Leptospirosis is a zoonotic disease that can pass from animals to humans. It is a bacterial disease that damages the liver and kidneys of dogs, sometimes resulting in renal failure and death. It is caused by a spirochete (spiral shaped bacterium) called a leptospire.

Leptospires live in fluids from infected animals, including urine, saliva, blood and milk. The disease is transmitted by direct contact with the fluids or with an infected animal. It is also transmitted by indirect contact such as vegetation, food and water, soil and bedding materials. Leptospires enter the body through mucous membranes or through breaks in the skin. The disease may be carried for years in animals without any apparent symptoms of the disease.

Any age, breed or sex of dog is susceptible to leptospirosis, although in general, young animals are more severely affected than adults. Large breed outdoor adult dogs are most commonly affected. Leptospirosis can cause irreversible kidney damage, liver damage, uveitis (inflammation of the inner part of the eye), and damage to other organs.

WHAT TO WATCH FOR

The first signs you might notice in your pet are flu-like symptoms. This may include several days of anorexia, vomiting, lethargy, depression and sometimes diarrhea or bloody urine. Other signs may include:

Chills and fever
Generalized muscle tenderness
Dehydration
Blood in the vomit or stool, bloody nose or widespread bruising
Jaundice
Labored breathing or coughing
Sudden lack of production of urine

Your veterinarian will want to do a complete review of history and physical exam findings to develop a list of possible causes for your dog's illness. In order to make a definitive diagnosis of leptospirosis, however, various diagnostic tests may be recommended.

Leptospirosis test. A microscopic agglutination test (MAT) is the most frequently used serologic test for leptospirosis. It evaluates the presence of serum antibodies to leptospiral antigens.

General blood and urine tests

Kidney biopsy

If the disease is caught in time, it can usually be treated successfully with penicillin and tetracycline drugs. However, those with renal failure may or may not recover, or may recover only partial renal function.

Animals with acute renal failure should be treated with appropriate fluid therapy.

Antibiotic therapy

Supportive care including hospitalization with intravenous fluids or blood transfusion.

Prevention is available in the form of vaccinations, although they provide protection against serovars (subtypes) canicola and icterohaemorrhagiae. Despite this, immunization is recommended. New vaccines may provide a broader spectrum of protection.

Rodents are a potential source of infection for dogs, and rodent control, especially in kennels, is an important prevention method.

Minimize contact with wild animals because these animals are reservoirs of infection.

Isolate infected animals and maintain a clean environment.

INFORMATION IN-DEPTH

Leptospirosis is still an important infectious disease of dogs, despite the fact that vaccines have been around for more than 30 years. It has a worldwide distribution and is caused by several distinct serovars (subtypes) of the organism Leptospira interrogans. The organism is a spiral shaped bacterium with hook shaped ends that makes a characteristic writhing and flexing movement while moving. There are many distinct subtypes of the leptospirosis organism, although five in particular are responsible for most cases of disease in dogs. Dogs contract leptospirosis either by direct contact with infected urine, bite wounds, eating infected tissue or during birth.

Wild animals like skunks, raccoons and opossums are a major source of infection, although pigs, rats and other animals may harbor the organism and serve as reservoirs of infection. Direct spread is enhanced by crowding of animals, such as in kennel situations. Indirect transmission can occur if susceptible animals are exposed to contaminated food, soil, water or bedding. Stagnant or slow-moving warm water provides an excellent habitat for the organism. This explains the increase in cases during periods of flooding.

Once the organism penetrates the body, it enters the bloodstream and multiplies rapidly and causes the blood vessels to become inflamed. The organism penetrates through the inflamed vessels and invades other organs like the kidneys, liver, spleen, eyes and reproductive tract. The body makes an immune response and eliminates the organism from most organs. Unfortunately, organisms tend to persist in the kidneys and can be released into the urine for several weeks or months. When the organism invades the kidney, sudden impairment of kidney function may result. Depending on how virulent, or infectious, the particular serovar of the organism is, and how strong an immune response the dog mounts, the damage can be mild or severe. Some serovars can cause sudden hemorrhage, liver damage, and most commonly, kidney damage.

Leptospirosis is a zoonotic disease and can be transmitted to humans. The Centers for Disease Control has reported an average of 50 to 100 cases per year for the past 20 years and a few cases come from contact with rats or dogs. The majority of human infections are among those who engage in water sport activities or who experience occupational exposure to wildlife or domestic animal hosts. It has a very low fatality rate in humans.

Diseases causing similar symptoms in dogs include the following:

OTHER CAUSES OF KIDNEY FAILURE
Acute kidney failure
Chronic kidney failure
Antifreeze poisoning
OTHER CAUSES OF LIVER FAILURE
Infectious hepatitis
Chronic active hepatitis
Liver cancer

VETERINARY CARE IN-DEPTH

DIAGNOSIS

Diagnostic tests are needed to verify the diagnosis of leptospirosis and exclude other causes of similar signs and optimally evaluate your pet for this disorder. Tests may include the following:

General blood and urine tests. Routine tests, such as a complete blood count, biochemistry panel and urinalysis will reveal the presence and severity of kidney damage and liver damage.

The microscopic agglutination test (MAT). The MAT is a blood test that looks for antibodies against the leptospirosis organism. A single high measurement may be diagnostic, although a more definite diagnosis is made if the antibody level increases fourfold, two to four weeks later.

Kidney biopsy. A silver stain looks for the leptospirosis organism, although this test often gives falsely negative results and may miss the diagnosis.

Therapy for leptospirosis may include one or more of the following:

Antibiotic therapy is performed in two phases. Phase I is for killing the leptospirosis organisms in the bloodstream. Penicillin is the best antibiotic for this. Phase II is for killing the organism in the kidney to prevent the carrier state. (Doxycycline is thought to be the most effective.

Supportive care is directed at the other affected organ systems. Most pets are dehydrated from vomiting and diarrhea and require intravenous fluid therapy. Animals in acute kidney failure may need a diuretic, like furosemide (Lasix) or mannitol, to help restore urine production. If urine flow cannot be restored, dialysis should be considered. This requires referral to a specialty practice or university. Dialysis is expensive, but the acute kidney failure due to leptospirosis is usually reversible. Blood transfusions may be needed if bleeding disorders develop or persist and are causing active bleeding.

Optimal treatment for your pet requires a combination of home and professional veterinary care. Follow-up care can be critical, especially if your pet does not rapidly improve. Administer all prescribed medication as directed. Alert your veterinarian if you are experiencing problems treating your pet.

If your dog has permanent kidney damage as a result of the leptospirosis, you may need to feed him a special low-protein diet. Monitor your dog’s food intake, water intake and body weight.

Blood and urine tests will need to be repeated and monitored frequently to assess the final extent of any kidney damage.

Consider vaccination for any other dogs in the household. There is a new vaccine (Duramune DA2P+Pv/LCI-GP) that immunizes dogs against four serovars of the leptospirosis organism. Previous vaccines only immunized against two serovars.