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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.

9 Responses to Leptospirosis Vaccine May Be Killing Dogs

  1. 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????

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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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