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April 18, 2013

Tick Update – Western Fence Swift

Western Fence Swift

Following my recent blog article on deer ticks @scientificamerican, a reader commented that there was no mention of the miracle of the Western Fence Swift , more commonly known as the Bluebellied Lizard. Being a Brit and having lived on the East Coast for the past 20 years, I had never heard of it before, but it is an amazing story.

Lyme disease, characterized by fever, headache, fatigue and a bullseye rash, is spread through the bite of ticks infected with the bacterium,¬†Borrelia burgdorferi. However in the western US, the Western Fence Swift actually cleanses the tick of the bacteria. Apparently, the swift has a protein that kills ¬†Borrelia burgdorferi as it feeds on the swift’s blood.

Since 90% of nymph ticks feed on the lizard, it has always been assumed that the presence of the fence swift has accounted for the lower incidence of Lyme Disease in the western states.  Unfortunately, over the past few years the numbers of western fence swift have been declining. As a result, the concern has been that there would be a corresponding increase in Lyme disease infections. However, a 2011 UC Berkeley study found that 95% of nymph ticks failed to find another host and presumably died. Such is the complexity of Nature and disease.