Characterization of the Healthy Ocular Mycobiome of Purebred Lusitano Horses Using Oxford Nanopore Long-Read Sequencing.

Overview

• This study analyzed the fungal communities (mycobiome) on the eyes of healthy Purebred Lusitano horses using advanced long-read DNA sequencing and fungal culture methods.
• It aimed to provide a detailed characterization of the normal fungal flora present on the equine ocular surface and to understand how environmental factors may influence this community.

Background

• The ocular surface is a distinct microbial environment continuously exposed to microbes from the surrounding environment.
• While bacterial components of the ocular microbiome have been studied, the fungal part, especially in horses, remains less understood.
• Understanding the healthy ocular mycobiome is important as some fungi are associated with eye infections, such as fungal keratitis.

Objectives

• To characterize the fungal community present on the healthy ocular surface of Purebred Lusitano horses.
• To investigate how factors such as geographic location and housing conditions affect the composition of the ocular mycobiome.
• To establish a baseline fungal profile for future research into diseases and environmental impacts on equine eye health.

Methods

• Sample Collection: Ocular surface samples were obtained from 12 clinically healthy Purebred Lusitano horses located in three different geographical regions of Portugal.
• Housing Systems: Horses were kept under two different housing conditions to evaluate environmental influence.
• Sequencing Technology: The Oxford Nanopore long-read sequencing platform was used, allowing for comprehensive identification of fungal species by sequencing longer DNA fragments.
• Conventional Cultures: In parallel, traditional fungal culture methods were employed to validate sequencing findings and identify viable fungi.

Key Findings

• High Diversity: The fungal communities on the ocular surface were highly diverse and showed significant variability between individual horses.
• Dominant Fungal Genera: Multiple fungal genera were abundant across samples, including several environmental fungi, although specific genus names were not provided in the abstract.
• Environmental Influence: Variation in fungal community composition suggested that local environmental conditions, such as geographic location and housing system, influence the ocular mycobiome.
• Presence of Pathogenic Fungi: Fungal genera commonly linked to equine fungal keratitis were found in the eyes of healthy horses, indicating these fungi can be part of the normal ocular flora without causing disease.
• Baseline Establishment: This work provides a foundational profile of the healthy equine ocular mycobiome useful for comparison in studies of ocular infection or microbial imbalance (dysbiosis).

Significance and Future Directions

• Understanding the normal ocular mycobiome improves knowledge of eye health and disease susceptibility in horses.
• The impact of environment and housing on fungal communities supports the importance of considering external factors in managing eye health.
• Detecting potential pathogenic fungi in healthy eyes highlights the need to understand microbial interactions and triggers that lead to disease.
• The use of Oxford Nanopore long-read sequencing demonstrates an effective approach for comprehensive fungal community profiling in veterinary studies.
• Future research can build on this baseline to explore fungal dysbiosis during ocular diseases, investigate the roles of specific fungi, and develop preventive or therapeutic strategies.