Australian Paralysis Tick

Ixodes holocyclus, commonly known as the Australian paralysis tick, is one of about 75 species of Australian tick fauna and is considered the most medically important. It can cause paralysis by injecting neurotoxins into its host. It is usually found in a 20-kilometre wide band following the eastern coastline of Australia. Within this range Ixodes holocyclus is the tick most frequently encountered by humans and their pets. As this area also contains the majority of Australia's most densely populated regions, incidents of bites on people, pets and livestock are relatively common.
Paralysis ticks are found in many types of habitat particularly areas of high rainfall such as wet sclerophyll forest and temperate rainforest. The natural hosts for the paralysis tick include koalas, bandicoots, possums and kangaroos.
== Description ==
The life cycle of Ixodes holocyclus consists of four stages- egg, larva, nymph, adult. Ticks hatch as six-legged larvae after an incubation period of 40 to 60 days. Larvae search for a blood meal from a host, feed for four to six days, then drop from the host and moult to become an eight-legged nymph. Nymphs require a second blood meal before they can moult again to become an adult. Female adults then require a further blood meal of up to ten days before dropping off to lay up to 3000 eggs in leaf litter. Male adults will search for females on the host for mating, and to parasitise the females for blood meals. This life cycle takes around a year to complete (average 365 days, minimum 135 days, maximum 437 days).
Larvae have 3 pairs of legs and the nymphs and adults 4 pairs. Ixodes holocyclus requires three hosts to complete its life cycle, thus it is a 'three-host tick'. To moult to the next stage a blood meal must be obtained by the larva or nymph. Moulting is known as ecdysis.
To find a host, ticks use a behaviour known as 'questing' - climbing onto vegetation and waving forelegs slowly until a host comes within reach. When on the host, they may not attack immediately, but wander for up to two hours until attaching on the back of the host's head or behind an ear. Certain chemicals such as carbon dioxide (hence the use of 'dry ice' baits) as well as heat and movement serve as stimuli for questing behaviour.
Both female and male ticks quest for a host, but for different reasons. The female quests for a blood meal, the male to search the host for a female tick in order to mate and feed from her. Males may parasitise the female ticks by piercing their cuticle with their mouth parts to feed on the haemolymph (up to 3-4 males have been found feeding on one female tick). Adult male ticks rarely blood-feed on a host. 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 to 600 times their unfed body weight. When a tick is fully engorged it is said to be replete.
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