Innovative vibriosis control in open aquaculture: Paratapes undulata as a sustainable growth and resistance enhancer in red tilapia

Abstract

This study demonstrates the novel therapeutic potential of Paratapes undulata for mitigating Vibrio alginolyticus infection in red tilapia. In vivo, P. undulata significantly improved growth by approximately 362% in group G3 (Clam-treated Control) and 284% in group G4 (Clam-treated Infected), compared to the infected control group (G2), and reduced mortality by 100% in group G3 and 75% in group G4, compared to the infected control group (G2), and alleviated clinical signs, correlating with enhanced hematological and biochemical profiles, and reduced tissue damage. Mechanistically, P. undulata modulated the immune response by shifting cytokine balance towards anti-inflammation, enhanced antioxidant capacity, and directly inhibited Vibrio alginolyticus virulence. Gas Chromatography-Mass Spectrometry and Fourier-Transform Infrared Spectroscopy analyses revealed the presence of bioactive compounds contributing to these effects. These findings establish P. undulata as a promising, natural, and sustainable biocontrol agent for vibriosis in aquaculture, offering a novel strategy for disease management and reducing reliance on antibiotics. This study suggests that P. undulata can be effectively incorporated into aquaculture feed or water treatments to prevent and manage vibriosis outbreaks.

Keywords: Paratapes undulata; Vibrio alginolyticus; Aquaculture immunology; Natural antimicrobials; Probiotic aquaculture.

Fig. 1

Experimental design: Clam-fish co-culture system.

Fig. 2

Cumulative mortality of red tilapia (%).

Fig. 3

Enumeration of V. alginolyticus in different groups.

Fig. 4

Effect of P. undulata on biochemical parameters in red tilapia.

Fig. 5

Modulation of antioxidant gene expression in P. undulata-treated fish.

Fig. 6

Modulation of metabolic gene expression in P. undulata-treated fish.

Fig. 7

Immune gene expression in response to P. undulata treatment.

Fig. 8

The transcription of all virulence genes including trh, toxR, and tdh was significantly lower in treated group compared to the positive control (p < 0.05).

Fig. 9

Photomicrograph of H&E section of different organs of control negative group showing: a) gills with normal primary and secondary lamellae. b) liver with normal hepatic parenchyma and cellular details.c) spleen with normal parenchyma white and red pulp. d) intestine with normal mucosa, submucosa and serosa. (Scale bar = 100 µm).

Fig. 10

Photomicrograph of H&E section of different organs of red tilapia infected with V. alginolyticus showing: a) gills with diffuse telangiectasis of secondary lamellae (arrows head) with deformities of others. b) gills with severe congestion of blood vessels (thin arrow) with partial fibrosis (thick arrow) and hemorrhage in the gill arch (arrowhead). c) liver with severe vascular congestion with extravasated erythrocytes (thick arrow) with perivascular mononuclear inflammatory cells infiltration (arrowhead). d) liver with diffuse vacuolation of hepatocytes of mainly fatty degeneration (arrows head). e) liver with perivascular inflammatory mononuclear cells infiltration (arrow) and severe vascular congestion (arrow head). f) spleen with severe vascular congestion (arrow head) and focal extravasated erythrocytes (hemorrhage) (thick arrow). g) spleen with focal fibrosis surrounded with inflammatory reaction (thick arrows). h) intestine with moderate focal extravasated erythrocytes in the lamina propria (arrow head) and focal fibrosis of submucosa (arrow). i) intestine with diffuse congestion of submucosal blood vessels (arrows). (Scale bar = 100 µm).

Fig. 11

Photomicrograph of H&E section of different organs of red tilapia subjected to P. undulatus showing: a) gills with apparently normal elongated primary lamellae with normal gill arch and secondary lamellae. b) liver with apparently normal hepatic parenchyma and cellular details except in focal mild cellular vacuolation of mainly hydropic degeneration (arrow head). c) spleen with normal parenchyma and mild subcapsular lymphocytic cellular depletion (arrows head). d) intestine with normal mucosa, submucosa and serosa except in mild submucosal vascular congestion (arrow head). (Scale bar = 100 µm).

Fig. 12

Photomicrograph of H&E section of different organs of red tilapia infected with V. alginolyticus and subjected to P. undulatus showing: a) gills with apparently normal primary lamellae, fusion of some secondary lamellae (arrows) and curving of others (arrow head). b) liver with mild vascular congestion (arrow) and focal mild subcapsular hepatocytes vacuolation (arrow head). c) liver with partial destruction of melano-macrophage centers (thin arrows), mild vascular congestion (thick arrow) and few mononuclear inflammatory cells infiltration (arrow head). d) spleen with well-organized parenchyma and mild focal lymphocytic cells depletion from white pulp (thick arrows). e) spleen with mild vascular congestion (thick arrow) and mild focal lymphocytic cells depletion from white pulp (arrow head). f) intestine with mild submucosal vascular congestion (arrow head) and perivascular mononuclear inflammatory cells infiltration (arrow head). (Scale bar = 100 µm).

Fig. 13

Agar well diffusion assay results of P. undulata Extract and blank on a lawn of pan-drug resistant V. alginolyticus isolate.