The association between weather, frenzied behaviour, percutaneous invasion by Strongyloides westeri larvae and Rhodococcus equi disease in foals.

The research suggests that certain weather conditions increase the likelihood of frenzied behavior in horses, which leads to a rise in the infection rate of two horse diseases. It argues that this frenzy may facilitate these parasites’ invasion of the foals.

Study Background and Methodology

• The investigators observed episodes of “frenzy,” a type of aggressive, hyperactive behavior among horses restricted to areas covered with sand or soil. They noticed these episodes notably increased under specific weather conditions, such as following rain and within a specific range of air and soil temperatures.
• In order to examine the association between these behaviors and the incidence of infections by Strongyloides westeri larvae and Rhodococcus equi, they took fecal samples and monitored the egg counts of the former species. Subsequently, the presence of R. equi was confirmed in soil samples and in the feces of the horses.

Study Findings

• The researchers made a significant observation regarding an increase in Strongyloides westeri egg counts in the horse droppings four to five days after the episode of frenzy. This suggests that the frenzy behavior could likely result from an invasion of the horse’s body by S. westeri larvae.
• They also found Rhodococcus equi bacteria in all soil samples and in droppings of the majority of the horses.
• Interestingly, in case of foals, R. equi was found in the limbs and peripheral lymph nodes, which is contrary to most reported cases where this bacterium was localized elsewhere in the foals’ bodies.

Study Conclusions and Implications

• The researchers proposed that the frenzy behavior in horses could be a response to the percutaneous, or through-the-skin, invasion by the Strongyloides westeri larvae.
• They also asserted that such invasions could possibly facilitate the invasion by Rhodococcus equi, a common but opportunistic bacterial pathogen in horse populations, as it was found in the majority of soil and fecal samples following the frenzy episodes.
• This study helps to highlight the significant influence that weather conditions and the environment could have on horse health and behavior, with potential implications for the prevention and treatment of equine diseases.