Identity

A high-priority, non-infectious metabolic disorder of fast-growing broilers. Systemic hypoxia triggers polycythemia and pulmonary hypertension, leading to right ventricular dilation, right-sided heart failure, and massive fluid accumulation in the abdomen.

Overview

Ascites (Pulmonary Hypertension Syndrome) results from a physiological mismatch between a broiler's rapid growth rate and its limited cardiopulmonary capacity. Environmental triggers (cold stress, poor ventilation, high altitude) induce systemic hypoxia, leading to increased blood viscosity and pulmonary arterial resistance. The chronic pressure overload destroys the right ventricle, causing transudation of fluid into the peritoneal cavity. Because it is metabolic, medicines do not cure it. Management relies entirely on moderating early growth rates (feed restriction, light schedules) and controlling environmental temperatures.

Structured Facts

Classification

Metabolic > Non-Infectious

Epidemiology

• Prevalence in India: Common in fast-growing broilers
• Severity: High
• Affected Species: Fast-growing broilers
• Affected Age: Late-stage broilers (mortality greatest > 5 weeks)
• Transmission: Non-infectious
• Seasonality: Associated with cold weather/cold stress
• Mortality: Approaching 100% in clinically affected birds showing abdominal distension
• Morbidity: Incidence can exceed 5% in fast-growing flocks
• Economic Importance: High (late-stage mortality, processing plant condemnation)

Clinical Signs

• Early/Intermediate: Reduced exercise tolerance, cyanotic combs and wattles, dyspnea
• Advanced: Severe abdominal distension, reluctant waddling gait; targets Cardiovascular and Respiratory systems
• Postmortem Findings: Large volume (up to 300mL) of clear, amber fluid with yellow fibrin clots in peritoneal cavity. Right ventricular dilatation and hypertrophy. Liver firm/white capsule.

Diagnosis

• Field Diagnosis: Fluid accumulation in abdomen, cyanosis
• Laboratory Tests: Calculation of Right Ventricle-to-Total Ventricle (RV/TV) ratio > 0.25
• Differential Diagnosis: Colibacillosis (peritonitis), Hepatotoxicoses

Treatment

• Immediate Actions: Increase ventilation, reduce cold stress
• Medicines: None
• Withdrawal: Not applicable

Prevention

• Vaccination: None
• Biosecurity: Not applicable
• Farm Management: Moderating growth rates via feed restriction/light-dark schedules (first 2 weeks); keeping dust/ammonia low; controlling temperatures to prevent cold stress; SpO2 monitoring in breeding.

Quantitative Data

• Morbidity Rate: > 5%
• Mortality Rate: ~100% (of clinically affected)
• Target Age: > 5 weeks
• Diagnostic RV/TV Ratio: > 0.25
• Fluid Volume: Up to 300 mL

Relationships

• Vaccines: None
• Medicines: None
• Breed Susceptibility: Fast-growing broilers
• Predisposing Relationships: Co-infection with Aspergillus fumigatus or IBV damages lung parenchyma, triggering Ascites