Dog Illnesses

Dog illnesses can be fairly mild, or severe, even deadly. The often come with a variety of symptoms and outcomes, and a range of treatment options.

Yorkshire Terrier

On this page you'll find a list of symptoms most frequently seen in dogs who are sick, and information on common canine illnesses and diseases.

I've also included an article written exclusively for this website by veterinarian Dr. Megan Teiber, DVM.

In it, she shares tips on how to recognize the signs that your dog is ill, how veterinarians reach a diagnosis, and the best way to keep your dog healthy in the first place.

Symptoms of Common Dog Illnesses

There are a handful of symptoms which usually mean Fido isn't well. Some are physical signs and pretty obvious, others are more vague or subtle, and may be behavioral rather than physical.

Common symptoms of dog illnesses include:

  • Diarrhea
  • Vomiting
  • Loss of appetite
  • Lethargy or exhaustion
  • Runny nose
  • Cough
  • Sneezing
  • Fever (anything over 104F)
  • Eye discharge
  • Swollen lymph nodes
  • Skin inflammation/rash
  • Disorientation
  • Shaking or trembling
  • Convulsion
  • Behavioral changes (eg. panting, pacing, whining)

Let's take a look at what certain combinations of symptoms MIGHT mean for your dog...

Diarrhea - Vomiting - Lethargy - Fever

These four symptoms are found in many contagious dog illnesses, some of them very serious. If your puppy or dog is showing several, or all, of these signs,  he needs to be examined by your veterinarian asap.

Potential cause of these symptoms include illnesses such as:

Runny Nose - Eye Discharge - Fever - Cough

Another four symptoms of dog illness which are often seen in (sometimes serious) contagious diseases, including:

Being able to recognize signs of a medical emergency in your dog could save his life.

This isn't always easy, but this page will help you figure out whether or not Fido's symptom/s require an immediate vet visit ..... Dog Emergency Symptoms

Canine Illnesses & Diseases

There are obviously a LOT of different diseases and illnesses which can affect our dogs. Some (like the ones listed above and some of the ones below) are fairly common, others are more rare.

Poodle with diarrhea

All of them need to be diagnosed by a veterinarian so that you can make sure Fido gets the right treatment. The earlier you treat a problem the quicker it will be to resolve, and the less costly the treatment.

The symptoms you might see are obviously very varied because there are a significant number of different diseases.

Other symptoms of dog illnesses might include:

  • Itching
  • Hair loss
  • Inflamed or irritated skin
  • Excessive thirst
  • Loss of appetite
  • Increased appetite
  • Weight loss
  • Weight gain
  • Difficulty breathing
  • Bad breath
  • Lameness 
  • Loss of co-ordination

.... and more.

Contagious Dog Illnesses

Non-Contagious Dog Illnesses

Dog Illnesses - A Veterinarians' View

Signs that all is not well:

Some signs of disease in dogs, such as vomiting, diarrhea, coughing, limping, or itching are pretty obvious to all pet owners. Others can be more vague.  But no one knows your dog better than you.  If you notice subtle changes in your dog’s personality, appetite, and energy levels, it is worth a trip to your vet. 

Personality changes may not be the same for every dog---a dog who is normally at your side all day may suddenly be more elusive, and a dog who is normally aloof may be more clingy. A Labrador who normally chows down every meal and suddenly refuses breakfast is a big deal, while skipping a meal probably would not be concerning for a dog who routinely picks at his food. 

Other common signs of dog illnesses that are easily missed include increased water consumption or urination, unintended weight loss, panting, and restlessness at night. When in doubt about whether your dog is sick, err on the side of caution.  It is better to get a clean bill of health from the vet and breathe a sigh of relief, than to find out too late that a serious illness was brewing all along. 

Reaching a veterinary diagnosis:

When you bring your dog to the vet for an illness, we will perform a full physical exam.  Sometimes the problem is obvious based on exam findings.  However, there are many times the exam is normal or does not give the answers we need. This is especially true if the dog’s symptoms are nonspecific or vague.   

If a dog is limping, it is pretty obvious we need to look at the affected leg, and if he is itching we need to look at his skin.  But if he isn’t eating well or is just more lethargic than normal, it could be just about anything! Where do we start?  

First, we consider your dog’s signalment. This is the age, sex, and breed, and it helps narrow down the list of probable diagnoses. For example, if a young dog is vomiting, we first consider intestinal parasites, dietary issues, or foreign body intestinal obstruction.  If the dog is older, we may be more likely to consider liver disease, kidney failure or cancer as possibilities. 

The breed is also important, as some breeds are more prone to certain canine illnesses than others.  For example, German Shepherd Dogs are the poster children for pancreatic insufficiency.  If they come to me for ongoing diarrhea and weight loss, it I would test for this disease early.  If the dog was a Chihuahua, I would consider this disease less likely and not pursue the testing right away. 

The next thing we’ll do is get a good history. It is important that the person who knows the dog best is the one that brings him to the vet.  We want to know your dog’s regular diet, if he’s on any medications, if he got into anything he shouldn’t have, if he’s been around other dogs, his vaccination history, if he’s had this problem before, and how long the symptoms have been happening. The answers to these questions may influence what diagnostic testing we recommend. 

Let’s take vomiting, for example.... if a young dog is vomiting very frequently for the last 2 days and has a history of eating socks, I would be likely recommend x-rays to look for intestinal obstruction.  If he’s older, vomiting on and off for a few weeks, and gradually losing weight, I’d be more likely to recommend bloodwork to check his organ function.  Of course, not every dog follows the rules, but these are good starting points.  

After considering exam findings, signalment, and history, we select the most reasonable diagnostic tests to recommend.  If your dog is severely ill, we may conduct multiple tests right away to get to the bottom of the problem as quickly as possible. 

If the symptoms are more mild or chronic, we may start with one test and take things step by step.  Sometimes, despite our best efforts, we don’t reach a definitive diagnosis. Tests can be normal or inconclusive, or they may be declined by pet owners due to cost or feasibility.  In these cases, we usually suggest supportive treatment.  This may mean fluids, anti-nausea medications, or pain medications to help your dog feel better even though we aren’t sure exactly what’s going on.  Sometimes this solves the problem.  If it doesn’t, we need to be more aggressive in our diagnostic testing.

Prevention Tips:

Lastly, there are things you can do as pet owners to prevent dog illnesses, or at least catch them early. The first is to keep your pet vaccinated.  Rabies and Distemper/Hepatitis/Parvovirus vaccines are considered ‘core’ by AAHA (the American Animal Hospital Association) and should be administered to all dogs.  Puppies may need several boosters, while adult dogs can receive vaccines spaced out based on your veterinarian’s recommendations or the laws in your state. 

Leptospirosis and Bordetella (kennel cough) vaccination is also recommended by most veterinarians but may be based on your dog’s lifestyle.  Lyme disease is becoming more common as ticks are more widespread, and many vets are now recommending the Lyme vaccine based on your location.  Canine influenza is another emerging disease and vaccines are recommended for at-risk dogs. 

You can also prevent disease by administering regular heartworm prevention and yearly heartworm tests.  An ounce of prevention is worth a pound of cure---the current preventatives are very safe and heartworm treatment is complex, risky, and expensive. 

The same goes for flea and tick prevention.  Keeping your dog free of fleas and ticks is much easier than battling a flea infestation or treating a tick-borne illness---your dog will thank you for it! 

Lastly, keep up with regular physical exams at your vet’s office.  Remember that dogs age faster than humans, and if they are examined less than 1-2 times per year, we risk missing the warning signs that something is amiss.  As dogs age, it is also recommended to check bloodwork regularly to monitor for organ function.

There are some diseases which are simply not preventable, but by keeping up with regular health checks, we can at least catch things early and intervene before your dog becomes severely ill.

Author: Dr. Megan Teiber, DVM

More About Dog Diseases

As yet there are not individual pages covering all the dog illnesses and conditions listed above. To make sure you have basic information on the majority of them I've included a very quick look at some of the others below:

Veterinarian examining tiny pitbull puppy


Leptospirosis bacterial disease affecting the urinary system, including liver and kidneys. Mainly transmitted through infected urine. It is possible for dogs to transmit Leptospirosis to human family members.

Symptoms:  include loss of appetite, vomiting, lethargy, fever. More advanced symptoms include jaundice, increased thirst and dehydration due to frequent urination. 

Treatment:  early antibiotic treatment can lessen the severity and/or duration of this illness.


A highly infectious viral infection of the respiratory system. Easy airborne transmission through coughing and sneezing. 

Symptoms:  include a runny nose, cough and fever.

Treatment:  is mostly supportive, with antibiotics being given for secondary infections.


Leptospirosis bacterial disease affecting the urinary system, including liver and kidneys. Mainly transmitted through infected urine. It is possible for dogs to transmit Leptospirosis to human family members.

Symptoms:  include loss of appetite, vomiting, lethargy, fever. More advanced symptoms include jaundice, increased thirst and dehydration due to frequent urination. 

Treatment:  early antibiotic treatment can lessen the severity and/or duration of this illness.


One of the most well-known dog illnesses.

A severe and usually fatal viral disease that affects the brain and nervous system. Transmitted through saliva. Once symptoms appear this illness is always fatal to both dogs and humans. 

Symptoms:  are behavioral and usually include unusual, irrational and frenzied aggression (if your dog was very shy you may see a increased affection or acute shyness if previously friendly). You may also see lack of co-ordination, seizures and the classic foaming at the mouth.

Treatment:  There is no treatment for Rabies and the disease is always fatal.

Canine Hepatitis

Highly contagious viral disease which affects the liver.

Starts in tonsils, spreads to lymph nodes, bloodstream and liver. Can be transmitted through urine, feces and saliva. 

Symptoms:  are similar to Distemper. Severe cases can progress rapidly and cause sudden death.

Treatment:  is supportive care which may include IV fluids and medications.

Puppy Strangles

Also known as Juvenile Cellulitis, Puppy Pyoderma, Sterile Granulomatous Dermatitis or Lymphadenitis.

Luckily it's not a very common condition.

An autoimmune disease which usually appears suddenly in puppies under 4 months of age. May have a hereditary component as some breeds are predisposed to developing it.

It needs to be treated quickly to avoid serious, or fatal, consequences.

Symptoms of Puppy Strangles:

These start off with generalized swelling of the puppy's face, but the most noticeable symptom is extreme swelling of the lymph nodes under the jaw and around the neck.

As this progresses it looks as though the puppy is being 'strangled' by the swelling, hence the name. Painful pimples and pustules then develop over the head/muzzle/ears.

Swelling might occur in other lymph nodes and joints, pustules may spread across the body, plus a puppy could lose his appetite and/or have a fever.

Treatment of Puppy Strangles:

Treatment usually consists of corticosteroids to reduce the swelling and inflammation, and antibiotics to kill off any secondary infection that has set up in the affected areas.

If your pup has a severe case, other treatments might be needed, or the standard treatment may need to be maintained for a longer period.


'Pano' is a condition that is most often seen in medium, large or giant breed puppies.

It's basically inflammation of the bones, usually in the front legs and it affects puppies between 6 and 18 months old.

It's a self-limiting disease which means that the majority of puppies will grow out of it without any treatment and without lasting side effects.

Symptoms of Pano in puppies:

Usually a puppy with Panosteitis will have some pain in his legs, and will limp intermittently.

It's usually worse in the morning, after rest, or at the beginning of a walk or play session. Then the puppy 'walks it off' and seems fine.

Usually a pup will suffer on and off for 3 - 6 months and then recover. Occasionally it can be longer.

Occasionally a pup will have a fever, seem lethargic or lose his appetite as well. If this happens he needs to be seen by a vet because treatment might be needed.

Treating Pano in puppies:

Most puppies recover fully without treatment and Pano is just a nuisance, but if your pup has a lot of pain or other symptoms then your vet might prescribe corticosteroids or other anti-inflammatory medications to help him feel better.

Vizsla dog with stethoscope

Health Alert. New Canine Virus Update

There appears to be a livestock virus which has mutated to the point where has the potential to be a risk to our dogs.

The virus is called CIRCOVIRUS and the main symptoms are bloody diarrhea, vomiting, lethargy, weakness & loss of appetite.

Other symptoms of Circovirus can include vasculitis, rapid heart rate and fluid on the lungs.

Quick diagnosis and prompt treatment give your dog the best chance of survival, so don't hesitate to push for an accurate diagnosis.

Prevention Is Key!

Having a sick pup is worrying, and getting him the care he needs to get better may be very expensive, so it makes sense to try to prevent your little guy or girl from getting sick in the first place.

Veterinarian with healthy terrier pup

Also, no matter what the subject, I always think that a good reference book is worth it's weight in gold, and this is certainly true when you're talking about dog illnesses and other canine health issues.

Here are a few of the best dog health books available, you'll feel better if you have at least one of them on your bookshelf....

All the information and advice on this page has been approved by
Veterinarian, Dr. Megan Teiber, DVM

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