Leptospirosis is a bacterial disease that is transmissible from animals to human beings (zoonotic) and is found worldwide. The causative agent is generically known as leptospires, and are found in a number of wild and domestic animal reservoir hosts. Leptospires are classified as spirochetes and are carried and shed in the urine of healthy reservoir hosts. Animals that recover from leptospirosis often continue to excrete leptospires for months if not years.
Leptospires do not survive well outside the body except under ideal temperature and humidity. They frequently contaminate water supplies where livestock and wild rodents congregate. Animals most often acquire the infection from direct contact with an infected host or by ingesting organisms in urine contaminated water.
There are seven major leptospires causing leptospirosis in dogs and each comes from a different host. Leptospira canicola is the most common cause of leptospirosis in dogs which also serve as the primary reservoir host. Leptospira icterohaemorrhagiae is a less frequent cause of leptospirosis in dogs and rats are the primary reservoir host. Leptospria pomona is carried by large animal species, especially livestock, and causes leptospirosis mostly in farm dogs and often in warm, rainy weather when pastures are dotted with pools of freestanding water contaminated with cattle urine. More infrequently, Leptospira grippotyphosa which is carried by voles and other small rodents, and Leptospira bataviae which is carried by rats, mice, and other dogs, have been reported to cause leptospirosis in dogs.
The most common manifestation of leptospirosis in dogs is kidney disease. Male dogs seem to be affected more than females. The majority of leptospira infections of dogs produce either no symptoms or symptoms so mild that they pass unnoticed. Dogs may exhibit signs of mild to moderate malaise and depression, low grade fever, vomiting, and reddening of the mucous membranes and whites of the eyes. Blood analysis often reveals elevation of white blood cells and elevated levels of blood urea nitrogen.
Each leptospire can manifest a different set of clinical symptoms. Leptospira canicola most often produces acute kidney inflammation (nephritis) without lasting kidney damage. Leptospira icterohaemorrhagiae manifests serious, generalized, bleeding (hemorrhagic) illness. In cases of more generalized disease, leptospirosis can cause pneumonia, liver inflammation accompanied by jaundice, or intestinal inflammation.
Complications from leptospirosis can involve chronic, progressive kidney disease which may follow one or more mild attacks of primary nephritis.
Treatment involves supportive care and administration of antibiotics. Supportive care involve replenishment of fluid and electrolyte loss in the presence of vomiting and diarrhea; transfusions in the presence of skin hemorrhages or other indications of blood loss or clotting abnormalities; administration of drugs that promote urination (diuretics) in the presence of early stages of kidney failure. Antibiotic therapy may be continued for several weeks in order to eliminate the leptospires.
Prevention involves vaccinations and avoidance of areas known to be contaminated with leptospires. Vaccines consist of inactivated bacteria containing the leptospires Leptospira canicola and Leptospira icterohaemorrhagiae. It should be noted that vaccines do not prevent infection, but rather are effective in reducing the occurrence and severity of disease. Further, duration of protection following vaccination is relatively short, usually no more than 6 months. The immunity imparted is specific to the individual leptospires contained in the vaccine.
Owners of dogs known or suspected to be infected with leptospires should realize that the disease does cause a public health hazard since human beings are susceptible. Human infections of leptospira can be severe and persist for lengthy periods of time. Owners of such dogs must be cautious and observe strict hygienic measures while caring for any pet suffering from leptospirosis.