The Clonal Population of Trichophyton equinum from Dermatophytoses of Japanese Racehorses.

This study analyzed the genetic and physiological characteristics of the fungus Trichophyton equinum, which often causes skin infections in horses, obtained from Japanese racehorses. The results suggest that these Japanese T. equinum isolates seem to come from a single genetic source, or clonal population.

Overview of the Research and Methodology

• The research utilized molecular and physiological testing on isolates of Trichophyton equinum, a fungal organism that commonly causes skin infections in horses and occasionally in humans. These isolates were obtained specifically from Japanese racehorses suffering from dermatophytoses, a type of fungal infection.
• The nucleotide sequence analysis compared the internal transcribed spacer (ITS) region of the isolates’ DNA to a reference strain’s DNA. This analysis found that the Japanese isolates showed a high degree of genetic similarity, identified to be 99.5%, to the reference strains. The ITS sequences within the Japanese isolates themselves also demonstrated a perfect 100% identical match.
• Similarly, the beta-tubulin (BT2) gene sequences in the isolates were found to be identical to those in the reference strains of T. equinum.

Findings

• One of the major findings of the study was that the MAT1-2 allele, a specific marker gene, was found in all seven isolates tested. Conversely, none of the tested isolates carried the MAT1-1 allele.
• Another important finding pertained to the isolates’ growth behavior. They were able to grow solely on Trichophyton Agar 5, but did not thrive on Trichophyton Agar 1 and 4, indicating a specific requirement for nicotinic acid for their growth.

Conclusions

• The uniformity in genetic sequencing, the sole presence of the MAT1-2 allele, and the distinct growth pattern under specific nutritional conditions point to the conclusion that the T. equinum isolates derived from Japanese racehorses are likely from a clonal population, meaning they have originated from a single ancestor through asexual reproduction.
• This understanding can help in formulating specific and effective treatments and preventive measures for dermatophytoses in racehorses, a concern for those involved in equine care and the racing industry.