Date of Graduation

8-2025

Document Type

Thesis

Degree Name

Bachelor of Science in Agricultural, Food and Life Sciences

Degree Level

Undergraduate

Department

Poultry Science

Advisor/Mentor

Graham, Danielle

Committee Member

Parsons, Ben

Second Committee Member

Hargis, Billy

Abstract

Histomonas meleagridis is a protozoan parasite and the causative agent of histomonosis in gallinaceous birds. There are currently no approved prevention or treatment options available for histomonosis control in the United States. Mortality in affected turkey flocks can exceed 80% which highlights the urgent need for research investigating novel strategies to mitigate histomonosis in the field. The objective of this study was to evaluate the in vitro antihistomonal and antibacterial effects of of methyl jasmonate (MeJA) and jasmonic acid (JA), two plant-derived compounds, in a xenic culture of H. meleagridis. Assays were conducted using cultured H. meleagridis (PHL strain) treated with varying concentrations of MeJA (0.5–10 mM; 3 assays) and JA (1–10 mM; 2 assays). Viable histomonad concentration (Log10 H. meleagridis cells/mL) was determined at 44-48 hours post-incubation at 40C. Chromagar Orientation agar was used for bacterial recovery (Log10 CFU/mL) in MeJA assay 3 and JA assay 1. Across the MeJA assays, treatment with MeJA ≥7.5 mM significantly (P ≤ 0.05) reduced H. meleagridis to a non-detectable level compared to the non-treated control. Bacterial recovery was significantly higher in the groups treated with 5 mM (7.85 ± 0.12) and 10 mM (7.81 ± 0.03) of MeJA compared to the non-treated control (6.77 ± 0.03) and the group treated with 1 mM of MeJA (7.09 ± 0.13), suggesting a trend of increasing bacterial growth as histomonad viability declined. In both JA assays, H. meleagridis concentration was significantly reduced in all groups treated at 1 mM, 5 mM, and 10 mM compared to the non-treated control. Although the effect of JA at all concentrations was significant, the effect of JA only reduced histomonad concentration by < 1 log compared to the non-treated control group. In Assay 1, bacterial recovery was markedly reduced in the group exposed to 10 mM JA (8.26 ± 0.02) compared to the non-treated control (8.68 ± 0.12). These results suggest that MeJA potency and effect on histomonad growth in vitro is more pronounced than JA and that the impact of both compounds on H. meleagridis was not related to inhibition of the bacterial population in the xenic culture. Research is underway to assess the prophylactic and therapeutic effect of MeJA treatment in H. meleagridis infected turkeys.

Keywords

Histomonosis; Poultry disease; Parasitology; Microbiota; Antiparasitic activity

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Available for download on Wednesday, July 08, 2026

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