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Infectious Diseases

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Canine Influenza

Canine influenza is a respiratory disease caused by a type A influenza virus. It is spread by aerosolized respiratory secretions and by contaminated objects (bedding, food and water bowls) and people moving between infected and uninfected populations. The time from exposure to showing signs of illness is 2-4 days and the virus is shed for 4-7 days after clinical signs first appear.

Because this is a relatively new pathogen, virtually all dogs that are exposed become infected since they have no natural or vaccine-induced immunity. Nearly 20% of infected dogs show NO clinical signs, but they still shed the virus and can spread the infection.

The clinical presentation of canine influenza varies considerably. There are those previously mentioned that show no signs of illness at all. Most (roughly 60%) will have an upper respiratory illness that may mimic kennel cough. The cough tends to be a bit more moist, however, and it persists for 10-30 days despite treatment with antibiotics and cough suppressants. There may be low-grade fever and nasal discharge. The remaining 20% of infected dogs develop more severe signs including high fever (104-106 F) and increased respiratory rate and effort. Pneumonia, precipitated or complicated by secondary bacterial infection, can be a life threatening result of influenza infection.

Treatment is supportive and includes maintaining good nutrition, using antibiotics to control secondary infections and intravenous fluids to maintain hydration in more severely affected cases. Some dogs recover with little or no intervention while others require intensive care for several days. There is currently no vaccine for canine influenza, so routine precautions are essential to preventing spread of the infection. The virus is easily killed by a number of disinfectants, including dilute bleach, so careful cleaning of the environment should eliminate the virus. Isolation of infected dogs and careful sanitation are the only tools we currently have to prevent spread of the infection.

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Kennel Cough

Kennel cough is a term loosely applied to a syndrome of canine infectious tracheobronchitis traceable to a wide variety of causative agents. It is characterized by an acute onset of frequent dry, hacking, "honking" cough, sometimes accompanied by discharge from the nose and/or eyes. Causes include a number of viruses and bacteria, the majority of which are routinely included in vaccines. However, there are some causative agents for which a vaccine does not exist, so it is possible for well-vaccinated togs to contract "kennel cough". Transmission is airborn or dog-to-dog, so areas of high concentration such as shelters, kennels, pet shops and commercial breeding kennels are at higher risk.

The incubation period for most pathogens causing tracheobronchitis is 3-10 days, and MOST are no longer contagious after 2 weeks, although Bordatella brochiseptica, the bacterial agent classically associated with "kennel cough" can be shed for up to 3 months.

Most cases of infectious trachobronchitis are caused by multiple agents, and the main concern is to keep it from progressing to pneumonia. Most dogs can weather a bout of "kennel cough" (essentially a doggie cold) and recover without intervention, but medication can make them more comfortable and can prevent disease progression. Cough suppressants may be useful if the cough is so severe that it disrupts sleep, and antibiotics are often given to eliminate the bacterial component and to prevent progression to pneumonia.

If you think your dog has kennel cough, do your best to isolate him/her from other dogs, and know that other dogs in your household will be exposed. Seek veterinary care if the dog has a fever over 103 degrees, has trouble resting because of the cough, is lethargic or is not eating.

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Pneumonia is an infection of the lungs and can be caused by a number of factors. As with most of the respiratory diseases, there can be a number of causative agents which can overlap. Dogs with pneumonia tend to exhibit a deep, moist cough rather than the dry, hacking cough seen with tracheobronchitis, have heavy nasal discharge, and they are generally ill, with fever, lethargy and inappetence being common. Pneumonia can affect a single lung lobe or can be generalized, involving all the lung fields.

Pneumonia can be a primary or secondary disease process, and the causes are far too many to address in this setting. Poor husbandry and plain old neglect is perhaps the underlying cause we will see most often. However, one primary problem that can lead to secondary pneumonia does deserve to be mentioned, as it is more common in large breed dogs. Mega esophagus (which can also be primary or secondary) is a dilation of the esophagus with ineffective esophageal motility which causes food to be regurgitated and can lead to aspiration pneumonia if food particles are inhaled. In severe cases, it is quite obvious--food just falls out every time the dog eats. There is no abdominal effort like you would see with vomiting. However, more subtle cases might result in minor regurgitation which owners may not notice. In either case, the possibility of stomach contents being aspirated exists and can lead to pneumonia.

Regardless of the cause, treatment of pneumonia requires aggressive supportive care, usually in an intensive care unit setting, and administration of appropriate antibiotics. Cultures of fluids obtained from deep in the respiratory tract may be required to help choose the right drugs. Intravenous fluids, oxygen, nebulization and nutritional support are also part of the treatment.