Control Of Parasites In Sheep Research Articles

SCOPS and COWS—‘Worming it out of UK farmers’

Infections with gastrointestinal roundworms are an important cause of production losses in sheep and cattle. Worm control is a vital part of health and production management in sheep flocks and cattle herds in the UK, and good control is highly dependent on effective anthelmintics. Unfortunately, a direct and unavoidable consequence of using anthelmintics to control worm populations is selection for individuals that are resistant to the chemicals used.If left unchecked, anthelmintic resistance (AR) could prove to be one of the biggest challenges to sheep and cattle production and animal welfare within the UK. As a consequence of increasing reports of AR in sheep, a working group, “SCOPS” (sustainable control of parasites in sheep) was formed in 2003 with representatives from the UK sheep industry to promote practical guidelines for sheep farmers and their advisors. This led to the production of guidelines for ‘sustainable worm control strategies for sheep’ intended for veterinarians and sheep advisors, plus ongoing promotional literature aimed at farmers.Whilst there is some evidence of emerging resistance in roundworms of cattle, it appears to still be at a very low level in the UK. However the potential presence of such AR in cattle worms has been seen as a timely warning, which if ignored, could lead to a not dissimilar AR situation to that seen in sheep, and in other cattle areas around the world. Reports of AR in UK cattle nematodes have generally been limited to a small number of anecdotal reports of treatment failure with some macrocyclic lactone (ML) products, especially those formulated as pour-on preparations, and invariably involving the dose-limiting species, Cooperia oncophora. As a consequence of these observations, guidelines have been produced similar to those for sheep, for sustainable worm control strategies for cattle “COWS” (control of worms sustainably), and were launched in May 2010. Uptake and effectiveness of SCOPS recommendations are currently being monitored in collaboration with the UK animal health industry, and similar proposals are being considered for uptake of COWS guidelines following the launch this year.

Efficacy of a combined oral formulation of derquantel–abamectin against the adult and larval stages of nematodes in sheep, including anthelmintic-resistant strains

Derquantel (DQL), a semi-synthetic member of a novel anthelmintic class, the spiroindoles, in combination with abamectin (ABA) [as the combination product STARTECT®] is a new entry for the treatment and control of parasites in sheep. The 19 studies reported herein were conducted in Australia, New Zealand, South Africa and the United Kingdom to demonstrate the efficacy of derquantel–abamectin (DQL–ABA) against a broad spectrum of gastrointestinal and respiratory nematodes of sheep, and to support registration of the combination product. Eleven studies were conducted using natural or experimental parasite infections with unknown or unconfirmed resistance, while eight studies utilised isolates/strains with confirmed or well characterised resistance to one or more currently available anthelmintics, including macrocyclic lactones. All studies included DQL–ABA and negative control groups, and in selected studies one or more reference anthelmintic groups were included. In all studies the commercial formulation of DQL–ABA was administered orally at 2mg/kg DQL and 0.2mg/kg ABA; placebo was administered in the same volume as DQL–ABA; and reference anthelmintics were administered as per label recommendations, except in one instance where levamisole was administered at twice the label dose. Infection, necropsy, worm collection and worm counting procedures were performed using standard techniques. Efficacy was calculated based on the percentage reduction in geometric mean worm count relative to negative control for each nematode species and lifecycle stage targeted. Twenty-two isolates/strains used in the eight studies targeting resistant worms had proven resistance: three to one anthelmintic class, eleven to two classes and eight to three or more classes; of these resistant strains, 16 demonstrated resistance to a macrocyclic lactone anthelmintic. Regardless of resistance status in the 19 studies, DQL–ABA controlled a broad range of economically important gastrointestinal and respiratory nematode parasites of sheep, as follows: ≥98.9% efficacy against Haemonchus contortus (adult and L4); Teladorsagia circumcincta (adult, L4 and hypobiotic L4); Teladorsagia trifurcata (L4); Trichostrongylus axei (adult and L4); Trichostrongylus colubriformis (adult and L4); Trichostrongylus falculatus (adult); Trichostrongylus rugatus (adult); Trichostrongylus vitrinus (adult and L4); Cooperia curticei (adult and L4); Cooperia oncophora (adult and L4); Nematodirus spathiger (adult); Nematodirus battus (adult); Nematodirus spp. (hypobiotic L4); Strongyloides papillosus (adult); Strongyloides spp. (L4); Chabertia ovina (adult); Oesophagostomum venulosum (adult); Dictyocaulus filaria (adult); and Protostrongylus rufescens (adult); ≥97.0% efficacy against Trichuris ovis (adult); and ≥95.9% efficacy against T. trifurcata (adult). Derquantel–abamectin is a highly effective combination anthelmintic, which will provide an important new tool for controlling helminths of sheep when used in conjunction with sustainable drenching practices.

Multiple resistance to anthelmintics in sheep nematodes and comparison of methods used for their detection

Intensification of animal production systems has led to an increased reliance on effective anthelmintics to control parasitic worms. However, the excessive and continued use of these “wormers” can lead to high selection pressures and have resulted in increased reports of emerging nematode populations exhibiting resistance to all of the main anthelmintic classes. Faecal egg count reduction tests (FECRT) were conducted on six farms in England and Wales according to standardised guidelines produced by the World Association for the Advancement of Parasitology. Selected farms were identified from a network of 40 study farms participating in a study investigating implementation of Sustained Control of Parasites in Sheep (SCOPS) principles. Resistance to the larval development test (LDT) to either benzimidazole- or imidazothiazole-group anthelmintics had been previously detected on these farms. In this study, resistance was indicated as present by LDT and/or FECRT to one or more groups of anthelmintics on a number of the study farms. Comparisons were made between results obtained by the two tests on the six farms. Benzimidazole resistance was identified by FECRT on five farms; imidazothiazole resistance on four farms and macrocyclic lactones resistance on five farms. The LDT identified the presence of benzimidazole resistance on all six farms, and imidazothiazole resistance on five farms. Generally, there was good agreement between the two tests in identifying both benzimidazole and imidazothiazole resistance. On one farm, the LDT identified the presence of benzimidazole-resistant nematodes, not detected by FECRT and on two farms the presence of imidazothiazole-resistant nematodes not detected by FECRT. On two farms “triple” resistance (i.e. resistance to all three groups of anthelmintics) was identified by FECRT and on one farm moxidectin resistance was suspected based on an early return to egg laying at 28 days post-treatment. Resistance was present in one or more genera, but most commonly in Teladorsagia on all six farms.

Parasitology in the practice laboratory: Part 1

of decreased productivity in the United Kingdom (UK), costing the UK national flock an estimated £84 million annually (Nieuwhof and Bishop, 2005). There have been recent reports of changes in UK parasite epidemiology. Haemonchus contortus and Fasciola hepatica are becoming both more common and more widespread; warmer autumns and longer grazing seasons are allowing parasite development to continue to occur later in the year and larvae to overwinter in greater numbers. Nematodirus battus, conventionally seen in young lambs in spring, is being recorded increasingly during autumn. In addition, anthelmintic resistance is now being identified much more commonly in the UK.At least eight UK cases of triple resistance to benzimidazole, levamisole and ivermectin in Teladorsagia have been identified, and experience suggests that the true incidence may be much higher. The sustainable control of sheep parasites in the UK has been considered by an industry and government workshop and the Sustainable Control of Parasites in Sheep (SCOPS) advisory manual produced (Abbott and others, 2004), outlining suggested new parasite control guidelines to minimise the selection for resistant worms. There is a strong argument that cattle enterprises should also be concentrating on avoiding the development of resistance before it becomes a real problem in their sector. They also need to consider other concerns, such as the spread of liver fluke and the control of lungworm in late summer, and in adult animals. Veterinary surgeons dealing with farm animal parasitology need to be able to provide the following services:

Efficacy of eprinomectin pour-on in naturally Oestrus ovis infested merino sheep in Extremadura, South-West Spain

The aim of this study is to evaluate the efficacy of the eprinomectin pour-on in naturally Oestrus ovis-infested sheep. To carry out this trial, 14 naturally infected sheep from the same flock were used. The animals were randomly distributed in three groups: group 1 (non-treated sheep), group 2 treated with 0.5 mg/kg bodyweight and group 3 treated with 1 mg/kg bodyweight of eprinomectin. The sheep were slaughtered 15 days after treatment and their heads were sectioned to count and identify larvae instar. The following results were obtained: Group 1: the average was 34 live and 0.75 dead larvae per sheep. Group 2: the efficacy of the eprinomectin was 83.5% against O. ovis group 3: the efficacy of the eprinomectin pour-on was 100%. Drug analysis was made to determine plasma eprinomectin concentration 9 days after treatment and the average concentrations in groups 2 and 3 were 1.23 and 3.04 ng/ml, respectively. The statistical study showed a significant difference between the efficacy and the dose used, and there was correlation between the plasma concentration of eprinomectin and the dose. The efficacy and easy application allow us to take into account this endectocide as an alternative method in the integral control of parasites in sheep.

Issues Associated with Research on Sheep Parasite Control in New Zealand – a Descriptive Ethic

In common with much of theEnglish-speaking world, New Zealandersgenerally oppose the use of animalexperimentation where there is no demonstrableand immediate benefit for human, animal, orenvironmental health. Intrusive experiments onsheep internal and external parasites publishedbetween 1996 and 2000 are reviewed, anddiscussed in relation to these publicsensibilities. A total of 16 publishedexperiments on sheep parasites involvedsurgical manipulations or other intrusiveprocedures. Some of these experiments had noshort-term application, or the only applicationwas in increasing animal production. Otherscould have been modified at some extra expenseso that they were less intrusive. Still otherswere duplications of previous work. All thesemanipulations would be unacceptable accordingto the orthodox morality of the general public.Breeding programs, rotation of grazing,``low-tech'' vaccination, and in vitromodels of sheep can provide insights intopreventing parasite infestation withoutintrusive experiments. Such research protocolsshould take priority over existing programs.The results also confirm earlier reports thatanimal ethics committees are not fulfillingtheir mandated objective of acting as watchdogsfor the public. Possible changes in New Zealandanimal welfare legislation and itsinterpretation by Animal Ethics Committees arediscussed.

Parasite control in sheep

In PracticeVolume 16, Issue 6 p. 309-318 Farm Animal Practice Parasite control in sheep Gerald Coles, Gerald ColesSearch for more papers by this author Gerald Coles, Gerald ColesSearch for more papers by this author First published: 01 November 1994 https://doi.org/10.1136/inpract.16.6.309Citations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume16, Issue6November 1994Pages 309-318 RelatedInformation

Anthelmintic resistance in nematodes: Extent, recent understanding and future directions for control and research

Resistance has now been reported to all of the broad spectrum anthelmintic types currently available, namely to the benzimidazoles, levamisole/morantel and to ivermectin. The problem causes most concern for parasite control in sheep, but anthelmintic resistance has also been reported in nematodes of horses, goats, pigs and more recently cattle. Our understanding of the factors which select rapidly for resistance has increased and programmes of worm control which minimize selection for anthelmintic resistance are being developed and tested. One of the greatest problems encountered in attempting to reduce the selection for overt drug resistance is the need for more sensitive tests for developing resistance. In the long term, new approaches to chemotherapy and to overcoming anthelmintic resistance problems will arise from improving our understanding of the modes of action of, and mechanisms of resistance to, anthelmintics at the level of the receptor proteins and their genes.