CONDITION
Campylobacteriosis
Campylobacteriosis is an infection of the digestive tract caused by bacteria in the Campylobacter genus. These bacteria can settle in the intestines and cause inflammation, leading to diarrhoea that may contain mucus or blood. Many dogs and cats carry Campylobacter without showing any signs, but younger animals, those with other health conditions, or those under stress may develop symptoms. Owners most often notice loose or watery stools that appear suddenly, sometimes with a distinctly foul smell or visible streaks of blood. The diarrhoea may be accompanied by a reduced appetite, occasional vomiting, or signs of mild abdominal discomfort. In many cases, signs resolve on their own within a few days, though the bacteria may persist in the gut for weeks or months. This page explores what patterns tend to raise suspicion for campylobacteriosis, what happens in the intestinal lining during infection, how the condition is investigated through faecal testing, and what approaches exist for managing symptoms and supporting recovery.
Why this matters now
Campylobacteriosis tends to appear most often in puppies and kittens under six months of age, whose immune systems are still maturing and whose gut flora may be less stable. Animals living in multi-pet households, kennels, or shelters face higher exposure, as the bacteria spread readily through faecal contamination of shared spaces. Stress from weaning, rehoming, travel, or concurrent illness can also create conditions in which dormant carriage shifts into active infection. While any dog or cat can be affected, those with weakened immune function—whether from age, underlying disease, or immunosuppressive medication—are more likely to develop symptoms.
In most cases, diarrhoea begins within two to five days of bacterial colonisation and may persist for several days to a week before gradually resolving. The severity varies widely: some animals experience only a brief period of soft stools, while others develop more pronounced inflammation with mucoid or bloody diarrhoea. Even after clinical signs fade, many animals continue to shed bacteria intermittently for weeks or months, meaning the infection can cycle through a household or group. Reinfection or flare-ups may occur if the animal is exposed again or if stressors compromise the gut lining.
Signals & patterns
Early signals
Sudden onset of loose stools
Diarrhoea often appears abruptly, shifting from normal consistency to soft or watery within a day or two. The change may be mild at first, with stools that are simply less formed, or more dramatic, with frequent pooling liquid.
Mucus in the stool
Owners may notice a clear or yellowish jelly-like coating on the faeces, which reflects inflammation and increased mucus production in the lining of the large intestine. This can appear early, even when the stool itself is only slightly soft.
Uncharacteristic odour
The smell of the diarrhoea can be distinctly foul or sour, often described as sharper or more pungent than usual. This reflects changes in the bacterial population and the breakdown products of inflammation in the gut.
Mild loss of appetite
Some animals become less interested in food or eat more slowly than usual. This can be subtle—finishing a meal over time rather than eagerly, or leaving a small portion uneaten—and may coincide with low-grade nausea or abdominal discomfort.
Later signals
Streaks or flecks of blood
As inflammation deepens, small amounts of fresh red blood may appear on the surface of the stool or mixed within it. This indicates erosion or ulceration of the intestinal lining, particularly in the colon, where Campylobacter tends to colonise.
Frequent straining or urgency
The animal may adopt a posture to defaecate repeatedly, producing only small amounts of mucus or liquid each time. This pattern, known as tenesmus, reflects irritation and spasm in the lower bowel and can be distressing for the animal.
Occasional vomiting
Some animals vomit intermittently, particularly if inflammation extends into the upper digestive tract or if nausea develops secondary to toxins or discomfort. Vomiting tends to be less consistent than the diarrhoea and may come and go over a few days.
Click to read about the biological mechanisms
How this is usually investigated
Options & trade-offs
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