(382) Changes in vaginal vestibule microbiota during estrus cycles in Asian elephants

Y. Yang¹, N. Kittisirikul², W. Langkaphin², T. Angkawanish², P. Comizzoli³, K. Chatdarong¹

1. Department of Obstetrics, Gynaecology and Reproduction, Faculty of Veterinary Science, Chulalongkorn University, Bangkok, Thailand

2. The Thai Elephant Conservation Center, National Elephant Institute of Thailand, The Forest Industry Organization, Lampang, Thailand

3. Smithsonian’s National Zoo and Conservation Biology Institute, Washington DC, USA


Abstract Text:

Changes in vaginal vestibule microbiota during estrus cycles in Asian elephants (Elephas maximus)

Y. Yang¹, N. Kittisirikul², W. Langkaphin², T. Angkawanish², P. Comizzoli³, K. Chatdarong¹

1. Department of Obstetrics, Gynaecology and Reproduction, Faculty of Veterinary Science, Chulalongkorn University, Bangkok, Thailand

2. The Thai Elephant Conservation Center, National Elephant Institute of Thailand, The Forest Industry Organization, Lampang, Thailand

3. Smithsonian’s National Zoo and Conservation Biology Institute, Washington DC, USA.

The Asian elephant (Elephas maximus), classified as endangered by the IUCN, has the longest estrous cycle of any land mammal, lasting approximately 15 to 16 weeks. Effective reproductive management throughout this prolonged cycle, supported by a deeper understanding of reproductive biology and physiology, is therefore essential to improve reproductive success and ensure the long-term survival of this species. Emerging evidence from other species highlights the importance of the vaginal microbiota in modulating fertility and reproductive performance. Nevertheless, the vaginal microbiota of elephants remains largely unexplored.

The objectives of the study were to (1) establish the first standardized protocol for vaginal vestibule microbiota (VVM) sampling in normal cycling Asian elephants (n = 6) and (2) characterize microbial composition, with particular attention to variations between the luteal (n = 3) and follicular phases (n = 3) of the estrus cycle, as determined by serumprogesterone and luteinizing hormone concentrations using enzyme immunoassays. Microbial profiling using 16S rRNA gene sequencing consistently identified Actinomycetota, Bacillota, Campylobacterota, and Spirochaetota as dominant bacterial phyla across all individuals. Significant phase-dependent shifts in microbial composition (Bray-Curtis, GUniFrac, Weighted UniFrac; p < 0.05) were observed. At the genus level, the relative abundance of Campylobacter was higher during the luteal (33.6%) compared to the follicular phases (10.2%) and was identified as a key biomarker significantly enriched in the luteal phase. In contrast, Treponema exhibited approximately twice the relative abundance during the follicular phase compared to the luteal phase. Lactobacillus constituted only 1.3% of the microbial community during the follicular phase and was not detected during the luteal phase.

These findings provide the first baseline characterization of VVM in normal cycling healthy elephants. The luteal phase exhibited greater bacterial diversity, potentially linked to progesterone dominance. These findings highlight the importance of studying microbial dynamics in reproductive cycling, their functional implications for fertility, and applications in elephant conservation management.