Diseases in Dogs pt.1

Viral diseases

Rabies

A rabid dog

Rabies is a viral disease commonly associated with dogs, although in recent years canine rabies has been practically eliminated in North America and Europe due to extensive and often mandatory vaccination requirements. However it is still a significant problem in Africa, the Middle East, Latin America, and Asia. Dogs are considered to be the main reservoir for rabies in developing countries. Areas that are rabies-free, (usually islands) such as Britain, Ireland, Australia, and the American state of Hawaii have strict quarantine laws to keep their territories rabies-free. These require long periods of isolation and observation of imported animals, which makes them unattractive places to move with a pet unless the pet is quite young. Areas that are not rabies-free usually require that dogs (and often cats) be vaccinated against rabies.

Historically, rabies has long been linked to dogs. The earliest mention of rabies is in the Codex of Eshnunna (ca. 1930 BC) (written prior to the Code of Hammurabi), which dictates that the owner of a dog showing symptoms of rabies should take preventative measure against bites. If a person was bitten by a rabid dog and later died, the owner was fined heavily. The sacred animal of the Babylonian goddess of health Gula or Ninisina was the dog; if a person insulted a dog, Gula caused that dog to bite the person and inflict them with rabies. In the 1800s the infectious nature of rabies was first demonstrated by taking the saliva from a rabid dog and injecting it into another animal.

Rabies in dogs is a fatal disease transmitted by the bite of an infected mammal, such as a cat, raccoon, bat, or another dog. Animals with rabies suffer deterioration of the brain and tend to behave bizarrely and often aggressively, increasing the chances that they will bite another animal or a person and transmit the disease. Three stages of rabies are recognized in dogs and other animals. The first stage is a one to three day period characterized by behavioral changes and is known as the prodromal stage. The second stage is the excitative stage, which lasts three to four days. It is this stage that is often known as furious rabies due to the tendency of the affected dog to be hyperreactive to external stimuli and bite at anything near. The third stage is the paralytic stage and is caused by damage to motor neurons. Incoordination is seen due to rear limb paralysis and drooling and difficulty swallowing is caused by paralysis of facial and throat muscles. Death is usually caused by respiratory arrest.

A person or dog bitten by an unknown dog (or other animal) should always be treated without waiting for symptoms, given the potentially fatal consequences of a rabid biter: there have been very few cases of someone surviving rabies when treatment was not begun until after symptoms appeared. Depending on local laws, dogs that are showing neurological signs at the time of the bite are euthanized in order to have their brain tested for rabies. Unvaccinated healthy dogs need to be confined for ten days from the time of the bite (at home or at a veterinarian depending on local law). If the dog is not showing signs of rabies at the end of ten days, then the bitten person could not have been exposed to rabies. Dogs and cats do not have the rabies virus in their saliva until a few days prior to showing symptoms. Ten day confinement does not apply to other species. A dog or cat bitten by a wild animal in an area known to have rabies should be confined for six months, because it can take that long for symptoms to start. This is an incentive to dog-owners to vaccinate their dogs even if they feel the risk of their dog contracting rabies is low, since vaccination will eliminate the need for their dog to be euthanized or impounded should it bite anyone or be suspected of biting anyone.

Other viral diseases

Other canine viral diseases of note include parvovirus, distemper, infectious canine hepatitis, herpesvirus, and influenza.

Canine parvovirus (caused by canine parvovirus type 2, canine parvovirus type 1 is also known as canine minute virus) causes a highly contagious gastrointestinal infection that is especially severe in puppies. It is spread through contact with infected feces. The virus attacks rapidly dividing cells, notably those in the lymph nodes, intestinal crypts, and the bone marrow. There is depletion of lymphocytes in lymph nodes and necrosis and destruction of the intestinal crypts. Symptoms and signs include vomiting, bloody diarrhea, depression, severe dehydration, fever, and low white blood cell counts. Although there is no specific treatment for the canine parvovirus, aggressive intravenous fluid therapy and antibiotics for dogs with secondary bacterial infections is usually required.

Canine distemper, caused by a paramyxovirus similar to the cause of measles, is a highly contagious disease that affects the respiratory, gastrointestinal, and central nervous systems. It is spread through either direct contact with respiratory excretions, through the air, or on fomites (inanimate objects such as clothing). Symptoms and signs include discharge from the eye or nose, coughing, difficulty breathing, vomiting, diarrhea, depression, seizures, and paralysis. Similar to canine parvovirus, treatment is supportive.

Infectious canine hepatitis is caused by canine adenovirus type 1. The virus is spread in the feces, urine, blood, saliva, and nasal discharge of infected dogs. It causes a liver infection and a bleeding disorder. Signs and symptoms include fever, depression, loss of appetite, coughing, tender abdomen, and spontaneous hemorrhages. Treatment is symptomatic.

Canine herpesvirus is a virus of the family Herpesviridae which most importantly causes a fatal hemorrhagic disease in puppies less than two to three weeks old. It is transmitted to puppies in the birth canal and by contact with infected oral and nasal secretions from the mother or other infected dogs, but it is not spread through the air. Signs and symptoms include depression, nasal discharge, and weakness. The inability of very young puppies to mount a febrile response seems to be a significant contributing factor to the high mortality rate in this age dog - it can reach 80 percent. In adult dogs, canine herpesvirus can cause abortion.

Canine influenza usually refers to infection with equine influenza virus H3N8. This virus was found to infect dogs in 2004, and the disease was very contagious due to the dog's lack of natural immunity. Signs and symptoms include cough and nasal discharge, and in more severe cases fever and pneumonia. Canine influenza has a high morbidity but a low mortality.

as edited from Wikipedia