Case Definition
Clinical evidence1 of infection with likely exposure history2 and lab confirmation using:
- Serological evidence of a fourfold change in IgG titre reactive with Rickettsia2 antigen by indirect immunofluorescence assay (IFA) between paired serum specimens (one taken in the first week of illness and a second 2-4 weeks later)
OR
- Detection of Rickettsia2 nucleic acid in a clinical specimen via amplification of a specific target by PCR assay
OR
- Demonstration of Rickettsia2 antigen in a biopsy or autopsy specimen by immunohistochemistry (IHC)
OR
- Isolation of Rickettsia2 from a clinical specimen in cell culture
Clinical evidence1 of infection with likely exposure history2 and one of the following:
- A single elevated (≥ 1:256) IgG titre reactive with Rickettsia2 antigen by indirect IFA with no other known cause
OR
- Epidemiologically linked to a confirmed case
1Clinical evidence is defined by any reported fever and one or more of the following: rash, eschar, headache, myalgia, anemia, thrombocytopenia, or any hepatic transaminase elevation.
2Rickettsia rickettsii (Rocky Mountain spotted fever) is currently the only pathogen caused by Rickettsia spp. bacteria that is required to be reported to public health in British Columbia. Diagnosis of Rocky Mountain spotted fever should be made by assessing clinical evidence and exposure history and other possible causes should be ruled out. False positive IgG IFA titres as a result of auto-immune disorders or other bacteria are rare but have been reported. Serological interpretation is further complicated due to cross-reactivity between Rickettsia species.
