Molecular characterisation of Histoplasma capsulatum sensu lato from Ethiopian horses reveals two distinct phylogenetic clades.

The research focused on the characterisation of Histoplasma capsulatum, the pathogen causing a contagious horse disease in Ethiopia. Analysis of the pathogen from infected horses identified two different phylogenetic groups.

The Study’s Purpose and Methodology

• Epizootic lymphangitis (EL) is a severe and infectious disease that affects horses in many regions of Ethiopia. It is caused by a strain of Histoplasma capsulatum known as ‘var. farciminosum’.
• The objective of this study was to characterise and identify this strain more accurately.
• In the study, a total of twelve yeasts isolated from infected horses, suspected to be H. capsulatum or yeasts unidentified by conventional methods, were characterised using ITS sequencing.
• Six of these isolates were found to correspond with H. capsulatum and the other six were identified as other fungi species: Pichia kudriavzevii, Trichosporon asahii, Geotrichum silvicola, and Moesziomyces aphidis.
• The H. capsulatum isolates were further analysed using multilocus sequence analysis. In this method, four key gene loci were PCR-amplified and sequenced.

Findings of the Study

• Phylogenetic analysis of the sequenced data suggested that there were two distinct groups or clades within the H. capsulatum strain. These groups were named the Eurasia clade and the Africa clade.
• Three of the isolates and one of the reference strains (ATCC 58332) were found to be identical and belonged to the Eurasia clade. The other three isolates and the second reference strain (ATCC 28798) also matched and belonged to the Africa clade.
• These findings suggest that there are at least two distinct groups of H. capsulatum causing disease in Ethiopian horses.

Significance and Implications of the Research

• The research stressed on the importance of advanced molecular tools in accurately identifying and typing pathogens and discovering new microorganisms in veterinary microbiology.
• The identification of different phylogenetic clades could improve the understanding of the disease’s transmission and epidemiology, potentially informing better diagnostic and control strategies.