From the point of view of the human
disease, dogs are the most important animal reservoir of
Lyme borreliosis; therefore, they are used as ‘sentinel animals’. In order to know the epidemiological characteristics of dogs with antibodies against Borrelia burgdorferi, 146 canine sera samples collected during 1993-94 have been studied. The antibody detection was made by an indirect immunofluorescence method and confirmed by a haemagglutination test. Seventeen dogs (11.6%) were seropositive, of which seven were hunting dogs, three were shepherd dogs, five were domestic pets, one was a watchdog and one was a stray dog. Seven dogs had longhair phenotype, 2 medium length type, 4 hard-hair and the other 4 were short-haired. Twelve seropositive dogs were males and five were females. All seropositive dogs were more than 1 year old. The dogs with greater seroprevalence were those that harboured ticks more often than the rest. Spring and summer were the seasons when more ticks were observed. The seroprevalence found in dogs was similar to that previously obtained in humans in this area. This finding gave evidence to an intimate association between human and canine seroprevalence.