Biodegradation strategies of veterinary medicines in the environment: Enzymatic degradation

One Health closely integrates healthy farming, human medicine, and environmental ecology. Due to the ecotoxicity and risk of transmission of drug resistance, veterinary medicines (VMs) are regarded as emerging environmental pollutants. To reduce or mitigate the environmental risk of VMs, developing friendly, safe, and effective removal technologies is an important means of environmental remediation for VMs. Many previous studies have proved that biodegradation has significant advantages in removing VMs, and biodegradation based on enzyme catalysis presents higher operability and specificity. This review focused on biodegradation strategies of environmental pollutants and reviewed the enzymatic degradation of VMs including antimicrobial drugs, insecticides, and disinfectants. We reviewed the sources and catalytic mechanisms of peroxidase, laccase, and organophosphorus hydrolases, and summarized the latest research status of immobilization methods and bioengineering techniques in improving the performance of degrading enzymes. The mechanism of enzymatic degradation for VMs was elucidated in the current research. Suggestions and prospects for researching and developing enzymatic degradation of VMs were also put forward. This review will offer new ideas for the biodegradation of VMs and have a guide significance for the risk mitigation and detoxification of VMs in the environment.

Expiry of veterinary medicines in supply outlets in Central Uganda: prevalence, management and associated factors

BACKGROUND

Animal diseases are a danger to livestock, businesses, and public health. This is why the public and private sectors in Africa have invested immensely in the manufacture and distribution of veterinary drugs. However, veterinary drug supply chain actors still suffer losses as a result of expiration. Besides, the way expired products are managed might pose risks to human, animal, and environmental health. This study investigated the prevalence, management of, and factors associated with the expiry of veterinary medicines in supply outlets in Central Uganda.

METHODS

A cross-sectional study was conducted among owners and caretakers of veterinary drug supply outlets. Data were collected using self-administered, semi-structured questionnaires. The level of expiry was computed as "acceptable" (for levels reported as ≤ 5%) and "unacceptable" (for levels reported as ˃5%). Logistic regression was used to assess associations between the level of drug expiry and predictor variables.

RESULTS

A total of 168 owners/caretakers of veterinary drug supply outlets were included in this study. The majority (148/168, 88.1%) of respondents reported having experienced expiries in their outlets. Unacceptable levels of expiry were reported in 38/168 (22.6%) of the outlets. Retail outlets accounted for the majority (34/38, 89.5%) of the unacceptable levels. Powdered drugs accounted for most expiries (106/148, 71.6%). Most expiries were for drugs supplied to outlets on credit (58/124, 46.8%) and those used to treat rare diseases (26/124, 21%). Major reasons for expiry included irrational prescription, inaccurate forecasts, overstocking, dry seasons, and stocking without considering stock-at-hand. Methods of disposal of expired drugs included throwing at pits (74/168, 44.1%); returning drugs to suppliers (51/168, 30.4%); and incineration (33/168, 19.6%). Factors associated with acceptable levels of expiry included the caretaker being female [adjusted OR = 2.9, 95% CI = 1.22-5.08]; having a procurement policy [adjusted OR = 3.9, 95% CI = 1.29-4.81] and practicing first expiry, first out [adjusted OR = 6.07, 95% CI = 4.71-8.70].

CONCLUSIONS

Veterinary drug expiries are common in Uganda, and environmentally unfriendly methods of disposal are widely used. Acquisition and use of inventory tracking technologies that support First-Expiry-First-Out principles as well as proper disposal of expired medicines are recommended.

Post marketing surveillance of selected veterinary medicines in Tanzania mainland

BACKGROUND

Veterinary medicines have been widely used for the prevention and treatment of animal diseases. Globally, the veterinary medicine industry is growing. However, there is a significant increase of concern on the quality of veterinary medicines in various developing countries' legal markets. Poor-quality medicines are associated with treatment failure, development of drug resistance, increased healthcare cost, and death. These reasons warrant a need for monitoring the quality of the medicines circulating in the Tanzania Mainland.

METHODS

This was a survey study and veterinary medicines samples were collected from 9 out of 26 regions of Tanzania mainland between 2014 and 2017. Veterinary medicines were sampled from wholesale pharmacies, retail pharmacies, veterinary clinics and Veterinary Accredited Drug Dispensing Outlets (ADDO-vet). All sampled medicines were subjected to product information review and full quality control testing at the Tanzania Medicines and Medical Devices Authority-World Health Organization prequalified laboratory.

RESULTS

A total of 238 samples of veterinary medicines were collected. Out of these, 97.1% (231/238) were subjected to full quality control testing and product information review. All sampled veterinary medicines conformed to visual appearance, clarity, pH, solubility and sterility tests. Also, of the sampled veterinary medicines 97.8% (226/231) and 89.2% (206/231) passed identification and assay tests, respectively. As well as, the majority of the collected samples 92% (219/238) failed to comply with product information requirements. The most observed deficiencies on product information were inadequate information on the package insert 94.1% (224/238), inappropriate storage conditions 55.5% (132/238) and lack of Tanzania registration number 27% (64/238).

CONCLUSION

Veterinary medicines with poor quality were found circulating in the legal markets of Tanzania. This can potentiate treatment failure and the development of drug resistance in animals and humans. Post marketing surveillance program will continue to be implemented to ensure that only good quality, safe and efficacious medicines are circulating in the Tanzania Mainland market.

The effect of anaerobic pig slurry redox potentials on the degradation of veterinary medicines

Veterinary medicines are frequently used within intensive livestock husbandry and there has been a growing interest regarding their fate in the environment. However, research has seldom assessed the influence of pig slurry properties on the fate of veterinary medicines even though such an understanding is essential for a more robust environmental risk assessment. Changes within manure degradation rates have the potential to alter the concentration of antibiotics applied to land, and the outcome of the risk assessment. The aim of this work was to investigate whether commonly reported redox potentials affect the degradation rates of acetyl-salicylic acid, ceftiofur, florfenicol, oxytetracycline, sulfamethoxazole, and tylosin. The employed redox potentials were -100 mV (reduced), -250 mV (anaerobic) and -400 mV (very anaerobic). A compound specific relationship was observed where the degradation of ceftiofur, florfenicol, oxytetracycline and sulfamethoxazole was inhibited under reduced conditions over that of very anaerobic; the respective DT50 values were 0.7-1.84 h, 1.35-3.61 h, 22.2-49.8 h, 131-211 h and 35.4-94 h. In contrast, tylosin was found to degrade faster at reduced conditions over very anaerobic (DT50 6.88-19.4 h). The presented research demonstrates the importance of redox potential on degradation rates and suggests we need stringent and harmonized redox control to improve the environmental risk assessment of veterinary medicines. Environmental relevance and significance: Given the significant effect of anaerobic redox potentials on veterinary medicine fate tighter regulation is required in manure degradation trials.

Assessing the mobility of veterinary drugs with column experiments using different soils and under controlled flow conditions

Veterinary pharmaceuticals are pollutants that received much attention during the last 20 years. Macrocyclic lactones are a class of drugs globally used in animal and human health, as well as crops protection. Some of its members are key substances for global food security. In this research, the mobility of eprinomectin (EPM) in soil columns (25 cm soil height; 10 cm diameter) was assessed for the first time. Soil density in the columns was 1.1-1.2 g/cm³. Porosity was 0.54-0.60. Three different soil types were used (agricultural, pastoral, wetland). In the experiment, chloride was used as a non-reactive tracer to determine the hydrodynamic conditions in the columns. Therefore, water velocity (v) was 0.146-0.151 cm/h, dispersion coefficient (D) 0.011-0.017 cm²/h and dispersivity (D/v) was 0.072-0.121. Our results showed that the drug remained in the top layers of the columns, after applying an extreme irrigation scenario. The retardation factor for EPM was 43.4-54.5 while for chloride was 0.99-1. EPM fraction (% of applied mass) in 0-1 cm was 13.8-18.0% and in 1-5 cm was 53.3-73.0%. An amount 13-29% was irreversibly bound or degraded during this experiment. From a soil management perspective, the continuous application of EPM contaminated manure, could result in high concentrations in the top 10 cm of the soil profile. Soil column experiments, where hydrodynamic conditions are well defined, are useful for the environmental impact assessment of veterinary pharmaceuticals.

Ecotoxicological effects of fipronil, neem cake and neem extract in edaphic organisms from tropical soil

Veterinary medicines are widely applied for the treatment and prevention of animal diseases. Consequently, animal manure contains significant amounts of environmental pollutants that are potential sources of environmental pollution when inappropriately applied in soils. This work aimed to evaluate ecotoxicological effects of doses of commercial fipronil, neem cake and neem extract in the survival and reproduction of earthworms (Eisenia andrei), enchytraeidae (Enchytraeus crypticus) and springtails (Folsomia candida) in Oxisol and tropical artificial soil (TAS). Applications of fipronil, neem cake and extract in soil were carried out according to standardized ISO methodologies by using a random experimental design with five replicates. Toxic effects of fipronil for springtails in Oxisol and TAS were observed with LC₅₀ of 0.26 mg kg^-1 (0.18-0.35 mg kg^-1) and 0.29 mg kg^-1 (0.22-0.37 mg kg^-1), respectively. It was not observed significant toxic effects of fipronil for earthworms and enchytraeidae in both soils. However, significant amounts of juvenile earthworm and adult enchytraeidae decreased in fipronil doses higher than 10 mg kg^-1. Neem cake and extract were not toxic for earthworms and enchytraeidae but, significant amounts of juvenile springtails decreased in neem cake doses from 500 to 1000 mg kg^-1. It can be concluded that the use of veterinary medicines containing synthetic compounds for preventing diseases in animals needs to be controlled to avoid environmental pollution after applying manure in soil. Veterinary medicines containing natural compounds as neem cake and extract are eco-friendly and could be efficiently applied in soil in a sustainable way.

Sorption and desorption of 17α-trenbolone and trendione on five soils

The metabolites 17α-trenbolone and 17α-estradiol are principal metabolites in cattle excreta following the administration of Synovex^® ONE, which contains trenbolone acetate and estradiol benzoate. As part of the environmental assessment of the use of Synovex ONE, data were generated to characterize the fate of 17α-trenbolone, and its metabolite trendione in the environment. Predictions of the fate and environmental concentrations of these hormones after land application require accurate estimates of the sorption of these compounds in soils. The sorption and desorption of 17α-trenbolone and trendione were measured at 5 nominal concentrations in 5 soils from different geologic settings using a batch equilibrium technique following guideline 106 of the Organisation for Economic Co-operation and Development. Both the sorption and desorption of 17α-trenbolone and trendione to soils were adequately described by the Freundlich sorption model and by linear partition coefficients. The mean sorption coefficients were 9.04 mL/g and 32.2 mL/g for 17α-trenbolone and trendione, respectively. The corresponding mean Freundlich sorption exponents were 0.88 and 0.98, respectively. Sorption of 17α-trenbolone and trendione was correlated principally with soil organic carbon. Average sorption coefficients normalized to soil organic carbon content (K_OC ) were 460 mL/g and 1804 mL/g for 17α-trenbolone and trendione, respectively. The mean desorption coefficients were 22.1 mL/g and 43.8 mL/g for 17α-trenbolone and trendione, respectively. Calculated hysteresis coefficients based on the difference in the area between sorption and desorption isotherms indicated that sorption equilibrium was not fully reversible and hysteresis of desorption isotherms occurred for both 17α-trenbolone and trendione. Environ Toxicol Chem 2017;36:613-620. © 2016 SETAC.

National monitoring study in Denmark finds increased and critical levels of copper and zinc in arable soils fertilized with pig slurry

The increasing consumption of copper and zinc in modern farming is linked to their documented benefit as growth promoting agents and usefulness for controlling diarrhoea. Copper and zinc are inert and non-degradable in the slurry and the environment and thereby introducing new challenges and concern. Therefore, a follow-up to pervious national soil monitoring programs on heavy metals was initiated in 2014 with special focus on the historical trends in soil concentrations of copper and zinc in Danish arable soils. Hereby it is possible to analyse trends for a 28 year period. Data shows that: 1) Amendment of soils with pig slurry has led to a significant increase in soil concentrations of copper and zinc, especially in the latest monitoring period from 1998 to 2014; 2) Predicted no-effect concentrations for soil dwelling species published by the European Union is exceeded for zinc in 45% of all soil samples, with the highest proportion on sandy soils; 3) The current use of zinc and copper in pig production may lead to leaching of metals, especially zinc, from fields fertilized with pig slurry in concentrations that may pose a risk to aquatic species.

Occurrence and transformation of veterinary pharmaceuticals and biocides in manure: a literature review

The spread of veterinary medicinal products (VMPs) and biocides via manure onto agriculturally used areas represents a very important emission into the environment for these product groups. Within this literature study, publicly available transformation studies with liquid manure are summarized. Transformation studies were evaluated regarding the transformation fate of tested substances, the origin and characteristics of used manure, the experimental setup, and the measured parameters. As main topics within the 42 evaluated transformation studies, the high dependency of transformation on temperature, redox potential, dry matter content, and other parameters is reported. Test duration throughout the studies ranged from 2 to 374 days and study temperature ranged from 5 to 55 °C. Only seven publications gave information on the redox potential of the manure. Further, the characterization of the matrix in many cases was inadequate due to missing parameters such as dry matter content or pH. Only three publications studied transformation of biocides. To allow for a consistent assessment of studies within the registration process, a harmonized internationally accepted and validated test method is needed. Additionally, monitoring data of VMPs in manure were collected from literature and evaluated regarding the origin and characteristics of the manure, the minimum/maximum found concentrations, and the percentage of identified compounds. Within the 27 evaluated publications, 1568 manure samples were analyzed and 39 different active substances for VMPs and 11 metabolites and transformation products of VMPs could be found in manure. Most often, the samples were analyzed for sulfonamides, tetracyclines, and fluoroquinolones. Not one study searched for biocides or worked with a non-target approach. For sulfadiazine and chlortetracycline, concentrations exceeding the predicted environmental concentrations were found.

Probabilistic risk assessment of veterinary medicines applied to four major aquaculture species produced in Asia

Aquaculture production constitutes one of the main sources of pollution with veterinary medicines into the environment. About 90% of the global aquaculture production is produced in Asia and the potential environmental risks associated with the use of veterinary medicines in Asian aquaculture have not yet been properly evaluated. In this study we performed a probabilistic risk assessment for eight different aquaculture production scenarios in Asia by combining up-to-date information on the use of veterinary medicines and aquaculture production characteristics. The ERA-AQUA model was used to perform mass balances of veterinary medicinal treatments applied to aquaculture ponds and to characterize risks for primary producers, invertebrates, and fish potentially exposed to chemical residues through aquaculture effluents. The mass balance calculations showed that, on average, about 25% of the applied drug mass to aquaculture ponds is released into the environment, although this percentage varies with the chemical's properties, the mode of application, the cultured species density, and the water exchange rates in the aquaculture pond scenario. In general, the highest potential environmental risks were calculated for parasitic treatments, followed by disinfection and antibiotic treatments. Pangasius catfish production in Vietnam, followed by shrimp production in China, constitute possible hot-spots for environmental pollution due to the intensity of the aquaculture production and considerable discharge of toxic chemical residues into surrounding aquatic ecosystems. A risk-based ranking of compounds is provided for each of the evaluated scenarios, which offers crucial information for conducting further chemical and biological field and laboratory monitoring research. In addition, we discuss general knowledge gaps and research priorities for performing refined risk assessments of aquaculture medicines in the near future.