Upper Respiratory Infections
Out of all puppy problems, Upper Respiratory Infections (URI) is one of the most frustrating for both pet owners and veterinarians. There is no easy fix; the issue is likely to be clinical for three to six weeks with treatment, and relapses are common. To understand this disease, we must consider the conditions in which it occurs, its bacterial and viral sources, and our options for prevention and treatment.
Conditions Inside and Outside the Puppy
URI– also called Canine Infectious Respiratory Disease (CIRD) or Infectious Respiratory Tract Disease (IRTD) - is primarily contracted in spaces occupied or visited by many dogs. Boarding houses, groomers, and dog parks, along with many other high traffic locations, provide many opportunities for exposure to URI-causing bacteria and viruses. Known commonly as "Kennel Cough" because of the honking, dry sound made by infected animals, URI is difficult to identify and diagnose because, while it can be caused by both bacteria and viruses independently, most cases involve multiple agents.
Understanding the upper respiratory tract, where URI occurs, helps develop a more complete picture of the disease. The upper respiratory tracts of mammals contains cilia, which are finger-like projections lining the airway. These cilia have a mucus-layer surface that helps catch the "junk" in the air the mammal breathes in. The cilia move together, grabbing bacteria, viruses, and other foreign substances from the air, and forcing them up and out the opening of the airway. This defense is often called the mucociliary escalator, as it constantly moves dirt and infection out of the respiratory area. Coughing and clearing the throat also help remove material from the respiratory surface. We will return to the cilia shortly as we consider the damage bacteria and viruses do to these internal defenses.
Bacterial Causes of URI
Bordetella is one of the few primary pathogens of respiratory tract, meaning it causes issues by itself! Related to Bordetella pertussis, which causes Whooping Cough in people, the Bordetella organism primarily spreads from dog to dog through coughing, but it can also be carried on clothing or shared in water bowls. The organism does not survive long outside the body, and exposure to most detergents, disinfectants, and sunlight kills it.
Bordetella bronchiseptica has several fibrillar appendages or spears that allow it to firmly attach to the surface lining of the nasal passage or respiratory tract after it is inhaled. Once it attaches, it releases a toxin that paralyses the cilia, neutralizing the body's number one defense: the mucociliary escalator. Without the mucociliary escalator, Bordetella can stay alive in the airway for as long as 14 weeks.
A strong strain of Bordetella incubates for two to seven days and is followed by the sudden onset of an unproductive, honking, dry cough. The cough grows worse during exercise, and secondary bacteria including E-Coli, Staph, and Strep species can develop with delayed treatment or with improper antibiotic management. Without proper antibiotic and supportive care, stressed puppies often develop bronchopneumonia from Bordetella infections.
Viral Causes of URI
As we discussed earlier, viral and bacterial infections of the upper respiratory tract often occur together. Parainfluenza is the primary virus that causes URI, but Adeno Type II, Canine Influenza, and Distemper are also causes. After the virus enters the dog's body, it "mows" down patches of cilia, ruining the body's defenses. This now-raw tissue is vulnerable to other organisms, making it easy for bacteria to "gang up" on the puppy. The bacteria attach to the airway surface and reproduce on the damaged cilia layer. This over exposure to pathogens causes reoccurring respiratory problems and makes the infections even more difficult to treat.
Vaccinations provide insurance against disease, and keeping puppies healthy in the face of exposure is the goal. Puppies between four and five weeks old are vaccinated with the Intranasal (IN) vaccine for Kennel Cough. Once vaccinated, the immune system goes looking for the cause of respiratory irritation, even fighting off organisms not included in the vaccine. The IN vaccine for Kennel Cough creates antibodies on the lining of the respiratory tract to assist the mucociliary escalator. These antibodies help bind the bacteria and viruses, preventing them from attaching to wall of the airway. Binding the infectious organisms allows the mucociliary escalator to remove them.
Dogs recently vaccinated with IN Bordetella vaccine have less severe clinical signs when exposed to influenza virus, and this general immunity helps in an outbreak. Vaccination for URI raises the population's resistance and shortens the illness's lifespan if exposure does occur.
Prevention is difficult, but when executed properly, URI can be a minor issue for kennels and other dog-heavy areas. Since we know high exposure to the organism is required to cause an outbreak of coughing, ventilation is the biggest defense for populations of dogs housed together. The concept is simple: dilute the organism with more air, ensuring minimal exposure when an affected dog coughs. Keeping the air moving also helps prevent additional bacteria and viruses from becoming concentrated in the area and making the existing infections difficult to clear.
TreatmentThere is more to treatment than just antibiotics, but antibiotics are important in respiratory infections just like other infections. Effective antibiotics must pursue Bordetella and Mycoplasma.
- Doxycycline is common and very effective against Mycoplasma and Bordetella. The once a day dose is easy to administer and does a good job protecting against the bacteria.
- Azithromycin is the next logical move if Doxycyline doesn't work. This is a reserve measure, as we do not want the diseases to develop bacterial immunity to this very helpful antibiotic. Zithromax works well in severe cases.
- Nose Drops, made with 10 cc saline solution and 100 mg Lincomycin, can be used several times a day to clean junk out of the airway and support the puppy's immune response. The mucus lining is mostly water, and therefore saline nose drops or nebulizers help prevent dehydration of this mucus layer and supports immune function.
- Supportive care cannot be understated. If puppies are nutritionally challenged because they are not eating, they have little immune defense against the invading organism. Puppy Gatorade and high fat high protein baby food are good support for the tiny baby. Parasites will suppress the immune system and complicate prevention and treatment, so it is vital to make sure your puppy is parasite-free.
Respiratory issues are a big concern between weaning and moving the puppies to their "forever home"! Once a puppy is coughing, it can take three to six weeks to totally resolve the issue. Remember to start a prevention plan including ventilation, disinfection, and vaccination, and your care will successfully move a litter from nursing mom to their next best friend!
If you need help, call us at 800.786.4751.
Don Bramlage, DVM, Former Director of Veterinary Services at Revival Animal Health
The materials, information and answers provided through this website are not intended to replace the medical advice or services of your personal veterinarian or other pet health care professional. Consult your own veterinarian for answers to specific medical questions, including diagnosis, treatment, therapy or medical attention.