Infection should be considered in dogs with acute renal or hepatic disease. It has also been proposed that infection may play a role in the development of chronic hepatopathies. Signs are more severe in young animals and include pyrexia, muscle tenderness, vomiting, dehydration, vascular collapse, increased thirst and coagulation defects. Icterus and renal failure are commonly noted but some animals may die per acutely, prior to development of typical clinicopathological changes.
- Clinical pathology: azotaemia is most common. Leucocytosis and thrombocytopenia may also be noted. Raised ALT, ALP and bilirubin are noted with hepatic involvement.
- Serological testing. A presumptive diagnosis may be made on the basis of a single high titre, with appropriate clinical signs, in a dog which has not been vaccinated recently. However, the titres may be negative in the first 7-10 days and further testing in 2-3 weeks is required to demonstrate a rising titre. Two serological tests are available. The Leptospira antibody screen (immunofluorescent antibody test; Leptospira antibody screen detects antibodies against a genus-specific antigen and is expected to detect antibodies against pathogenic serovars likely to cause clinical disease in the UK. However, it does not allow confirmation of the infecting serovar. A microscopic agglutination test is also available in which the patient sample is tested against serovar pools. If a positive result is obtained, then the sample is tested against individual serovars (at an additional cost). Dogs with positive titres often have sera which cross reacts with a variety of serovars and historically the highest titre may be presumed to indicate the infecting serovar. However, this assumption has been questioned since it was found that the highest titre may vary between laboratories, over time, in the same patient.
- PCR on urine. Organism shedding is typically noted from day 7-14 after infection, prior to development of an antibody titre. A positive result confirms infection and urinary shedding.
Vaccination usually only produces a very short-lived humoral response and prevaccination screens are not advised. Serology should be reserved for suspected clinical cases. Annual booster vaccination is recommended for dogs with a reasonable risk of exposure.
For more information about canine infectious diseases visit our website https://nwlabs.co.uk/lab-facts
