Identification of third stage larvae of strongyles and molecular diagnosis of Strongylus vulgaris in the feces of Thoroughbred horses kept in training centers in Rio de Janeiro, Brazil.

The aims of the present study were to identify strongyles in the feces of Thoroughbred horses based on larval morphology; to detect Strongylus vulgaris using molecular diagnosis and compare results to those of feces culture; and to determine the association between the presence of S. vulgaris with corresponding animal information (age range, gender, and anthelmintic use). Feces of horses kept in six Training Centers in Rio de Janeiro State, that showed the presence of ≥500 eggs per gram of feces (EPG) were subjected to strongyle identification. Of the 520 fecal samples collected, 35 had an EPG ≥ 500. After fecal culture for L3 larvae identification, DNA was extracted, subjected to PCR to amplify the ITS2 region DNA fragment of S. vulgaris, and sequenced. A total of 3500 larvae were analyzed. Most were classified as small strong (99.7%), with an emphasis on the type A subfamily of Cyathostominae. Forms of S. vulgaris only corresponded to 0.2%. In all, 25 samples showed amplified S. vulgaris DNA products and 11 showed nucleotide sequences with high sequence identity. Fecal culture and PCR results showed poor agreement (kappa = 0.105) for S. vulgaris diagnosis. Age, gender, anthelmintic use, and anthelmintic administration interval were not statistically significant. The present study showed the presence of S. vulgaris in the feces of horses kept in Rio de Janeiro Training Centers, mainly seen via PCR, which has emerged as the most effective tool for diagnosis. This study made it possible to identify strongyles that infect horses in the region, emphasizing upon the necessity for constant monitoring of the animals.

Machine learning prediction of multiple anthelmintic resistance and gastrointestinal nematode control in sheep flocks.

The high prevalence of Haemonchus contortus and its anthelmintic resistance have affected sheep production worldwide. Machine learning approaches are able to investigate the complex relationships among the factors involved in resistance. Classification trees were built to predict multidrug resistance from 36 management practices in 27 sheep flocks. Resistance to five anthelmintics was assessed using a fecal egg count reduction test (FECRT), and 20 flocks with FECRT < 80% for four or five anthelmintics were considered resistant. The data were randomly split into training (75%) and test (25%) sets, resampled 1,000 times, and the classification trees were generated for the training data. Of the 1,000 trees, 24 (2.4%) showed 100% accuracy, sensitivity, and specificity in predicting a flock as resistant or susceptible for the test data. Forage species was a split common to all 24 trees, and the most frequent trees (12/24) were split by forage species, grazing pasture area, and fecal examination. The farming system, Suffolk sheep breed, and anthelmintic choice criteria were practices highlighted in the other trees. These management practices can be used to predict the anthelmintic resistance status and guide measures for gastrointestinal nematode control in sheep flocks.

Anthelmintic efficacy of nitazoxanide in dogs naturally infected with Toxocara canis.

Toxocara canis (T. canis) is a gastrointestinal nematode in dogs, and its larvae also infect humans, causing severe larval migratory disease. Anthelmintic drugs have become the primary means to combat T. canis. In this study, the efficacy of nitazoxanide (NTZ) was tested against all the internal stages of T. canis, including L3 larval stage in vitro experiments and gastrointestinal worm in vivo experiments. In the in vitro experiment, after treatment with NTZ at 7.81 and 62.5 µg/mL for 12 h, the larval mortality efficacy reached 90.0 and 100.0%, respectively. In the in vivo experiments, 100 mg/kg NTZ possessed good anthelmintic efficacy against T. canis, with an egg per gram (EPG) reduction of 99.19%, and 90.00% of dogs cleared with residual worms. These results were comparable to those of the positive control drug. The highest anthelmintic efficacy was observed in the group treated with 150 mg/kg NTZ. Based on faecal egg counts, the number of T. canis eggs decreased by 100.00%, and the percentage of dogs cleared with residual worms achieved 90.00% after 7 days of treatment in the 150-mg/kg NTZ treatment group. In general, NTZ showed great potential to be applied as an anthelmintic against T. canis.

Revisiting anthelmintic resistance in sheep flocks from São Paulo State, Brazil.

Haemonchus contortus and Trichostrongylus colubriformis are the most important gastrointestinal nematodes causing serious losses in sheep production of tropical and subtropical regions. Prophylaxis of gastrointestinal nematode infections is based on anthelmintics use, but their frequent administration selects multiple-resistant parasites. To evaluate how the situation has changed over the last decades, the anthelmintic resistance status of gastrointestinal nematodes in sheep flocks was assessed in the current study and compared to previous surveys. In each one of the 15 flocks evaluated, animals (n ≥ 7) were allocated into at least five groups and treated as follows: 1) untreated control; 2) albendazole; 3) levamisole; 4) ivermectin; and 5) monepantel. If more animals were available, two additional groups were included: 6) closantel, and 7) moxidectin. The faecal egg count reduction test (FECRT) was carried out to evaluate the pre- and post-treatment using the SHINY tool. Haemonchus spp. was the most prevalent nematode from faecal cultures. The mean efficacy of albendazole was 40%. Only in two farms, levamisole presented a relatively high percentage of reduction in the FECRT about 90%, while ivermectin and moxidectin presented the worst mean efficacy of 34% and 21% among all farms, respectively. Like other anthelmintics, closantel demonstrated low efficacy (63%) across all farms evaluated. Monepantel presented an overall mean efficacy of 79%, but it was the only anthelmintic that presented efficacy ≥95%, in five farms. The results revealed that gastrointestinal nematodes with multiple anthelmintic resistance were prevalent in all 15 sheep herds. The research suggests that nematodes are becoming more and more resistant to various anthelmintic compounds, which has made the problem worse. This circumstance highlights the necessity to put into practice sustainable and long-lasting methods to prevent gastrointestinal nematode infections in sheep husbandry.

Epidemiology and field efficacy of anthelmintic drugs associated with gastrointestinal nematodes of sheep in Nejo district, Oromia, Ethiopia.

Gastrointestinal nematodes (GINs) are major constraints to health and productivity of small ruminants. Methods of their control relies mainly on anthelmintic drugs; however, the indiscriminate use of these drugs could lead to the development of anthelmintic resistance (AR). This study aimed to investigate the epidemiology of GINs infection, and field evaluation of anthelmintic efficacy in sheep. The epidemiological data were collected using a cross-sectional study design while a farm-based field study design was employed for the evaluation of anthelminthic efficacy. Furthermore, standard parasitological techniques were employed for qualitative and quantitative worm identification. The overall prevalence indicated 50.3%. Six genera of GINs (Haemonchus, Trichostrongylus, Oesophagostomum/Chabertia, Trichuris, Teladosargia/Ostertagia and Nematodirus) were identified. Among the identified genera, Haemonchus (25.4%) and Trichostrongylus (24.8%) were the dominant genera followed by mixed infection (21.8%), Oesophagostomum/Chabertia (10.4%), Trichuris (7.8%), Teladosargia (Ostertagia) (5.7%) and Nematodirus (4.1%). Mixed infections consisted either of double infections with Haemonchus and Trichostrongylus, or triple infections with Haemonchus, Trichostrongylus and Trichuris. The McMaster egg counting results showed that the mean EPG of infected sheep was 845.6. The results also showed 66 (34.2%), 101 (52.3%) and 26 (13.5%) sheep had low, moderate and heavy worm burden, respectively. Albendazole and Ivermectin showed low efficacy (percentage reductions = 90% and 92%; 95% lower confidence limit = 82.1% and 83.6% respectively) whereas Tetramisole was effective (FECR% = 96.8%; 95% LCL = 93.4%). Factors such as age, body condition, management system and past deworming history of sheep were found to have a statistically significant (p < 0.05) influence on the occurrence and burden of the worms. This is further explained as the highest prevalence and worm burden was detected in sheep of young age (p = 0.008; OR = 0.58; 95% CI = 0.39-0.87), poor body condition (p = 0.001; OR = 0.08; 95% CI = 0.04-0.16) and sheep kept under semi-intensive (p = 0.04; OR = 1.53; 95% CI = 1.02-2.29) with no deworming history for the last two months (p = 0.001; OR = 2.97; 95% CI = 1.94-4.56). The study results revealed that nematode infections were among sheep health constraints that could hurt their productivity while low efficacy of Albendazole and Ivermectin were detected. Therefore, the appropriate management techniques of GIN infections should be designed and implemented. Moreover, a further study involving more sensitive techniques (e.g. Mini-FLOTAC, molecular, and serological techniques) should be conducted by considering different host and environmental risk factors such as production level and seasons.

Performance of three techniques for diagnosing equine tapeworm infection.

Tapeworm infection in horses can cause serious health concerns, and recent data have documented treatment failures in the most common species, Anoplocephala perfoliata. The threat of anthelmintic resistance in A. perfoliata is of particular concern because of poor diagnostic performance of standard egg counting techniques for detecting this parasite. This study compared the performance of three diagnostic techniques 1) Mini-FLOTAC, 2) Cornell-Wisconsin, and 3) Proudman and Edwards used to detect and quantify A. perfoliata eggs in naturally infected horses. Eighteen adult female horses from the University of Kentucky's historic parasitology herd were included in this study. Fecal samples were collected from all horses at five collection time points two weeks apart and analyzed with the three techniques. A total of 90 samples were collected and 270 counts determined in the study. The proportions of positive samples determined by the three techniques were significantly different from each other (p<0.05): Mini-FLOTAC (16%), Cornell-Wisconsin (47%), and Proudman and Edwards (70%). The Proudman and Edwards technique counted consistently higher numbers of tapeworm eggs compared to the other two techniques throughout the study [p < 0.05]. Total raw counts of tapeworm eggs across the study for each technique were 16, 88, and 410 for the Mini-FLOTAC, Cornell-Wisconsin, and Proudman and Edwards, respectively. This study demonstrated that the Proudman and Edwards technique was superior in diagnosing A. perfoliata infection. Future work needs to assess this technique's potential for Fecal Egg Count Reduction Testing (FECRT).

The first report of triple anthelmintic resistance on a French Thoroughbred stud farm.

This study assessed the anthelmintic resistance in strongylid nematodes against commonly used anthelmintic (AH) drugs in a French galloping racehorse stud farm from March to December 2023. Faecal egg count reduction tests (FECRTs) were conducted in three different groups of Thoroughbred yearlings (a group of 6 males, a group of 13 females and a group of 8 females and 3 males) following the new World Association for the Advancement of Veterinary Parasitology (WAAVP) guidelines. The efficacy of fenbendazole was tested in two groups once during the monitoring period (in March), the efficacy of ivermectin in 3 groups twice (in March-April and in November-December) and the efficacy of pyrantel in one group once (in May-June). For each FECRT, the 90% confidence interval of the percentage faecal egg count reduction was calculated using the hybrid Frequentist/Bayesian analysis method. The resistance in strongylids was observed to fenbendazole, pyrantel and ivermectin in all the groups in which these drugs were tested. The number of animals in each group was sufficient to reach ≥80% power for the resistance test. The results highlight the first case of triple AH resistance in strongylids in France. Further studies involving more farms and equids are required to assess the prevalence of AH resistance in France and refine recommendations for owners.

Chicory (Cichorium intybus) reduces cyathostomin egg excretion and larval development in grazing horses.

Cyathostomins are the most prevalent parasitic nematodes of grazing horses. They are responsible for colic and diarrhea in their hosts. After several decades of exposure to synthetic anthelmintics, they have evolved to become resistant to most compounds. In addition, the drug-associated environmental side-effects question their use in the field. Alternative control strategies, like bioactive forages, are needed to face these challenges. Among these, chicory (Cichorium intybus, Puna II cultivar (cv.)) is known to convey anthelmintic compounds and may control cyathostomins in grazing horses. To challenge this hypothesis, we measured fecal egg counts and the rate of larval development in 20 naturally infected young saddle horses (2-year-old) grazing either (i) a pasture sown with chicory (n = 10) or (ii) a mesophile grassland (n = 10) at the same stocking rate (2.4 livestock unit (LU)/ha). The grazing period lasted 45 days to prevent horse reinfection. Horses in the chicory group mostly grazed chicory (89% of the bites), while those of the control group grazed mainly grasses (73%). Cyathostomins egg excretion decreased in both groups throughout the experiment. Accounting for this trajectory, the fecal egg count reduction (FECR) measured in individuals grazing chicory relative to control individuals increased from 72.9% at day 16 to 85.5% at the end of the study. In addition, larval development in feces from horses grazed on chicory was reduced by more than 60% from d31 compared to control individuals. Using a metabarcoding approach, we also evidenced a significant decrease in cyathostomin species abundance in horses grazing chicory. Chicory extract enriched in sesquiterpenes lactones was tested on two cyathostomins isolates. The estimated IC50 was high (1 and 3.4 mg/ml) and varied according to the pyrantel sensitivity status of the worm isolate. We conclude that the grazing of chicory (cv. Puna II) by horses is a promising strategy for reducing cyathostomin egg excretion and larval development that may contribute to lower the reliance on synthetic anthelmintics. The underpinning modes of action remain to be explored further.

Ecology of the free-living stages of cattle nematodes in the dry season in the Lerma Valley, Salta province, Argentina.

The objective of this work was to describe the dynamics of development and survival of the free-living stages of cattle gastrointestinal nematodes (GIN) in fecal matter (FM) and pasture during the dry season in the Lerma Valley, Salta province, northwestern Argentina (NWA) to contribute to GIN management. The climate in the region is characterized by a rainy summer followed by a dry season from middle autumn to early spring. Fecal matter from calves naturally infected with GIN was deposited on three experimental field plots in April, July and October 2019, corresponding to the beginning, middle and end of the dry season, respectively. Each experimental unit consisted of 7 stools of about 800 g and had four repetitions. To determine the development from egg to infective larvae (L3), the first sampling (5 g fecal matter) was performed from the 10th day post-contamination and continued every 3 days until L3 were found. Subsequently, a monthly sampling was made until two consecutive negative results were obtained. Sampling of pasture began three days after the L3 recovery from FM, and continued monthly until two negative results were obtained. The following parameters were evaluated: development time and development rate from egg to L3; permanence time of L3 in feces; time of appearance on pasture; migration rate; and permanence time of L3 on pasture. The main genera of parasites present were Cooperia and Haemonchus. Significant differences were observed in the development time among contamination months (p < 0.001); development time was highest in the July contamination (28 days), with October and April contamination averaging 9 and 10 days, respectively. Development time also showed significant differences (p < 0.01) among contamination months, being highest in October (31.48%). The highest permanence time in fecal matter values were recorded in the July contamination (183 days) and migration rate was highest in the October contamination (42.49%). The highest time of appearance on pasture value was recorded in the July contamination (117 days). Finally, the highest permanence time of L3 in feces values were detected in the October contamination (148 days). The results of this work show that fecal contamination in the NWA region in the dry season would play an epidemiological role in the GIN cycle as a source of infection for the next productive cycle in the rainy season.

Revealing the associated microflora hosted by the globally significant parasite Trichostrongylus colubriformis.

Trichostrongylus colubriformis is a parasitic helminth that primarily infects small ruminants, causing substantial economic losses in the livestock industry. Exploring the microbiome of this helminth might provide insights into the potential influence of its microbial community on the parasite's survival. We characterised the intestinal microbiome of T. colubriformis that had been collected from the duodenum of sheep, and compared the helminth microbiome with the duodenal microbiome of its host, aiming to identify contributions from the helminth's environment. At the same time, we explored the isolation of fastidious organisms from the harvested helminth. Primary alpha and beta diversity analyses of bacterial species revealed statistically significant differences between the parasite and the host, in terms of species richness and ecological composition. 16S rRNA differential abundance analysis showed that Mycoplasmoides and Stenotrophomonas were significantly present in T. colubriformis but not in the duodenal microbiome of the sheep. Furthermore, two bacteria, Aeromonas caviae and Aeromonas hydrophila, were isolated from T. colubriformis. Examinations of the genome highlight differences in genome size and profiles of antimicrobial resistance genes. Our results suggest that T. colubriformis carries a specific bacterial community that could be supporting the helminth's long-term survival in the host's digestive system.

Metabarcoding study to reveal the structural community of strongylid nematodes in domesticated horses in Thailand.

BACKGROUND: Mixed strongylid infections significantly impact equine health and performance. Traditional microscopy-based methods exhibit limitations in accurately identifying strongylid species. Nemabiome deep amplicon sequencing approach previously succeeded in describing the strongylid communities in livestock including equids. However, there are no available studies that describe the structural communities of strongylid parasites in horses in Thailand. Therefore, this study was undertaken encompassing the ITS-2 rDNA metabarcoding assay to characterize strongylid species within horse fecal samples collected from a cohort of yearlings at the largest domesticated stud farm in Thailand. In addition, to investigate the capability of ITS-2 rDNA in assessing the phylogenetic relationships among the identified strongylid species. RESULTS: The study identified 14 strongylid species in the examined equine populations, each with varying prevalence. Notably, Cylicocyclus nassatus and Cylicostephanus longibursatus were identified as the predominant species, with Strongylus spp. conspicuously absent. The phylogenetic analysis of 207 amplicon sequence variants (ASVs) displayed a complex relationship among the investigated cyathostomin species, with some species are positioned across multiple clades, demonstrating close associations with various species and genera. CONCLUSION: The ITS-2 nemabiome sequencing technique provided a detailed picture of horse strongylid parasite species in the studied population. This establishes a foundation for future investigations into the resistance status of these parasites and enables efforts to mitigate their impact.

Pyrantel resistance in canine hookworms in Queensland, Australia.

Hookworms are the most common intestinal nematode parasites of dogs in Australia. The control of these parasites relies mostly on regular deworming with anthelmintics, with pyrantel-based dewormers being a relatively low cost and readily-available option for dog owners. Pyrantel resistance in canine hookworms in Australia was first reported in 2007, however pyrantel-based dewormers are still used against hookworm infection in dogs across Australia. The present study was conducted to evaluate the efficacy of pyrantel against hookworms infecting dogs housed in a shelter facility in Southeast Queensland which receives rescued or surrendered animals from greyhound rescue centres and dog shelters across this region. A total of 10 dogs were examined using the faecal egg count reduction test (FECRT). There was no reduction in FEC in any of the dogs following pyrantel treatment, with drug efficacies ranging from -0.9% to -283.3%. Given that these dogs originated from various sites across Southeast Queensland, the present study suggests that pyrantel resistance is widespread in this region, and hence this anthelmintic may not be a useful option for treatment of hookworm infections in dogs.

Faecal egg count reduction test in goats: Zooming in on the genus level.

The faecal egg count reduction test (FECRT) is the most widely used method to assess treatment efficacy against gastrointestinal nematodes (GIN). Information on genera composition of the GIN community is not available with this test and it is commonly obtained by identifying cultured third-stage larvae (L3) or through molecular assays in the post-treatment survey, but results provided are usually only qualitative or semi-quantitative. The updated WAAVP guidelines now recommend assessing anthelmintic efficacy for each GIN genus/species separately (genus-specific FECRT), but this approach is poorly employed in Europe and in goats especially. For this reason, four FECRT trials were conducted using oxfendazole and eprinomectin in two Italian goat farms. Samples were processed individually using the McMaster technique and then pooled to create two samples from faeces of 5 animals each. Pooled samples were analysed using the McMaster and cultured for seven days at 26°C to obtain L3s. The genus-specific FECRT was based on larval identification, integrating coproculture and FEC results. Larvae were identified as Haemonchus, Trichostrongylus, Teladorsagia, Oesophagostomum / Chabertia and Bunostomum. Molecular assays (a multiplex real-time PCR and two end-point PCRs) were also implemented on pooled samples to support the morphological identification. The Spearmann Rho test confirmed a high correlation between the two approaches (Rho = 0.941 and Rho = 0.914 respectively for Haemonchus and Trichostrongylus, the two most common genera). Both oxfendazole and eprinomectin were effective in one farm, while none in the other farm (FECR = 75.9% and 73.3% respectively). In the second farm, the genus-specific FECRT highlighted a different response to treatment among genera: oxfendazole lacked efficacy against both Haemonchus and Trichostrongylus spp., eprinomectin only against Haemonchus, while all other genera were susceptible to both drugs. This study brings new attention on the importance of adopting a genus-specific approach to identify and quantify differences in susceptibility to anthelmintics among genera in goats, providing support for FECRT interpretation, anthelmintic resistance evaluation and evidence-based GIN control.

The proof is in the poo-ding: Benefits of the longitudinal molecular surveillance of drug resistance demonstrated in a New South Wales cattle herd.

Our understanding of anthelmintic resistance in the gastrointestinal nematodes of Australian cattle relies exclusively on small-scale phenotypic reports utilising traditional faecal egg count reduction tests. This approach is not readily scalable to establish the national prevalence of resistance, nor is it conducive of routine longitudinal surveillance for the emergence of resistance in its early stages. This study introduces the benefits of applying mixed amplicon metabarcoding longitudinally for timely and cost-efficient molecular surveillance of multiple anthelmintic resistance mutations, as they emerge on farms. Using opportunistically collected faecal samples from a cattle herd in central west New South Wales (2019-2023), we detected the early emergence of Haemonchus spp. levamisole-resistant S168T shortly after levamisole introduction, while benzimidazole-resistant allele frequencies remained constant. Additionally, we observed the possible spill-over of resistant Haemonchus contortus from sheep, along with variations in faecal burdens and species diversity influenced by climate stochasticity and host immunity. This study emphasises the power of molecular diagnostics for farm-level anthelmintic resistance management, providing essential evidence to support its integration into routine surveillance programmes.

BEVA primary care clinical guidelines: Equine parasite control.

BACKGROUND: There is a lack of consensus on how best to balance our need to minimise the risk of parasite-associated disease in the individual horse, with the need to limit the use of anthelmintics in the population to preserve their efficacy through delaying further development of resistance. OBJECTIVES: To develop evidence-based guidelines utilising a modified GRADE framework. METHODS: A panel of veterinary scientists with relevant expertise and experience was convened. Relevant research questions were identified and developed with associated search terms being defined. Evidence in the veterinary literature was evaluated using the GRADE evidence-to-decision framework. Literature searches were performed utilising CAB abstracts and PubMed. Where there was insufficient evidence to answer the research question the panel developed practical guidance based on their collective knowledge and experience. RESULTS: Search results are presented, and recommendation or practical guidance were made in response to 37 clinically relevant questions relating to the use of anthelmintics in horses. MAIN LIMITATIONS: There was insufficient evidence to answer many of the questions with any degree of certainty and practical guidance frequently had to be based upon extrapolation of relevant information and the panel members' collective experience and opinions. CONCLUSIONS: Equine parasite control practices and current recommendations have a weak evidence base. These guidelines highlight changes in equine parasite control that should be considered to reduce the threat of parasite-associated disease and delay the development of further anthelmintic resistance.

Genome-wide association studies of parasite resistance, productivity and immunology traits in Scottish Blackface sheep.

Gastrointestinal parasitism represents a global problem for grazing ruminants, which can be addressed sustainably by breeding animals to be more resistant against infection by parasites. The aim of this study was to assess the genetic architecture underlying traits associated with gastrointestinal parasite resistance, immunological profile and production in meat sheep, and identify and characterise candidate genes affecting these traits. Data on gastrointestinal parasite infection (faecal egg counts for Strongyles (FECS) and Nematodirus (FECN) and faecal oocyst counts for Coccidia, along with faecal soiling scores (DAG), characterised by the accumulation of faeces around the perineum) and production (live weight (LWT)) were gathered from a flock Scottish Blackface lambs at three and four months of age. Data on the immune profile were also collected from a subset of these lambs at two and five months of age. Immune traits included the production of Interferon-γ (IFN-γ), Interleukin (IL)-4 and IL-10 following stimulation of whole blood with pokeweed mitogen (PWM) or antigen from the gastric parasite Teladorsagia circumcincta (T-ci), and serum levels of T. circumcincta-specific immunoglobulin A (IgA). Animals were genotyped with genome-wide DNA arrays, and a total of 1 766 animals and 45 827 Single Nucleotide Polymorphisms (SNPs) were retained following quality control and imputation. Genome-wide association studies were performed for 24 traits. The effects of individual markers with significant effects were estimated, and the genotypic effect solutions were used to estimate additive and dominance effects, and the proportion of additive genetic variance attributed to each SNP locus. A total of 15 SNPs were associated at least at a suggestive level with FECS, FECN, DAG, IgA, PWM-induced IFN-γ and IL-4, and T-ci-induced IL-10. This study uncovered 52 genes closely related to immune function in proximity to these SNPs. A number of genes encoding C-type lectins and killer cell lectin-like family members were close to a SNP associated with FECN, while several genes encoding IL-1 cytokine family members were found to be associated with IgA. Potential candidate genes belonging to or in close proximity with the Major Histocompatibility Complex (MHC) were revealed, including Homeostatic Iron Regulator and butyrophilin coding genes associated with IFN-γ(PWM), and IL-17 coding genes associated with IgA. Due to the importance of the MHC in the control of immune responses, these genes may play an important role in resistance to parasitic infections. Our results reveal a largely complex and polygenic genetic profile of the studied traits in this Scottish Blackface sheep population.

Gastrointestinal parasite community structure in horses after the introduction of selective anthelmintic treatment strategies.

A relatively new method to study the species richness and diversity of nematode parasites in grazing animals is to perform deep sequencing on composite samples containing a mixture of parasites. In this work, we compared species composition of strongyles in two groups of horses as a function of egg count and age, based on a DNA barcoding approach. Faecal egg counts and larval cultures were obtained from nearly 300 horses, i.e., domestic horses (n = 167) and trotters (n = 130) sampled nationwide. The second internal transcribed spacer region (ITS2) of strongyle nematodes in the larval cultures was first amplified using barcoded universal primers and then sequenced on the PacBio platform. Subsequently, bioinformatic sequence analysis was performed using SCATA to assign operational taxonomic units (OTU). Finally, species occurrence and composition were assessed using R. ITS2 sequences were found in the majority (89%) of larval samples. Sequencing yielded an average of 140 (26 to 503) reads per sample. The OTUs were assigned to 28 different taxa, of which all but three could be identified as species. The average relative abundance of the seven most abundant species (all Cyathostominae) accounted for 87% of the combined data set. The three species with the highest prevalence in both horse groups were Cyathostomum catinatum, Cylicocyclus nassatus and Cylicostephanus calicatus, and they were frequently found in different combinations with other species regardless of horse group. Interestingly, this result is largely consistent with a previous Swedish study based on morphological analysis of adult worms. In addition, two migratory strongylids (Strongylus vulgaris and S. edentatus) occurred in few domestic horses and trotters. Except for C. minutus and C. nassatus, which decreased with age, and C. catinatum and S. vulgaris, which increased, no specific trends were observed with respect to horse age. Taken together, these results are broadly consistent with data obtained before the introduction of selective targeted treatment in Sweden in 2007. All in all, our results suggest that this treatment strategy has not led to a significant change in strongyle nematode community structure in Swedish horses. The study also confirms that nemabiome analysis in combination with diversity index analysis is an objective method to study strongyle communities in horses.

Prevalence and seasonal dynamic of gastrointestinal parasites in equids in France during two years.

Grazing equids are constantly exposed to three clinically important gastrointestinal parasites (small strongyles/cyathostomins, Anoplocephala spp. and Parascaris spp.). Knowledge of the local seasonal dynamic of these parasitic infections is important for constructing a sustainable parasite control program with a rational number of anthelmintic treatments. However, studies describing these patterns are sparse in France. In this context, a two-year study was carried out to assess i) the seasonal dynamic and variability of strongyle faecal egg counts (FEC) and infective larvae (L3) counts on pastures, and ii) the prevalence of Anoplocephala spp. and Parascaris spp. and the dynamic evolution of their presence. During 2021 and 2022 grazing seasons, monthly individual faecal egg counts (FEC) and diarrhea scores (DS) were determined on 428 equids divided into 33 groups. A monthly body condition score (BCS) was also attributed to animals ≥3 years old and a monthly bodyweight was estimated for each animal <3 years old. At the group level, the strongyle L3 counts on grazed pastures were carried out at least in spring, summer and autumn. Eggs of strongyles were observed in 97% of equids. In 64% of the groups, the peaks of FEC were noted in September and October. At the individual level, the maximum strongyle FEC was related to age, group of breeds, number of grazed plots and number of anthelmintic treatments. No negative association was observed between strongyle FEC and BCS or average daily weight gain. In the pastures, cyathostomin larvae were found almost exclusively. Over the two years, the peaks of cyathostomin L3 counts occurred in 87% of the groups between September and November and ranged from 635 to 87,500 L3 kg-1 dry herbage. The variability of the maximum cyathostomin L3 count in each group was explained by the year and the number of grazed plots. Eggs of Anoplocephala spp. were observed in 12% of equids. Eggs of Parascaris spp. were noted in 34% of one year-old animals, 9% of two years-olds and 2% of olders. Anoplocephala spp. and Parascaris spp. eggs were observed every month with a peak in the percentage of shedders in groups in October for Anoplocephala spp. and May-June for Parascaris spp.This study highlights the prevalence of each parasite, the variability in cyathostomin egg excretion and L3 counts amongst groups and individuals and the factors involved in this variation These local epidemiological data will help us to re-think a newer strategy against these parasites.

The feeding of heather (Calluna vulgaris) to Teladorsagia circumcincta infected lambs reduces parasitism but can detrimentally impact performance.

Gastrointestinal nematode (GIN) infections impact small ruminant health, welfare, and production across farming systems. Rising anthelmintic resistance and regulation of synthetic drug use in organic farming is driving research and development of sustainable alternatives for GIN control. One alternative is the feeding of plants that contain secondary metabolites (PSMs) e.g., proanthocyanidins (PA, syn. condensed tannins) that have shown anthelmintic potential. However, PSMs can potentially impair performance, arising from reduced palatability and thus intake, digestibility or even toxicity effects. In this study, we tested the trade-off between the antiparasitic and anti-nutritional effects of heather consumption by lambs. The impact of additional feeding of a nematophagous fungus (Duddingtonia flagrans) on larval development was also explored. Lambs infected with Teladorsagia circumcincta or uninfected controls, were offered ad libitum heather, or a control chopped hay for 22 days during the infection patent period. Eight days into the patent period, parasitised lambs were supplemented (or remained unsupplemented) with D. flagrans for a 5-day period. Performance and infection metrics were recorded, and polyphenol levels in the heather and control hay were measured to investigate their association with activity. The lambs consumed heather at approximately 20% of their dry matter intake, which was sufficient to exhibit significant anthelmintic effects via a reduction in total egg output (P = 0.007), compared to hay-fed lambs; the magnitude of the reduction over time in heather fed lambs was almost 10-fold compared to control lambs. Negative effects on production were shown, as heather-fed lambs weighed 6% less than hay-fed lambs (P < 0.001), even though dry matter intake (DMI) of heather increased over time. D. flagrans supplementation lowered larval recovery in the faeces of infected lambs by 31.8% (P = 0.003), although no interactions between feeding heather and D. flagrans were observed (P = 0.337). There was no significant correlation between PA, or other polyphenol subgroups in the diet and egg output, which suggests that any association between heather feeding and anthelmintic effect is not simply and directly attributable to the measured polyphenols. The level of heather intake in this study showed no antagonistic effects on D. flagrans, demonstrating the methods can be used in combination, but provide no additive effect on overall anthelmintic efficacies. In conclusion, heather feeding can assist to reduce egg outputs in infected sheep, but at 20% of DMI negative effects on lamb performance can be expected which may outweigh any antiparasitic benefits.

Genetic profile of adaptive immune traits and relationships with parasite resistance and productivity in Scottish Blackface sheep.

Gastrointestinal (GI) parasites cause significant production losses in grazing ruminants which can be mitigated by breeding animals resistant to disease. Lymphocyte cytokine production and parasite-specific Immunoglobulin A (IgA) are adaptive immune traits associated with immunity to GI parasites. To explore the utility of these traits for selective breeding purposes, this study estimated the genetic parameters of the immune traits in sheep and assessed their relationship with disease and productivity traits. Whole blood stimulation assays were performed on 1 040 Scottish Blackface lambs at two months of age in 2016-2017. Blood was stimulated with either pokeweed mitogen (PWM), a non-specific activator of lymphocytes, and Teladorsagia circumcincta (T-ci) larval antigen to activate parasite-specific T lymphocytes. The type of adaptive immune response was determined by quantifying production of cytokines interferon-gamma (IFN-γ), interleukin (IL)-4, and IL-10, which relate to T-helper type (Th) 1, Th2 and regulatory T cell responses, respectively. Serum T-ci specific IgA was also quantified. Heritabilities were estimated for each immune trait by univariate analyses. Genetic and phenotypic correlations were estimated between different immune traits, and between immune traits vs. disease and productivity traits that were recorded at three months of age. Disease phenotypes were expressed as faecal egg counts (FEC) of nematode parasites (Strongyles and Nematodirus), faecal oocyst counts (FOC) of coccidian parasites, and faecal soiling score; production was measured as lamb live weight. Significant genetic variation was observed in all immune response traits. Heritabilities of cytokine production varied from low (0.14 ± 0.06) to very high (0.77 ± 0.09) and were always significantly greater than zero (P < 0.05). IgA heritability was found to be moderate (0.41 ± 0.09). Negative associations previously identified between IFN-γ production and FOC, and IL-4 production and strongyle FEC, were not evident in this study, potentially due to the time-lag between immune and parasitology measures. Instead, a positive genetic correlation was found between FOC and PWM-induced IFN-γ production, while a negative genetic correlation was found between FOC and T-ci induced IL-10. Live weight was negatively genetically correlated with IFN-γ responses. Overall, IFN-γ and IL-4 responses were positively correlated, providing little evidence of cross-regulation of Th1 and Th2 immunity within individual sheep. Furthermore, T-ci specific IgA was highly positively correlated with PWM-induced IL-10, indicating a possible role for this cytokine in IgA production. Our results suggest that while genetic selection for adaptive immune response traits is possible and may be beneficial for parasite control, selection of high IFN-γ responsiveness may negatively affect productivity.