Identification of Leptospire Urinary Shedders Among Roaming Dogs by Polymerase Chain Reaction (PCR)
Dogs may harbor pathogenic leptospires as serovar Canicola without overt clinical signs of infection. In serologic surveys of clinically healthy dogs, the wide prevalence of seroreactivity among serogroups suggests that subclinical infections and exposures to non-pathogenic serovars occur. Once infected, dogs may become urinary shedders and they might theoretically be thought as an environmental risk of infection.
To identify leptospire urinary shedders among free-roaming dogs.
Seven dogs were captured and serum and urine samples were obtained. Serum MAT was done for evaluation of anti-leptospiral antibodies against serovars belonging to 19 serogroups of pathogenic leptospires. Urine samples were submitted to conventional PCR according to Merien (1992). Attempts to isolate leptospires were made whenever PCR yielded positive results.
Antibodies against serovar grippotyphosa (4/7), pomona (2/7), butembo (3/7), castellonis (1/7), Copenhageni (2/7), Icterohaemorrhagiae (2/7), Hardjo (1/7), e Wolffi (1/7) were found in low titers (< 400). All dogs but one were previously vaccinated with bivalent vaccine (Icterohaemorrhagiae and Canicola). Positive PCR results, with amplification of a band (331 pb) was yielded from two dogs, one vaccinated and one unvaccinated dog. Urinary shedding was confirmed three times more, within a period of three months in one dog. Antimicrobial treatment (doxycycline) of the dog resulted apparently in the clearance of infection. Attempts to cultivate the organism were frustrating. Sequencing of amplicons revealed homology to sequences of Icterohaemorrhagiae at the Gene Bank.
Urine PCR is a useful tool for identification of subclinically infected dogs, aiming to prevent urinary shedding of leptospires.