April-September when ticks are active and humans are frolicking outside to get bitten
Clinical Presentation for E and R
general malaise, headache, fever, and myalgias. 80% won't know they've been bitten, so check for risky activities in past 2 weeks. Only 20% of R pt present with rash, but rash may develop. E less likely to have rash. neutropenia, thrombocytopenia, and anemia support. Vasculitis is hallmark. May see encephalitis
If suspected, and should include in differential Dx, treat with Doxicycline. Not commonly used in hospital, so if you don't think about it, pt will die. Only justifiable pediatric admin of doxicycline. Pregnancy needs rifampin
RMSF & HME
SE b/c of tick distribution (Star-tick) or Western coast (not E.) because of W. Black legged tick
invades endothelial cells. small, gm-, pleomorphic bacteria. rarely seen on slide. infer from perivascular infiltration with mononuclear WBCs and small vessel breakdown.
causes 300-400 cases RMSF per yr. 7-14 day incubation
keeps R. and E. around in tick population
children ages 5-9 and men. Ab decreased DR in <16 from 7->2% but >16 25->7% so age increases mortality risk
greater than one dilution change b/w one month. F/u decreases biologic false (-) but still likely to have biologic false (+). Ab, serum, and reagent must be exact.
IFA and Latex agg
2 serotests used. Both specific, latter not as sensitive. Used in conjunction to decrease false + for syphilus, HIV, and lyme disease
IF or Immunoperoxidase biopsy stain, culture
useful for academic and epidemiologic ID of E and R diseases
infects WBCs (monocytes, macrophages, and PMNs) forming morula (endovascular) in cytoplasmic vacuoles. Veterinary infection as well. 5-10 day incubation
E. chaffeensis. SE region
A. phagocytophilia and E. ewingii in midwest, New England, and Europe.
causes non-tick asc rickettsial disease called Q fever.