What is the primary cause of Tetanus infection in horses?

The primary cause of Tetanus infection in horses is indeed bacterial toxins found in soil or feces. The bacterium responsible for Tetanus, Clostridium tetani, is commonly located in the environment, especially in areas contaminated with feces, soil, and decaying organic matter. When a horse suffers a wound or injury, particularly one that is deep or puncture-like, it can allow these bacteria to enter the body. Inside the anaerobic (low-oxygen) environment of a wound, the bacteria can proliferate and produce a potent toxin that affects the nervous system, leading to the clinical signs associated with Tetanus, such as muscle stiffness and spasms.

While other factors, such as exposure to moldy hay or improper feeding practices, can affect a horse's health, they do not specifically relate to the Tetanus infection mechanism. Animals do not typically transmit Tetanus directly to each other, making the presence of the bacteria in the environment the primary concern for equine Tetanus.