Veterinary advice should be sought from your local veterinarian before applying any treatment or vaccine. Not sure who to use? Look up veterinarians who specialize in poultry using our directory listing. Find me a Vet

Avian Intestinal Spirochetosis

Spirochetosis, Chicken Tick Paralysis, Fowl Spirochetosis, Fowl Tick Fever, Fowl Tick Paralysis, Chicken Tick Fever

Avian intestinal spirochetosis (AIS) is an enteric disease of birds caused by colonization of spirochetal bacteria of the genus Brachyspira in the bird's intestines (specifically the cecum and rectum). There are seven types of Brachyspira that infect birds, however the four main pathogenic (disease-causing) species in chickens include B. intermedia, B. pilosicoli, B. alvinipulli and B. hyodysenteriae. AIS is known to cause mild to moderate, subacute to chronic disease historically in flocks of laying hens and broiler breeders. The severity of the infection depends on the particular strain of Brachyspira, extent of colonization, the chicken's age and overall health and immune status.

Clinical signs

  • Delayed onset of egg production in pullets.
  • Reduced egg production in egg laying hens.
  • Smaller and lighter eggs (decreased egg weight) often with reduced egg shell quality.
  • Frequent changes in fecal consistency.
  • Eggshells are frequently stained with feces.
  • Increased fecal output and amount of water present in feces.
  • Yellowish-brown, mucoid and/or foamy diarrhea with increased lipid content.


Brachyspira can be initially introduced into chicken flocks through wild birds, rodents, insects (such as flies), domestic and feral dogs or cats, other livestock (pigs or horses), other poultry species (ducks, geese, turkeys, pheasants, etc.), and even humans. Ducks in particular, are known to be subclinical carriers of Brachyspira spp., meaning that they are often easily infected but never develop clinical signs of disease, however they will shed the bacteria in their feces. Brachyspira are most commonly spread between flock members through environmental contamination with feces from infected birds. When chickens are exposed to the same environments as infected hosts, they are at risk of becoming infected.

Clinical Signs

Delayed onset of lay
Reduced egg production
Chickens never laying eggs
Reduced egg weight
Wet feces
Yellowish-brown diarrhea
Mucoid and/or foamy diarrhea
Fecal staining of eggshells


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


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.
TiamulinAdministered in drinking water according to manufacturer recommendations. Has been found to be effective at reducing severity of clinical signs related to colonization by certain species of Brachyspira in egg laying hensMJ Woodward et al., 2015



  • Practice good sanitation
  • Clean and disinfect waterers daily, as certain strains of Brachyspira can survive for extended periods of time in water, particuarly at colder temperatures.
  • Do not house chickens and ducks together.
  • Provide chickens with water sources that are inaccessible by ducks, to minimize contamination and spread through water.

Scientific References

Risk Factors

  • Poor sanitary practices
  • Free range chicken flocks
  • Keeping ducks and chickens housed together
  • Letting chickens drink from swimming pools used by ducks.

Also Consider