Summary
Problems associated with tick bites include tick paralysis, transmission of infectious disease and occasionally, allergic reactions.

Ticks have 8 legs

Like other arachnids (e.g. 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 (present in Australia between around August to February) cause problems to its 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/desensitisation 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.  Information on these disorders is beyond the scope of this article, but useful information can be found by contacting:

1. •TAGS (Tick Alert Group Support Inc., PO Box 95 Mona Vale, NSW 1660  (http://www.tickalert.org.au/) or,
   

2. •The Tick-Borne Diseases Research Unit, Royal North Shore Hospital, Pacific Highway, St Leonards NSW 2065.
   

3. •American Centre for Disease Control http://www.cdc.gov/ncidod/dvbid/lyme/
   

4. •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:

1. •Wear long-sleeved shirts and long trousers when walking in areas where tick occur
   

2. •Tuck trouser legs into long socks
   

3. •Wear a hat
   

4. •Wear light clothes; this makes it easier to see ticks
   

5. •Brush clothing before coming inside to remove ticks
   

6. •Undress and check for ticks daily, checking carefully in the neck and scalp
   

7. •An insect repellant may help, particularly ones containing DEET (eg. Rid, Rid Tropical) or other products such as Aerogard.
   

What to do if you have had potentially dangerous allergic reactions to tick bites in the past

If you are allergic to ticks, you should carry emergency medication (an adrenaline auto-injector such as EpiPen or Anapen) and a means of summoning assistance (such as mobile telephone).

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:

1. •Do NOT forcibly remove the tick*
   

2. •Do not try to kill the tick using insecticide or chemicals (eg. oil, turpentine, Kerosene, methylated spirits)*. This is because attempts to remove the tick or using these products can irritate the tick, thus increasing the risk that more allergen-containing saliva may be injected. Indeed, most allergic reactions to ticks occur when an attempt is made to remove the tick, or when it is disturbed (eg. scratched).
   

3. •Seek urgent medical attention in case additional treatment is required. (The tick can then be removed under medical supervision where there are the facilities to treat an allergic reaction).
   

4. •Use EpiPen if potentially dangerous allergic symptoms occur.
   

* Should one remove ticks or leave them alone?

Whether to kill or remove ticks in patients allergic to ticks 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. It is commonly recommended that ticks are killed first before removal in order to reduce the risk that they inject more toxin and trigger paralysis. Ticks poisoned with insecticide or spirits, however, do not die immediately, and that such chemicals can disturb them enough to inject more toxin. Other 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).

Additional information and options for treatment of those with tick allergy

The author of this educational article currently recommend that the tick is killed first using a product called “Aerostart”, and that medical attention be sought immediately after doing so. “Aerostart” is 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 carburettors. Since Aerostart is a flammable product, it is wise to use it away from naked flames and to not smoke around the area of use. (Rapid cooling of the surrounding skin may also occur and thus skin irritation). (More information on Aerostart can be obtained at -  http://crcind.com.au/catalogue.nsf/web_brands/Aerostart?openDocument).

It is important to note that:

1.This advice is based on clinical experience of those treating patients with tick allergy; and

2.This product is not “registered” for such use; and

3.That this product is flammable, and thus should not be used near naked flame or when smoking; and

4.That rapid cooling of the skin and thus skin irritation may occur; and

5.Since it is unlikely that formal studies in this area will occur in the near future, such advice is based on a consensus of “expert opinion” rather than derived from results of formal clinical studies.

Tick bites and red meat allergy

Observations of a relationship between adult onset red meat allergy and prior tick bite reactions has been noted by researchers in Australia and the USA. The mechanism is an active rae of research.

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

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