Common Dog Diseases, Explained

Some illnesses to watch out for to keep your best friend safe.

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Dog Diseases

“I wish my dog could talk to me, even just for a minute.”

If you’re a dog owner, you’ve most likely had this thought at least once. Maybe the thought only entered your brain because you wanted to know if your pup truly enjoys the food you feed them, or whether or not they think that boujee Casper dog mattress was worth the $200 you spent. 

Or, maybe you’ve had this thought when you could kind of tell your dog wasn’t feeling well, and you desperately wanted to understand what was wrong. Dogs tend to hide any signs of discomfort, so it can be especially difficult to know when something might be amiss. (Not every ailment is as easy to spot as cherry eye, for instance.) Which is why, as a pet owner, it’s important to understand and recognize symptoms of common infectious diseases, viruses, or illnesses that your BFF may contract. 

sick dog

You also have to keep your own health in mind. Salmonella, brucella, campylobacteriosis, ringworm, roundworm, Mange, MRSA, hookworm, tapeworm… these are all diseases, viruses, or skin infections that your pup could inadvertently pass onto you through direct contact with bodily fluids. Simple handwashing is essential (as if we need to remind you of that in 2020). 

Let’s go through a few of the most common diseases, their symptoms, how they’re contracted, treatment options, and what you can do to prevent them. We’re not gonna lie to you–things might get morbid, or sad, or gross… but if your dog could talk, they’d definitely thank you later. Also, just an FYI: If you sign up for pet health insurance before your pet shows symptoms of these diseases, treatment would likely be covered, as they wouldn’t be considered pre-existing conditions.)

If you’d like to skip ahead, here are some of the topics we’ll cover:

Common diseases



Canine distemper

Kennel cough

Kidney disease


Lyme disease





Canine herpesvirus

Questions you might have

What diseases can be fatal for dogs?

What disease might kill a dog within 2 days?

Can dogs get STDs?


You may have heard your vet refer to this as simply “parvo,” which almost sounds deceptively cute. But, believe us–it’s not. 

Canine parvovirus is a highly contagious viral disease that attacks your dog’s intestines, which will typically lead to severe dehydration. It’s commonly spread when a dog comes into contact with the infected fecal matter of another dog who had parvo, but can also be easily spread simply from dog-to-dog contact. 

The common symptoms of parvovirus would be hard to miss–vomiting, diarrhea, loss of appetite, weight loss, dehydration, fever, and lethargy. So if your pup has one or more of these symptoms, your best bet would be to contact your vet ASAP, because canine parvovirus can be fatal.

Parvo treatment can also be a bit intense. Your vet would likely administer intravenous fluids and antibiotics. Treatment may also include balancing your dog’s blood sugar, intravenous electrolytes, intravenous nourishment, and an antiemetic injection to reduce nausea and vomiting. Your pup might also be required to stay in an isolation ward at your local vet hospital for a few days if the case is severe enough. 

The virus can survive in certain environments for years after exposure. So if you know your dog’s been infected, it’ll be a good idea to sanitize things like bedding and carpets. It may even be necessary to bleach your yard!

With all that said, it’s also important to remember that the mortality rate for parvovirus is actually pretty low, and since the vaccine is super effective, it’s an easy virus to avoid. Just be sure your pup is vaccinated, and avoid letting them hang out with any unvaccinated dogs.


Another almost cute-sounding name for a disease that is anything but adorable. Heartworm disease is a condition in which a parasite sets up shop in your dog’s heart, lungs, and blood vessels. It’s contracted when a mosquito infected with the disease bites your dog. The mosquito bite leaves behind microfilariae, which then become larvae, and eventually matures into adult heartworms.

There are 4 different stages of heartworm disease and the symptoms you notice will depend on which stage of the disease your pup is currently in.

The first stage may not include any symptoms at all–if anything, maybe just a light cough. In stage 2, you may notice your dog is a bit more lethargic than usual, in addition to developing a light cough. Stage 3 is when the symptoms may begin to become more apparent. In this stage, you’ll likely notice lethargy after light activity, a consistent cough, and slight difficulty breathing.

The fourth stage is obviously the most dangerous. In this stage, it’s possible for the amount of worms inside of your dog to actually cause blockages of blood flow back to your dog’s heart. This usually requires immediate surgery and can be fatal if left untreated. 

Treatment for heartworm disease would vary depending on the stage. If surgery is not required, treatment would involve a round of antibiotics, followed by a rest period, followed by three injections of a drug called melarsomine, which are administered 30 days apart. After that, your pup would receive an additional 30 days of steroids. It’s a grueling treatment process, which is easily avoidable as long as you’re properly taking care of your dog. 

Your vet can prescribe your pup medication to be taken once a month, and you can have your dog tested annually, which will likely be covered by your pet health insurance if you have a policy. As long as you keep up with the doses, you’ll likely never even have to think twice about heartworm. 

Canine distemper

Canine distemper is a virus that affects the dog’s gastrointestinal, respiratory, and central nervous systems. It’s easily spread from dog-to-dog contact–from urine, saliva, blood, sharing food bowls, and even through airborne exposure. 

With canine distemper, there are two stages of symptoms. In the first stage, you’ll notice a fever, nasal and eye discharge, lethargy, coughing, diarrhea, and vomiting. During the second stage, the symptoms will become more severe as the disease begins to attack the central nervous system. Here, your pup may experience head tilt, partial or full paralysis, seizures, muscle twitches, and in some cases, death. 

Dogs who make it through the acute stage of the virus may also develop hyperkeratosis of the paw pads and nose. That means their nose and paw pads may harden and enlarge, which can be very uncomfortable. 

But let’s stop to take a breath for a sec. It obviously goes without saying, canine distemper is one of the most serious diseases your dog can contract–however, it’s also one of the most preventable. 

Be sure your puppy has had full rounds of distemper vaccinations, and keep those vaccinations up to date throughout your dog’s entire life. Do your best to avoid any gaps in vaccinations. Obvious, but worth noting–keep your dog away from any other infected animals or wildlife if possible. 

Kennel cough

Canine infectious tracheobronchitis–or kennel cough–is a highly contagious respiratory disease. It can spread easily through animals in close proximity. Dog parks, training groups, and doggy daycares are all potential breeding grounds for this nasty little bug (this explains the name–the infection can spread quickly among dogs in the close quarters of a kennel or animal shelter). Young puppies, older dogs, and unvaccinated dogs would be most at-risk.

The symptoms to look out for are usually a runny nose, sneezing, lethargy, low fever, loss of appetite, and a strong cough that might resemble a “goose honk.” While the symptoms of kennel cough are usually mild–and the disease is easily treatable–symptoms such as these should always be reported to your vet, since they can sometimes be signs of more dangerous illnesses. 

Treatment will usually entail just a couple weeks rest, some antibiotics, and maybe a cough suppressant to ease the symptoms.

Luckily, there are also measures you can take in order to potentially prevent them from contracting kennel cough. A vaccine is available for the bordetella bacterium, which is the most common agent to cause kennel cough. So if you know your pup may be staying in any kind of doggy daycare of boarding facility, be sure to have them vaccinated! 

Kidney disease

Just like humans, dogs can also develop kidney disease. There are several different causes of kidney disease in dogs, and by the time your pup begins to show signs of the disease, the initial cause may not even be apparent anymore. Some causes can include birth defects in the kidneys, diseases associated with the immune system, cancer, and acute kidney disease (usually caused by poisoning). Older dogs are also more prone. 

When the issue is not acute, the disease will be characterized by normal kidney functions beginning to slow and malfunction. Symptoms you’ll want to look out for include a change in volume of drinking and/or urination, weight loss, loss of appetite, depression, and sometimes vomiting.

Sadly, kidney disease is typically not something that can be cured. However, you can treat it with medicine, and implement certain vet-prescribed diets to help slow the progression to allow your dog to go on living happily for years after diagnosis. 


Also known as “lepto,” leptospirosis is a highly contagious bacterial infection that can lead to liver, kidney, and lung disease. Lepto is zoonotic, meaning it can be passed along to humans, so protecting your dog will also help to protect you.

Leptospirosis is usually transmitted through direct or indirect contact with another animal’s infected urine. Infected animals shed the bacteria when they urinate, leaving their surrounding environment contaminated. The bacteria can then enter your dog’s body through abrasions or cuts in the skin following exposure to infected urine, blood, placenta, or contaminated water or soil.

Symptoms to look out for would include fever, shivering, muscle tenderness, dehydration, vomiting, diarrhea, loss of appetite, lethargy, or jaundice (yellowing of the whites of their eyes or the inside of their ears, gums, or the exposed skin of their belly). It’s super important to let your vet know right away if you see your dog experiencing any of these symptoms–delaying treatment for too long could result in severe kidney or liver damage, and even death. 

But luckily, leptospirosis is fairly easy to prevent. The best way to protect your dog from lepto is to vaccinate them against it. A lepto vaccine is not always part of a routine vaccination program, so make sure to ask your vet about it if it’s something you’re concerned about. 

Lyme disease

Just like humans, dogs can contract Lyme disease via bites from certain species of ticks. The actual disease is caused by a bacterium carried by the tick–once the bacteria is in the bloodstream, it can travel to different parts of the body and cause illness along with problems with certain organs and joints.

Many animals can have Lyme disease and show no signs. In dogs, the most common symptoms include fever, loss of appetite, painful or swollen joints, lameness that comes and goes, swollen lymph nodes, and lethargy. If Lyme disease is left untreated it can lead to damage in the kidneys, nervous system, and heart. In certain cases, it can even be fatal. 

Lyme disease is another one that is also pretty simple to prevent. There’s a few different vet-approved flea and tick preventatives on the market, so speak to your veterinarian to find the best and most appropriate product for your dog. There is also a vaccine that can help prevent against the disease.

Lastly, make sure to simply check your pup’s fur after they’re finished playing outside, especially if they were romping around in taller grass or wooded areas. For short-haired dogs, it’s a pretty simple task, but it can be especially tedious for dogs with thicker coats. However, the more time you spend thoroughly checking their coat, the better. Be sure to check between their toes, around their ears, their belly, under their tail, and near their butt.


Though preventable, rabies is definitely a disease that evokes a lot of fear–and for good reason. The rabies virus can affect all mammals, and it’s spread by direct contact with the saliva of an infected animal. Like lepto, rabies is zoonotic, meaning it can be spread from animals to humans. Transmission of the virus is usually through a bite wound, but can also spread through a scratch or an existing open wound. 

If you know what you’re looking for, the symptoms of the rabies virus will be hard to miss. An infected dog may show extreme behavioral changes such as restlessness, apprehension, or aggression. Dogs who are normally very friendly may become irritable, while normally excitable animals may become more docile. A dog may bite or snap more than usual, attacking other animals, humans and sometimes inanimate objects. They may also have a fever.

As it progresses, they may become hypersensitive to light and sounds, have seizures, and can become extremely aggressive. During the final stages, the dog may experience paralysis of the nerves that control the head and throat, which can result in the well-known symptom of foaming at the mouth. As the paralysis progresses, the dog will eventually go into respiratory failure and pass away.

Okay, so we’re aware that this was not an easy section to read. But wipe the sweat from your forehead and relax… Rabies is a vaccine-preventable disease. Modern rabies vaccines for dogs are extremely safe, effective, and in most cases, required by law. So as long you’ve been bringing your pup to the vet regularly, you shouldn’t have to worry. 


Ringworm is a fungus which grows and lives in the outermost layer of skin and in the hair follicles of infected dogs, and occasionally in the nails. It can affect humans and other animals, and is highly contagious.

It’s typically contracted when a dog comes into contact with other animals infected with ringworm, particularly in places like dog parks, kennels, and shelters.

The symptoms are fairly easy to spot–ringworm will usually be characterized by circular skin lesions or patchy bald spots which will illuminate under a black light. In most cases, it’s pretty simple to treat as well. Your vet will likely prescribe your pup an antifungal shampoo and/or ointment; for more severe cases, oral antifungals will be required. Ringworm can be passed from dogs to humans, so be extra cautious if you know your pup is infected. Keep in mind that the average amount of time for the infection to clear is around 100 days.

The best way to prevent ringworm in dogs would be to regularly clean your home and any grooming tools or bedding that your pup may regularly come into contact with–especially if your pup is hanging around other animals often. 


The dreaded C word… Just like humans, dogs are also at risk for developing different types of cancer. It’s not contagious, and there isn’t a single defined cause. However, your dog’s likelihood of developing cancer can have a lot to do with its genes–just like in humans. 

Early detection of cancer is key, so it’s important to recognize any abnormalities and have them treated as soon as possible. Some warning signs of cancer include persistent or abnormal swelling, loss of weight and/or loss of appetite, bleeding or abnormal discharge from any body opening, difficulty eating or swallowing, lethargy or loss of stamina, persistent lameness or stiffness, and difficulty breathing, urinating, or defecating.

While these symptoms can be signs of cancer, it’s best not to let yourself get too worried right away, as they can also be common symptoms of other illnesses. However, the moral of the story here is simply to have your pup checked out by a vet at the first sign of any of these symptoms. 

Cancer will likely never be 100% preventable, and just like with humans, there’s no vaccine for it–however there are definitely steps you can take to decrease the likelihood that they’ll contract it. First, consider spaying or neutering your dog. Spaying your female dog before her first heat can significantly decrease the chances of her getting breast cancer, and similarly, neutering a male dog will decrease the risk of testicular cancer. 

Just like their human counterparts, dogs are also affected by their environment. So while you’re trying to avoid environmental risks like cigarette smoke, toxic chemicals, and excessive sunlight, make sure you’re doing the same for your pup. 


Brucellosis is a contagious infection caused by the bacterium brucella canis. Typically, the most at-risk dogs are strays, or dogs with no access to regular veterinary care or spay/neuter procedures. It’s pretty unlikely to affect any domestic pet, and is typically only a concern for breeders. However, should it occur, it’s oftentimes manageable, but incurable. 

Brucellosis affects female and male dogs in very specific ways. In females, the most common clinical symptom is infertility.

In males, there may be inflammation of the epididymis, which is a part of the testicles. In the early phase of the infection, the testes will be enlarged and painful. As the infection progresses, the testes become firm and shrunken. Infected males will usually become sterile due to testicular damage. Infected males may also develop prostatitis (inflammation of the prostate gland), which would usually result in difficulty urinating and defecating.

Currently, there is no vaccine for brucellosis. In terms of prevention, a simple blood testing of both a male and female dog prior to breeding is the best bet. This is another one that can be transmitted to humans, so managing this infection is imperative. 

Canine herpesvirus

The doggy variety of the herpes virus is also referred to as CHV. Crushingly, the virus is also known as “fading puppy syndrome,” due to the affect it can have on newborn pups. The effects of the disease are most pronounced in newborns who who have an infected mother. CHV-infected puppies will be weak, have no appetite, have discolored faces, and they’ll usually pass away before treatment can even begin. 

Licking, sniffing, and sexual intercourse are the primary methods of transmission. Infected dogs can easily transmit the virus to others in crowded spaces if they also have kennel cough. Like Brucellosis, canine herpes is mainly a concern among dog breeders and it oftentimes not noticeable in adult dogs. However, unlike brucellosis, canine herpesvirus cannot be passed on to humans. There is unfortunately no cure, nor a vaccine.

What diseases can potentially kill a dog?

Just like humans, dogs are vulnerable to illness and disease, often with tragic consequences. There are many serious dog diseases that are possibly fatal (although in many cases such outcomes can be avoided with early diagnosis and proper treatment). Some ailments that could potentially kill a dog include canine parvovirus, kidney disease, Lyme disease, heartworm, canine distemper, rabies, lepto, fungal infections, and cancer

What disease can kill a dog in 2 days?

That would be canine parvovirus, which we’ve already discussed above. If your dog or puppy exhibits any of the symptoms of this disease—vomiting, diarrhea, loss of appetite, weight loss, dehydration, fever, and lethargy—get them to the vet immediately. 

Can dogs get STDS?

This is a tough question. It might be a bit weird to think about your fur babies being sexually active, since they’re essentially like your children–but there are technically STDs your dog might be able to contract or transmit. Those include brucellosis and transmissible venereal tumors (TVT), both pretty rare. Other dog diseases could be spread by close, non-sexual contact, but they wouldn’t be classified as “STDs.” 

This is a lot…but don’t get too stressed!

dog illness

We realize this was a ton of info–but, again, understanding the various types of dog diseases is vital. At the end of the day, the main takeaway here would be to simply, 1) make sure your pup is fully vaccinated, and gets check-ups regularly, and 2) contact your vet if you notice anything unusual like: sudden weight loss, weight gain, loss of appetite, or change in behavior. And hey, it never hurts to have your furry friend set up with pet health insurance when they’re just a puppy. 

Now, please… stop reading, and scratch your dog’s belly. 


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