Study Of Pet Dogs Shows Lyme Disease Risk In UK Bigger Than Previously Thought

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Main Category: Infectious Diseases / Bacteria / Viruses
Also Included In: Veterinary;  Public Health
Article Date: 25 Jan 2012 - 13:00 PST

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The risk of a person living in the UK becoming infected with Lyme disease is much greater than previously thought, according to a study from Bristol University that surveyed pet dogs to find out how many of them harboured the ticks that transmit the disease. The researchers, from Bristol University, reported their findings earlier this month in the journal Comparative Immunology, Microbiology and Infectious Diseases.

Lead author Faith Smith, of Bristol's School of Biological Sciences, said in a statement released on Wednesday that Lyme disease is a growing problem in the UK. It is going to spread more and more unless surveillance and routine testing improve considerably.

She said the health and economic impact will be felt as loss of working hours and fewer tourists visiting places where ticks are prevalent.

"In particular, future warmer winters might well extend the period over which ticks are active seasonally, while growing wild reservoir host populations, such as deer, will allow the tick population to expand," she explained.

Lyme disease is a debilitating chronic infection, caused by Borrelia burgdorferi, a bacterium that spreads to humans and other animals, including dogs, when they are bitten by infected ticks.

In humans, one of the earliest signs of Lyme disease is a characteristic red rash that spreads from the tick bite, followed by what feels like the flu. The symptoms are less clear and harder to spot in dogs.

Chronic forms of the disease can last many years. If left untreated, it can lead to arthritis and neurological problems, including nerve damage, paralysis and blindness.

Experts have suspected for some time that Lyme disease is on the increase in the UK, but consistent surveillance figures are lacking, say the Bristol researchers.

Since 2000, the numbers of reported cases are thought to have increased fourfold: from 0.38 per 100,000 of the UK human population to 1.79 per 100,000 in 2009.

In 2010 there were just under a thousand reported cases of Lyme disease in humans in England and Wales, but the authors reckon the number of real cases is likely to be much higher than this due to under-reporting.

So Smith and colleagues set out to estimate the numbers by using pet dogs as "sentinels". Since pet dogs largely share the same environment as humans, then finding out how many carry ticks infected with Lyme disease is a plausible indicator of the exposure risk to humans.

For the study, they inspected 3,534 dogs selected at random while they visited veterinary practices in England, Scotland and Wales over a 6-month period (March to October 2009).

They found 14.9% of the dogs had ticks. Of the 739 tick samples that could be tested, 17 tested positive for the Borrelia bacteria, which means about 2.3% of the ticks they found were infected with Lyme disease.

This translates to about 481 infected ticks per 100,000 dogs.

The researchers conclude that this would suggest, since there is a big difference between 481 and 1.79 per 100,000, that the recent estimates are much too low.

Funds from the Natural Environment Research Council (NERC) and Merial Animal Health Ltd helped pay for the study.

Written by Catharine Paddock PhD
Copyright: Medical News Today
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