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Office of Binational Border Health

Rocky Mountain Spotted Fever


Rocky Mountain Spotted Fever (RMSF) is a tick-borne disease characterized by fever, headache, rash, and thrombocytopenia, and can lead to sepsis, chronic sequelae, and death. From 2009 to 2014, a total of 752 RMSF cases and 79 fatalities were reported in Mexicali, a Mexican city that borders Imperial County, CA.


Imperial County implemented a project to test if dogs in the area had previously been exposed to Spotted Fever Group Rickettsiae or other tick-borne pathogens. Serum samples collected at rabies clinics were tested against Rickettsia rickettsi, Ehrlichia canis and Anaplasma phagocytophilum. Analysis of test results and the information given by dog owners via surveys was used to assess the status of tick-borne diseases in the region.


Results indicated that Imperial County could be at risk of transmission of imported spotted fever group rickettsiae to resident ticks. Adequate tick prevention and continued surveillance of tick-borne pathogens can help prevent the spread of RMSF and other diseases in this dynamic border region. ​

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