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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
1× 3×
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; 00:1–13.
•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.