Rocky Mountain Spotted Fever in Mississippi: Survey for Spotted Fever Antibodies in Dogs and for Spotted Fever Group Rickettsiae in Dog Ticks1

Abstract

During epidemiologic studies of Rocky Mountain Spotted Fever in Mississippi in 1973, dogs were surveyed for antibodies tp spotted fever group antigens and for tick parasites infected with rickettsiae of the spotted fever group. Fifty-three (46%) of 116 serum samples had complement-fixing antibody titers greater than or equal to 1:8 as compared to only one (5%) of 21 samples from a group of dogs obtained from metropolitan Chicage. Fifty-two per cent of the dogs tested from Mississippi had microagglutinating antibodies titers greater than or equal to 1:8; 9% of dogs from Chicago had similar titers. Rickettsia rickettsii was demonstrated in only one (0.8%) of 129 Dermacentor variabilis removed from Mississippi dogs. Quite unexpectedly, 167 (18.9%) of 884 Rhipicephalus sanguineus taken from these dogs contained spotted fever group rickettsiae.

Experimental infection of dogs with a Brazilian strain of Rickettsia rickettsii: clinical and laboratory findings

“…Therefore, seropositivity may not necessarily indicate a very recent infection. On the other hand, long periods of seroreactivity highlight the important role of dogs as sentinels for surveillance of RMSF or BSF (Sexton et al 1976, Lemos et al 1996, Paddock et al 2002, Sangioni et al 2005) since a seroreactive dog indicates circulation of spotted fever group rickettsia in a given area, at least within the previous 6-12 months.…”

Serologic Evidence for Exposure toRickettsia rickettsiiin Eastern Arizona and Recent Emergence of Rocky Mountain Spotted Fever in This Region

“…Clinical illness follows a bite from an infected tick, and is characterized by fever, rash, and possible complications, including encephalitis, respiratory disorders, and coagulopathy; case-fatality in untreated patients may be as high as 30% (Dalton et al 1995). RMSF may also cause a similarly severe or fatal illness in dogs, and dogs may serve as sentinels for risk of disease in humans (Gordon et al 1984, Hinrichsen et al 2001, Keenan et al 1977a, Keenan et al 1977b, Magnarelli et al 1982, Norment and Burgdorfer 1984, Sexton et al 1976. RMSF is widely distributed throughout the eastern, south-central, and mid-western United States, corresponding to the distribu-tion of the American dog tick (Dermacentor variabilis) and the Rocky Mountain wood tick (Dermacentor andersoni), the expected tick vectors (Comer 1991).…”

Short report: concurrent Rocky Mountain spotted fever in a dog and its owner.

“…Subsequent descriptions of temporally associated RMSF in dogs and family members have been briefly noted from other locations in the United States, including Washington, D.C.; Maryland; Mississippi; Connecticut; and Ohio. [2][3][4][5][6] Because RMSF occurs sporadically and can be a difficult diagnosis for veterinarians and doctors, cases in dogs and humans may be missed. In this report, we describe a case of fatal canine RMSF diagnosed at necropsy, resulting in testing for and diagnosis of the same disease in the dog's owner.…”

“…1 Reports from other states have documented cases of temporally associated human and canine disease occurring within a period of 14-21 days. 2,4,8 In a hyperendemic focus of RMSF in Clermont County, Ohio, concurrent illnesses were reported in 4 (25%) of 16 dogs owned by families in which 14 confirmed cases of RMSF had occurred. The prevalence of antibodies reactive with R. rickettsii was significantly higher among dogs from case households: 12 (75%) animals associated with human cases had positive antibody titers when tested by immunofluorescence assay, compared with only 1 (0.7%) of 137 stray dogs sampled at animal shelters in another Ohio county where RMSF was endemic.…”