July
2007
Rocky Mountain Spotted Fever
Rocky Mountain Spotted Fever (RMSF) is a tick-borne disease by a bacterium called Rickettsia rickettsii. Even though RMSF sounds like it is only in the Rocky Mountains (where it was first described), it occurs throughout all the Americas. It is most prevalent in the Southeastern and South Central states. North Carolina has a larger percentage of cases, though there aren’t that many cases overall. In 2004, 1,454 cases of RMSF were reported to the CDC.
I’m writing about this because a viewer/reader in Charlottesville, VA asked me to talk about it because her husband was severely affected by RMSF this year (2007). Rural and suburban regions have the most cases of RMSF though some cases from parks in NYC have been reported!
Spring and early summer is when RMSF appears the most, as most tick-borne illnesses are. Outdoors people are obviously most at risk – so, white men. Most cases are in people aged 40-64. Dog can carry the infected ticks and pass them on to their owners.
The common brown dog tick (Rhipicephalus sanguineus – wow say that 3 times fast, or at all) may be a vector (carrier) for RMSF. Possibly infection can occur without a tick bite, in which contamination might be due to contact or inhalation with tick poop or tick tissue.
Clinical: Incubation period is 2-14 days, but most occur a week after infection. Flu like symptoms occur first – in particular a fever, as in the name for RMSF. So there are headache, body aches, nausea. Belly pains occur usually in children. The RASH! That is why RMSF has its name. But it takes 3-5 days for the rash to develop after the flu symptoms occur. So that makes it difficult to diagnose RMSF initially. The rash starts on the ankles and wrists, spreading out from there including to the soles and the palms. It is red and very evident because they aren’t tiny – they are like large constituency of small dots to form polka dots. It isn’t an itchy rash nor like hives. However, 10% of cases don’t get the rash. Or in darker skinned folks, it might be missed. “Spotless RMSF” can be fatal because without seeing the rash, treatment is more likely to be started too late – and with RMSF, starting treatment soon is vital. After 5d of RMSF symptoms, the mortality rate increases with delayed treatment. One study showed those treated in the first 5 days vs. after the 5th day, the mortality rate was 6.5% vs 22.9% respectively. Though it is estimated the overall mortality rate is less at 3.3%. RMSF can cause bleeding, swelling, coughing, confusion, neurological problems including seizures. Gangrene can develop in the fingers, toes, ears, and in men the scrotum. Eventually all the internal organs can fail.
Diagnosis: blood tests can be falsely negative in the early stages of RMSF. So treatment is often initiated upon clinic history and physical exam. The blood test usually doesn’t pop up positive until 7-10 days after symptoms started. This IFA test is 95% sensitive 14-21d after the onset of illness. There is not a test for the tick itself should a patient bring it in.
Treatment: the antibiotic of choice is tetracycline. But in kids with growing bones (or a fetus in a pregnant woman), it can cause tooth and bone problems. Chloramphenicol is an alternative antibiotic. 1 week of antibiotics is usually curative.
Prevention: avoid tick bites. DEET so far is the only proven bug repellent against tick bites. Make sure you check your dog everyday for ticks. Check for ticks on the body everyday. It is estimated it takes about 24 hours for a tick to transmit disease to a person. Prophylactic antibiotics are not recommended. There is no vaccine.
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drjohnhong 
Uncategorized, infections 
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