The Australasian Society of Clinical Immunology and Allergy

Problems associated with tick bites include tick paralysis, transmission of infectious disease and occasionally, allergic reactions.  Like other arachnids such as spiders, scorpions and mites, ticks have eight legs.  They pass through a number of life stages from egg, to larva, to nymph and then finally, the adult.  Adult ticks are present in Australia between around August to February and  cause problems to their human and animal hosts.

TICKS DO NOT STING

Adult ticks attach themselves to the tips of grass blades and vegetation, and transfer themselves to passing animals or human. When humans are infested, the tick usually crawls up inside clothing. Adult ticks attach themselves strongly to their host by biting through the skin, and generally lodge in the skin of the head or neck.  The most common reaction is local irritation and swelling. Tick saliva can also transmit infection, and contains toxic proteins that can cause paralysis, and proteins capable of triggering allergic reactions.

TICK ALLERGY 

Minor local itching and swelling is common at the site of a tick bite. Serious allergic reactions (such as anaphylaxis) have also been described, in response to a number of species of ticks, including the so-called Australian paralysis tick, Ixodes holocyclus. Most reactions occur when the tick is disturbed, such as scratching the bite site, or after attempts to remove it. This has implications for what should be done when a tick is discovered (see below).

DIAGNOSIS AND MANAGEMENT OF TICK ALLERGY

At this time, there is no reliable skin or blood allergy test to confirm a diagnosis of tick allergy. Limited research suggests that the allergen causing problems is a salivary protein. Diagnosis is therefore based on the history of the reaction. Management involves avoidance of ticks where possible, and knowing what to do if bitten again. There is currently no commercially available extract to use for immunotherapy (desensitization) to switch off the allergy.

TICK PARALYSIS

This is beyond the scope of this article.  Further information can be obtained at:

• Medline Plus links http://www.nlm.nih.gov/medlineplus/ency/article/001359.htm
• Ulladulla Veterinary Hospital http://www.shoal.net.au/~rwylie/tick.html

TICKS AS A SOURCE OF INFECTIOUS DISEASE

Ticks can transfer infection is from animals to human hosts, such as Lyme disease or Spotted Fever.  This is beyond the scope of this article, but useful information can be found by contacting:

• TAGS (Tick Alert Group Support Inc., PO Box 95 Mona Vale, NSW 1660  (http://www.tickalert.org.au/) or,The Tick-Borne Diseases Research Unit, Royal North Shore Hospital, Pacific Highway, St Leonards NSW 2065.American Centre for Disease Control http://www.cdc.gov/ncidod/dvbid/lyme/
• Medline Plus Links http://www.nlm.nih.gov/medlineplus/lymedisease.html

REDUCING THE RISK OF TICK BITES

The following measures may reduce the risk of tick bite:

• Wear long-sleeved shirts and long trousers when walking in areas where tick occurTuck trouser legs into long socksWear a hatWear light clothes; this makes it easier to see ticksBrush clothing before coming inside to remove ticksUndress and check for ticks daily, checking carefully in the neck and scalpAn insect repellant may help, particularly ones containing DEET (eg. Rid, Rid Tropical)
• In those allergic to ticks, carrying a spray can of "Aerostart" (see below), emergency medication (EpiPen) and a means of summoning assistance (such as mobile telephone), are essential components of management.

WHAT TO DO WHEN YOU ARE ALLERGIC TO TICKS AND FIND ONE

Disturbing the tick can result in the injection of allergen, and can trigger an allergic reaction.
The following steps are recommended:

• Do not forcibly remove the tick*Do not try to kill the tick using insecticide or chemicals (eg. oil, turpentine, methylated spirits)Do kill the tick by spraying it with "Aerostart", an ether-containing spray that freeze-dries the tick and kills it instantly. This allows the tick to fall out without being able to inject allergen-containing saliva. "Aerostart" can be purchased from hardware stores and some service stations, and is commonly used by mechanics to clear carburetors. http://crcind.com.au/catalogue.nsf/web_brands/Aerostart?openDocument   Use EpiPen if potentially dangerous allergic symptoms occur.

• Seek medical attention in case additional treatment is required.

* SPECIAL NOTE

Whether to kill or remove ticks first, commonly causes confusion. In part, this is because most of the literature is concerned with reducing the risk from tick paralysis, rather than preventing allergic reactions. In the past, it was often recommended that ticks be killed first before removing them, to reduce the risk that they would inject toxin and trigger paralysis. It was later realized that ticks poisoned with insecticide or spirits did not die immediately, and that such chemicals could actually disturb them enough to inject more toxin. Currently, most writers concerned with tick paralysis or tick-borne infection recommend that ticks be removed using physical means only (e.g. using special forceps http://www.aafp.org/afp/20020815/643.html). The authors of this educational article do not recommend any method other than using "Aerostart" (or similar product) as described above for patients with tick allergy.

ADDITIONAL WEB LINKS

• NSW Department of Health 2004 article http://www.health.nsw.gov.au/public-health/phb/HTML2004/novdec04html/article6p212.html Tick Alerts Support Group (TAGS, Australia) http://www.tickalert.org.au/index.htm Australian Venom Research Unit, Department of Pharmacology, University of Melbourne http://www.avru.unimelb.edu.au/avruweb/arthrop.htm#ticks CSIRO Australia Entomology http://www.ento.csiro.au/
• University of Sydney Department of Medical Entomology http://medent.usyd.edu.au/photos/tick_photos.htm http://medent.usyd.edu.au/fact/ticks.htm

REFERENCES

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DISCLAIMER

The content of this article has been reviewed by ASCIA members, represents the available published literature at the time of review and is not intended to replace professional medical advice. Any questions regarding a medical diagnosis or treatment should be directed to a
medical practitioner.

For further information on allergy, asthma or immune diseases, visit www allergy.org.au - the web site of the Australasian Society of Clinical Immunology & Allergy (ASCIA).  ASCIA is the peak professional body of Clinical Immunologists and Allergists in Australia and New Zealand.

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© ASCIA 2006

Content Last updated March 2006