Brown rats, black rats, spotted fever

David Richard Harper D.R.HARPER at MDS.QMW.AC.UK
Mon Dec 16 11:14:02 EST 1996


K. Weber wrote:
> 
>         One explanation for the dwindling of the Bubonic Plague in Britain
> has been that the native black rats were replaced by the European brown
> rat.  A friend of mine and I have been batting this around.  Does anyone
> know whether we have native black rats or brown rats in America?  I assume
> that our domesticated rats are bred from the brown ones.  From my
> observations of these, at least some of them eat fleas during grooming.
> It has occured to me that if the brown rat learned to destroy fleas as
> part of grooming and the black rats had never picked up this habit, that
> this might be one reason that these rats were assumed to not transmit the
> plague.  Did they get it?  When there are outbreaks of plague as happened
> in a high sierra campground in the late sixties (thirty cases), how do the
> host animals (assumed to be squirrels) get the organism.  Can it be
> carried in a benign form?
>         My sister-in-law got a very virulent infection in southern Utah
> about twelve years ago.  In relating the story at church, my mother
> learned that one of her friends had a daughter who was diagnosed with
> spotted fever at the University of Utah.  My sister-in-law was treated at
> the federally funded Santa Clara Health Center in St. George, Utah by a
> retired hematologist who was able to respond quickly.  He removed her
> spleen.
>         We have also been wondering whether it was actually the plague
> which caused the massive die off of rats at the very beginning of the
> plague.  Might something else have set up the conditions necessary for the
> development of virulence in the spotted fever organism.  Are spotted fever
> and bubonic plague the same thing?  Defoe mentions both names in his
> Journal of the Plague Year.  The friend at church did not have rocky
> mountain spotted fever unless there is something important I don't know
> about it.  Her baby was in a coma six hours after contracting it.
>         If you answer this please send me a copy e-mail.  I may not be
> able to pick up all my mail from the groups.
> 
>                                         Kathleen


Rocky mountain spotted fever is caused by Rickettsia ricketsii, and
intracellular bacterium.  Plague is caused by a totally different
organism, Yersinia pestis.  Check out:

http://www.mic.ki.se/Diseases/c1.html

-for information on both.





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