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Sour Crop

Thrush, Yeast Infection, Moniliasis

Sour crop, also known as thrush, are common names for candidiasis---a fungal infection caused by yeasts belonging to the Candida genus. There are several different species of Candida that can cause infection in chickens, with the most common being C. albicans. Candida species are a normal part of a healthy chicken's microflora, in which they are present in small amounts. Candida coexist alongside several bacterial organisms, which are all kept in balance with one another. However, Candida are opportunistic, meaning that they take advantage of any opportunity that presents itself which enables them to flourish within the chicken's digestive system, frequently involving the oral cavity. This 'window of opportunity' occurs during periods in which the chicken is vulnerable, such as from inappropriate antibiotic use, malnutrition, stress, underlying illness, spoiled water, or from excessive use of disinfectants.
Candidiasis in chickens


Characteristic of candidiasis is the presence of white patches or plaques (oral lesions) found on the chicken's tongue, mouth, crop and esophagus tissue. Affected birds often will also experience delayed emptying of the crop ("crop binding"), which after a period of time can lead to the development of a foul smell coming from the chicken's mouth. Chickens may also develop generalized clinical signs such as loss of appetite, reduced drinking, and lethargic/depressed behavior.

Chickens with candidiasis can sometimes be concurrently infected with other diseases, which can complicate or confuse clinical signs observed. A case of concurrent infection in a backyard flock of chickens occurred in 2016 where the birds were concurrently infected with fowlpox and candidiasis.

Thrush 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
In mild or early cases of candidiasis in chickens, all that may be needed is a simply diet modification and the use of natural remedies. 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 will need their crop emptied and flushed (a procedure that should only be done by a veterinarian, as if it is done wrong it can be fatal to the bird). Concurrent supportive care may be needed as well, in the form of IV fluids. In order 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. In order to strengthen immunity, there are a variety of different herbs and nutraceuticals that might be prescribed by your vet to be administered concurrently with the primary antifungal drugs.

Clinical Signs

Oral lesions inside mouth
Excessive beak rubbing
Delayed crop emptying
Sour odor from mouth
Depression
Loss of appetite
Lethargy
Poor digestion of food
Weight loss
Listlessness
Roughened feathers
Yellowish-green diarrhea

Diagnosis

  • History
  • Clinical signs
  • Physical exam
  • Culture
  • Cytology

Treatment

NameSummary
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.
Fennel teaHas proved a good initial natural product to get the crop moving( purchase fennel tea bags)Bird Vet Melbourne
Crop FlushYour veterinarian will usually empty out and flush the chicken's crop contents and obtain a sample to run a laboratory test on in order to verify the specific organism. Following this procedure, supportive care is needed in order to prevent dehydration and help to restore the natural balance of the crop.Bird Vet Melbourne
AntifungalsNystatin (300 KIU/kg) administered orally is the drug of choice, however in some cases your veterinarian may recommend Ketoconazole (10-30 mg/kg) or Itraconazole.

This medication is only effective for oral or topical use only, for it must come into direct contact with the yeast to be effective.
K Marx; D McCluggage
Strengthen immunityAloe vera, Chinese herbal tea combinations, Larch arabanogalactans, or Lactalbumins.D McCluggage
Apple cider vinegarAdd 1 tablespoon of apple cider vinegar to each gallon of water and use as drinking water for 3 to 4 days. It may help in chickens with mild cases.D McCluggage; Bird Vet Melbourne; G Damerow

Prevention

  • 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

Blogs

Risk Factors

  • Recently received antibiotics or coccidiostats
  • Young chicks
  • Older chickens
  • Chickens with weakened immune systems, such as when recovering from an illness or injury
  • Stress
  • Excessive or inappropriate use of disinfectants
  • Malnutrition
  • Spoiled water