Dogs are prone to several infectious diseases caused by viruses, bacteria, fungi, and parasites. Some of the most common infectious diseases that can affect dogs include:

1. Parvovirus: This highly contagious virus affects the gastrointestinal tract of dogs, causing severe vomiting, diarrhea, dehydration, and in some cases, death. It is transmitted through contact with infected feces and can survive in the environment for months.
2. Canine Distemper: This viral disease is spread through contact with infected respiratory secretions and affects the respiratory, gastrointestinal, and nervous systems of dogs. It can cause fever, coughing, vomiting, diarrhea, seizures, and even death.
3. Kennel Cough: Also known as canine infectious tracheobronchitis, kennel cough is a respiratory disease caused by several bacterial and viral pathogens. It is highly contagious and spreads through direct contact with infected dogs, or exposure to contaminated surfaces.
4. Leptospirosis: This bacterial infection affects the liver and kidneys of dogs and can be transmitted through contact with infected urine or contaminated water. It can cause fever, vomiting, diarrhea, dehydration, and in severe cases, organ failure and death.
5. Lyme Disease: Caused by the bacteria Borrelia burgdorferi, Lyme disease is spread through tick bites and can affect the joints, heart, and nervous system of dogs. Symptoms may include fever, lameness, joint pain, lethargy, and loss of appetite.
6. Canine Influenza: Similar to human influenza, canine influenza is a respiratory disease caused by two different strains of the influenza virus. It is highly contagious and can cause coughing, sneezing, fever, and in severe cases, pneumonia.
7. Heartworm Disease: This parasitic infection is spread through the bite of infected mosquitoes and affects the heart and lungs of dogs. It can cause coughing, lethargy, weight loss, and in severe cases, heart failure.

Prevention and treatment of these infectious diseases vary depending on the specific disease. Vaccination, regular parasite prevention, and good hygiene practices, such as proper handwashing and disinfecting of surfaces, can help reduce the risk of transmission. It is important for pet owners to keep their dogs up-to-date on vaccinations and to consult with a veterinarian for proper diagnosis and treatment of any suspected infections.