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Leptospirosis Vaccine May Be Killing Dogs

woman caressing a dogStory Highlights
  • Leptospirosis is a treatable bacterial infection that can be contracted by dogs through contact with the urine of infected animals.
  • Vaccinations against leptospirosis are associated with severe adverse reactions in dogs and have been linked to 120 deaths over the last two years.
  • Although the infection is transmissible to humans, few cases are reported in the U.S.

Leptospirosis is a bacterial disease spread through the urine of infected rats, wildlife, and canines. Although it is treatable with antibiotics if it is caught early, the disease can be fatal to dogs—particularly puppies and young animals. Symptoms can range from mild lethargy and depression, to more serious symptoms like abdominal pain, jaundice, and liver damage. Leptospirosis illness leads to death in approximately 20 percent of cases, usually because the early symptoms are common to many diseases and may go unrecognized.

According to the American Veterinary Medical Association’s information of leptospirosis, symptoms may include “fever, shivering, muscle tenderness, reluctance to move, increased thirst, changes in the frequency or amount of urination, dehydration, vomiting, diarrhea, loss of appetite, lethargy, jaundice (yellowing of the skin and mucous membranes), or painful inflammation within the eyes,” among many others.1

Leptospirosis is not a new disease and actually is not a common problem in dogs (and does not appear to be a problem in cats), but increased awareness and testing have led to an increase in diagnosis.2

Risk and Prevention

Risk factors for contracting leptospirosis include drinking from contaminated sources, such as ponds, puddles or streams, roaming on rural properties where potentially infected wild animals may be, exposure to wild or farm animals, and contact with rats or infected dogs.1 Leptospirosis may also be contracted in urban areas through infected rodents. Preventive measures include reducing rodent populations, minimizing dogs’ exposure to wildlife, and avoiding stagnant-water conditions.

Potential Dangers of Leptospirosis Vaccines

There are vaccines against leptospirosis, but they are not on the “core schedule,” meaning they are only optionally offered. They also do not come highly recommended and many veterinarians are seriously opposed to them, maintaining among other things, that “the vaccine can actually cause the disease in dogs, and it has also been linked to early kidney failure in older animals.3

Vaccines against leptospirosis reportedly are associated with “as many or more adverse reactions than occur for any other” optional vaccine on the market.4 Others have agreed that the leptospirosis vaccines in general may “cause the most frequent and violent reactions” and, except in places where infection is a “severe threat, the benefits… do not outweigh the risks.”5

Nobivac L4, a new tetravalent vaccine against leptospirosis, was introduced in 2013 to cover newer strains of the bacteria found in Europe, and reports have since accumulated indicating that the vaccine has caused so many deaths and severe adverse reactions that the World Small Animal Veterinary Association (WSAVA) has warned against using it in puppies younger than 12 weeks of age, though other sources say the WSAVA disclaims that statement, and the vaccine is in fact routinely given to very young pups.6

According to the Daily Mail, more than 2,000 adverse reactions to the vaccine, including 120 deaths, have been linked to Nobivac L4 in the last two years.7 Reported side effects have included epileptic fits, swollen glands and blindness.

Dog breeder Carol Blackburn-Harvey recently brought attention to the issue in Great Britain when she lost her rare, prize dog to side effects of the vaccine. Manufactured by MSD Animal Health, a subsidiary of Merck Sharp & Dohme, Nobivac L4 is currently being monitored by the Government’s Veterinary Medicines Directorate (VMD), but its refusal to disclose the full number of known adverse reactions has sparked suspicions that the problem is being under-reported and the public under-informed.4

Bridgette Evans, another experienced and accredited dog breeder, who believes that every dog she has had vaccinated with Nobivac L4 was adversely affected, said:

Vets are not willing to admit or are in denial about the risk posed by the vaccine—it can kill perfectly fit and healthy dogs.4

A spokesperson for MSD, however, says:

The adverse event may have been related to an underlying disease, using other drugs at the same time, or other non-drug related causes. Therefore, marketing authorization holders and the authorities are obliged in the EU to apply a causality assessment to each case indicating the likelihood of an adverse event being linked to product administration.4 

Leptospirosis in Humans

Though leptospirosis is a zoonotic infection, meaning it can be transmitted to humans, it is rarely seen in humans in the U.S. There are estimates of between 100 and 200 human cases per year and half of those cases occur in Hawaii.8 Infection is much more prevalent in tropical climates and in impoverished areas of the world with poor sanitation and underdeveloped infrastructures. Epidemics may occur when there are floods, and infections are more common in times of increased rainfall.

The World Health Organization (WHO) estimates the worldwide prevalence of leptospirosis in humans at 0.1 to 1 per 100,000 people in temperate climates and 10 or more per 100,000 in tropical climates. Occasional epidemics may increase the number to 100 or more per 100,000 people.9


1 Leptospirosis. American Veterinary Medical Association. Copyright 2016.
2 Becker K. This Vaccine Can Impair Your Dog’s Immune System. Healthy Pets June 10, 2015.
Becker K. Leptospirosis: Yes, You COULD Get This Disease from Your Dog, But… Healthy Pets Feb. 25, 2013.
Yorke H. Vets’ Vaccine Alert After Claims of Dog Deaths. The Telegraph July 2, 2016.
5 Vaccinations: Leptospirosis. The Angry Vet.
Guthrie A. WSAVA Slams Daily Telegraph Story About Leptospirosis Vaccine. Veterinary News July 6, 2016.
Miller S. Thousands of Dogs Dying or Suffering Severe Reactions After Being Vaccinated Against Bacterial Infections. Daily Mail July 3, 2016.
Centers for Disease Control and Prevention. Leptospirosis. Apr. 17, 2015.
9 World Health Organization. Leptospirosis Burden Epidemiology Reference Group (LERG). Zoonoses and Veterinary Public Health 2016.

20 Responses to Leptospirosis Vaccine May Be Killing Dogs

  1. Karol Lavia Reply

    August 20, 2017 at 7:20 am

    Pet Smart told me I needed to give this vaccine to my 7-year old malamute for her trip to Mexico. Absolutely a lie. She died three weeks later from the disease after terrible suffering. This vaccine should be banned. I was heart broken.

  2. Elizabeth Badger Reply

    August 1, 2017 at 12:01 pm

    The Leptospirosis vaccine caused masticatory myositis in our son’s 8.5 year old Rottweiler almost 2 years ago. For anyone not aware of this terrible ailment, his jaw clamped totally shut, where it couldn’t not even be attempted to be open under heavy anesthesia. He could neither eat or drink. This ailment also went undiagnosed by the vet who administered the vaccine, and another vet that saw him. It was only after our own extensive reading, that did we on our own, that we figured out what was wrong with him, and then went to the vet with the recommendations based on our readings, for a course of action to save his life. It took almost a full year of prednisone for him to recover. Once he was off the prednisone, shortly after he developed Osteosarcoma in his front leg. He was sent to the Rainbow Bridge just last week. And he was a healthy dog prior to the vet convincing our son that this vaccine was required. He was never told that there were possible side effects, and why would he even think that there would be. After much reading, it is more than evident that he should never have been given that vaccination, nor should he have been given the rabies shot prior to a titre test. Although, he lived to be almost 11 years old, which is remarkable for a Rottweiler, he could of been spared a lot of pain and discomfort, had he not been given these unnecessary vaccines.

  3. elle Reply

    July 8, 2017 at 2:36 pm

    My dog went into a chock 2 hours after the vaccination . He would stop for 15 minutes starring into a wall or a bush , without moving a muscle . Now , 4 months later , he is all of a sudden afraid of cars in the street . He eats and drinks as normally , but he is as far from
    normal as can be .
    He is a 9 years old Basset Fauve de Bretagne , the vet didn´t ask before she gave it to my dog and I had only asked for a Rabies vaccination .
    None of the vets , I have taken my dog to , will accept any a these facts and treats me , like I am crazy . It is my 5.th dog , and I have had big dogs earlier , that went to training schools , one was even an Agilty champignon , so I am a very serious dog owner .

  4. D M C Reply

    July 7, 2017 at 3:40 am

    My 8 year old perfectly healthy xbreed lost her sight within 3 weeks of receiving her Lepto 4 booster. I was told she has a brain tumor but I now have serious doubts as she is still with us after nearly 9 months. I feel so helpless as there is nothing I can do to establish the truth and I have lost faith in vets as I feel these boosters are more about making money than caring for my dog. Think very seriously before consenting to your pet receiving this drug, I am convinced it is responsible for my dogs blindness and nobody will help !

  5. Diane Botts Reply

    May 20, 2017 at 6:53 am

    Ever since my pup had a reaction from the lepto. Vaccine he has become very aggressive in his behavior. He had a bad reaction from the vaccine and I had him treated but he now has become very aggressive. Could this be a result from the vaccine?

  6. James Reply

    May 6, 2017 at 6:30 am

    The UK version of L4 from Intervet/MSD Animal Health killed our 5 year old Akita. She stopped eating and lost 30% of her body weight over 6 weeks while thes struggled to find anything wrong. She fnally was put to sleep with nothing found to be wrong. The only trearment she had received at the vets was the injection of Nobivac L4 Leptospirosis vaccine.

  7. Cathy Reply

    May 5, 2017 at 11:36 am

    My Jack Russell, who is almost 15 and super healthy got her Lepto booster last week before we were leaving to move out west for the summer. We occasionally need to board our 2 dogs because of whitewater rafting trips, and they have to have a kennel cough vaccine and a lepto vaccine in order to board them. She started feeling poorly within a few days, and I could smell it on her breath that she was sick. She then developed a high fever and runny discharge from her nose accompanied by constant sneezing. She is very lethargic, but thankfully she is still eating and drinking well. My vet said that it probably wasn’t the vaccine, but I think it is. She’s never sick and this is very unlike her. They placed her on antibiotics and I’m hoping it’ll bring her around

    • Rebecca Reply

      May 22, 2017 at 11:09 pm

      Cathy, Did your dog get better? I have a Jack. He got a lepto shot today and seems to be experiencing similar symptoms. He can’t walk. I have to carry him around. Since it’s only been 5 hours, I’m just hoping it’ll get better.

      • Cathy Everhart Proctor Reply

        May 29, 2017 at 7:14 pm

        Rebecca, my jack Russell is still ill. I have to carry her as well, but we discovered that she had a serious staph infection as well as e-coli. We got rid of the upper respiratory thing, and now it is returning. Meanwhile, $1500 later, I still believe with all of my heart it was the vaccine that started everything.

  8. Prince Reply

    May 5, 2017 at 3:13 am

    My dog was mistakely given an overdose of this vaccine and now she is not eating,she is vomiting ,she is not active (dull) and her stool is watery

  9. Prince Reply

    May 5, 2017 at 3:12 am

    My dog was mistakely given an overdose of this vaccine and now she is not eating,she is vomiting and her stool is watery .

  10. Eve Reply

    April 8, 2017 at 9:31 pm

    Also i wanted to add that one of my dog got overvaccinated with rabbies vaccine because she was a rescue dog and she developped seizures and lost her hair all around her ears. After fighting quite a bit with the vet, i finally could obtain a written exemption of any further vaccinations . Why do vets wait for our pets to be in serious health geopardy to recognize that over vaccinations is so damaging to their health????

  11. Adam Reply

    March 30, 2017 at 2:41 pm

    This one s for leptospirosis which is not recommended as a “core” vaccine to be given routinely to your dog unless in a leptospirosis area, though it has course of course become the norm for all dogs today.

  12. Anita Azzopardi Reply

    October 8, 2016 at 9:31 am

    My dog developed Pancreatitis 1 year ago after receiving the Lepto shot. Not realizing that this was the connection, she received another Lepto injection this year and 2 months later went into liver failure. I now see the correlation, and wish my Vet would have been honest and let me know that a 13 year old Pug did not need this. Thanks to the Vet being money hungry, instead of caring about my dog, she is no longer with us. Please do your research before allowing your vet to give your dog vaccines. 10-8-2016.

  13. Cornell Preiss Reply

    August 26, 2016 at 2:18 am

    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. 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.

  14. Velobwoy Reply

    July 29, 2016 at 4:14 pm

    Lepto is no joke. I contracted it 19 years ago in Hawaii. People occasionally die from it there, if they leave it untreated. It is a spirochete, like Lyme disease, and I suspect it uses some of the same mechanisms to hide from the immune system within one’s cells by camouflage, moving into different life cycles when threatened, etc… How the hell some genius thinks they can vaccinate against something like that, I’d love to hear.

    • Jo Reply

      July 31, 2016 at 6:10 pm

      Me thinks you’ll be waiting a long time, unless you’re into reading a lot of baloney. But I doubt it.
      I won’t consent to vaccinating my pets at all. The only 2 times my dog had to have a rabies vaccine was those times I (unfortunately) HAD to bring her to the vet for physical issues that I couldn’t address at home. Would that I could have!
      Each time she had the rabies vaccine she was lethargic for several days.

    • S Cox Reply

      March 23, 2017 at 12:45 pm

      I am sorry , Velobwoy, but your comment is pure nonsense. You think because an infection is severe the vaccine will be less effective? For your information, many “geniuses” have actually researched scientifically and proven that many vaccines safely prevent lethal diseases, as smallpox, meningitis, pneumonia, etc. This has also been shown clinically. I have not legitimately researched Leptospirosis vaccine for animals to evaluate it’s risks versus benefits so would not make such a ridiculous claim based on here-say and anecdotes. You could do this unless you rely on one of the radical anti vaccine sites that have no credibility.

  15. Stan Reply

    July 29, 2016 at 12:29 pm


    Repeating Dr Becker’s claim in your article is poor science…at best. I have NOT been a great proponent of Lepto protection for canines during my 45yrs of practice (even the newer lower antigen L4), but stating (without reference to the source) that science has demonstrated reversion to virulence for a killed bacterin and “the vaccine can actually cause the disease in dogs” undermines the believability of some other good points in your discussion about vaccine protocols.

    I have also observed other “poor veterinary medical science” linked to the Mercola site in the past.


    Stan Zbylot DVM

  16. Elizabeth Young Reply

    July 29, 2016 at 10:57 am

    After the 1st year shots , most dogs will have immunity for at least 8 years , or , almost the length of life of the dog . Check out http://www.critterfixer.com , a Texas Vet’s website or Dr. Karen Becker’s website ( holistic vet ). Since I don’t over vaccinate my dogs have no weird skin allergies and no food allergies . I feed non-GMO dog food that is grain free . Major vaccine makers will not sponsor research on this because it may go against the bottom line . Same for traditional vets , who , like pediatricians , get office visit fees every time you bring your dog in for a battery of shots . Helps their bottom line . As for checking titers , a dog can have cellular immunity and no or low titers and still be immune to disease . Plus , they are expensive . Do ” the most nothing ” , feed the best food , exercise , don’t buy puppy mill dogs ( genetic problems ).

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