BackgroundMediterranean Spotted Fever (MSF), whose etiological agent is R. conorii, is one of the oldest described vector-borne infectious diseases. Although it is endemic in the Mediterranean area, clinical cases have also been reported in other regions. R. massiliae-Bar29 is related to MSF cases. This strain is distributed worldwide. R. conorii and R. massiliae-Bar29 are transmitted by ticks. Dogs are considered the sentinel of R. conorii infection. Cats could also be involved in their transmission. Rickettsia felis, etiological agent of Flea-borne spotted fever, is mainly transmitted by the cat flea, Ctenocephalides felis. Up to now, the role of cats in its transmission is not entirely elucidated. The aim of the study is to analyze the infection in cats by these microorganisms.MethodsThe study was undertaken in Northeastern Spain. Twenty municipalities of seven regions participated in the study. 212 cats (pets and stray cats) were analyzed. Variables surveyed were: date of collection, age, sex, municipality, source, living place, outdoor activities, health status, type of disease, contact with other animals, and ectoparasite infestation. Sera were evaluated by indirect immunofluorescence antibody assay (IFA). Molecular detection (real-time PCR and sequencing) and cultures were performed on blood samples.ResultsThere were 59 (27.8%) cats seroreactive to one or more microorganisms. Considering cross-reactions, the seroprevalences were 15.6%-19.5% (R. massiliae-Bar29), 1.9%-6.2% (R. conorii), and 5.2%-7.5% (R. felis). A weak association was observed between SFG seropositivity and tick infestation. Ticks found on seropositive cats were Rhipicephalus pusillus, R. sanguineus and R. turanicus. DNA of Rickettsia was detected in 23 cats. 21 of them could be sequenced. Sequences obtained were identical to those sequences of SFG rickettsiae similar to R. conorii and R. massiliae. No amplification of R. felis was obtained.ConclusionsCats can be infected by SFG rickettsiae and produce antibodies against them. Cats may play a role in the transmission cycle of R. conorii and R. massiliae-Bar29, although the role in the R. felis cycle needs further analysis.

Dogs are considered to be the sentinels of Rickettsia conorii infection, which is the causative agent of Mediterranean spotted fever, one of the most prevalent tick-transmitted disease in our area. It is transmitted by the dog tick, Rhipicephalus sanguineus. This tick is relatively host-specific, and rarely feeds on people unless its preferred host-the dog-is not available [1]. This tick is active from spring to autumn, but climatic changes influence its activity and, consequently, Mediterranean spotted fever epidemiology [2].As canine serology constitutes a useful epidemiological marker [3], the objective of this study was to evaluate the presence of R. conorii in dog populations subjected to different exposure to R. sanguineus. For this purpose, three seroepidemiological studies were designed: serosurvey in dogs with close contact with ticks, seasonal differences in antibodies to R. conorii in dogs subjected to natural tick infestation, and a comparison of canine seroprevalence rates obtained in 1997 and in 2007 in dogs regularly treated for ectoparasites. M A T E R I A L S A N D M E T H O D SBlood samples collected by cephalic venipuncture were allowed to clot. Serum was stored at )80°C until being analysed. A questionnaire was completed at the time of sampling, providing information about modus vivendi (shelter, flat, kept in yard, garden, farm), purpose (pet, hunting, breeding, shepherd, guard), and ectoparasite treatment. Dog sera were tested for IgG antibodies to R. conorii by an indirect immunofluorescence antibody test (bioMérieux, R. conorii spot-IF, Marcy l'Etoile, France). All sera were screened at 1 : 40 dilution. Positive sera were then titrated in a two-fold dilution. The Epi Info v.3.3.2 software package was used for statistical analysis.STUDY I: One hundred and thirty canine sera were collected from dogs living in the countryside around Barcelona (Delta del Llobregat). Serum samples were collected during the summer.Most of the dogs lived outdoors (n = 103). Ninety-eight of 130 were guard dogs, 12 were hunting dogs, eight were pets, eight were kenneled, and four were sheep dogs. None of them received ectoparasite treatment.STUDY II: Nine dogs exposed to natural tick infestation were investigated for 17 months for detection of IgG to R. conorii. Dogs were clinically explored, and sera were collected monthly. Sera were diluted 1 : 20 in a two-fold dilution until titration.STUDY III: In 1997, 74 canine sera were collected from spring to autumn in different veterinary clinics in Barcelona province. All of them systematically received an acaricide treatment. Dogs lived in flats (48.5%), gardens (40.9%), farms (7.6%) and breeding kennels (3%). In 2007, 70 canine sera were collected in the same area during the same period of time. Dogs were living in shelters and were treated for ectoparasites monthly.

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