High frequency and high genetic diversity of Pneumocystis sp. in foals
What does Pneumocystis diversity look like in one of its animal hosts? An investigation of foals reveals an unexpectedly high frequency of Pneumocystis together with remarkable genetic diversity, providing new clues about strain circulation, coinfection, and host–fungus relationships.
Horses harbour their own Pneumocystis populations, but their prevalence and genetic diversity remain poorly characterized. To address this gap, Guiblin and colleagues investigated Pneumocystis in lung samples from 22 foals aged 1–7 months, including animals with interstitial pneumonia and animals that died from unrelated conditions.
The fungus was detected in 21 of the 22 foals and in 48 of the 52 lung specimens analysed, revealing a strikingly high frequency of Pneumocystis in this population.
Genetic analyses uncovered substantial diversity. Single nucleotide polymorphisms (SNPs) were identified in samples from 16 foals, leading to the identification of three alleles. Mixtures of alleles were also frequently observed, suggesting that individual animals may simultaneously harbour more than one Pneumocystis strain.
Ultradeep sequencing and phylogenetic analyses further identified sequences distinct from the reference Pneumocystis sp. ‘Equus ferus caballus’, raising the possibility that an additional, yet uncharacterized Pneumocystis species may infect foals.
These findings expand current knowledge of Pneumocystis diversity in animal hosts and open new questions about strain circulation, host specificity, and the evolutionary diversity of the genus.
Article reference
Guiblin J, Le Gal S, Le Nan N, Paranthoën C, Velo-Suárez L, Foucher N, Bernez-Romand M, Madeline A, Cordonnier-Lefort N, Sevin C, Valle-Casuso JC, Guillot J, Moreau P, Nevez G.
High frequency and high genetic diversity of Pneumocystis sp. in foals.
Medical Mycology. 2026;64(6).
