What is Leptospirosis?

Introduction

If you decide to have leptospirosis vaccine administered to your pet, have it given as an independent injection, and not in a combination vaccine or multiple vaccines given on the same day. First get your dog immunized against parvo and distemper virus. Then let several weeks pass before the leptospirosis vaccination. This is because adding leptospirosis ingredients to combination vaccines can reduce the protection effectiveness of the other ingredients. You can read about how that occurs here. It is also apparent from the results of that study that the current recommendation that "one lepto vaccine dose size fits all sizes of dogs" needs to be rethought out.

What Causes Leptospirosis?

Leptospirosis is a disease that affects many kinds of animals besides dogs. It occurs throughout the World.

The organism that causes leptospirosis belongs in a group of spiral organisms called spirochetes. They are similar to ordinary bacteria in many ways. However, they move and wriggle about in a spinning motion using their wavy membrane called a flagella. There are many spirochetes in nature, most living free in the environment and doing no harm. But two spirochetes have adapted to cause disease in your pet. They are the Leptospira responsible for leptosporosis and the Borreia that cause Lyme disease.

There are a very large number of leptospira. Currently, about 230 of them have been identified. They are divided into strains (or serovars), based on the characteristic of their surface proteins. Eight of these are known to cause disease in dogs and cats. They are: Leptospira icterohaemorrhagiae, L. canicola, L. grippotyphosa, L. pomona, L. bratislava, L. automnalis, L. bataviae, L. hardjo, and L. grippotyphosa . The first four are the most common ones that infect dogs.

In the United States, the disease is always present in the environment for your dog to pick up. This is because it is perpetuated in rats, and wildlife, as well as domestic livestock. Veterinarians see more cases in the late summer and fall - probably because that is when pets and wildlife are out and about. More cases also occur after heavy rainfalls. The disease is most common in places around the World with mild or tropical climates. In the United States, it is seen more frequently in states with heavy rainfall. Winter conditions lower the risk because leptospira do not tolerate the freezing and thawing of near-zero temperatures. They are killed rapidly by drying but the persist in standing water, dampness, mud and alkaline conditions.

How Would My Dog Catch Leptospirosis ?

Most of the infected wild animals and domestic animals that spread leptospirosis do not appear ill. In these animals, the leptospira have taken up residence in their kidneys. The type of infected reservoir animals varies from area to area. In some areas it is raccoons, in others, skunks, in some, rats. When reservoir animals void urine, they contaminate their environment with living leptospira. These carrier wildlife shed leptospira intermittently. Sometimes they shed for months and sometimes for life.

Pets can become infected by sniffing this urine. More often, the leptospira are washed by rains into standing water. Then pets wading, swimming or drinking the contaminated water, develop the disease. Although this is the way that leptospira usually pass from animal to animal, they can also enter through a bite wound or through the pets eating infected materials.

Because of these dynamics, pets and working breeds that spend time in wooded or swampy areas are more likely to catch leptospirosis. Dogs that spend their lives indoors or in areas that are not contaminated by carrier wildlife are less likely to become infected.

What Happens When My Dog Catches Leptospirosis?

Not all dogs that are exposed to leptospirosis become visibly ill. In a 2007 Michigan study, 25% of the unvaccinated healthy adult dogs examined in had antibody to leptospirosis which indicates that they had been previously exposed to leptospirosis without their owners noticing a problem.

But we do not know if these pet's long-term health remained unaffected. Chronic kidney inflammation (Chronic Interstitial Nephritis, CIN or chronic kidney damage) is a leading cause of kidney failure and death in dogs. You can read about chronic kidney damage here. Although there are many causes, this form of kidney damage can be one outcome of leptospirosis.

When leptospirosis does cause sudden disease in dogs, it tends to be most severe in unvaccinated dogs that are younger than 6 months old. These are the pets most likely to suffer life-threatening liver and kidney damage. In these cases, L. grippotyphosa is often responsible. It takes about 4-12 days after exposure for the pet to feel ill.

In dogs of any age that become ill, the leptospira spread rapidly through the pet’s blood stream, usually causing high fevers, depression and joint pain. Leptospira produce powerful toxins that can attack the liver and kidneys, leading to failure of these organs. Strains of lepto vary in their intensity and in the portions of the body they attack most severely. Some varieties primarily cause liver damage, while others concentrate in the kidneys. In other pets, blood fails to clot normally - leading to bleeding.

What Are The Signs I Would See In My Dog?

There are typical symptoms that veterinarians associate with leptospirosis. But because no two cases proceed exactly alike, not all of the typical signs are likely to be present in any one pet.

The most common signs are fever and depression. These pets are cold, shivery, and stiff. They may carry their tummies tucked up do to pain. Some drool and vomit and most loose their appetite. Fever causes many dogs to drink excessively.

Later in the disease, a few pets will develop eye inflammations (uveitis), nervous system abnormalities or pass red-tinged urine. As the disease progresses, the pet may become dehydrated due to the fever, vomiting and disinterest is drinking. A drop to subnormal body temperature is a very grave sign. A few dogs, particularly juveniles, will die suddenly before many of these signs occur.

When the liver has been damaged, the pet’s skin may take on a yellowish tinge (=jaundiced = icteric) and show all the symptoms of hepatitis. When the kidneys have been severely damaged, the pet may show the signs of uremia. These organ changes can be temporary - or permanent.

How Would My Veterinarian Diagnose Leptospirosis In My Dog ?

The symptoms that I discussed above, along with a history of your dog being exposed to places were leptospirosis lurks, might make your vet suspect this disease. Leptospirosis sometimes occurs in outbreaks, and your veterinarian may be aware that it is presently occurring in your community. If your veterinarian zeros in on leptospirosis on the first examination, you are very fortunate. Because symptoms vary so much between pets and because most veterinarians only see a few cases from time to time, it is common to miss the diagnosis on the first examination.

To make the diagnosis - or rule it out - your veterinarian will order blood tests (CBC & Chemistry). One of the typical signs found in blood tests as leptospirosis progresses, is an elevation in the number of white blood cells in the pet’s blood. The cells that tend to go up in leptospirosis are the neutrophils. However, very early in infection, white blood cell numbers can be lower than normal. There are often other chemical abnormalities that suggest leptospirosis - changes in liver enzymes, blood-clotting cells (thrombocytes) and kidney health values (BUN/creatinine). Evidence of damage to the pet's kidney’s would also be reflected in abnormal urine analysis results.

There are a very large number of diseases of dogs that can give test results identical to that seen in cases of leptospirosis. These include ehrlichiosis, babesiosis, autoimmune disease, infectious canine hepatitis, canine herpes virus, canine brucellosis and certain poisonings. Because of this, your veterinarian may place your pet on antibiotics while another test is run. This is the leptospirosis PCR test. This test is extremely sensitive in finding the presence of leptospira in your pet’s body. After the first ten days of infection, antibodies against leptospirosis can be detected in your pet’s blood if it has encountered leptospira. However, antibody detections is not as valuable as a positive PCR test in dealing with leptospirosis. The antibody test can be positive in pets due to previous vaccinations or a prior exposure to lepto that has nothing to do with your pet’s current health problem. Occasionally the diagnosis can be made by seeing leptospira microscopically in the pet’s urine.

How Will My Veterinarian Treat Leptospirosis In My Pet?

The treatment of leptospirosis is much easier than the diagnosis. Fortunately, many common antibiotics kill leptospira. Antibiotic resistance is not a problem in leptospirosis so ordinary penicillin, tetracycline and erythromycin all work well. Most veterinarians keep infected pets on one of the tetracycline-class antibiotics for an extended period after recovery to try to prevent a carrier state from developing.

Sick pets require intense supportive care to get them through the early severe stage of the disease. Dogs with stomach involvement need anti-emetic medications to lessen vomiting. Dogs that vomit need intravenous fluids to stem dehydration and correct blood acid/base balance. Rigorous fluid therapy also helps flush out the pet’s kidneys and, hopefully, protect them from permanent damage. When the pet’s kidneys have shut down and toxins are accumulating in its blood, hemodialysis has even been used.

Many pets make a full recovery. A few go on to suffer chronic renal failure or develop chronic active hepatitis - neither of which is curable.

How Can I Prevent My Pets From Catching Leptospirosis?

Limiting your pet’s access to contaminated water is the best way to avoid leptospirosis. But there is another potentially larger problem. Feeding pets and wild critters outside your home attracts rodents and possible wildlife-carriers and should be avoided. Most urban Americans know that sanitation is important in reducing rat populations around their home. But few realize that feeding urban pests, such as raccoons, or maintaining feeding stations for feral cats also increases the risk that your pet will be exposed to leptospirosis. It is not that ferral and stray cats are known to spread lepto, but feeding them is known to attract raccoons - known lepto spreaders (vectors). You can read a bit about leptospirosis in raccoons here.

Vaccination:
Your other option is to have your pet vaccinated. The American Animal Hospital Association (AAHA) considers leptospirosis vaccine a “non-core” vaccine for dogs. That is, they do not recommend pets receive it unless there is a good chance they will be exposed to leptospirosis. The main reason for this is that veterinarians see more vaccination reactions following the administration of vaccines containing leptospirosis than any other vaccines. These reactions range from the minor inconveniences of pain at injection site, facial swelling and hives to a fatal anaphylactic reaction. Which pet will experience them cannot be predicted.

The immunity that leptospirosis vaccinations give is short lasting - perhaps a year, perhaps less in some dogs. Occasionally, the vaccine does not protect at all. Vaccine manufacturers have known the drawbacks of their leptospirosis vaccines for years.

However, in 2004, The Ft. Dodge division of Wyeth Pharmaceuticals came out with a multi-strain leptospirosis vaccine produced from leptospira sub-units (LeptoVax 4). Researches have long suspected that the cellular debris and other extraneous material that found its way into leptospirosis vaccines might account for the high frequency of vaccine reactions. This sub-unit technology is thought to allow only the leptospira proteins necessary for your pet’s immunity to be injected. Hopefully, products like these will be safer than the older methods of production but just as effective. But remember - no leptospirosis vaccination is without risk and it will take a number of years to evaluate these new products in the field.

So you and your veterinarian must decide if your pet’s risk of catching leptospirosis justifies yearly vaccination. In making that decision you must ask if your pet frequents areas that may harbor leptospirosis. You must also know if leptospirosis is occurring frequently in your community.

You must also consider if your pet, or its siblings, have had previous vaccination reactions. Reactions also seem to occur more frequently in smaller breeds than larger ones.

I suggest that the first vaccination be at 14-16 weeks of age. It can be given as early as 12 weeks of age, but I seen no need for this unless the pup's exposure risk is high. I also suggest it be given during a week when no other vaccinations are give. Some high-risk work breeds receive leptospirosis vaccination more frequently than once a year. Obtaining a blood sample and checking the dog for protective levels of antibody is a safer option.

Vaccination does not always prevent infection - but it tends to make the disease much milder, if infection occurs. There is the potential for vaccinated dogs that do become infected to become long-term carriers of leptospirosis. Some long-term carriers have a more frequent incidence of reproductive failure and stillbirths.

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