In general, viral organisms cannot live and reproduce except within the living cells of the dog (host). This one main and important characteristic separates viruses from bacteria. Viral infections can be picked up from the air, soil or other inanimate objects. Most viruses, however, cannot and do not survive very long outside of the dog. The major exception to this rule would be canine parvovirus that can survive for many months in the environment. It is also important to note that viruses that infect dogs do not infect people and visa versa. Also, most dog owners erroneously think that their dog is safe in their house or backyard. FALSE! Viruses cannot be kept out, and often owners or the wind carry deadly disease right to the dog on a regular basis. For this reason preventative vaccination is extremely important.

Caused by the canine distemper virus, a relative of human measles, this is a common and highly contagious disease. It is most often contracted by inhalation through the respiratory tract. Young pups and older animals are most commonly affected but any dog not properly vaccinated will be susceptible.

Clinical signs vary greatly and can include a mild fever, loss of appetite, a discharge from the eyes and nose and coughing. In more severe cases, nasal and eye discharges can be quite heavy; severe coughing, vomiting and diarrhea will also occur. Often, bacteria cause what is known as a secondary infection, meaning that they cause another infection in addition to the distemper infection. Some dogs may die. Others that recover may have no other problems, but more often, 1-3 weeks after the generalized illness, severe systemic neurologic disease begins including seizures, neck pain, muscle tremors, staggering/trouble with balance and unusual behavior. ((Canine Distemper))

If pregnant females are infected, pups may be aborted, stillborn, or born weak and die soon after birth. Pups that do survive can also develop neurologic disease a few months after birth. Young pups infected can have severe loss of tooth enamel and cardiomyopathy. Diagnosis is based on the history, including vaccination status, clinical signs, blood counts, and special serologic testing for the disease. Distemper may mimic several other respiratory and neurologic diseases, confusing the diagnosis.

There is no real treatment of canine distemper; all care is supportive while the disease runs its course. Fluid therapy is needed so dogs with vomiting and diarrhea do not dehydrate and die. Antibiotics are important to control secondary infection. Vitamins and nutritional supplements are often employed to keep the patient's strength up. Dogs who develop neurologic symptoms often need to be euthanised, as medication is rarely effective.

Caused by the canine parvovirus, "Parvo" is a very common and highly contagious disease of dogs of all ages, but strikes young puppies the hardest. Dogs infected with parvo pass huge quantities of virus in their feces, saliva and vomitus. This virus can literally "hang out" in the environment and be moved around for months from location to location on feet, by cats or insect or on other objects. Many cases have been seen in dogs vaccinated with over-the-counter vaccines or at "quick-shot" clinics so care should be taken, not only to vaccinate all dogs, but also to be certain that quality is not neglected. 

Once the dog encounters the virus orally or through the nose, the virus replicates quickly in intestinal cells and in the bone marrow and thusly causes severe damage to these areas. Clinical signs include a sudden onset (often very sudden) of not eating, vomiting and diarrhea, with the diarrhea turning bloody in a few days. Dogs usually are quite depressed and quickly become dehydrated. Diagnosis is based on history including if and how the dog was vaccinated, clinical signs, blood counts and a special fecal parvo test.

Without treatment approximately 90% of dogs will die in a few days. Rare cases of the illness can also lead to heart failure and sudden death in very young pups. Certain breeds are more susceptible to the virus including Doberman Pinschers, Pit Bulls and Rottweilers, the latter being most severely affected and hardest to treat.  ((Parvo Diarrhea))

This author advises prompt treatment by a facility experienced in care for these dogs and by those who somewhat like to treat parvo patients. In our hands over 90% of all dogs treated survived. We have encountered, however, practitioners who prefer not to treat these dogs due to the high level of care involved. The Rottweiler, also, will be much more difficult to save than other breeds in general.

For best results, patients should be hospitalized and placed on IV fluids, massive doses of antibiotics, anti-vomiting drugs, intravenous feeding and serum transfusions in some cases. Intensive monitoring and high quality nursing care is essential to save these dogs. While the virus itself cannot be killed, most dogs that can be kept alive for 4-10 days post infection will recover completely. Dogs exposed to parvo-infected patients should be given a parvo vaccine containing killed virus only as soon as practical.

Alternately, some patients are treated on an outpatient basis, receiving fluids and medications at a veterinary facility, then being kept at home. While this may produce a cost savings for the pet owner, survival rates will be 25-50% lower than for hospitalized dogs. Most dogs that recover have no lasting side effects but they certainly need to be kept current on preventative vaccines to prevent another infection.

Caused by the canine coronavirus, this virus produces a gastrointestinal infection of similar but lesser severity than that of canine parvovirus. This virus often invades and causes further damage to dogs who already have parvo, or it may cause vomiting and diarrhea on its own. Because the virus does not attack the bone marrow and does not damage the intestines as badly as parvo, most cases are not as severe although death can occur.

Clinical signs include loss of appetite, vomiting, dehydration and a green-yellow foul smelling diarrhea that can be intermittent. Diagnosis is based on history, clinical signs, blood counts and determining that the infection is not parvovirus. There are no specific tests for this disease. With treatment, most dogs will survive.

Treatment is very similar to that of canine parvovirus with the exception that most (but not all) dogs seem to recover more quickly that do parvo dogs. For best results patients should be hospitalized and placed on IV fluids, antibiotics, anti-vomiting drugs and intravenous feeding. Intensive monitoring and high quality nursing care is essential. While the virus itself cannot be killed, most dogs that can be kept alive for 4-10 days post infection can recover completely. Alternately, some patients are treated on an outpatient basis, receiving fluids and medications at a veterinary facility, then being kept at home. While this may produce a cost savings for the pet owner, survival rates will be 25-35% lower than for hospitalized dogs.

Infectious canine hepatitis (ICH) is caused by what is called canine adenovirus type 1. Dogs and foxes can both be infected and harbor the virus which is passed in the urine for 6-9 months after infection. The virus is stable in the environment for some time and attacks primarily the liver of dogs that become infected. Dogs become infected when the virus enters the nose or mouth of the animal. Older dogs are almost never affected with most patients being under 1 year of age.

Some dogs may become ill so quickly that owners think the pet has been poisoned. Clinical signs include a very sudden and rapid onset of fever, abdominal pain, small hemorrhages on the lips, seizures, convulsions and death. Dogs can be dead a few hours after clinical signs start. Less than fatal cases will exhibit depression, loss of appetite, some vomiting and diarrhea, a high fever and enlargement of the lymph nodes.

Still other dogs may develop blue eye where one or both corneas become a cloudy blue color. Some will have very mild fever and throat inflammation, while others will develop a more severe chronic hepatitis that leads to a slowly progressive deterioration of the patient. It is important to note that this illness cannot affect people and that human hepatitis involves a virus specific to people. Diagnosis can be a challenge, based on history, including vaccine history, clinical signs, blood counts, serum chemistries and special serologic tests specific for ICH.

There is no specific treatment for the ICH virus so supportive care is essential to save the dog. Heavy fluid therapy through the IV route, antibiotics to protect against secondary infection and strong nutritional support are essential. The prognosis is good for milder cases, poor for the more severely affected dogs.

Rabies is a viral illness that attacks the nervous system of the dog and other warm-blooded animals. An animal or man gets rabies by being bitten by an infected animal and on rare occasion through contact with other bodily fluids. When the dog is bitten, the virus replicates in peripheral nerves, travels to the brain and spinal cord where further damage is inflicted, and lastly spreads to other tissues allowing it to be transmitted to other creatures. In the wild, bats, foxes, raccoons and skunks all carry and promulgate the illness.

An infected dog will first show changes in their behavior for 1-3 days and there may be a mild fever, dilation of the eyes and extreme pain around the bite wound. Then, for 1-7 days, the dog will salivate, have trouble walking and at the slightest stimuli become viscous and attack. Then, usually 2-10 days after the infection has started, the dog enters what is known as the "dumb" phase. For the final 2-4 days of the infection the dog will squint, the third eyelid with notably protrude, the voice may change and then the patient falls into a coma, respiratory paralysis and death.

Diagnosis is based on clinical signs and a special IFA test performed on brain tissue from the dead animal. If a dog bites a human it will be quarantined for about 10 days for observation. If no signs are present all involved can rest easily. Dogs showing clinical symptoms or animals otherwise killed after a bite will (MUST) have their brain examined by this IFA test for rabies. Since this is such a serious human health hazard, all dogs older than 4 months of age should receive regular rabies vaccination. There is no treatment for canine rabies.

Herpes in dogs usually results in a rapidly fatal disease of young puppies. Pups acquire the virus from the mother during passage out of the birth canal. In less than 1 week these pups will become weak, refuse to nurse, tremble and appear rather listless. They may pass yellow fluid in the stool, seem to have a painful abdomen, and later many pups have evidence of hemorrhage in the skin or from bodily orifices. Death will occur within 2 days of becoming ill.

Older dogs will most often have few, mild or no clinical symptoms but harbor the virus, especially in the genital tract of the male or female dog. Diagnosis is based on history, clinical signs and special tests to detect the virus. Often the diagnosis is obtained with post-mortem specimens from dead puppies. There is no treatment or prevention other than to never breed dogs suspected or known to harbor the virus.

Parainfluenza is one of several different viruses that can cause canine infectious tracheobronchitis also known as kennel cough. This is a slightly stable virus that can be passed from dog to dog through the air, which then leads to respiratory tract infection. For more specific information please see the highlighted topic.

CANINE INFLUENZA

Canine influenza is a highly contagious respiratory infection of dogs that is caused by the canine influenza virus, a virus that is closely related to the virus that causes equine influenza. It is thought that the equine influenza virus mutated to produce the canine influenza virus.

Two clinical syndromes have been seen in dogs infected with the canine influenza virus—a mild form of the disease and a more severe form that is accompanied by pneumonia.

Dogs suffering with the mild form of canine influenza develop a soft, moist cough that persists for 10 to 30 days. Some dogs have a dry cough similar to the kennel cough virus complex. For this reason, canine influenza virus infections are frequently mistaken for "kennel cough." Dogs with the mild form of influenza may also have a thick nasal discharge, which is usually caused by a secondary bacterial infection.

Dogs with the severe form of canine influenza develop high fevers (104ºF to 106ºF) and have clinical signs of pneumonia, such as increased respiratory rates and effort. Pneumonia may be due to a secondary bacterial infection.

Because this is a newly emerging disease, almost all dogs, regardless of breed or age, are susceptible to infection and have no immunity. Virtually all dogs that are exposed to the virus become infected and nearly 80% show clinical signs of disease. Fortunately, most affected dogs have the mild form.

Fatal cases of pneumonia resulting from infection with canine influenza virus have been reported in dogs, but the fatality rate (5% to 8%) has been low so far.

As with any disease caused by a virus, treatment is largely supportive. Good animal care practices and nutrition assist dogs in mounting an effective immune response. In the milder form of the disease usually resolves quickly after treatment with a broad-spectrum bactericidal antimicrobial. In the more severe form of the disease with pneumonia responds best to hydration (sometimes via intravenous administration of fluids) and a broad-spectrum bactericidal antimicrobial.

To date, there is no evidence of transmission of canine influenza virus from dogs to people.

Back to Dog Index

HOME PAGE | HOSPITAL INFORMATION | PET HEALTH INFORMATION

©2007 James W. Day D.V.M., P.C.