The role of clinically healthy dogs in the transmission of vector-borne diseases in Spain: a nationwide study

Background Canine-vector-borne diseases (CVBDs) are a health risk for both dogs and humans. This study sought to determine the role of clinically healthy dogs in transmitting the three main CVBD (Leishmaniosis due to Leishmania infantum , Ehrlichiosis due to Ehrlichia canis and Dirofilariosis due to Dirofilaria immitis ) in Southern Europe. It were reported in all 50 Spanish provinces. Possible associations between seroprevalences and epidemiological variables were also assessed. Methods 11,886 dogs from 609 veterinary clinics were tested using the URANOvet® diagnostic rapid test to detect antibodies against L. infantum and E. canis , and D. immitis antigen. Data were collected regarding sex, age, habitat, clinical signs compatible with each CVBD and the regular use of ectoparasiticides. Results Infection prevalences were L. infantum 17.3% (1915/11,048), D. immitis 3.2% (314/9,938) and E. canis 3.4% (315/9,125). Clinically healthy dogs accounted for 17.6%, 64.7%, and 35.9% of those positive for L. infantum , D. immitis , and E. canis , respectively. Significant differences in the epidemiological variables examined (p < 0.05) were related to positivity for the three pathogens examined including geographic location, habitat, associated clinical signs and use of ectoparasiticides. While a higher seroprevalence of L. infantum and positivity for D. immitis antigen were recorded in older dogs (p < 0.01), male dogs showed a higher seroprevalence of L. infantum (p < 0.01). Conclusions These data indicate that dogs in Spain are at permanent risk of acquiring all of the three CVBD analysed. We recommend that veterinarians should include these main CVBD in their differential diagnoses and, depending on the geographical region, encourage the use of repellents and other prophylactic measures to prevent their transmission by arthropod vectors. These findings highlight the need for early infection detection by routine screening of clinically healthy dogs, as these could be important subclinical carriers.