Control Of Parasites In Sheep Research Articles

Evaluation of the supply of Duddingtonia flagrans for the control of gastrointestinal parasites in sheep.

Parasitic resistance imposes alternative control methods, like nematophagous fungi. In this study, two experiments were conducted supplying Duddingtonia flagrans aiming to evaluate the biological control of parasites in sheep. In the first, 24 sheep naturally infected by gastrointestinal nematodes were allocated, in randomized blocks, following the treatments: control or treated group, 0.5g/animal product containing D. flagrans, chlamydospores. Weight, body score, Famacha©, egg count per gram of feces (EPG), and larval percentage were evaluated. In the second experiment, D. flagrans (0.25 and 0.5g product) was infested with manure, plus or not protein concentrate, in a completely randomized design. In both experiments the dose was intentionally lower than recommended. Recovery and larval identification were performed. The SAS analyzed the variables by the MIXED procedure, repeated measures in time. Weight, body score, hematocrit, and Famacha© did not show differences between treatments (p>0.05); however, EPG (p<0.001) and the percentage of larvae identified in coproculture were different. In the second experiment, the inclusion of the fungus did not influence the recovery of larvae (p>0.05). In both experiments, colonization and advancement of the fungus were visualized. Under the experimental conditions, the fungus D. flagrans was not effective in the biological control of parasitic infection in sheep.

Moxidectin use in Scottish sheep flocks suggests a need for clearer product labelling and communication of updated SCOPS guidelines.

Guidelines for sustainable use of moxidectin were established in 2020. This study aimed to identify how Scottish sheep farmers are using this key endectocide and estimate its effectiveness against gastrointestinal nematodes. Questionnaires were distributed to sheep farmers across Scotland, and analysis focused on moxidectin use in relation to Sustainable Control of Parasites in Sheep (SCOPS) guidelines. Farmers using moxidectin in their flock volunteered to submit post-treatment sheep faecal samples, which were analysed for the presence of gastrointestinal nematodes using faecal egg counts with polymerase chain reaction to determine species. Despite 70% of farmers using moxidectin in 2020, knowledge levels varied: 24% of farmers included other anthelmintics when asked about moxidectin use. Moxidectin was used for a wide variety of reasons, and most farmers did not consistently follow SCOPS guidelines. Despite only 2 of 76 farmers reporting failure of moxidectin treatment, gastrointestinal nematodes were found following moxidectin treatment on five out of six farms tested and included Teladorsagia circumcincta, Cooperia curticei, Haemonchus contortus and Nematodirus sp. Findings from this project indicate the need for improved anthelmintic product labelling and farmer support to encourage sustainable use. The presence of nematodes in treated animals is suggestive of anthelmintic resistance.

Disease surveillance in England and Wales, June 2022.

Disease surveillance in England and Wales, June 2022.

Determining the influence of socio-psychological factors on the adoption of individual ‘best practice’ parasite control behaviours from Scottish sheep farmers.

Since 2003, the Sustainable Control Of Parasites in Sheep (SCOPS) group have provided the UK sheep farming industry with guidance on ways to mitigate the development and dissemination of anthelmintic resistance (AR). However our empirical understanding of sheep farmers’ influences towards such ‘best practice’ parasite control approaches is limited, and therefore requires further assessment and evaluation to identify the potential factors influencing their implementation. In 2015, a telephone questionnaire was conducted in order to elicit Scottish sheep farmers’ attitudes and behaviours regarding the SCOPS recommended practices, as well as gauging farmers’ general attitudes to gastrointestinal nematodes (GIN; term roundworm used in questionnaire) control. A quantitative structural equation modelling (SEM) approach was employed to determine the influences of socio-psychological factors and the uptake of individual anthelmintic resistance mitigating practices including: the implementation of a quarantine strategy for parasite control and the use of parasite diagnostic testing for monitoring faecal egg counts (FEC) and detecting AR. The proposed models established a good fit with the observed data and explained 61%, 54% and 27% of the variance in the adoption of AR testing, FEC monitoring, and quarantine behaviours respectively. The results presented highlight a number of consistent and distinct factors significantly influencing the implementation of selected SCOPS recommended practices. The negative influences of topography and farmer experience was frequently demonstrated in relation to multiple GIN control practices, as well as the positive influences of social norms, worm control knowledge, AR risk perception and positive attitudes to the services provided by the veterinary profession. Factors that were shown to have the greatest relative effects on individual parasite control practices included: the perceived expectation of others (i.e. Social norms) for implementing a quarantine strategy, farmer’s suspicions to the presence of AR on the holding for instigating AR testing and the confirmation of AR for adopting FEC monitoring. Determining the influences of behaviour-specific factors on farmers’ decision making processes will help to identify and address positive and negative influences concerning implementation of AR mitigating practices, as well as contribute to the development of more evidence based intervention strategies in the future.

Prevalence of sheep lice and trends in control practices across Australia - Australian sheep parasite control surveys from 2003 to 2019.

The sheep body louse (Bovicola ovis) is a parasite of major economic concern in Australia. This article reports lice incidence and control practices on Australian sheep farms as determined by three cross-sectional surveys of the years 2003, 2011 and 2018. The incidence of live lice detected within a flock was similar across the survey years with a slight decline in 2018 (2003: 20%, 2011: 18.6% and 2018: 13.9%). In an average year, most farmers did not see any direct or indirect evidence of lice infestation (2011: 59.3% and 2018: 69.5%), however, over a five-year period 38.9% (2003), 66.3% (in 2011) and 55.8% (in 2018) reported seeing evidence of lice infestation at least once with significant variation between sheep producing regions in 2011. In an average year, nearly three quarters of respondents treated for lice (2011:73.5% and 2018: 73.3%) with the majority treating immediately following shearing and very few treating sheep with long wool. Even higher percentages treated for lice at least once in the preceding five-year period (2011: 86.2% and 2018: 87.5%). Backliner was the most popular method of chemical application for lice control in sheep off-shears or with short wool (2003: 77%, 2011: 73% and 2018: 74.3%). For long wool treatments, hand jetting declined in popularity from 2003 (64%) to 2011 (54%) and 2018 (8.6%) as backliners became more popular (2003: 36%, 2011: 51% and 2018: 60%). The use of benzoylphenyl urea insect growth regulators (IGR) for off-shears/short wool treatment declined from 2003 (92.8%) to 2011 (51%) and 2018 (2.9%) and were largely replaced by neonicotinoids and spinosad for backliner/spray-on products. The use of organophosphates declined for plunge dipping (2003: 83.8%, 2011: 83% and 2018: 7.7%). Spinosad use for plunge dipping off-shears/short wool increased over the survey years (2003, 0%, 2011: 9% and 2018:46.2%). The use of IGRs declined for backliner application on long wool and were mainly replaced by spinosad in 2011 and 2018. Fewer respondents reported suspected resistance to lice control products in 2018 (8%) compared with 2003 (26%) and 2011 (13%) with most reporting suspected resistance to IGR and synthetic pyrethroids and emerging suspicions of resistance to neonicotinoids in 2018. Resistance to lice control products also reduced in importance as a reason for recurring lice infestations between 2011 (ranked 2nd) and 2018 (ranked 6th). Biosecurity was important to sheep producers with the highest ranked reason for recurring lice infestations being from stray or purchased sheep.

Australian surveys on parasite control in sheep between 2003 and 2019 reveal marked regional variation and increasing utilisation of online resources and on-farm biosecurity practices.

Australian Wool Innovation Limited (AWI) commissioned three cross-sectional surveys of sheep producers' sheep parasite control practices over a 15-year period from 2003 to 2018. The aims were to document current sheep parasite incidence and control practices, to measure change in sheep parasite control practices over time and to inform extension messages for sheep industry advisors and sheep farmers. The surveys were conducted in 2004, 2012 and 2019 measuring sheep parasite control practices in the years 2003, 2011 and 2018. The surveys focused on incidence and control of the three major sheep parasite groups; gastrointestinal nematodes, blowflies and lice. The 2003 and 2011 surveys were paper-based and the 2018 survey was accessed via a link to an online survey. This article is the first in a series of four presenting the results of the three surveys and will cover methods, demographics, production systems and general parasite management. Response rates to the surveys declined each year from the peak response rate in 2003 (n = 1365 in 2003; n = 575 in 2011 and n = 354 in 2018). Mean reported rainfall was significantly lower in 2018 (407 mm) than in 2003 (611 mm) and 2011 (650 mm). The demographics of the respondents and their production systems were largely similar between the three surveys for respondent age, median property size, income from wool and sheep meat, proportion of the property area cropped, median sheep dry sheep equivalent (DSEs), ewes as a proportion of the total flock and median cattle DSEs. Month of weaning was more likely to be in summer months for summer dominant rainfall areas and spring for intermediate and winter dominant rainfall areas. There was a marked increase in the proportion of respondents asking for an animal health history when introducing sheep to their flock from 2011 (9%) to 2018 (65%). Similarly, a greater proportion of respondents isolated introduced sheep for at least 2 weeks in 2018 (82%) compared with 2011 (19%). However, there was a decrease in the use of a quarantine lice treatment for introduced sheep from 2011 (50%) to 2018 (21%). Farmers rated themselves, other farmers or member of their staff as most important sources of information on parasite control in both 2011 and 2018. There was a significant increase in the proportion of respondents visiting the ParaBoss suite of websites from 2011 to 2018 confirming their growing importance for information delivery and decision support.

Biological Control of Gastrointestinal Helminthes of Livestock

Gastrointestinal helminths cause considerable production loss in ruminants globally and constraint to optimum livestock production. Extensively managed animals often host gastrointestinal parasites. Guidelines for sustainable control of parasites in sheep (SCOPS) have been produced in the UK which include recommendations for treatments to ewes. Traditionally control has been achieved through the application of broad spectrum anthelmintic; however, resistance is the major issue. In terms of parasitic nematodes in sheep, widespread resistance has been identified to the three available broad-spectrum anthelmintic classes with reports of increasing multi-class resistance was reported. Anthelmintic treatments can reach up to eight for lamb finishing. Resistance to anthelmintic can be reached to 88%. The trend towards nonchemical parasite control methods (ecological, organic, green) farming of livestock. Biological control of nematode parasites of livestock is the rising issue of animal science. In this study, biological control of nematode parasites of livestock has been reviewed.

129 Evaluation of the effect of Bedoukian compound X administered twice on gastrointestinal nematode infection in sheep

Abstract Gastrointestinal nematodes (GIN) and coccidia have a large financial and health impact on small ruminants. Recent years have seen an increase in anthelminthic/ coccidiostat resistance, and there is a need to develop alternative control methods. The objective of this study was to examine the effect of a unique proprietary compound used in the fragrance/flavor industry with an insect repellant application (Compound X; Bedoukian Research) on parasite control in sheep. Previous research by our laboratories showed a short term reduction in fecal egg count (FEC) in sheep orally drenched with the product. In the current study, naturally infected (GIN and coccidia) Katahdin lambs were orally drenched with 15 mL of Compound X and 15 mL mineral oil (CMX; n = 11) or 30 mL mineral oil (CON; n = 9) on d 0 and 21; FEC/fecal oocyst count (FOC) were determined every 7 d for 8 wk, and feces were cultured to examine GIN larvae. Data were analyzed using a mixed model with repeated measures over time, and regression (SAS). The FEC were reduced in CMX compared with CON between d 0 and 21 (P &lt; 0.03, both mixed model and regression), d 21 and 42 (P &lt; 0.001, mixed and regression), and d 0 and 56 (P &lt; 0.001); FEC were influenced by day of study (P &lt; 0.04), and the interaction tended to be significant using regression (P &lt; 0.10). The FOC were negligible and not analyzed. There was no effect on development of nematode larvae in feces. However, there was a shift in population distribution from Haemonchus contortus to Trichostrongylus spp. which indicated a possible effect on female H. contortus fecundity. There was a sign of toxicity in one lamb following the second CMX drench. The value of using such a compound for GIN control may warrant further investigation.

Strategic planning for parasite control on livestock farms

There are several approaches to the control of parasites in sheep and cattle, ranging from therapeutic, when actions are only taken when clinical disease is observed, to strategic, when steps are taken to anticipate and mitigate the risk of disease and production losses. Strategic programmes generally result in high levels of animal welfare through the avoidance of clinical disease and superior animal performance by reducing exposure to pathogens. Implementation of strategic actions requires forward planning and may not be straightforward in some systems, for example, all-year-round calving dairy herds. The main tools for strategic control are pasture management, nutrition, vaccination and medication; general principles and examples are provided in this article.

Resistance delaying strategies on UK sheep farms: A cost benefit analysis

UK guidelines for the sustainable control of parasites in sheep (SCOPS) were formulated with the primary aim of delaying development of anthelmintic resistance (AR) on UK sheep farms. Promoting their use requires the engagement and commitment of stakeholders. An important driver for behavioural change in sheep farmers is evidence of economic benefits. A recent evaluation of SCOPS guidance in practice demonstrated a significant reduction in anthelmintic use, suggesting economic benefits through a direct reduction in product and labour costs. However, in order to maintain production, a range of alternative control strategies are advised, resulting in additional costs to farmers and so a full cost benefit analysis of best practice management was undertaken. We allocated financial values to the management recommendations described in the SCOPS technical manual. Benefits were calculated using data for production variables and anthelmintic use measured during studies to evaluate the effect of SCOPS recommendations on 16 UK sheep farms and from other published work. As SCOPS control is not prescriptive and a range of different diagnostics are available, best and worst case scenarios were presented, comparing the cheapest methods (e.g. egg counts without larval culture) and management situations (e.g closed flocks not requiring quarantine treatments) with the most laborious and expensive. Simulations were run for farms with a small, medium or large flock (300; 1000; 1900 ewes) as well as comparing scenarios with and without potential production benefits from using effective wormers. Analysis demonstrated a moderate cost for all farms under both scenarios when production benefits were not included. A cost benefit was demonstrated for medium and large farms when production benefits were included and the benefit could be perceived as significant in the case of the large farms for the best case scenario (>£5000 per annum). Despite a significant potential reduction in anthelmintic use by farmers employing SCOPS guidance, the very low price of the older anthelmintic classes meant that the benefit did not always outweigh the additional management/diagnostic costs unless an increase in production was also achieved. This is an important finding. Focussing research on key innovations that will improve the cost effectiveness of diagnostic assays in a diagnostic driven control strategy, as well as designing treatment options that can improve production outcomes, and presenting them in a clear and transparent way, must be high priority goals. Coupling targeted research with improvements in the delivery of messages to the end user is important in the light of increasing global concerns over drug resistance.

A quantitative analysis of attitudes and behaviours concerning sustainable parasite control practices from Scottish sheep farmers

Nematode control in sheep, by strategic use of anthelmintics, is threatened by the emergence of roundworms populations that are resistant to one or more of the currently available drugs. In response to growing concerns of Anthelmintic Resistance (AR) development in UK sheep flocks, the Sustainable Control of Parasites in Sheep (SCOPS) initiative was set up in 2003 in order to promote practical guidelines for producers and advisors. To facilitate the uptake of ‘best practice’ approaches to nematode management, a comprehensive understanding of the various factors influencing sheep farmers’ adoption of the SCOPS principles is required.A telephone survey of 400 Scottish sheep farmers was conducted to elicit attitudes regarding roundworm control, AR and ‘best practice’ recommendations. A quantitative statistical analysis approach using structural equation modelling was chosen to test the relationships between both observed and latent variables relating to general roundworm control beliefs. A model framework was developed to test the influence of socio-psychological factors on the uptake of sustainable (SCOPS) and known unsustainable (AR selective) roundworm control practices. The analysis identified eleven factors with significant influences on the adoption of SCOPS recommended practices and AR selective practices. Two models established a good fit with the observed data with each model explaining 54% and 47% of the variance in SCOPS and AR selective behaviours, respectively. The key influences toward the adoption of best practice parasite management, as well as demonstrating negative influences on employing AR selective practices were farmer’s base line understanding about roundworm control and confirmation about lack of anthelmintic efficacy in a flock. The findings suggest that improving farmers’ acceptance and uptake of diagnostic testing and improving underlying knowledge and awareness about nematode control may influence adoption of best practice behaviour.

The development of anthelmintic resistance with best practice control of nematodes on commercial sheep farms in the UK

Antimicrobial resistance threatens the effective prevention and treatment of an ever-increasing range of infections. The widespread development of anthelmintic resistance is a major global issue affecting the effective control of parasite diseases in grazing livestock production. Sustainable control strategies that reduce dependence on antimicrobials have the potential to slow the further development of resistance but there is little data on the effect of control strategies on resistance development in the field. This report documents a study undertaken to measure the temporal effect of the UK sustainable control of parasites in sheep (SCOPS) guidelines on the development of anthelmintic resistance. Farms carrying out SCOPS or traditional worm control (TRADITIONAL) were tested for resistance to the benzimidazole and imidazothiazole anthelmintics in vitro using a discriminating dose (dd) larval development test (LDT) in year 1 and then 7 years later. In years 5 and 7, resistance was also measured using a dose-response LDT assay. There was a significant increase in Teladorsagia survivors at the benzimidazole dd assay between year 1 and year 7 for both treatment groups, but the increase in survivors was greater for the farms carrying out their traditional worm control compared to the SCOPS farms. There was also a significant difference between benzimidazole dd results generated across years for Trichostrongylus, but the year and treatment interaction was not significant. Only one of the farm Teladorsagia populations had survivors in the imidazothiazole dd assay in years 1 and 7 and none of the Trichostrongylus populations survived in year 1 compared to isolates from three of the farms in year 7. Dose-response data showed a significant effect for time for both the benzimidazole and imidazothiazole anthelmintics and the increase was again significantly higher for the Teladorsagia populations in the TRADITIONAL group compared to the SCOPS group. This data suggests an increased sensitivity both to detect and to measure changes in response to anthelmintics with the dose-response assay compared to the dd and this is important particularly when allele frequencies are low as might be the case when novel compounds are released to the market. Anthelmintic use across years 5–7 was significantly lower for the farms in the SCOPS group compared to the TRADITIONAL group and farmers in the SCOPS group had selected products from the benzimidazole group less often than farmers in the TRADITIONAL group. Both groups had made minimal use of the imidazothiazole anthelmintic classes and the majority of ewe treatments were selected from the macrocyclic lactone class. Further research is required to determine the effect of these anthelmintic choices on the development of resistance to the macrocyclic lactones.

Three-year evaluation of best practice guidelines for nematode control on commercial sheep farms in the UK

Anthelmintics are commonly used on the majority of UK commercial sheep farms to reduce major economic losses associated with parasitic diseases. With increasing anthelmintic resistance worldwide, several countries have produced evidence-based, best practice guidelines with an example being the UK’s Sustainable Control of Parasites in Sheep (SCOPS) initiative. In 2012, a pilot study demonstrated that SCOPS-managed farms used fewer anthelmintic treatments than traditionally managed farms, with no impact on lamb productivity and worm burden. Building on these results, we collected data for three consecutive years (2012–2014) with the following aims: (1) To compare the effects of traditional and SCOPS-based parasite management on lamb productivity and worm burden; (2) To evaluate the effect of region and farm type on lamb productivity and worm burden; (3) To compare the frequency and patterns of use of anthelmintic treatment on traditional and SCOPS-managed farms. The study was carried out on 16 farms located in the North east and the South west of England and Wales. Lamb productivity was assessed by quantifying birth, mid-season and finish weights and calculating daily live-weight gains and time to finish in a cohort of 40–50 lambs on each farm. Five annual faecal egg counts were carried out on each farm to assess worm burden. No differences in lamb productivity and worm burdens were found between farms that adopted SCOPS guidelines and traditional farms across the three years. However, mean infection levels increased for both the SCOPS and the traditional groups. Lamb production was not significantly different for farm type and region but the effect of region on infection was significant. For both ewes and lambs, SCOPS farms carried out significantly fewer anthelmintic treatments per year, and used fewer anthelmintic doses/animal than traditional farms. The data suggest a trend to increasing use of anthelmintics in ewes on traditional but not on the SCOPS farms and a decreasing use of anthelmintics in lambs on both SCOPS and traditional farms. Across time, an increasing number of SCOPS farmers left their ewes and lambs untreated and the reverse was true for traditional farmers. Overall, farms implementing SCOPS guidelines used less anthelmintic treatments and less frequently than traditionally managed farms, without loss of animal performance or increased worm burden. Implementing SCOPS guidelines might have economic benefits for farmers, help reduce development of anthelmintic resistance on farms and decrease any environmental impact of anthelmintics. Furthermore, these data suggest some important epidemiological trends that should be investigated in long-term studies.

Ovicidal and larvicidal activity of extracts of Opuntia ficus-indica against gastrointestinal nematodes of naturally infected sheep

This study describes the in vitro anthelmintic activity of extracts from Opuntia ficus indica against gastrointestinal nematodes of sheep. The anthelmintic activity was evaluated by inhibition of egg hatching, larval development and larval migration assays. The residual aqueous fractions from cladodes and fruits showed higher ovicidal activity with EC50 values of 7.2mg/mL and 1.5mg/mL, respectively. The aqueous, hexane, and ethyl acetate fractions from fruits and the aqueous fraction from cladodes inhibited 100% of larval development at the lowest concentration tested (1.56mg/mL). The crude cladode and fruit ethanolic extracts inhibited larval migration and showed EC50 values of 0.74mg/mL and 0.27mg/mL, respectively. Phytochemical screening detected high concentrations of alkaloids, tannins, flavonoids, and saponins in the fruits and cladodes. The results demonstrated that O. ficus exhibits anthelmintic activity in vitro, suggesting that, beyond its nutritional potential, this plant can also be an ally for parasite control in sheep.

Evaluation of ‘best practice’ (SCOPS) guidelines for nematode control on commercial sheep farms in England and Wales

Parasitic diseases are a major constraint to optimum livestock production and are the major cause of economic loss in UK sheep flocks, with farmers remaining dependant on anthelmintics for control. In the UK, research and evidence based, “best practice” guidelines for sustainable control of parasites in sheep (SCOPS) were first produced in 2004 and have been regularly updated since. This study was designed to evaluate the effect of these best practice guidelines for worm control on lamb production and infection levels, compared with more traditional management. Sixteen farms were selected based on a 2 cube factorial design with 3 factors known to affect worm epidemiology: control regimen; farm type; and climatic region. A formalised plan for worm control using 7 potential resistance-delaying practices was prepared for each of the 8 best practice (SCOPS) farms, in conjunction with the farms veterinarians. The 8 farms in the traditional management group (CONTROL farms) were selected based on ongoing evidence of them using worm control strategies deemed to be “higher-risk”. A cohort of 40–50 study lambs at each farm was monitored from birth to finishing, allowing evaluation of lamb productivity, worm infection levels and for comparison of numbers of anthelmintic treatments. Birth and mid-season weights were used to calculate daily live-weight gain. Birth and finish dates were used to calculate time to finish and finish weights were also compared. Faecal egg counts, larval culture and species differentiation were undertaken throughout the year to assess the impact of the control strategies on worm burdens. There was no significant difference in results for any of the 3 production responses when comparing predicted means accounting for the differences in birth weight. In fact SCOPS farms had, on average, a higher daily weight gain and finish weight than CONTROL farms when comparing observed means. Statistical analysis of infection levels clearly showed no significant effect according to farm type (p=0.71) or treatment (p=0.81). In contrast the effect of region (p=0.08), although not significant, had a much larger effect size (standardised mean difference) with lower parasite burdens based on faecal egg counts on Northern farms compared to Southern farms. For both ewes and lambs, significantly fewer treatments were carried out on the SCOPS farms. The data collected from this study suggests that farms implementing SCOPS principles use less anthelmintic than other farms, without loss of animal performance or increased worm burden.

Anthelmintic resistance in Northern Ireland (III): Uptake of ‘SCOPS’ (Sustainable Control of Parasites in Sheep) recommendations by sheep farmers

Reports of anthelmintic resistance to multiple drugs in individual parasite species, and in multiple parasite species across virtually all livestock hosts, are increasingly common. A working group of UK researchers and practitioners devised a set of guidelines in 2003 (Sustainable Control of Parasites in Sheep, ‘SCOPS’) aimed at maintaining anthelmintic efficacy on farms. Over the years that followed, these guidelines were promoted through meetings, promotional literature and the agricultural press. Results from questionnaires conducted in Northern Ireland (NI) in 2005 (covering 1999–2004) and 2011 (covering 2008–2011) have provided an opportunity to examine the extent to which these campaigns have influenced parasite control on sheep farms.The percentage of flocks at risk of under-dosing through inaccurate weight estimation in NI has increased by 15.9% since 2005. The number of flocks at risk of under-dosing through non-calibrated equipment has increased by 14.3% since 2005. The size of the in refugia population may have potentially doubled, as indicated by an increased compliance with the recommendation (wherever possible) to leave a portion of the flock untreated. However, whether this is indeed the case cannot be explicitly determined without a measure of the impact of various factors, including host immunity, environment/climate, previous anthelmintic treatment and the species of parasite present.

Parasite control in sheep: A risky business

Sheep are infected with a range of parasites, for which appropriate and effective control strategies are required. Changing patterns of disease and the inability to control parasitic infections effectively require the implementation of risk-based approaches to parasite control for many of the major parasitic diseases affecting sheep. Developing nematode resistance to anthelmintics necessitates changes to conventionally worming programmes that reduce the risk of further development of anthelmintic resistance through incorporation of new anthelmintic classes and products, along with ‘best practice’ guidelines for anthelmintic usage. Climatic changes pose a greater risk to sheep flocks through spread of parasites, such as Haemonchus contortus and Fasciola hepatica, which are parasites inextricably linked to high rainfall and increasing temperatures. Intensification increases the risk from diseases such as coccidiosis and it is now advocated that a risk-based approach to the control of coccidia infection in lambs should be based on strategic, treatments interventions linked to identified periods of risk. Concerns over the risks from the use of ectoparasiticides, have seen the demise of sheep dipping in many countries leading to increasing levels of ectoparasitic infections. At the same time, greater reliance has been placed on the use of injectable macrocyclic lactones, which inadvertently may also increase selection pressure for anthelmintic resistance. As a consequence of all the above factors, risk-based approaches to parasite control need to consider the strategic use of antiparasitics for individual target parasites, as well as needs to integration and rationalisation of all the component strategies.

Surveying the management practices and research needs of graziers in the New England region of New South Wales

The inaugural committee of the Cicerone Project commissioned a survey of livestock producers in the New England region to determine the research problems and production practices which were of greatest importance to graziers. In addition, an assessment was made of the level of interest livestock producers had in participating in a proposed producer-led research and adoption project. The survey was mailed to livestock producers in five districts across the New England region during October and November 1997. The survey results concerning land and pasture management issues suggested that a majority of livestock producers in the New England region found the challenges of dry seasons, fertiliser use, pasture composition and pasture persistence to be major problems. A further issue identified was the problem of resistance to drenches used for internal parasite control in sheep. It was clear that producers depend largely on pastures as the primary feed source due to the high cost of supplementary feed. There was considerable interest in learning how to fill gaps in the feed supply, and the management of the feed supply through droughts. Thus, one desired focus of future studies was to explore management systems that might improve the productivity, resilience, stability and longevity of pastures in the New England region. In addition, a focus on grazing management and its effects on pastures and on internal parasite control was suggested by survey respondents. Of the 316 responses to the survey, 76% expressed interest in becoming involved in the Cicerone Project, confirming the desirability of forming a producer-led research and adoption network within the New England region. One hundred and eighty-one respondents expressed an interest in becoming partner members, 100 respondents indicated they were interested in having their farm included in a network, while 139 people were interested in attending regional workshops where further details about the nature of the Cicerone Project would be developed. The survey was clearly of interest to commercial-scale livestock producers as the average size of respondents’ sheep flocks and cattle herds was over 5000 and 500, respectively. The results of this survey provided empirical evidence to support the formation of the Cicerone Project, which was created in 1998 following the approval of a business plan by the primary funding agency, the Woolmark Co.

A computer simulation study to evaluate resistance development with a derquantel–abamectin combination on UK sheep farms

UK guidelines for the sustainable control of parasites in sheep (SCOPS) aim to delay further development of anthelmintic drug resistance. This study describes a computer model evaluation of resistance development with a novel oral formulation of derquantel–abamectin, to inform recommendations for use. Two different farm management scenarios, based on UK field data, were modelled to simulate low refugia (non SCOPS) or high refugia (SCOPS) worm populations. The effect on resistance allele frequencies and field efficacy of several treatment scenarios using the novel active derquantel (DQL), a spiroindole (SI), as either a single or multiple active formulation with abamectin (ABA), a macrocyclic lactone (ML), under the two farm management systems was evaluated. The initial resistance allele frequency for DQL was set at 0.0001, assuming that resistance in the UK is low, and for ML at 0.165 or 0.8, assuming that resistant nematode populations exist in the UK. DQL resistance reached a level at which a reduction in field efficacy might be detected (resistance allele frequency 0.25) by year 16 when used sequentially, and by year 31 when used in annual rotation (ABA) with SCOPS management inputs, and by year 5 (sequential) and by year 10 (annual rotation) with non SCOPS management inputs. ML resistance reached a level at which a reduction in ABA field efficacy might be detected (resistance allele frequency 0.25) by year 4 when used sequentially, and by year 8 when used in annual rotation with DQL and SCOPS management inputs, and by year 1 (sequential) and by year 2 (annual rotation) with non SCOPS management inputs. No detectable reduction in field efficacy was observed for DQL–ABA after 40 years of use with SCOPS management inputs for simulations using an initial ML resistance allele frequency of 0.165 and 0.8. A detectable reduction in field efficacy was observed for DQL–ABA by year 32 (initial ML resistance allele frequency=0.165) and by year 6 (initial ML resistance allele frequency=0.8) with non SCOPS management inputs. In summary, the results suggest that formulating DQL in combination with ABA confers a substantial advantage in delaying the development of both DQL and ML resistance, and the provision of adequate refugia further extends this advantage.

Exploring flubendazole formulations for use in sheep. Pharmacokinetic evaluation of a cyclodextrin-based solution

BackgroundFlubendazole (FLBZ) is a poor water solubility broad-spectrum BZD methylcarbamate anthelmintic compound. Cyclodextrins (CDs) are usually used to increase aqueous solubility of poor hydrosoluble compounds. The comparative in vitro aqueous solubility of FLBZ and other BZD anthelmintics in the presence of hydroxypropyl-β-cyclodextrin (HPβCD) was evaluated in the current work. Additionally, the comparative pharmacokinetic behaviour of FLBZ (and its metabolites) administered by the intraruminal (i.r.) or intraabomasal (i.a.) routes to sheep as either an aqueous CDs-based solution or a conventional carboximethylcellulose (CMC) suspension was assessed. Drug solubility studies involving albendazole, mebendazole, oxfendazole and FLBZ were performed in an aqueous solution (pH 1.2 or 7.4) with or without HPβCD (10%, w/v). The pharmacokinetic study involved two experiments. Experiment 1: In a crossover study, sheep received either a FLBZ-CDs solution (n = 3) or a FLBZ-CMC suspension (n = 3) by the i.r. route (3.8 mg/kg). The treatment Groups were reversed after a 21-days washout period. Experiment 2: sheep (n = 4) were treated by the i.a. route with the FLBZ-CDs solution (3.8 mg/kg). Plasma and abomasal fluid samples were collected between 0 and 72 h post-treatment. Samples were analysed by HPLC.ResultsImprovement of FLBZ aqueous solubility due to CDs resulted markedly higher than that observed for mebendazole and albendazole. However, oppositely to what was expected, the absorption-related pharmacokinetic parameters did not show any marked formulation-dependant effect. After the i.a. administration of FLBZ, the AUC and the Tmax of the parent compound were significantly (P < 0.05) reduced, which is consistent with ruminal bypass.ConclusionThe administration of FLBZ as a CDs-based solution, does not seem to achieve great practical relevance for parasite control in sheep.