Pneumonia is an irritation of the lungs caused by different sources. It is characterized by an inflammation of the deep lung tissues and the bronchi. Pneumonia can be acute or chronic. This life-threatening illness is more common in cats than in dogs and the complication “Kennel Cough” can occur in young pets. Routes of infection Many causes can trigger an infection of the deep lung tissues. Specifically in younger pets an weak immune system can encourage pneumonia. Concretely, the overreaction of various causes irritate the lungs. Fungal The most represented fungal infections are Coccidioides and Cryptococcus. Cryptococcus are most common in cats. Bacterial Pneumonia is most often caused by a bacterial infection. The bacterial infection occurs mainly after a viral infection. Some examples are canine distemper virus, adenovirus type 1 and 2, parainfluenza virus and feline calicivirus. Those viral infections cause lesions in the airways that allow bacteria to enter the respiratory system more easily. The pneumonia caused by Tuberculous appears more often in dogs. Gastric acid can also trigger pneumonia when a pet is throwing up, because the bacteria can more easily get in the lungs. Viral The disease progression begins with a viral infection which spreads into the respiratory tract and later develops into pneumonia. The symptoms of viral infections like canine distemper virus, adenovirus type 1 and 2, parainfluenza virus and feline calicivirus benefit a bacterial infection which ends in pneumonia. Parasitic Parasites, for example lung worms like Filaroides, Aelurostrongylus or Paragonimus get in the bronchi and cause pneumonia. Allergic Through an allergic reaction, the lung is infiltrated by inflammatory cells which cause pneumonia without any infection. Protozoan The probability that a dog or cat gets pneumonia through protozoans like Toxoplasma gondii or Pneumocystis jirovecii is really low. Aspiration There are several factors which might cause vomiting, for example dysfunctional esophagus, wrong medication or wrong food. By vomiting, the gastric acid injures the upper respiratory system which becomes vulnerable to bacterial infection and causes pneumonia. Symptoms Dogs and cats who develop pneumonia usually show symptoms like moist or productive cough, followed by nasal discharge and breathing sounds. After some time, the respiratory rate becomes more rapid and breathing difficulties appear. Another conspicuous indication is appetite loss, followed by weight loss. Fever and lethargy are also common symptoms. Also an obvious sign of a regular virus infection is that the pet does not respond to the threat of