Occurrence: Worldwide.   Species affected: All. Turkeys are more susceptible than broilers.   Age affected: All. Adults are more susceptible.

Causes: Ionophores are common anticoccidial and antibacterial feed additives. Toxicity occurs when high levels are ingested through feed.

Effects: Signs include birds lying on their sides with partial paralysis and legs extended, anorexia, weakness, drop in egg production, dyspnoea and dehydration. Mortality is variable, but may exceed 70%.

Ionophores are common anticoccidial and antibacterial feed additives. They facilitate the movement of alkali metallic actions, such as Na+, across cell membranes. Ingestion of food with high levels of ionophores can cause acute toxicity in all birds (adults are most susceptible). Toxic levels cause potassium to leave and calcium to enter the cells, resulting in cell death.

Monensin and sulphur drugs may accentuate ionophore toxicity.

Signs include birds down on their sides with partial paralysis and legs extended, anorezia, weakness, drop in egg production, dyspnoea and dehydration. Mortality is variable, but may exceed 70%.

Lesions include opaque fibrin plaques on the epicardium, haemorrhage in coronary fat and decreased liver weight.

Pallor and atrophy of muscle fibres of the legs and back can also be seen.

Diagnosis is by feed analysis.

Clinical signs, gross and microscopic lesions are suggestive. Scattered areas of hyalinisation with heart and muscle necrosis and myofibril degeneration and necrosis are important lesions.

It simulates Marek’s Disease (MD), Nitrofuran Toxicity, Selenium Deficiency (myopathy), Avian Encephalomyelitis (AE), and Cassia Occidentalis (Coffee bean) toxicity.

Spot checking feed will help prevent the disease.

Fresh feed will discontinue clinical signs. About 75% of broiler diets contain ionophores.

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