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Other Names: Avian Cryptosporidiosis

Cryptosporidiosis is the name of the disease caused by infection with protozoan parasites of the genus Cryptosporidium. Cryptosporidial parasites predominately infect the epithelium of the intestinal tract, presenting as a gastrointestinal disease or respiratory disease. Cryptosporidium is typically opportunistic and more likely to infect young and/or immunocompromised birds. Infection of the bursa (bursal cryptosporidiosis) is commonly seen in chickens with Infectious Bursal Disease virus or Chicken Infectious Anemia virus.

There are many species of Cryptosporidium that infect a wide range of animal species, including humans. The following Cryptosporidium species have been reported to infect chickens:
  • Cryptosporidium baileyi: Infects the Bursa of Fabricius, conjunctiva, kidneys, respiratory tract, cloaca, or rectum. Found worldwide and in a wide range of bird species.
  • Cryptosporidium meleagridis: Infects the small and large intestines. Found in Columbiformes, Galliformes, Passeriformes, and Psittaciformes worldwide.
  • Cryptosporidium galli: Infects the proventriculus. Affects chickens in Asia, Europe, Oceania, and South America. Found in Bucerotiformes, Galliformes, Passeriformes, Psittaciformes, and Phoenicopteriformes.
  • Cryptosporidium andersoni: Affects chickens and other Galliformes in Europe.
  • Cryptosporidium parvum: Infects the small intestine or caecum. Found in Accipitriformes, Anseriformes, Charadriiformes, Galliformes, Passeriformes, and Psittaciformes in Asia, Europe, and the Americas.

How Chickens get Cryptosporidiosis

Chickens become infected by ingesting Cryptosporidium oocysts excreted in the feces and surrounding environment from an infected host. The host doesn't need to be a chicken. Many other bird species can be infected hosts. Oocysts are capable of surviving outside their host for long periods of time (often greater than 6 months duration) in cool, moist environments, especially water sources.

How Cryptosporidiosis is Diagnosed

Cryptosporidium is detected in the conjunctiva, sinus, trachea, lungs, kidneys, small and large intestine, cloaca, and bursa of Fabricius in chickens.

Cryptosporidiosis Treatment

Cryptosporidiosis can be difficult to treat. The most important aspect of treatment is strengthening the bird's immune system, since infection with this organism tends to occur most frequently in birds with compromised immune systems. Identification and treatment of any underlying diseases and improving basic care are also paramount.

Clinical Signs

Nasal and eye discharge
Swollen sinuses
Difficulty breathing
Undigested food in droppings
Weight loss
Ruffled feathers


  • History
  • Clinical Signs
  • Physical exam
  • Cytology - fecal smears
  • Fecal flotation
  • Acid fast stains

Reported Cases

  • Case 1: Visceral gout and Cryptosporidiosis in a Commercial laying hens Formalin-fixed kidney tissues from adult egg-laying chickens in two houses of an egg-production complex in the upper Midwest were submitted to Iowa State University for histopathologic examination. An increased incidence of visceral gout, average daily mortality 1%-2% higher than expected, and egg production within normal limits were observed in both houses. Numerous developing stages of Cryptosporidium were observed on the apical surface of epithelial cells lining renal collecting tubules and ureters. Scanning and transmission electron microscopy were used to visualize colonization of cryptosporidia, disruption of microvilli, and exfoliation of parasitized epithelial cells. Lymphoplasmacytic infiltration in the wall of ureters and hyperplasia of parasitized epithelial cells resulted in partial obstruction of ureters, which may have induced visceral gout in affected hens. Ref

  • Case 2: Intestinal cryptosporidiosis in a Chickens In a retrospective examination of histopathology reports from Aug. 1, 1985, through Sept. 31, 1987, 10 cases of small- or large-intestinal cryptosporidiosis (not epithelial cryptosporidiosis of the bursa of Fabricius) were found in chickens. Infection was evenly distributed among young chickens. Incidence of intestinal cryptosporidiosis increased during 1987. Although all infected birds were clinically ill, signs or gross lesions of intestinal disease were not always present. In all cases, mild to marked histologic lesions were associated with Cryptosporidium sp.; however, intestinal tracts were not cultured for other infectious agents. The numbers of Cryptosporidium sp. and character of inflammatory response were not significantly correlated. A difference (P = 0.01) among intestinal segment (small vs. large) infection with Cryptosporidium sp was seen. Light-microscopic appearance and organ distribution of Cryptosporidium sp suggest that in addition to C. baileyi, other Cryptosporidium sp infect chickens. Until the diagnostic procedure for outbreaks of gastrointestinal disease in poultry routinely includes histopathology, fecal flotation, and virus, bacteria, and chlamydia cultures, and until species of Cryptosporidium are isolated, identified, reported, and investigated experimentally, the importance of intestinal cryptosporidiosis in chickens will remain unknown. Ref

  • Case 3: Intestinal cryptosporidiosis in a Turkey poults Naturally occurring cryptosporidiosis is reported in turkey poults suffering from diarrhoea and unthriftness in Iran. Histological and ultrastructural studies revealed high number of Cryptosporidium developmental stages mainly located in the mid and terminal portions of small intestine of the poults. Other portions of the intestinal tract were less frequently infected. Oocyst shedding was detected only in 29% of the histologically positive birds. Based on host species, clinical signs, pathology and tissue location of the parasites, Cryptosporidium meleagridis was most likely responsible for these infections. 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.
Identifying and treating any underlying infections.
Paromomycin100 mg/kg diluted in dextrose and administered by crop gavage every 12 hours for 5-7 daysK Marx; S Gelis 2000



  • Minimize stress
  • Providing quality feed
  • 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.
  • Prevent exposure to wild birds and their feces.

Scientific References


Risk Factors

  • Birds with an underlying illness
  • Young chickens
  • Immunocompromised chickens
  • Keeping birds in a dirty, unsanitary environment.
  • Ingestion of untreated or fecal contaminated drinking water.
  • Wild or pet exotic birds on the premises.
  • Letting chickens drink from rivers.