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Cryptosporidiosis is a parasitic infection caused by protozoan parasites of the genus Cryptosporidium. It manifests as a respiratory infection, urinary tract infection, and/or gastroenteritis. The majority of cases of cryptosporidiosis in chickens are caused by C. baileyi and C. meleagridis, and rarely C. galli and C. parvum. C. baileyi can cause mild to severe gastroenteritis or respiratory infections, whereas C. meleagridis mainly causes gastroenteritis. Sometimes birds can be infected with C. parvum or C. galli without showing any signs of infection. C. parvum is the only strain of cryptosporidium capable of causing infection in humans.

Transmission occurs through the ingestion of Cryptosporidium oocysts that are passed in the faeces of an infected host. Cryptosporidium does not reproduce outside of a host, and ooysts are infectious immediately upon being excreted in feces. Infection results from the ingestion or inhalation of sporulated oocysts in contaminated water, feed, bedding, and dust. Cryptosporidium infect a wide range of host species, including humans, other mammals, birds, reptiles, and fish. The infectious dose is low. Chickens don't need to ingest very many to cause an infection in a healthy bird. Infected birds will shed Cryptosporidium oocysts in their feces for up to 60 days after they have recovered.

Oocysts are capable of surviving outside the chicken for long periods of time (often greater than 6 months duration) in cool, moist environments, especially water sources. Humans often become infected with Cryptosporidium through ingestion of water in public swimming pools and drinking water.


Cryptosporidium spp. can be detected sometimes in fecal tests.

Clinical Signs

Weight loss
Ruffled feathers
Nasal and eye discharge
Swollen sinuses
Difficulty breathing
Extending neck
Reluctance to move
Increased respiratory sounds (rales)
Undigested food in droppings


  • Cytology
  • Fecal test
  • Acid-fast staining
  • Direct fluorescent antibody [DFA]


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.
Paramomycin100 mg/kg administered orally every 12 hoursK Marx



  • Good sanitary practices
  • Place water sources higher up to help prevent feces from contaminating the water source.
  • Prevent birds flying overhead from contaminating water sources with their feces.

Scientific References

Risk Factors

  • Keeping birds in a dirty, unsanitary environment.
  • Ingestion of untreated or fecal contaminated drinking water.