Atypical Typhus

This is the third of 16 student posts, guest-authored by Mary Egan.

Murine typhus has been in the news recently in Austin, TX, where in May of this year, two people were found to be positive and one died.  This rings a number of alarm bells for me, since I live in Texas, and specifically in Austin.  I know of another Austin veterinarian who got sick with murine typhus in 2008, when it was first noticed in Austin and investigated by the CDC.  I was also working as a relief vet at the Town Lake Animal Center, the municipal shelter, and at the Austin Humane Society, the main nonprofit adoption shelter which has a feral cat Trap-Neuter-Return surgery clinic, when the CDC investigators came to Austin.  They collected blood samples on local animals and also fleas.  Of course, at that time I wasn’t particularly interested in public health, just shelter medicine, and it didn’t really register.  Now I wish I could’ve gone back and tagged along to see more of what they were doing!

Murine typhus is an odd and off the radar disease.  It doesn’t help that murine and typhus are both words with multiple meanings.  Murine is a word that refers to mice, in Latin, murinus, or mouse, in Latin, mus.  It is also a type of eye drops and also a brand of ear wax remover.  How putting mice in your eyes or ears helps them is a mystery to me.  Murine also sounds very similar to marine, so it’s not unreasonable to start picturing typhus near the ocean, which is an odd coincidence, since murine typhus actually occurs primarily in coastal areas.

Typhus itself is a confusing word.  It comes from the Greek, and means hazy, which is how your brain feels if you’re infected.  It is not the same as typhoid fever, which is caused by Salmonella typhi, a bacteria that can cause food borne illness resulting in diarrhea and vomiting.  This is not that.

The typhus we are interested in is a tiny bacteria from the family Rickettsia.  And of course there is more than one type of typhus, to confuse the issue further.  Epidemic typhus is the ancient disease that has been a major player in history.  It was first noted in the Spanish blockade of Granada in 1489, and then killed more of Napoleon’s army than the Russians.   This is Rickettsia prowazekii, which is carried on lice and affects humans.  This is the typical typhus.  If you ever read just “typhus” it is referring to this type of typhus.  It has also been called jail fever, since many old jails were breeding grounds for lice, and the prisoners were more likely to die of infection than be hung for their misdeeds.  This typhus can cause a rash, fever, severe headache, joint pain, kidney failure, delirium, stupor, and even death in 10-60% of cases if it’s not treated.  A blood test will show if there are antibodies to typhus if you go to your doctor with these signs.  There is an effective treatment, a course of antibiotics that kills the rickettsia, and supportive care depending on how far along the disease had progressed.  It is possible for the agent to go underground, and then reappear later in life.  Then it is called Brill-Zinsser disease and is often a very mild form of epidemic typhus, still treated with antibiotics.

The typhus that showed up in Austin is murine typhus, also called Rickettsia typhi, and it is carried on fleas and primarily affects rats.  This is also called endemic typhus because it is pretty much always present on rats in the environment.  Humans historically get it as a side product of coming into contact with rats carrying the infected fleas.  This disease is usually not as severe as epidemic typhus, but can still cause all the same signs and symptoms, and rarely can lead to death if not treated.  Less than 2% die of murine typhus if it is not treated with antibiotics.

Murine typhus has a worldwide distribution, but in the United States it is usually seen near coastal areas in California, Hawaii, and Texas.  The 2008 cases were odd that they were in Austin, in central Texas.   In the previous 25 years, there had only been four cases total.  In 2008 there were 13 cases in the four months from March to July, and a total of 33 cases by October.  Of these, 70% of the people infected were hospitalized with myalgia, severe headache, and fever, and the most severe cases were treated for pneumonia, kidney failure, and coagulopathy.   There were no deaths.  This outbreak showed that aside from the normal rat-flea cycle, there are likely other cycles that involve domestic and feral cats, opossums, dogs, and the fleas that live on them.  And consequently, the fleas that live on domestic cats and dogs then live in the yards and homes of their owners, and then can live on the owners themselves.

The cases were clustered in the central Austin area, with a large percentage coming from one zip code that contains a large portion of the exceedingly popular Town Lake Hike and Bike Trail used by over 20,000 people daily, and the smaller but more wild Shoal Creek Trail.  There have been reports of coyote sightings and suspected killings of family pets in this zip code.  So there is ample space for wildlife within this urban environment.  This also means there are plenty of hosts for fleas.  And Austin in general and this neighborhood in particular is known for a slightly hippy, crunchy granola lifestyle preferring organic and natural everything, with easy access to the outdoors and hiking trails.  It is not surprising this outbreak occurred in this area.

So what does all this mean?  Diseases which were previously uncommon are now becoming more common due to changes in lifestyle.  People want to live close to nature and have trails to walk their dogs.  There is nothing wrong with that.  It’s the parasite hitchhikers their pets pick up and bring home that’s the problem.  And changes in behavior where dogs are now not only in the house, but often in the bed with their owners, means that those fleas have a chance to bite humans.  That doesn’t mean you shouldn’t walk your dog on the trail.  But it does mean you need to use protection.  Spray yourself and your clothes with a flea killing insecticide such as DEET when out walking.  Wear boots, long pants, and long sleeved shirts.  Use appropriate flea control on your pets.  Kill fleas in your yard or home with appropriate premises control measures.  It’s great to be one with nature, you just don’t want that nature to bite back with a case of murine typhus.

Bibliography

1.  Adjemian J, Parks S, McElroy K, Campbell J, Eremeeva ME, Nicholson WL, et al. Murine typhus in Austin, Texas, USA. Emerg Infect Dis. 2010 Mar.   Accessed June 13, 2012.  Available at: http://wwwnc.cdc.gov/eid/article/16/3/09-1028.htm

2.  James C.  Two cases of typhus in Travis County.  KXAN web site.  Accessed June 13, 2012.  Available at: http://www.kxan.com/dpp/news/local/austin/2-cases-of-typus-in-travis-county

3.  Typhus.  Wikipedia website.  Accessed June 13, 2012.  Available at: http://en.wikipedia.org/wiki/Typhus.

4.  Murine typhus.  Texas Department of State Health Services website.  Accessed June 13, 2012.  Available at: http://www.dshs.state.tx.us/idcu/disease/murine_typhus/information/

5.  Conlon J.  The historical impact of epidemic typhus.  Accessed June 13, 2012.  Available at: http://entomology.montana.edu/historybug/typhus-conlon.pdf.

6.  Google map of 78703 zip code.  Google maps website.  Accessed June 13, 2012.  Available at: http://maps.google.com/maps?oe=utf-8&rls=org.mozilla:en-US:official&client=firefox-a&q=78703&um=1&ie=UTF-8&hq=&hnear=0x8644b55c47d7dc5f:0x717c8b7186632905,Austin,+TX+78703&gl=us&ei=i7DTT9vPJsLQ2AX54riFDw&sa=X&oi=local_group&ct=image&ved=0CHQQtgM

7.  Gonzales R.  Santa Ana announces flea-borne typhus alert.  Orange County Register website.   Accessed June 13, 2012.Available at: http://www.ocregister.com/news/santa-356066-control-typhus.html

8.  Roving pack of coyotes mauls pets.  KXAN website.  Accessed June 13, 2012.  Available at: http://www.kxan.com/dpp/news/local/austin/roving-pack-of-coyotes-maul-pets