Leptospirosis is a disease caused by a spiral-shaped bacteria called Leptospira interrogans. This bacteria has a multitude of serovars (or breeds). It infects a variety of tissues in the body primarily the liver and kidneys but also eyes, lungs, and brain. The severity of the disease ranges considerably with the infecting serovar, the immune status of the host, and the concurrent health problems of the host. Treatment if initiated early in the disease is often successful but many times affected dogs remain subclinically infected for a long time afterwards. These dogs act as carriers and serve as a source for spread of the organism to other animals.
Leptospira infects a number of animal including humans. Deer, cattle, and rodents serve as the main reservoirs of the organism in the environment. Urine is the primary means of transmission. Infected urine contaminates bodies of water in particular shallow, stagnant bodies of water. Dogs coming into contact with the contaminated water become infected through ingestion, inhalation, or absorption across mucous membranes like the gums. Summer and early fall are the times of highest incidence. Young, large breed dogs that like the water are the most at-risk group for exposure. Other possible routes of transmission include bite wounds, venereal contact, and ingestion of contaminated food.
Clinical signs develop in approximately one week after exposure. Most common initial signs are fever, depression, loss of appetite, vomiting, and loss of energy. The disease progresses to acute renal failure (increased thirst increased urination, and significant electrolyte imbalances) and/or acute liver disease (improper clotting and jaundice). Less common clinical signs include incoordination, disorientation, difficulty breathing, coughing, inflammation of the eyes, and hemorrhage. Untreated most dogs will die within 3-7 days from complete renal failure.
Treatment consists of antibiotic therapy to kill the organism, fluid and electrolyte therapy to restore normal hydration and correct electrolyte imbalances, and measures to address other signs such as blood transfusions if hemorrhaging. Prognosis varies greatly with infecting serovar, the immune competence of the host, and the stage of the disease at presentation. It is impossible to predict response to therapy. Some dogs with severe disease at presentation respond well to therapy and survive; others with mild disease at presentation fail to respond to therapy and eventually die. Even if treatment is successful, often residual damage in the form of chronic hepatitis or chronic renal disease remains.
Vaccines are available for some of the serovars but not all of them. Unfortunately, there is little if any cross-protection between serovars. Thus, even a fully vaccinated dog can become infection with Leptospira organisms. In endemic areas, initial vaccination should be 3 doses given 2-3 weeks apart and boosters given every 6 months to 1 year thereafter. Preventing access to shallow, stagnant water is also recommended especially in areas with large populations of rodents or deer. Discuss with your veterinarian the risk of Leptospira exposure in your area.
All the serovars that infect animal can potentially infect humans. Owners, veterinarians, and veterinary staff need to exercise appropriate caution, hygiene, and sanitation to reduce risk of infection.
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