer than that of hard ticks, lasting over several years.

Hard ticks have very few predators, and are more likely to succumb to desiccation from high temperatures and low humidity. From the enormous numbers of eggs (2,500-3,000) deposited in the moist leaf litter by the female before she dies, only a fraction of the eggs will survive and eventually grow to become adults. The six-legged larvae hatch after the eggs have incubated for 40-60 days. To moult to the next stage, the larval tick must obtain a blood meal. In searching for a host, they display a behaviour referred to as 'questing'; whereby the tick climbs to the top of nearest vegetation and waves its forelegs to and fro slowly, hopefully contacting a prospective passing host. Certain biochemicals such as carbon dioxide as well as heat and movement serve as stimuli for questing behavior. Ticks usually do not climb more than around 50cm in the vegetation and there is no evidence to suggest that they fall out of trees. (Some soft ticks seek hosts by questing on low-lying vegetation, but the vast majority are nest parasites, residing in sheltered environments such as burrows, caves, or nests.)

Once a suitable host is found, the larvae will blood feed for 4-6 days, drop from the host and moult to the eight-legged nymphal stage. Nymphs require a further blood meal for 4-8 days before moulting to the adult stage. Both female and male ticks quest for a host, but for different reasons; the female for a bloodmeal, the males to search the host for female ticks in order to mate and sometimes feed from them. Males may actually parasitise the female ticks by piercing their cuticle with their mouthparts to feed on her haemolymph (the tick's blood) and up to 3-4 males have been found feeding on one female tick. Male ticks rarely bloodfeed on a host. Hard ticks feed for extended periods of time on their hosts, varying from several days to weeks, depending on such factors as life stage, host type, and species of tick. The outside surface, or cuticle, of hard ticks actually grows to accommodate the large volume of blood ingested, which, in adult ticks, may be anywhere from 200-600 times their unfed body weight. (By comparison, the outside surface, or cuticle, of soft ticks expands, but does not grow to accommodate the large volume of blood ingested, which may be anywhere from 5-10 times their unfed body weight.) The adult female tick will drop off the host after feeding and lay eggs over several weeks before dying. The male tick dies after reproducing.

If visiting known tick infested areas, light coloured clothing should be worn, as ticks will be much easier to detect. Trousers should be tucked into socks and shirts into pants. An insect repellent containing DEET or Picaridin should be applied, with a cream repellent applied to the skin and a spray repellent to footwear and clothing (note that DEET can damage some synthetic clothing). The repellent should be reapplied every few hours. All clothing should be removed on returning home and placed into a hot dryer for 20 minutes, which will kill any ticks that may still be on the clothing. Note that ticks can wander on the body for some two hours before attaching. The body should thereafter be searched well for ticks, especially behind the ears and on the back of the head, groin, armpits and back of the knees.

If a tick is detected that is attached, never attempt to place any chemical such as methylated spirits onto the tick, nor should it be touched or disturbed, as the tick will inject saliva into the skin, which could make the situation worse. Rather the tick should be sprayed with an aerosol insect repellent preferably containing pyrethrin or a pyrethroid (if a repellent cannot be found which contains a pyrethroid, then Lyclear, a scabies cream containing permethrin will work fine). The combination of hydrocarbons and the pyrethrin acts as a narcotic and a toxicant, and prevents the tick from injecting its saliva. The tick should be sprayed again one minute later (or dabbed with the Lyclear) and left. After 24 hours it should drop off naturally or be gently removed with fine-tipped forceps. It is normal for a tick bite to remain slightly itchy for several weeks, however if other symptoms develop, then a doctor should be consulted immediately.

 

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