When looking at the most deadly dog diseases, there is a difference to what we see in countries with high vaccination rates compared to what affects the worldwide canine population, says veterinary surgeon Graham Lewis.
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This highlights the advantage of having readily available vaccinations and a population with a high vaccination rate and shows how lucky we are in the UK.
Some of the disease and issues below can affect the human population as well and demonstrates the vital importance of a One Health approach across human medicine, veterinary medicine and the health of our environment.
Deadliest dog diseases
Cancer
Neoplasia means the presence of new, abnormal tissue and is the medical term for cancers. Unfortunately we are all familiar with cancer and the devastating effects it can have and, like humans, dogs are prone to a variety of different neoplasias.
Some neoplasias are fairly benign. For example, cocker spaniels are prone to wart-like skin growths and labradors get fatty lumps called lipomas. However, it is common for more malignant neoplasias to affect dogs as well and these can spread rapidly and often can become fatal.
With advancements in veterinary medicine and the common spread of vaccinations, neoplastic diseases are the most common cause of death that we see in practice in the UK.
Parvovirus
Parvovirus is a particularly nasty virus that is highly contagious and still fairly common in the UK. It can be fatal and commonly affects young puppies. We will commonly see it spread through an entire litter and it causes severe bloody diarrhoea, vomiting and fever. It can be rapidly fatal in young puppies and intensive care is needed to try to treat this deadly virus.
Luckily there are vaccines available to protect against parvovirus, with the first given between six and eight weeks and a second needed two to four weeks later. A third vaccination is recommended in some breeds that seem particularly at risk. It can also affect unvaccinated adult dogs – after the initial course, a vaccination every three years helps protect your dog and reduces the risk to other dogs in the area.
Leptospirosis
In dogs, leptospirosis is a condition caused by a bacteria that is spread through urine and can live in the soil or water for months, before entering the body via the mouth or any cuts or wounds. It can also affect people (known as Weil’s disease), although luckily this is rare. But if your dog gets the condition, there is a risk to you too.
Leptospirosis affects the liver and kidneys and the symptoms are due to these organs failing. Vomiting, diarrhoea, jaundice (yellow colour to gums), lethargy, drinking more and loss of appetite are all common. Unfortunately death can occur within two days of showing symptoms.
Some dogs can carry the bacteria without showing symptoms, posing a risk to other dogs and the people around them.
Leptospirosis can be controlled by vaccination, with annual vaccination boosters important for this condition. With the rise in vaccination rates in the UK, we see this a lot less commonly, however it is still a condition we see from time to time.
Rabies
Rabies is an invariably fatal disease caused by a virus that is a very real risk to humans too. 59,000 people are estimated to die from rabies annually, with the vast majority getting rabies from a bite or scratch from an affected dog.
Dogs contract rabies from a bite or scratch as well and initially have a high temperature and can be more vocal. As the disease progresses it can take two forms: furious rabies is the kind we are most familiar with, they become aggressive, eat anything and are very restless. But there is also a dumb rabies where they become quiet, drool excessively and have difficulty swallowing. In both cases, the disease is fatal and euthanasia is the kindest option.
The UK has been rabies-free for over 100 years, however many parts of the world still struggle to control this virus. Vaccinations can help stop the spread and anybody that has taken their pet abroad will be aware of the requirement to have a three-yearly rabies vaccination for their dog.
Distemper
Another nasty virus is distemper. This one, like rabies, affects the central nervous system but can also affect several other body systems and organs leading to a wide range of symptoms. Fever, discharge from the eyes and nose, tremors, hardening of the pads and paralysis can all be seen and it can be fatal. It is very contagious, can be spread in the air and survive in the environment which makes it a risk to many dogs in the world.
With a good vaccination program in place, this disease can be controlled and has just about been eradicated in the UK. I’ve only ever seen one case, and that was while travelling in Thailand. Treatment cannot kill the virus, but symptomatic treatment can help animals potentially survive.
A three-yearly vaccine for adult dogs (and the primary course for puppies) helps prevent the risk to your pet.
Heartworm
Heartworm (dirofilaria immitis) is a parasite that is spread by mosquitos - one of the deadliest insects in the world – and one of the deadliest animals. The larvae develop in the mosquito, are transmitted into the dog's blood when the mosquito bites and they migrate to the heart and large blood vessels to mature. They can stay there and reproduce for many years and it can take a long time for clinical signs to develop. Unfortunately by this stage, the disease is often well advanced.
They cause scarring of the heart and blood vessels eventually leading to signs of heart failure. They can also sometimes cause problems with the liver or the kidneys, depending on where the worms are in the circulatory system.
Treatment is possible but the damage caused by adult worms is often irreversible. Prevention via mosquito control and regular heartworm preventative wormers is the best option in endemic areas.
In the UK, we are lucky this is not currently an area the parasite can live as it needs year-round warmer temperatures. But with global warming there is a risk this parasite could start to make itself at home in the UK!
Multi-resistant bacteria
This might also be described as superbugs, or you might be familiar with terms like MRSA, but while cases of these are currently low numbers, they represent a growing risk and have the potential to threaten both pets and humans to the levels of some of the deadly diseases mentioned above. Without antimicrobials that work, simple infections have the potential to get rapidly out of hand and become fatal.
Diseases like tuberculosis used to be common in people and any surgery carried a high risk of incurable infection. We may return to those days in the future but hopefully remedies such as blood-letting or ‘fresh air’ won’t become common practice in the doctors or the vets!
The risk of multi-resistant bacteria is why we are more careful than ever when it comes to prescribing antibiotics and we try to only use them in suitable cases. Often swabs are taken to see what bacteria is present and to find out what antibiotics will work best in that situation. I hope pet owners understand why these steps are necessary sometimes for the greater good, as well as ensuring their own pet gets the best treatment.
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