Survey shows new ticks have moved to UK

25 March 2011 by Tom Marshall

A new study has confirmed that an invasive alien species of tick has taken up residence in southern England.

Tick

The arachnid invaders had already been detected, but this is the first indication that it has established a breeding population. More broadly, the paper also shows that ticks are more common on British dogs than previously thought.

It raises concerns about the potential for more tick-borne diseases in both animals and people. These concerns are only likely to grow over time, as climate change is expected to make the UK more hospitable to ticks that have until now been confined to warmer climes.

"This is the first large-scale systematic study of ticks on British dogs," says Faith Smith, a PhD student specialising in ticks in Bristol University's Veterinary Parasitology Group and lead author of the research. She notes that previous research on the subject has tended to focus on animals already known to have ticks, rather than on a random sample of the dog population.

'We hope our work will provide a baseline to let us track future changes in the UK's tick population. It could also help us predict the effects of climate change on tick distributions and disease spread,' she adds.

This is an important study because the results suggest that the risk of tick infestation is far higher in dogs than was previously thought.

- Professor Richard Wall, Bristol University

Ticks can transmit infections including Lyme disease; Smith is now investigating which diseases the ticks found during the study were carrying.

The study was published in Medical and Veterinary Entomology, and is based on a survey of 173 veterinary surgeries across the UK. Each vet was asked to pick five dogs a week and check them for ticks. They looked at dogs brought in for any reason, not just those they already had reason to think were carrying ticks.

In total, 3,534 dogs were examined, and 810 had at least one tick on them. Gundogs, terriers and pastoral breeds like sheepdogs were the most likely to be tick-infested, perhaps partly because they tend to spend more time in environments where the parasites lurk. In general, shorter-haired hounds were less likely to be infested.

Scientists from Bristol conducted the study in collaboration with Merial Animal Health, a company that makes veterinary products. Merial helped put the researchers in touch with vets all over the country.

The new tick species, Dermacentor reticulatus, appeared five times. Recent studies suggest this species is spreading into more northerly parts of Europe, and being found at higher altitudes, as the climate warms. Infection rates were highest in June and lowest in March.

"This is an important study because the results suggest that the risk of tick infestation is far higher in dogs than was previously thought," says Professor Richard Wall, head of the group at Bristol and co-author of the study. "This has serious implications for the incidence of tick-borne disease. The study also confirms that a non-native species of tick, which is also a major disease vector in Europe, is now established in southeastern England. It will be of considerably interest to monitor its spread."

Ticks live by feeding on their hosts' blood. Many ticks take an adventurous approach to sampling new foods; the most common type in Britain is known as the sheep tick, but will also happily attach itself to other animals including deer, dogs and humans.

The natural barrier of the English Channel and the recently-introduced Pet Passport scheme make it harder for ticks to spread to the UK from continental Europe, but as the new arrival shows, it's not impossible. Dogs entering the country are dusted with a chemical that's meant to kill parasites, but it's not completely reliable.

Smith says there's no reason to worry too much at present, but that owners should consider checking their dogs for ticks after they've been for a walk in tick-rich habitats like long grass, shrubby undergrowth or poorly-drained boggy areas.