title: Acute febrile illness is associated with Rickettsia spp infection in dogs.
abstract: BACKGROUND
  Rickettsia conorii is transmitted by Rhipicephalus sanguineus ticks and causes Mediterranean Spotted Fever (MSF) in humans. Although dogs are considered the natural host of the vector, the clinical and epidemiological significance of R. conorii infection in dogs remains unclear. The aim of this prospective study was to investigate whether Rickettsia infection causes febrile illness in dogs living in areas endemic for human MSF.
  
  
  METHODS
  Dogs from southern Italy with acute fever (n = 99) were compared with case-control dogs with normal body temperatures (n = 72). Serology and real-time PCR were performed for Rickettsia spp., Ehrlichia canis, Anaplasma phagocytophilum/A. platys and Leishmania infantum. Conventional PCR was performed for Babesia spp. and Hepatozoon spp. Acute and convalescent antibodies to R. conorii, E. canis and A. phagocytophilum were determined.
  
  
  RESULTS
  The seroprevalence rates at first visit for R. conorii, E. canis, A. phagocytophilum and L. infantum were 44.8%, 48.5%, 37.8% and 17.6%, respectively. The seroconversion rates for R. conorii, E. canis and A. phagocytophilum were 20.7%, 14.3% and 8.8%, respectively. The molecular positive rates at first visit for Rickettsia spp., E. canis, A. phagocytophilum, A. platys, L. infantum, Babesia spp. and Hepatozoon spp. were 1.8%, 4.1%, 0%, 2.3%, 11.1%, 2.3% and 0.6%, respectively. Positive PCR for E. canis (7%), Rickettsia spp. (3%), Babesia spp. (4.0%) and Hepatozoon spp. (1.0%) were found only in febrile dogs. The DNA sequences obtained from Rickettsia and Babesia PCRs positive samples were 100% identical to the R. conorii and Babesia vogeli sequences in GenBank®, respectively. Febrile illness was statistically associated with acute and convalescent positive R. conorii antibodies, seroconversion to R. conorii, E. canis positive PCR, and positivity to any tick pathogen PCRs. Fourteen febrile dogs (31.8%) were diagnosed with Rickettsia spp. infection based on seroconversion and/or PCR while only six afebrile dogs (12.5%) seroconverted (P = 0.0248). The most common clinical findings of dogs with Rickettsia infection diagnosed by seroconversion and/or PCR were fever, myalgia, lameness, elevation of C-reactive protein, thrombocytopenia and hypoalbuminemia.
  
  
  CONCLUSIONS
  This study demonstrates acute febrile illness associated with Rickettsia infection in dogs living in endemic areas of human MSF based on seroconversion alone or in combination with PCR.
authors.affiliation: Departament de Medicina i Cirurgia Animals, Facultat de Veterinària, Universitat Autònoma de Barcelona (UAB), Cerdanyola, 08193, , Barcelona, Spain. laia.solano@uab.cat.|Royal Veterinary College, University of London, Hatfield, United Kingdom. laia.solano@uab.cat.
authors.forename: Laia
authors.initials: L
authors.lastname: Solano-Gallego
authors.affiliation: Clinica Veterinaria Camagna, Reggio, Calabria, Italy. alessandracapri@hotmail.com.|Dip.to di Scienze Veterinarie, Polo Universitario Annunziata, Messina, Italy. alessandracapri@hotmail.com.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Caprì
authors.affiliation: Dip.to di Scienze Veterinarie, Polo Universitario Annunziata, Messina, Italy. mariagrazia.pennisi@unime.it.
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: Pennisi
authors.affiliation: Laboratorio Veterinario San Marco, Padova, Italy. mc@sanmarcovet.it.
authors.forename: Marco
authors.initials: M
authors.lastname: Caldin
authors.affiliation: Laboratorio Veterinario San Marco, Padova, Italy. tf@sanmarcovet.it.
authors.forename: Tommaso
authors.initials: T
authors.lastname: Furlanello
authors.affiliation: Laboratorio Veterinario San Marco, Padova, Italy. micheletrotta@gmail.com.
authors.forename: Michele
authors.initials: M
authors.lastname: Trotta
mesh_terms: D000818:Animals; D016022:Case-Control Studies; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004283:Dog Diseases / Q000453:epidemiology* / Q000382:microbiology / Q000473:pathology*; D004285:Dogs; D005334:Fever / Q000209:etiology*; D007558:Italy / Q000453:epidemiology; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D012282:Rickettsia Infections / Q000453:epidemiology / Q000382:microbiology / Q000473:pathology / Q000662:veterinary*; D020114:Rickettsia conorii / Q000302:isolation & purification*; D017422:Sequence Analysis, DNA; D016036:Seroepidemiologic Studies; D012698:Serologic Tests
chemical_list: D004269:DNA, Bacterial