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Other Names: Thrush, Sour Crop, Yeast Infection, Moniliasis, Candidiasis, Candida Infection

Candidiasis, often referred to as "sour crop", is an infection of the chicken's crop, caused by a build up of Candida. The most common pathogens belonging to this group are Candida albicans, C.tropicalis, C.glabrate, and C.krusei. Candida species are a normal part of a healthy chicken's microflora. Factors such as prolonged or inappropriate antibiotic use, corticosteroids, malnutrition, stress, underlying illness, and/or excessive use of disinfectants can predispose chickens to candidiasis.

Clinical Signs of Candidiasis

The most common clinical signs observed in chickens with candidiasis include:
  • Changes in behavior
  • Delayed crop emptying, which after a period of time can lead to the development of a foul smell coming from the chicken's mouth.
  • Regurgitation
  • Reduced appetite
  • Depression/lethargy
  • White patches or plaques (oral lesions) on the inside of their mouth and/or under the tongue.
  • Abnormal droppings, often appear brownish and watery
  • If chicks are affected, may show stunted growth
Chickens with candidiasis can sometimes be concurrently infected with other diseases, which can complicate or confuse clinical signs observed.

Candidiasis Vs Canker

Candidiasis (Thrush)Canker
Body areas affectedOral cavity, esophagus, and cropOral cavity, esophagus, and crop
Pathogen typeYeastProtozoan parasite
Pathogen speciesCandida albicansTrichomonas gallinae
Oral lesion appearancePatches of raised, whitish, dead epithelial debris. The top white pseudomembranes can be wiped off. Sticky, yellowish-white 'canker-like' masses of caseous, necrotic material.
More likely to occur followingProlonged antibiotic therapy, concurrent disease, infestation with internal or external parasites, or stressful event.Pigeons and doves sharing the same water or feed source.
TreatmentTreat the primary cause, antifungals, strengthen immunity, crop flushMetronidazole, thyme extract

Treatment for Candidiasis

In very mild or early cases of candidiasis, all that may be needed is a change in diet and the use of natural remedies, such as apple cider vinegar added to the water. However, once the condition has progressed to a severe infection (once the bird has stopped eating and drinking and is showing obvious lethargy or depression), a trip to your veterinarian is needed.

In severe cases, if the chicken is unable to empty their crop, they may need it emptied and flushed (a procedure that should only be done by a veterinarian, as if it is done wrong, can be fatal to the bird). Concurrent supportive care may be needed as well, in the form of IV fluids, to help restore the natural balance of microorganisms in the crop. Your veterinarian will usually prescribe one of three types of antifungal medications---Nystatin, Ketaconazole, or Itraconazole. There are a variety of different herbs and nutraceuticals that can be given concurrently to help strengthen their immune system.

Clinical Signs

Delayed crop emptying
Oral lesions inside mouth
Excessive beak rubbing
Sour odor from mouth
Loss of appetite
Weight loss
Yellowish-green diarrhea


  • History
  • Clinical signs
  • Physical exam
  • Wet or Gram's-stained smears
  • Crop washings

Reported Cases

  • Case 1: Pulmonary candidiasis in a Sun conure An adult male sun conure was evaluated because of lethargy, ruffled feathers, and decreased appetite. Physical examination revealed hypothermia, dehydration, dyspnea, and crop distention. Results of a complete blood cell count revealed a marked inflammatory leukogram, and cytologic examination of a crop swab sample identified gram-negative bacilli and occasional yeast organisms. Radiographs demonstrated an opaque, ill-defined, soft tissue structure in the caudal coelom just cranial to the renogonadal silhouette, loss of serosal detail, and splenomegaly. Endoscopic examination revealed a pale, granuloma-like structure within the caudal aspect of the left lung, splenomegaly, and an enlarged proventriculus. Intraoperative cytologic examination of a biopsy sample of the lesion demonstrated yeast organisms, and a subsequent culture of the biopsy sample revealed Candida albicans. The bird was treated intraoperatively with intralesional amphotericin B. Postoperative treatment consisted of meloxicam, trimethoprim sulfa, amphotericin B by nebulization, and systemic itraconazole and fluconazole. The bird made a complete recovery, was discontinued from all medications, and has remained asymptomatic for 6 months. Although rare, pulmonary candidiasis should be on the list of differential diagnoses for any respiratory infection in birds. Endoscopic biopsy, cytology, and fungal culture were valuable in making the diagnosis. 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.
NystatinMay be effective in mild infections. Given twice a day orally at 300,000 IU/kg.B Speer
Apple cider vinegarMay be effective in mild infections. Add 1 tablespoon of apple cider vinegar to each gallon of water and use as drinking water for 3 to 4 days.D McCluggage; Bird Vet Melbourne; G Damerow
KetoconazoleMay be indicated for severe infections. Given orally at 10-30 mg/kg, twice a day for 7-30 daysK Marx; D McCluggage
FluconazoleMay be indicated for severe infections. Given orally at 20 mg/kg, every 48 hours for 14 to 17 days.K Marx
FlucytosineMay be indicated for severe infections. Given twice a day orally at 250 mg/kg for 14 to 17 days.K Marx
ItraconazoleMay be indicated for severe infections. Given twice a day orally at 10 mg/kg for 21 days.K Marx
Pomegranate (Punica granatum) peel powderHas high inhibition against Candida albicansM Pai et al., 2010
Clove (Syzygium aromaticum powder and Thyme (Thymus vulgaris) oilAdding clove powder (2%) and thyme (200 ml/kg) of the diet of broiler chickens help improve the symptoms induced by Candida albicans and increased PCV %, ALT and AST level, with a decrease in erythrocyte count and total leukocyte count.G Fatah et al., 2020; A Abed et al., 2021
Cinnamon (Cinnamomum cassia) essential oilHas strong antimicrobial effect against Candida sppJ Ahmed et al., 2019; S Yanakiev 2020; M Prajapati et al., 2021;



  • Avoid prolonged or excessive use of antibiotics in chickens.
  • Maintain good sanitary conditions
  • Do not put sick or injured chickens back out into the flock until they have fully recovered and immune system is restored.
  • Feed a balanced diet
  • Do not feed chickens spoiled food
  • Change water sources daily
  • Do not excessively use disinfectants
  • Administer apple cider vinegar every other month in drinking water at a rate of 5 mL per L of water.

Scientific References

Good Overviews

Risk Factors

  • Prolonged or inappropriate use of antibiotics and corticosterioids
  • Chickens with scissors beak
  • Chickens with weakened immune systems, such as when recovering from an illness or injury
  • Excessive or inappropriate use of disinfectants
  • Malnutrition

Case Stories