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 adult animals, signs resolve on their own within a few days, though the bacteria may persist in the gut for weeks or months. In young puppies and kittens, bloody diarrhoea with vomiting or dullness overlaps with more serious infections such as parvovirus, and small animals can become dehydrated within a day or two. Campylobacter is also a zoonosis. Campylobacter jejuni and Campylobacter upsaliensis carried by dogs and cats can infect people by the faecal-oral route, when hands become contaminated from faeces, bedding or the coat of an affected animal. Between 2016 and 2018 an outbreak in the United States linked more than a hundred human infections to contact with puppies. People with a weakened immune system tend to be at greater risk of severe illness, and young children and older people may also be more vulnerable. 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 a few days of exposure 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. In very young or small animals, fluid lost through diarrhoea and vomiting can lead to dehydration within a day or two. In unvaccinated puppies, bloody diarrhoea with vomiting can also be caused by parvovirus, which can progress to collapse within 24 to 48 hours, and the appearance of the stool does not distinguish the two. 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 and pass to the people in it. 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
Diagnosis typically begins with a detailed history of the onset and character of the diarrhoea, recent environmental changes, exposure to other animals, and any concurrent signs such as vomiting or lethargy. Physical examination may reveal mild abdominal discomfort or dehydration, though many animals appear otherwise well. When campylobacteriosis is suspected, faecal testing becomes the central tool, though the pattern of clinical signs and the animal's age and environment often provide important context before any laboratory result is available.
Faecal culture
Faecal PCR
Faecal cytology
Faecal flotation and direct smear
Haematology and biochemistry
Options & trade-offs
Management often combines supportive care to ease symptoms and maintain hydration with measures to reduce bacterial load or inflammation. The approach taken reflects the severity of signs, the animal's overall health, and practical considerations such as the presence of other pets or vulnerable individuals in the household. Different combinations work for different animals, and the balance between intervention and allowing time for self-resolution varies case by case.
Supportive care and dietary management
Many animals recover with rest, access to fresh water, and a temporary shift to a bland, easily digestible diet such as cooked chicken and rice or a prescription gastrointestinal formula. Small, frequent meals can reduce the workload on an inflamed gut, and gradual reintroduction of the usual diet helps prevent relapse. In cases of significant fluid loss, subcutaneous or intravenous fluids may be given to restore hydration and electrolyte balance.
Trade-offs: This approach avoids the use of antibiotics and allows the immune system to clear the infection naturally, but it requires time and may not be sufficient in animals with severe inflammation, marked dehydration or signs of systemic illness. Close monitoring is needed to ensure signs are improving rather than worsening.
Antimicrobial therapy
European guidelines on acute diarrhoea in dogs advise against antibiotics for mild or moderate disease, including diarrhoea that contains blood, because trials have found no clinically relevant benefit. A positive Campylobacter test on its own is not generally regarded as a reason to treat, since many healthy animals carry the organism. Antibiotics tend to be reserved for animals that are severely unwell, septic or immunocompromised. Where treatment is aimed at Campylobacter itself, a macrolide such as erythromycin is often used, and treating a positive result does not reliably stop the animal from shedding the bacteria.
Trade-offs: Campylobacter can carry resistance to commonly used antibiotics, and treatment does not guarantee elimination of the bacteria from the gut. Antibiotic use may also disrupt the normal intestinal flora, potentially prolonging recovery in some cases or contributing to resistance patterns in the wider microbial community.
Probiotics and microbiome support
Probiotics containing strains such as Lactobacillus or Enterococcus are sometimes given to help restore balance to the gut flora and compete with pathogenic bacteria for attachment sites. These supplements may be started during or after the acute phase of illness and continued for several weeks.
Trade-offs: Evidence for efficacy varies by product and strain, and not all probiotics survive passage through the stomach or establish in the colon. Some animals experience no measurable benefit, whilst others show faster resolution of loose stools and reduced recurrence.
Environmental hygiene and isolation
Reducing faecal contamination of the environment through prompt removal of stools, disinfection of food and water bowls, and temporary separation of affected animals from others can limit transmission within a household or group. Chlorine-based disinfectants or heat can inactivate Campylobacter on hard surfaces.
Trade-offs: Hygiene measures are labour-intensive and may not be fully achievable in outdoor or shared environments. Even with rigorous cleaning, reinfection can occur if other animals continue to shed bacteria intermittently or if the source of infection has not been identified.
Monitoring and reassessment
In adult animals that remain bright, keep eating and drinking, and have mild diarrhoea without vomiting, observation without antibiotics allows time to see whether signs resolve, as they often do within several days. Young puppies and kittens, and animals of any age with repeated vomiting, blood in the diarrhoea alongside dullness or weakness, reduced drinking, or pale or tacky gums, are a different picture. These features can accompany dehydration, parvovirus in unvaccinated puppies, or bacteria entering the bloodstream, and in young animals the picture can change within 24 to 48 hours. None of these can be separated from uncomplicated campylobacteriosis at home, and a positive Campylobacter test does not exclude them.
Trade-offs: This approach minimises unnecessary medication but requires owners to be comfortable with a degree of uncertainty and to recognise when signs are not improving. It suits adult animals with mild signs and good overall health. It is poorly suited to young, small or unvaccinated animals, and to any animal with vomiting, dullness or blood in the diarrhoea, where dehydration or a more serious infection cannot be excluded without examination and testing.
Common misconceptions
"A positive test for Campylobacter means the bacteria are definitely causing the diarrhoea."
Many healthy dogs and cats carry Campylobacter in their intestines without ever showing signs of illness, and the bacteria can be detected incidentally when testing is performed for other reasons. A positive result in an animal with diarrhoea indicates the organism is present, but does not confirm it is the sole or primary cause, particularly if other pathogens or stressors are also present. The clinical context—age, history, severity of signs—often matters more than the test result alone.
"Once the diarrhoea stops, the infection is gone and the animal is no longer contagious."
Clinical recovery often precedes microbiological clearance, and many animals continue to shed Campylobacter intermittently for weeks or months after symptoms resolve. This means an apparently healthy animal can still pass bacteria to other pets or to people handling contaminated faeces, bedding or the animal itself. The duration of shedding varies widely between individuals, and because shedding can be intermittent, a negative test does not reliably confirm that the infection has cleared.
"Antibiotics will always clear the infection and prevent future episodes."
Whilst antibiotics can reduce bacterial numbers and shorten the period of active shedding, they do not reliably eliminate Campylobacter from the gut, and reinfection or relapse can occur if the animal is re-exposed or if environmental contamination persists. Resistance to commonly used drugs is increasingly recognised, and some strains may not respond to treatment at all. In many cases, spontaneous resolution occurs without antimicrobial intervention.
Related conditions
Salmonellosis
Salmonellosis shares many clinical features with campylobacteriosis — both are bacterial infections that can cause acute diarrhoea with mucus or blood, particularly in younger animals or those with compromised immunity. The two conditions can be difficult to distinguish based on signs alone, and in some cases both organisms may be present in the same animal.
Tritrichomonas Foetus in Cats
Tritrichomonas foetus in cats causes persistent large-bowel diarrhoea with mucus and sometimes blood, a pattern that overlaps with what may be seen in campylobacteriosis. Both organisms can colonise the intestine without causing signs in all animals, and both are more likely to cause symptoms in younger individuals or group-housed cats.
Gastroenteritis in Dogs
Gastroenteritis in dogs is a broad term that encompasses many causes of intestinal inflammation, including bacterial infections such as campylobacteriosis. When a dog presents with sudden-onset diarrhoea, vomiting, and reduced appetite, campylobacteriosis is one of several possible underlying causes that may be considered during investigation.
Canine Parvovirus
Canine parvovirus in young, unvaccinated dogs can cause foul-smelling, bloody diarrhoea with vomiting that overlaps with campylobacteriosis. Signs can progress from dullness and poor appetite to vomiting and bloody diarrhoea within 24 to 48 hours, severely affected puppies can collapse with shock, and the two conditions cannot be told apart without laboratory testing.
Animals with recurrent or persistent diarrhoea may benefit from broader investigation into other causes of intestinal inflammation, including food sensitivities, parasitic co-infections, or conditions such as inflammatory bowel disease. Understanding the interplay between gut flora, immune function, and environmental stressors can provide useful context for long-term management. Because dogs and cats can pass Campylobacter to people through faecal contamination of hands and surfaces, the household matters as well as the animal. Young animals and those with diarrhoea are more likely to be shedding the organism, and people with a weakened immune system, young children and older people tend to be more vulnerable to severe illness. Handwashing after handling the animal, its bedding or its faeces lowers the chance of spread, and shedding can continue after the diarrhoea has stopped.
Last reviewed: 13 September 2026 · Dr Alastair Greenway MRCVS