Why are they important? Your dog is constantly at risk of contracting a potentially deadly disease. Distemper, Parvovirus, Infectious Canine Hepatitis - they haven't gone away, they're still out there. The reason we don't see them as commonly as we used to is that most dogs are vaccinated to protect them; without vaccination, any dog is at risk. There are also some rarer or less severe diseases we can vaccinate against - such as Kennel Cough and Leishmania. Vaccination is a very low risk way to protect your dog - and the other dogs around you - and we strongly recommend it!
What are vaccines? Most vets now offer a wide range of vaccines against different diseases, and we'll look at each of the more important ones in turn. Vaccines work by "teaching" the immune system how to fight a particular infection. They do not "weaken" or "strengthen" it, but they do make it better able to fight particular diseases. Some vaccines (like the Parvo Vaccine) contain a weakened but still live form of the disease agent - these often give longer lasting immunity (3 years) compared with those containing inactivated or dead organisms (like Leptospirosis, which only lasts a year or so). It's also important to remember that, unlike in humans, vaccines for dogs do NOT last for life - the manufacturer's recommended repeat dose dates are based on the time interval that will protect 99% of dogs vaccinated. It is true that some dogs' immunity does last longer, and for some disease, you can do antibody tests to see if the levels of antibody are still high. However, for most disease (especially Lepto, for example), this test is unreliable because the vaccine does not produce protection using antibodies but other components of the immune system. Fortunately, there is very little evidence of any significant risk to healthy dogs from vaccines - "over-vaccination" is a theoretical rather than a real risk.
(1) Distemper This is a very serious disease that, although closely related to measles, is much more dangerous. It is estimated that 50% of unvaccinated dogs who are infected will die, even with treatment. Typically, it causes a runny nose and eyes, vomiting and diarrhoea, pneumonia, seizures or fits, hardening of the footpads and ultimately death. Even in dogs who recover, encephalitis (causing dementia or fits) may occur as a result months or even years later. The vaccine requires 2 doses 2-4 weeks apart, then a booster a year later. It is repeated every three years.
(2) Infectious Canine Hepatitis ICH is caused by a canine adenovirus that attacks the liver. Infected dogs become severely jaundiced, have a high fever and lose their appetite; in severe cases, bleeding, fits and death may occur within hours. Even after recovery, infected dogs will often excrete the virus in their urine for many months. The vaccine requires 2 doses 2-4 weeks apart, then a booster a year later. It is repeated every three years.
(3) Parvovirus Also known as "Parvo", this virus is probably the most commonly seen fatal infection in dogs. Although vaccination is very effective, puppies face a short gap of vulnerability after their mother's immunity wears off and before their vaccines kick in - this is why it is vital to keep as many dogs as possible vaccinated to minimise the risk of transmission! Older dogs can also develop Parvo too, though - it's not just a disease of puppies. They virus attacks the intestines causing vomiting, diarrhoea and then severe, bloody diarrhoea, dehydration, septicaemia, shock and death. Even with intensive care nursing and treatment, at least 30% (and often more) will usually die. The vaccine requires 2 doses 2-4 weeks apart, then a booster a year later. It is repeated every three years.
(4) Leptospirosis Also known as Weil's Disease, this is caused by a group of bacteria that are transmitted in urine (from rats, dogs and cattle). It can also infect people, and it is able to invade the body even through intact skin. It damages the kidneys and the liver, and in severe cases may be fatal. There are a wide range of different "serovars" or strains of the bacterium; traditional vaccines are available against 2 of these strains, but some newer vaccines will protect against 4. The older vaccine needs only 2 doses, 2-4 weeks apart, and then an annual booster. The newer (L4) vaccine requires 3 doses, 2 weeks apart in a puppy, and then annual boosters. The vaccine DOES NOT last more than a year, and CANNOT be tested with "titre tests".
(5) Kennel Cough The two most important causes of Kennel Cough are Parainfluenza and the bacterium Bordetella bronchiseptica. The symptoms are a honking cough, which may persist for months, and often a low fever, lethargy and loss of appetite; however, in severe cases, pneumonia may occur which can even be fatal, especially in very young or very old dogs. There is an injectable vaccine against Parainfluenza (which can be given along with the Lepto vaccines), but it's effectiveness is limited. The full Kennel Cough vaccine is given up the nose and gives protection against both types. Vaccinated dogs do sometimes develop kennel cough (it isn't a perfect protection), but it is milder and much, much less infectious than if they had been infected without the benefit of vaccination. For maximal protection, the dog requires one dose annually.
(6) Rabies Although not (yet) present in the UK, rabies is a highly dangerous disease which can infect any mammal, including humans. Once symptoms occur, the disease is almost 100% fatal. Any dog wanting to visit mainland Europe (or most other non-UK countries) MUST be fully vaccinated before they leave. Infected dogs usually become hyperaggresive and will run around biting people and frothing at the mouth (the virus is transmitted in the saliva) before having seizures and dying. There is no treatment, and infected dogs must be put down to prevent their suffering and to protect the public. The vaccine requires a single injection (no requirement for blood tests any more) and must be repeated every 3 years.
(7) Leishmaniasis This is a fairly exotic disease, not yet native to the UK. We do, however, see it in dogs that have returned to the UK from southern Europe, where it is fairly common. It is spread primarily by sand-fly bites, although direct dog-dog transmission can also occur. Leishmania usually causes a scaly, scabby skin lesion, which gradually spreads; however, it can also cause severe internal damage as the parasites attack the gut (causing vomiting and diarrhoea), the muscles (causing muscle pain and lethargy) and the kidneys (causing increased drinking and urination). Most dogs will also suffer weight loss, and although the disease can be managed, it cannot be 100% cured. The vaccine requires 3 injections, 3 weeks apart under the skin and boosted annually for at-risk dogs.
In conclusion... Vaccination will reduce the chance that your dog contracts the disease, the severity if they do contract it, and the risk of them spreading it. Not all dogs can be vaccinated effectively (for example, dogs on certain medications won't respond properly to vaccines), so you are protecting these dogs as well as your own by vaccinating. If you want to know more about a particular disease or vaccine, give your vet a call!