Infection of the intestinal tract with Campylobacter jejuni and other Campylobacter spp is common in poultry and waterfowl but is not typically associated with clinical signs of disease. Exceptions are C hepaticus and C bilis, which have been reported to cause spotty liver disease in layer chickens and decrease egg production. Bacterial isolation remains the standard method for detection, but PCR assay is increasingly used for diagnosis. No treatment is needed for most avian Campylobacter infections, but C hepaticus outbreaks may be treated by antimicrobials. Some poultry Campylobacter species, particularly C jejuni, are a common source of infections in humans.
Campylobacteriosis does not commonly cause clinical signs in poultry and other birds. However, Campylobacter hepaticus and C bilis cause spotty liver disease in layer chickens and are associated with decreased egg production.
Campylobacteriosis is a noteworthy enterocolitis of humans. Campylobacteriosis is frequently acquired through consumption of undercooked poultry meat contaminated with Campylobacter jejuni. It can also be acquired from handling backyard poultry and from diarrheic companion animals and contaminated water.
Etiology of Campylobacteriosis in Birds
Bacteria of the genus Campylobacter are motile, curved, microaerophilic, gram-negative bacilli. Campylobacter colonize the intestine of chickens, turkeys, and waterfowl but are generally nonpathogenic in birds.
C jejuni is the predominant species associated with foodborne infection derived from poultry; however, C coli and C lari have also been implicated in some cases and can also be recovered from the intestinal tract of birds.
Some strains of C jejuni have been reported to cause enteritis and death in newly hatched chicks and poults, but administering isolates of C jejuni to chickens has not reproduced the syndrome. However, novel species of Campylobacter, C hepaticus and C bilis, have been identified as the cause of spotty liver disease in layer chickens.
C hepaticus is also associated with spotty liver disease of breeder chickens and has been identified as the etiologic agent of the disease formerly known as avian vibrionic hepatitis.
Epidemiology of Campylobacteriosis in Birds
Columbiformes and domestic and free-living Galliformes and Anseriformes birds are natural reservoirs of the human pathogenic Campylobacter spp (C jejuni, C coli, and C lari) and other poorly defined Campylobacter spp.
Many commercial broiler and turkey flocks harbor C jejuni, although the prevalence can vary from 0% to 100% depending on season (lowest in fall and winter and highest in summer) and age of the birds. C jejuni has been found in all areas of commercial poultry production.
Although young birds can be experimentally infected by Campylobacter, the organismis normally undetected in commercial operations until birds are 3 weeks old.
Environmental contamination with bird feces is probably the most common source of infection for dissemination of both C jejuni and C hepaticus; however, some species of Campylobacter can be transmitted vertically, either on the surface of eggs or by transovarial transmission.
Insects, fomites, and contaminated water and feed can transmit Campylobacter to young birds. Commercial poultry litter can remain infective for long periods, subject to at least a 10% moisture level and neutral pH. In many clinical cases of spotty liver disease, birds had a history of access to muddy puddles; nonchlorinated water derived from a dam, river, or shallow well should be regarded as a possible source.
Rats, mice, wild birds, darkling beetles, and houseflies can be transmission sources for flocks; equipment and footwear contaminated with feces from an infected source may also serve as vehicles of transmission. Young chicks and poults are easily colonized when exposed to C jejuni and can excrete the organism in the feces for their lifetimes.
Once C jejuni has been introduced into the environment, rapid transmission within the flock occurs, with subsequent colonization of a high proportion of exposed breeders, commercial-meat, or laying-strain poultry.
C jejuni has been isolated from the reproductive tracts of hens and roosters, suggesting vertical transmission in some cases. Therefore, biosecurity may not be adequate to control transmission of Campylobacter until it has been eradicated from parent flocks.
Clinical Findings of Campylobacteriosis in Birds
Key clinical signs, in addition to multifocal necrotic hepatitis, include egg production losses and increased flock mortality rate.
Birds challenged with Campylobacter jejuni generally do not exhibit clinical signs of disease. Many birds are colonized with Campylobacter spp early in life with no associated clinical signs or lesions.
Lesions
Challenged chicks may exhibit distention of the jejunum, disseminated hemorrhagic enteritis, and in some cases, focal hepatic necrosis. However, infected flocks seldom exhibit these lesions, increased mortality rates, or decreased feed conversion.
Birds challenged with C hepaticus exhibit focal hepatic necrosis in varying levels of severity. Infected layer flocks exhibit spotty livers, increased mortality rates approaching 15%, and decreased egg production. Death can occur rapidly, suggesting the involvement of acute septicemia and toxemia.
Diagnosis of Campylobacteriosis in Birds
Clinical signs (for C hepaticus)
Bacteriologic culture or PCR assay
Diagnosis of campylobacteriosis in birds is based on clinical signs and detection of the pathogen. Diagnosis of spotty liver disease is done by clinical signs and culture of C hepaticus from liver lesions.
There are no reliable serologic tests for Campylobacter in avian species.
Detection of colonized birds can be done by bacteriologic culture of fecal samples. However, culture of the organism is difficult because it is susceptible to a number of the antimicrobials used in common Campylobacter enrichment media and selective agar.
C jejuni can be cultured on many commercially available media, but the strategy includes direct isolation or a broth enrichment followed by isolation on selective agar.
Thermophilic Campylobacter spp should be cultured at 42°C under humid, microaerophilic conditions (85% nitrogen, 10% carbon dioxide, and 5% oxygen) for 48 hours. Some strains require a hydrogen-enriched atmosphere (5%).
Campylobacter spp can be identified by biochemical testing, matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry, or PCR assay.
The nalidixic acid susceptibility test is no longer reliable because of the increasing prevalence of fluoroquinolone-resistant C jejuni. Various genotyping methods such as pulsed-field gel analysis and whole genome sequencing can distinguish various C jejuni isolates.
C hepaticus samples should consist of liver or bile; bacteriologic culture using feces or cecal droppings is not reliable for diagnosis.
Cultivation can be challenging because commercial enrichment broths and selective agar contain selective agents that are inhibitory to many C hepaticus strains.
For culture, bile can be plated directly onto regular 5% sheep blood agar or Brucella blood agar with 5% horse blood and incubated in microaerophilic conditions at 42°C. Livers can be enriched in modified Preston broth, incubated at 37°C in microaerophilic conditions for up to 7 days, then isolated on Brucella blood agar with 5% horse blood.
The selective filtration method can also be used for contaminated organ samples: a 1/10 diluted sample is allowed to penetrate a sterile filter (pore size, 0.45 mcm) placed on the surface of a blood agar plate. After the liquid is absorbed into the plate, the filter is removed and incubated microaerobically. Identification can be done by biochemical testing, PCR assay, or MALDI-TOF.
Control and Prevention of Campylobacteriosis in Birds
Improved biosecurity and hygiene
Antimicrobial treatment (for C hepaticus)
No effective vaccine
Because Campylobacter jejuni is not found as a specific pathogen under commercial conditions, treatment of poultry flocks is not a consideration. If C jejuni is considered a problem in companion bird aviaries or in exotic species, antimicrobials could be administered in drinking water in an attempt to eradicate it.
Because of the zoonotic risk associated with C jejuni and its ability to rapidly develop antibiotic resistance, antibiotics should be administered with caution in companion birds.
Spotty liver disease outbreaks caused by C hepaticus may be treated with antibiotics such as chlortetracycline and lincomycin; however, development of resistance and egg withholding time for layers are important concerns.
Fluoroquinolones and erythromycins are the classes of antimicrobials used to treat humans for campylobacteriosis.
Preharvest prevention of Campylobacter infection in commercial poultry is based on strict biosecurity, decontamination of housing between successive flocks, exclusion of rodents and wild birds, and insect eradication.
Chlorination of drinking water to 2 mcg/mL and operation of farms on a strict all-in/all-out management basis occasionally decreases the prevalence of infection. Innovative methods of prevention, such as competitive exclusion, bacteriophage therapy, bacteriocins, and vaccination, are under intensive investigation.
Withholding feed from broilers and turkeys for at least 12 hours before slaughter and thoroughly decontaminating transport coops and modules decrease fecal contamination and lower the level of C jejuni introduced into processing plants.
Zoonotic Risk of Campylobacteriosis in Birds
Campylobacter jejuni is a major source of foodborne enteritis in humans; contaminated undercooked poultry is responsible for most cases. The condition was recognized in the mid-1970s, and the importance of the organism has become apparent with improved methods of isolation and identification.
Other sources, such as nonchlorinated ground water, unpasteurized milk, young diarrheic pets, and contaminated beef and pork products are also responsible for infection of humans.
In commercial poultry processing, improved washing of carcasses, use of counter-flow mechanical advances in scalding, elimination of immersion chillers, and reduction in manual handling by installation of advanced automated equipment has decreased C jejuni contamination on poultry meat.
Chemical disinfectants in the washes, such as chlorine; peracetic acid with hydrogen peroxide; trisodium phosphate, glutaraldehyde, and succinic acid; and organic compounds such as lactic and acetic acids may also effectively decrease C jejuni on poultry carcasses in the processing plant.
Bacteriophages and bacteriocins may also be useful. However, regulations regarding the biological sanitizers that can be used in processing plants are in flux.
Concurrent measures in food preparation, hygienic storage, handling, and preparation are necessary to prevent contamination of prepared foods, work surfaces, and utensils by raw poultry and other meats. The risk of foodborne C jejuni infection can be decreased through cooking poultry to achieve a core temperature of 74°C for 1 minute.
Key Points
Campylobacter is a major cause of enteritis in humans, frequently acquired through consumption of undercooked C jejuni–contaminated poultry meat and other foods.
Many Campylobacter spp colonize the intestine of poultry and waterfowl but are generally nonpathogenic to birds.
C hepaticus and C bilis are the causative agents of spotty liver disease in layer chickens.
