Crop Infections in Birds

Crop infections in pet birds are not as common as they were years ago, but they still occur, primarily in baby birds that are being syringe- or spoon-fed a formula-based diet. Crop infections not usually fatal if treated early, but they can be serious and may cause problems with a bird’s appetite and/or digestion.

What is the crop?

 The crop (also known as the ingluvies) is a muscular pouch located on the front of a bird's neck, above the top of the chest or sternum. It is an enlargement of the esophagus and serves as a storage place for food. While present in most pet birds, not all birds have a crop. 

Adult birds produce crop milk from the crop, which is composed primarily of a secretion of the cells lining the crop, along with some beneficial bacteria and IgA, an antibody important to the immune system. The parents regurgitate crop milk and feed it to newly hatched birds. 

What are some of the causes of crop infections?

The crop can become infected by many of the same things that infect other areas of the gastrointestinal tract. “Sour crop” is a term used for any infection in the crop. Infections often cause the digestive waves of the crop to slow down dramatically or completely stop, causing the food in the crop to become sour. 

"Crop infections can be caused by bacteria or yeast, especially Candida species."

Crop infections can be caused by bacteria or yeast, especially Candida species. Trichomonas, a protozoal organism, causes crop infections in pigeons and raptors (birds of prey) that requires microscopic analysis of crop contents to diagnose. In those species, this infection is often treated based on clinical suspicion. Viral diseases, such as avian bornavirus and polyomavirus can also cause slow crop motility and sour crop in psittacines (parrots). 

Other crop problems include crop burns (from over-heating formula for baby birds), crop lacerations (from incorrectly feeding baby birds or from other trauma), and the entrapment of foreign objects. 

What are some of the signs of crop infection? 

The most common symptoms of crop infection are a fluid-filled, distended crop and/or regurgitation. You may notice a sour smell if you smell the bird’s mouth or regurgitated material. The regurgitated material may be food, crop fluid, or both. While other conditions can cause regurgitation in birds, crop infection occurs often enough that it should be considered before other, more serious conditions. Crops that are distended with fluid and showing no signs of motility need immediate veterinary attention. 

How are crop infections diagnosed? 

Usually, a procedure called a crop wash or crop aspirate is performed. The veterinarian places a small amount of water into the crop using a feeding tube. Some of the fluid is then suctioned out and tested for infectious organisms. The tests may include direct microscopic examination to look for abnormal bacteria or yeast. Your veterinarian can perform Gram stains on the fluid and examine it with a microscope to better identify abnormal bacteria and yeast organisms. A bacterial culture of the crop fluid may be sent away to identify the specific type of bacteria present. Swabs may be sent to a reference lab for viral testing, as well. 

If these tests do not provide an answer, other tests may be needed, such as radiographs (X-rays) or crop biopsy. Tests that give basic information about the overall health of the bird may also be recommended, such as white and red blood cell counts or blood chemistry profiles. 

How are crop infections treated? 

Once the correct diagnosis is made, your veterinarian will determine the best course of treatment.

• Bacterial infections are treated with antibiotics.
• Yeast infections are treated with an anti-fungal medication.
• Viral infections such as polyomavirus and avian bornavirus require supportive care, as there is no anti-viral treatment available.
• Impactions of the crop, crop burns, lacerations, and entrapment of foreign objects in the crop may require a combination of medical and surgical therapy.

Crop infections can be very serious and may require your bird be hospitalized and treated. Veterinary attention is required to resolve any crop diseases or problems.