Bridging Livestock and Aquaculture: Surveillance of Antimicrobial Resistance Pathways in Nigerian Fish Ponds Fertilized with Animal Waste

1. Overview

Antimicrobial resistance (AMR) is a global health challenge, with serious implications for aquaculture. Fish farming is vital for food security, particularly in low- and middle-income countries, but the overuse of antibiotics threatens both productivity and public health. In Nigeria, aquaculture ponds are often fertilized with untreated cattle dung or poultry manure, creating a major but underexplored pathway for resistant bacteria to enter aquatic environments.

This study aims to investigate the prevalence, resistance patterns, and resistance genes of Salmonella spp. and other enteric bacteria in manure-fertilized aquaculture systems in Osun and Oyo States, Nigeria. By extending prior research on AMR in livestock waste, the project will identify risks, map transmission routes, and recommend practical strategies to reduce antibiotic dependence in aquaculture.

Facilities and Resources: Laboratory work will be conducted at the Department of Microbiology, Obafemi Awolowo University (OAU) Ile-ife and Omololu Hospital Laboratory, Ibadan Nigeria. Both facilities have microbiology and molecular biology capacity. Oversight will be provided by Prof. Joseph Omololu-Aso (Professor of Clinical Microbiology and Infectious Diseases, OAU; CEO, Omololu Hospital; Director General, CPM International Research Institute). Ethical approval will be sought from the OAU Research Ethics Committee.

Estimated Timeline: The project will run for 12 months:
- Months 1–2: Ethics approval, farm recruitment, pilot testing.
- Months 3–6: Field sampling and microbiological culture.
- Months 7–9: Molecular confirmation and antibiotic susceptibility testing.
- Months 10–12: Data analysis, dissemination, and open-access reporting.

Open Science Commitment: All protocols, datasets, and analysis scripts will be preregistered and shared via ResearchHub. Quarterly updates will be posted, and a preprint will be prepared for open-access dissemination.

2. Introduction

Aquaculture is the fastest-growing food sector globally, contributing to nutrition, livelihoods, and economic development. However, the sector faces severe disease burdens, often managed by routine antibiotic use. This practice accelerates antimicrobial resistance (AMR), leading to the emergence of multidrug-resistant (MDR) pathogens such as Salmonella, Vibrio, and Escherichia coli. Resistant strains compromise fish health, reduce productivity, and pose direct risks to human populations through foodborne transmission and environmental contamination.

Globally, the Food and Agriculture Organization (FAO) estimates that more than 70% of antibiotics used in aquaculture are administered prophylactically, often without veterinary oversight. Studies in Asia (China, Vietnam, Bangladesh) have revealed high prevalence of tetracycline and sulfonamide resistance genes in aquaculture ponds. In Europe, resistant Vibrio spp. have been detected in salmon farms, while in South America, resistant Aeromonas spp. have been reported. In Africa, however, data are limited, leaving significant gaps in surveillance and management strategies.

In Nigeria, aquaculture is expanding rapidly, with thousands of smallholder farms contributing to national food supply. A common practice is the use of untreated cattle dung and poultry manure to fertilize ponds, enhancing algal growth and fish productivity. While cost-effective, this practice likely introduces resistant bacteria from livestock into aquaculture systems. My prior undergraduate study in Ile-Ife town confirmed this risk: 50% of cattle dung samples carried Salmonella spp., with resistance to Amoxicillin (75%) and Augmentin (60%). These findings highlight untreated manure as a reservoir of resistance genes.

Rationale: This study addresses a critical gap by linking terrestrial livestock waste to aquatic AMR pathways. It will provide empirical evidence of MDR bacteria in fish ponds, identify specific resistance genes, and assess management practices that reduce risks. The project aligns with the One Health framework, recognizing the interconnectedness of human, animal, and environmental health.

Research Questions:
- RQ1: What is the prevalence of MDR Salmonella and other enteric bacteria in aquaculture ponds fertilized with animal waste?
- RQ2: Which resistance genes (tet, bla, sul) are most commonly detected in aquaculture isolates?
- RQ3: What pond management practices are associated with reduced AMR prevalence?

Hypotheses:
- H1: Ponds fertilized with animal manure harbor higher MDR prevalence than non-manure ponds.
- H2: Detected resistance genes correspond to antibiotics commonly used in livestock (Septrin, Streptomycin, Augmentin, Amoxicillin).
- H3: Proper manure treatment and pond management practices reduce AMR prevalence.

Impact Statement: This study will provide actionable evidence to strengthen sustainable aquaculture practices in West Africa. Findings will guide policy on manure management, inform One Health interventions, and support fish farmers by highlighting strategies that safeguard productivity and food safety.

3. Methods

Participants and Sample
The project will be conducted by a multidisciplinary team with expertise in microbiology, infectious diseases, and aquaculture.

Lead investigator: Akoledowo Eniola (Microbiologist, early-career researcher).

Supervisory team: Prof. Joseph Omololu-Aso (OAU, Omololu Hospital, CPM International Research Institute), Dr. (Mrs.) Omololu-Aso (CMD, Omololu Hospital), Mr. Olaoye Damilola (CPM International Research Institute).

Supporting team: postgraduate students of Prof. Omololu-Aso at OAU and staff at Omololu Hospital Laboratory.

Sample Collection:
- Farms: 10 fish farms in Osun and Oyo States (5 manure-fertilized, 5 controls).
- Samples: 60 total (pond water, sediment, manure inputs, fish gills/intestines).
- Sample Size Justification: Power analysis indicates 60 samples provide ≥80% power to detect a 25% difference in MDR prevalence between groups (α = 0.05).
- Inclusion: Active farms ≥6 months old. Exclusion: Recently disinfected or inactive ponds.

Materials and Procedures
- Sample Collection: Sterile swabs and containers; cold-chain transport.
- Microbiological Culture: Isolation on Salmonella-Shigella agar, MacConkey agar, and nutrient agar.
- Biochemical Identification: Gram staining, catalase, citrate, and sugar fermentation tests.
- Molecular Analysis: PCR detection of tet, bla, and sul genes.
- Antimicrobial Susceptibility Testing: Kirby-Bauer disk diffusion on Mueller-Hinton agar.
- Laboratories: OAU Department of Microbiology and Omololu Hospital Laboratory.

Planned Analyses
1. Preprocessing: Verification of isolate identity, removal of duplicates, standardization of antibiograms.
2. Statistical Testing:
   - Descriptive statistics for prevalence of resistant isolates.
   - Chi-square tests for group comparisons.
   - Logistic regression for associations between farm practices and AMR prevalence.
3. Hypothesis-Specific Predictions:
   - H1: If manure-fertilized ponds harbor higher MDR prevalence, Chi-square results will be significant.
   - H2: If AMR genes correspond to veterinary antibiotic use, PCR will reveal tet, bla, sul dominance.
   - H3: If improved practices mitigate AMR, regression will show reduced odds ratios.
Contingency Plan:
- IF sample size per farm is smaller than expected, THEN aggregate at group level.
- IF unexpected genes are detected, THEN pursue supplementary sequencing within budget.

Ethics and Data Management
- Ethical Approval: To be obtained from OAU Research Ethics Committee.
- Confidentiality: Farmer identities anonymized; results reported in aggregate.
- Data Sharing: Raw data, protocols, and analysis scripts deposited in open-access repository linked to ResearchHub.
- Oversight: Prof. Omololu-Aso and Dr. (Mrs.) Omololu-Aso will ensure compliance with ethical and biosafety standards.

4. Pilot Data

My undergraduate project in Ile-Ife (Osun State, Nigeria) demonstrated that 50% of cattle dung samples carried Salmonella spp. Isolates showed high resistance: Amoxicillin (75%), Augmentin (60%), Septrin (55%), Streptomycin (15%). These findings confirm that untreated livestock waste is a reservoir for resistant bacteria, justifying further study in aquaculture.

5. Budget

Total Requested: USD$5,000

- Consumables ($2,000): Culture media, reagents, antibiotic discs, PCR kits, DNA extraction supplies.
- Minor Equipment ($1,200): Micropipettes, electrophoresis accessories, PCR consumables.
- Field Sampling ($1,000): Transportation, sampling kits, cold storage.
- Personnel Support ($500): Research assistants, farmer liaison.
- Data Analysis & Dissemination ($300): Preprint preparation, repository upload, presentations.

Justification: Laboratory consumables and molecular kits form the largest share due to intensive culture and PCR analysis. Field sampling funds ensure repeated farm visits. Personnel costs support trained assistants for data collection. Dissemination costs align with ResearchHub’s open science mandate.

6. References

1. Cabello, F. C. (2006). Heavy use of prophylactic antibiotics in aquaculture: a growing problem for human and animal health and for the environment. Environmental Microbiology, 8(7), 1137–1144.
2. Chiu, C. H., Su, L. H. & Chu, C. (2004). Salmonella enterica serotype Choleraesuis: epidemiology, pathogenesis, clinical disease, and treatment. Clinical Microbiology Reviews, 17(2), 311–322.
3. Hyeon, J. Y. et al. (2011). Prevalence, antibiotic resistance, and molecular characterization of Salmonella serovars in retail meat products. Journal of Food Protection, 74(1), 161–166.
4. Majowicz, S. E., Musto, J., Scallan, E., et al. (2010). The global burden of nontyphoidal Salmonella gastroenteritis. Clinical Infectious Diseases, 50(6), 882–889.
5. McGuinness, S., McCabe, E., O’Regan, E., et al. (2009). Development and validation of a rapid real-time PCR based method for the specific detection of Salmonella on fresh meat. Meat Science, 83, 555–562.
6. Sayah, R. S., Kaneene, J. B., Johnson, Y., & Miller, R. (2004). Patterns of antimicrobial resistance observed in Escherichia coli isolates obtained from domestic- and wild-animal fecal samples, human septage, and surface water. Applied and Environmental Microbiology, 71(3), 1394–1404.
7. World Health Organization (2013). Salmonella (non-typhoidal). WHO Fact Sheet.

Bridging Livestock and Aquaculture: Surveillance of Antimicrobial Resistance Pathways in Nigerian Fish Ponds Fertilized with Animal Waste

Bridging Livestock and Aquaculture: Surveillance of Antimicrobial Resistance Pathways in Nigerian Fish Ponds Fertilized with Animal Waste

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Related Funding

Request for Proposals - Antimicrobial Resistance (AMR) in Aquaculture

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