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White settlers in the Bitterroot valley of Montana ignored indigenous warnings about vengeful spirits on the valley's West side.
Many settlers who lived on the West side of the valley died from Rocky Mountian Spotted Fever, but East-siders lived.
Why was the East side safe?
Many settlers who lived on the West side of the valley died from Rocky Mountian Spotted Fever, but East-siders lived.
Why was the East side safe?
To really understand this, we need to explore how tick-borne diseases navigate their world.
Parasites don’t live in an environment free of competition.
Sure, they’re competing with their hosts for nutrients.
They’re ALSO competing with things inside the hosts.
Parasites don’t live in an environment free of competition.
Sure, they’re competing with their hosts for nutrients.
They’re ALSO competing with things inside the hosts.
There’s two ways that a tickborne disease can be transmitted.
The first one is the one that everyone’s familiar with.
An infected tick bites a host, and passes the germ onto a new generation of ticks when new individuals feed.
This is horizontal transmission.
The first one is the one that everyone’s familiar with.
An infected tick bites a host, and passes the germ onto a new generation of ticks when new individuals feed.
This is horizontal transmission.
However, ticks can also pass germs onto their eggs through their ovaries.
This is called horizontal, or transovarial transmission.
Both of these are important to RMSF’s survival, because dual transmission increases the chance of completing another cycle in the wild.
This is called horizontal, or transovarial transmission.
Both of these are important to RMSF’s survival, because dual transmission increases the chance of completing another cycle in the wild.
We want to understand how these bacteria work…and over the years, the Bitterroot valley has turned into a kind of laboratory for how bacteria compete inside ticks.
You see, in the Bitterroot valley, there are two different bacteria circulating in these ticks.
You see, in the Bitterroot valley, there are two different bacteria circulating in these ticks.
R. rickettsiae is the one we know as RMSF.
The other, lesser known bacteria, is R. peacockii, or what’s called the East Side Agent
Both of these bacteria compete for space in the next generation of tick, but they do so in very different ways.
The other, lesser known bacteria, is R. peacockii, or what’s called the East Side Agent
Both of these bacteria compete for space in the next generation of tick, but they do so in very different ways.
R. rickettsiae is pretty adept at getting into the ticks through their mouths, but R. peacockii is really good at passing on through the ovaries.
R. rickettsiae makes the ticks really sick, while R. peacockii is less hard on the host.
R. rickettsiae makes the ticks really sick, while R. peacockii is less hard on the host.
RMSF has a harder time maintaining it’s foothold in the cycle, and R. peacockii takes advantage of a natural ‘choke point’.
Eggs can’t maintain both bacteria at the same time.
R. peacockii tends to win this fight and outcompetes RMSF when they’re in a shared habitat.
Eggs can’t maintain both bacteria at the same time.
R. peacockii tends to win this fight and outcompetes RMSF when they’re in a shared habitat.
Getting outcompeted for the next generation of hosts explains why some tick populations don't get RMSF.
So, if there’s a stronger competitor, why does RMSF even exist if these ticks can easily cross the river on their hosts?
This question hasn't recieved as much attention.
So, if there’s a stronger competitor, why does RMSF even exist if these ticks can easily cross the river on their hosts?
This question hasn't recieved as much attention.
If we look at a topographical map, we can see that the two sides of the river are VERY different.
On the West side, there's a lot of mountains.
The East side is flatter, less mountainous, and is just a completely different habitat.
On the West side, there's a lot of mountains.
The East side is flatter, less mountainous, and is just a completely different habitat.
These are older pictures, so we can just look at Google Earth.
The difference between the two habitats is still pretty obvious.
The difference between the two habitats is still pretty obvious.
Ticks are cold-blooded, so their body temperature is always the same as the environment.
Anything living inside of them will be exposed to similar environments.
If the tick is cold, so is the bacteria.
If the tick is hot, so is the bacteria.
Anything living inside of them will be exposed to similar environments.
If the tick is cold, so is the bacteria.
If the tick is hot, so is the bacteria.
This is, of course, a pretty simplistic way to look at it.
What hosts the ticks have access to, even the chemicals in the environment from plants, the bacteria the ticks are exposed to, etc can have significant effects on the bacteria inside the ticks.
What hosts the ticks have access to, even the chemicals in the environment from plants, the bacteria the ticks are exposed to, etc can have significant effects on the bacteria inside the ticks.
Either way, the current idea is that the habitat on the West side of the river does something to help out RMSF while the environment on the East side of the river benefits R. peacockii.
Since R. peacockii outcompetes RMSF, you get a separation between two close environments.
Since R. peacockii outcompetes RMSF, you get a separation between two close environments.
A post to acknowledge our sources:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4018725/pdf/nihms80080.pdf
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4018725/pdf/nihms80080.pdf
We'd like to thank everyone who was interested in this topic from the start!
The reception we've received has been so cool, and so heartwarming.
It's a really cool story, and we're glad so many people have been curious about it!
The reception we've received has been so cool, and so heartwarming.
It's a really cool story, and we're glad so many people have been curious about it!
