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In-feed oxolinic acid-induced histopathological alterations in Nile tilapia Oreochromis niloticus juveniles

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Abstract

Aquaculture urgently requires effective bacterial disease management, necessitating improved regulation of antibiotic application. This study investigated the effects of oral oxolinic acid (OA) administration on Oreochromis niloticus at the dose of 12 (1×) and 36 mg (3×)/kg biomass/day for 7 consecutive days, relative to a control group. The 1× and 3× groups experienced dose-dependent mortalities ranging from 3.33% to 8.33%. The concentrations of OA residues peaked in the plasma, liver, and kidney on day 7 with the muscle tissues showing the greatest amounts. In both groups, the residues persisted even on day 35 post-dosing. Elevated concentrations of malondialdehyde and total nitric oxide were noted, signifying oxidative stress responses, which correlated with the tissue level changes in various organs. Nevertheless, the cohort administered the recommended dose (1×) exhibited recovery following OA discontinuation. Histologically, the kidney had hydropic oedema, degradation of renal epithelium, nephrocalcinosis, vacuolation, and necrosis. Glycogen-type vacuolation, cellular hypertrophy, and cytoplasmic vacuolation were observed in the liver. Gills exhibited epithelial hyperplasia, thinning, curling, thickening of secondary lamellae, and erosion. Intestinal tissues exhibited a depletion of absorptive vacuoles, degradation of the epithelial layer, mucinous degeneration, and necrotic regions. Splenic alterations were confined to necrosis and a slight increase in sinusoidal space. Recovery was noted in the 1× group. However, none of the assessed parameters normalized in the 3× group even after 35 days of dose suspension. The results, thus, indicated that O. niloticus can able to adapt and tolerate OA safely. However, the recommended dose of OA (12 mg/kg biomass/day for 7 days) elicited reversible biological reactions in tilapia and can be utilized in aquaculture with due caution following regulations.
In-feed oxolinic acid-induced histopathological alterations in Nile tilapia
Oreochromis niloticus juveniles
Arya Sen1*, Masud Bora1, Thangapalam Jawahar Abraham1, Avishek Bardhan1, Ratnapriya Das1 and Prasanna Kumar Patil2
1Department of Aquatic Animal Health, Faculty of Fishery Sciences, W. B. University of Animal and Fishery Sciences, Chakgaria, Kolkata 700094, West Bengal, India
2Aquatic Animal Health and Environment Division, ICAR-Central Institute of Brackishwater Aquaculture, Raja Annamalai Puram, Chennai 600028, Tamil Nadu, India
*Email: arya.sen2@gmail.com, 08981250040
ABSTRACT
The effects of oral oxolinic acid (OA) administration on Oreochromis niloticus at the dose of 12 (1×: recommended dose) and 36 mg/kg
biomass/day (3×: overdose) for 7 consecutive days, relative to a control group were investigated. The 1× and 3× groups experienced dose-
dependent mortalities ranging from 3.33% to 8.33%. Histological observations were carried out in the kidney, liver, gill, spleen, and intestine.
The OA residues peaked in the plasma, liver, and kidney on day 7 of administration with the muscle tissues showing the greatest amounts. In
both groups, the residues persisted even on day 35 post-dosing. Elevated levels of malondialdehyde and total nitric oxide were noted,
signifying oxidative stress responses, which correlated with the tissue level changes in various organs. Nevertheless, the cohort administered
the recommended dose exhibited recovery following OA discontinuation. Recovery was noted in the 1× group. However, none of the assessed
parameters normalized in the 3× group even after 35 days of dose suspension. The results, thus, indicated that O. niloticus can able to adapt
and tolerate OA safely. However, the recommended dose of OA (12 mg/kg biomass/day for 7 days) elicited reversible biological reactions in
O. niloticus and can be utilized with due caution following regulations in aquaculture.
INTRODUCTION
Aquaculture contributes significantly to global fish production,
with Asian countries accounting for 70% of the total output.
Inland fisheries account for 12.5% of total production (FAO
2024).
Cichlids are farmed in 140 countries, with most production
concentrated in Southeast Asia. Southeast Asian countries
particularly emphasise tilapia cultivation, with the Nile tilapia
accounting for 80% of production, making it the second most
significant finfish group. However, issues with disease and
biosecurity have restricted its use (FAO 2024).
Disease outbreaks in tilapia hinder growth, impacting fish
quality, safety, and market access. Streptococcal and viral
diseases, including the Tilapia Lake Virus, pose significant
threats. The aquaculture industry is at risk due to increasing
new infectious pathogens (Patil et al. 2022).
OA is a widely used antibiotic in aquaculture but is not
regulated in India. Scientific research is needed to develop
guidelines for responsible use and biocompatibility with
antibiotics in Indian aquaculture (Abraham et al. 2023).
OBJECTIVES
To assess the accrual and depletion of OA residues in the
edible tissue and oxidative stress parameters in Oreochromis
niloticus juveniles upon oral administration.
To study histopathological alterations in the vital organs of
OA-dosed O. niloticus juveniles.
METHODOLOGY
RESULTS AND DISCUSSION
1a 1a 1a 1a 1a 1a
1a
2b 3b 1a 1a 1a
1a
2c 3c
4b 4b 1a
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
1.80
Day 0 OD Day 7 OD Day 7 POD Day 14
POD Day 21
POD Day 35
POD
MDA (µm)
0 mg (0×) 12 mg (1×) 36 mg (3×)
1a 1a 1a 1a 1a 1a1a
2b 3b
4b
1a 1a
1a
2c
3c 4c 5b
6b
0
20
40
60
80
100
120
140
160
180
200
Day 0 OD Day 7 OD Day 7 POD Day 14
POD Day 21
POD Day 35
POD
TNO (µm)
0 mg (0×) 12 mg (1×) 36 mg (3×)
0
50
100
150
200
250
300
OA residues (µg/kg)
Plasma Muscle Liver Kidney
7 OD 14 POD7 POD 21 POD 28 POD 35 POD 7 OD 14 POD7 POD 21 POD 28 POD 35 POD
Gill Kidney Liver Spleen Intestine
1×
Day 7
OD
1×
Day 35
POD
3×
Day 7
OD
3×
Day 35
POD
OA-dosing (OD) impacted the fish health status, dose-dependently.
At the recommended dose, OA caused reduced feed intake, and increased
mortality, histopathological alterations, and oxidative stress.
OA residues in fish tissues peaked on day 7 of dosing and depleted rapidly
by day 35 post-OA-dosing (POD) highlighting rapid absorption,
distribution, and elimination.
Dose-dependent recovery was observed during the POD period.
The fast elimination of OA residues suggested safety for both fish and
consumers.
Due to the rising concerns about antimicrobial resistance, responsible use
of the antibiotic is warranted.
CONCLUSIONS
REFERENCES
FAO. 2024. The State of World Fisheries and Aquaculture 2022. Towards Blue Transformation. Rome.
Abraham TJ, Patel JB, Bardhan A., et al. 2023. Safety, tolerability and biological responses of Oreochromis
niloticus juveniles upon oral oxolinic acid administration. J Vet Pharmacol Therap 2023; 00:113.
Patil PK, Mishra SS, Pradhan PK, et al. 2022. Usage pattern of chemicals, biologicals, and veterinary
medicinal products in Indian aquaculture. Rev Aquac 14(4):2038-2063.
ACKNOWLEDGEMENTS
The authors thank the Vice-Chancellor, West Bengal University of Animal and Fishery Sciences, Kolkata, for
providing the necessary facilities and the Indian Council of Agricultural Research (ICAR), Government of India
for financial support to carry out this work.
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Article
Full-text available
The use of chemicals, biologicals and veterinary medicinal products (VMPs) helps in healthy and sustainable fish production. Information on the use of these products is essential for assessing farming practices, potential human health and environmental risks. A questionnaire‐based nationwide survey covering aquaculture farms (n = 2936) producing carps, tilapia, pangasius and rainbow trout in freshwater and shrimp in brackishwater estimated the use of 52 different types of inputs which included disinfectants (597 g t−1), probiotics (2.28 kg t−1), environmental modifiers (22.82 kg t−1), nutritional supplements (1.96 kg t−1), natural anti‐infective agents (293 g t−1), herbicide and piscicides (844 g t−1), antibiotics (2 mg PCU−1), antifungal (4 mg PCU−1), and antiparasitic (14 mg PCU−1) agents. The bulk of these inputs was used for soil and water quality improvement and had low environmental and human safety concerns. The multivariate analysis revealed significant variation in the frequency and quantity of compounds use among farm groups. Redundancy analysis revealed a significant association between the number of products used and stocking density. The survey also showed a considerable influence of education and farming experience on the usage pattern of aquaculture inputs. Results of the study indicated greater reliance of farmers on the use of disinfectants for biosecurity, nutritional supplements for enhanced growth and environmental modifiers for maintaining soil and water quality in culture systems. Though there was no use of restricted antibiotics and antiparasitic agents, the development and implementation of standard regulatory guidelines are essential for safe and effective use of inputs for sustainable aquaculture.