Reports of cases of leptospirosis have increased recently across the United States. Consequently, we are hearing concerns from pet caregivers about whether they should or should not have their companion dogs vaccinated against leptospirosis. Let’s take a moment here to review leptospirosis disease, causes, symptoms, the vaccine, and treatment options. Other issues surrounding leptospirosis are also discussed.
What is Leptospirosis
Leptospirosis is caused by Leptospira bacteria. Over 300 leptospirosis strains exist and most do not cause disease. Thus far, approximately ten of the leptospirosis strains (serovars) are considered clinically important for dogs.
How Leptospirosis is Spread
Leptospirosis is spread through skin or mucous membranes from contact with tissue, urine, blood, or other bodily fluids, except saliva. Most commonly, dogs acquire the disease by closely sniffing or walking through urine-contaminated water, soil, or food. They could also get it from contaminated bedding, a bite from an infected animal or by eating infected tissues or carcasses. Very rarely, dogs contract leptospirosis through breeding or from the disease breaking through the placental wall. Raccoons, skunks, foxes, moles, squirrels, opossums and rats are considered common carriers and can excrete the bacteria occasionally or continuously for several years.
In large part, leptospirosis is most commonly found in areas with warm climates and high annual rainfall. Fast-flowing or large bodies of water are not the concern, but contaminated standing puddles and wet mud after high rainfall or flooding could be involved. It is therefore impacted by climate change and residential development in once rural areas.
Additionally, leptospirosis is communicable from dogs to humans (i.e. a zoonotic disease). If a dog is diagnosed with leptospirosis, humans should wear rubber gloves, clean up urine with iodine, and not let the dog lick their faces until treatment is completed.
Symptoms
- Fever
- Shivering
- Muscle tenderness
- Lethargy
- Increased thirst
- Changes in the frequency or amount of urination
- Dehydration
- Vomiting
- Diarrhea
- Loss of appetite
- Jaundice
- Inflammation of the eyes
If caught too late, leptospirosis can result in kidney failure and liver failure. Less commonly, dogs may develop lung disease or bleeding disorders.
Diagnosis
Rapid point-of-care (POC) tests for leptospirosis can point veterinarians in diagnostic testing directions for other diseases. However, POC testing should not be used as a definitive diagnosis of leptospirosis infection or to exclude it. Veterinarians should continue to test using the Microscopic Agglutination Test (MAT), this titer test measures the antibody increase against Leptospira sp., as well as DNA-PCR, which detects the DNA of the actual bacteria, Leptospira sp, in whole blood or urine.
Treatment
Treatment is highly and rapidly effective and should include antibiotics such as penicillin, doxycycline, ampicillin, and amoxicillin, if caught early enough. Late diagnosis may require emergency care.
Vaccine
A vaccine is available for leptospirosis but only covers four clinically significant serovars out of the seven: L. canicola, L. icterohaemorrhagiae, L. grippotyphosa, and L. pomona in the United States. In Europe, the serovars in the vaccines are against L. icterohaemorrhagiae, L. canicola, L. grippotyphosa, and L. australis.
The vaccination protocol for leptospirosis is an initial shot and a booster three weeks later. After that, the vaccine must be given annually to maintain efficacy. If the annual booster lapses, your dog will need to start the protocol again from the beginning. However, please keep in mind that this vaccine is still the most common one associated with eliciting acute and per-acute adverse reactions. Thus, the pet’s lifestyle and disease exposure risk versus a potential adverse vaccine reaction need to be taken into account.
Discussion
Leptospirosis is a rare clinical disease in companion animals. Unfortunately, infected dogs can die of leptospirosis if it is not caught early enough.
The two most frequently questions I receive about leptospirosis overlap in some respects and are:
- My companion dog was vaccinated against leptospirosis, but still developed the disease. Why?
- Leptospirosis was confirmed in my area. Should I vaccinate my companion dog for it?
If your dog was vaccinated, but still developed the disease, the reasons could be:
Your dog was not vaccinated properly for leptospirosis (following the protocol described above).
- The infecting serovar is not covered by the vaccine (quite common).
- The vaccines are only 80% effective against leptospirosis.
- The diagnosis was incorrect.
When I read or hear “confirmed cases”, my first question is always, “What diagnostic tools were used to reach this conclusion?” More often than not, it is only the MAT test. While MAT is still considered by many to be the “gold standard” at this time, it is fraught with errors – and can provide false positives. Furthermore, true clinical cases of leptospirosis have MAT serological titers of at least 1:1600 or higher, and an 8 to 16-fold rise in titer three to four weeks later is typically expected to confirm the disease. Unfortunately, this is too long a time lapse to verify a true clinically significant strain. As Dr. Katharine Lunn of North Carolina State University points out, the MAT test does not reliably predict the infecting serovar because it is testing the serogroup. This can give us an idea of circulating Leptospira serovars, but is definitely not definitive.
DNA-PCR tests also have their drawbacks, but when used in combination with the MAT test, we get closer to a more accurate diagnosis. The results of all diagnostic tests should be interpreted in conjunction with your companion dog’s vaccination history, clinical signs, and clinicopathologic findings.
In essence, we could be jumping to conclusions and treating the wrong disease with the wrong medications.
If an outbreak is reported in the media, many pet parents may consider the vaccine. Again, though, the vaccine is not highly effective, and may not cover the clinically significant strain present in your area nor the serovar causing the outbreak. The only way to know the serovar involved is from water testing. You can call the county or state health department and ask. Please note, several states do not test water or areas for leptospirosis, which the common belief is that they do not find it clinically significant or a current health concern.
Additionally, of all of the bacterin vaccines available on the market, immunology expert, Dr. Ronald Schultz, maintains that the leptospirosis vaccine causes the most adverse reactions such as a Type 1 hypersensitivity, hair loss or lethargy.
In the event of a confirmed outbreak in your area, and concern about your pet’s potential to catch leptospirosis, avoidance is the best policy. I would keep your dog away from standing water, slow moving streams, wet mud and puddles. As well, I would watch for any “ADR” (Ain’t Doin’ Right) mild or vague symptoms and take your companion dog in for a thorough check up and laboratory testing that includes both MAT and DNA-PCR testing for leptospirosis.
References
Dodds, W. Jean, DVM. “Snapshot of Leptospirosis Strains & Vaccine.” Dr. Jean Dodds’ Pet Health Resource. N.p., 19 July 2015. http://drjeandoddspethealthresource.tumblr.com/post/124510474596/leptospirosis-vaccine#.WLbr-_krLIV.
Lunn, Katharine, PhD. “Leptospirosis in Dogs.” Merck Veterinary Manual, Feb 2022. http://www.merckvetmanual.com/generalized-conditions/leptospirosis/leptospirosis-in-dogs.
Schultz, Ronald, PhD, and Karen Becker, DVM. “The Pets Most Likely to Suffer from Vaccine Adverse Reactions.” Healthy Pets. Mercola, 08 Nov. 2013. http://healthypets.mercola.com/sites/healthypets/archive/2013/11/08/rattlesnake-vaccine.aspx.
Schultz, Ronald, PhD. “Update on Leptospirosis Vaccines.” Dr. Jean Dodds’ Pet Health Resource, 29 May 2013. http://drjeandoddspethealthresource.tumblr.com/post/51665176980/leptospirosis-dog-vaccines#.WLcGFvkrLIV.
Originally Published: March 5, 2017
Updated: April 21, 2024