Haematological parameters in stray dogs seropositive and seronegative to Ehrlichia canis in North Trinidad

In view of the fact that stray dogs are a reservoir for many diseases, this study was undertaken to determine the prevalence of Ehrlichia canis in stray dogs in North Trinidad and to evaluate the diagnostic implications of haematological alterations associated with seropositivity. Overall, 41 (44.6%) of 92 stray dogs were seropositive to E. canis by the indirect immunofluorescent antibody test. Dogs, one year of age and older (59.7%) were more likely to be seropositive than dogs less than one year old (13.3%) (p<0.001). No significant differences in seropositivity between females and males were found. The odds ratios showed that seropositive dogs were 3.34 (CI 95%; 1.33-8.59) and 5.17 (CI 95%; 0.19-1.26) times more likely to have low platelet counts and elevated total serum protein concentrations (p=0.014 and p<0.001, respectively) than seronegative dogs. Lower mean platelet counts and a higher mean total protein concentration were associated with seropositivity (p<0.01). Mean eosinophil and segmented neutrophil counts were elevated in dogs that tested negative for E. canis antibodies (p=0.002 and p<0.005, respectively). Other haematological parameters were not different between the 2 groups. The high percentage of stray dogs infected with E. canis should alert veterinarians to the potential risk of transmission of the disease. A comprehensive study possibly using molecular methods such as nested PCR should be undertaken to determine how co-infection with other pathogens may alter haematological profiles. In general, control of ticks and stray dog populations may help to control the spread of tick-borne diseases.