Family Cluster of Rocky Mountain Spotted Fever

Abstract

Soon after a patient from Tennessee died of Rocky Mountain spotted fever (RMSF), several family members developed symptoms suggestive of the disease and were treated presumptively for RMSF. Fifty-four persons visiting the index patient's home were interviewed; serum samples were collected from 35. Three additional cases of RMSF were confirmed, all of which occurred in first-degree relatives. Time spent at the family home and going into the surrounding woods were significantly associated with developing antibodies to Rickettsia rickettsii. Ticks were collected and examined for rickettsiae by polymerase chain reaction analysis. Because hyperendemic foci and family clusters of RMSF can occur, when a case is suspected clinicians should be vigilant for signs and symptoms consistent with R. rickettsii infection in other persons who may have been similarly exposed.

Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses, and Anaplasmosis — United States

“…Temporally and geographically related clusters of illness have occurred among family members (including their pet dogs), coworkers, or persons frequenting a particular common area. Described clusters include ehrlichiosis among residents of a golfing community (80), ehrlichiosis and RMSF among soldiers on field maneuvers (85,86), and RMSF among family members (87)(88)(89). Infections with R. rickettsii and Ehrlichia species have been observed concurrently in humans and their pet dogs (48,83,90).…”

Rocky Mountain Spotted Fever

“…Treatment with chloramphenicol is associated with a higher percentage of fatal outcomes than treatment with tetracyclines. 32,54 Moreover, gray baby syndrome and aplastic anemia that is unrelated to dosage, both rare but potentially fatal complications, have been reported with the use of chloramphenicol. 23,54 Also, the efficacy of chloramphenicol in the treatment of other tick-borne illnesses that may mimic RMSF is uncertain.…”

“…Approximately 40% of patients with RMSF do not report an antecedent tick bite. 32,35,36,43,47,54 In this context, absence of tick bite should never dissuade a clinician from considering RMSF.…”

“…Dependent on the patient's age, untreated RMSF has a 10% to 25% case-fatality ratio. 32,54 Delayed treatment after day 5 is associated with a significantly higher morbidity and mortality. 45,54 Fifty percent of all deaths occur on or before day 8.…”

Fatal Cases of Rocky Mountain Spotted Fever in Family Clusters—Three States, 2003

“…4 Family clusters of infection are a well-recognized feature of RMSF because of shared residence and risks for vector exposure. 5 In its early stages, RMSF can resemble many other infectious and noninfectious conditions and can be difficult to diagnose (Box), even for physicians familiar with the disease. 3,6 The majority of patients do not have the classic RMSF triad of fever, rash, and history of tick bite on their first visit for medical care; often the rash appears several days after onset of fever and can evolve to become petechial.…”