Phycomycosis of the horse caused by Basidiobolus haptosporus.

This research article focuses on a unique case of phycomycosis (a type of fungal infection) in a horse due to Basidiobolus haptosporus. The report contrasts this case with typical clinical indicators of diseases caused by Hyphomyces destruens, and conducts a retrospective analysis of 63 previous cases of phycomycosis diagnosed since 1970, identifying 11 with similar characteristics.

Unique Case of Phycomycosis

• The researchers describe the unique case of a horse suffering from subcutaneous phycomycosis, a type of fungal infection, caused by Basidiobolus haptosporus. This fungal disease is not typically found in horses and presented some clinical symptoms similar to those caused by Hyphomyces destruens, another type of fungus. However, its gross and microscopic pathological traits were distinctly different, making this an unusual and noteworthy case warranting further study.

Pathological Findings

• Specifically, the histopathological characteristics of this Basidiobolus haptosporus infection were identified by a unique eosinophilic sleeve surrounding wide, frequently septate hyphae (the filamentous structures of a fungus) scattered throughout the affected tissue. This distinctive fungal growth pattern was commonly found at the advancing border of the lesion, highlighting the progressive nature of the infection.

Retrospective Study of Phycomycosis Cases

• In a broader scope, the researchers also revisited 63 cases of phycomycosis that had been diagnosed at their laboratory since 1970. They found that there were 11 other cases displaying similar histological features to the unique case under study, showing that while rare, this type of Basidiobolus haptosporus infection was not unprecedented.

Implications for Disease Understanding and Epidemiology

• The discovery of this particular form of fungal disease in horses and its recurrence in the studied cases broadens the understanding of the diversity and behavior of the Basidiobolus genus in the equine host. The research hints at potential implications for the epidemiology (the study of diseases and their frequency, distribution, and control) and pathogenesis (the manner of development) of equine dermal granulomas (skin nodules) caused by fungal infections. The outcome of this case and the retrospective study indicates a need for further research to deepen our knowledge of causative factors, transmission, and disease progression in these fungal infections in horses.