In vitro and in vivo effects of Acacia mearnsii De Wild extract for cyathostomin control in horses.

Overview

• This study evaluated the effects of Acacia mearnsii extract, a tannin source, on controlling cyathostomin parasites in horses, testing both in laboratory (in vitro) conditions and in living animals (in vivo).

Introduction and Background

• Cyathostomins are common parasitic nematodes (small worms) infecting horses, causing health issues and performance decline.
• Anthelmintic resistance—the reduced effectiveness of standard deworming drugs—has prompted research into alternative parasite control methods.
• Plant extracts rich in tannins, such as from Acacia mearnsii, have shown potential anthelmintic (anti-worm) activity.

Objectives

• To assess the efficacy of Acacia mearnsii extract on cyathostomin control in horses.
• To test the effects both in vitro (egg hatchability tests) and in vivo (fecal egg count reduction in naturally infected horses).
• To monitor any physiological or health impacts using body weight, body condition, and blood analyses.

Methods

• Subjects: 30 naturally cyathostomin-infected Pantaneiro horses were selected from two farms (Farms A and B).
• Parasite Confirmation: Third-stage larvae from initial samples were confirmed to be cyathostomins.
• In Vitro Testing: Egg hatchability tests (EHT) were conducted on fecal samples to determine effective concentration (EC50) of the A. mearnsii extract that inhibits egg hatching.
• In Vivo Testing: Two 28-day randomized field trials performed to evaluate fecal egg count reduction (FECRT) with measurements on days 0, 7, 14, 21, and 28.
• Diet and Treatment: Horses were fed panicum grass, 1 kg concentrate, 40 g sugarcane molasses (control group), and a treatment group received 25 g of A. mearnsii extract instead of molasses.
• Health Monitoring: On days 0 and 28, body weight (BW), body condition score (BCS), and blood samples for hematological and biochemical assays were collected.

Results

• In vitro results:
  • EC50 (concentration needed to reduce egg hatching by 50%) was 13.2 mg/mL for Farm A and 14.9 mg/mL for Farm B, indicating the extract was effective at inhibiting egg hatchability in lab conditions.
• In vivo results:
  • The fecal egg count reduction test (FECRT) showed minimal egg count reduction (3.09% control group, 3.18% treated group), with no significant differences (P > 0.05) between groups.
  • This suggests the extract did not meaningfully reduce parasite egg shedding in live horses during the 28-day trial.
• Health Parameters:
  • No significant differences in body weight, body condition score, or blood hematological and biochemical parameters between treatment and control groups (P > 0.05).
  • Indicates the extract did not negatively affect general health or cause hematological toxicity over the trial period.

Conclusions

• Acacia mearnsii tannin extract demonstrated a capacity to reduce cyathostomin egg hatchability under laboratory conditions, confirming its anthelmintic properties in vitro.
• However, these in vitro effects did not translate into reduced parasite loads in naturally infected horses over the 28-day field trial.
• The extract was safe with no adverse effects on body condition or blood health markers.
• Additional research may be needed to optimize dosing, delivery, or combination strategies for tannin extracts to become effective anthelmintic alternatives in vivo.