Viral Diseases

The environment of viruses is constituted essentially by the cells they infect. Viruses must parasitize cells to ensure their propagation. Outside cells, viruses lack of activity, although to allow transmission to another individual they need to survive outside the cell. The way a virus survives in the environment is the result of an adaptation that largely determines how it is transmitted. Viruses can be transmitted through direct contact between individuals, or through other ways such as, for instance air, water, feces, body fluids, food, or fomites. In some cases, transmission needs the participation of other living organisms, so-called vectors, in which the virus is equally propagated. These vectors are often blood-sucking insects that inoculate the infectious pathogen through their bites, thus spreading the infection in a population. A virus may preferably use a single transmission route, but viruses using more than one way of transmission are frequent.1 Vaccinations against canine viral disease are especially important because no specific treatment exists to directly combat these agents once they gain a foothold within the dog's body.

Canine distemper most frequently affects young dogs, but is sometimes seen in older animals. The disease takes three forms: digestive, with high fever, vomiting, diarrhea, loss of appetite, and severe dehydration; respiratory, with the same general signs and coughing; and nervous, marked by meningitis and spasms and usually ending in death of the animal. Distemper virus may be carried on the nose or the paw pads. Specific antibiotics and anticonvulsants are usually disappointing and preventive vaccination is the only effective way to control this disease. The prognosis varies; as a general rule, the older dog is, the less likely it is to die from distemper.

Infectious hepatitis is particularly common among male dogs in their first year and is transmitted through urine. Infected animals may have high fever, intense thirst, and severe cramps. The mucous tissue are saffron yellow; in some cases the whole cornea turns bluish; this color disappears when the dog is well again. The prognosis is good for dogs that survive the first 48 hours. Treatment of infectious hepatitis is carried out by the veterinarian. It is supportive in nature, consisting of serum, antibiotics, and vitamin supplements, particularly the B vitamin complex. Vaccines are the best prevention.

The Parainfluenza virus is the cause of serious tracheobronchitis. It usually infects dogs housed in kennels and grooming establishments. A dry, noisy cough, easily triggered by pressing on the throat, develops over the course of several weeks. Preventive vaccines contain antibodies which fight against influenza.

Rabies is a terrible, dangerous scourge for all warm-blooded animals that can be found throughout the world. The disease exists in 2 forms: Raging and Paralytic. Ten to sixty days after being bitten by a rabid animal, the dog shows an obvious change in behavior as the virus attacks the nervous system. A usually agitated, aggressive dog may become calm and timid, or a gentle animal may become an unpredictable biter. A rabid animal must be terminated, but it is difficult to know in advance whether the animal is rabid or not. Certainly it must be isolated, but the decision to have it destroyed can be made only after seeing the illness evolve. The final diagnosis can be made after the brain has been examined during the autopsy. It is best to confirm the diagnosis before treating humans bitten by the sick dog because rabies vaccines can be dangerous. If your dog is bitten by an animal suspected of having rabies, take the dog as soon as you can to a veterinarian to be vaccinated (if it has not already been) or to have a booster shot. The vaccine is very effective if it administered at once. If it is shown that the animal that bit the dog was rabid, the infected dog will be destroyed, unless it can be proved that it has been vaccinated. Vaccination is carried out after the age of five months. It involves a regular booster shot. This is legally compulsory in afflicted areas, for crossing international borders, and in boarding kennels.

Parvovirus is a serious disease that is characterized by profuse brownish or bloody diarrhea and rapid dehydration. If the dog is not treated very quickly, it may die within 24 hours. The sick dog may recover, if it receives good supportive therapy consisting of plenty of serum (intravenous fluids) and antibiotics. Various vaccines are available and yearly boosters are recommended.

In the past, Canine coronavirus usually produced only a mild enteritis. More recently, new strains of coronavirus have caused severe systemic disease with fever, diarrhea, and neurological signs.2

Canine Herpesvirus 1, also called canine herpesvirus, canine tracheobronchitis virus, and kennel cough virus, is a species of Varicellovirus virus that causes often fatal necrotising rhinitis and pneumonia in newborn puppies. In older animals, it may cause tracheobronchitis (kennel cough).

Canine oral papillomavirus causes papillomas on the lips, which spread inside the mouth. Canine papillomavirus causes papillomas on the skin.

Canine influenza virus emerged around 2000 when an equine influenza virus (EIV) was transmitted to dogs in Florida. After 2003, the canine virus was carried by infected greyhounds to various parts of the United States and then became established in several large animal shelters, where it has continued to circulate.

More recent viral diseases in dogs have been associated with newly discovered Pneumovirus (respiratory disease), kobuviruses, and sapoviruses (diarrheic disease).


  1. Animal viral diseases and global change: bluetongue and West Nile fever as paradigms
  2. Edward J. Dubovi. Fenner's Veterinary Virology
  3. Microevolution of Canine Influenza Virus in Shelters and Its Molecular Epidemiology in the United States
  4. Pneumovirus in Dogs with Acute Respiratory Disease
  5. Viruses in diarrhoeic dogs include novel kobuviruses and sapoviruses

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