Leptospirosis is a serious disease that affects dogs, cats, horses, swine, sheep, goats, deer, marine mammals and humans. The disease starts when leptospires, the immature form of the bacteria, enter the body and make their way into the bloodstream. They stick to the endothelial cells within the blood vessels causing severe vasculitis (inflammation). As the organism replicates it causes more and more damage to the blood vessels. Eventually, the blood vessel walls begin to hemorrhage. The liver and kidneys are the two organs that are affected most often, but the bacteria can also attack the spleen, eyes, nervous system and reproductive organs. Once an animal is infected, they may shed the organism for years and thus infect others.
There are two species of Leptospira that are further divided into over 250 smaller groups called serovars. The most common serovars and the animals that are asymptomatic hosts in the United States are: grippotyphosa carried by raccoons, bratislava carried by rats and horses, autumnalis carried by mice and pomona carried by cows and pigs. Dogs infected with canicola, bratislava and grippotyphosa usually have severe kidney disease with mild liver disease. Dogs with icterohaemorrhagiae and pomona have more liver disease. Pomona is associated with the most severe kidney disease and has the worst prognosis.
Leptospira bacteria like to live in warm moist environments with alkaline soil. Under these conditions, the bacteria can survive for months. Infections occur through direct exposure to the urine, saliva (bite wounds) or tissues of animals infected with the disease. It can also be contracted indirectly by contact with water, soil, food or bedding that is contaminated with the organism. The leptospires can penetrate mucous membranes and damaged skin. In the February 2016, nine dogs tested positive for this disease in Scottsdale, Arizona. It is thought that heavy storms left standing water that was contaminated by pack rats. Unfortunately, two died.
Signs of leptospirosis vary greatly from mild malaise to death. The incubation period is usually 7 days. The most common signs in dogs in the early phase are fever, shivering, lethargy, decreased appetite and muscle tenderness. As the disease progresses, increased thirst and urination, abdominal pain, vomiting, eye disease, diarrhea, joint stiffness, bruising of the skin, coughing and a runny nose are just a few of the symptoms that can occur. The exact symptoms depend upon which organ is affected. Animals with liver involvement become jaundiced (yellow color of the skin). If the nervous system is involved, animals may seizure, have problems walking or suffer neurologic deficits.
Diagnosis of leptospirosis requires special testing to identify the organism. Routine blood work, urinalysis and clotting tests will make it a rule-out but not make the diagnosis. 87-100% of dogs present with elevated creatinine and BUN. The specific tests for this bacteria are listed as follows: 1) Microscopic Agglutination Test – This is the most common test in veterinary medicine. Blood is collected for measurement of the titer. Since this test is a measurement of the antibodies generated against the bacteria, it will be negative early in the disease. It usually takes about 7-10 days for antibodies to be found. 2) ELISA Testing – This test is another antibody test that is sometimes used to distinguish vaccination titers from naturally occurring infections. 3) Polymerase Chain Reaction Assays – This test identifies the nucleic acid of leptospires which means it does not require production of antibodies. Early in the disease, the test is performed on blood. After 10 days, urine is used instead because higher numbers of the leptospires are found there. Unfortunately, the test may give a false negative result if the patient is receiving antibiotics. This is the test used to detect dogs who are carriers of leptospirosis. 4) Culture – Growing this bacteria is difficult because it requires specific conditions and grows slowly.
Antibiotics are used to treat leptospirosis. Due to the severity of this disease, treatment with doxycycline is started while waiting for test results. Most dogs will also require hospitalization with fluid therapy and careful monitoring of their kidney function. Since leptospirosis is a zoonotic disease, the dog must be kept in strict isolation. Caregivers should take precautions to prevent contracting or spreading the disease including waterproof gowns, gloves and face shields. All waste must be carefully collected and disposed of properly.
Prevention is the key to dealing with leptospirosis. Thankfully, there are two vaccines available for dogs in the United Sates. One is a bivalent which means it only contains two serovars, icterohaemorrhagiae and canicola. I recommend the other vaccine which contains 4 serovars – canicola, icterohaemorrhagiae, grippotyphosa and pomona. This vaccine is licensed for pups 6 weeks and older. The manufacturer recommends 2 doses of the vaccine given 2-3 weeks apart and then boosted annually.
Sources:
-Adams, Laura. Canine Leptospirosis in Arizona, Arizona Veterinary News, Arizona Veterinary Medical Association, March 2016.
-Morgan, Rhea. Leptospirosis (Zoonotic), Associate Database, Veterinary Information Network, 1/29/2014, Last updated by Kari Rothrock 1/20/2012.