West Coast Lyme Disease System
Lyme disease on the west coast. Yes, it is out here. Although, it is not as common as it is in the east coast and there are numerous hypothesis behind that.
In this blog post I will try to break down all you need to know about Lyme disease. Since I am a tick biologist of the west coast, my perspective will be dominated by the California Lyme disease system.
So first off, Lyme disease is caused by a bacteria that looks like microscopic corkscrews, called Borrelia burgdorferi. Most pathogens thrive off of iron and therefore reside within the hosts blood. Borrelia burgdorferi thrives off of other elements such as manganese, which tends to be within cartilaginous tissues, such as joints. That is one reason why Lyme disease is so tricky to diagnose, because the bacteria doesn’t hang out in the blood. Yet most pathogen diagnosis are blood tests. This is also thought to contribute to the intense arthritis symptom associated with the infection. There are other disease causing Borrelia species of bacteria that are also vectored (or transmitted) by ticks. Some of these diseases cause similar symptoms as Lyme disease, but can usually also be treated with antibiotics.
The only way you can get Lyme disease if you are bitten by an Ixodes species of tick. The most common vector (or transmitter) of Lyme disease. On the west coast those are typically the Ixodes pacificus.
Or Ixodes scapularis on the east coast.
Both species are also considered the “Black legged tick”. Both species have only three life stages. Larva, nymph and adult. They all vary in size where larvae look like a freckle or a poppy seed. The nymphs are about the size of a sesame seed and adults are about the size of a sunflower seed.
As they feed on blood they become engorged and therefore larger. I have seen an adult female about the size of my thumb nail! She had a full blood meal and was ready to lay her eggs.
Surprisingly, a tick only takes a blood meal twice in their life. They feed to essentially molt into the next life stage. So when they emerge from their eggs they feed on a host, then molt into a nymph. As a nymph they go on a grand quest for a host, if successful they will molt into the adult life stage. As adults, they become sexually active. This is the only life stage that you can tell the sex of the tick. Males do not tend to take a full blood meal. Their anatomy simply will not allow them too. They have really hard bodies that do not expand. So they take little sips at a time, if they find a host. Adults quest for a larger hosts such as deer, mostly because that’s where all the female ticks will be. The main objective of a male is to release his spermatophore into the females genital pore. Once she has this spermatophore, she will take a full blood meal, so her eggs has all the nutrients in order to be laid. Notice the adult females have that redish body coloration, that is their alloscutum. It is a more flexible tissue that allows them to double in size.
These Ixodes species are known to be generalist ticks, rather than specialized ticks. This is in reference to they can be found on a wide variety of different blood meal hosts. Whereas some species of ticks are only found on say birds. Both these Ixodes species tend to feed on small mammals such as rats, mice, shrews, or chipmunks and lizards as larva and nymphs. While adults are typically found on larger animals such as deer. This is in part because the size of their mouth parts and the response from the host.
On the west coast, the Ixodes pacificus larval and nymphal stages have shown to have a preference for feeding on the Western fence lizard (Sceloporus occidentalis). This has been demonstrated in lab setting, where ticks were set up with a choice of hosts, and they always picked the lizard. This has also been shown in the field, via when trapping lizards and small mammals, the lizards tend to have much larger tick burdens than the rats and mice. We aren’t entirely sure why the ticks prefer the lizard. Some suggest its life history traits between the different hosts, while other suggest it is more to do with pheromones or chemical signals. It is most likely a combination of these mechanisms. What is really exciting about this lizard and tick relationship, is there is an borreliacidal element to the lizards blood. So it’s almost like a cure for the tick if it’s infected with Borrelia burgdorferi. A blood meal from the lizard will clear out most bacteria within the tick.
On the east coast there is also an eastern fence lizard, but their home range is more southern and therefore isn’t a player in the north east Lyme disease area.
Other small mammals on the west coast such as the dusky-footed woodrat, western grey squirrels, and deer mice are all host of juvenile Ixodes pacificus ticks and can maintain an infection of Lyme disease.
We are not really sure the health impacts cause on these small mammals or how long they are infected for. But we do know that these are the hosts that re-infect a lot of the ticks when they feed on them. This is important since a lot of larvae feed on these small mammals this is the first time that they can become infected with Borrelia burgdorferi. When a larvae becomes infected it stays infected through the molting process. So then this is when it becomes a risk to humans. Because now that it is an infected nymph it will be on the quest for a new blood meal.
When humans tend to get infected with Lyme disease it is typically by and infected nymph that feed on them. Since they are still small enough to not be felt or recognized on your skin and they are at higher risk for being infected. Since larvae don’t emerge from egg infected, typically if you were to notice one attached to you, you should be uninfected. And adult ticks, humans usually feel the bite immediately and take them out. Here is another super cool fact about Borrelia burgdorferi, it likes to snuggle into the stomach of a tick. So it takes at least 24 hours for it to travel from the tick into the hosts bloodstream. Therefore, if you feel a tick bite and remove it carefully with tweezers, before 24 hours that it has been attached, then you should not be at risk for Lyme disease! Now there are other tick borne diseases that can be transmitted much faster than 24 hours, so be aware of those.
So to wrap this up here are my big take homes for all of this loaded information.
There are about 900 species of ticks around the world. About 90 of those are in the United States, and only 2 of those species will typically transmit Lyme disease to humans.
If you find a tick feeding on you and you gently remove it with tweezers by getting as close to the mouth parts of the tick as possible, within 24 hours, you should be Lyme free.
The bulls-eye rash is a reaction to Borrelia burgdorferi. Although it only occurs within 75% of the time.
Lyme disease can be treated with simple antibiotics if you go to the doctor in a timely manner.
Chronic Lyme is still not understood: if the bacteria is still within your body or if the effects/symptoms are from long lasting damage of the bacteria. Kind of similar to the way polio works.
If you get a tick attached to you, carefully remove with tweezers. DO NOT BURN IT OUT, do not suffocate it with Vaseline. Burning or placement of tweezers not at the base of the head could cause the ticks insides (i.e. pathogens)to be regurgitated back into you!
There is an increase in new tick borne pathogens, we do not know if this is due to an increase in scientific methods of testing or a true increase in diseases.
Tick home ranges are expanding.
ABOVE ALL, CHECK YO’SELF BEFORE YOU WRECK YO’SELF (FOR TICKS)! The best way to prevent tick borne diseases is know which ones you are at risk for and understanding those risks. Most of the risks can be limited by thoroughly checking yourselves while hiking and camping or the use of repellent.
If you have any questions feel free to email: jsalomon@mail.sfsu.edu ! No matter how silly you feel like the question is, just ask the tick chick.
Here are some good resources to learn more about ticks and Lyme disease:
www.sweilab.com
https://www.cdc.gov/lyme/index.html
https://www.tickproject.org/people.html
http://www.wcsuticklab.com/
https://www.youtube.com/watch?v=_IoOJu2_FKE
https://www.lymedisease.org/new-borrelia-species-robert-lane/