Ionophore toxicosis is characterized by muscle damage, with incoordination, leg weakness, diarrhea, dyspnea, and decreased feed intake and weight. Stunting can also occur.
Type I (“red muscle” or oxidative) fibers are the most susceptible, and lesions are most prominent in leg muscles.
In cases of ionophore toxicosis, lesions can also occur in heart and gizzard muscle. Adult birds (chickens, turkeys, ratites) and birds with no previous exposure are the most susceptible.
Gross and histological changes in ionophore toxicosis are similar to those of nutritional myopathy (see ionophore toxicosis image). Ionophores promote the movement of cations across the cell membrane, resulting in an increased intracytoplasmic concentration of Ca2+ and in cell death.
Courtesy of Dr. A. J. Van Wettere.
Monensin, lasalocid, salinomycin, and narasin have been associated with ionophore toxicosis in poultry. Salinomycin and narasin at the dose recommended for chickens (60–70 g/tonne [54.5–63.6 g/ton]) is toxic for turkeys; doses > 15 g/tonne [13.6 g/ton] are toxic in turkeys. For monensin and lasalocid, the dose recommended for chickens (110 g/tonne [100 g/ton]) is not toxic to turkeys.
The toxic dose of ionophores is decreased if they are administered in conjunction with tiamulin, erythromycin, or chloramphenicol.
Coffee senna (Senna occidentalis) is a shrub that grows in tropical and subtropical regions (see the table Poisonous Range Plants in Temperate North America). Seeds are toxic, and ingestion by poultry (both chickens and turkeys) causes myodegeneration. Clinical signs and gross and histological changes in muscles are similar to those associated with ionophore toxicosis.
For More Information
Fulton RM. Toxins and poisons. In: Swayne DE, ed. Boulianne M, Logue CM, McDougald LR, Nair V, Suarez DL, associate eds. Diseases of Poultry. 14th ed. Wiley Blackwell; 2020:1349-1382.
