Inhibitory effects of different plant extracts on Histomonas meleagridis in vitro and in vivo in chickens

Histomonosis is a protozoan disease that is caused by Histomonas meleagridis, which can lead to cecal inflammation and liver necrosis in poultry. Since the discontinuation of nitarsone in 2015, there is currently a lack of approved prophylactics for managing histomonosis. In search of potential alternatives, the present investigation evaluated the inhibitory effects of seven commercial plant extracts on the in vitro growth of H. meleagridis. Additionally, the in vivo effectiveness of three of the most promising plant extracts was evaluated. The study demonstrated that all seven plant extracts exhibited antihistomonal properties in vitro. Sodium houttuyfonate, emodin, and osthole displayed the highest effectiveness among these extracts, as evidenced by their respective minimal lethal concentration of 0.25, 0.5, and 1 mg/mL. Subsequently, these three plant extracts were employed in additional in vivo testing. The results indicated that all three extracts could mitigate liver and cecum lesion scores in infected chickens while facilitating a degree of body weight gain following infection compared to the challenged control. The group administered with 0.5 g/kg (feed) sodium houttuyfonate exhibited the most pronounced effect, as evidenced by the absence of a significant difference in weight gain compared to the dimetridazole group (P < 0.05). However, the three plant extracts did not fully restore the body weight of infected chickens to levels comparable with the blank control. The experimental results indicate that sodium houttuyfonate, emodin, and osthole possess properties that contribute to the prevention and treatment of histomonosis, with sodium houttuyfonate demonstrating the most favorable results.