Brittle tail syndrome is an emerging infection in horses caused by a keratinolytic fungus Equicapillimyces hongkongensis gen. nov., sp. nov.

This research explores a new fungal infection in horses known as brittle tail syndrome, identified as being caused by the novel fungus Equicapillimyces hongkongensis gen. nov., sp. nov.

Introduction and Background on Brittle Tail Syndrome

• Brittle tail syndrome is a recent disease affecting horses, which leads to the weakening and breakage of tail hair. It has been traced back to a previously unknown fungus referred to as Equicapillimyces hongkongensis gen. nov., sp. nov.

E. hongkongensis Characteristics and Growth Conditions

• The fungus is a type of hyaline mould which branches into divisions and grows optimally at temperatures around 30°C. It demands nicotinic acid to survive but is inhibited by cycloheximide, a compound known for its antifungal properties.
• The uniquely designed fungus targets horse hair, filling the core of the infected hair shafts with hyphae, further creating structures resembling ascomata that have banana-shaped ascospore-like structures which disrupt the hair cortex from within.

Correlation Between Brittle Tail Syndrome and E. hongkongensis

• The research clearly establishes a strong link between the syndrome and the novel fungus. Out of 22 horses showing symptoms of the syndrome, all were found to have the fungus present in smear tests (compared to just 6.5% of 31 asymptomatic horses), while 72.7% had positive culture tests (compared to 6.5%) and all were PCR positive (compared to 32.3%).

Pure E. hongkongensis Isolates

• Genotyping was carried out on pure E. hongkongensis isolates and their corresponding samples using PCR and sequencing of several genes. The results showed that while all the isolates were identical, they were also distinctly different from other known fungi, being mostly related to fungi in the class Sordariomycetes and the family Ophiostomataceae.

Unknown Factors and Potential Risks

• While this study provides significant insight into the cause of brittle tail syndrome and its linkage with the newly discovered fungus, several aspects remain unknown. This includes information about its geographical distribution, environmental or animal reservoirs where it may exist.
• Although the most noticeable current effect is the unsightly appearance of the infected horse tails, the fungus could form the basis of more serious equine pathogens if it happens to affect the skin and hooves of horses.