Enteric Campylobacteriosis in Animals

Campylobacter jejuni, Gram-stained smear of intestine, dog

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Courtesy of Ms. Paula Yant.

Campylobacter spp are thin (0.2–0.8 mcm × 0.3–5 mcm), gram-negative, motile, curved rods that exhibit a characteristic corkscrew darting motility by virtue of their single flagellum. The cells are generally S-shaped or curved, but occasionally they are long (8 mcm) spiral rods. In unfavorable growth conditions, spiral rods undergo a degenerate conversion to coccoid forms. They grow slowly, with a generation time of ~90 minutes, are fastidious, and require enriched medium and microaerobic conditions with increased CO₂ (3%–15% O₂, 3%–10% CO₂, 85% N₂) for growth.

The family Campylobacteraceae consists of three genera associated with animal and human diseases, including Campylobacter and Arcobacter. Certain species are present commensally in animals, which act as reservoirs for infections in humans. The thermophilic Campylobacter spp—namely, C jejuni and C coli—have the highest prevalence and disease impact.

See the table Campylobacter Species That Cause Diseases in Animals for a brief summary of animal diseases caused by different Campylobacter spp.

Initially, Arcobacter spp were considered to be aerotolerant campylobacters. They are implicated in reproductive disorders, mastitis, gastric ulcers, and/or diarrhea in production animals. Arcobacter spp include A cryaerophilus (previously Campylobacter cryaerophilus), A skirrowii, A thereius, and A butzleri.

Campylobacter spp are transmitted via food, water, or the fecal-oral route. Animals serve as reservoir hosts for Campylobacter infections in both animals and humans throughout the world. The predominant ecologic niche for Campylobacter spp is the GI tract of a wide variety of domesticated and wild vertebrates, and zoonotic transmission from animals to humans in meat of animal origin is a food safety issue. Campylobacter spp are also commonly isolated from wild birds, including migratory birds and waterfowl, crows, gulls, and domestic pigeons, which can contaminate the environments of grazing animals. Wild rodents and insects such as flies have also been reported to harbor and transmit C jejuni.

Fecal contamination of the environment provides a ubiquitous source of these organisms under appropriate conditions for their survival. Campylobacter spp can persist for long periods in feces, milk, water, and urine, especially at temperatures close to 4ºC. In adverse conditions, C jejuni jejuni converts to a viable nonculturable form that can be reactivated when ingested.

Human foods documented as contaminated with Campylobacter include chicken, turkey, beef, pork, fish, and milk. Domesticated poultry are the most important reservoir of C jejuni jejuni for humans, causing 50%–70% of cases; chicken meat is the number one source. Like their owners, dogs and cats are commonly infected when they ingest undercooked poultry.

Natural infections with C jejuni jejuni resulting in enteritis have been reported in juvenile macaques, weaning-age ferrets, dogs, cats, and swine. Chickens, rodents, ferrets, primates, rabbits, and pigs have been inoculated experimentally by various routes with C jejuni and subsequently developed enteritis.

Bacterial motility, mucus colonization, toxin production, attachment, internalization, and translocation are among the processes associated with C jejuni jejuni virulence. Infection begins with ingestion of C jejuni jejuni in contaminated foods or water. Gastric acid provides a barrier, and the bacteria must reach the small and large intestines to multiply; C jejuni invades both epithelial cells and cells within the lamina propria. Virulent Campylobacter spp adhere to and invade enterocytes after penetrating the surface mucus layer. They survive in the cytoplasm of enterocytes, extending their intracellular survival by avoiding lysosomal compartments. The pathogenesis of Campylobacter-associated disease involves type IV and type VI secretion systems and toxins, including the virulence factor CDT (cytolethal distending toxin).

C jejuni jejuni produces a spectrum of disease scenarios, depending on the immune status of the host, bacterial virulence, gene expression, and other factors. Infected patients may show signs of systemic illness, may show only GI signs, may be infected and shed the organism transiently but remain clinically normal, or may clear the infection promptly with no signs of illness or shedding. Abdominal pain, fever, diarrhea, blood in feces, and inflammatory cells in feces are the most classic clinical manifestation, demonstrating the inflammatory nature of infection by C jejuni jejuni.

C jejuni jejuni, C coli, C upsaliensis, and C helveticus are the Campylobacter spp that have been associated with intestinal disease in companion animals. C jejuni jejuni causes diarrhea in dogs and cats, which are considered an important source of infection by the bacterium in the human population. Diarrhea is usually acute. Diarrhea lasting 5–15 days is the most common clinical sign in dogs < 6 months old. It may be watery to bloody with mucus and is sometimes stained with bile. Occasionally, diarrhea becomes chronic and may be accompanied by fever and increased WBC counts. Cats < 6 months old commonly have diarrhea, which may be bloody. Some infected cats show no clinical signs. In addition, C jejuni jejuni has been isolated in the vaginal discharge from late-pregnancy abortions in dogs.

In cattle and sheep, Campylobacter spp—including C jejuni jejuni, C fetus fetus, C hyointestinalis hyointestinalis, and C sputorum—can cause enteritis and abortion. However, in studies that compared C jejuni prevalence in healthy cattle and in cattle with diarrhea, the frequency of Campylobacter spp was not notably different, and the role of Campylobacter spp in enteric disease of ruminants remains controversial. Clinically normal cattle can have substantial numbers of Campylobacter, suggesting a possible commensal role for the organism. In a number of studies, cattle checked at slaughter harbored Campylobacter in the gallbladder, large and small intestines, and liver. Fecal shedding of Campylobacter in cattle leads to contamination of milk and beef.

Swine commonly carry C coli and C jejuni jejuni as intestinal commensals, and studies in the US, the Netherlands, Great Britain, and Germany show that more than half of commercially raised pigs excrete the organisms. Current research suggests that Campylobacter spp do not cause clinical disease in pigs,1-3 but increasing antimicrobial resistance of C coli and C jejuni jejuni isolates from swine carcasses and production facilities make the potential contamination of pork an increasing concern for human health.

Birds, including intensively farmed poultry, appear to have higher infection and carrier rates of Campylobacter spp, especially C jejuni jejuni, than other animals. In broilers, the pathogen may colonize the palatine lymphoid tissues and the crop, leading to its extremely rapid transmission through water troughs and the standard fecal-oral route. A not-yet-identified species of Campylobacter has been associated with necrotizing hepatitis in chickens. C jejuni jejuni has been isolated from the small intestines of clinically ill birds, especially psittacines (parrots) and passerines (finches and canaries), with hepatitis, lethargy, loss of appetite, weight loss, and yellow diarrhea. Mortality may be high. Conversely, disease due to Campylobacter spp in wild birds is rare, though they commonly carry the organism.

Campylobacter GI disease has been reported in exotic pets (eg, ferrets, mink, primates, hamsters, guinea pigs, mice, and rats). Although clinical signs vary in these species, they generally include mucoid, watery, bile-streaked diarrhea (sometimes with blood), anorexia, vomiting, and fever. Prolonged infections are possible but uncommon; most infections are self-limiting, with mild clinical signs. In mink, erosive colitis has been associated with C jejuni infection; such infection was reproduced experimentally.

The following Campylobacter spp, several of which are implicated in human diseases, have been isolated from birds, shellfish, reptiles, marine mammals, and production animals without causing disease in the animal hosts:

• C avium

• C hyointestinalis lawsonii

• C fetus testudinum

• C canadensis

• C peloridis

• C insulaenigrae

• C subantarcticus

• C volucris

• C ureolyticus (previously Bacteroides ureolyticus)

Arcobacter spp that infect animals include A cryaerophilus (abortion in production animals), A butzleri (diarrhea in production animals, abortions in cattle, and abortions in pigs), A skirrowii (diarrhea in sheep, abortion in production animals), and A thereius (abortions in pigs). The following species have also been isolated from food animals but are not known to cause disease: A cibarious (chicken meat, piggery effluent), A trophiarum (fattening pigs), and A suis (pork meat). Approximately 11 additional Arcobacter spp are found in shellfish, sewage, seawater, sediments, and salt marsh plants but are not known to cause diseases in animals or humans.

• Presumptive diagnosis: clinical signs, gross and microscopic lesions

• Confirmatory diagnosis: isolation or demonstration of Campylobacter spp by PCR assay and/or other molecular methods

Campylobacter spp can be found in both healthy and diarrheic animals; thus, determination of their role in disease is challenging. A presumptive diagnosis of enteric campylobacteriosis relies on clinical signs coupled with gross and microscopic lesions; confirmation of the diagnosis, however, requires isolation of the causative agent using selective media under microaerophilic conditions.

Fresh fecal samples should be collected and transported to the laboratory preferably on the same day and within at least 2 days for processing. If transport to the laboratory is delayed, maintaining transport media and storage conditions at 4°C produces the best results. Campylobacters are very sensitive to environmental conditions, including dehydration, atmospheric oxygen, sunlight, and increased temperature.

Campylobacters can be quickly outgrown by contaminating microbes during prolonged transport to the laboratory, and isolation of pure colonies for downstream testing can be difficult. Filtration using 0.45-mcm filters can help because campylobacters will pass through.

Enrichment is required for clinical sampling unless material can be transported to the laboratory immediately. When samples are collected in swabs, the use of commercially available transport tubes containing medium, such as Amies, is recommended. The medium can be plain agar or charcoal based. Several media have been described for the transport of fecal specimens, including Cary-Blair, modified Cary-Blair, modified Stuart medium, Campy thioglycolate medium, alkaline peptone water, and semisolid motility test medium. Other media are recommended for isolating those campylobacters specifically associated with reproductive losses.

Arcobacter spp (previously known as aerotolerant campylobacters) can also be associated with human and animal diarrhea and with animal abortions. Arcobacter spp are usually not thermophilic; however, they can be confused with the nonthermophilic Campylobacter spp if aerotolerance is confirmed using standardized suspensions of organisms. Although most cases of human enteritis are attributed to C jejuni jejuni, C coli, C lari, or C upsaliensis, the importance of other species also associated with GI illness may be markedly underdiagnosed as a consequence of inappropriate isolation and identification methods.

PCR-based methods effectively identify infection, especially if cultivation is difficult or if the sample has been somewhat mishandled. However, a positive test is not sufficient evidence to determine causation and must be considered in conjunction with clinical signs.

Differentiation of subspecies can be necessary for identification of important pathogens. Conventional biochemical techniques can be used to make this determination; at present, however, identification relies on molecular tests and/or matrix-associated laser desorption/ionization–time-of-flight (MALDI-TOF) methods.

• Supportive care

• Administration of antimicrobials when necessary, according to susceptibility testing

Clindamycin, gentamicin, tetracyclines, erythromycin, cephalosporins (eg, cephalothin), and fluoroquinolones (eg, nalidixic acid) are effective against C jejuni, C helveticus, and C upsaliensis. C fetus, C hyointestinalis, C mucosalis, and C sputorum are usually resistant to the fluoroquinolones yet sensitive to cephalosporins. C coli are now showing resistance to fluoroquinolones and cephalosporins. Susceptibilities to penicillins and trimethoprim vary across Campylobacter spp. Resistance to the fluoroquinolones, tetracyclines, kanamycin, and some other antimicrobials has been documented among Campylobacter spp, mediated by both chromosomal and plasmid mechanisms.

Campylobacteriosis is considered a zoonotic disease. C jejuni is one of the leading causes of bacterial foodborne human gastroenteritis in the world, and it manifests as self-limiting, watery and/or bloody diarrhea, abdominal cramping, and occasionally fever. Immunocompromised patients may develop a more severe condition, requiring antimicrobial treatment.

Although most zoonotic cases of human campylobacteriosis are associated with consumption of meats, especially chicken, contaminated with this microorganism, transmission from infected dogs can also occur. Prevention should be based on strict hygiene, consumption of well-cooked meat, and avoiding contact with canine secretions.

Some animals remain colonized and become persistent Campylobacter shedders despite treatment with antimicrobials. If the goal of treatment is to decrease the risk of zoonotic transmission to a susceptible household member, antimicrobial treatment alone may be inadequate. Control involves treatment, removal of the patient to a clean environment, and prospective fecal testing to ascertain shedding status; nevertheless, low infective doses and the ubiquitous distribution of the organism pose substantial challenges in the prevention of infection.

• Also see pet health content regarding disorders caused by bacteria in the digestive system in cats and in dogs.