Ticks (General)
Fact Sheet
Ornate Kangaroo Ticks. Image: Eric Vanderduys.
Introduction
Ticks don‘t have a waist, neck, or even a proper head. They
have eight legs and a round flat body. What appears to be the
‘head’ of a tick is a special fused structure of mouthparts and
sensory appendages found only in ticks and mites. Ticks are
actually a particular kind of mite, and fully fed ticks are the
most massive mites of all. All ticks feed exclusively on blood
stolen from mammals, birds, reptiles, or in one South American
species, from cane toads. Ticks are an ancient group, as
shown by a 90 million year old tick in amber which is similar
to some modern species. There are over 800 species of ticks
worldwide divided into two major families, the soft ticks and the
hard ticks.
The ticks outlined here, and other less commonly encountered
species, can be brought to the Queensland Museum Inquiry
Centre for identification.
Hard ticks
The majority of ticks are ‘hard’ ticks (Family Ixodidae, 630
species), which have a hard finger nail-shaped shield on their
backs. This family includes all of the commonly encountered
ticks, for example, the:
•
Australian Paralysis tick which often attaches to
humans, dogs, and many other animals on the east
coast of Australia (see separate fact sheet which
includes information on tick removal)
•
Ornate Kangaroo tick which is common west of the
Great Dividing Range and often attaches to humans
•
Brown Dog Tick
•
Cattle Tick.
certain odours or carbon dioxide from a potential host. They
then move towards their intended victim smelling the air with
eagerly extended first legs. They always clamber on to hosts;
they cannot jump. Once on their chosen host they may spend
a long time searching for protected sites such as the armpits,
groin or around the head, neck and ears. Even though ticks
are often found on the head and neck, this is a result of ticks
climbing to a favoured attachment site rather than dropping
from trees.
Feeding of hard ticks
The most obvious tick
mouthpart is the hypostome,
an immobile barbed prong
that juts out from the front
of the tick and is flanked by
sensory palps.
The hypostome is overlaid
by a pair of thin strap-like
appendages tipped with
Underside view of tick mouthparts.
fine cutting blades (the
Image: Matthew Shaw.
chelicerae). These blades
slice into the skin while the barbs anchor the tick inside
the wound. Many ticks (e.g. Brown Dog Tick, Cattle Tick)
also secure themselves more strongly with the aid of a
special cement substance. Attached hard ticks do not feed
continually. Rather they suck blood and ‘spit’ out excess
water, salts and sometimes toxins, back into the wound. By
spitting out excess fluid their meal of blood is made as thick
as possible to cram the maximum amount of protein into
their bloated bodies.
Lifecycle of Hard Ticks
After hatching, tiny six-legged larvae seek their first meal.
During each meal they swell enormously, and once bloated to
capacity they moult to their next life stage. Larvae are too small
for many people to see when they attach for their first feed; but
after feeding they are approximately the size of the head of a
pin. Unlike later stages, tick larvae tend to cluster together and
a close encounter with a larval cluster can result in many, even
hundreds, of tiny attached ticks. After engorging, larvae drop off
to digest their bloodmeal and then moult to the nymphal stage.
The nymphs then seek a new host. After gorging themselves,
the now half-matchhead-sized nymphs drop to the ground,
digest their meal and moult to adulthood, at which point they
are ready to locate their final meal. Hard ticks only feed and
moult a maximum of three times during their life.
Host finding of hard ticks
Most hard ticks find hosts by lying in ambush at sites close to
the ground. Ticks become excited when they detect vibrations,
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© The State of Queensland, (Queensland Museum) 2011
Female Ornate Kangaroo Tick starting to feed on human.
Image: Eric Vanderduys.
Hard ticks usually spend 5-8 days or more feeding at the one
site on a single host. Compared to other blood feeders (e.g.
leeches, fleas, lice or mosquitoes), this is extremely unusual.
Their ability to feed successfully for so long is because they
prevent strong reactions from their host‘s immune system using
a cocktail of over 60 biochemicals. For four or more days after
attachment, hard ticks slowly increase in size.
During this long initial period the tick‘s skin is growing by
thickening but the overall body size increases only slightly.
After about four days of the tick‘s skin preparing in this way,
there is a dramatic acceleration in the tick‘s feeding (‘the big
sip’), when it rapidly increases body volume many times within
24 hours. The result is a grossly bloated tick, up to 120 times
heavier than when it first attached.
Although their bodies tend to be dark brown, body colour
should never be relied upon for tick identification. This tick
is mostly a nuisance to dogs, however large populations
can build up, and then dogs can become weakened and
anaemic. Only a small proportion of the infesting population
is present on the dog at any one time. The majority of the
ticks will be concealed in hiding places near where dogs
rest (kennels and bedding).The ticks found on the dog will
include many males.
In other parts of the world, Brown Dog Ticks can transmit
an agent of spotted fever, however in Australia they are not
known to harbour this pathogen.
Hard Tick egg-laying
Engorged, a female tick drops off her host and crawls to a
sheltered site to spend her final weeks digesting blood before
laying over 1000(up to 23000) eggs. As each egg is laid, it
is coated in wax to prevent drying out making egg-laying a
laborious process that can take up to two weeks, after which
the exhausted mother dies. Flexing her mouthparts downwards
she scoops up a freshly-laid egg from her abdomen and then
flexing up again presents the egg to two fleshy tentacle-like
organs (Gene‘s organs) that emerge from underneath her
dorsal shield. These organs give each egg a coat of waxes and
other protective compounds.
Ornate Kangaroo Tick Amblyomma triguttatum
In western and northern Queensland, people may attract
Ornate Kangaroo Ticks. The adult females have an almost
circular body, are noticeably large (about 5mm long before
feeding), with very long legs and a set of pale metallic marks
on the dorsal shield. In western Queensland this marking
is just a single spot. The minute larvae are most commonly
encountered in summer, and nymphs are most likely to be
found in February/March.
Ornate Kangaroo Ticks can induce local skin reactions and
a delayed hypersensitivity reaction 24-48 hours after tick
removal. For sensitised people, subsequent bites may induce
intense skin reactions and severe discomfort.
Male Brown Dog Tick. Note the cleft in the first
segment of the first leg. Illustration: Catherine Harvey.
Cattle Tick Boophilus microplus
Cattle Ticks are native to Africa where they naturally feed
on large grazing animals. They are now found throughout
warmer areas of the world where cattle are present. Female
cattle ticks attach as larvae and only finally detach when
they are ready to drop off to lay eggs. They can do this
because they have evolved the remarkable ability to moult
between stages while remaining on the host. They cannot
survive in very dry areas or in the absence of large grazing
animals such as cattle. Cattle Ticks can also be common
on feral deer in Queensland. They have great economic
importance as they can transmit debilitating diseases to
cattle.
Soft ticks
Unlike the hard ticks discussed above, ‘soft’ ticks (Family
Argasidae, 180 species) are secretive and rarely encountered nest or roost-dwellers with a highly wrinkled skin.
Ornate Kangaroo Tick laying eggs. Image:
Anthony O’Toole
Brown Dog Tick Rhipicephalus sanguineus
Brown Dog Ticks are almost entirely restricted to dogs
and their occasional attachment to other animals (pigs,
cattle and very rarely humans) is accidental. They need
a warm climate and are highly tolerant of arid conditions,
which is not surprising since their original home includes
Saharan Africa. Unusually they can be abundant in both
the driest and the wettest areas of Queensland. Dingoes
only support low numbers of this tick. The Brown Dog Tick
differs from the Australian Paralysis Tick by having short
mouthparts and all legs of the same colour. Magnification
will reveal a useful identifying feature only found in this
species: a strong cleft on the first segment of the first leg.
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© The State of Queensland, (Queensland Museum) 2011
Visitors to coral cays may be unfortunate enough to feel the
bites of the Seabird Soft Tick (Carios capensis). Seabird
Soft Ticks are associated with seabird islands and rookeries. They can reach high population densities but most are
not seen. They feed on seabirds and on human visitors to
coral cays and other islands in warm areas where seabirds
nest. Seabird Soft Ticks mostly feed at night and unlike
hard ticks, adult soft ticks feed stealthily and rapidly (in
less than 20 minutes), and then retreat to concealed hiding
places. They can produce extremely irritating reactions in
sensitised individuals and are known to carry a wide variety
of viruses.
Further Information
Roberts, F.H.S. 1970. Australian Ticks. CSIRO, Melbourne.
Author: Matthew Shaw
Queensland Museum
PO Box 3300, SOUTH BRISBANE QLD 4101
Phone: (07) 3840 7555
http://www.qm.qld.gov.au/