Leptospirosis in Dogs
Reports of cases of leptospirosis have increased recently across the United States. Consequently, I am hearing concern 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 vaccines, and treatment options. Other issues surrounding leptospirosis are also discussed.
What is Leptospirosis
Leptospirosis is a bacterium. Over 200 leptospirosis strains exist and most do not cause disease. Thus far, approximately seven 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, as is thought to be the case with the small recent outbreaks in northern California (5 reported cases in San Francisco) and around Philadelphia. 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, and not let the dog lick their faces until treatment is completed.
- Muscle tenderness, Lethargy
- Increased thirst
- Changes in the frequency or amount of urination
- Loss of appetite
- 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.
The most common diagnostic tool used for leptospirosis is the Microscopic Agglutination Test (MAT), this titer test measures the antibody increase against leptospirosis sp. Another more definitive diagnostic tool is the DNA-PCR, which detects the DNA of the actual bacteria, Leptospira sp, in whole blood or urine.
Treatment is highly and rapidly effective and will include antibiotics such as penicillin, doxycycline, ampicillin and amoxicillin if caught early enough. Late diagnosis may require emergency care.
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.
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 disease exposure risk versus adverse vaccine reaction and benefits need to be taken into account.
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).
- Dr. Ronald Schultz considers the vaccine only 60-80% 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 – which as Dr. Katharine Lunn of North Carolina State University points out – the MAT test does not reliably predict the infecting serovar.
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 that they do not find it clinically significant or a current health concern.
Additionally, of all of the bacterin vaccines available on the market, Dr. 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 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.