by Jennifer Coates, DVM
If you spend much time on websites dedicated to canine nutrition, you’re bound to run into a debate over Salmonella.
In general, veterinarians have considered salmonellosis (disease caused by infection with Salmonella bacteria) to primarily be a problem in dogs that are fed raw or undercooked meats. However, this summer’s Diamond pet food recall shows that to protect both dogs and people, all owners need to be informed about the disease, regardless of what they feed their pets.
Canine salmonellosis is an interesting condition.
Many healthy, adult dogs that become infected never show any clinical signs – dogs are actually quite resistant to the disease. These individuals are still problematic, however, because they are capable of infecting people and other animals when they shed the bacteria in their feces.
It’s the very young, very old, or dogs that are stressed or have compromised immune systems that are at the greatest risk for developing salmonellosis.
Let’s take a look at what happens in a dog’s body when its natural defenses cannot keep Salmonella under wraps.
Salmonella bacteria that survive their trip through the acid environment of the stomach attach to the tips of intestinal villi, the tiny finger-like projections, covering the inner surface of the small intestine that greatly increase the organ’s surface area and absorptive capacity.
From there, they invade deeper into the lining of the intestine and multiply.
This process, along with the inflammatory response that results, leads to tissue injury, death, and sloughing, thereby reducing the intestine’s absorptive surface area, causing liquid to leak through the intestinal wall, and disrupting the motility of the intestinal tract.
The bacteria can survive in and be shed from a dog’s intestinal lining for at least three to six weeks after infection has occurred.
Salmonella can also hide out in cells within intestinal lymph nodes, the spleen, or liver.
When these “carrier” dogs become stressed or immunocompromised, the bacteria can take advantage of the situation and become active again, producing illness and/or fecal contamination.
The most common clinical signs associated with a Salmonella infection that is limited to a dog’s digestive system are diarrhea (often containing mucus or blood), fever, lethargy, loss of appetite, dehydration, weight loss, and abdominal pain.
If damage to the intestinal lining is significant enough, Salmonella bacteria have direct access to a dog’s blood stream.
This can lead to septicemia (the presence of bacteria within the blood) and endotoxemia (the release of bacterial toxins into the blood stream when some types of bacteria die or are damaged).
These potentially life threatening conditions produce symptoms such as pale mucous membranes, rapid breathing, a rapid heart rate, collapse, seizures, shock and death, often as a result of disseminated intravascular coagulation (a condition during which blood fails to clot or clots inappropriately throughout the body) and multiple organ failure.
So, even though Salmonella infections rarely cause disease in healthy dogs in the prime of their lives, its potential effect on puppies, older dogs, sick animals, and people is so catastrophic that all dog owners should pay the bacteria the respect it deserves.
Dictionary of Veterinary Terms: Vet-speak Deciphered for the Non-veterinarian.
Dr. Coates has recently joined the PetMD team and she is now writing for the Fully Vetted column; great blog, do check it out.
also writes short stories that focus on the strength and
importance of the human-animal bond and freelance articles relating to
a variety of animal care and veterinary topics. Dr. Coates
lives in Fort Collins, Colorado with her husband, daughter, and
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