Vaccinate - protect your pet

James Hill MA, VetMB, MRCVS, Fromus

Vaccination, do the benefits outweigh the risks? A commonly asked question, with a simple answer – yes, clearly.

Until the advent of vaccines, infectious diseases killed large numbers of pets each year. Consequently, vaccination became one of the greatest success stories in veterinary medicine.

Despite the fact that pet owners are not legally obliged to vaccinate, the moral obligation to protect pets from preventable disease is unavoidable and in light of the significant health benefits and protection from serious diseases that vaccination offers, we vets advocate vaccination.

Undoubtedly, vaccination has dramatically reduced the frequency of the majority of infectious diseases that affect our pets and as a result, these infectious diseases are far less prevalent in the UK. However, complacency amongst pet owners and failure to maintain vaccination could quite easily result in widespread outbreaks of disease among our dog population.

Today, focussing on leptospirosis, I examine the necessity of vaccination and its potential impact on an animal’s health.

Leptospirosis: the low-down
Canine leptospirosis can be contracted indirectly from the environment – a waterway, marshy land, a ditch or even a puddle - or directly from unprotected, infected dogs. The disease is highly contagious and an infected dog can become seriously ill very quickly. The disease can also infect people, which means an infected dog is a real risk to the owner and attending veterinary staff. The disease has an exceedingly high mortality rate and even cases that receive the very best veterinary care are likely to die after two or three days, following presentation. Therefore, if your pet’s vaccinations are not kept up-to-date, any dog can be at serious risk of contracting this potentially fatal disease.

Leptospirosis develops from bacteria transferred via the urine of an infected animal. After ingestion of the bacterium, the disease enters the bloodstream via the mucous membranes, such as the nose or mouth and this is followed by rapid replication of the bacterium in several tissues such as the kidney, liver and spleen. The bacterium is then excreted via the animal’s urine back into the environment ready to infect another animal. This puts every dog at risk and, as such, it is crucial that pets are protected through annual vaccination.

The UK has two commonly seen forms of the disease: Leptospira canicola and Leptospira icterohaemorrhagiae (Weil’s disease is the human equivalent).

Leptospira canicola has the dog as the main carrier of disease. This form of disease primarily affects the kidneys and clinical signs can vary from mild and non-specific, to kidney failure or sudden death. Should a dog escape death, it can become a carrier of the disease and shed the bacterium into the environment through their urine. Infected dogs may continue to excrete organisms leading to repeated contamination of the environment and in damp conditions, the bacterium may survive weeks or even months. In Europe, the prevalence of Leptospira canicola has declined. This can be explained by the fact that the dog is the natural reservoir for canicola and widespread routine vaccination has reduced the shedding of such strains from vaccinated animals.

Leptospira icterohaemorrhagiae has the rodent as the main carrier of the disease. Transmission to dogs is either directly via contact with infected urine, or indirectly via contact with contaminated water, such as drinking from ditches or swimming in canals and rivers inhabited by infected rats. The symptoms can vary from mild non-specific signs such as lethargy and depression, to more severe signs such as abdominal pain, jaundice, vomiting, haemorrhagic diarrhoea, liver damage and death. Dogs that have been infected may go on to become carriers of the disease, shedding the bacterium into the environment in their urine. These animals may be infected long-term and pose a real threat not only to other dogs, but also to humans.

Humans: what are the risks?
Clearly, Leptospira icterohaemorrhagiae, which is carried by rats, is the most significant in terms of human health in the UK. Leptospirosis is a serious zoonotic disease, which means it can be transmitted to humans who come into contact with infected animals or contaminated water.

The human form of leptospirosis is known as Weil’s disease. It is not an uncommon disease, in fact, in the current climate rats are thriving in both rural and urban areas and environmental contamination is commonplace. Infection occurs through skin contact, dirty hands, water bowls etc. Once contracted, Weil’s disease has horrific health consequences, leading to kidney and liver failure and affecting the blood’s ability to clot.

Symptoms: what to expect
Clinical signs of acute and severe cases of the disease in dogs are obvious, including high temperature, severe thirst, depression, lethargy, abdominal pain, vomiting, bloody diarrhoea and jaundice. In practice, I see several cases of this severity per year – enough to keep me regularly vaccinating my dog.

Leptospirosis: a case in point
One remarkably heartbreaking case comes to mind when considering the issue of vaccination. A Labrador was recently admitted to my surgery in a very bad way and displaying the classic symptoms of severe leptospirosis. As  working dog, he was extremely likely to come into contact with leptospirosis, as his work often entailed the retrieval of birds from numerous watery environments. Unfortunately, despite extensive, intense medical treatment, the disease proved too overwhelming and the poor dog died just two days after admittance to hospital.

Unfortunately, he was unvaccinated. When quizzed on this issue, his owner admitted that he had not vaccinated his dog due to worries about possible side effects and he “didn’t believe in vaccination”. Sadly, had he been more educated about the dangers of non-vaccination and vaccinated his dog, this preventable tragedy would not have occurred.

On a positive note and lessening the futility of the situation, as a consequence of this dog’s death, many of the unvaccinated working dogs in the community were brought in for vaccination as news of the disaster spread.

Vaccination: prevention is key
I am a keen proponent of annual vaccination, not only because it enables vets to immunise dogs and protect them against disease, but also because it provides us with the opportunity to conduct a thorough health check on a yearly basis. If you wait for a health problem to come to you, it can be more difficult or even impossible to treat. Therefore, by doing an annual ‘pet service’, potential health issues can be detected at an early stage and dealt with before they pose a more serious threat. It is incumbent upon vets to meticulously assess an animal’s health at the time of vaccination in order to service health needs adequately and protect them from prospective illness.

In the UK, Leptospirosis is due to two strains, whilst in the USA, there are several strains reported to cause the disease in dogs. As a result, UK vaccines only contain the two strains of the disease that they are likely to encounter - Leptospira canicola and Leptospira icterohaemorrhagiae.

Leptospira icterohaemorrhagiae can exist wherever there is water and infected rodents, so, whether in the country or the city, a dog is at risk. This refutes claims by some American experts that vaccination should only occur in areas of particular risk, because everywhere is potentially an area of risk.

One only needs to refer to the increasing need for pest control to realise that the rodent population is booming, providing a huge reservoir for infection. In the UK, a leading animal health company offers the only high antigenic mass vaccine on the market to provide both 12 months duration of immunity against Leptospirosis, but also reduction of renal shedding. It is highly effective and routine annual vaccination will protect dogs from the disease, whilst ensuring that those not displaying clinical symptoms cannot shed the organism into the environment. As a result, dogs, along with their owners, are protected from infection.

So, having illustrated the need for vaccination in order to prevent infection for the disease, we must now consider the question of whether vaccinations cause more illness than they prevent?

Whilst serious adverse reactions are exceptionally rare, it is possible (whether the vaccine is for human or animal use) for some unwarranted effects to arise at a very low level. Pet vaccines are tested thoroughly for both safety and efficacy and this has been confirmed by an independent epidemiological study involving almost 4,000 dogs. The study, undertaken by the Animal Health Trust, showed there was no evidence to suggest that dogs suffered any increased level of illness after vaccination.

In nearly 20 years of practice, I have not seen a fatality directly attributed to vaccination, but I have witnessed many deaths due to disease. People should fear the disease, not the vaccine and we have to address the fear that vaccinating your pet is putting them at equal risk of death as the disease itself. Leptospirosis is a preventable disease, but if an animal is unfortunate enough to contract it, they are more than likely to die in horrific circumstances.

Leptospirosis: The outlook
In order for your pet, and the dog population as a whole, to remain free of leptospirosis, along with other infectious diseases, pet owners must maintain annual vaccination. There is no reason to take a risk with such a nasty disease when there are the means by which to prevent it.

Undertake a balanced risk assessment of the situation – the risk from vaccines is miniscule, yet the risk from the disease is high – and the argument in support of vaccination is undeniable. By failing to vaccinate your pet, you are failing to act in their best interest.