Dogs can get sick for many reasons: viruses, bacteria, parasites, allergies, dental problems, age-related changes or environmental factors. Some conditions are mild and easy to manage. Others, such as canine parvovirus or distemper, can become life-threatening very quickly.
This guide explains the most common dog diseases, the signs you should watch for, how prevention works and when it is time to contact a veterinarian.
It is not always easy to know whether a symptom is serious. A dog may only seem “a little tired” at first, but early changes in appetite, stool, breathing, skin, ears or behaviour can give you valuable clues.
Important notice: This article is for educational purposes only. It does not replace veterinary diagnosis or treatment. If your dog is unwell, in pain, has difficulty breathing, has blood in stool or vomit, collapses, has seizures or deteriorates quickly, contact your veterinarian or an emergency clinic immediately.
Editorial note: Written and reviewed by the Dogtorcito team using veterinary references from AVMA, WSAVA, AAHA, Merck/MSD Veterinary Manual, Cornell University College of Veterinary Medicine and CDC resources. Last reviewed: May 17, 2026.
Quick guide: common dog diseases and warning signs
| Disease or condition | Common signs | Main prevention |
|---|---|---|
| Canine parvovirus | Vomiting, bloody diarrhoea, lethargy, loss of appetite | Core vaccination, hygiene, avoiding risky exposure before puppy vaccines are complete |
| Canine distemper | Fever, nasal or eye discharge, cough, diarrhoea, neurological signs | Core vaccination |
| Kennel cough | Dry honking cough, gagging, mild fever, tiredness | Risk-based vaccination, avoiding crowded dog spaces during outbreaks |
| Mange | Itching, hair loss, crusts, red or irritated skin | Parasite prevention, avoiding contact with infected animals |
| Leishmaniasis | Weight loss, skin lesions, lethargy, nail changes, kidney problems | Sandfly repellents, collars or spot-ons, vaccination where recommended |
| Otitis externa | Head shaking, scratching ears, bad smell, ear discharge | Ear checks, drying after baths, managing allergies |
| Periodontal disease | Bad breath, tartar, red gums, pain, loose teeth | Tooth brushing, dental checks, professional cleanings |
Infectious diseases in dogs
Infectious diseases are caused by organisms such as viruses, bacteria or other pathogens. Some spread through direct contact with infected dogs, contaminated environments or respiratory droplets. Puppies, senior dogs, unvaccinated dogs and dogs with weakened immune systems are usually at higher risk.
Canine parvovirus
Canine parvovirus is one of the most serious infectious diseases in dogs, especially in puppies and unvaccinated dogs. It mainly attacks the gastrointestinal tract and can cause severe dehydration in a short period of time.
Common symptoms of parvovirus
- Sudden vomiting
- Severe diarrhoea, often bloody
- Loss of appetite
- Extreme tiredness or weakness
- Fever or low body temperature
- Abdominal pain
- Dehydration
Parvovirus is highly contagious and can survive in the environment for long periods. That is why prevention is not only about vaccines, but also about hygiene and avoiding high-risk areas until a puppy is properly protected.
How to prevent parvovirus
The most important preventive measure is vaccination. Puppies need a complete vaccination schedule, and adult dogs need boosters according to your veterinarian’s recommendations.
Until your puppy is adequately vaccinated, avoid:
- Dog parks
- Busy pavements used by many unknown dogs
- Kennels or daycares with unknown vaccination status
- Contact with sick dogs
- Areas contaminated with faeces
When to contact the vet
Contact your veterinarian urgently if your dog, especially a puppy, has vomiting, diarrhoea, blood in the stool, sudden weakness or refuses food. Parvovirus can progress quickly and requires veterinary care.
Canine distemper
Canine distemper is a contagious viral disease that can affect several body systems, including the respiratory, digestive and nervous systems. It can cause long-term complications and may be fatal.
Common symptoms of distemper
- Fever
- Watery or pus-like discharge from the eyes or nose
- Coughing
- Sneezing
- Vomiting or diarrhoea
- Loss of appetite
- Lethargy
- Muscle twitching
- Tremors or seizures in advanced cases
Distemper can be difficult because symptoms may appear in stages. A dog may first show respiratory signs and later develop digestive or neurological problems.
How to prevent distemper
Vaccination is the best protection. Distemper is included in the group of core vaccines recommended for most dogs.
When to contact the vet
Contact your vet if your dog has respiratory signs together with fever, diarrhoea, severe tiredness or any neurological sign such as tremors, twitching or seizures.
Kennel cough
Kennel cough, also known as canine infectious respiratory disease complex, is a contagious respiratory condition. It often spreads in places where dogs gather, such as kennels, shelters, grooming salons, daycare centres, training classes and dog parks.
Common symptoms of kennel cough
- Persistent dry cough
- Honking cough
- Gagging or retching
- Sneezing
- Nasal discharge
- Mild fever
- Reduced energy
Many cases are mild, but puppies, senior dogs and dogs with existing health problems can develop more serious respiratory illness.
How to reduce the risk
Your vet may recommend vaccination against Bordetella and other respiratory pathogens if your dog frequently mixes with other dogs.
You can also reduce risk by:
- Avoiding crowded dog spaces during outbreaks
- Keeping sick dogs away from other dogs
- Choosing kennels or daycares that require vaccination
- Avoiding shared bowls in high-traffic dog areas
When to contact the vet
Call your vet if your dog has difficulty breathing, stops eating, seems very weak, has a fever or the cough does not improve.
Parasitic diseases in dogs
Parasites can affect the skin, digestive system, blood, organs or general health. Some are visible, such as fleas and ticks, while others require veterinary testing.
Sarcoptic and demodectic mange
Mange is a skin disease caused by mites. The two most common types are sarcoptic mange and demodectic mange.
Sarcoptic mange
Sarcoptic mange, also called canine scabies, is usually very itchy and contagious between dogs. It can also cause temporary irritation in humans who have close contact with an affected dog.
Common signs include:
- Intense itching
- Hair loss
- Red skin
- Crusts or scabs
- Thickened or irritated skin
- Wounds from scratching
- Secondary skin infections
Demodectic mange
Demodectic mange is caused by mites that can normally live on a dog’s skin in small numbers. It may become a problem in puppies, immunocompromised dogs or dogs with underlying health problems.
Common signs include:
- Patchy hair loss
- Red or scaly skin
- Skin infections
- Mild or intense itching, especially if infection develops
How to prevent mange
Prevention depends on the type of mite and the dog’s risk. Regular parasite control may help protect against several external parasites, but any suspected mange case should be diagnosed by a veterinarian.
Avoid contact with infected animals until your vet confirms the cause and treatment plan.
When to contact the vet
See your vet if your dog has intense itching, spreading hair loss, crusts, wounds, bad skin smell or recurring skin infections.
Leishmaniasis
Leishmaniasis is a parasitic disease transmitted by sandfly bites. It is especially important in Mediterranean regions and other endemic areas. Symptoms may appear months or even years after infection.
Common symptoms of leishmaniasis
- Weight loss
- Lethargy
- Skin ulcers or scaling
- Hair loss, especially around the eyes or ears
- Overgrown nails
- Swollen lymph nodes
- Nosebleeds
- Increased thirst or urination
- Kidney problems
Leishmaniasis can affect several organs, so early detection and veterinary follow-up are very important.
How to reduce the risk
Prevention focuses on reducing sandfly bites. Depending on your area, your veterinarian may recommend repellents, collars, spot-on products, vaccination or regular testing.
Useful habits include:
- Avoiding walks at dusk and dawn during high-risk seasons
- Using vet-approved sandfly repellents
- Keeping dogs indoors during peak sandfly activity
- Using fine mesh screens when appropriate
- Testing dogs that live in or travel to endemic areas
When to contact the vet
If you live in or travel to an endemic area and your dog shows weight loss, skin lesions, unusual tiredness, nosebleeds or increased thirst, ask your veterinarian about leishmaniasis testing.
Ear disease in dogs
Ear problems are very common in dogs. Some breeds are more prone to them, especially dogs with floppy ears, narrow ear canals, allergies or frequent exposure to water.
Otitis externa
Otitis externa is inflammation or infection of the external ear canal. It can be painful and often becomes recurrent if the underlying cause is not addressed.
Common symptoms of otitis externa
- Head shaking
- Scratching the ears
- Bad smell from the ear
- Redness or swelling
- Dark, yellow or waxy discharge
- Pain when touching the ear
- Tilting the head
- Rubbing the head against furniture or the floor
Ear infections can be linked to allergies, moisture, parasites, foreign bodies, excessive wax or anatomical predisposition.
How to reduce the risk
- Check your dog’s ears regularly
- Dry the ears after baths or swimming
- Use only vet-approved ear cleaning products
- Do not insert cotton swabs deep into the ear canal
- Ask your vet about allergies if ear infections keep coming back
When to contact the vet
See a vet if your dog has ear pain, bad smell, discharge, repeated head shaking, swelling or recurring ear infections. Ear medication should be chosen according to the cause, so diagnosis matters.
Dental disease in dogs
Dental disease is one of the most common health problems in adult dogs. It often starts with plaque and tartar build-up, then progresses to gum inflammation, pain, infection and, in severe cases, tooth loss.
Periodontal disease
Periodontal disease affects the gums and structures that support the teeth. It can cause pain even if the dog continues to eat normally.
Common symptoms of periodontal disease
- Bad breath
- Yellow or brown tartar
- Red or bleeding gums
- Difficulty chewing
- Drooling
- Pawing at the mouth
- Loose or missing teeth
- Reduced appetite
- Preference for soft food
Small breeds and older dogs are often at higher risk, but any dog can develop dental disease.
How to prevent dental disease
The most effective home habit is brushing your dog’s teeth with dog-safe toothpaste. Dental chews, dental diets and water additives may help, but they do not fully replace brushing or veterinary dental checks.
Ask your vet how often your dog needs professional dental cleaning.
When to contact the vet
Book a veterinary check if your dog has bad breath, tartar, red gums, difficulty chewing, bleeding from the mouth, loose teeth or signs of oral pain.
General warning signs: when your dog needs urgent care
Some symptoms should never be ignored. Contact a veterinarian quickly if you notice:
- Repeated vomiting or diarrhoea
- Blood in stool, urine or vomit
- Difficulty breathing
- Collapse or loss of consciousness
- Seizures
- Sudden weakness
- Pale or blue gums
- Swollen or painful abdomen
- Inability to urinate
- Refusing food for more than 24–48 hours
- Severe pain
- Rapid worsening of symptoms
- Suspected poisoning
- Heatstroke signs such as heavy panting, weakness or collapse
If you are unsure whether it is urgent, call your vet and describe the symptoms. It is safer to ask early than to wait until the problem becomes serious.
How to reduce your dog’s risk of disease
Not every disease can be prevented, but many risks can be reduced with consistent care.
Keep vaccinations up to date
Core vaccines protect against severe diseases such as parvovirus and distemper. Your vet may also recommend additional vaccines depending on your dog’s lifestyle, age, region and exposure risk.
Dogs that go to kennels, daycare, grooming salons, dog parks or training classes may need extra protection against respiratory diseases.
Follow parasite prevention
Parasites can cause skin disease, digestive problems and serious systemic illness. Keep your dog’s deworming and parasite prevention schedule updated.
Your dog’s plan may depend on:
- Age
- Weight
- Lifestyle
- Region
- Travel habits
- Contact with other animals
- Local parasite risks
Book regular veterinary check-ups
Many conditions are easier to manage when detected early. Regular check-ups help monitor teeth, ears, skin, weight, heart, joints and general health.
Senior dogs or dogs with chronic conditions may need more frequent visits.
Watch for small behaviour changes
Dogs often show illness through subtle changes before obvious symptoms appear.
Pay attention to:
- Sleeping more than usual
- Eating less
- Drinking more water
- Avoiding walks
- Coughing
- Scratching
- Head shaking
- Hiding
- Irritability
- Changes in stool or urination
Keep your dog’s health records organised
Vaccines, deworming dates, test results, treatments, symptoms and vet visits are easier to manage when they are stored in one place.
This is especially useful if your dog has a chronic condition, visits different clinics or needs emergency care.
Track symptoms and prevention with Dogtorcito
When your dog is sick, it is easy to forget important details: when the vomiting started, how often your dog coughed, whether the diarrhoea had blood, which medication was given or when the last vaccine was due.
With Dogtorcito, you can keep your dog’s health information organised in one place.
What you can record in Dogtorcito
- Vaccines
- Deworming
- Parasite prevention
- Symptoms
- Treatments
- Vet visits
- Diagnoses
- Medication
- Weight changes
- Notes and observations
- Medical history for each dog
Why it helps during illness
A clear record helps you explain the situation better to your veterinarian.
For example, you can note:
- When symptoms started
- How often they occur
- Whether they are getting better or worse
- Photos of skin lesions, wounds or ear discharge
- Medication given
- Appetite, stool and energy changes
- Follow-up appointments
This information can help your vet understand the progression of the problem and adjust the treatment plan if needed.
Useful if you have more than one dog
If you have several dogs, each one can have an individual profile. That way, vaccines, symptoms, reminders and medical history do not get mixed up.
Is your dog showing symptoms?
If your dog has vomiting, diarrhoea, coughing, skin lesions, ear pain, weight loss, bad breath, unusual tiredness or any sudden change in behaviour, contact your veterinarian.
And if you want to stay better organised, create your Dogtorcito account and start tracking your dog’s health today.
With Dogtorcito, you can:
- Remember vaccines and deworming
- Track symptoms before a vet visit
- Store medical history
- Follow treatment progress
- Manage several dogs separately
- Share clearer information with your veterinarian
The best way to protect your dog is a combination of prevention, observation and timely veterinary care. Vaccines, parasite control, dental care, regular check-ups and organised health records can make a real difference in your dog’s quality of life. 🐾
FAQ
What are the most common dog diseases?
The most common conditions include canine parvovirus, canine distemper, kennel cough, mange, leishmaniasis, otitis externa and periodontal disease. Many of them can be prevented or caught early with vaccination, parasite prevention and regular veterinary checkups.
How do I know if my dog is sick?
Common warning signs are loss of appetite, unusual tiredness, vomiting, diarrhoea, coughing, excessive thirst, skin changes, hair loss or sudden changes in behaviour. If you are unsure, contact your veterinarian.
How can I best protect my dog from disease?
The most effective measures are keeping vaccinations up to date, using regular parasite prevention, caring for your dog’s teeth, booking routine veterinary checkups and paying attention to early changes in behaviour.
Can dog diseases spread to humans?
Most conditions, such as parvovirus or distemper, only affect dogs. Some parasites, like sarcoptic mange, can cause temporary skin irritation in people who have close contact with an affected dog. Simple hygiene measures are usually enough to minimise the risk.
When should I take my dog to the vet immediately?
Seek urgent care for: difficulty breathing, collapse, seizures, blood in stool or vomit, persistent severe vomiting or diarrhoea, pale or blue gums, severe pain, inability to urinate or any rapid worsening of your dog’s condition.
Bibliography
- AVMA — Canine parvovirus
- AVMA — Canine distemper
- MSD Veterinary Manual — Canine distemper
- WSAVA — 2024 Vaccination Guidelines for Dogs and Cats
- AAHA — 2022 Canine Vaccination Guidelines
- Merck Veterinary Manual — Mange in Dogs and Cats
- Merck Veterinary Manual — Ear Infections and Otitis Externa in Dogs
- Cornell University College of Veterinary Medicine — Periodontal Disease
- CDC Emerging Infectious Diseases — Topical insecticide treatments to protect dogs from sand fly vectors of leishmaniasis
- CDC — Leishmaniasis Control in Dogs
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