Leptospirosis is a bacterial infection caused by Leptospira. Leptospira exists worldwide. There are numerous Leptospira bacteria; 230 have been identified thus far.
Wild animals can spread leptospirosis to dogs. Leptospira can remain in the environment for long periods of time, especially in warm, stagnant water or in moist soil. The bacteria do not tolerate freezing temperatures, so the risk of a dog getting leptospirosis decreases during the winter months. Most cases are seen during the summer and fall when temperatures are warmer.
Dogs usually become infected with leptospirosis through direct contact with the urine of infected animals, such as raccoons, rats, skunks, feral cats, other dogs, and other animals. It's also possible for dogs to become infected with the bacteria by swimming in or drinking contaminated water. Dogs who have contact with contaminated soil can also become infected. The bacteria can penetrate the soft lining of a dog's nose, eyelids, and mouth or enter the body through scratches or open sores on a dog's skin.
After Leptospira have entered a dog's body, the bacteria multiply in the bloodstream and move into the body's tissues. The bacteria mainly settle in the liver and kidneys. Once there, the bacteria damages to these organs.
Approximately eight to 10 days after infection, a dog's body produces an antibody that quickly clears much of the bacteria out of the dog's system.
Most dogs recover from leptospirosis well, though the time it takes for them to recover varies. However, in many dogs, even those who appear to have recovered fully, small amounts of Leptospira bacteria remain in the dog's body. Dogs can pass the bacteria to other animals through their urine. A dog becomes a carrier when he recovers from leptospirosis but still carries the bacteria in his body.
Many dogs with mild leptospirosis infections don't show any symptoms.
Dogs who have severe leptospirosis infections may experience vomiting, diarrhea, depression, lack of appetite, lethargy, muscle pain, increased thirst and urination, and fever. Jaundice may also occur. Jaundice is an indication of liver inflammation and shows up as yellowing of the lining of the mouth and whites of the eyes.
Blood clotting issues may occur, which can result in bleeding from a dog's mouth tissues or blood in the stool. Death can occur in severe cases of leptospirosis.
In rare cases, acute pulmonary hemorrhage and respiratory distress can happen.
When symptoms occur, they usually show up between four and 12 days after infection with the bacteria. Young dogs tend to get sicker than older dogs do.
While leptospirosis cannot be definitively diagnosed with routine blood work, a veterinarian will begin with this in order to determine what might be going on with a dog. Clues from routine blood work may lead a vet to recommend definitive tests for leptospirosis.
Complete Blood Count CBC): A CBC may show an increase in white blood cells and a decrease in platelets, both indicative of an infection. A dog with leptospirosis may also have decreased red blood cells due to bleeding.
Serum Biochemistry: Damage to the liver and kidneys may show up as high liver or kidney values. This test may also show abnormal potassium, chloride, sodium, and phosphorus levels in dogs with leptospirosis.
Urinalysis: A urinalysis can show kidney damage.
Several tests can definitively diagnose leptospirosis in dogs, but the two most commonly used ones are the DNA-PCR test and the microscopic agglutination test (MAT).
The DNA-PCR test is often faster and cheaper than the MAT. Every living thing has DNA, including bacteria, viruses, and protozoa. The DNA-PCR test detects the DNA of Leptospira bacteria in urine or blood. There are often a large number of bacteria in urine, so it's typically the preferred sample.
The DNA-PCR test has limits. It must be administered before a dog is given antibiotics because the test may not be able to detect the small number of bacteria following antibiotic treatment. Dogs with mild disease may not test positive for leptospirosis due to the small number of bacteria present in the system.
The MAT identifies antibodies against Leptospira in a dog's body. If the antibody level is high enough, leptospirosis is diagnosed.
The MAT also has limitations. It is slower than the DNA-PCR test. It may take several days before results are back from the laboratory. If the dog was given antibiotics early in the course of the disease before her body had time to start producing antibodies or if the dog was vaccinated against leptospirosis, the MAT may produce an inconclusive result.
Dogs who do not show any symptoms of leptospirosis generally recover without treatment. However, these dogs are in danger of becoming carriers of the disease and may pass it to other animals through their urine for up to a year.
Many dogs with leptospirosis recover well with antibiotic treatment. Dogs with severe illness may need to be hospitalized. Dogs who are hospitalized will receive antibiotic treatment, fluid therapy, nutrition, and treatment to manage diarrhea and vomiting if needed.
Owners should keep their dogs from swimming in or drinking water from ponds, streams, and puddles. Owners should also safely control the rodent population both in and around their homes.
There is a vaccine for leptospirosis. The vaccine is short-acting and cannot protect against all the types of Leptospira bacteria. Owners who are interested in the vaccine should talk to their veterinarians about it.
Leptospirosis is a zoonotic disease, one that can be spread from animals to people. Dog owners should be cautious when caring for an infected dog. Face masks, gloves, and regular, thorough hand-washing will help prevent infected urine from getting into the mouth, nose, eyes, or broken skin. Disinfection of contaminated areas and objects is also important.
Someone who feels sick after being exposed to leptospirosis should seek medical attention from their physician.
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