# Therapeutic Effects of Psoralea corylifolia and Morus alba Aqueous Extracts on Tetrahymena pyriformis-Infected Guppies (Poecilia reticulata) and Underlying Transcriptomic Mechanisms: Implications for Ciliate Parasite Control

## TL;DR

A herbal mix of Psoralea corylifolia and Morus alba helps guppies survive a ciliate parasite infection by killing the parasite and boosting the fish's immune system.

## Contribution

The study identifies a synergistic herbal combination effective against ciliate parasites and reveals its dual action through transcriptomic analysis.

## Key findings

- The herbal combination of Psoralea corylifolia and Morus alba significantly improved guppy survival against Tetrahymena pyriformis.
- The treatment activated immune-related genes and altered metabolic pathways in gill tissue.
- 577 genes showed altered activity, including those in IL-17 signaling and cytosolic DNA sensing.

## Abstract

Fish farming faces serious losses from parasites like the one causing “white spot disease.” This study tested whether natural Chinese herbs could help protect fish from these tiny invaders. Researchers mixed extracts from ten different herbs and found that a combination of two—Psoralea corylifolia and Morus alba—worked best together to kill the parasites. When sick guppies were given a mild bath in this herbal mixture, most survived, while nearly all untreated fish died. The treatment not only killed the parasites directly but also helped the fish defend themselves. By studying the fish’s gill tissue, scientists discovered that the herbs boosted the fish’s own immune system and changed how their cells used energy to fight infection. This meant the fish could better resist the parasites and recover from damage. Using plant-based treatments like this offers a safer, natural alternative to chemical drugs, which can harm the environment and lead to drug-resistant parasites. This approach could help fish farmers keep their stocks healthy in a more sustainable way.

Tetrahymena pyriformis is biologically similar to Ichthyophthirius multifiliis, the parasite that causes “white spot disease” in fish. Because it has immune evasion genes and grows quickly, T. pyriformis serves as an ideal model for developing treatments against I. multifiliis and related parasites. This study tested water extracts from 10 traditional Chinese herbs against T. pyriformis and identified 5 with strong antiparasitic effects: Morus alba, Psoralea corylifolia, Sophora flavescens, Polygonum cuspidatum, and Pomegranate Peel. Combination tests showed that certain pairs, especially P. corylifolia with M. alba, worked together synergistically. When infected guppies were treated with this herbal combination at a concentration of 1.39 g/L (1:144 dilution), their 10-day survival rate reached 66.7%. Gill tissue analysis identified 577 genes with changed activity after treatment—228 increased and 349 decreased. These genes were linked to immune responses, metabolism, and cell processes. The key differentially expressed genes include those involved in the IL-17 signaling pathway, amino sugar metabolism, and the cytosolic DNA-sensing pathway. These results show that the herbal combination works by both directly killing parasites and boosting the fish’s immune system. This study provides a scientific basis for using natural herbal treatments as an eco-friendly way to control parasitic diseases in aquaculture.