John Campbell, of Christchurch, asks :-

I recently arrived back from Canada and the USA with a tick attached to my leg which my doctor photographed, removed and sent away for identification. Does this happen much and is the tick dangerous to me or biosecurity?

Scott Hardwick, a biosecurity entomologist with AgResearch, responded.

These are really good questions as “ticks suck” and not just because they feed on blood. There are about 900 species of tick worldwide of which 11 occur in New Zealand. Of these only one, Haemaphysalis longicornis (the cattle tick) is introduced. It is important that we keep ticks from overseas out of New Zealand due to the potential harm that they or the diseases they carry could cause to humans, native species, pets and farm animals.

Your tick has been identified from its remains as a female Amblyomma americanum or lone-star tick. The long retention time on the patient is explained by the fact that there was no male tick present, so the female was not inseminated and as a result could not engorge with blood and eventually detach.

Travellers coming into New Zealand occasionally, and unwittingly, bring an unwelcome ‘souvenir’ in the form of a tick with them. These ticks can either be either attached to their bodies or in their luggage. A recent review of border interceptions showed 172 records of exotic ticks of which approximately half were associated with travellers that had moved across New Zealand’s borders.

Intercepted ticks come from all areas of the globe with those originating from Australia (50 per cent), Oceania/the Pacific (10 per cent), North America (10 per cent) and Asia (9 per cent) making up a majority of the records. Perhaps the most concerning feature of these records is that they are incomplete as there are reports of travellers returning to New Zealand finding, removing, and throwing away ticks that they find on themselves.

No matter how embarrassing, if you return to New Zealand after travelling and find a tick on you it is extremely important to go to your doctor and have it removed and sent away for identification. This is because ticks can vector a wide range of diseases. While it is commonly known that some ticks transmit Lyme disease most people are unaware that as a group ticks can transmit over 220 different disease causing organisms. It is important to know the identity of the tick that has bitten you as each different species is associated with a small subset of these diseases. Knowing which disease that you may have been exposed to will allow your doctor to arrange to prescribe appropriate treatments and let them know which symptoms to look for.

I would like anyone to contact me should they have a tick they want identified or if they were bitten by a tick while they were travelling abroad. This information will help clarify the potential risk to New Zealanders whilst travelling overseas.