by Barry B. Burtis D.V.M.
In my last column we began a discussion about a bacterial disease called leptospirosis. There are many different types or species of the Leptospira family of bacteria, the causative organism. The different types have adapted to different preferred animal hosts. Cattle, various rodents, skunks, raccoons, opossums, pigs, dogs and other canines all can act as reservoir species for the bacteria. In these host-adapted animals, disease tends to be milder but excretion of the bacteria into the environment still occurs. The leptospire bacteria can live outside the host for several months if the conditions are damp, protected from sunlight and cool. This means spring and fall are the seasons of most danger for infection. For dogs kept as pets in this part of the world or in countries where the disease is more common in people, it is usually contact with these bacteria in the environment that leads to infection. The tiny corkscrew shaped bacteria can penetrate a dog's intact or cut skin or mucus membranes, usually of the mouth, nose or throat.
For this reason, it historically was felt that hunting dogs and dogs living in rural areas had a greater risk of infection. They were more likely to drink or swim in water that had become infected with the bacteria. Stagnant pools of water in pasturelands, streams and swampy areas are places that were thought to be places with increased risk of exposure. However, with recent increased numbers of cases of leptospirosis being seen in urban dogs, risk factors may not be as they once were. Increasing numbers of wildlife species within our cities, dogs traveling as they now do and the increasing popularity of leash free environments for dogs, all may be responsible for leptospirosis posing more danger to all dogs.
Within 4-7 days of entering the dog's body, the bloodstream is rapidly invaded and within another 2-4 days the bacteria spreads to all parts of the body. The symptoms produced from this invasion can be mild or severe. Fever, sore muscles, weakness, depression, changes in breathing, loss of appetite, diarrhea and sometimes jaundice can all be seen with leptospirosis. Occasionally, sudden death with no preceding clinical signs can occur. The severity of the disease will depend on which species of the bacteria is causing the infection and the patient affected. Inflammation of the internal parts of the eye, called uveitis, is another body system that can be affected with leptospirosis. That was what happened with Bonna. Remember Bonna, she is the 8 year old husky written about at the start of this tale.
Two days after Bonna's first visit, when blood tests and physical examinations were unable to provide a definitive diagnosis, changes were detected in both eyes and a veterinary eye specialist was consulted. A course of antibiotics was begun. Those same blood tests, done just a few days earlier, were repeated. Now, instead of being completely normal, as they had been, they showed serious and significant changes in the health of both her kidneys and liver. These organ systems are the ones most commonly affected in this disease. Failure of these vital organs can be life threatening.
Confirmation of a diagnosis of leptospirosis relies on tests that detect antibodies against the bacteria in the blood. These tests can be difficult to interpret and sometimes are unavailable until the most serious stage of the disease is past. Animals with leptospirosis will usually require intensive supportive care and appropriate antimicrobial therapy. Often a combination of amoxicillin or ampicillin and doxycycline is used to eliminate the bacteria from both the blood and organs of an affected animal.
Humans can be affected with leptospire bacteria and the route of infection is by direct or indirect exposure to urine from an infected dog, raccoon or skunk. Humans have also been exposed by swimming in water contaminated with leptospires from wildlife. Therefore, caution must be exercised by both veterinary hospital personnel and owners who are caring for a sick or recovering leptospirosis patient.
Vaccination recommendations regarding this disease vary amongst veterinarians. Risk factors for individual dogs need to be considered. Traditionally, with leptospirosis vaccines, there have been concerns about the lack of a vaccine against all species of leptospire bacteria, about the duration of immunity from vaccines and about hypersensitivity reactions following vaccination. Current vaccines available are addressing many of these issues. Dog owners should discuss with their veterinarian whether leptospirosis vaccinations should be considered for their pet. Cats do not develop clinical signs with leptospirosis and therefore, although leptospires have been isolated from cats, it does not appear to be a problem for them.
Happily Bonna recovered successfully from her illness and she greatly enjoyed walks and romps in the snow, this year, just as she has in winters past.