Leptospirosis: Part 2
Yesterday, we talked about how dogs contract leptospirosis, how vaccination may or may not help prevent it, and what the bacteria do to a dog’s body. Today, let’s touch upon how the disease is diagnosed and treated and how we can prevent dogs from being a source of infection for people.
The microscopic agglutination test (MAT) is the most commonly used test for leptospirosis, but it is not perfect. In general, a definitive diagnosis requires that two blood samples drawn and tested 2-4 weeks apart demonstrate a four-fold increase in antibody levels. Obviously, treatment has to begin before the final results are in. Previous vaccination and initiating treatment in between the tests can make interpreting the results difficult. A high titer on the initial blood sample to a serovar that a dog has not been vaccinated against is suggestive of lepto but still not foolproof. An initial negative result can be seen with very early infections and so does not completely eliminate the possibility of lepto infection either.
Other tests are available (e.g., ELISA and PCR tests and dark field microscopy), but they also have their limitations. In reality, what oftentimes occurs is that a veterinarian suspects lepto, treats the dog accordingly, and the diagnosis is confirmed with the second blood test after the patient is well on his way to recovery … hopefully.
This delay in diagnosis is more than just an annoyance. People and other animals can contract leptospirosis through contact with an infected dog’s urine (cats seem to be pretty resistant to the disease, however). So while the dog is hospitalized for treatment and even after he goes home, biosecurity is essential. Strict quarantine is implemented during the initial stages of therapy. Veterinary personnel should wear gowns, foot covers, gloves, eye shields, and masks when handling or cleaning up after lepto suspects.
Most mildly to moderately affected dogs will recover from leptospirosis when treated with appropriate antibiotics (usually doxycycline or penicillin followed by doxycycline), intravenous fluid therapy, and symptomatic care (e.g., anti-nausea medications if a dog is vomiting). More severe cases may require medications to stimulate urine production, dialysis, and blood or plasma transfusions to keep the patient alive while giving affected organs a chance to recover. Prognosis in these cases is obviously not as good.
Dogs that have been infected with Leptospira interrogans can shed the organism in their urine for a long time and pose a risk to both people and animals. A two week course of the antibiotic doxycycline helps to clear the bacteria out of the kidneys. Most dogs return home while they are still undergoing this treatment, so owners should take them to urinate in areas where other pets do not have access, wear gloves and wash hands thoroughly when they have potentially had contact with their dog’s urine, and clean up any “accidents” that occur using either bleach or iodine-based disinfectants.
For more information about leptospirosis as it applies to both people and pets, check out the Center for Disease Control’s excellent webpage concerning this important disease.
Dr. Jennifer Coates