Resistance In Gastrointestinal Nematodes Research Articles

Faecal egg count reduction tests and nemabiome analysis reveal high frequency of multi-resistant parasites on sheep farms in north-east Germany involving multiple strongyle parasite species

Anthelmintic resistance in sheep parasitic gastrointestinal nematodes is widespread and a severe health and economic issue but prevalence of resistance and involved parasite species are unknown in Germany. Here, the faecal egg count reduction test (FECRT) was performed on eight farms using fenbendazole, ivermectin and moxidectin and on four farms using only moxidectin. A questionnaire was used to obtain data on management practices to potentially identify risk factors for presence of resistance. All requirements of the recently revised WAAVP guideline for diagnosing anthelmintic resistance using the FECRT were applied. Nematode species composition in pre- and post-treatment samples was analysed with the nemabiome approach. Using the eggCounts statistic package, resistance against fenbendazole, ivermectin and moxidectin was found on 7/8, 8/8 and 8/12 farms, respectively. No formal risk factor analysis was conducted since resistance was present on most farms. Comparison with the bayescount R package results revealed substantial agreement between methods (Cohen's κ = 0.774). In contrast, interpretation of data comparing revised and original WAAVP guidelines resulted in moderate agreement (Cohen's κ = 0.444). The FECR for moxidectin was significantly higher than for ivermectin and fenbendazole. Nemabiome data identified 4 to 12 species in pre-treatment samples and treatments caused a small but significant decrease in species diversity (inverse Simpson index). Non-metric multidimensional scaling and k-means clustering were used to identify common patterns in pre- and post-treatment samples. However, post-treatment samples were scattered among the pre-treatment samples. Resistant parasite species differed between farms. In conclusion, the revised FECRT guideline allows robust detection of anthelmintic resistance. Resistance was widespread and involved multiple parasite species. Resistance against both drug classes on the same farm was common. Further studies including additional drugs (levamisole, monepantel, closantel) should combine sensitive FECRTs with nemabiome data to comprehensively characterise the anthelmintic susceptibility status of sheep nematodes in Germany.

Reducing fecal egg count through selective breeding alters dorper lamb response to Haemonchus contortus in an artificial challenge trial

Infection by gastrointestinal nematodes (GIN), particularly Haemonchus contortus, can be detrimental to sheep health and performance. Genetic susceptibility to GIN varies between breeds, with those lacking high levels of natural resistance often requiring frequent anthelmintic treatment when facing parasitic challenge. Genetic technology can serve as a tool to decrease GIN susceptibility via selection for sheep with reduced fecal egg count (FEC) estimated breeding values (EBVs). However, the physiological changes that result from implementation of this strategy are not well described. Additionally, there is a need for comparison of animals from recent selective breeding against breeds with inherent GIN resistance. In this study we administered a challenge of H. contortus to Dorper x White Dorper (DWD; n = 92) lambs that have been genetically selected for either low (DWD-) or high (DWD+) FEC EBVs and Barbados Blackbelly x Mouflon (BBM; n = 19) lambs from a genetically resistant breed backgrounds. Lamb FEC, packed-cell volume (PCV) and serum IgG were measured at intermittent levels over 5 weeks. At day 21 and day 35, the selectively bred DWD- had a lower mean FEC compared to DWD+, but were higher than BBM. Reductions in both PCV and serum IgG from initial day 0 levels were observed in DWD lambs, but not in BBM. Furthermore, from a subset of lambs (n = 24) harvested at day 21, DWD- only tended (p = 0.056) to have lower mean worm counts than DWD+, with BBM having the lowest mean worm count. Differentially expressed genes (DEGs) identified via RNA-sequencing of abomasal tissue at day 21 indicate a more pronounced Th2 immune response and more rapid worm expulsion occurred in iBBM than iDWD- and iDWD+ lambs. However, gene expression in DWD- suggests an association between reduced FEC EBV and gastric acid secretion and the ability to limit worm fecundity. Ultimately, selection of Dorper sheep for low FEC EBV can reduce susceptibility to GIN, but it will likely require multiple generations with this trait as a breeding priority before presenting a similar resistance level to Caribbean breeds.

A SURVEY OF ANTHELMINTIC EFFICACY IN DAIRY GOAT FARMS IN SOUTH-EAST FRANCE

Goat’s milk production is an important activity in France. Gastrointestinal nematodes (GIN) remain a main threat for grazing goats, usually controlled using anthelmintic drugs (AH). However, 1) eprinomectin (EPN) is the sole molecule yet available without withdrawal time for milk in France; 2) nematodes AH resistances increase dramatically. First, a survey was performed on 13 farms in the Auvergne-Rhône-Alpes (AURA) region to evaluate the efficacy of 2 AH authorized for dairy goats: a benzimidazole (BZ) and a macrocyclic lactone (EPN pour-on). Fecal Egg Count Reduction Tests (FECRT) were carried out using 3 groups of 10 goats per farm: a control group, one treated with BZ (oxfendazole) and one treated with EPN. The results indicate a resistance to BZ in 11 out of 13 farms (84.6%) and a lack of efficacy for EPN pour-on in at least 10 farms (76.9%). Secondly, EPN was given orally or subcutaneously in 4 farms of the previous trial showing a lack of efficacy to EPN pour-on. A resistance to EPN was confirmed in 3 out of 4 farms. Although based on a few farms, these results confirm the high prevalence of resistance of GIN to BZ in dairy goat farms. They also highlight a high level of resistance to EPN and the lack of efficacy of EPN when used pour-on. Given the level of resistance to marketed drugs, there is an urgent need to explore alternative options to AH to prepare integrated, sustainable control of GIN.

114 The efficacy of a natural fungus (Duddingtonia flagrans) in reducing gastrointestinal nematode indicators in lambs

Abstract Sustainable and profitable small ruminant production in the US is affected by infections with gastrointestinal nematodes (GIN), especially the blood sucking GIN, Haemonchus contortus. The overuse and misuse of available drug classes has led to multi-drug resistant GIN that pose significant challenges to parasite control on many farms. The objective of this study was to evaluate the effectiveness of a natural fungus (Duddingtonia flagrans; Bioworma, International Animal Health) in reducing GIN larval counts and other GIN indicators in hair sheep wethers. Eighteen St. Croix (n = 9) and Barbados Blackbelly (n = 9) wethers (227 ± 1.4 days of age and 29.7 ± 0.6 kg BW) were dewormed (d 0) with a combination of levamisol (Prohibit; 8 mg/kg BW) moxidectin (Cydectin; 0.2 mg/kg BW) and albendazole (Valbazen; 7.5 mg/kg BW) prior to the start of feeding according to the manufacturer’s recommendations for feeding BioWorma. At this time, lambs were separated into two treatment groups (n = 9/group), split into 3 replications per treatment group and placed on six pasture paddocks (0.06 ha; n = 3 per paddock) after accounting for breed, initial fecal egg count (FEC) and BW. Lambs were then fed daily either a grain supplement ration (corn and soybean meal) with Livamol with Bioworma (LIV) or without (CON) at 2% of their BW for 98 d. LIV was added to the ration based on total lamb BW/paddock. To evaluate the effect of LIV treatment, BW and body condition scores (BCS) were recorded every 2 wk for 98 d. Blood and fecal samples were also collected for determination of packed cell volume (PCV) and FEC. Pooled treatment group feces (d 0 – 98) were collected and cultured to determine GIN genera. A subset of animals/treatment (n = 3) will be harvested to determine abomasal worm counts. Data were analyzed using repeated measures in a mixed model, and FEC were log transformed before analysis. Following deworming (d 0), FEC were reduced by 100% by d 14. There was a mixed population of GIN at the start of the study (averaging 54%, 42%, 1.2% and 1.8% for H. contortus, Tricostrongylus spp., Oesphagostomum spp. and Nematodirus spp., respectively). LIV with Bioworma supplementation had no impact on BW, BCS, PCV or FEC in this study averaging 34.2 ± 0.3 kg, 2.5 ± 0.04, 34.7 ± 0.5% and 150.9 eggs per gram, respectively. Under the conditions of this study, Bioworma® supplementation had no influence on GIN indicators measured up to 100 d of grazing. This research will be continued during subsequent grazing seasons to determine the effect of continued supplementation on lamb parasite load and performance as well as pasture infestation levels.

Genetic Parameter Estimation and Selection for Resistance to Gastrointestinal Nematode Parasites in Sheep-A Review.

Gastrointestinal nematodes (GINs) are a major problem affecting sheep production systems worldwide. The flocks infected with GINs can undergo significant economic losses due to a decrease in productivity, the animals' deaths, and the costs associated with treatments. The over-reliance on anthelmintics in the past years to eliminate GINs has resulted in the development of resistance against the available commercial anthelmintics. Genetically resistant animals can be used in mating systems to improve the overall flock resistance. This review aimed to summarize the estimated genetic parameters for resistance traits and genetic gains through the use of genetic/genomic selection for resistance to GINs in sheep. Heritability estimates from the literature ranged from 0.00 to 0.46 for fecal egg counts, 0.12 to 0.37 for packed cell volume/hematocrit, 0.07 to 0.26 for FAffa MAlan CHArt (FAMACHA©), from 0.10 to 0.37 for blood parameters, and 0.19 for Immunoglobulin A. Genetic correlations between traits measuring resistance to GINs and production traits ranged from negative to positive values in the literature. Genetic gains are possible when genetic/genomic selection for GIN resistance is applied. Therefore, genetic/genomic selection can be used to improve flocks' resistance to GINs as a sustainable approach in sheep production systems.

Investigating the perceived versus actual gastrointestinal nematode challenge on extensive sheep farms

Extensive farming systems form an integral part of sheep production systems across Europe. However, with innate production handicaps, declining sheep numbers and narrow economic margins, production is becoming increasingly challenging threatening the future sustainability of the industry. Gastrointestinal nematodes (GINs) are a significant cause of production losses to the global sheep industry, with well-established resistance to the major anthelmintic groups. Traditionally, extensive farming systems are not thought to have a significant parasite challenge compared with intensive farms, but there is a need to identify the scale and importance of GINs on extensive farms to inform the need for sustainable control strategies. In this study, a questionnaire of extensive farmers (n=34) was conducted and parasitological data were collected from nine study farms to investigate the perceived versus actual GIN and anthelmintic resistance challenge faced by extensive farms. The results showed a production-limiting challenge on most farms, with a higher GIN challenge observed on improved pastures. Furthermore, over half of the extensive farmers perceived anthelmintic resistance to be a greater problem for intensive farmers, with only 20% of respondents reporting known anthelmintic resistance. However, all study farms had evidence of resistance to at least one group of anthelmintics. Consequently, this study has demonstrated that despite the traditional perception of parasitism on extensive farms, there is a need to increasingly consider its impact and take a proactive approach to sustainable control, with solutions tailored to their unique management.

Genomic Regions Associated with Resistance to Gastrointestinal Nematode Parasites in Sheep-A Review.

Gastrointestinal nematodes (GINs) can be a major constraint and global challenge to the sheep industry. These nematodes infect the small intestine and abomasum of grazing sheep, causing symptoms such as weight loss, diarrhea, hypoproteinemia, and anemia, which can lead to death. The use of anthelmintics to treat infected animals has led to GIN resistance, and excessive use of these drugs has resulted in residue traced in food and the environment. Resistance to GINs can be measured using multiple traits, including fecal egg count (FEC), Faffa Malan Chart scores, hematocrit, packed cell volume, eosinophilia, immunoglobulin (Ig), and dagginess scores. Genetic variation among animals exists, and understanding these differences can help identify genomic regions associated with resistance to GINs in sheep. Genes playing important roles in the immune system were identified in several studies in this review, such as the CFI and MUC15 genes. Results from several studies showed overlapping quantitative trait loci (QTLs) associated with multiple traits measuring resistance to GINs, mainly FEC. The discovery of genomic regions, positional candidate genes, and QTLs associated with resistance to GINs can help increase and accelerate genetic gains in sheep breeding programs and reveal the genetic basis and biological mechanisms underlying this trait.

Worm control practices used by Thoroughbred horse managers in Australia: A national survey

This study assessed worm control practices used by Australian Thoroughbred farm managers with an online questionnaire survey. The questionnaire comprised 52 questions (close-ended: 44; open-ended: 8) about farm demography and general husbandry practices, farm managers’ knowledge of gastrointestinal nematodes (GIN) and their importance, diagnosis, worm control strategies and anthelmintics, anthelmintic resistance (AR) and grazing management. Following the pilot survey, the link for the questionnaire survey was sent to all (n = 657) registered members of the Thoroughbred Breeders Australia on 12th April 2020. The response rate for the questionnaire was 18.5% (122 of 675). The farm managers reported a good understanding of GIN and their importance in different age groups of horses as most respondents (70% of 122) perceived worm-related illness to be more important in young (i.e., foals, weanlings and yearlings) than adult (> 3 years old) horses. Although most respondents (93%, 113 of 122) used anthelmintics prophylactically to control GIN, only 15% (18 of 122) observed worm-related illness in their horses. Just under 40% of respondents were performing faecal egg counts, with less than 20% using the results of faecal egg counts to guide deworming decisions. The interval-based deworming strategy was the most common method (≥55% of 122 respondents) to control GIN in all age groups of horses. Macrocyclic lactones were the first choice of anthelmintics for all age groups of horses. Although the majority of respondents (88%, 107 of 122) perceived resistance in GIN against commonly used anthelmintics as an important issue in managing worms in horses, only 29% assessed the efficacy of anthelmintics and 91% (111 of 122) were unaware of AR on their properties. Grazing management practices, such as manure removal, were more frequently performed on smaller paddocks (<0.20 ha: 58%) than on larger paddocks (>0.20 ha: 18%). Multiple correspondence analyses showed that the likelihood of suboptimal worm control practices on small farms (n = ≤50 horses) was greater than that of medium (n = 51–100) and large (n = >100) farms. This study provides insights into the demography of Thoroughbred farms in Australia, husbandry practices used by stud managers and their knowledge about worms, control options and AR concerns, thereby paving the way for taking any initiatives to address the problem of AR in GIN of Australian Thoroughbred horses.

The first report of macrocyclic lactone resistant Dictyocaulus viviparus in the UK.

Abstract Background: The bovine lungworm Dictyocaulus viviparus negatively impacts bovine health and leads to substantial economic losses. Lungworm infections can be difficult to manage due to the unpredictable and severe nature of clinical outbreaks. Despite widespread use of long-acting macrocyclic lactones in grazing cattle in the UK, there have been no confirmed reports of resistant lungworm to date, with only one case of anthelmintic resistant lungworm confirmed worldwide. Methods: Lungworm Baermann filtrations were conducted on first season grazing dairy calves as part of a wider study investigating anthelmintic resistance in gastrointestinal nematodes in Scotland using the faecal egg count reduction test. Results: Clinical signs and significant numbers of lungworm larvae in faeces were observed post-treatment with either ivermectin or moxidectin. Resistant gastrointestinal nematode populations were also detected in both treatment groups. Conclusion: This short report describes the first evidence of macrocyclic lactone resistant D. viviparus in the UK.

219 Identification of Functional Single Nucleotide Polymorphisms Responsible for Alternative Splicing Affecting Gastrointestinal Nematodes Resistance in Grazing Sheep

Abstract Sheep infected with gastrointestinal nematodes (GIN) can show weight loss, anemia, diarrhea, decrease appetite, and hypoproteinemia, which can sometimes lead to death. These signs of infection decrease productivity and cause economic losses. Economic losses can also be associated with treatment without efficacy due to GIN resistance to most anthelmintic classes. Combined approaches need to be used to reduce the reliance on anthelmintic as the only control method to GIN. The aim of this study is the identification of potential functional single nucleotide polymorphisms (SNPs) responsible for alternate splicing in Rideau X Dorset crossbred sheep with different immune profiles using RNA-Sequencing (RNA-Seq). Animals were exposed to GIN while grazing, after that those with the greatest and least gastrointestinal tract parasite burdens were selected for liver RNA extracting. These animals can be separated into groups of high (H; n = 5) and medium (M; n = 6) innate immune responses. In addition, liver RNA was extracted for GIN-unexposed control lambs (U; n = 4). RNA-Seq analysis was performed using the CLC genomics workbench software, version 20.0.4 (CLC Bio, Aarhus, Denmark). Quality control analyses, including guanine-cytosine (GC) content, ambiguous base content, Phred score, base coverage, nucleotide contributions, and over-represented sequences parameters, were performed on fastq files. Sequence reads were aligned to the annotated Oar_rambouillet_v.1 (release 109) ovine reference genome. After filtering steps, mRNA isoforms with multiple (³ 2) expressed mRNA isoforms with at least one mRNA isoform differently expressed (DE) between H- and M-innate immune response and GIN-unexposed control groups (FDR &amp;lt; 0.05 and |FC| &amp;gt; 2) were keep. A total of 1, 75, and 58 DE mRNA isoforms were identified for M versus H, U versus M, and U versus H comparisons, respectively. Gene ontology (GO) analysis including the biological process, molecular function, and cellular component GO categories and metabolic pathways analysis were performed using STRING-db software. Enriched biological processes and metabolic pathways related to the immune system, as well as cholesterol and other sterol metabolism (e.g., sterol biosynthesis, steroid metabolism, cholesterol biosynthesis, cholesterol metabolism, ascorbate and aldarate metabolism, drug metabolism, and terpenoid biosynthesis) were identified (FDR &amp;lt; 0.05). Next, the list of DE mRNA isoforms identified will be deeply studied by performing SNP discovery analysis to validate if specific functional SNPs are responsible for the alternative splicing affecting GIN resistance in grazing sheep. The complete results will help to better understand the biological mechanisms that may be regulating the immune response to GIN. Candidate functional SNPs have the potential to be included in a commercial SNP panel for selection of more resistant animals to improve GIN resistance in sheep flocks.

Dose confirmation of a novel fixed dose combination injectable (0.2 mg/kg doramectin + 6.0 mg/kg levamisole hydrochloride) against naturally acquired gastrointestinal nematodes in US cattle

Macrocyclic lactone (ML) resistance in cattle gastrointestinal nematodes (GINs) is an increasing problem. Concurrent combination anthelmintic therapy incorporating an existing ML with a second drug class has been proposed to control cattle GINs while slowing the development of ML resistance. Two dose confirmation studies were conducted to investigate the efficacy of a new fixed-dose combination injectable (FDCI) anthelmintic against common cattle GINs known to negatively impact production. The FDCI is formulated with 5 mg/ml doramectin and 150 mg/ml levamisole hydrochloride (HCl). Cattle enrolled in the two studies were sourced from either the Southern (Study 1, n = 30) or Midwest (Study 2, n = 36) United States. Animals with GIN infections confirmed by fecal egg count (FEC) were randomly allocated to one of three treatment groups. On Day 0, cattle with positive FECs on Day −5( ± 2) were weighed and administered a single subcutaneous injection of either saline (0.9% sodium chloride) at 0.04 ml/kg, 10 mg/ml doramectin at 0.02 ml/kg (to provide 0.2 mg/kg doramectin) or the FDCI at 0.04 ml/kg (to provide 0.2 mg/kg doramectin and 6.0 mg/kg levamisole HCl). On Day 14, fecal samples were collected, animals were euthanized, and worms were collected from the intestinal tract of each animal. Treatment efficacy was calculated using worm burdens and the fecal egg count reduction test (FECRT). Pre-treatment (Day −5, Study 1; Day −3, Study 2) mean FECs were 999.4–1136.2 eggs per gram (EPG) in Study 1 and 137.1–226.6 EPG in Study 2. The FDCI was active against cattle GIN populations in both studies, with FECRT ≥ 99.98% in both studies. Compared to saline-treated cattle, FDCI-treated cattle had significantly fewer adult and immature worms of all identified species on Day 14. In Study 1, Day 14 efficacy of the FDCI was 96.9% for Cooperia spp. (C. oncophora (99.7%) and C. punctata (95.9%)), 99.1% for Nematodirus helvetianus, and 99.8% for Ostertagia spp. In Study 2, the FDCI provided 100% efficacy against all adult GIN species identified, including all GINs identified in Study 1 and Trichostrongylus axei. The FDCI also provided 95.5% efficacy against immature Ostertagia spp. and 100% efficacy against immature Cooperia spp. (Study 2). Doramectin was effective against all adult cattle GINs (except N. helvetianus) in Study 2 but was only effective against adult Ostertagia spp. in Study 1. Additionally, doramectin was only effective against immature Cooperia spp. (and not immature Ostertagia spp.) in Study 2. A single administration of the doramectin + levamisole HCl FDCI provides a new and effective approach to the treatment and control of common cattle GINs, including those exhibiting decreased susceptibility to doramectin alone.

Anthelmintic Resistance of Gastrointestinal Nematodes of Communally-Grazing Goats in Humbo District, Southern Ethiopia.

Anthelmintic resistance (AR) in gastrointestinal nematodes (GINs) is currently present worldwide and a major challenge to goat production. However, no updated information is available on this topic in the study area. Thus, this study evaluated the efficacy of commonly used anthelmintics on GINs in naturally-infected goats and assessed farmers' perception of anthelmintic utilization practices in Humbo district, Southern Ethiopia. The field experiments for routinely used anthelmintics, namely, albendazole, ivermectin, and tetramisole, were conducted from September 2022 to April 2023. Sixty naturally-infected goats with nematodes were selected based on egg count (≥150 eggs per gram of feces) and allocated randomly into four groups (15 animals per group). Then, fecal samples were collected pre- and post-treatment and examined for fecal egg count reduction (FECRT) to determine the AR status of goat GINs. The modified McMaster technique using standard floatation was used for quantifying the eggs. In addition, a questionnaire survey was conducted to assess anthelmintic utilization practices among goat owners. The FECR levels for albendazole, ivermectin, and tetramisole were 94.6, 95.9, and 97.3%, respectively. By coproculture, the nematode genera identified before treatment were Haemonchus, Trichostrongylus, Teladorsagia, Oesophagostomum, Bunostomum, and Chabertia Species. However, post-treatment fecal cultures showed that some Haemonchus, Trichostrongylus, and Strongyloides spp. did not respond to the treatments. The questionnaire survey revealed that albendazole was the most commonly used anthelmintic to treat nematode infection in goats. Respondents expressed that anthelmintic treatment was utilized based on veterinarian prescription (59%), availability (32%), efficacy (4%), and affordability (5%). Tetramisole should be used cautiously to prevent the development of resistant strains, as it was still effective in the study area. Additionally, regular monitoring of anthelmintic effectiveness is necessary.

Weighted single-step genome-wide association study and functional enrichment analyses for gastrointestinal nematode resistance traits in Santa Ines sheep

This study aimed to identify genomic regions, pathways, and putative candidate genes associated with resistance to gastrointestinal nematode in Santa Ines sheep. The phenotypic information comprised 5529 records from 1703 naturally infected animals. After genomic data quality control, 37,511 SNPs from 589 animals were available. The weighted single-step approach for genome-wide association study was performed to estimate the SNP effects and variances accounted by 10–SNP sliding windows. Confirming the polygenic nature of the studied traits, 20, 22, 21, and 19 genomic windows that explained more than 0.5% of the additive genetic variance were identified for fecal egg counts (FEC), Famacha© (FAM), packed cell volume (PCV), and total plasma protein (TPP), respectively. A total of 81, 122, 106, and 101 protein-coding genes were found in windows associated with FEC, FAM, PCV, and TPP, respectively. Several protein‐coding genes related to the immune system and inflammatory response functions were identified within those genomic regions, such as ADCY9, ADRB2, BRAF, CADM1, CCL20, CD70, CREBBP, FNBP1, HTR4, IL16, IL22, IL26, MAPK8, NDFIP1, NLRC3, PAK5, PLCB1, PLCB4, ROCK1, TEK, TNFRSF12A, and VAV1. Functional enrichment analysis by DAVID tool also revealed many significant (P < 0.05) pathways and Gene Ontology terms that could be related to resistance to gastrointestinal nematode in Santa Ines sheep, such as chemokine signaling pathway (oas04062), cAMP signaling pathway (oas04024), cGMP-PKG signaling pathway (Oas04022), platelet activation (Oas04611), Rap1 signaling pathway (oas04015), and oxidoreductase activity, acting on paired donors, with incorporation or reduction of molecular oxygen (GO:0016705). These results contribute to improving the knowledge of the genetic architecture of resistance to gastrointestinal nematode in Santa Ines sheep.

Seasonal Prevalence and Status of Anthelmintic Resistance of Goats' Gastrointestinal Nematodes, Mirab Abaya, Southern Ethiopia.

Goats are an important source of livelihood especially for smallholder communities. But gastrointestinal nematodosis is the greatest threats of goat production. A repeated cross-sectional and field experimental study design was conducted from December 2020 to August 2021 in Mirab Abaya district, with the aim of seasonal prevalence gastrointestinal nematode infection and assessment of anthelmintic resistance. A systematic random sampling strategy was used to select the study goats. The overall prevalence of gastrointestinal nematode infections of goats in the study area was 57.9% (95% CI: 54.4-61.4), of which 48.7% (95% CI: 43.7-53.7) and 67.2% (95% CI: 62.3-71.7) accounted to dry and wet seasons, respectively. The multivariable logistic regression analysis showed that season, age, sex, and flock size were significantly (p < 0.05) influenced the prevalence of gastrointestinal nematode infection of goats. The number of eggs per gram of faeces (EPG) was ranged from 100 to 2500. The overall mean egg per gram of faeces (EPG) was 461.1 ± 20.9. The mean EPG of wet season (532.7 ± 28.6) was higher than the dry season (362.3 ± 29.1). From faecal culture, 552 nematode larvae were recovered, and the most commonly identified nematode genera were Haemonchus (36.4%) that followed by Trichostrongylus (28.1%), Oesophagostomum (15.4%), Bunostomum (11.4), Teladorsagia (5.4%), and Strongyloides (3.0%) species. From the anthelmintic resistance test in the field, the percentage reduction and 95% confidence limit of albendazole were 96% (84.2-99.0) and 97.0% (84.6-99.4) in dry and wet seasons, respectively. Here, the lower limit of 95% CI was less than 90% both in dry and wet seasons; and hence, albendazole was suspected for resistance development by gastrointestinal nematode. From a pooled faecal culture that collected from albendazole-treated goats, Haemonchus species was recovered. Therefore, due attention shall be by animal health professionals in the area in the use of albendazole. Animal health extension work to create awareness of how anthelmintic is used is helpful in reducing the risk. Changing the type of anthelmintic drug after using for some period will minimize the risk of anthelmintic resistance development.

Evidence of resistance to ivermectin in the gastrointestinal nematodes of horses from Mexican southeast.

Gastrointestinal nematodes (GIN) are a major impediment to breeding and exploitation of horses. Traditional control of GIN has generated resistance to main anthelmintics, including ivermectin. An analysis of five ranches with a history of IVM use was done to determine the efficacy and resistance of GIN to IVM treatment in horses from the Mexican southeast. Predesigned questionnaires were applied to collect information on previous treatment protocols. The fecal egg count reduction test (FECRT) was applied to determine resistance. Before IVM application, a McMaster test was used to diagnose GIN infection in horses, and feces cultures were done to identify L3 larvae for Strongylida eggs. Pre-treatment samples showed that 72.7% (80/110) of horses were GIN positive, with cyathostomins being the most frequent (91.8%), followed by Oxyuris equi (7.0%), Parascaris equorum (1.0%), and Strongylus vulgaris (0.2%). Based on the results, the horses at each ranch were divided in control (CG) and experimental (EG) groups with similar eggs per gram of feces (EPG). The EG (40/80) was dewormed with IVM (0.2mg/kg orally) and the CG (40/80) remained untreated. After 14days, EPG were measured, and feces cultures were done again to identify L3 larvae. After treatment of EG, 40% (16/40) of horses were positive, the most frequently identified GIN were cyathostomins (98.6%), followed by P. equorum (1.0%) and S. vulgaris (0.2%). Three of the five ranches were classified as resistant, according to the FECRT, with a percentage of reduction from 53 to 68%, all of which used IVM ≥4 times annually. This is the first evidence of resistance in cyathostomins to IVM treatment in horses from the Mexican southeast, adding to the current problem of anthelmintic resistance in equine GIN.

Exploitation of Host Resistance: A Promising Alternative Approach to Control Gastrointestinal Nematodoses in Small Ruminant: A Review

Gastrointestinal nematodes (GINs) are the most insidious pathogens causing severe economic losses to the livestock industry. Among GINs Haemonchus contortus is the most pathogenic and predominant parasite of small ruminant livestock. Although the use of chemical anthelmintics is still the corner-stone of control method for GINs, the increasing rate of prevalence of anthelmintic resistance has made it less reliable control option. Anthelmintic resistance together with global demands for chemical residue free animal product has led to search for alternative sustainable control strategies which rely less on chemical anthelmintics. One of such strategy is the exploitation of host resistance against the GINs including H. contortus. The resistance of animals to GINs varies within and between breeds of sheep and goats. Host immune response plays an important role in host resistance but the immune mechanisms responsible for resistance are not fully known. Studies on identification of gene/(s) responsible for host resistance are also being carried out to find out the molecular mechanism of GINs resistance in sheep and goats all over the world. Selective breeding for GINs resistance is the ultimate solution for the problems of anthelmintic resistance. This article reviews the published reports on GINs resistance in relation to immunological response and genetic studies in small ruminants and discusses the prospects for selective breeding of GINs resistance in sheep and goat.

Therapeutic advantages of the combined use of closantel and moxidectin in lambs parasitized with resistant gastrointestinal nematodes

The serious widespread development of nematode resistance has motivated the use of combined anthelmintic formulations. However, the advantages/disadvantages of the combined use of anthelmintics require further scientific characterization. The goals of the current trial were a) to characterize the pharmacokinetics of closantel (CLO) and moxidectin (MXD) administered both subcutaneously (sc) and orally either separately or co-administered (CLO + MXD) to lambs; b) to compare the nematodicidal activity of both molecules given individually or co-administered to lambs infected with resistant nematodes. Seventy (70) Corriedale lambs naturally infected with multiple resistant gastrointestinal nematodes were involved in the pharmacokinetic and efficacy trials. The animals were allocated into six groups (n = 10) and treated with either CLO, MXD, or with the CLO + MXD combined formulation by both the oral and sc routes. Additionally, an untreated control group (n = 10) was included for the efficacy trial. The efficacy was estimated by the faecal egg count reduction test (FECRT). Higher systemic exposure of both CLO and MXD was observed after the sc compared to the oral administration in lambs. The combined administration of CLO + MXD did not markedly alter their disposition kinetics. At 13 days post-treatment, the administration of both molecules as a single active principle reached efficacy levels ranging between 80% (MXDoral), 84% (CLOoral), 85% (CLOsc), and 92% (MXDsc). The combined oral and sc treatments reached 99% efficacy. No adverse effects were observed after the combined treatment of CLO + MXD, and their co-administration did not show any adverse pharmacokinetic interaction. The combined effect of CLO + MXD successfully restored the maximum efficacy levels, which were not reached by the individual active ingredients.

Efficacy in US cattle of a novel fixed-dose combination injectable (0.2 mg/kg doramectin + 6.0 mg/kg levamisole hydrochloride) against naturally acquired gastrointestinal nematode infections

Reports of macrocyclic lactone (ML) loss of efficacy suggest ML resistance in gastrointestinal nematodes (GINs) is a growing problem in the US cattle industry. Empirical and modeling data support combining an ML and second anthelmintic from a different drug class to help ML resistance development while effectively treating existing resistant parasite populations. Here, we present a novel fixed-dose combination injectable (FDCI) solution for cattle that delivers 0.2 mg of doramectin and 6.0 mg of levamisole hydrochloride (HCl) per kg of body weight. Field studies were conducted at six sites across the Midwest United States to investigate the efficacy of a single administration of the FDCI in treating common cattle GINs. Cattle (n = 425) with GIN infections confirmed by fecal egg count (FEC) on Day −10( ± 2) were randomly allocated to the control (saline) or treatment (FDCI) group. On Day 0, pre-treatment fecal samples were collected, and cattle were administered a single subcutaneous injection of saline (n = 106) or FDCI (n = 319). Post-treatment fecal samples were collected on Day 14. Fecal egg count reduction tests (FECRTs) were conducted using Day 0 and Day 14 FECs. Efficacy was evaluated using Day 14 FECs (FDCI-treated versus saline-treated). Within treatment, samples collected on Days 0 and 14 with ≥ 20 eggs per gram (EPG) were cultured for nematode larvae recovery and identification. Day −10 FECs for enrolled animals were similar between treatment groups. Coprocultures from cattle with FEC ≥ 20 EPG (n = 68 saline; n = 211, FDCI) on Day 0 showed the presence of Cooperia punctata, Ostertagia spp., Haemonchus spp., C. oncophora, Oesophagostomum spp. and Trichostrongylus spp. Day 14 FECs for FDCI-treated cattle were significantly reduced (0–3 EPG) compared to saline-treated cattle (0–1252 EPG) (p ≤ 0.0042). At all study sites, the efficacy of the new FDCI was ≥ 99.4% and the FECR was 0.99 or 1.00. Day 14 coprocultures from control cattle showed infections of common GIN genera, confirming the efficacy of the FDCI against GINs in the field. A single administration of the doramectin + levamisole HCl combination injectable effectively treats common and economically important cattle GINs.

Genome-Wide Analysis of Sheep Artificially or Naturally Infected with Gastrointestinal Nematodes.

The anthelmintic resistance of gastrointestinal nematodes (GINs) poses a significant threat to sheep worldwide, but genomic selection can serve as an alternative to the use of chemical treatment as a solution for parasitic infection. The objective of this study is to conduct genome-wide association studies (GWASs) to identify single nucleotide polymorphisms (SNPs) in Rambouillet (RA) and Dorper × White Dorper (DWD) lambs associated with the biological response to a GIN infection. All lambs were genotyped with a medium-density genomic panel with 40,598 markers used for analysis. Separate GWASs were conducted using fecal egg counts (FECs) from lambs (<1 year of age) that acquired their artificial infections via an oral inoculation of 10,000 Haemonchus contortus larvae (n = 145) or naturally while grazing on pasture (n = 184). A GWAS was also performed for packed cell volume (PCV) in artificially GIN-challenged lambs. A total of 26 SNPs exceeded significance and 21 SNPs were in or within 20 kb of genes such as SCUBE1, GALNT6, IGF1R, CAPZB and PTK2B. The ontology analysis of candidate genes signifies the importance of immune cell development, mucin production and cellular signaling for coagulation and wound healing following epithelial damage in the abomasal gastric pits via H. contortus during GIN infection in lambs. These results add to a growing body of the literature that promotes the use of genomic selection for increased sheep resistance to GINs.

Evaluation of a refugia-based strategy for gastrointestinal nematodes on weight gain and fecal egg counts in naturally infected stocker calves administered combination anthelmintics

Refugia-based strategies associated with a combination of anthelmintic drugs belonging to different drug classes are becoming more common management practices to mitigate anthelmintic resistance (AR) in gastrointestinal nematodes (GIN) in small ruminants. Though refugia-based strategies have been largely demonstrated in small ruminants, cattle veterinarians and producers are considering such management strategies in grazing cattle production systems. Implementing refugia-based strategies lowers the amount of anthelmintics used in the herd and therefore slows the progression of AR by allowing a proportion of worms to escape drug selection pressure. The objective of this study was to observe the effect of a refugia-based strategy on body weight (BW), average daily gain (ADG) and fecal egg counts (FEC) of trichostongyle-type nematodes in naturally infected beef calves over a 131-day grazing season when compared with a whole herd treatment strategy, using the same combination of drugs. Stocker calves (n = 160) were ranked by body weight within sex then allocated to 16 paddocks, which were randomly assigned to one of two treatment groups. All calves in Group 1 (n = 80) were administered treatment, while in Group 2 (n = 80) the steer with the highest FEC in eggs per gram (EPG) within the paddock was left untreated. Treated calves received an extended release injectable 5 % eprinomectin (LongRange®, Boehringer Ingelheim Animal Health USA Inc.; 1 mL/50 kg of BW) and a 22.5 % oxfendazole oral suspension (Synanthic®, Boehringer Ingelheim Animal Health USA Inc.; 1 mL/50 kg of BW). Fecal egg counts and BW were recorded on days (D) −35, 0, 21, 131, and 148 to calculate the average fecal egg count reduction (FECR) and ADG for both groups. Linear mixed models, with paddock as the experimental unit, were used for analyses. The EPG differed on D21 (p < 0.01) and D131 (p = 0.057) with Group 2 having a higher average FEC (15.2 EPG D21; 57 EPG D131) compared with Group 1 (0.4 EPG D21; 37.25 EPG D131). However, there was no significant difference in average BW or ADG between treatment groups throughout the study. Results suggest refugia-based strategies could be implemented without significant negative impacts on average BW and ADG across other calves in the herd.