Parasitic Nematodes In Sheep Research Articles

Bacteria associated with ovine gut parasites Trichuris ovis and Haemonchus contortus.

An associated microbiome of any host helps it in different metabolic processes ranging from the decomposition of food to the maturation of gametes. Organisms with a parasitic mode of life, though present at nutritious sites inside their host, maintain their own microbiome. Nevertheless, the comprehensive characterization and functionality of microbiome in parasitic organisms remain understudied. We selected two nematode parasites of Kashmir Merino sheep viz;Haemonchus contortus and Trichuris ovis based on their higher prevalence, difference in mode of nutrition, habitation site and effect on host. The objective of the study was to explore the bacteria associated with these parasitic nematodes of sheep. We adopted a 16S rRNA metagenomic sequencing approach to estimate and compare the bacterial communities present in these two nematode species. Nematode parasites from Kashmir Merino sheep were identified morphologically and confirmed with DNA characterization. H. contortus was dominated by phylum Proteobacteria (57%), Firmicutes (25%), Bacteroidota (15%) and Actinobacteriota (3%). Conversely, T. ovis showed Proteobacteria (78%) followed by Firmicutes (8%), Bacteroidota (8%), Actinobacteriota (1%), Fusobacteriota (1%) and other phyla (4%). This study provides a comprehensive account of the microbiome composition of H. contortus and T. ovis, both of which are highly prevalent among Kashmir Merino sheep. Additionally, T. ovis exhibited a greater bacterial diversity compared to H. contortus. Notably, these nematodes were found to harbor certain pathogenic bacteria. This study can further be carried forward in gaining insights into the complex relationship between the microbiota of a parasite and its pathogenicity, reproductive potential and host microbiome modification.

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.

Predatory activity and passage of six nematophagous fungi species in gastrointestinal tract of trichostrongylide-infected sheep

ABSTRACTWith the development of anthelmintic resistance of parasitic nematodes, screening the potential of predatory fungi candidates by in vitro and in vivo assay is necessary for biocontrol of parasitic nematodes in sheep. Fifteen native isolates of fungi species of six predators were evaluated through in vitro and in vivo experiment to evaluate the capacity of passing through the gastrointestinal tract of sheep. The results of the in vitro experiment showed that the reduction percentages of the third-stage larvae (L3) of trichostrongylides in faeces were 97.02–98.49% for five isolates of Arthrobotrys (Monacrosporium) sinense; 83.47–99.12% for three isolates of Arthrobotrys oviformis; 80.00–97.41% for four isolates of Arthrobotrys conoides; and 99.18%, 77.56%, and 75.72% for one isolate of Arthrobotrys microscaphoides, Arthrobotrys salina, and Dactylellina leptospora, respectively. In the in vivo assay, the results exhibited that the larval recoveries in faeces were significantly decreased (p < .05), and L3 reduction percentage ranged from 37.84% to 86.93% for all fungal isolates tested, except for one isolate of D. leptospora. After fungal treatment (within 24 h) of one isolate of A. salina, although the efficacy against L3 was 43.83%, tested fungus was detected in the faeces. The remaining isolates, except one isolate of D. leptospora and one isolate of A. conoides, were positive for either L3 reduction or fungal survival in faeces. The present study showed that nematophagous fungi could survive in the passage through the alimentary tract of sheep and should be potential candidates as a feed supplement.

Comparison of two in vitro methods for the detection of ivermectin resistance in Haemonchus contortus in sheep

Summary Gastrointestinal parasitic nematodes in sheep cause severe economic losses. Anthelmintics are the most commonly used drugs for prophylaxis and therapy against parasitic helminths. The problem of drug resistance has developed for all commercially available anthelmintics in several genera and classes of helminths. In vitro and in vivo tests are used to detect anthelmintic resistance. Two in vitro methods (larval migration inhibition test and micromotility test) for the detection of ivermectin (IVM) resistance were compared using IVM-resistant and IVM-susceptible isolates of Haemonchus contortus. The degree of resistance for each test was expressed as a resistance factor (RF). The micromotility test was more sensitive for quantitatively measuring the degree of resistance between susceptible and resistant isolates. The RFs for this test for IVM and eprinomectin ranged from 1.00 to 108.05 and from 3.87 to 32.32, respectively.

In vitro ovicidal and larvicidal activity of condensed tannins on gastrointestinal nematode infestations in sheep (Ovis aries)

Infestations of gastrointestinal parasitic nematodes in sheep result in significant costs to farmers. These infestations are controlled using synthetic anthelmintic treatments, which can result in the development of anthelmintic resistance in nematodes. The use of plants rich in condensed tannins (CTs) is a promising alternative for controlling infestations of harmful parasites in sheep, and could allow reduction of the chemical products used. This study investigated the in vitro effect of CTs from Acacia mearnsii extract (AE) on egg hatching and motility of third-stage larvae. Egg-hatching rate was measured after incubation with extracts for 48 h at 27 °C. The egg hatch test was performed with dilutions of 0.09, 0.19, 0.39, 0.78, 1.56, 3.12, 6.25, 12.5, 25, 50, and 100 mg mL-1. Distilled water was used as the negative control. The corresponding egg hatching inhibition percentages were 22.3, 32.3, 39.2, 49.1, 56.7, 59.0, 62.3, 77.3, 92.7, 98.3, and 100%. The concentration required to inhibit egg hatching in 50% of eggs (LC50) was 2.85 mg mL-1. The inhibition achieved with the negative control was 7.06%. A larval migration inhibition test was carried out after incubation with the extracts for 48 h at 27 oC, with AE and distilled water used in dilutions of 3.12, 6.25, 12.5, 25, 50, and 100 mg mL-1. The corresponding percentages of migration inhibition were 16.5, 37.0, 56.3, 79.4, 91.8, and 97.1%. The concentration required to inhibit migration of 50% of larvae (LC50) was 12.45 mg mL-1. The inhibition achieved with the negative control was 8.53%. The in vitro ovicidal and larvicidal activity of CTs from AE indicate the anthelmintic effect of AE, suggesting the potential of CT extracts to be used as alternatives for controlling gastrointestinal nematode infestations in small ruminants.

Efficacy of monepantel, derquantel and abamectin against adult stages of a multi-resistant Haemonchus contortus isolate

Drug resistance in gastrointestinal nematodes is a severe problem for sheep farmers. With the recent introduction of monepantel (Zolvix®) and of derquantel plus abamectin (Startect®) in New Zealand, two new anthelmintic classes will be available to control gastrointestinal nematodes. While monepantel covers a broad spectrum of nematodes, the efficacy of derquantel is mid-spectrum and limited to a smaller number of species and stages. The combination of derquantel and abamectin allows to enlarge the spectrum and to cover most parasitic nematodes in sheep. However, the question remained open, if the efficacy of the new anthelmintics can be maintained in the presence of severe anthelmintic resistance. The present study investigated the efficacy against adult stages of a multi-resistant Haemonchus contortus isolate. While monepantel resulted in 100 % elimination, derquantel in combination with abamectin resulted in efficacies <95 % (faecal egg counts and worm counts).

Screening for the presence of nematophagous fungi collected from Irish sheep pastures

With worldwide development of anthelmintic resistance, alternative approaches to the chemotherapeutic dominant approach for the control of parasitic nematodes in sheep are urgently required. As natural enemies of nematodes, nematophagous fungi offer the exciting possibility of an alternative to the dominant anthelmintic approach for parasite control in ruminants. Permanent sheep pasture harbor a promising array of nematophagous fungi and merits further investigation. One hundred and fifty samples of soil, old and fresh faeces were collected from 10 Irish sheep pastures. The three methods employed for the isolation of nematophagous fungi include the Baermann technique, flotation method and the sprinkling–baiting technique. Twenty-nine nematophagous fungi were observed of which 12 were predacious and 17 were endoparasitic. The most prevalent fungi were Cystopage lateralis, Stylopage hadra, Drechmeria coniospora and Meristacrum asterosperum. Permanent sheep pasture is a good source of nematophagous fungi and hence may harbor potential biological control agents. Monacrosporium cionopaga, Duddingtonia flagrans, D. coniospora and Hirsutella rhoissilensis were detected in fresh faecal samples indicating they may have survived the gastrointestinal tract and therefore a viable option as a biological control agent.

Tanniferous forage plants: Agronomic performance, palatability and efficacy against parasitic nematodes in sheep

AbstractTanniferous forage plants can have beneficial effects on ruminant productivity and health (improved protein supply, bloat safety and antiparasitic properties). However, condensed tannins can also lower palatability, voluntary feed intake and digestibility. The aim of our interdisciplinary project was to generate basic knowledge on plant management, feed palatability and the antiparasitic properties of tanniferous forage plants for their practical application in agronomy, focusing on their usefulness in controlling gastrointestinal nematodes in organic farming. We found thatOnobrychis viciifolia(sainfoin),Lotus corniculatus(birdsfoot trefoil) andCichorium intybus(chicory) were suitable for cultivation under the given temperate climatic conditions, whereasLotus pedunculatus(big trefoil) was soon outcompeted by unsown species. Growing the tanniferous plant species in a mixture withFestuca pratensis(meadow fescue) rather than in a monoculture had the advantage of increasing total dry matter (DM) yield (especially in the case of tanniferous legumes) and of reducing the DM proportions of unsown species. However, due to dilution by non-tanniferousF. pratensis, the tannin concentrations of mixtures were clearly lower and the seasonal fluctuations in tannin concentrations greater than that of monocultures. Across species, tannin concentrations were highest forO. viciifolia, followed byL. corniculatusand very low forC. intybus. Palatability of all tanniferous forages was comparable to that of a ryegrass/clover mixture when fed as dried forage and, when offered as silage, palatability ofO. viciifoliawas clearly superior to that of the respective ryegrass/clover control. Administration of dried or ensiledO. viciifoliareduced parasite egg counts in feces of lambs co-infected with the gastrointestinal nematode speciesHaemonchus contortusandCooperia curticei. We conclude thatO. viciifoliais the most promising among the tested tanniferous forage plant species due to its suitability for cultivation, its high tannin concentration, its high palatability and its antiparasitic activity even in dried or ensiled form.

Prevalence of anthelmintic resistance on sheep farms in New Zealand

AIM: To establish the prevalence of anthelmintic resistance in parasitic nematodes on sheep farms in New Zealand. METHODS: A cross-sectional prevalence study was conducted, using a standardised faecal nematode egg count (FEC) reduction (FECR) test (FECRT) for ivermectin, at a full (0.2 mg/kg) and half (0.1 mg/kg) dose rate, and albendazole, levamisole and albendazole-levamisole in combination, on 60 lambs (n=10 per group) on farms selected from throughout New Zealand. Farms that conformed with selection criteria were chosen at random (n=80) or with a history of suspected resistance to macrocy- clic lactone (ML) anthelmintics (n=32). Resistance to an an- thelmintic was inferred when there was <95% reduction in FEC 7-10 days after treatment. Larval cultures were performed for all control groups and for treated groups for which resistance was evident. RESULTS: Of the farms randomly selected, 36% showed ≥95% FECR for all anthelmintics tested; resistance to ivermectin at 0.1 and 0.2 mg/kg liveweight was evident on 36% and 25% of these farms, respectively. Resistance to both ivermectin (0.2 mg/kg) and levamisole was evident on 8/80 (10%) farms, to ivermectin and albendazole on 10/80 (13%) farms, and to iver- mectin, levamisole and albendazole on 6/80 (8%) farms. The prevalence of resistance to a half dose of ivermectin tended to be more prevalent on farms with a history of suspected ML resistance (p=0.06). Resistance to albendazole was seen across all the main parasite genera, and to levamisole in Nematodirus, Ostertagia (= Teladorsagia) and Trichostrongylus species. Resistance to ivermectin was dominated by Ostertagia spp, although Cooperia, Nematodirus and Trichostrongylus species were also implicated. CONCLUSION: Anthelmintic resistance in parasitic nema-todes of sheep is common in New Zealand. Not only was resistance to albendazole and levamisole common, but resistance to the ML, ivermectin, was at a higher prevalence than expected. Sheep farmers and advisors in New Zealand need to re-evaluate the way they manage parasites, and more research is urgently needed if the steady decline in anthelmintic susceptibility is to be halted.

Discovery of quantitative trait loci for resistance to parasitic nematode infection in sheep: I. Analysis of outcross pedigrees

BackgroundCurrently most pastoral farmers rely on anthelmintic drenches to control gastrointestinal parasitic nematodes in sheep. Resistance to anthelmintics is rapidly increasing in nematode populations such that on some farms none of the drench families are now completely effective. It is well established that host resistance to nematode infection is a moderately heritable trait. This study was undertaken to identify regions of the genome, quantitative trait loci (QTL) that contain genes affecting resistance to parasitic nematodes.ResultsRams obtained from crossing nematode parasite resistant and susceptible selection lines were used to derive five large half-sib families comprising between 348 and 101 offspring per sire. Total offspring comprised 940 lambs. Extensive measurements for a range of parasite burden and immune function traits in all offspring allowed each lamb in each pedigree to be ranked for relative resistance to nematode parasites.Initially the 22 most resistant and 22 most susceptible progeny from each pedigree were used in a genome scan that used 203 microsatellite markers spread across all sheep autosomes. This study identified 9 chromosomes with regions showing sufficient linkage to warrant the genotyping of all offspring. After genotyping all offspring with markers covering Chromosomes 1, 3, 4, 5, 8, 12, 13, 22 and 23, the telomeric end of chromosome 8 was identified as having a significant QTL for parasite resistance as measured by the number of Trichostrongylus spp. adults in the abomasum and small intestine at the end of the second parasite challenge. Two further QTL for associated immune function traits of total serum IgE and T. colubiformis specific serum IgG, at the end of the second parasite challenge, were identified on chromosome 23.ConclusionDespite parasite resistance being a moderately heritable trait, this large study was able to identify only a single significant QTL associated with it. The QTL concerned adult parasite burdens at the end of the second parasite challenge when the lambs were approximately 6 months old. Our failure to discover more QTL suggests that most of the genes controlling this trait are of relatively small effect. The large number of suggestive QTL discovered (more than one per family per trait than would be expected by chance) also supports this conclusion.

Biological control of nematode parasites in sheep1

In a world in which sheep producers are facing increasing problems due to the rapid spread of anthelmintic resistance, the battle against gastrointestinal parasitic nematodes is a difficult one. One of the potential new tools for integrated control strategies is biological control by means of the nematode-destroying microfungus Duddingtonia flagrans. This fungus forms sticky traps that catch developing larval stages of parasitic nematodes in the fecal environment. When resting spores (chlamydospores) of this fungus are fed daily to grazing animals for a period of time, the pasture infectivity and thus, the worm burden of grazing animals are lowered, especially in young lambs. Research has been conducted throughout the world covering many different climates and management systems. An Australian parasite model showed that if the fungus performs efficiently (> or =90% reduction in worm burden) for 2 or 3 mo, it should contribute significantly to a reduction in the number of dead lambs otherwise occurring when managed only by anthelmintic treatment and grazing management. Feeding or field trials have clearly demonstrated that dosing with a few hundred thousand spores per kilogram of live BW not only reduced the number of infective larvae but also increased the BW of the lambs compared with controls not given fungus. Initial Australian work with feeding spores by means of a block formulation or a slow-release device has shown some promise, but further work is needed to fully develop these delivery systems. In tropical Malaysia, small paddock trials and field studies resulted in significant improvements, in terms of lower worm burdens and increased live BW, when feeding half a million spores daily to grazing lambs. Additional benefits have been observed when the fungus is employed in combination with a fast rotational grazing system. Research has also demonstrated that spores can be delivered in slightly moist feed block material, but only if such blocks are consumed rapidly, because of their very short shelf life. In the northern, temperate Danish climate it has been demonstrated that daily feeding of half a million spores per kilogram of live BW can lead to significant production benefits, with increased live BW gain in fungus-exposed animals. Biological control of parasitic nematodes in sheep seems to hold promise for the future, but to be able to assist producers, the optimal delivery system needs to be refined and further developed. In addition, more work will be needed to define the best use of this technology in different geographic regions.

Synthesis and Anthelmintic Activity of 7-Hydroxy- 5-oxo-5H-thieno[3,2-b]pyran-6-carboxanilides and -6-thiocarboxanilides

7-Hydroxy-5-oxo-5H-thieno[3,2-b]pyran-6-carboxanilides and -6-thio-carboxanilides represent a novel series of anthelmintic compounds, with broad-spectrum activity against important parasitic nematodes in sheep and dogs. In particular, an improved efficacy against Trichostrongylus colubriformis in sheep over the related 3-carbamoyl-4-hydroxycoumarins has been noted. New synthetic routes to the key intermediate, 7-hydroxythieno[3,2-b]pyran-5-one, have been developed.

Restriction fragment length patterns of dna from parasitic nematodes of sheep

High molecular weight DNA obtained from sheep parasitic nematodes Haemonchus contortus, Ostertagia circumcincta and Trichostrongylus colubriformis, was digested with various restriction endonucleases. Digestion with Eco R1 produced the most informative pattern of repeat sequence bands. H contortus adult or larval DNA produced bands of 2.7, 3.0 and 1.4 kb. O circumcincta adult or larval DNA had common 2.7 and 1.4 kb bands with adult specific bands of 2.2 and 0.9 kb and a larval specific 2.08 kb band. T colubriformis adults or larval DNA produced 2.7, 1.4 and 0.79 kb bands. These preliminary results show that restriction patterns of repeat sequence DNA may be useful for the identification of various trichostrongylid species parasitic for sheep.

Ecological Studies on Nematodirus species in Sheep in Manawatu district, New Zealand

The study of populations of animals has received the attention of a large number of workers. Of these, however, but a few have been interested in the problem in its application to parasitic nematodes and in this field there is consequently a limited literature. Particularly is this so when the parasitic nematodes of sheep are considered, the incentive for study of which, in most cases, has been the pressing need for their destruction. This desire has been fulfilled to a greater or lesser degree, but at the expense of researches which would have contributed to a more fundamental knowledge of the ecological relationships of parasitic worms in general.