Sheep dip chemicals and water pollution

Choice test to determine potential attractants and repellents for the sheep scab mite, Psoroptes ovis (Acari: Psoroptidae)

A choice test bioassay was devised to screen compounds as potential semiochemicals (e.g., kairomones or allomones that mediate aggregation, attraction or repellence) for the obligate parasitic mite, Psoroptes ovis. The choice test used filter paper discs in a 1:4 test:control ratio and was found to be a reliable, effective and efficient method. Four mammalian lipid components were assessed as potential attractants-linoleic acid, arachidonic acid, methyl myristate and squalene-, and the insect/tick repellent DEET for potential repellence. Linoleic acid was significantly attractive to P. ovis adult females and has the potential to act as an attractant. Identification of P. ovis semiochemicals, especially attractants, would be beneficial in the development of novel control methods and tools for this species. This is essential considering the increase in resistance to the limited prophylactic chemical treatments in the UK, and the high prevalence of scab infections.

Improving environmental risk assessment of human pharmaceuticals

This paper presents 10 recommendations for improving the European Medicines Agency's guidance for environmental risk assessment of human pharmaceutical products. The recommendations are based on up-to-date, available science in combination with experiences from other chemical frameworks such as the REACH-legislation for industrial chemicals. The recommendations concern: expanding the scope of the current guideline; requirements to assess the risk for development of antibiotic resistance; jointly performed assessments; refinement of the test proposal; mixture toxicity assessments on active pharmaceutical ingredients with similar modes of action; use of all available ecotoxicity studies; mandatory reviews; increased transparency; inclusion of emission data from production; and a risk management option. We believe that implementation of our recommendations would strengthen the protection of the environment and be beneficial to society. Legislation and guidance documents need to be updated at regular intervals in order to incorporate new knowledge from the scientific community. This is particularly important for regulatory documents concerning pharmaceuticals in the environment since this is a research field that has been growing substantially in the last decades.

Biodegradation of cypermethrin by a novel Catellibacterium sp. strain CC-5 isolated from contaminated soil

The bacterial strain CC-5, isolated from contaminated soil and identified as Catellibacterium sp. based on morphology and partial 16S rDNA gene sequence analysis, utilized cypermethrin as its sole carbon source and degraded 97% of 100 mg·L(-1) cypermethrin within 7 days. The optimal degradation conditions were determined to be 30 °C and pH 7.0. Degradation was found to follow a first-order model at initial cypermethrin concentrations below 400 mg·L(-1). Strain CC-5 suffered substrate inhibition at high cypermethrin concentrations, and the biodegradation kinetics were successfully described by the Haldane model, with a maximal specific degradation rate of 1.36 day(-1), an inhibition constant of 164.61 mg·L(-1), and a half-saturation constant of 101.12 mg·L(-1). Inoculating cypermethrin-treated soil samples with strain CC-5 resulted in a higher rate of cypermethrin removal than that in noninoculated soil, regardless of whether the soil had previously been sterilized. These results reveal that the bacterial strain may possess potential to be used in bioremediation of pyrethroid-contaminated environment.

Potential environmental consequences of administration of ectoparasiticides to sheep

Sheep ectoparasiticides, which include the synthetic pyrethroids, the organophosphates, the 'insect'-growth regulators, the formamidines and the spinocyns, enter into the environment primarily through disposal of dip or fleece scours, as well as with contaminated faeces and urine. Due to the large quantities of spent dip, risks associated with environmental contamination are high. Synthetic pyrethroids and organophosphates pose risks to dung, soil and aquatic fauna; concerns over potential ecotoxicity to vertebrates and invertebrates have resulted in the cessation of their use in many countries. There is very little information regarding the ecotoxicity of 'insect'-growth regulators, formamidines or spinocyns, with no studies focussing on sheep. Here, the impact of sheep ectoparasiticides is discussed in terms of their potential to enter into the environment, their toxicity and their impact on ecosystem functioning. Where there are no data for excretion or toxicity of the ectoparasiticides used in sheep production, examples to demonstrate potential impacts are taken from laboratory ecotoxicity tests and the cattle literature, as well on work with foliar insecticides. Future research priorities are suggested to allow assessment of the environmental consequences of sheep ectoparasiticide treatments, which are essential for future sustainable sheep production.

Effects of salinity, DOM and metals on the fate and microbial toxicology of propetamphos formulations in river and estuarine sediment

Toxicity studies tend to use pure pesticides with single organisms. However, natural systems are complex and biological communities diverse. The organophosphate pesticide propetamphos (PPT) has been found exceeding regulatory limits (100 ng L(-1)) in rivers. We address whether solution properties affect the fate of Analar (Analar-PPT) or industrial PPT (PPT-Ind) propetamphos formulations and whether propetamphos and metal toxicant effects are additive, antagonistic or synergistic? The sorption, desorption, biodegradation and microbial toxicology of Analar-PPT and PPT-Ind were investigated in Conwy River and estuary sediment. Results showed elevated salinity enhanced PPT sorption, while higher salinities increased PPT-Ind retention. Higher dissolved organic matter (DOM) and low salinity slowed Analar-PPT biodegradation (1.9×10(-3)h(-1)). Analar-PPT and PPT-Ind biodegradation was further reduced by low salinity, high DOM and dissolved Zn and Pb (6.3×10(-4)h(-1), 1100 ht(½) for Analar-PPT; 7.5×10(-4)h(-1), 924 ht(½) for PPT-Ind). Toxicity effects of PPT, Zn and Pb in equitoxic ratio were higher for PPT-Ind (4.7 μg PPT-Ind g(-1); 581 μg Zn g(-1); 395 μg Pb g(-1)) than for Analar-PPT (34.6 μg PPT g(-1); 312 μg Zn g(-1); 212 μg Pb g(-1)) whilst a toxicant ratio 1:100:10 suggested small quantities of Analar-PPT (EC(10)=0.06 μg g(-1)) affected microbial communities. The combined toxicity effect was more than additive. Thus, industrial formulations and pollutant mixtures should be considered when assessing environmental toxicity.

Effect of propetamphos on the male rats reproductive system

The present study aimed at defining the testicular toxicity of propetamphos. Mature male albino rats (5-6 months old) were treated with propetamphos orally at doses of 0, 0.18, 0.38, 0.75, 1.5 and 3mg/kg/day for 60 consecutive days. Propetamphos at a dose of 0.38 mg/kg/day significantly reduced the sperm motility only. At 0.75 mg/kg/day sperm count, sperm motility, plasma testosterone level and activity of sorbiol dehydrogenase (SDH) were significantly reduced and sperm morphological abnormalities were significantly increased. At 1.5mg/kg/day weight of testes, seminal vesicle and epididymis were reduced dose dependently whereas, at 3mg/kg/day, weight of prostate gland and activities of acid phosphatase (ACP) and glucose-6-P-dehydrogenase (G6PDH) were decreased significantly. On histopathological examination indicated toxicity of propetamphos on testes depending on dose and observed at doses higher than 0.38 mg/kg/day. These results indicate testicular toxicity of propetamphos at dose of 0.38 mg/kg/day or higher in male albino rats.

Sheep blowfly strike risk and management in Great Britain: a survey of current practice

The methods used for the control of sheep blowfly strike (ovine cutaneous myiasis) and the farm management factors associated with strike prevalence were examined using data from questionnaire survey returns provided by 966 sheep farmers in Great Britain, based on the period between March 2003 and February 2004. Overall, 91% of participants treated prophylactically with insecticides against blowfly strike; 39% treated twice and 11% treated more than three times in the year. Insect growth regulators (IGRs) were the most commonly chosen product (40%), especially the IGR cyromazine. Only 12% of farmers opted to dip their sheep in organophosphate insecticide against fly strike and 2% of farmers reported applying inappropriate products against strike to their sheep, such as ivermectin or 'drenches'. Farmers worming their ewes more often were 0.8 times less likely to report blowfly strike, but those who wormed their lambs more often were 1.2 times more likely to report strike. Pure-breed flocks were 0.7 times less likely to record an outbreak of blowfly strike than cross-breed flocks. Strike was less likely in ewe flocks grazed at higher altitude; however, this relationship with altitude was not seen in lambs. The results show that insecticides remain the primary tool used by almost all farmers to prevent strike and that the type of insecticides used and means of application have altered dramatically over the past 15 years. However, the prevalence of strike has remained almost unchanged over this period. Clearly careful attention to the type and timing of insecticide application, in association with a detailed understanding of the husbandry factors that predispose sheep to higher strike risk, is essential to allow the optimal management of strike problems.

The impact of synthetic pyrethroid and organophosphate sheep dip formulations on microbial activity in soil

Sheep dip formulations containing organophosphates (OPs) or synthetic pyrethroids (SPs) have been widely used in UK, and their spreading onto land has been identified as the most practical disposal method. In this study, the impact of two sheep dip formulations on the microbial activity of a soil was investigated over a 35-d incubation. Microbial utilisation of [1-(14)C] glucose, uptake of (14)C-activity into the microbial biomass and microbial numbers (CFUs g(-1) soil) were investigated. In control soils and soils amended with 0.01% sheep dip, after 7d a larger proportion of added glucose was allocated to microbial biomass rather than respired to CO(2). No clear temporal trends were found in soils amended with 0.1% and 1% sheep dips. Both sheep dip formulations at 0.1% and 1% concentrations resulted in a significant increase in CFUs g(-1) soil and [1-(14)C] glucose mineralisation rates, as well as a decline in microbial uptake of [1-(14)C] glucose, compared to control and 0.01% SP- or OP-amended soils. This study suggests that the growth, activity, physiological status and/or structure of soil microbial community may be affected by sheep dips.

Toxicology and fate of Pestanal and commercial propetamphos formulations in river and estuarine sediment

To quantify the impact of organophosphate pesticides on aquatic ecosystems requires a mechanistic understanding of their behaviour in a range of environmental matrices. The objective of this study was to compare the sorption/desorption, biodegradation and toxic effects of the Pestanal grade and commercial formulation (Ectomort Centenary) of the organophosphate insecticide propetamphos in river and estuarine sediments. For both formulations, the sorption of propetamphos onto sediment was initially very rapid followed by a slower sorption phase. Similarly, the initial rate of desorption was rapid, followed by a much slower rate. In both sorption and desorption experiments, the level of sorbed propetamphos was considerably higher for the commercial formulation of propetamphos (Kd=7-11) than for the Pestanal grade (Kd=4-10). The rate of propetamphos biodegradation was sediment dependent but was most rapid where microbial activity and nutrients were the highest and sorption was the lowest. Propetamphos was more rapidly degraded in sediments under aerobic (t(1/2)=15 d) compared to anaerobic conditions (t(1/2)=19 d). However, no significant difference in the biodegradation rates of the Pestanal grade and commercial formulations of propetamphos were observed. The toxic effect of propetamphos on sediment microbial communities was significantly greater for the commercial formulation than for the Pestanal grade of propetamphos based on EC50 (21 versus 236 microg g(-1)) and EC10 values (0.3 versus 54 microg g(-1)). In conclusion, our results highlight the importance of using commercial pesticide formulations when carrying out ecotoxicological testing.

Mineral and carbon usage of two synthetic pyrethroid degrading bacterial isolates

AIMS

To investigate the biodegrading ability and cometabolism of synthetic pyrethroid (SP) utilizing bacteria in cultures with various minerals and carbon sources.

METHODS AND RESULTS

Previously isolated SP-degrading Pseudomonas sp. and Serratia sp. were used in cultures containing either flumethrin SP or cypermethrin SP formulations. The culture media consisted of either (i) water only, (ii) water and sucrose, (iii) mineral broth or (iv) mineral broth and sucrose. The growth of both organisms was greatest in the mineral broth and sucrose medium, but the growth-limiting factor for Pseudomonas sp. strain Circle was the mineral content whereas for Serratia sp. strain White it was the carbon substrate.

CONCLUSION

The greatest extent of degradation of both SP-based compounds occurred with Pseudomonas sp. strain Circle but was dependant on the medium.

SIGNIFICANCE AND IMPACT OF THE STUDY

This investigation could lead to the development of a relatively inexpensive medium supplement to enhance the microbial biodegradation of undesirable compounds, either in situ or ex situ. In this particular case, for the biodegradation of SPs used in sheep dip.

Determination of solid-liquid partition coefficients (K(d)) for diazinon, propetamphos and cis-permethrin: implications for sheep dip disposal

Two groups of chemicals are currently licensed for use in sheep dip products in the UK. These are organophosphate (OP) insecticides and synthetic pyrethroid (SP) insecticides. SPs are deemed to be less toxic to human health than OPs, although they are approximately 100 times more toxic to some elements of the aquatic environment. Three insecticides were selected for experimental investigation: diazinon, propetamphos (OPs) and cis-permethrin (SP), representative of the active ingredients used in sheep dip formulations, with additional uses in insect control in crops, and for domestic control of flies, mosquitoes, cockroaches, lice, ticks and spiders. The UK Government has recently reviewed agricultural practices relating to the disposal of used sheep dip, because the constituent insecticides are frequently detected in UK watercourses and the presence of these compounds is a severe hazard to the aquatic environment. Standard batch sorption experiments were carried out to investigate insecticide partitioning from water to soil, and the relationship between sorption and soil organic carbon content is discussed. Sorption isotherms and K(d) values showed that cis-permethrin adsorption was fastest on all five soils investigated, exhibiting the greatest total partitioning to the soil phase (83.8-94.8%) and high resistance to desorption. In comparison, the OP insecticides exhibited moderately strong soil adsorption as evidenced by their K(d) coefficients (diazinon K(d) 12-35 and propetamphos K(d) 9-60), with low sorption reversibility (< 15%). Calculation of a hydrological retardation factor in a scenario representative of a typical UK environment suggested that SP insecticides such as cis-permethrin will not migrate in the soil profile due to their virtual immobility and strong soil retention, and thus waste sheep dip disposal to agricultural land should not pose a risk to aquatic life if applied with appropriate controls.

A simple pump-assisted method for collecting live, undamaged Psoroptes ovis from sheep using circulating saline

The availability of large numbers of undamaged sheep scab mites, Psoroptes ovis, would be beneficial for discovery screening and development trials. There are several reported procedures for removing scab mites from sheep but they have limitations. To overcome this, a simple but versatile method employing the use of pumped saline was developed to remove all stages of the P. ovis mite from sheep. The method takes no more than 2 min to remove mites from the selected site with relative ease and is not affected by the condition of the fleece or lesion. The number of mites removed with the new method was 5-10 times more than detected by visual examination. These mites were undamaged and survived off-host for up to 16 days. The robust, portable equipment is easy to use under field conditions, making this method suitable for use as a diagnostic tool for early detection and monitoring of scab mites thus providing opportunities for development of novel alternative control strategies.

Biodegradation of the synthetic pyrethroid cypermethrin in used sheep dip

AIMS

To investigate the breakdown of cypermethrin synthetic pyrethroid (SP) insecticide-based used sheep dip (USD), with its indigenous microbial community and two previously isolated SP-degrading microorganisms.

METHODS AND RESULTS

Cultures of USD (50 ml) containing 250 ml l(-1) cypermethrin were inoculated with the SP-degrading organisms and incubated at 25 degrees C with agitation at 80 rev min(-1) for 14 days. The viable cell counts and concentration of cypermethrin were monitored. A non-stimulated control was also carried out. The previously isolated bacteria were the most effective at degrading cypermethrin, leaving approximately two-thirds the concentration of SP as was found in the control. The non-stimulated cultures showed negligible breakdown of SP over the experimental period.

CONCLUSIONS

The previously isolated SP-degrading bacteria could have a use in the treatment of SP USD.

SIGNIFICANCE AND IMPACT OF STUDY

In situ treatment of SP-based USDs to detoxify the active ingredient before disposal could be very useful in helping to deal with agricultural pesticide waste. Such an approach, or by ex situ treatment would be more preferable to current methods, such as those of incineration and disposal to land.

Isolation and identification of synthetic pyrethroid-degrading bacteria

AIMS

To isolate, select, identify and assess the potential for the biodegradation of synthetic pyrethroids (SPs) in sheep dips.

METHODS AND RESULTS

SP-degrading bacteria were isolated from a mixed soil sample consisting of garden soil and soils from farms where SPs had been used. The two largest in size were then identified using microscopy, biochemical and genetic techniques to be members of the genera Pseudomonas and Serratia. By comparing the 16S rRNA gene sequences, the Pseudomonas sp. discovered was shown to group within the Pseudomonas fluorescens intrageneric cluster. The Serratia isolated was closely related to Serratia plymuthica. Cell growth and degradation was greatest in the Pseudomonas sp. culture where there was breakdown of 60 mg l(-1) to 6 mg l(-1) technical cypermethrin in 20 days. Tolerance to the SPs was greater in the Pseudomonas sp. but was found to depend on the availability of other carbon sources and nutrients.

CONCLUSIONS

The bacteria characterized show the potential to be used in a bioremediation application for the treatment of SP residues.

SIGNIFICANCE AND IMPACT OF THE STUDY

The SP-degrading bacteria may have use in the disposal of used SP residues and with further research could lead to an alternative route of disposal for use in agriculture or industry.

A review of water quality concerns in livestock farming areas

Post-war changes in farming systems and especially the move from mixed arable-livestock farming towards greater specialisation, together with the general intensification of food production have had adverse affects on the environment. Livestock systems have largely become separated into pasture-based (cattle and sheep) and indoor systems (pigs and poultry). This paper reviews water quality issues in livestock farming areas of the UK. The increased losses of nutrients, farm effluents (particularly livestock wastes), pesticides such as sheep-dipping chemicals, bacterial and protozoan contamination of soil and water are some of the main concerns regarding water quality degradation. There has been a general uncoupling of nutrient cycles, and problems relating to nutrient loss are either short-term direct losses or long-term, related to accumulated nutrient surpluses. Results from several field studies indicate that a rational use of manure and mineral fertilisers can help reduce the pollution problems arising from livestock farming practices. Several best management practices are suggested for the control of nutrient loss and minimising release of pathogen and sheep-dip chemicals into agricultural runoff.