Rory Thomson BVMS MRCVS

The manufacturer of the majority of the dog vaccinations in the United Kingdom has taken the decision to discontinue the production of ‘Lepto 2’ or ‘L2’, a vaccination covering 2 strains (or serovars) of Leptospirosis in dogs in favour of the 4 strain vaccination ‘Lepto 4’ or ‘L4’, which contains 4 strains (or serovars)

Leptospirosis is a bacteria that can affect people as well as dogs, usually causing kidney or liver disease that can be fatal. The disease is usually carried and spread through water from rats and rodents carrying the disease.

There are over 300 serovars of leptospirosis spanning about 25 different serogroups. The serogroup tends to identify the reservoir species that the bacteria prefers to live in, however these strains can adapt and become more infectious to other species.  The more common and significant serogroups include Canicola (dogs), Icterohaemorrhagiae (rats), Grippotyphosa (small mammals such as voles, raccoons and skunks), Hardjo (cows).

Several decades ago, it was mainly the Canicola and Icterohaemorrhagiae strains that affected dogs, which is what is in the L2 vaccination.  With improved vaccination and bacteria adaptations other strains have started to become more prevalent as a cause of leptospirosis disease in dogs across the globe with Grippotyphosa increasing in prevalence (and is now reported to be the most common strain in some areas of North America, possibly due to the reservoir in the raccoon population).

There is currently no evidence that a leptospirosis vaccination strain will provide any cross protection to other leptospirosis strains.  It is speculated that the more strains of leptospirosis there are in a vaccination, the more likely it is to provide some cross reactivity, particularly within a serogroup.  Most of the data regarding leptospirosis prevalence is coming from North America and Europe and does not necessarily reflect the strains dogs in the United Kingdom are being exposed to.

There are challenges with the identification of which strain of Leptospirosis is causing disease in dogs. There has been an increase in the number of cases of Leptospirosis in the United Kingdom, some of which are in vaccinated dogs.  Although data is limited and the strains of leptospirosis vary geographically, the main serovars currently being identified are Icterohaemorrhagiae, Australis and Sejroe.  The L4 vaccination covers Canicola, Ictohaemorrhagiae, Grippotyphyosa and Australis (but does not cover Sejroe).

Although the L4 vaccination does provide a better coverage for the current strains of Leptospirosis, it does not cover all strains and the vaccination is more inconvenient to administer, with the license requiring a specific 4 week gap between first and second vaccination.  It also comes at an increased cost. With increased movement of pets globally and the changing prevalence of Leptospirosis strains, it is inevitable that at some point we are going to need to rethink our Leptospirosis vaccination strategy.  While I feel there is no strong evidence that the current L4 vaccination is going to make a massive difference to reducing the risk to dogs in the North East of England, the discontinuation of the L2 vaccination has made us have to reconsider our vaccination protocols and as such we will be providing the L4 vaccination routinely from January.  We will maintain a small supply of L2 while stocks last.

All dogs requiring an L2 booster vaccination will be offered the L4 upgrade, which will require a second vaccination 4 weeks later.  This second vaccination is sponsored by the pharmaceutical company and will be given free of charge in 2025.  If declined and a restart is required in a subsequent year to upgrade it will be charged as a re-start vaccination course.

All puppies will routinely be given L4 vaccinations.  A request for L2 can be made while stocks last, however due to the discontinuation of production of the main supplier of L2, the ongoing availability of L2 cannot be guaranteed and a future restart may be necessary.