Serum antibody titres for leptospira and its association to the immunization and rearing pattern in a sample of dogs from suburbs of Colombo: a preliminary study

Leptospirosis is an important zoonotic disease in man and animals. Increasing numbers of human Leptospirosis are reported each year in Sri Lanka. Rodents are most often the natural maintenance host of leptospira, but the potential of transmitting the disease from ruminants and dogs to human should not be overlooked. Aim of this study was to determine the serum antibody titres for leptospira in 139 dogs in selected suburbs of Colombo, Sri Lanka and evaluate its association with dog rearing pattern and immunization history. A questionnaire based survey was conducted to collect data on dog rearing pattern and vaccination history of dogs. In addition, the potential transmission of leptospira from dog to human and public awareness on canine leptospirosis was also assessed. Blood samples obtained from dogs were subjected to Microscopic Agglutination Test (MAT) to detect leptospira antibody levels and to identify respective strains. Strains were identified against 12 serovars of pathogenic genomospecies Leptospira interrogans. According to MAT results, around 62% of unvaccinated domestic dogs enrolled in the study had leptospira antibody titres ranging from 1:100 - 1:3200, indicating an acute or convalescent stage of infection. Moreover, 25% of primarily vaccinated dogs, 17.9% of regularly vaccinated dogs and 36.8% of randomly vaccinated dogs failed to seroconvert. Serum samples subjected to sero grouping were all found to be within pathogenic genomic species Leptospira interrogans. Single sero groups L. canicola, L. australis, L. Icterohaemorragica and L. djsiman and mixed sero-groups L. australis and L. canicola were predominantly observed. No clinically proven Leptospirosis was reported among the owners of the dogs, their family members or other household pets even if they had close contact with their dogs. Among the surveyed population, only one person was aware of (0.7%) possible transmission of leptospirosis from dogs. Statistically significant number of primarily vaccinated dogs was in indoor habitats and randomly vaccinated dogs were in outdoor habitats (p< 0.05). That trend was not observed in regularly vaccinated and unvaccinated dog population (p> 0.05). Leptospirosis being a highly infectious zoonotic disease, outdoor living unvaccinated and randomly vaccinated domestic canine populations may contribute to increasing incidence of Leptospirosis in man as well as in other domestic mammals.