Introduction

Associated with inadequate supplies of oxygen, poor ventilation and physiology (oxygen demand, may be related to type of stock and strain). Ascites is a disease of broiler chickens occurring worldwide but especially at high altitude. The disease has a complex aetiology and is predisposed by reduced ventilation, high altitude, and respiratory disease. Morbidity is usually 1-5%, mortality 1-2% but can be 30% at high altitude. Pulmonary arterial vasoconstriction appears to be the main mechanism of the condition.

Signs

• Sudden deaths in rapidly developing birds.
• Poor development.
• Progressive weakness and abdominal distension.
• Recumbency.
• Dyspnoea.
• Possibly cyanosis.

Post-mortem lesions

• Thickening of right-side myocardium.
• Dilation of the ventricle.
• Thickening of atrioventricular valve.
• General venous congestion.
• Severe muscle congestion.
• Lungs and intestines congested.
• Liver enlargement.
• Spleen small.
• Ascites.
• Pericardial effusion.
• Microscopic - cartilage nodules increased in lung.

Diagnosis

Gross pathology is characteristic. A cardiac specific protein (Troponin T) may be measured in the blood. This may offer the ability to identify genetic predisposition. Differentiate from broiler Sudden Death Syndrome and bacterial endocarditis.

Treatment

Improve ventilation, Vitamin C (500 ppm) has been reported to be of benefit in South America.

Prevention

Good ventilation (including in incubation and chick transport), avoid any genetic tendency, control respiratory disease.