Accidental monensin toxicosis in horses in Mozambique.

This research article reports on an unintentional exposure of horses to monensin, a toxic substance, in Mozambique, leading to serious health complications and several deaths.

Introduction and Background

This research study was conducted after an incident in Mozambique where horses from multiple farms were accidentally fed a concentrate that contained 69 parts per million (ppm) of monensin. Monensin is an ionophore antibiotic commonly used in poultry and cattle feeds to promote growth and prevent coccidiosis, a parasitic disease. However, it is highly toxic to horses, with serious health consequences, as observed in this study.

Observations and Findings

The research reported the clinical signs observed in the affected horses:

• The horses exhibited acute signs of toxicity, suggesting an immediate and severe reaction to the monensin exposure.
• Depression was observed, indicating a general state of ill health and potential neurological effects due to the toxicosis.
• The horses were anoretic i.e., they lost appetite and willingness to eat, which is a common reaction in animals suffering from acute illness.
• Paresis was another symptom seen. This partial loss of voluntary movement or paralysis indicates significant nervous system impairment.
• Epistaxis, or nose bleeding, was reported in one case which could be linked to internal hemorrhage caused by monensin toxicosis.

Postmortem Findings

Postmortem examination was performed on three horses. Observations included:

• Presence of petechial hemorrhages (tiny purple or red spots) in various internal organs, such as muscles, heart, lungs, gastrointestinal tract, and spleen. These might be indicative of blood clotting disorders or damage to the blood vessels caused by the toxicity.
• The absence of significant histopathological lesions in cardiac and skeletal muscles, except for one case where there was focal loss of myofibrils (the basic rod-like units of a muscle). This could suggest that monensin’s harmful effects might not always manifest in visible tissue damage.

This study emphasizes the critical need for careful handling and administration of feed in livestock farming to prevent disastrous incidents of toxicosis, particularly from substances like monensin that are beneficial to some animals but fatal to others.