Campylobacter jejuni is a bacterium that is routinely associated with diarrheal disease in dogs, cat and humans. In the past few years, Campylobacter jejuni has emerged from obscurity as a veterinary pathogen to recognition as a leading cause of enteritis in human beings.

Dogs and cats maintained in kennels and catteries, laboratories, and animal shelters have a much higher likelihood of harboring the organism than privately owned dogs and cats. The organism has been isolated from only 4 percent of clinically healthy dogs and cats. It has been isolated, however, in 21 percent of cats with diarrhea, and 29 percent of dogs with diarrhea. Puppies and kittens are more likely to acquire Campylobacter jejuni and develop diarrhea because of a lack of previous exposure and development of antibodies that protect them from disease.

The principal means of transmission is by fecal-oral spread, especially via food and water. Contaminated meat and unpasteurized milk are other common sources of infection.

The severity of the disease caused by the organism depends on the number of organisms ingested, as well as the immune status of the infected animal. Other intestinal pathogens, such as parvovirus, coronavirus, Giardia, and Salmonella, may play a synergistic role in the disease.

Cats can carry the organism but not show any signs of disease. This is common. If clinical signs do develop, they occur most frequently in dogs younger than 6 months. Stress, such as that due to concurrent disease, hospitalization, pregnancy, or surgery can make animals more susceptible to clinical disease. The main clinical sign of illness is diarrhea, ranging from mild loose feces, to watery diarrhea, to diarrhea containing blood and mucus. The acute form that often affects puppies (and occasionally adult dogs) causes mucus-laden watery diarrhea, often accompanied by decreased appetite and occasional vomiting. Fever may also occur. In some cases, the diarrhea may last several weeks, may be intermittent, and may even last for several months.