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Vaccination for leptospirosis: is the vaccin more lethal than the disease?

mer, 07/31/2019 - 12:57

Leptospirosis is known as a core vaccine for many dogs all over the world. They receive their annual jab to protect them against a few serovars of leptospirosis for the next months. The leptospirosis vaccine has been a matter of discussion for ages, as it is a vaccination against a bacterial disease. The effectivity of vaccinations against bacterial diseases have been questioned for a long time. Even though it has had positive effects in some cases, it doesn’t seem to be the solution in all cases. However, with the release of the new L4 vaccine, named after the 4 serovars it protects against, the commotion around the vaccine was raised to a new level. The vaccine was linked to the death of many dogs worldwide and the media has now jumped on the subject. Here’s a summary on the entire issue.

The previous leptospirosis vaccine, the L2, protected dogs against two serovars: L. ichterohaermorrhagicae and L. Canicola. These are the two most common serovars in Europe. However, these are just 2 of a total of more than 200 serovars who cause leptospirosis. The most common leptospirosis infection in dogs is Weil’s disease, which causes apathy, fever, joint aches and nausea. At a later stage this disease causes damage to internal organs such as the liver and kidneys. This damage is often irreversible and can lead to death when left untreated. This can be prevented by a timely diagnosis and treatment of the disease. Leptospirosis can be treated with antibiotics and has a good prognosis when it is caught and treated early. Weil’s disease is a zoonosis which means humans can be infected through animals and get sick as well. In humans this disease is also treatable with antibiotics and has a good prognosis, unless the diagnose and treatment comes too late, in which case it can be deadly.
As the name suggests, L4 protects against 4 serovars. Apart from the two in L2 it also protects against Leptospira Australis (Bratislava) and Leptospira Grippotyphosa. This should result in better protection but unfortunately side effects were mentioned within months, and some were very severe. The side effects vary from mild symptoms like swelling and mild lethargy to severe things like meningitis, epileptic insults and damage to organs.

Since 2014 about 2000 cases were reported and 120 of them had fatal endings. The Veterinary Medicines Directorate, part of the British Government, set up research after the vaccine but up to today are unwilling to publically report about the number of victims, nor about whether or not the vaccine will be withdrawn from the market. VMD did research 292 cases of severe side effects with often deadly ending. This research mainly covered dogs from England, but also several from other European countries amongst which were the Netherlands, Belgium, France, Spain and Switzerland. The cases were on both individual dogs and on complete litters in which several showed (severe) side effects. Every case was looked at thoroughly and general health, age, health history and treatment were checked. In a large number of cases the information turned out to be too incomplete to be able to draw a proper conclusion. In a small number of cases a separate reason was found to be present, thus making the side effect highly unlikely. In 53 cases was found it to be possible the problems were caused by the vaccine. This group of dogs contained a large variety in age and breed. Apart from some very young pups who probably fell ill after the first vaccinations, also adult and senior dogs were reported. Both mutts and pedigree dogs were in this group. The problems described would vary from sudden illness and death to prolonged illness and eventual choice of euthanasia.

The rumours about the vaccine are quickly shared through social media and also reach national and international press. Both Daily Mail and Telegraph (UK) mention the risks of this vaccine in early July. Examples of diseased dogs are mentioned and specialists are interviewed. Both papers mention how WSAVA (World Small Animal Veterinary Association) warned about the vaccine. Supposedly they advise to never vaccinate with Nobivac’s L4 pups under the age of 12 weeks. However, WSAVA publically denies ever having stated this. On their website is published the article was based on incomplete research of the journalists in question.

They also state to never recommend vaccines of any brand. They point at the WSAVA regulations (latest renewal 2015). Those regulations clearly say Leptospiroses vaccine is not in the standard vaccination schedule and per individual chances for contamination should be considered. Amongst other things these chances depend on both habits of the dog and the habitat it lives in. Leptospiroris flourished especially well in tropical areas and prefers stagnant waters. Rats and mice also are a risk where contamination in concerned. This makes dogs that hunt and/or swim a lot more vulnerable. WSAVA advise to estimate chances per year and per habitat and to only vaccinate when a proven high risk is present. WSAVA also advice to advice per individual in order to know whether L2 or L4 would be more appropriate. Such an advice needs information regarding the environment the dog in question lives in so the serotypes present can be identified. This means a general advice on which type vaccination to use is impossible to give without further information.

The recent developments show how hard it is to separate facts from rumours. About the true risks of this vaccine nothing was revealed so far. What is known are the common facts for every vaccine against bacterial diseases: the vaccine contains of so-called dead pathogen, an inactivated part of the disease the vaccine is meant for. This pathogen does not have the ability to activate the immune system by itself in order to build resistance against the disease. To realize this an additive is needed, a so-called adjuvant.

In Nobivac L4 vaccine this adjuvant is thiomersal. Almost 50% of thiomersal consists of mercury. It created a lot of fuss when used in humane vaccines and was said to be linked to development of ADHD and autism after vaccination. A lot of research was done and amongst other things it turned out thiomersal is not as toxic as many other mercury compounds that for instance are known in environmental pollution.
Still this remedy is contentious and a number of countries banned it from use in humane vaccines. Although not illegal in the Netherlands one seems to strive for as many thiomersal-free vaccines as possible so the matter if only used if no other options are available. Whether or not thiomersal is one of the reasons L4 seems to give so many side-effects and which consequences this may have only time will tell.