Leptospirosis In Your Dog

How Dogs Catch It, How Vets Try To Cure It, How We Can Prevent It

Ron Hines DVM PhD


If you came to this page because of a concern about leptospirosis vaccine reactions, go here

Where you live is important when deciding the risk of your dog catching leptospirosis see the map here

What Causes Leptospirosis?

Leptospirosis is a disease found in temperate climates throughout the world. It is caused by a bacteria – a peculiar, very thin, corkscrew-shaped one with a hooked-shaped “tail” (they really have no front or rear). Each has undulating motility organs that remind me of Dracula’s cape. (ref) The whole group are called spirochaetes. Most species of spirochaetes live free in the environment and cause no illness. But a few species of spirochaetes have evolved to cause particularly nasty diseases. Those include the leptospira that cause leptospirosis, and their close relatives, the spirochaetes responsible for  Lyme disease, relapsing fever and syphilis. None of them, other than syphilis, are particularly choosy about whom they infect. 

Traditionally, leptospirosis threat was associated with areas of heavy rainfall, high humidity, a temperate or tropical climate, flooding and lack of basic sanitation. Rats were thought to be the main transmitter – they apparently carry the organism in their kidneys and spread it through urine contamination. But that may no longer be the case. Expand the map at the top of this page to see where most cases in dogs occur in the USA. Late summer and fall see the most cases. The organism generally enters the body from contaminated water or soil through the mouth, nose, or eyes – or through broken skin . Hawaii leads the Nation in reported cases. (ref) It is also the state with the highest average rainfall.

Is There More Than One Type Of Leptospirosis Organism?

Yes, there are many. They are called subtypes or serovars.

Serovars differ in the structure of certain of their surface constituent (lipopolysaccharides). These surface compounds contain both carbohydrate and fatty components. Since these compounds are the ones that your dog’s immune system recognizes, immunity to one subtype/serovar may not impart strong immunity to other serovars. There have been over 250 different leptospirosis serovars reported through 2009. (ref1, ref2)  The ones that most commonly infect dogs are Leptospira icterohaemorrhagiae, L. canicola and L. kirschneri/grippotyphosa. Other serovars are occasionally responsible and the prevalence of all of them vary from place to place and time to time.

Both Zoetis’ Vanguard® L4 and Boehringer Ingelheim ’s Recombitek® 4, current leptospirosis vaccines contain killed portions of the L. canicola, L. grippotyphosa, L. icterohaemorrhagiae and L. pomona organisms – the serovars they feel your dog is most likely to be exposed to. But when your dog becomes infected, current antibody tests (MATs) have limited ability to accurately determine the serovar(s) involved. Read more about MATs tests farther along.

How Would My Dog Catch Leptospirosis ?

How long After Exposure Might My Dog Become ill?

Most of the dogs and infected wild animals and domestic livestock that spread leptospirosis do not appear ill. In those animals, the leptospira have taken up residence in their kidneys and are shed in high numbers in their urine. All chronically infected animals can shed leptospira intermittently or continuously. In dogs, it takes about 2 weeks before the leptospira begin to appear in their urine. They can sometimes be found there for only a few days; but sometimes for more than two years. (ref) The incubation period – the time from exposure to illness – can be only a few days or as long as two weeks. In experimental studies, the average was about a week. (ref) However many dogs that are infected or exposed never become visibly ill. (ref1, ref2)

Today, most dogs in the developed (prosperous) world that catch leptospirosis, catch it from wildlife reservoirs, not other infected dogs. The species of animals that spread the disease vary from place to place. In areas of poverty where rats are prevalent, those rodents are thought to be the prime transmitter. But in prosperous areas where urban wildlife like raccoons are abundant, suspicion falls on them. (ref1, ref2, ref3, ref4 

It is probably not that the endearing raccoons are any better a carriers of leptospirosis than a number of other critters. Its just that they are the most clever and fearless about invading human and dog-occupied space in their search for food.   (ref) Nothing interested your dog more than sniffing the scent of exotic urine. By the time your dog sniffs a urine-contaminated location, the raccoon or other leptospirosis vector is long gone.  Leaving food out for stray cats presents the same under appreciated threat. (ref) The second way the disease travels is when that urine gets washed into bogs, streams and impoundments that your dog frequents. Drainage pipes and culverts are a choice location for racoon latrines. I cannot tell you which is most likely – although floods and heavy rainfall are often associated with leptospirosis outbreaks.  Dogs and cats that spend their days indoors are considerably less likely to encounter leptospirosis than those that spent much of their time off-leash and out of doors.

What Are Some Signs I Might See If My Dog Became ill With Leptospirosis?

I mentioned earlier that many dogs show few signs of illness once infected with leptospirosis and succeed in riding their bodies of these organisms on their own. There is really no advantage for an organism to make its host ill. But there is really no way of knowing which dog will react violently to the leptospira infection and which will not. Perhaps it is the damaging ability (virulence) of the particular leptospirosis serovar your dog was exposed to. Perhaps the genetic abilities of the immune system of your dog. Perhaps the size of the dose of leptospira organisms it encountered. Perhaps all three. (ref)  Whatever the case, veterinarians know a dog’s life might be in danger when signs of kidney, liver or lung damage begin to appear.

Fever, muscle pain and a depressed mood are often the first signs an owner observes – the signs that motivate them to bring their pet in to their veterinarian. Fever is also common. It motivates dogs to drink and consequently urinate more. Generally, these dogs show little interest in food.  Vomiting is common. Some have diarrhea. Their midsection (abdomen) might be tender to the touch. As the disease progresses, some of these dogs show a yellowish hue to their gums and the whites of their eyes – evidence of jaundice and liver damage. During a leptospirosis infection, these organisms move freely through the dog’s blood. Depending on the organs most affected, there can be a great variation in signs. A particularly nasty form of leptospirosis affects the lungs (leptospirosis pulmonary hemorrhage syndrome = LPHS). (ref) Those dogs present with shortness of breath (dyspnea) and perhaps cough up blood (hemoptysis). Something has decreased the ability of their blood to clot normally. So nose bleeds, increased tendency to bruise, and blood in the stool might accompany LPHS as well. These are signs similar to DIC, a cytokine “storm” ( CS). (ref) If kidney damage becomes severe, the signs of leptospirosis are the signs of uremia (kidney failure). A subset of dogs are left with chronic liver problems. (ref) You can read a summary of the various signs that have been associated with leptospirosis in dogs here and  here

What Tests Will My Veterinarian Use To Diagnose Lepto In My Dog?

Like many infectious disease your veterinarian encounters, the initial blood analysis reports are rarely definitive for one certain disease. But with lepto, they do tell your veterinarian that a disease is affecting your pet’s whole body and that it is likely due to some infectious organism.  Your dog’s total white blood cell count (WBC) will often be high. It is quite common for its thrombocyte count, the cells involved in blood clotting, to be low and for its neutrophil count to be high. Because of bleeding, you dog might be anemic as well. Since the kidneys are often a destination for leptospira, tests that detect a decrease in kidney function (creatinine and BUN) are often elevated as well. Liver tests (ALT, GGT, bilirubin) are commonly abnormal. Alkaline phosphatase (AP) – an enzyme released by many injured tissues is often elevated. Your pet’s urine analysis (urinalysis) often shows signs of kidney infection as well (pus cells, casts and protein).

The symptoms that I mentioned earlier, along with a history of your dog being exposed to places were leptospirosis lurks, and these blood results might lead your veterinarian to suspect that your dog has contracted leptospirosis. If that is the case, your vet might order one or more of three specific tests: the MAP test, a PCR test, or a leptospirosis IgM test. All these tests have their limitations – but they are the best we veterinarians currently have to offer. (ref)

MAT Test  Modified Leptospirosis Agglutination Test

This test looked for antibodies in your pet’s blood directed against leptospira – evidence the organism is or had been present. Weakly positive tests can be quite hard to interpret. Also, the test can be negative early in the disease – before the pet has had time to produce the antibodies the test looks for. Some positive tests can been from a previous leptospirosis vaccinations you dog received. It generally takes 10-14 days for a current leptospirosis infection to produce MAT-positive results (an elevated antibody titer ) – although some dogs develop a positive titer earlier.

Generally, the only way to be certain that a positive titer is related to a current infection is to measure it early and again later during the illness and find that the titer has increased substantially. (rptref) It is usually the first test your veterinarian runs because it is readily available at central labs and relatively inexpensive as test costs go. It is not an easy test for labs to run. First, the results can be quite hard to interpret (there is quite a bit of subjectivity). Live cultures of various leptospirosis serovars must be maintained at the lab – always a threat to the employees. Different labs have been known to interpret test results differently on the same dog. Antibodies to one serovar frequently cross-react with others. So using the MAT test, one can never be certain which of the many leptospira strain or strains your dog is reacting to.

A PCR Test ….Leptospirosis Polymerase Chain Reaction Test

PCR tests amplify telltale leptospira DNA components, making them appear in quantities that can be identified as to their origin. This test is likely to pick up the presence of leptospirosis before the MAT test does. Test results are not influenced by prior vaccination. It is best performed before a dog begins antibiotic therapy and before the dog might naturally clear leptospira from its body. Both of of those situations might yield a false-negative PCR result regarding your pet’s illness. During the first ten days after infection, blood samples are the specimen of choice. After that, urine might be a better choice. Some vets send off samples of both. The test rarely misses the leptospirosis organisms when they are present in moderate or high numbers in the sample, but it too has limited effectiveness in determining which serovar of lepto it might be. The PCR test can also not tell the difference between a dog chronically infected with leptospirosis that is shedding leptospira in its urine and a recently infected dog.

In Office Tests

Two companies, Idexx Laboratories and Zoetis, market in-office leptospirosis tests that veterinarians can perform. These tests rely on detecting  the early antibodies (IgM) that dogs produce when they first encounter the leptospirosis organism. Later on, and in vaccinated dogs, the antibody is mostly IgG). The development of these tests has been a great help in getting your dog into therapy quickly –  before the results of central lab MAT and PCR tests have time to arrive.  (ref)

The  Idexx test is their SNAP®Lepto ; the Zoetis test is their Witness®Lepto. I can not tell you if one is superior to the other. Zoetis funded a study that found their product better than Idexx’s. But I put little stock in company-funded articles.  It doesn’t matter if it’s a car, shaving cream or a lab test; they always find their product superior to the competition. (ref)

Other Diagnostic Methods

Pathologists and veterinary microbiologists can sometimes identify leptospira when blood and tissues samples are examined with dark field microscopy. A variety of other methods have been reported as well (eg RSAT, CF, LFA), but none to my knowledge are readily available to practicing veterinarians. (rptref)

Laboratories and research centers can also attempt to grow the leptospirosis organisms from tissue submitted to them. Leptospira can be quite difficult and expensive to grow. The test procedure is slow and expensive. Other bacterial contaminants in the submitted sample often crowd out the leptospira. So growing (culturing) leptospira organisms is generally reserved for scientific experimentation aimed at providing new knowledge about the disease.

Is There A Danger I Could Catch It From My Dog?

It is theoretically possible – but quite unlikely. Use common sense and practice good hygiene, just like veterinary and human nurses do. (ref)

Here are some things that minimize the transfer of infectious diseases of all kinds. They apply to an active case of leptospirosis in your dog as well:

Have only one, healthy, family member care for the dog. It should not be a child. Confine your pet to an easily sanitized area of your home. Prevent exposure of your other pets. Wear protective gloves when cleaning up after your dog. Take your dog out on a leash frequently to urinate and defecate. Only allow the pet to urinate and relieve itself on dry concrete surface that can be easily sanitized with bleach. When you are potentially exposed to any secretions or waste from your pet, disinfect your hands liberally with a common disinfectant. Alcohol-based sanitizers, povone iodine and Lysol all kill leptospira rapidly. So does bleach, heat and drying. Should you feel ill, always inform your physician about your pet’s illness. If you are a worrier and want to be more certain your dog does not remain a leptospirosis carrier, have a PCR test or two performed on its urine after its recovery.

How Will My Veterinarian Treat Leptospirosis In My Pet?

Most every veterinarian who encounters a case of leptospirosis in a dog will place that dog on antibiotics. A number of antibiotics have been shown to kill leptospira in the lab. The one most commonly used in the field is probably doxycycline. However dogs with any form of stomach and higher intestine inflammation commonly vomit doxycycline back up. So your vet might resort to a drug in the penicillin class. Those drugs have also been shown to kill leptospira, but they are not thought to be as effective in preventing the development of carrier dogs. Once the dog has improved, your vet might then switch the pet over to doxycycline. (rptref1, ref2)

Sick dogs can require intense supportive care to get them through the early severe stages of leptospirosis. Dogs that vomit or show intestinal involvement generally receive medications to calm their stomachs (eg metoclopramide, maropitant) and meds to decrease stomach acidity (eg ranitidine or omeprazole). Diarrhea needs attending to as well. Many also need intravenous fluids to combat the dehydration vomiting, diarrhea and inappetence produce. If their tummies are sensitive or they show other evidence of pain, they benefit from pain-control medications (eg buprenorphine). Those with respiratory distress benefit from oxygen and some from theophylline. Dogs that are not willing eat need to receive their essential nutrients in other ways. 


Some dogs whose kidneys fail due to an acute leptospirosis infection still have the ability to recover if hemodialysis takes over the work of their kidneys for a while.  When hemodialysis is attempted, it is rarely suggested for more than 4 weeks. If a dog’s kidneys have not begun to recover by then, hemodialysis is unlikely to be helpful. Your vet would have to refer you to one of the limited number of centers where such procedures are performed.

If My Dog Recovered From Leptospirosis, Can It Catch Lepto Again?

Yes, that is possible; although veterinarians have no easy way to confirm that it happens. 

Since it is very uncommon for dogs to develop leptospirosis twice, we have little data to go on. We know that dogs and humans remain immune to the specific strain of leptospira that infected them for as long as protective antibodies linger in their bodies. That is often a year or two. We also know that sometimes that antibody immunity cross-protects against different leptospirosis serovars and sometimes it does not. But we do not know what role immunological memory plays in leptospirosis immunity or if it too is serovar specific. Immunological memory generally persists much longer than the time antibodies can be detected in the blood.

How Can I Help Prevent My Dog From Being Exposed To Leptospirosis?

I believe that in the United States, the most successful ways to limit your dog’s exposure to leptospirosis is to limit its exposure to contaminated water as well as its exposure to the urine of infected wildlife, rats and feral domestic animals.  The prime attractor of all potential leptospirosis carriers is food – food placed intentionally for those animals or food left outside for your dogs and cats. Without those food sources (as well as unsecured garbage) there would not be an urban reservoir of leptospirosis and other similar diseases. Kindhearted people, upsetting the balance of Nature do animals no service. Keep your cats indoors to prevent their exposure – the rodents that are prime carriers of leptospirosis are their natural prey. (ref)

Leptospira organisms generally enter the body through the mouth or a skin abrasion. Some have associated leptospirosis exposure with feeding leptospirosis-contaminated raw meat to dogs. But that is highly unlikely to happen when American supermarket meat is consumed. (ref) These organisms are very dependent on water, mud or damp clay soils to survive. That is because they do not possess a waterproof membrane to protect them from drying. Leptospira die quickly on dry surfaces – even if those surfaces were contaminated with urine from other infected animals. Temperatures at or above 131F (42C) kill leptospira quickly. All common household disinfectants (bleaches, alcohol based products, vinegar, lemon juice etc.) kill the organisms. Porous items need to be completely submersed in these solutions. Standing water can be disinfected using swimming pool chlorine tablets (but realize that those products are toxic to all aquatic life). Common industrial chemicals are so toxic to leptospira that obviously polluted effluent water is not as much a leptospirosis threat to your pet as are lakes and streams with water that appears pristine.

The United States army once experimented with giving their soldiers in Panama doxycycline in an attempt to prevent them from contracting leptospirosis. (ref)  I do not know if that approach holds promise.


Your other option is to have your pet vaccinated against leptospirosis. The American Animal Hospital Association (AAHA) considers leptospirosis vaccine a “non-core” vaccine for dogs. That is, they do not recommend pets receive the vaccine unless there is a good chance they will be exposed to leptospirosis. The main reason for that is that veterinarians see more vaccination reactions following the administration of vaccines containing leptospirosis than other vaccines. These reactions range from the minor inconveniences of pain at injection site to facial swelling and hives to fatal anaphylactic reactions. Which pet will experience them cannot be predicted – however I believe that the one-size-dose-fits-all philosophy accounts for many of the reactions veterinarians see. (ref)

Only you can decide if your pet’s risk of catching leptospirosis justifies the risks of yearly vaccination. In making that decision you need to ask yourself if your pet frequents areas that are likely to harbor the disease. That includes doggy parks. You need to also know if leptospirosis occurs frequently in dogs in your community. You also need to consider if your pet, or its siblings, have had previous vaccination reactions to a lepto-containing vaccine or one that did not contain lepto.

These vaccinations do not always prevent infection – but they tend to make the disease much milder when a leptospirosis infection occurs. How long immunity might persists after vaccination has not been well established. (ref1, ref2)

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