CABI Blog

Over Easter I took the opportunity for a few days’ break in the Scottish Highlands; although it’s a bit too early in the year for blood-sucking arthropods to be a problem, I was reminded of the publication a few months ago of a new edition of ‘Ticks: your pets, your family and you’, by Alison Blackwell, George Hendry and Darrel Ho-Yen (for details see the publisher’s website at http://www.mercatpress.com). George Hendry is the author of the best-selling ‘Midges in Scotland’, and the newer book provides a similar account of ticks in the UK, scientifically rigorous but easily readable by the general public. It aims to make people aware of the dangers of tickborne diseases while reassuring anyone who might have been alarmed by exaggerated rumours. While researching this article I also discovered that the week before Easter was Tick Prevention Week in the UK – see http://www.tickpreventionweek.org.

Tick populations can reach hundreds of thousands per hectare (tens per square metre), and are not confined to upland areas – indeed mountain tops are too exposed for them, and they are present in London’s Richmond and Bushy Parks. In many years of hill-walking I have only noticed a few tick bites, perhaps a couple of dozen at most; but looking at the life-size illustrations of tick larvae and nymphs in the book I wonder how many times I’ve been bitten by a tick too small to notice.

The best known tickborne disease is probably Lyme disease; I get the impression that this is perceived to be a much bigger problem in North America than in the UK, and the book confirms that much more public information is available there. I wondered how much this reflected a true difference in the prevalence of infection and how much it was just perception, so I did some investigation in CAB Abstracts. This revealed an interesting article (Davidson, M. M. et al: Scottish Medical Journal (2003) 48 (1), pp. 6-9) indicating among other things that the annual incidence in Scotland had been calculated at between 1.25 and 16.5 per 100 000, but that even in areas with significant numbers of infected ticks the risk of infection is low. Further investigation revealed that although the incidence in the USA as a whole is comparable to that in Scotland, the disease there shows a strong geographic concentration in the north-east and north-central regions, where the incidence in some states is much higher – over 130 per 100 000 in Connecticut in 2002 (Bacon, R. M. et al.: Morbidity and Mortality Weekly Report (2004) 53 (17), pp. 365-369). On both sides of the Atlantic there is suspicion that the recorded figures may be underestimates.

There are of course other tickborne diseases in Britain, North America and elsewhere (at least we in the UK don’t have to worry about the tickborne encephalitis that lurks not far away in Central Europe), and climate change may increase the risks (ticks flourish in warm wet climates) but it appears that although the comparative lack of concern about Lyme disease in Britain may need to be addressed, it is not purely due to complacency. This would support the overall message of Blackwell et al’s book, which could perhaps be summarised as ‘be aware, and take precautions, but don’t panic’.

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