There are a number of highly infectious and potentially fatal diseases which can affect your dog. There is no treatment for many of these diseases and young puppies that catch them often die. However, for many of these conditions there is a simple protection in the form of vaccination. Ensuring that your dog completes an initial course of vaccinations and then receives regular booster jabs is important if you want to keep your dog fit and healthy. If you are planning on taking your dog abroad with you it will also need to be vaccinated against rabies before you travel. Always discuss preventative healthcare with your vet as they will be best placed to advise you on your pet's individual needs.
There are other infectious diseases for which there is no vaccine. We are fortunate in the UK that most infectious diseases not covered by vaccinations are relatively mild. However, if you are taking your pet abroad you need to be aware that there are some nasty diseases like leishmaniosis and ehrlichiosis that your pet may be exposed to.
Many parasitic diseases also affect dogs and these can be picked up from apparently healthy animals (dogs, cats and wildlife) and preventative healthcare can be beneficial to protect your pet from fleas, lice, worms and ticks. Your vet will be able to advise you on what products you need to buy to keep your pet safe and healthy.