A Second Lizard Helps Prevent Lyme Disease

A few years ago, I wrote a post called Lizards, Ticks, and Lyme. It explained how Western Fence Lizards (Sceloporus occidentalis) have a blood protein that kills the bacteria that causes Lyme Disease, and this is one of the major explanations of why Lyme Disease is so much less common in the Western USA.

Well, new research (see references at the end) has added a really intriguing facet to the Tick-Lizard-Lyme story. This new research focuses on the southeastern USA. The southeast is another area where Lyme Disease rates are very low. But why? The southeastern USA has populations of Black-legged Ticks (members of the genus: Ixodes), which are the ticks that can carry Lyme Disease. The region has the mammal species such as deer and mice that act as reservoirs for Lyme Disease. People in the southwest get bitten by ticks, just like other parts of the country. So why is Lye Disease so much more common in the northeastern USA than the southeastern?

Well, once again, it looks like we can thank lizards. Skinks are a group of smooth-scaled rather lovely looking lizards and they are one of the preferred hosts for ticks in the southeastern USA. In the northeastern USA mice are the much more common host to ticks. And this sets up a roadblock for Lyme Disease in the southeast because skinks have been shown to be really bad transmitters of Lyme Disease. Mice, on the other hand, have been shown to be very effective transmitters of Lyme Disease.

A Southeastern Five-lined Skink (Photo credit: Animal Spot)

It is not yet known if the stinks blood contains proteins that actually kill the Lyme Disease-causing bacteria, or it there is something else about skinks that reduces transmission rates, but this difference in host does help to explain why Lyme Disease rates are so much lower in the southeastern USA as compared to the northeastern USA.

So, fence lizards and skinks both contribute to reducing Lyme Disease in the areas where these lizards are found. Pretty fascinating stuff! I am very much looking forward to learning more about this subject as more research is done. Do other lizard species also reduce the occurrences of Lyme Disease? Does skink blood kill the bacteria that causes Lyme Disease? What is the blood protein that the fence lizards produce that kills the bacteria, and can it be synthesized? So many questions!

I hope you follow this story, and are as intrigued by it as I am. I will certainly write more as more is discovered.

Here are some sources for further reading: a Science News article, and an SF Gate article.

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Lizards, Ticks, and Lyme

Western Fence Lizard (Sceloporus occidentalis). Photo courtesy of Jocelyn Knight.

There is a small lizard that lives all across the western USA that has a superpower! The lizard is the Western Fence Lizard (Sceloporus occidentalis) and the superpower is that it can kill Lyme Disease. This is not a new story, by any means, but it is a great one. It is also a reminder that there are amazing things to discover in our back yards, and that we gain amazing benefits from unlikely parts of the natural world.

So, the story is this. A person in Connecticut is about 100 times more likely to get Lyme Disease than a person in California. Why is this true? This was a puzzle for scientists and public health specialists.

Female Black-legged Deer Tick (Ixodes scapularis). Photo courtesy of Innovative Pest Management.

Many possible ideas have been examined. Is it because there are more ticks in Connecticut? No, there are lots of ticks in both states. Well, only certain species of tick can carry Lyme Disease, so maybe those species occur in Connecticut but not California. No, the species of tick, members of the genus Ixodes, occur in both states. Ok, where do the ticks get Lyme Disease from, maybe the reservoir for the disease is only found on the east coast, but not the west. Nope, the disease is commonly found in many species of mammal, deer particularly, and these animals are found all across North America. Well, maybe people in the two states are not getting bitten at the same rates for some reason. No, the numbers of bits per 100,000 individuals is about the same. But, for some reason, when a person is bitten by a tick in California they very rarely get Lyme Disease.

It turns out that this is because most ticks in California (and I am talking about the members of the genus Ixodes that can carry Lyme Disease, here) don’t actually carry Lyme Disease very often. They can, but they generally don’t.

An entomologist at the University of California, Berkeley (Robert Lane, Ph.D.) figured out why they don’t back in the late 1990s. It turns out that one of the common hosts of ticks in the western USA are Western Fence Lizards and Western Fence Lizard blood contains a protein that kills the Lyme Disease causing organism (a bacteria called Borrelia). In lab tests, Borrelia bacteria that was placed in mouse blood would survived for about three days, but Borrelia bacteria that was place in Western Fence Lizard blood died in one hour! (On a bit of a side note, when I was a kid my family and I actually did some field collecting for this project. When we went hiking in the east bay hills, we would save the ticks we found on ourselves or the dog and take them in to UCB.)

So what happens is that any time a tick bites a Western Fence Lizard, the blood that the tick drinks kills off all the Borrelia in its system. If that tick then goes on to bite you, it has no Borrelia to pass on to you and you do not get Lyme Disease. Pretty cool, right? One of the big, unanswered questions is what protein, exactly, in Western Fence Lizard blood is so lethal to Borrelia?

So, next time you see a Western Fence Lizard say thanks for the Lyme Disease protection. The next time you find a tick on you, don’t panic because it probably has been drinking blood from a Western Fence Lizard and so has no Lyme Disease to give you, unless you are back east in which case you should probably watch for possible Lyme Disease symptoms.

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