There are many infectious agents that can lead to kennel cough, making it a more complicated disease than many people think. Kennel cough can be caused by viruses, bacteria, mycoplasmas, or a combination of the three.
Canine parainfluenza virus is the virus most commonly found in dogs with kennel cough. Canine adenovirus, distemper virus, herpesvirus, and reovirus are also thought be to involved in kennel cough, as well as their own corresponding diseases, making vaccination against them very important.
Although both mycoplasmas (a type of microbe), and several viruses play roles in the causes of kennel cough, the primary agent of infection is the bacteria Bordatella Brontiseptica. In order to understand how Bordatella infects the lungs, first let’s get an understanding how healthy lungs work.
One of the body’s defensive mechanisms used to keep the lungs healthy is called the mucociliary apparatus, which works kind of like an escalator in the upper respiratory tract. The respiratory tract is lined with little hair-like projections called cilia. When we (and dogs) breathe in things that we don’t want in our lungs like bacteria, dust, etc., it gets trapped in mucous and the little cilia beat to work the trapped particles out of the respiratory tract, and eventually they get coughed up and swallowed, preventing them from taking residence in our lungs and causing disease.
Bordatella is a tough little organism that attaches to, and replicates on, the cilia that line the respiratory tract. There they begin to produce toxins that prevent the cilia from beating and prevent the body’s cells from destroying the invading bacteria and fighting off illness, eventually leading to kennel cough. Not only do these conditions allow Bordatella to grow and replicate, but it also paves the way for other infectious agents to come in. If the body is unable to fight off the infection, it can progress into a serious infection of the lungs, in other words: pneumonia.
This scanning electron micrograph (SEM) depicted a number of Gram-negative Bordetella bronchiseptica coccobacilli bacteria.
This organism is commonly found to be the cause of respiratory tract infections in dogs, as well as human beings whose immune system had been compromised including those who are infected by the HIV virus. Courtsey CDC/ Janice Carr