Leptospirosis vaccine for dogs in Kerala: is it necessary?

Whether the leptospirosis vaccine is necessary for your dog is a decision for your vet; the guideline does not give a blanket yes or no. The World Small Animal Veterinary Association (WSAVA) calls it a core vaccine only where canine leptospirosis is endemic, the types of the bacteria involved are known, and a suitable vaccine is available. Where all three hold, it says vaccinating all dogs is highly recommended. This article sets out those conditions, what a 2013 study of dogs in three Kerala districts found, and what to ask your vet. The rest of the puppy plan is in dog vaccination schedule India: core vaccines and when.

What are the signs of leptospirosis in dogs, and when should you see a vet?

The Merck Veterinary Manual says some leptospirosis infections cause no signs, while others lead to sudden and severe disease. The most common pattern in dogs begins with sudden kidney disease, with sluggishness, loss of appetite, vomiting, dehydration and back pain. The disease can also cause sudden liver failure, often leading to yellowing of the gums, skin and eyes. Some dogs develop bleeding disorders, which can appear as nosebleeds, bruising, or blood in the faeces or vomit. Coughing or difficulty breathing can occur, as can muscle pain, stiffness, weakness, trembling or reluctance to move.

A dog with any of these signs should see a vet promptly, especially if it has been in flood water or other water that may be contaminated. Merck says the disease can affect almost all mammals, including people, and that strict cleanliness is essential. It advises wearing gloves when cleaning up urine and washing hands thoroughly after handling the dog, at least until antibiotic treatment is finished.

How do dogs and people catch leptospirosis?

The US Centers for Disease Control and Prevention (CDC) says leptospirosis is caused by the bacterium Leptospira, which can be found in contaminated water or soil. The bacteria are spread through the urine of infected animals and can survive in contaminated water or soil for weeks to months. Animal urine in soil and on other surfaces can get into floodwater or rainwater. People can be infected by contact with water or soil containing urine or body fluids from infected animals, especially after hurricanes, flooding or heavy rainfall; by directly touching body fluids from an infected animal; or by eating food or drinking water contaminated with infected urine. The CDC lists livestock, dogs, cats, rodents, marine mammals and wild animals among the animals that carry the bacteria, and says some infected animals show no symptoms at all.

Merck says dogs become infected through contact with contaminated urine or water, or through bite wounds or damaged skin. Infected dogs can then become carriers and shed bacteria in their urine for months or even years.

The CDC’s advice for lowering a person’s risk includes not swimming or wading in water that might be contaminated with animal urine, avoiding contact with animals that may be infected, covering cuts and scratches with waterproof bandages, and wearing waterproof protective clothing, shoes or boots near floodwater.

What does WSAVA say about the leptospirosis vaccine?

WSAVA’s 2024 guideline says leptospirosis is a life-threatening zoonotic disease that is widely distributed around the world. It makes the vaccine core if leptospirosis is prevalent in dogs in the regions where the dog lives or travels, the implicated serogroups are known, and suitable vaccines are commercially available. WSAVA says this means the vaccine is core in many but not all parts of the world. It gives South Australia as a place that has been studied carefully and where there is little to no evidence that canine leptospirosis occurs.

The guideline is just as direct about the second condition. A vaccine cannot be designated core if it is uncertain which vaccine should be given, and in many parts of the world it remains undetermined which serogroups would need to be included in local vaccines. WSAVA says that the development of “pan-protective” vaccines, which might protect against most known variants, should be eagerly awaited and, if successful, would substantially extend the regions where leptospirosis vaccines can be considered core.

On the vaccines themselves, WSAVA says there are monovalent, bivalent, trivalent and quadrivalent products. They variously contain serovars from the serogroups Icterohaemorrhagiae, Canicola, Grippotyphosa, Pomona and Australis, and quadrivalent vaccines provide broader protection. Merck likewise says vaccines are available for four of the most common types of leptospirosis in dogs, but they do not protect against all strains.

For the schedule, WSAVA’s table says the initial dose is usually from 8 weeks of age (follow the product leaflet), a second dose follows 2 to 4 weeks later, and a booster is given annually. Two doses of this kind of inactivated vaccine are needed to immunise: WSAVA says the first dose primes the immune system and the second immunises. If the second dose is not given within 6 weeks of the first, WSAVA says to assume the first gave no protection and start again with two doses 2 to 4 weeks apart. For a dog that was properly immunised but whose protection has lapsed, it likewise recommends starting again with two doses. An unvaccinated adult dog also needs two doses, then annual revaccination. Merck also says vaccination is usually recommended every year.

WSAVA’s 2015 report for Asia (Day and colleagues) adds two points. Its research recommendations say that groups should work together to determine the circulating serovars that are relevant in each country. Its answer to a question about vaccine choice says that including additional, locally important serovars or strains in a leptospirosis vaccine may lead to enhanced protection.

What did the Kerala study of dogs find?

The study was published in 2013 by Ambily and colleagues from the College of Veterinary and Animal Sciences, Mannuthy. The authors say that many places in South India, including Kerala, are known to be endemic for leptospirosis. They tested 205 dog blood samples from Thrissur, Kozhikode and Palakkad, collected between March 2011 and February 2012. The samples included 35 from healthy vaccinated dogs and 30 from healthy unvaccinated dogs; the rest were from dogs suspected of acute leptospirosis.

In total, 146 samples (71.12%) were positive on the microscopic agglutination test, which the authors call the gold standard test for diagnosis. They included the healthy vaccinated dogs; the healthy unvaccinated dogs were negative. The most common type was Autumnalis (36 samples), followed by Australis (28) and Pomona (20). The vaccinated dogs had antibodies to Canicola and Icterohaemorrhagiae, which the authors say are in the common commercial vaccine. Because 140 of the 205 samples came from suspected cases, the 71% figure describes this sample, not all dogs in Kerala.

The authors noted that an earlier Kerala study, in 2004, found Pomona the most common type, while later studies found Australis and Autumnalis. They concluded that, although the vaccines in Kerala then contained Icterohaemorrhagiae and Canicola, Autumnalis needed to be added, because immunity to leptospirosis is mostly specific to the type. They also pointed out that most earlier Kerala studies were confined to Thrissur district and called for a detailed study covering the whole state. In an area where vaccination is routine, they noted, antibody levels have to be higher to confirm acute infection, because healthy vaccinated animals also have antibodies. The authors added that dogs can act as a link between environmental reservoirs of infection and people.

What should I ask my vet about the vaccine?

These questions follow from the sources above.

• Which types does this vaccine contain? WSAVA says the serogroups in vaccines depend on the region.
• Do they include the types that cause disease where I live? WSAVA’s Asia report says locally important serovars in a vaccine may lead to enhanced protection.
• Does my dog need two doses 2 to 4 weeks apart, and when is the yearly booster due?
• What happens if a dose is late? WSAVA says that if the second dose is not given within 6 weeks of the first, the course should be started again with two doses 2 to 4 weeks apart.
• Is this part of a combined vaccine?

Frequently asked questions

Is the leptospirosis vaccine one of the usual puppy vaccines?

Not by default. WSAVA lists it as core only in regions that meet its three conditions; elsewhere it is a vaccine chosen with the vet. Its table says the first dose is usually from 8 weeks, with a second dose 2 to 4 weeks later.

How often does the vaccine need repeating?

WSAVA’s table says annually, and Merck says vaccination is usually recommended every year.

Does the vaccine protect against every type?

No. Merck says the vaccines do not protect against all strains, and WSAVA says protection depends on the serogroups a vaccine contains.

Can people catch leptospirosis from dogs?

Merck says the disease can affect almost all mammals, including people, and the CDC lists dogs among the animals that carry the bacteria. Contact with an infected animal’s urine or body fluids is one way people are infected, which is why Merck advises gloves and handwashing when caring for an infected dog.

Sources

• WSAVA Vaccination Guidelines Group (2024). 2024 WSAVA guidelines for the vaccination of dogs and cats. J Small Anim Pract 65(5):277-316. https://wsava.org/wp-content/uploads/2024/04/WSAVA-Vaccination-guidelines-2024.pdf
• Day MJ, Karkare U, Schultz RD, Squires R, Tsujimoto H (2015). Recommendations on vaccination for Asian small animal practitioners. J Small Anim Pract 56(2):77-95. https://pmc.ncbi.nlm.nih.gov/articles/PMC7166337/
• Ambily R, Mini M, Joseph S, Krishna SV, Abhinay G (2013). Canine leptospirosis: a seroprevalence study from Kerala, India. Veterinary World 6(1):42-44. https://doi.org/10.5455/vetworld.2013.42-44
• Merck Veterinary Manual, dog owners: leptospirosis in dogs. https://www.merckvetmanual.com/dog-owners/disorders-affecting-multiple-body-systems-of-dogs/leptospirosis-in-dogs
• US Centers for Disease Control and Prevention. About leptospirosis. https://www.cdc.gov/leptospirosis/about/index.html