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Common Infectious Diseases in Dogs: Top 10 Infections to Know

What is it?

Infectious diseases in dogs refer to a wide range of illnesses caused by viral, bacterial, or fungal agents. These diseases can be highly contagious and can spread rapidly among dogs and other animals. Diagnosis typically involves laboratory testing to identify the specific pathogen causing the infection.

How is it Treated?

Medication such as antibiotics or antiviral drugs may be prescribed to help control the infection. Supportive care such as intravenous fluids, nutritional support, and other interventions may also be necessary to manage symptoms and prevent complications.

Breed Predispositions

Bulldogs Shar Peis German Shepherds Cavalier King Charles Spaniels


Over the past few days, Mark had observed that his usually energetic and playful Labrador Retriever, Buddy, had become increasingly lethargic and had lost interest in eating. Concerned about his furry friend’s well-being, Mark decided it was time to visit the veterinarian. After a detailed examination and a series of tests, the vet informed Mark that Buddy had contracted an infectious disease. Mark was taken aback by the diagnosis, as he had always been diligent about Buddy’s vaccinations and overall health.

Dogs are very susceptible to certain types of infections. The most common ones include canine distemper, parvovirus, coronavirus, and leptospirosis. These viruses can spread rapidly among dogs, causing severe illness or death.

It’s essential to understand the causes, symptoms, and how to prevent each common disease so that you can recognize them early and seek treatment immediately. For example, the following are some of the most common infectious diseases your dog might have:

1. Canine Parvovirus (“parvo”)

Canine parvovirus (CPV) is a highly contagious viral infection that affects dogs, particularly puppies and unvaccinated dogs. It belongs to the Parvoviridae family and primarily targets the gastrointestinal tract. The virus can cause severe illness and life-threatening, especially in young or immunocompromised dogs.

CPV is transmitted through direct contact with infected dogs or their feces. It can also be spread indirectly through contaminated objects or environments. The virus is highly resistant and can survive in the environment for months, making it easily transmissible.

Once a dog is infected, the virus attacks rapidly, dividing cells in the intestinal lining, bone marrow, and lymphoid tissues. This leads to severe gastroenteritis, causing symptoms such as vomiting, diarrhea (often bloody), lethargy, loss of appetite, and dehydration. In some cases, CPV can also affect the heart, leading to myocarditis.

Prompt diagnosis and treatment are crucial for managing canine parvovirus infection. Veterinary care typically involves supportive therapy for dehydration, electrolyte imbalance, and secondary bacterial infections. In addition, dogs with parvovirus require strict isolation to prevent the spreading of the infection, and in severe cases, hospitalization may be necessary.

Prevention is key to protecting dogs from CPV. Vaccination is highly effective and typically included in puppies’ core vaccination protocols. In addition, maintaining good hygiene, avoiding contact with infected dogs or their feces, and disinfecting contaminated areas are essential preventative measures.

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Canine distemper, a common canine disease, is an extremely contagious viral ailment affecting dogs and other animals. It’s triggered by the canine distemper virus (CDV), a member of the Paramyxoviridae family. This disease of dogs primarily impacts the respiratory, gastrointestinal, and nervous systems of the afflicted animals.

The virus is mainly transmitted through respiratory secretions or feces from infected animals, allowing it to spread between animals. However, it can also propagate through objects contaminated by the virus or via direct contact with infected animals. Puppies and unvaccinated dogs are particularly prone to contracting this disease.

Upon infection, the virus proliferates through the respiratory tract and the lymphatic system, aiming at different organs and tissues. It can precipitate various symptoms, including fever, nasal and ocular discharge, coughing, vomiting, diarrhea, lethargy, and loss of appetite. In severe instances, distemper can also provoke neurological symptoms, such as seizures, tremors, and alterations in behavior, making it a common cause of such symptoms in dogs.

Diagnosing distemper generally involves the consideration of clinical signs, history, and laboratory tests such as blood analyses and viral detection from swabs or tissue samples. Unfortunately, no targeted antiviral treatment for distemper exists, so providing supportive care becomes crucial. This includes managing symptoms, supplying fluids to prevent dehydration, and preventing secondary bacterial infections.

Vaccination is one of the most effective ways to protect your dog from distemper. It is typically included in the core puppy vaccination protocols, much like a vaccine for Lyme disease, another disease affecting animals and people. Distemper is a severe and often fatal disease, so prevention through vaccination and avoiding exposure to infected animals is paramount. In addition, practices like maintaining good hygiene, quarantining infected dogs, and disinfecting areas contaminated by the virus also aid in curbing the spread of this virus.

3. External Parasites

External parasites in dogs are organisms that live on the outer surface of the dog’s body and feed on its blood or skin. These parasites can cause discomfort, irritation, and various health issues for dogs. Common external parasites in dogs include fleas, ticks, lice, mites, and mange. 

  • Fleas are tiny, wingless insects that infest the dog’s fur, causing itching, scratching, and allergic reactions. They can also transmit diseases and parasites.
  • Ticks are arachnids that attach to the dog’s skin and feed on its blood. They can transmit various diseases, such as Lyme disease and Ehrlichiosis.
  • Mites are microscopic organisms that can cause various skin conditions in dogs. Examples include ear mites, which infest the dog’s ear canals, and sarcoptic mange mites, which cause mange and intense itching.
  • Lice are small insects that infest the dog’s fur, causing itching, scratching, and hair loss. They are most commonly seen in puppies and dogs with weakened immune systems.

External parasites can be prevented and treated through various methods, including regular grooming, flea and tick prevention products, maintaining a clean living environment, and seeking veterinary treatment when necessary. However, it’s important to address external parasite infestations promptly to prevent discomfort, reduce the risk of disease transmission, and maintain the overall health and well-being of the dog.

infectious disease in dogs

4. Fungal Infectious Disease

Fungal infectious diseases in dogs are caused by various fungi that can infect the dog’s body and cause various health issues. Fungi are microorganisms that can thrive in different environments and infect different parts of the dog’s body, including the skin, respiratory system, digestive system, and internal organs.

Common fungal infections in dogs include:

  • Dermatophytosis (Ringworm): This fungal infection affects dogs’ skin, hair, and nails. It can cause circular patches of hair loss, redness, itching, and crusty lesions.
  • Aspergillosis: This is a respiratory infection caused by the Aspergillus fungus. Dogs can inhale the spores, leading to respiratory symptoms such as coughing, difficulty breathing, nasal discharge, and sneezing.
  • Blastomycosis: This is a systemic fungal infection caused by the fungus Blastomyces. It commonly affects the lungs but can also spread to other organs. Symptoms may include coughing, difficulty breathing, weight loss, skin lesions, and eye problems.
  • Histoplasmosis: This is another systemic fungal infection caused by the fungus Histoplasma. Dogs can contract the infection by inhaling fungal spores. It can affect the lungs, liver, spleen, and other organs. Symptoms may include coughing, weight loss, loss of appetite, and fever.
  • Cryptococcosis: This is a fungal infection caused by the Cryptococcus fungus. It primarily affects the respiratory system but can also involve the central nervous system. Symptoms may include nasal discharge, respiratory distress, neurological signs, and eye problems.

Fungal infections in dogs are typically diagnosed through clinical signs, microscopic examination of samples, fungal culture, and other specialized tests. In addition, treatment often involves antifungal medications specific to the type of infection and supportive care to manage symptoms and promote healing. Therefore, it’s important to consult a veterinarian to diagnose and treat fungal infections in dogs.

5. Leptospirosis

Leptospirosis is a bacterial infection that afflicts dogs, other animals, and even humans. This disease is caused by bacteria belonging to the Genus Leptospira. These bacteria, typically present in the urine of infected animals, have a remarkable ability to survive in soil and water for prolonged periods. As a result, dogs are susceptible to infection through contact with contaminated water, soil or through interaction with infected animals, including rodents, wild animals, and wildlife.

The clinical presentations of leptospirosis can vary, ranging from mild to severe. In certain instances, dogs may not exhibit any discernible symptoms, while in others, the disease could progress rapidly, culminating in serious illness. Common indications of leptospirosis in dogs include:

  • fever
  • lethargy
  • decreased appetite
  • vomiting, diarrhea
  • abdominal pain
  • muscle pain
  • jaundice (yellowing of the skin and eyes)

Leptospirosis also qualifies as a zoonotic disease, signifying that it can be transmitted from animals to humans. Therefore, exercising caution is vital when interacting with an infected dog or when contacting its bodily fluids, including contact with animal feces.

The diagnosis of leptospirosis is usually determined through a mix of clinical signs, blood tests, and specific laboratory tests aimed at detecting the presence of Leptospira bacteria or antibodies in the dog’s blood or urine. Treatment typically incorporates antibiotics to exterminate the bacteria and supportive care to manage symptoms and avoid complications.

Prevention of leptospirosis includes vaccination, avoiding interaction with potentially contaminated environments or animals, and adhering to good hygiene practices, such as donning protective gloves when handling potentially infected animals or their fluids. Further, a consultation with a veterinarian is vital for diagnosing, treating, and preventing leptospirosis in dogs. Finally, it’s essential to remember that dogs carry many diseases, and this virus is very contagious, underscoring the importance of preventative measures.

6. Kennel Cough

Kennel cough, or canine infectious tracheobronchitis, is a highly contagious respiratory infection many dogs can contract. Viruses and bacteria, including canine parainfluenza, canine adenovirus, and Bordetella bronchiseptica, typically cause this illness. Notably, the disease occurs when these pathogens are present and easily spread in areas where dogs are nearby, such as kennels, dog parks, or grooming facilities.

The cardinal symptom of kennel cough is a persistent, dry, hacking cough, often forceful and suggestive of a dog attempting to clear its throat. Dogs may also display symptoms including sneezing, nasal discharge, a mild fever, loss of appetite, and lethargy. The cough may sometimes worsen, leading to discomfort and difficulty breathing.

Despite being a relatively new disease identified in the world of canine health, kennel cough is usually categorized as a self-limiting disease. This is because it naturally resolves on its own within a few weeks. Nonetheless, it can advance to more acute respiratory infections or pneumonia in certain instances, particularly in puppies or dogs with compromised immune systems. Thus, attentive observation of the dog’s symptoms and timely veterinary care are paramount.

The therapeutic approach for kennel cough chiefly involves supportive care to mitigate symptoms. This may involve administering cough suppressants or bronchodilators to facilitate easier breathing. Also, if a bacterial infection is suspected, antibiotics may be prescribed to prevent secondary bacterial infections. Rest and isolation from other dogs are also vital to prevent the disease from spreading further. Knowing that most dogs will recover is reassuring, but immediate veterinary attention is needed when disseminated disease occurs.

7. Rabies

Rabies is a lethal viral disease impacting the nervous systems of mammals, including dogs, which can lead to dire neurological symptoms. The rabies virus, responsible for the disease, is typically transmitted via the bite or scratch from an affected dog or other infected animals. This disease is caused by the virus infiltrating the brain and spinal cord.

In its initial stages, rabies in dogs may present indistinct symptoms. These can encompass behavioral shifts such as heightened aggression or withdrawal, excessive salivation, and challenges in swallowing. As the disease advances, more severe symptoms manifest in the affected dogs. These include muscular weakness, paralysis, confusion, seizures, and eventual coma or death. Rabies is a fatal disease once its clinical signs surface; currently, no cure exists.

Since rabies is a zoonotic infection capable of transmission to humans and other animals, prevention is paramount. Rabies vaccination is the most effective measure to safeguard dogs against this disease. It’s usually administered in a series starting at a young age, followed by regular booster shots. Dog rabies vaccination is a legal requirement in numerous jurisdictions, including the United States.

In regions where rabies is prevalent, maintaining close supervision of dogs, including female dogs who might be more vulnerable due to pregnancy or nursing, is critical to prevent contact with wild animals like bats, raccoons, skunks, and foxes, which are common virus carriers. This precaution is especially important during events where many dogs, like a dog show, are gathered. If a potentially rabid animal bites a dog, immediate veterinary care is necessary, and the incident must be reported to the local animal control or public health authorities. Timely and appropriate management can help curtail the spread of rabies to humans, other animals, and even healthy dogs, thus mitigating the overall risk of infection.

8. Canine Parainfluenza

Canine parainfluenza is a highly contagious respiratory virus that affects dogs. It is one of the pathogens commonly associated with kennel cough, a respiratory infection characterized by a harsh, dry cough. Canine influenza is caused by the parainfluenza virus, which primarily affects the respiratory system of dogs.

The virus is spread through respiratory secretions, such as coughing or sneezing, from infected dogs. It can also be transmitted indirectly through contaminated surfaces or objects. Puppies, elderly dogs, and dogs with weakened immune systems are particularly susceptible to infection.

The symptoms of canine parainfluenza include a persistent, dry cough, nasal discharge, sneezing, and mild respiratory distress. The infection may sometimes progress to more severe respiratory symptoms, such as pneumonia. It is important to note that canine parainfluenza can be easily mistaken for other respiratory infections, so proper diagnosis by a veterinarian is essential.

Vaccination against CPIV is recommended for puppies younger than eight weeks old. Vaccinated puppies older than eight weeks old should receive booster vaccinations every three months. Booster vaccines are available commercially.

9. Canine Coronavirus

Canine coronavirus is a highly contagious viral infection that primarily affects the gastrointestinal system of dogs. It is caused by the canine coronavirus (CCoV) and is different from the coronavirus strain that causes COVID-19 in humans.

Canine coronavirus is spread through contact with infected feces, contaminated surfaces, or oral exposure to infected material. Puppies and dogs with weakened immune systems are more susceptible to the virus. The virus primarily affects the small intestine, leading to inflammation and damage to the intestinal lining.

The symptoms of canine coronavirus infection can vary but commonly include diarrhea, vomiting, loss of appetite, lethargy, and dehydration. In severe cases, it can lead to more serious gastrointestinal issues. It is important to note that canine coronavirus infection can be easily mistaken for other gastrointestinal illnesses, so proper diagnosis by a veterinarian is essential.

Preventing canine coronavirus involves good hygiene practices, such as proper sanitation of living areas, regular cleaning of food and water bowls, and prompt removal and disposal of feces. Vaccination against canine coronavirus is available in some regions but is not considered a core vaccine and is generally recommended based on the dog’s risk of exposure. Therefore, consulting with a veterinarian is crucial to determine the appropriate preventive measures for each dog.

10. Canine Hepatitis

Infectious canine hepatitis (ICH), also referred to as canine hepatitis, is a prevalent viral ailment primarily affecting the livers and other organs of domestic dogs. The disease is instigated by canine adenovirus type 1 (CAV-1), and its transmission is highly efficient, spreading through contact with infected dogs’ urine, feces, saliva, or nasal secretions.

The signs of infectious canine hepatitis in dogs can fluctuate, depending on the intensity of the infection. Light cases might present symptoms such as fever, lethargy, diminished appetite, and coughing. More severe cases can result in jaundice (yellowing of the eyes and mucous membranes), abdominal discomfort, vomiting, diarrhea, and possibly life-threatening complications like liver failure and clotting disorders. This inflammatory disease is usually more severe in young dogs, while older dogs may have milder symptoms or be asymptomatic carriers.

There exists a vaccination to avert canine hepatitis, and it’s often incorporated into the core vaccination regimen for dogs. In addition, vaccination aids in fostering immunity against the virus, diminishing the threat and harshness of the disease. Hence, dog owners must adhere to the suggested vaccination timeline and ensure their dog’s vaccinations remain current.

If you suspect that your dog might have canine hepatitis, immediate veterinary attention is vital. Treatment usually involves supportive care tailored to manage symptoms and ward off complications. This care may encompass intravenous fluids, medications to bolster liver function, and other supportive therapies suited to the specific needs of the individual dog. Moreover, early detection of this common form in dogs, combined with preventive measures like vaccination and proper hygiene practices, can significantly aid in protecting dogs from canine hepatitis. Therefore, the infection is usually manageable if caught early and treated appropriately.

Frequently Asked Questions

Treating an infected dog depends on the specific infection and its severity. In general, treatment may involve a combination of the following approaches:

  • Antibiotics: Bacterial infections are typically treated with appropriate antibiotics prescribed by a veterinarian. The specific antibiotic will depend on the type of bacteria involved and its susceptibility to different medications.
  • Antifungals: Fungal infections may require antifungal medications, such as oral or topical medications, to eliminate the fungal organisms. The specific antifungal treatment will depend on the type of fungus causing the infection.
  • Antivirals: Viral infections may require antiviral medications, although treatment options can vary depending on the specific virus. In some cases, supportive care and management of symptoms are the primary focus, as there may not be direct antiviral treatments available for certain viral infections.
  • Topical Treatments: External infections, such as skin or ear infections, may require topical treatments, such as medicated shampoos, creams, or ear drops, to target the infection locally.
  • Supportive Care: Besides specific treatments for the infection, supportive care may be necessary to help the dog recover. This can include providing a comfortable environment, adequate nutrition, hydration, and monitoring for any medication complications or side effects.

It’s important to consult a veterinarian for proper diagnosis and treatment recommendations for an infected dog. They will evaluate the specific infection, consider the dog’s overall health and individual needs, and develop an appropriate treatment plan tailored to the situation.

The duration of a dog virus can vary depending on the specific virus and the dog’s overall health. Some viral infections in dogs may last a few days, while others can persist for several weeks or months. It is important to note that viral infections may have different stages, including an incubation period, an active infection phase, and a recovery period. The length of each stage can vary. Additionally, the severity of the infection and the individual dog’s immune response affect how long the virus lasts. Prompt veterinary care, supportive treatment, and following the recommended treatment plan can help shorten the duration of the virus and promote a faster recovery.

The recovery time for a sick dog can vary greatly depending on the specific illness or condition, the severity of the illness, the dog’s overall health, and the effectiveness of the treatment provided. Some dogs may recover within a few days or weeks, while others may require longer periods, especially for more serious or chronic conditions. Therefore, it is important to consult with a veterinarian for an accurate diagnosis and appropriate treatment plan tailored to your dog’s specific needs. Following the veterinarian’s instructions, providing necessary medications, and offering supportive care, such as proper nutrition, rest, and a stress-free environment, can help promote a faster recovery for your dog.

Vaccination is an important and effective preventive measure against various infectious diseases in dogs. Vaccines stimulate the dog’s immune system to recognize and defend against specific pathogens, such as viruses or bacteria, that can cause diseases. Vaccinations can help protect dogs from serious illnesses like distemper, parvovirus, rabies, and canine influenza, among others. By vaccinating your dog, you can significantly reduce their risk of contracting these diseases and, in many cases, prevent them altogether. It’s important to follow a proper vaccination schedule recommended by your veterinarian to ensure that your dog receives the necessary vaccines at the appropriate times to maintain their immunity and overall health.

Certain fungi that affect dogs can potentially transfer to humans, leading to fungal infections. These infections are known as zoonotic fungal infections. Examples include ringworm (caused by the fungus Microsporum or Trichophyton) and some types of Dermatophytosis (fungal skin infections). Direct contact with an infected dog’s skin, hair, or contaminated items such as bedding or grooming tools can increase the risk of transmission. Therefore, it’s important to practice good hygiene and take necessary precautions when handling or treating a dog with a fungal infection to minimize the risk of transmission to humans.

Dogs can potentially catch several diseases from humans, including:

  • Influenza: Certain strains of influenza viruses can infect both humans and dogs. Canine influenza (dog flu) is a contagious respiratory illness that can be transmitted from dogs to humans and vice versa.
  • Methicillin-resistant Staphylococcus aureus (MRSA): This is a type of antibiotic-resistant bacteria that can be transmitted between humans and dogs. Dogs can become carriers of MRSA and potentially infect humans through close contact.
  • Tuberculosis: While rare, dogs can contract tuberculosis (TB) from humans with active TB infections. This is more common in areas where TB is prevalent.
  • Salmonella: Dogs can become infected with Salmonella bacteria from contaminated food, and in turn, they can potentially transmit the bacteria to humans through fecal matter or direct contact.

It’s important to note that the transmission of these diseases between humans and dogs is not very common, and the risk can be minimized through good hygiene practices, such as proper handwashing, regular veterinary care, and appropriate handling of food and waste.

You are unlikely to pass a common cold virus directly to your dog. The viruses that cause the common cold in humans are typically specific to humans and do not easily infect dogs. Similarly, dogs have their own set of respiratory viruses that are specific to them and do not commonly infect humans. However, practicing good hygiene when you’re sick is always a good idea, such as washing your hands thoroughly and avoiding close contact with your dog or their food and water bowls to minimize potential risks. If your dog shows signs of respiratory illness, it’s best to consult a veterinarian for proper diagnosis and treatment.

Respiratory Syncytial Virus (RSV) is primarily a human virus, and it is rare for dogs to contract RSV from humans. RSV typically affects infants and young children, causing respiratory symptoms such as cough, runny nose, and fever. It is not a common infection in dogs, and there have been no documented cases of dogs transmitting RSV to humans or vice versa. However, if you have concerns about your dog’s respiratory health or if they are showing symptoms of illness, it’s always best to consult with a veterinarian for an accurate diagnosis and appropriate treatment.

One of the dogs’ most common bacterial infections is skin infection, pyoderma. Various bacteria, including Staphylococcus intermedius, Streptococcus spp., and others, can cause these infections. Bacterial skin infections in dogs often result in symptoms such as redness, itching, hair loss, sores, and a foul odor. Other common bacterial infections in dogs include urinary tract infections, respiratory infections, and ear infections. It’s important to note that the specific bacterial infection can vary depending on the dog’s age, environment, and overall health. If you suspect your dog has a bacterial infection, it’s recommended to consult with a veterinarian for proper diagnosis and treatment.

Signs of infection in a dog can vary depending on the location and type of infection. However, some common signs of infection in dogs include:

  • Redness, swelling, or inflammation in the affected area.
  • Discharge, pus, or foul odor from a wound, ear, or other body part.
  • Increased body temperature (fever).
  • Lethargy or decreased energy levels.
  • Loss of appetite.
  • Pain or discomfort when touched or when the infected area is manipulated.
  • Lameness or limping if the infection affects the joints or limbs.
  • Changes in behavior, such as increased irritability or aggression.
  • Changes in the appearance or texture of the skin, such as rashes or lesions.
  • Excessive licking, scratching, or biting of a particular area.

If you notice any of these signs in your dog, it is important to seek veterinary care for proper diagnosis and treatment of the underlying infection.

One of the leading causes of death in dogs is cancer. Cancer can affect various organs and systems in the body, and it can be aggressive and difficult to treat. Common types of dog cancer include lymphoma, mast cell tumors, bone cancer (osteosarcoma), and hemangiosarcoma. Other significant causes of death in dogs include age-related conditions such as organ failure, heart disease, and kidney disease. It is important to note that the prevalence and impact of different diseases can vary depending on the individual dog’s breed, age, and overall health. Regular veterinary check-ups, preventive care, and early detection can help improve outcomes and prolong the lifespan of dogs.

Disclaimer: The information provided on this veterinary website is intended for general educational purposes only and should not be considered as a substitute for professional veterinary advice, diagnosis, or treatment. Always consult a licensed veterinarian for any concerns or questions regarding the health and well-being of your pet. This website does not claim to cover every possible situation or provide exhaustive knowledge on the subjects presented. The owners and contributors of this website are not responsible for any harm or loss that may result from the use or misuse of the information provided herein.

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