Clostridium botulinum type-C intoxication associated with consumption of processed alfalfa hay cubes in horses.

This research article documents an outbreak of botulism in horses linked to the consumption of processed alfalfa hay cubes, resulting in various clinical signs, and death in several instances. A causal relationship was established based on the presence of clostridium botulinum type-C toxin in the feed and the horses’ biological samples. Treatment with type-C antitoxin and plasma from horses previously immunized with clostridium botulinum type-C toxoids proved partially successful.

Background and Objective

• The study aimed to investigate an observed episode of nervous system dysfunction in horses across 17 premises in southern California. The researchers were interested in identifying the underlying cause of the dysfunction and establishing appropriate countermeasures.

Observations and Findings

• Thirty-eight horses were affected by nervous system dysfunction, and out of these, 31 died. The dysfunction was characterized by symptoms like a drastic increase in appetite, anxious demeanour, muscle tremors, decreased eyelid tone, dilated pupils, unusually small, hard faecal balls, and a tendency to lie down sternally with neck extension.
• Analysis of the temporal distribution of cases across all premises led the researchers to hypothesize that the disease’s cause could be related to a common batch of alfalfa hay cubes consumed by all the affected horses.

Diagnosis and Research Methodology

• To confirm this hypothesis, 15 horses were submitted for postmortem examination.
• The diagnosis of botulism was confirmed upon the detection of type-C1 toxin in both the feed in question and the intestinal contents of one of the horses. The horse’s liver also tested positive for the toxin.
• Toxigenic strains of Clostridium botulinum type-C, the bacterium responsible for causing botulism, were isolated from the intestinal contents of 5 affected horses. One horse contained type-C1 and type-C2 toxins in addition.

Treatment and Survival Rate

• The researchers treated 10 horses with a type-C antitoxin and plasma obtained from horses previously immunized with clostridium botulinum type-C toxoids to counter the toxin’s effects.
• Out of these treated horses, seven survived, indicating that the treatment had a success rate of 70%.
• These findings highlight the importance of maintaining a cautious approach when sourcing and processing equine feed, to prevent outbreaks of life-threatening diseases like botulism.