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Avian Intestinal Spirochetosis

Avian intestinal spirochetosis (AIS) is an intestinal disease of chickens caused by infection with the spirochete Brachyspira. The pathogen is commonly found in adult chickens with free range or pasture access worldwide. The most frequent Brachyspira species isolated from chickens are B. intermedia and B. pilosicoli.

Clinical signs of Avian Intestinal Spirochetosis

The most commonly reported clinical signs observed in chickens infected with Brachyspira include:
  • Persistent diarrhea, which may be yellowish brown to caramel colored, mucoid and/or foamy, with increased lipid content. Feces are often smeared on the feathers around the chicken's cloaca, which is commonly referred to as “pasted vent”.
  • Delay in onset of egg laying in pullets. Decreased egg production in adults.
  • Actively laying hens produce smaller and lighter eggs with pale yolks. The egg shells are often contaminated with feces.
  • Progeny of infected breeder chickens may be weak and underweight.

Transmission of Avian Intestinal Spirochetosis

Brachyspira are initially introduced into chicken flocks through pigs, wild birds, rodents, insects, domestic and feral dogs or cats, other livestock, other poultry species, and even humans. Pigs are the main hosts for Brachyspira species, although ducks can also be subclinical carriers. Brachyspira are spread between flock members through contamination of the soil, water, and/or feed with feces from infected birds. When chickens are exposed to the same environments as infected hosts (especially pigs), they are at risk of becoming infected.

Clinical Signs

Delayed onset of lay
Reduced egg production
Laying smaller, lighter, or poor shell quality eggs
Caramel colored, frothy feces
Fecal staining of eggshells


  • History
  • Clinical signs
  • Fecal exam
  • PCR assay
  • Bacterial culture
  • Necropsy

Reported Cases

  • Case 1: Acute septicemic spirochetosis in a Owl Acute septicemic spirochetosis was diagnosed in an adult male northern spotted owl found dead in Kittitas County, Washington, USA. Gross necropsy findings included marked enlargement of the liver and spleen and serofibrinous deposits on the serous membranes lining the body cavities and the pericardial and perihepatic sacs. Microscopic observations included macrophage infiltration in the liver and spleen with mild thrombosis and multifocal necrosis, as well as hemorrhage and acute inflammation in the choroid plexus of the brain. No viruses or pathogenic bacteria were isolated from brain, liver, or spleen, and no parasites were found in blood smears or impression smears of the liver. Chlamydial culture attempts were unsuccessful and no chlamydial antibodies were detected in serum. In silver-stained microscopic sections and by transmission electron microscopy of liver, numerous long, thin, spiral-shaped bacteria were seen in the liver, spleen, cerebral ventricles, and within blood vessels in many organs. The organism was identified as a member of the Borreliagenus by sequence analysis of the PCR-amplified 16S rRNA gene. Ref

  • Case 2: Cecal spirochetosis in a Chickens Cecal spirochetosis in chickens has been associated with enteric disease and reduced egg production in the United States and Europe. This report describes spirochete overgrowth of cecal mucosa in chickens from a flock of 100,000 commercial layers experiencing diarrhea and a 5% drop in egg production. Spirochetes were demonstrated in the ceca by darkfield and light microscopy. Apical surfaces of cecal enterocytes were covered by a dense layer of spirochetes aligned parallel to each other and perpendicular to the mucosal surface. Weakly beta-hemolytic, indole-negative spirochetes were isolated from the ceca on BJ media under anaerobic conditions at 42 C. Ref

  • Case 3: Cecal spirochetosis and typhlitis in a Turkey Spirochetes that were identified as Brachyspira pilosicoli were present in the ceca of 7.5- to 18-wk-old turkeys with cecal spirochetosis and typhlitis. The identity of B. pilosicoli was confirmed on the basis of ultrastructural morphology of the cecal epithelium adherent microbes, immunohistochemical staining with a Brachyspira genus-specific monoclonal antibody, and amplification of a B. pilosicoli species-specific 16S ribosomal RNA (rrs gene) sequence by using the polymerase chain reaction and DNA obtained by laser-capture microdissection of the epithelium-adherent microbial fringe. Ref

  • Case 4: Spirochetosis (enteritis) in a Chickens A flock of 75 gamefowl chickens in California started showing signs of weakness, greenish diarrhea, pale combs, and increased mortality. The disease persisted for several months. A necropsy was performed on two 6-month-old game hens which revealed mucoid enteritis with greenish, bile-stained intestinal contents. The spleens were stippled and slightly enlarged (considered a main sign of spirochetosis in chickens). Venous blood samples appeared pale and thin. Ref

  • Case 5: Spirochetosis (intestinal) in a Chickens A flock of 100,000 thirty-week-old commercial Leghorn hens started developing wet droppings and fecal staining of the feathers around the vent. The ceca droppings were light brown, frothy fluid. The chickens were in small battery cages, and they had no access to the outside environment. Mice and humans were possible routes of infection. Ref

  • Case 6: Spirochetosis (intestinal) in a Chickens Cecal samples from laying chickens from 25 farms with a history of decreased egg production, diarrhea, and/or increased feed conversion ratios were examined for anaerobic intestinal spirochetes of the genus Brachyspira. Seventy-three samples positive in an immunofluorescence assay for Brachyspira species were further examined using selective anaerobic culture, followed by phenotypic analysis, species-specific PCRs (for Brachyspira hyodysenteriae, B. intermedia, and B. pilosicoli), and a Brachyspira genus-specific PCR with sequencing of the partial 16S rRNA gene products. Brachyspira cultures were obtained from all samples. Less than half of the isolates could be identified to the species level on the basis of their biochemical phenotypes, while all but four isolates (5.2%) were speciated by using PCR and sequencing of DNA extracted from the bacteria. Different Brachyspira spp. were found within a single flock and also in cultures from single chickens, emphasizing the need to obtain multiple samples when investigating outbreaks of avian intestinal spirochetosis. Ref

  • Case 7: Spirochetosis (intestinal) in a Chickens DNA was extracted from fecal samples collected from each of 21 flocks of laying hens >40 wk of age in Pennsylvania, and this material was tested for B. intermedia and B. pilosicoli using a duplex PCR. Negative samples also were tested using a Brachyspira genus-specific PCR. The consistency of the feces was observed, and manure handling systems and medication histories were recorded. Brachyspira intermedia was detected in 662 (63.1%) samples from 17 (81%) flocks, with a within-flock prevalence of 10%–100%. Brachyspira pilosicoli was detected in 112 (10.7%) samples from 5 flocks (23.8%), with a within-flock prevalence of 8%–82%. Four of the flocks had both pathogenic species present, three had no pathogenic species detected, and two had no Brachyspira species detected. Nine flocks had many fecal samples with a wet appearance and/or a caramel color, and all of these were colonized with one or the other of the two pathogenic species. Nine of 12 flocks with manure that was mainly dry also were colonized. Differences in colonization rates between flocks with or without wet manure were not significant. Colonization with pathogenic Brachyspira species, and particularly B. intermedia, occurs very commonly in layer flocks >40 wk of age in Pennsylvania. Ref


Supportive careIsolate the bird from the flock and place in a safe, comfortable, warm location (your own chicken "intensive care unit") with easy access to water and food. Limit stress. Call your veterinarian.
Tiamulin (Denagard)12.5-25 mg/kg body weight PO q24h for 3 to 5 daysM Woodward et al., 2015; C Stephens et al., 2010; B Speers; D Burch et al., 2007
Lincomycin20 mg/kg body weight PO q24h for 5 daysC Stephens et al., 2010
Cinnamon (Cinnamomum verum)Reduction of Brachyspira colonization in young pullets was obtained, in a curative way, in an in vivo study using feed supplemented with coated trans-cinnamaldehyde at a dose of 500 mg/kgM Verlinden et al.,2013; F Omonijo et al., 2017
Probiotics (Lactobacillus reuteri)When added to drinking water of hens it provided protection against infection with Brachyspira .L Mappley et al., 2013



  • Not housing pigs and chickens together, or keeping chickens on land which was previously used by pigs.
  • Practice good sanitation
  • Clean and disinfect waterers daily.
  • Minimize attraction of rodents.

Scientific References

Age Range

Risk Factors

  • Environments which previously housed pigs.
  • Keeping pigs on the same property as chickens.
  • Poor sanitary practices
  • Free range chicken flocks
  • High populations of rodents.

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