Leptospirosis is a disease of worldwide significance that infects both animals and humans. The scientific name of the infecting organism is Leptospira interrogans sensu lato. While cats can be infected, they rarely show signs of disease. The disease is much more of a problem in dogs, people, and livestock.
Transmission
Leptospirosis is transmitted between animals through contact with infected urine; veneral and placental transfer; bite wounds; or the ingestion of infected tissue. Indirect transmission occurs through exposure of susceptible animals to contaminated water sources, food, or even bedding. Stagnant water provides a suitable habitat for Leptospira. As a result, disease outbreaks often increase during periods of flooding. In dry areas infections are more common around water sources.
Freezing greatly reduces the survival of the organism in the environment. This explains why infections are more common in summer and fall and why the infection is more prevalent in temperate areas.
Infection
Leptospira bacteria penetrate mucous membranes or abraded skin and multiply rapidly upon entering the blood system. From there they spread to other tissues including the kidneys,liver, spleen, nervous system, eyes, and genital tract. As the body fights the infection, the organism is cleared from most organs, but they may remain in the kidneys and be shed for weeks or months in the urine.
Symptoms
In acute infections a fever of 103-104°, shivering, and muscle tenderness are the first signs. Then vomiting and rapid dehydration may develop. Severely infected dogs may develop hypothermia and become depressed and die before kidney or liver failure has a chance to develop.
In subacute infections, the animal usually develops a fever, anorexia, vomiting, dehydration, and increased thirst. The dog may be reluctant to move due to muscle or kidney pain. Animals with liver involvement may develop a yellowing of the skin. Dogs that develop kidney or liver involvement may begin to show improvement in organ function after 2 to 3 weeks or they may develop kidney failure. Despite the possibility of severe infection and death, the majority of leptospiral infections in dogs are chronic or subclinical. Dogs that become chronically infected may show no outward signs, but may intermittently shed bacteria in the urine for months or years.
Diagnosis
A positive diagnosis can be made through a blood test. Acutely infected or chronically infected dogs will most likely be shedding Leptospira organisms in their urine. It is possible toculture a urine sample and get a positive diagnosis. However, because of intermittent shedding and bacterial contamination this is not always the best way to diagnose the disease.
Treatment
Treatment consists of antibiotics, fluid replacement, and controlling the vomiting and the problems associated with the corresponding kidney or liver infections. Penicillin, or one of its derivatives is the antibiotic of choice for treating the initial infection. IV fluids are given to rehydrate the animal and help with the damage done to the kidneys.
Vaccination and Prevention
Prevention involves keeping pets out of contact with contaminated water sources, or wildlife reservoirs. Humans can contract leptospirosis and any potentially infected animal should be handled very carefully to avoid human exposure.
There are currently many different vaccines available on the market. The ones currently available for dogs are chemically inactivated (killed) whole culture vaccine, which unfortunately, make them much more likely to cause vaccine reactions as opposed to most viral vaccines.
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