Ascites Syndrome (also called water belly) can be identified outwardly by the following symptoms, However outward symptoms are not always obvious in live birds but dead birds show signs more revealing of Ascites :
Symptoms-Live Birds:
Red abdominal skin
Slowing or stopped growth rate
Waddling when walking
Swollen abdomen
Symptoms-Dead Birds
Birds die on their backs with dark purple colored heads.
Symptoms-Live Birds:
Red abdominal skin
Slowing or stopped growth rate
Waddling when walking
Swollen abdomen
Symptoms-Dead Birds
Birds die on their backs with dark purple colored heads.
What is Ascites Syndrome?
Ascites Syndrome is a condition where fluid builds up in the hepatic (areas relating to the liver), peritoneal areas (smooth transparent serous membrane that lines the cavity of the abdomen) or in the pericardial body cavities (a double walled sac which contains the heart and roots of the great vessels). According to Poultry Health Services, Ascites syndrome cannot be transmitted or spread from bird to bird.
Causes of Ascites Syndrome

Sodium
Lung damage
Liver damage
Increased vascular hydraulic pressure
Vascular damage
Increased tissue oncotic pressure
Decreased vascular oncotic (usually colloidal) pressure
Venous hypertension resulting from right heart failure in response to increased pulmonary resistance.
Most Common Cause of Ascites
WARNING-Graphic images of autopsied chickens at the bottom of the page.
Lung damage
Liver damage
Increased vascular hydraulic pressure
Vascular damage
Increased tissue oncotic pressure
Decreased vascular oncotic (usually colloidal) pressure
Venous hypertension resulting from right heart failure in response to increased pulmonary resistance.
Most Common Cause of Ascites
- Genetic predisposition to pulmonary hypertension which will progress to congestive heart failure and terminal ascites in many cases.
- An increase in vascular hydraulic pressure in the venous system (superficial veins, deep veins, or venous sinuse) caused by right ventricular failure (RVF) associated with hepatic fibrosis a condition where connective tissues is over produced and builds up in the liver..
- Cold stress-Chickens 3 weeks of age and younger exposed to cold stress are more likely to develop Ascites.
- RBC rigidity of sodium toxicity
- Less frequently from lung pathology
- Crotalaria Plant
- Liver damage caused from aflatoxin or toxins from exposure to Crotalaria plants which can cause Ascites in meat type broiler chickens, ducks and breeders.
WARNING-Graphic images of autopsied chickens at the bottom of the page.
Factors that Increase the Demand for Oxygen in Bird Lungs
Bird lungs are rigid and fixed in the thoracic cavity which means there is very little room to allow for the increased blood flow that occurs when the capillaries expand. Meat birds are particularly more susceptible to Ascites as they grow because they grow faster than other chicken breeds. The increased blood flow causes pulmonary hypertension and cor pulmonale, RVF and ascites in broiler chickens due to oxygen demands caused by exposure to cold which reduces the amount of oxygen that can be carried through the blood. Acidosis and carbon monoxide increases the blood volume, narrows or blocks the capillaries which interferes with the blood flow needed in the lungs which can increase RBC rigidity, polycythemia with increased blood viscosity which often results in flock outbreaks of pulmonary hypertension syndrome (with or without ascites).
Pulmonary Hypertension Syndrome
Pulmonary hypertension syndrome is less than 2 percent in some broiler flocks and can be as high as 15 to 20 percent in roaster flocks due to right ventricular hypertrophy which causes the increased workload in blood flow which leads to RVF if the pressure persists.
Young Broilers with Increased Sodium (Aspergillosis) Can develop Pulmonary Hypertension Syndrome
Clinical findings:
- Rapid growth rates is a known predisposing factor
- Large broilers are affected more often than smaller ones
- More frequent in males than females
- Mortality rates are higher after 5 weeks of age
- Affected broilers often die on their backs
- No signs of ascites until after RVF occurs
- Peripheral vessels get congested
- Ascites increases the respiratory rate and reduces exercise tolerance
- Not all broilers which die from pulmonary hypertension syndrome have ascites
- Death can happen before any symptoms are noticed
How to Control Ascites
Reduce bird's metabolic oxygen requirement by slowing the growth rate.
- Reduce feed density and availability
- Control Temperature, humidity, and air movement to prevent loss of body heat (especially during the early neonatal period)
- Provide shelter and heat to reduce cold stress (especially during the first three weeks of life) Cold stress causes predisposing factors that make birds more susceptible to ascites.
- Do not raise meat birds in Altitudes greater than 3,000 ft (900 m)
Results From Autopsies of Chickens & Poultry Affected with Ascites Syndrome
Autopsies Results Show:
- Lesions, clear yellow fluid and clots of fibrin in the hepatoperitoneal spaces
- Enlarged heart
- Thickened right ventricle
- Yellow protein clots are often present
- Fluid in the body cavities and heart sac
- Liver can be swollen and congested, firm and irregular with edema and have clotted protein on the surface it can also be modulated and shrunken."It may be white with subcapsular edema and a thickened capsule or have large or small blebs of fluid between the capsule and the visceral peritoneum. Hydropericardium is mild to marked, and occasionally there is pericarditis with adhesions, usually from secondary infections. Right ventricular dilatation and mild to marked hypertrophy of the right ventricular wall may be noted. The right atrium and vena cava are markedly dilated in most cases. Occasionally, there is thinning of the left ventricle. The lungs are extremely congested and edematous, (Dr. Billy M. Hargis) ".
The Merck Veterinary Manual
The Merck Veterinary Manual (MVM) covers all domesticated species and diseases in veterinary medicine worldwide. Revised and redesigned, new edition of the veterinary classic has information, color images, text, and tables to enhance and illustrate topics. This edition includes a new section on public health and zoonoses, expanded coverage of fish and aquaculture, new chapters on backyard poultry, toxicologic workplace hazards, smoke inhalation, and additional coverage of numerous new and emerging topics in veterinary medicine.
References:
1. Hargis, Billy M. DVM, PhD, Professor and Director; Tysons sustainable poultry health chair, JKS poultry health research laboratory, University of Arkansas; Department of Poultry Science, University of Arkansas. Retrived on October 7, 2017 from Merck Vet Manual http://www.merckvetmanual.com/poultry/miscellaneous-conditions-of-poultry/ascites-syndrome-in-poultry).
2. Ascites water belly. Retrieved on October 8, 2017 from Poultry Health Services. http://www.poultryhealth.ca/ascites-water-belly/
1. Hargis, Billy M. DVM, PhD, Professor and Director; Tysons sustainable poultry health chair, JKS poultry health research laboratory, University of Arkansas; Department of Poultry Science, University of Arkansas. Retrived on October 7, 2017 from Merck Vet Manual http://www.merckvetmanual.com/poultry/miscellaneous-conditions-of-poultry/ascites-syndrome-in-poultry).
2. Ascites water belly. Retrieved on October 8, 2017 from Poultry Health Services. http://www.poultryhealth.ca/ascites-water-belly/