Ticks are from the same class of arthropods as spiders, so they are arachnids – parasitic arachnids. There are around 70 different types of ticks in Australia, with tick species found in every state and territory. However the most medically important tick species is the Paralysis Tick, Ixodes holocyclus, which is found on the east coast, with some tick populations in a number of non-coastal areas. In excess of 95% of tick bites in Eastern Australia are due to this species, resulting in most tick-borne illnesses.
Australia’s tick season, when the adult ticks are more prevalent, is predominantly from July to December, however the risk of exposure can be year-round.
Ticks are not very mobile, instead they crawl up the stem of grasses or small branches - usually no higher than 50cm - and wait, ready to attach to a passing host by piercing the skin with its sharp mouth. Once attached, they secrete an anti-coagulant which allows them to feed without the blood clotting, and in some cases, an antigen as well. In most cases, if the tick is removed promptly, its bite many only produce some localised swelling and redness for a few days only at the bite site.
Some of the health issues ticks can cause:
- Tick paralysis (very rare, as tick must remain in place for a few days)
- Transmission of infections (less common than allergic reactions)
- Allergic reactions
- Mammalian meat allergy
Tick types:
There are three main tick species which are known induce paralysis and other local and systemic symptoms when they feed on humans, however six of the 17 human-biting ticks are capable of transmitting a number of bacterial, rickettsial, viral and autoimmune illnesses that include Q fever, Queensland tick typhus, Flinders Island spotted fever, Australian spotted fever (ASF) and babesiosis. In addition, information provided by the federal health department acknowledged ‘that other serious illnesses, such as a Lyme disease-like syndrome, may be caused by exposure to Australian ticks, however there is no evidence yet this is the case (Lyme disease)’.
PARALYSIS TICK
The “paralysis tick”, Ixodes holocyclus, also known as the seed or grass tick, is identified as a flattened oval seed-shaped parasite, and only the female’s bite is a threat to native animals, birds, livestock, reptiles, pets and humans. When the tick bites and injects the anti-coagulant, it also secretes a neurotoxin that contains a paralytic agent. It’s this agent which is toxic to some animals and potentially to humans also. Two other species are also capable of causing paralysis and other local and systemic reactions. Tick paralysis is very rare, and is more often seen in children than adults.
Where are they found?
Ixodes holocyclus is found along the eastern seaboard of Australia, east of the Great Dividing Range, and possibly into Tasmania, but is not known to occur in Western Australia, South Australia or the Northern Territory. There are two other Ixodes species of paralysis ticks, I. hirsti, which occur in South Australia and also has been recognised in NSW and Tasmania, and I. cornuatus, which occurs in Tasmania and Victoria. Their preferred habitat is in high humidity areas, particularly in gullies, wet sclerophyll forests, rainforest edges and regrowth, lantana thickets and grassy areas.
Other potentially disease-carrying tick species can be found in areas across Australia, including in arid conditions.
Tick paralysis symptoms:
- Localised redness or swelling at the bite site
- Rash, headache, fever
- Flu-like symptoms, tender lymph nodes
- Feeling unsteady, light sensitivity
- Full body numbness and tingling
- Increased weakness in the limbs
- Partial face paralysis
Severe allergic reaction to tick bites
- To avoid the risk of an allergic reaction to a tick bite, don’t handle them or try to forcibly remove them – this could make them inject the allergen or toxin into the bite site.
- Allergic reactions can vary from mild symptoms, such as swelling and redness at the site of the bite, to anaphylactic shock which causes swelling of the throat, difficulty breathing and collapse. Immediate emergency medical assistance should be sought if anaphylaxis is suspected.
Tick bites and mammalian meat allergy
Australian immunologists were the first to describe an association between tick bites and the development of mammalian meat allergy, since confirmed in other regions. The proteins in the saliva of ticks sets off an allergic response which is triggered when the individual consumes any ‘mammalian meats (beef, lamb/mutton, pork, goat, horse, kangaroo, venison and other exotic mammals) … and all forms of gelatin’1. There are no desensitisation treatments to switch off tick bite allergy.
Tick bite first aid:
- Do not scrape the tick off or remove them with blunt tweezers. Use a commercially approved product to rapidly freeze and kill the tick and allow it to drop off. These products usually contain ether and they will kill the tick within five minutes. Read more on how to safely remove a tick from the National Allergy Strategy.
- If the tick does not drop off, leave it in place and seek medical attention urgently.
- If allergic to tick bites, always ensure you have the necessary medications on hand to manage reactions including anaphylaxis.
Tick bite prevention:
- Avoid tick-infested areas if possible
- Use insect repellent containing DEET, Citriodiol (extract of lemon eucalyptus or PMD) or Picaridin.
- Impregnate outer layers of clothing with a contact insecticide such as Permethrin.
- Wear a long sleeved shirt and long trousers
- Tuck pants into long socks or use gaiters
- Wear light-coloured clothing – to make ticks more visible
References:
- Australian Society of Clinical Immunology and Allergy https://www.allergy.org.au/patients/insect-allergy-bites-and-stings/tick-allergy
- Australian Department of Health https://www1.health.gov.au/internet/main/publishing.nsf/Content/ohp-tick-bite-prevention.htm
- Australian Museum: https://australian.museum
- Live Science: https://www.livescience.com
- Science direct: https://www.sciencedirect.com
- Human Tick-Borne Diseases in Australia: https://www.frontiersin.org/articles/10.3389/fcimb.2019.00003/full