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Tetracycline and sulphonamide residues in farmed fish in Dar es Salaam, Tanzania and human health risk implications
Abstract
In Africa, antibiotic residue investigations in animal food have primarily been focused on meat, neglecting farmed fish. This cross-sectional study conducted in Dar es Salaam, Tanzania, aimed to assess sulphonamide and tetracycline residues in farmed fish, comparing levels with Codex Alimentarius Commission's acceptable daily intake (ADI) and maximum residue limits (MRLs). A total of 84 farmed fish were sampled and analysed in the presence of tetracycline and sulphonamide residues. All samples were positive for sulphonamide residues (100%; n = 84), and 2.4% (n = 2) were positive for tetracycline and consequently also positive for both compounds. Tetracycline levels were below ADI and MRL, 28.5% (n = 24) surpassed the ADI, and 6% (n = 5) of the samples exceeded the MRL for sulphonamide. Regular monitoring of antibiotic residues in aquaculture products is crucial to mitigate health risks and expanding assessments to include other commonly used compounds is warranted.
... Over the past decade, global pesticide use has increased significantly to support high crop production for the growing population (Chen et al. 2023;Chou et al. 2024;Yuan et al. 2024). This continuous use has led to the presence of pesticide residues in the food chain, which includes deposits of active pesticide components, metabolites, or breakdown products (Kilusungu et al. 2024;Rahman A et al. 2024;Moussaif et al. 2024). The longterm health implications of pesticide residues in food webs encompass cancer, reproductive harm, and endocrine disruption, whereas short-term effects may manifest as headaches and nausea (Végh et al. 2023; Barbosa et al. 2023). ...
This study analysed pesticide residues in cauliflower (Brassica oleracea botrytis) and bitter gourd (Momordica charantia), two widely consumed vegetables in Bangladesh, and assessed the associated human health risks. Vegetables were analysed using a modified QuEChERS extraction, followed by gas chromatography with flame thermionic and electron capture detectors. Results showed that in 36.7% of the samples pesticide residues were detected, 90.9% of which exceeding the MRLs of the European Commission, so highlighting serious food safety concerns. Multiple residues were detected in some samples, with chlorpyrifos being the most common present, followed by diazinon, dimethoate and quinalphos. Human health risks, calculated by estimated daily intake and hazard index, indicated potential non-carcinogenic risks from the present pesticides. This study may assist policymakers and authorities in developing strategies for safe vegetable production and quality monitoring to ensure food safety.
Background
Antimicrobial resistance is a global problem and involve pathogens which have the potential to move between food producing animals and humans by direct exposure or through the food chain or the environment. The objective of this study was to determine the performance in addressing antimicrobial resistance in Kenya, Tanzania, Uganda and Zambia. Desk review and in-depth interviews were employed for data collection. Interviews were conducted with national antimicrobial resistance focal officials.
Results
The findings indicate that in the four countries there was minimal capacity to conduct AMR surveillance. There were few well-established laboratories in tertiary hospitals, both private and public hospitals. The animal, environment and agricultural sectors in all countries had limited capacity in conducting antimicrobial resistance surveillance. There is limited data on antimicrobial resistance in all the four countries, and regional data sharing was limited. In all the four countries, data from research institutions were not linked using standardized system making difficult to compile the national database. The capacity for microbiological culture, identification and antimicrobial sensitivity testing using standardized protocols was available in the four countries. The interventions adopted by the countries included development of National Action Plans on antimicrobial resistance and setting up of multi-sectoral national coordinating structures.
Conclusions
Based on this findings, the countries need improved National Integrated Antimicrobial Resistance Surveillance systems to include community settings, involving antimicrobial use and resistance in human, animal, food, and environment sectors. In addition, the region requires clear antimicrobial resistance data sharing protocol for quick comparability of the data across the region. This is important in driving antimicrobial resistance agendas at regional level, which will eventually trigger collective actions.
As the number of inhabitants in Sub-Saharan Africa (SSA) increases, demand for animal-source proteins outstrips the current supply. Aquaculture is promoted to sustain livelihood and for improved food security. However, the production in SSA is still low at less than 1% of the total global production. Poor water quality is cited to be one of the factors limiting the growth of the aquaculture sector and is attributed to limited familiarity with standard aquaculture practices. Thus, a knowledge, attitudes, and practices (KAPs) survey was carried out among fish farmers in five districts of the Rwenzori region. Our results showed that 81% and 80% of them had poor knowledge and practices concerning water quality in aquaculture, respectively. Seventy percent did not know that fish farming caused pollution, while 68% believed that there was no need to treat fish farm effluents. Only 45% showed good attitudes towards water quality management. Fish farmers that fed fish with only complete pellets and those that combined them with locally available products (LAP) were 8 and 5 times more likely to possess more knowledge (p < 0.01) on water quality as compared to others that used only LAP. Slight improvements in attitudes and practices for every unit increment in knowledge were observed (p < 0.05). This limited familiarity with water quality management could severely impede the growth of aquaculture, as well as the sustainable utilization of available water resources. Therefore, there is a need for more training and improvement of extension services among fish farming communities.
Antimicrobial resistance (AMR) is a significant threat to global public health. Specifically, excessive usage of antimicrobials in food animal production is one significant reason for AMR development in humans. Therefore, it is essential to identify the trends of AMR in fish and poultry and develop better surveillance strategies for the future. Despite this imperative need, such information is not well documented, especially in Africa. This study used a systematic review to assess AMR trend, spatial distribution, and incidence in fish and poultry research in Nigeria, Egypt, and South Africa. A literature assessment was conducted for published studies on AMR between 1989 and 2021 using the Scopus and Web of Science databases. One hundred and seventy-three relevant articles were obtained from the database search. Egypt was the leading exponent of antimicrobial resistance research (43.35%, 75 studies), followed by Nigeria (39.31%, 68 studies), then South Africa (17.34%, 30 studies). The majority of the antimicrobial resistance studies were on poultry in Egypt (81%, 61 studies), Nigeria (87%, 59 studies), and South Africa (80%, 24 studies). Studies on fish were 17% (13 studies), 9% (6 studies), and 10% (3 studies) in Egypt, Nigeria, and South Africa, respectively. Antimicrobial resistance patterns showed multiple drug resistance and variations in resistant genes. AMR research focused on sulfamethoxazole groups, chloramphenicol, trimethoprim, tetracycline, erythromycin, and ampicillin. Most studies employed the disk diffusion method for antimicrobial susceptibility tests. Among the four mechanisms of AMR, limiting drug uptake was the most reported in this study (both in fish and poultry). The findings reveal public and environmental health threats and suggest that it would be useful to promote and advance AMR research, particularly for countries on the global hotspot for antimicrobial use.
In Tanzania, the increased demand for animal-derived foods, particularly eggs, meat, and milk, has resulted in the intensification of farming systems with the use of antimicrobials, particularly sulphonamides and tetracyclines. According to the FAO/WHO Codex Alimentarius commission, concentrations of antimicrobial residues in food exceeding the acceptable daily intake (ADI) and maximum residual limit (MRL) pose a health risk to consumers. This cross-sectional study determined the concentrations of sulphonamide and tetracycline residues in the liver tissues of commercial broiler chicken sold in Dar es Salaam, Tanzania, to find out whether the amounts of residues were within the legally permitted and acceptable limits in food. We conveniently sampled eighty-four liver tissue samples from broiler chicken sold in two out of six large markets in Dar es Salaam. The amounts of tetracycline and sulphonamide residues were determined using an ELISA kit (Shenzhen Lvshiyuan Biotechnology Company, Shenzhen, China). The results showed that all 100% (n = 84) samples contained tetracycline residues and 21.4% (n = 18) samples contained sulphonamide residues, while 21.4% (n = 18) contained both sulphonamide and tetracycline residues. The concentrations of sulphonamide residues were within the maximum residual limit (MRL). However, 90.5% (n = 76) of the samples had tetracycline levels that exceeded the acceptable daily intake (ADI) range 0–3 µg/kg and 13.1% (n = 11) of the samples had tetracycline levels that exceeded the maximum residue limit of 300 µg/kg. The observed presence of antibiotic residues in the poultry tissues poses a health risk to consumers, and may lead to antimicrobial resistance micro-organisms, which may spread to humans and animals via the environment. Vigorous surveillance and observation of the withdrawal periods should be advocated to ensure that the food from animals is safe with regard to the residues of veterinary medicines.
The intensification of aquaculture in Cameroon requires efficient screening methods to control veterinary drug residues in fish. This is why the charm II radio receptor technique for the detection of antimicrobial residues in aquaculture fish initiated in Belgium was transferred to Cameroon according to Commission Decision 2002/657/EC. The validation parameters included the following tests: repeatability, reproducibility and robustness in addition to the mandatory characteristics, detection capability and specificity. Selected veterinary drug-free fish samples of tilapia (Oreochromis niloticus), catfish (Clarias gariepinus), carp (Cyprinus Carpio) and kanga (Heterotis niloticus) were spiked at different target concentrations with different antimicrobials (β-lactams, tetracycline, sulfonamides, macrolides and chloramphenicol). The detection capabilities (CCβ) were at MRPL (0.3 µg/kg for chloramphenicol), or below the regulatory limits in a range of 0.25-0.5 MRL with 0% false-negative results. β-lactams (penicillin G), tetracyclines (tetracycline, chloretetracycline and oxytetracycline) and macrolides (erythromycine A) were detected at half MRL (25, 50 and 100 µg/kg respectively), while sulfonamides (sulfamethazine) was detected at 25 µg/kg (0.25 MRL). The detection capabilities (CCβ) obtained were satisfactory as the cut-off factors (Fm) were less than the mean values of blank fish readings (B) (Fm < B). Furthermore, the method was applicable since the cut-off factor was less than the positivity threshold (Fm < T). The variability of the data under repeatability and reproducibility conditions was acceptable, with a relative standard deviation less than 15%. Results were unaffected by delaying the reading time from 0 h to 24 h after the addition of scintillation fluid, with a precision below 16%. Likewise, non-target drugs were not detected even at high concentrations (100 MRL) in a cross-reactivity study. From the overall results, the performance characteristics (detection capabilities, precision, robustness and specificity) were suitable and comparable to the initial validation results, indicating that the transfer to Cameroon laboratory was valid, the method was reliable and could be used in aquaculture fish quality monitoring programs in Cameroon.
The fisheries sector of Tanzania is dominated by small-scale fishers who produce up to 95% of the total amount of fish caught in the country. The small-scale fisheries are constrained by inadequate infrastructure, including a lack of capacity for processing and cold storage facilities, poor transportation and fishing tools that increase post-harvest losses. Small-scale fishers lack sufficient capital and skills to invest in modern fishing technologies. Additionally, social-demographic aspects of the fishers, such as education level, gender, age, fishing experience and training influence access to fishing resources and capital, leading to variation in fish catch and post-harvest losses. Thus, this study examined factors that influence fish catch and spoilage in small-scale fisheries in the Bagamoyo District, Tanzania. Forty randomly selected fishers from the Mlingotini fishing village were interviewed. The results show that after spending an average of 11 hours per fishing session, the fishers catch an average of 18.5 kg of fish. The amount of fish captured differed with fishing experience, age and sex of the fisher, education level of the fisher, and the time spent selling the captured fish. On average, 10% of the weight of the fish captured per fishing session spoils. The level of spoilage varied according to the fisher’s age and sex, education level, fishing experience, length of fishing session, and fishing gear used. Provision of training related to fish processing and handling and improvement of cold storage and transport facilities are recommended to reduce spoilage.
Antibiotics are among the essential veterinary medicine compounds associated with animal feed and food animal production. The use of antibiotics for the treatment of bacterial infections is almost unavoidable, with less need to demonstrate their importance. Although banned as a growth factor for a few years, their use in animals can add residues in foodstuffs, presenting several environmental, technological, animal health, and consumer health risks. With regard to human health risks, antibiotic residues induce and accelerate antibiotic resistance development, promote the transfer of antibiotic-resistant bacteria to humans, cause allergies (penicillin), and induce other severe pathologies, such as cancers (sulfamethazine, oxytetracycline, and furazolidone), anaphylactic shock, nephropathy (gentamicin), bone marrow toxicity, mutagenic effects, and reproductive disorders (chloramphenicol). Antibiotic resistance, which has excessively increased over the years, is one of the adverse consequences of this phenomenon, constituting a severe public health issue, thus requiring the regulation of antibiotics in all areas, including animal breeding. This review discusses the common use of antibiotics in agriculture and antibiotic residues in food/feed. In-depth, we discussed the detection techniques of antibiotic residues, potential consequences on the environment and animal health, the technological transformation processes and impacts on consumer health, and recommendations to mitigate this situation.
The study assessed antimicrobial drug use, pattern, and the occurrence of residues in farmed fish, as well as the level of awareness of drug residues amongst fish farmers in Kaduna State. A total of 300 fish samples from 30 farms in the three senatorial districts of Kaduna State were screened for the presence of antimicrobial drug residues. One hundred questionnaires were administered to fish farmers. Out of the 300 fish samples screened, antimicrobial drug residues were detected in 73.70%. An overall prevalence of 73.70% was obtained, while the prevalence of 63, 74, and 84% was obtained from Kaduna North, Central, and South senatorial districts respectively. From the questionnaire responses, the use of antimicrobial drugs in fish ponds was common (91.86%); with tetracycline (63.41%) being the most frequently used. Self-prescription and administration of drugs by farmers (67.86%) were more in number than those who consult veterinarians for prescription and drug administration. The level of awareness on antimicrobial drug residues in fish and dangers associated with the use and consumption of these residues were very low. Furthermore, the majority of the farmers did not observe antibiotic withdrawal periods before sales of fish to consumers. This study has established a high prevalence of antimicrobial drug residues in farmed fish in the study area. In addition, awareness of the dangers and public health implications of antimicrobial drug residues in fish amongst farmers in Kaduna is low. Therefore, the use of the antimicrobial drug in aquaculture should be regulated and farmers should be encouraged to use immunostimulators or probiotics for disease control and prevention, to safeguard the general populace from the hazards associated with drug residues in fish.
In Africa, there is dearth of information on antimicrobial use (AMU) in agriculture and food production systems and its consequential resistance in pathogens that affect animal, human and environmental health. Data published between 1980 and 2021 on the magnitude of AMU and AMR in agriculture and food productions systems in Africa were reviewed. Data from 13–27 countries in Africa indicate that 3558–4279 tonnes of antimicrobials were used in animals from 2015 to 2019. Tetracyclines and polypeptides contributed the largest proportion of antimicrobials used. Cattle and poultry production account for the largest consumption of antimicrobials in Africa. Although limited studies have reported AMR in crops, fish and beekeeping, AMR from a variety of farm animals has been substantially documented in Africa. Some countries in Africa have developed policies/plans to address AMU and AMR in agriculture and food production systems; however, their enforcement is challenged by weak regulations. In conclusion, although there is limited information on the quantities of antimicrobials used in agriculture and food production system, the levels of AMR are high. There is a need to strengthen regulatory authorities with a capacity to monitor AMU in agriculture and food production systems in Africa.
All infections are potentially curable as long as the etiological agents are susceptible to antimicrobials. The increased rate at which antimicrobials are becoming ineffective is a global health risk of increasing concern that threatens withdrawal of beneficial antimicrobials for disease control. The increased demand for food of animal origin, in particular eggs, meat and milk has led to intensification and commercial production systems where excessive use and misuse of antimicrobials may prevail. Antimicrobials, handled and used by farmers and animal attendants with no formal education, may be predisposed to incorrect dosages, misuse, incorrect applications and non-adherence to withdrawal periods. This study was conducted to assess the regulatory roles and governance of antimicrobials, establish the pattern and extent of their use, evaluate the antimicrobial residues and resistance in the food animals and crop agriculture value chains, and relate these findings to existing strategies in place for combating the emergence of antimicrobial resistance in Tanzania. A multimethod approach (desk review, field study and interviews) was used. Relevant establishments were also visited. High levels of resistance to penicillin G, chloramphenicol, streptomycin and oxytetracycline have been reported, especially for Actinobacter pyogenes, Staphylococcus hyicus, Staphylococcus intermedius and Staphylococcus aureus from dairy cattle with mastitis and in humans. Similar trends were found in poultry where eggs and meat are contaminated with Escherichia coli strains resistant to amoxicillin + clavulanate, sulphamethoxazole and neomycin. An increasing trend of emerging multidrug resistant E. coli, Klebsiella pneumoniae, Staphylococcus aureus and Salmonella was also found in food animals. An increase in methicillin resistant Staphlococcus aureus (MRSA) and extended-spectrum beta-lactamase (ESBL) in the livestock sector in Tanzania have been reported. The pathogens isolated in animals were resistant to ampicillin, augmentin, gentamicin, co-trimoxazole, tetracycline, amoxicillin, streptomycin, nalidixic acid, azithromycin, chloramphenicol, tylosin, erythromycin, cefuroxime, norfloxacin and ciprofloxacin. An increased usage of antimicrobials for prophylaxis, and therapeutics against pathogens and for growth promotion in livestock, aquaculture and crop production were observed. A One Health strategic approach is advocated to combat antimicrobial resistance (AMR) in the food and agriculture sectors in Tanzania. Practical recommendations include (a) legislation review and implementation; (b) antimicrobial use (AMU), AMR and antimicrobial residue (AR) awareness and advocacy among stakeholders along the value chain; (c) strengthening of surveillance and monitoring programs for AMU, AMR and AR; (d) enhanced development and use of rapid and innovative diagnostic tests and the promotion of biosecurity principles; and (e) good husbandry practices. The utilization of this information to improve public health policies and reduce the burden of AMR will be beneficial.
Tanzania launched its first National Action Plan (NAP) on antimicrobial resistance (AMR) in 2017 to reduce the burden of AMR in the country and contribute to the global response. We aimed to analyze the implementation of the NAP on AMR in Tanzania using the governance framework. In-depth interviews were conducted with human and animal health practitioners and national-level policy actors. We adapted Chua’s AMR governance framework to analyze the development and implementation of the NAP in Tanzania. Implementation of the NAP has realized several achievements, including: (i) the establishment of a functioning Multi-Sectoral Coordinating Committee for coordinating the implementation of AMR activities; (ii) existence of governance structure; (iii) establishment of human and animal surveillance sites; (iv) creation of AMR awareness in the community and (v) availability of guidelines at the health facility level to ensure AMR stewardship. However, some dimensions of the governance areas, including reporting and feedback mechanisms, accountability, transparency and sustainability of AMR plans, are not effectively implemented. Addressing these challenges should involve strengthening the collaboration of the different sectors involved at different NAP implementation levels by careful planning and coordination, and provision of adequate resources to ensure sustainability.
Antimicrobials are used to support livestock health and productivity, but might pose a risk for the development of antimicrobial resistance; in particular, when multiple livestock species are raised together in production systems. On integrated chicken-fish farms, chickens are raised over fish ponds and poultry faeces is excreted into the ponds. We investigated antimicrobial usage and the antimicrobial susceptibility of Escherichia coli cultured from poultry faeces on 301 integrated farms in Ayeyarwady Delta of Myanmar. Antimicrobials were used by 92.4% of farmers for chickens, but they were not applied to fish. The most common antimicrobials used were Octamix (amoxicillin and colistin sulfate) on 28.4%, enrofloxacin on 21.0% and amoxicillin on 16% of farms. Overall, 83.1% (152/183) of the E. coli were resistant to at least one antimicrobial. The highest level of resistance was to amoxicillin (54.6%), tetracycline (39.9%), sulfamethoxazole/trimethoprim (35.5%) and enrofloxacin (34.4%). Multidrug resistance was identified in 42.4% of isolates. In general, we found similar levels of antimicrobial resistance in non-users of antimicrobials as in users of antimicrobials for more commonly applied antimicrobials. Overall, antimicrobial resistance was lower in chickens on these integrated farms in Myanmar, compared to poultry farms in other countries of South East and East Asia.
The current study was conducted to determine sulfonamides (SAs) and tetracyclines (TCs) residuals in farmed Nile Tilapia fish (Orechromis niloticus) using the solid phase extraction (SPE) technique and high performance liquid chromatography with diode array detection (HPLC-DAD). As well, to assess the potential health risk due to the consumption of contaminated fish following its household thermal processing. Tilapia samples were collected from four governorates in Egypt; El-Fayoum, Giza, Cairo, and Alexandria. The results showed that 56.3% (27 out of 48 samples) of fish samples were free of antibiotics, while 10.4% and 33.3% of samples were contaminated by SAs and TCs, respectively. Besides, oxytetracycline (OTC) showed the highest detected concentrations ranged from 52.8 to 658.5 (µg/kg), followed by chlortetracycline (OTC) (35.89– 109.76 µg/kg), and tetracycline (TC) (68.8 – 96.7- µg/kg). While the detected SAs were between 32.89 µg/kg (sulfamethazine: SMT) and 136.43 µg/kg (sulfadimethoxine: SDM). As well, sulfamethoxazole (SMX) showed an average concentration of 52.41 µg/kg. Notably, only 7 samples (out of 21 positive samples) had residual levels exceeded the permissible limits. The study also concluded that freezing fish at −18 °C for one week had no significant effect on the stability of SAs and TCs. As well, SAs showed more stability than TCs against the thermal processing for fish. Indeed, the stability of SAs and TCs antibiotics was arranged in a descending order, shown as follows: SMT > SDM > SMX > CTC > TC > OTC. Eventually, no potential risk to the Egyptian population was found from the consumption of the contaminated fish samples by SAs and TCs.
An adequate sampling methodology is the key to knowing the health status of aquatic populations. Usually, the aims of epidemiological surveys in aquaculture are to detect an infection and estimate the disease prevalence, and different formulas are used to calculate the sample size. The main objective of this study was to assess if the sample sizes calculated using classical epidemiological formulas are valid considering the sampling methodology, the population size, and the spatial distribution of diseased animals in the population (non-clustered or clustered). However, the use of sample sizes of 30, 60, and 150 fish is widely accepted in aquaculture, due to the requirements of the World Organization for Animal Health (OIE) for epidemiological surveillance. We have developed a specific software using ASP (Active Server Pages) language and MySQL database in order to generate aquatic populations from 100 to 10 000 brown trouts infected by Aeromonas salmonicida with different levels of prevalence: 2, 5, 10, and 50%. Then we implemented several Monte Carlo simulations to estimate empirically the sample sizes corresponding to the different scenarios. Furthermore, we compared these results with the values calculated by classical formulas. We determined that simple random sampling was more accurate in detecting an infection, because it is independent of the distribution of infected animals in the population. However, if diseased animals are non-clustered it is more efficient to use systematic methods, even in the case of small populations. Finally, the formula to calculate sample size to estimate disease prevalence is not valid when the expected prevalence is far from 50%, and it is necessary to increase the sample size to reach the desired precision.
The treatment of animals with antimicrobial products may lead to the contamination of edible tissues by their residues, which may represent a risk to human health. Therefore, this study aimed to determine the level of antimicrobial residues in food-producing animals (chicken, beef, and milk) in Lebanon. A total of 310 samples were collected and analysed using an LC-MS/MS for the determination of 48 compounds belonging to different families in order to map their compliance according to the European Commission decision 2002/657/EC. Results show that 60% of the analysed samples were not contaminated by any residue, while 12% presented a concentration higher than the MRLs for tetracyclines, sulphonamides, quinolones, and macrolides. Results revealed that chicken were the most contaminated by antimicrobial residues, when compared to beef and milk. The obtained results demonstrate the uncontrolled use of antimicrobials in some Lebanese farms and claim for better management of livestock.
Background:
The overuse of antimicrobials in food animals and the subsequent contamination of the environment have been associated with development and spread of antimicrobial resistance. This review presents information on antimicrobial use, resistance and status of surveillance systems in food animals and the environment in Africa.
Methods:
Information was searched through PubMed, Google Scholar, Web of Science, and African Journal Online databases. Full-length original research and review articles on antimicrobial use, prevalence of AMR from Africa covering a period from 2005 to 2018 were examined. The articles were scrutinized to extract information on the antimicrobial use, resistance and surveillance systems.
Results:
A total of 200 articles were recovered. Of these, 176 studies were included in the review while 24 articles were excluded because they were not relevant to antimicrobial use and/or resistance in food animals and the environment. The percentage of farms using antimicrobials in animal production ranged from 77.6% in Nigeria to 100% in Tanzania, Cameroon, Zambia, Ghana and Egypt. The most antibiotics used were tetracycline, aminoglycoside and penicillin groups. The percentage of multi drug resistant isolates ranged from 20% in Nigeria to 100% in South Africa, Zimbabwe and Tunisia. In the environment, percentage of multi drug resistant isolates ranged from 33.3% in South Africa to 100% in Algeria. None of the countries documented national antimicrobial use and resistance surveillance system in animals.
Conclusion:
There is high level of antimicrobial use, especially tetracycline, aminoglycoside and penicillin in animal production systems in Africa. This is likely to escalate the already high prevalence of antimicrobial resistance and multi drug resistance in the continent. This, coupled with weak antimicrobial resistance surveillance systems in the region is a great concern to the animals, environment and humans as well.
Food safety concerns have been raised over vegetables and herbs grown in aquaponics and hydroponics due to the reuse of wastewater and spent nutrient solutions. This study was conducted to determine the occurrence of foodborne pathogens in greenhouse-based aquaponic and hydroponic systems. Fish feces, recirculating water, roots, and the edible portions of lettuce, basil, and tomato were collected at harvest, and microbiological analyses were conducted for the bacterial pathogens Shiga toxin-producing Escherichia coli (STEC), Listeria monocytogenes, and Salmonella spp. Enrichments and selective media were used for the isolation, and presumptive positive colonies were confirmed by PCR. STEC was found in fish feces, in the water of both systems, and on the surface of the roots of lettuce, basil, and tomato regardless of the system. However, contaminated water did not lead to the internalization of STEC into the roots, leaves, and/or fruit of the plants. Meanwhile, L. monocytogenes and Salmonella spp. were not present in any samples examined. Our results demonstrated that there are potential food safety hazards for fresh produce grown in aquaponic and hydroponic production systems.
An observational cross-sectional study was carriedy out to investigate antibiotic residues in Clarias gariepinus and Oreochromis niloticus from the intensive rearing system in Southern Benin. The targeted antibiotic families were tetracyclins, amphenicols, beta-lactams and
macrolides. One hundred and forty-four (144) samples were used per antibiotic family for residue detection in the fish muscle, making 576 treated samples. The Charm II method based on radioimmunoassay was used. The results showed an overall residue prevalence of 11.1%, which is attributable to tetracyclines alone. There was no residue of the other antibiotic families in the treated fish muscles. The adult fish were the only contaminated age group with 22.2% residue prevalence compared to the fingerlings (p < 0.05). Likewise, the antibiotic esidues were significantly (p< 0.05) more prevalent in Clarias gariepinus (16.7%) than in Oreochromis niloticus (5.6%). The adult fishes are generally fattier than the young ones, and that can lower the fish body antibiotic elimination capability. This first detection of tetracyclines residues in fish produced in Benin shows the need to rule and control antibiotic use in the developing fish industry to preserve consumers’ health.
In Ghana there are concerns that antibiotics may be used inappropriately to boost fish production, though no study has investigated this problem. To provide preliminary insights into public health aspects of the problem, we investigated the occurrence of antibiotic residues and antibiotic-resistant bacteria in Nile tilapia (Oreochromis niloticus), a fish commonly cultivated and consumed in Ghana. Two hundred Nile Tilapia fish were randomly sampled from four major markets in Accra, the capital city of Ghana. One hundred samples were screened for antibiotic residues using a microbial inhibition plate test that detects sixteen different antibiotics commonly used in animal husbandry and aquaculture. The other 100 samples were cultured for bacteria using direct culture methods, and the isolates were tested against seven antibiotics by the Kirby Bauer method. The overall prevalence of antibiotic residues in the fish samples was 7%. Bacteria that were isolated from the fish samples were Shigella sonnei (10%), Enterobacter cloacae (7%), Escherichia coli (6%), Salmonella Typhi (3%), Klebsiella pneumoniae (2%), and Proteus mirabilis (2%). All bacteria isolated were susceptible to gentamicin and ciprofloxacin but resistant to ampicillin. Multi-drug resistance (ie resistance to three or more different classes of antibiotics) occurred in 86.7% of the isolates. Nile Tilapia sold in Accra is a source of multi-drug resistant bacteria. Consumption of the fish can also lead to significant exposure to antibiotic residues.
Information on the presence of antibiotics is sparse for all types of water in Africa, including groundwater, surface water, effluent of wastewater treatment plants (WWTPs) and municipal potable water. With the relatively high sales of different antibiotics to treat infectious diseases in the human population of Africa, the residual of the antibiotics is bound to be released through excretion via urine or fecal matter in parallel to the high sales. This article reviews the published analysis on the occurrence of antibiotics in the environment particularly in the aquatic environment in some countries in Africa. In general, sulfamethoxazole was the most commonly detected in Africa surface water (with eight reports from four countries) at a concentration range of 0.00027 – 39 μgL ⁻¹ . Wastewater analysis is believed to give an early warning for preventing epidemics. Thus, we discuss the associated level of antibiotic resistance to some prevalent diseases in Africa whose aetiological agents can develop antibiotic resistance due to exposure to antibiotic residue in water. This is important because of rising population of immuno-deficient African residents ravaged by HIV/AIDS, poor nutrition and less efficient sanitation systems.
The majority of seafood is farmed, with most finfish coming from freshwater ponds. Ponds are often fertilized to promote microbial productivity as a natural feed source to fish. To understand if pond fertilization with livestock manure induces a probiotic or prebiotic effect, we communally reared tilapia (Oreochromis shiranus), and North African catfish (Clarias gariepinus), for 4 weeks under seven manure treatments including layer chicken, broiler chicken, guinea fowl, quail, pig, cow, vs. commercial feed to evaluate microbial community dynamics of the manure, pond water, and fish feces using 16S and 18S rRNA marker genes along with metagenome sequencing. Catfish growth, but not tilapia, was positively associated with plankton abundance (p = 0.0006, R² = 0.4887) and greatest in ponds fertilized with quail manure (ANOVA, p < 0.05). Manure was unique and influenced the 16S microbiome in pond water, tilapia gut, and catfish gut and 18S community in pond water and catfish guts (PERMANOVA, p = 0.001). On average, 18.5%, 18.6%, and 45.3% of manure bacteria sOTUs, (sub‐operational taxonomic units), were present in the water column, catfish feces, and tilapia feces which comprised 3.7%, 12.8%, and 10.9% of the total microbial richness of the communities, respectively. Antibiotic resistance genes were highest in the manure and water samples followed by tilapia feces and lowest in catfish feces (p < 0.0001). In this study, we demonstrate how the bacterial and eukaryotic microbial composition of fish ponds are influenced by specific livestock manure inputs and that the gut microbiome of tilapia is more sensitive and responsive than catfish to these changes. We conclude that animal manure used as fertilizer induces a primarily prebiotic effect on the pond ecosystem rather than a direct probiotic effect on fish.
Background
Residues of antimicrobials in food have received much attention in recent years because of growing food safety and public health concerns. Their presence in food of animal origin constitutes socioeconomic challenges in international trade in animal and animal products. The major public health significances of antimicrobial residues include the development of antimicrobial drug resistance, hypersensitivity reaction, carcinogenicity, mutagenicity, teratogenicity, bone marrow depression, and disruption of normal intestinal flora. Indiscriminate use of antimicrobials in aquaculture resulting in occurrence of residues in aquaculture products and associated harmful health effects in humans requires control measures to ensure consumer protection.
Main body
This article focuses on factors contributing to the presence of antimicrobial residues in aquaculture products and their implications on consumers’ safety. Regulatory actions aimed at prudent use of veterinary drugs in food-producing animals with emphasis on aquaculture for safe and wholesome food production are also reviewed.
Conclusion
Prudent use of antibiotics in aquaculture under veterinary supervision is critical in ensuring safety of aquaculture products. Good animal husbandry practices as well as the use of alternatives to antibiotics such as vaccination, probiotics, phage therapy, and essential oils are recommended panaceas to reducing the use of antimicrobial residues in aquaculture and consequent food safety effects.
Antibiotic residue in meat is a serious public health concern due to its harmful effects on consumer health. This study aimed at estimating the residue levels of four commonly used antibiotics in meat samples using three analytical methods (ELISA, TLC and HPLC). A total of 150 samples of raw meat from sales points were analysed for ciprofloxacin, streptomycin, tetracycline, and sulphanilamide residues. Overall, ELISA analysis showed that 56, 34, 18, and 25.3% of the samples tested positive for ciprofloxacin, streptomycin, sulphanilamide and tetracycline residues respectively while TLC and HPLC detected 21.4, 29.4, 92.5, and 14.6%, and 8.3, 41.1, 88.8, and 14.6% of the samples as containing the residues, with ciprofloxacin and sulphanilamide having the lowest and highest occurrence, respectively. Furthermore, the concentrations of antibiotic residues were in the ranges of 19.8–92.8, 26.6–489.1, 14.2–1280.8, and 42.6–355.6 μg/kg with ELISA, while HPLC detected concentration ranges of 20.7–82.1, 41.8–320.8, 65.2–952.2 and 32.8–95.6 μg/kg for sulphanilamide, tetracycline, streptomycin, and ciprofloxacin, respectively. Mean ciprofloxacin and streptomycin residue levels were above the Codex/SA MRL recommended limit, while 3% of the samples contained multidrug residues. Although some of the mean residues levels were below the permissible limits, the co-occurrence of multidrug residues in some of the samples calls for concern.
Aim:
We investigated the prevalence of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae among wild fish from the coast of Bejaia (Algeria) in the Mediterranean Sea.
Results:
From March 2012 to August 2013, gut and gill samples of wild fish were screened for the presence of ESBL-producing Enterobacteriaceae. Strains were characterized with regard to antibiotic resistance, β-lactamase content, plasmid-mediated quinolone resistance, aminoglycoside resistance genes, and clonality (repetitive sequence-based polymerase chain reaction profiles and multilocus sequence typing). Virulence traits were performed for Escherichia coli and Klebsiella pneumoniae isolates. Of the 300 fish studied, 64 (21.3%) isolates were screened as positive for ESBL producing by the double-disc method. The isolates corresponded to E. coli, K. pneumoniae, Enterobacter cloacae, Morganella morganii, Citrobacter freundii, and Proteus vulgaris. A predominance of blaCTX-M gene was observed with a prevalence of 60.5% (n = 46). Furthermore, our study describes the association of important coresistance and virulence factors in E. coli and K. pneumoniae. Twelve of the ESBL producers carried genes of the qnr family and oqxAB gene and six carried the aac(6')-Ib-cr gene.
Conclusions:
Our results highlight for the first time the diffusion of multidrug-resistant Enterobacteriaceae isolates carrying resistance and virulence genes in fish from the Mediterranean Sea in Algeria.
Oxytetracycline is used to treat various diseases in cattle. However, its use may be associated with unacceptable residue levels in food. Oxytetracycline residues in tissues from indigenous cattle were determined in a cross-sectional study conducted in the Kilosa district, Tanzania, between November 2012 and April 2013. A total of 60 tissue samples, including muscle, liver and kidney, were collected from slaughterhouses and butchers and analysed for oxytetracycline using high-performance liquid chromatography. Oxytetracycline residues were found in 71.1% of the samples, of which 68.3% were above acceptable regulatory levels. The mean concentration of oxytetracycline across tissues was 3401.1 μg/kg ± 879.3 μg/kg; concentrations in muscle, liver and kidney were 2604.1 μg/kg ± 703.7 μg/kg, 3434.4 μg/kg ± 606.4 μg/kg and 3533.1 μg/kg ± 803.6 μg/kg, respectively. High levels of oxytetracycline residue in meat from indigenous cattle may pose a health threat to consumers in Kilosa. The findings possibly reflect a general lack of implementation of recommended withdrawal periods, ignorance about drug use and lack of extension services. Strict regulation of the use of antimicrobial drugs in the livestock industry and associated testing of animal-derived food sources prior to marketing are required.
The aim of the study was to screen for the presence of antimicrobial residues in poultry eggs from Bangladesh using the Charm II radio-receptor assay in the absence of expensive confirmatory instrumentation. This was based on cut-off values as set in the validation guidelines according to Commission Decision 2002/657/EC and Commission Implementing Regulation (EU) 2021/808. Fortified eggs spiked with fixed concentrations of doxycycline, erythromycin A, sulphamethazine, and benzylpenicillin were used to determine the cut-off values and detection capabilities (CCβ). Other validation parameters included were applicability, ruggedness, and robustness. A total of 201 egg mix samples from native organic chicken, duck, and commercial farm-raised laying hens (both brown and white eggs) were tested and after analysis 13%, 10%, and 4.5% of the egg mix samples showed positive signals for sulphonamides, macrolides/lincosamides, and tetracyclines, respectively. Presence of multiple drug residues were also suspected in 11 out of 201 egg mix samples.
Aquaculture is currently the fastest-growing food production sector, supplying half of the fish consumed by humans globally. Nevertheless, aquaculture has been indicated as a medium for production and gateway for the transfer of antibiotic resistance bacteria (ARB) and their corresponding antibiotic resistance genes (ARGs). However, the precise sources, factors responsible, types and consequences of ARB and ARGs in African aquaculture are currently not well known. This chapter fills such as a knowledge gap by discussing the sources of ARB and ARGs in African aquaculture, the possible factors contributing to their increase, the types of ARB and ARGs found in the industry and the socioeconomic consequences to humans. The chapter found that, African aquaculture represents a hotspot reservoir of ARB and ARGs. However, the ARB and ARGs in African aquaculture are complex and not solely derived from the industry. They originate from multiple sources, including antibiotics application in aquaculture, livestock manure and integrated aquaculture systems, agriculture and human health. The ARB and ARGs also originate from wastewater treatment plants, hospitals and pharmaceutical industries. The African aquaculture sector is currently dominated by multiple ARB and their genes, resistant to antibiotics commonly used to treat human diseases. The ARB and ARGs in aquaculture are caused by overuse and misuse of antibiotics in the sector, lack of regulations, ineffective enforcement, loose rules and inadequate surveillance and monitoring systems, which increase the availability and accessibility of antibiotics. Moreover, incorrect prescription, easy affordability and prolonged use of the same antibiotics also contribute to the increased ARB and ARGs in the African aquaculture industry. The ARB and ARGs existing in aquaculture are transferred to humans via aquaculture product contamination during handling and consumption of raw or undercooked food, horizontal and vertical gene transfers and direct contact with water or drinking contaminated water. The consequences of ARB and ARGs from aquaculture include increased infections, frequency of treatment failures, severe infections, prolonged duration of illness and increased frequency of bloodstream infections and hospitalisation. These make primary healthcare redundant for previously curable diseases, thereby increasing costs to society on treating cultured species and humans, leading to animal and human deaths. The information generated in the chapter calls for a “One Health” approach to combat ARB and ARGs while formulating stringent measures, legislations and regulations for antibiotics use in aquaculture, agriculture and sick patients to safeguard human health.
A structured questionnaire was administered to 151 purposively selected fish farmers to assess their practices and perceptions on antimicrobial usage (AMU) in fresh water fish farms in North-central Nigeria. Risk pathways for antimicrobial resistance (AMR) spread, risk status and drivers for misuse and overuse of antimicrobials were also assessed and residue presence in fish and pond water samples determined. Descriptive and analytic statistical analyses were performed at 95% confidence level. AMU risk status was assessed with Traffic Light model. Disc diffusion test was used to detect residues. All 151 recruited farmers participated but only 78.1% of them used antimicrobials in fish production. About 94% farmers practiced self-prescription of antimicrobials, and 94.9% did not observe withdrawal periods after AMU. AMR risk pathways were consumption (p=0.010), contacts (p=0.004), and environment (p=0.002). Socio-cultural drivers of antimicrobial misuse, overuse and resistance emergence in fish farms were inappropriate AMU (p=0.002), poor biosecurity (p=0.001), poor sanitation (p=0.001), poor economic status of farmers (p=0.002), and intensive management system (p=0.001). Majority (73.5%) of farms were in Class 3 (Red risk) status. Residues were detected in fish and water samples from 44.4% of the farms. The study revealed poor practices and perceptions on AMU. AMU stewardship should be promoted through farmers’ education. To achieve food safety, food security, public and environmental health, socio-cultural drivers for misuse and overuse in farms should be mitigated through surveillance and control programmes using the concept of ‘One Health’ approach.
Residual antibacterial agents in 5909 animal and fishery products in Tokyo, Japan, were investigated over 17 consecutive years (2003–2019). Monitoring of 32 antibacterial agents (lincosamides, macrolides, penicillins, quinorones and tetracyclines) per product was accomplished via two steps: screening (by microbiological methods) and confirmation (by instrumental methods). Microbiological screening methods identified presumptive groups and determined semi-quantitative values. The instrumental methods quantified 81 residues of 11 different antibacterial agents in 72 samples. The screening strategy based on microbiological methods demonstrated the following: (i) the majority of the samples (over 99%) met Japanese regulations, (ii) using multiple methods provided a reliable inspection system with accurate quantitative values and (iii) there was a constant presence of tetracyclines and unexpected residues (lincomycin and norfloxacin) in various products. Thus, this long-term monitoring and screening strategy provided evidence that the frequencies and trends of residual antibacterial agents not only enhance food safety but also help to prevent antimicrobial resistance.
Antibiotics are widely used in aquaculture. Intensive farming drives indiscriminate use of antibiotics, which results in residues of antibiotics in cultured aquatic products and bacterial resistance. This perspective attempts to present a brief update on usage, regulations, residues and potential human health risk of antibiotics used in aquaculture. Through the comprehensive literature review, we provide a view that the safety of aquatic products still requires further attention and more rigorous risk assessment. Finally, we make a few suggestions for future research directions: reduce the use of antibiotics to bring down the speed of resistance development, and monitor resistant pathogen and genes; strictly manage the environmental sanitation of aquaculture and pay attention to the quality of water bodies introduced into aquaculture; seek international cooperation to establish an information bank of antibiotic residues and antibiotic resistant genes, and set up a quantitative model to assess the risk of antibiotic resistance associated with the antibiotic residues.
Antibiotics are used abusively in humans and agriculture, including aquaculture, making them omnipresent in the environment, posing health risks to aquatic animals and humans. However, how antibiotics affect the anatomy and physiology of fish, including the presence of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in fish in Africa are currently poorly understood. This chapter synthesized the available literature on the potential risks of antibiotics on cultured fish and human health from Africa. The limited available studies indicate that few antibiotics improve fish growth but do not affect their survival rate. Antibiotics application on fish cause body malformation and damage, which induce hepatotoxicity, nephrotoxicity, leukocytosis, hematopoiesis, and lymphocytosis, suggesting sustained toxic effects. Antibiotics use in fish and other foods like shrimps and vegetables together with antibiotics residues in the aquatic environment have led to an increase in the prevalence of ARB and ARGs, posing a human health risk in various African countries. Limited studies indicate higher residues of antibiotics in cultured fish, which exceed the maximum limits set by the Codex Alimentarius Commission and the World Health Organization. Thus, policies and mechanisms for limiting the use of antibiotics in food animals to protect human health in Africa are urgently needed.
This review focuses on the current status of antibiotics use, effects on animal health and the environment, existing policies and regulatory mechanisms in the top 15 producing countries. Fifty papers were reviewed and represented the bulk of literature worldwide. We observed that 67 antibiotic compounds were used in 11 of the 15 countries between 2008 and 2018. Among these countries, 73% applied oxytetracycline, sulphadiazine and florfenicol. On average, countries used 15 antibiotics and the top users included Vietnam (39), China (33) and Bangladesh (21). On environmental and health risks, the review revealed sufficient evidence that directly links antibiotics use to food safety, occupational health hazards and antimicrobial resistance. Environmental risks included residue accumulation, aquatic biodiversity toxicity, microbial community selection for antibiotic resistance and the emergence of multi‐antibacterial resistant strains. Regarding policies, major players were the European Commission, the Food and Drug Administration, European Medicines Agency, Norwegian Veterinary Institute, the Norwegian Food Safety Authority, Codex and government ministries. In particular, the Norwegian Food Safety Authority and Norwegian Veterinary Institute demonstrated the most outstanding regulation mechanisms of antibiotics use in aquaculture that needs to be emulated. The future of aquaculture lies in guaranteeing the supply of safe aquatic products to the growing consumer market. Thus, international coordination of the policy and regulatory environment is needed, while increased investment in research for alternative aquatic health management strategies is essential. Future technologies should focus on the reduction of antibiotics use to safeguard the environment and ensure safety of consumers, feed industry and aquaculture workers.
The practice of antimicrobial usage in African catfish (Clarias gariepenius) production and the presence of antimicrobial residue in catfish in Oyo State were investigated by cross sectional study. Twenty commercial fish farmers were interviewed using interviewers administered semi-structured questionnaire on the pattern of antibiotic usage, knowledge of occurrence and risks of antimicrobial residues in catfish produced for public consumption. In addition, 165 samples of Clarias gariepenius were obtained from ready to eat fish restaurants and farms for screening for antimicrobial residues using Premi®Test kit while oxytetracycline residue was determined by high performance liquid chromatography (HPLC). The results showed that majority (95%) of the respondents frequently administered drugs (in feed and water) to their fish without veterinary prescription and not observing withdrawal period. Oxytetracycline is the commonly used, extra-label drug usage were frequently practiced. Ninety eight (61.3%) liver and 84 (52.5%) muscle of catfish screened contained detectable antimicrobial residues, while 62 (38.8%) liver and 48 (30.0%) muscle had oxytetracycline residue by HPLC method. Oxytetracycline concentrations in the positive samples ranged between 234.3 and 987.5 µg kg 1 (mean = 875.32±45µg kg) in the liver and 22.5 and 553.2 µg kg (mean = 257.2±133µg kg) in the fillets. Forty 1 1 1 three (26.9%) liver and 30 (18.8%) fillets contained oxytetracycline residues above the Codex Alimentarius Commission established maximum residue limit of 600 and 200 µg kg respectively. This implied that 1 appreciable quantity of catfish consumed in Ibadan, Nigeria posed antibiotic residue risks and food safety consequences. Misuse of antibiotics in aquaculture production without veterinary prescription and control coupled with lack of awareness of the food safety consequences were the contributing factors for the high level of residue violation. Therefore, there is need for veterinary supervision of drug use in fish, residue monitoring and food safety education of producers and consumers.
This study was carried out to assess the level of heavy metals (lead (Pb) and cadmium (Cd)) and antibiotics (tetracycline and chloramphenicol) residues in frozen and fresh fish types obtained from Eleyele river, Officer's mess, Alfa farm and a major frozen meat outlet in Ibadan, Oyo State Nigeria. The Atomic Absorption Spectrophotometer (AAS) and High Performance Liquid Chromatography (HPLC) were used to analyze the heavy metals and antibiotics residue levels in fresh and frozen fish, respectively. The results showed mean concentrations of antibiotics was higher (p<0.05) in fresh than in frozen fish samples while there were no significant differences in the mean concentrations of heavy metal residue. The differences of mean residue levels in both antibiotics and heavy metals tested in the cranial and caudal parts of the fish samples were not significant (p<0.05). However, there was a significant difference between species (tilapia and catfish) and sources. The highest heavy metals and tetraxycline residues were observed in Alfa's farm (Pb: 0.039+/-0.004 ppm; Cd: 0.020+/-0.006 ppm; tetraxycline: 2.185+/-0.412). Chloramphenicol was highest in Officers mess (0.837+/-0.165 ppm). The heavy metals (Pb and Cd) concentrations determined were below the maximum permissible limits set by both local and international safety agencies. Tetraxcycline exceeded international limits of 0.2 ppm while Chloramphenicol which has a zero tolerance level was also detected from all sources. This study accentuates the need for control of heavy metals and antibiotics in fish sold for human consumption in Ibadan, Nigeria. The need to ban chloramphenicol in treatment of fish and other animals is emphasised.
Antibiotic residues (sulfonamides and tetracyclines) were determined in Gilthead sea bream (Sparus aurata) and feed samples by means of immunoassays and LC-MS-MS (liquid chromatography-mass spectrometry2). A preliminary study to know the withdrawal time of oxytetracycline in Gilthead sea bream samples was also conducted. It was carried out using immunoassays based on photometric detection of horseradish peroxidase (HRP) activity and time-resolved fluorometric detection of coproporphyrin of Platinum (II) (ELISA and TR-FIA, respectively). The results were compared to those obtained using an LC-MS-MS methodology. They showed that approximately 37 days would be the withdrawal time in order not to exceed the MRL and fish could be commercialized with safety.Regarding feed samples analysis, an LC-MS-MS method was optimized including sample treatment. Average recoveries (n = 6) ranging from 78 to 108% were obtained and precision of the method was between 0.2 and 3%. The same sample treatment was applied to the feed immunoanalysis obtaining satisfactory results.Finally, 20 fish and 4 feed samples were analysed in order to confirm the feasibility of the immunoassays for detecting antibiotic residues. Sulfonamide residues were not detected in any fish sample. Tetracycline residues were detected in some fish samples from marine farms, with total concentrations between 2.1 and 152 ng g−1. In all cases, the obtained results correlated well with those achieved by LC-MS-MS. Therefore, the new methodology allows for food safety of the medicated fish.
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