Development of a recombinant protein-based ELISA for diagnosis of larval cyathostomin infection

Validation of a serum ELISA test for cyathostomin infection in equines

Cyathostomins are ubiquitous equine nematodes. Infection can result in larval cyathostominosis due to mass larval emergence. Although faecal egg count (FEC) tests provide estimates of egg shedding, these correlate poorly with burden and provide no information on mucosal/luminal larvae. Previous studies describe a serum IgG(T)-based ELISA (CT3) that exhibits utility for detection of mucosal/luminal cyathostomins. Here, this ELISA is optimised/validated for commercial application using sera from horses for which burden data were available. Optimisation included addition of total IgG-based calibrators to provide standard curves for quantification of antigen-specific IgG(T) used to generate a CT3-specific 'serum score' for each horse. Validation dataset results were then used to assess the optimised test's performance and select serum score cut-off values for diagnosis of burdens above 1000, 5000 and 10,000 cyathostomins. The test demonstrated excellent performance (Receiver Operating Characteristic Area Under the Curve values >0.9) in diagnosing infection, with >90% sensitivity and >70% specificity at the selected serum score cut-off values. CT3-specific serum IgG(T) profiles in equines in different settings were assessed to provide information for commercial test use. These studies demonstrated maternal transfer of CT3-specific IgG(T) in colostrum to newborns, levels of which declined before increasing as foals consumed contaminated pasture. Studies in geographically distinct populations demonstrated that the proportion of horses that reported as test positive at a 14.37 CT3 serum score (1000-cyathostomin threshold) was associated with parasite transmission risk. Based on the results, inclusion criteria for commercial use were developed. Logistic regression models were developed to predict probabilities that burdens of individuals are above defined thresholds based on the reported serum score. The models performed at a similar level to the serum score cut-off approach. In conclusion, the CT3 test provides an option for veterinarians to obtain evidence of low cyathostomin burdens that do not require anthelmintic treatment and to support diagnosis of infection.

Species interactions, stability, and resilience of the gut microbiota - Helminth assemblage in horses

The nature and strength of interactions entertained among helminths and their host gut microbiota remain largely unexplored. Using 40 naturally infected Welsh ponies, we tracked the gut microbiota-cyathostomin temporal dynamics and stability before and following anthelmintic treatment and the associated host blood transcriptomic response. High shedders harbored 14 species of cyathostomins, dominated by Cylicocyclus nassatus. They exhibited a highly diverse and temporal dynamic gut microbiota, with butyrate-producing Clostridia likely driving the ecosystem steadiness and host tolerance toward cyathostomins infection. However, anthelmintic administration sharply bent the microbial community. It disrupted the ecosystem stability and the time-dependent network of interactions, affecting longer term microbial resilience. These observations highlight how anthelmintic treatments alter the triangular relationship of parasite, host, and gut microbiota and open new perspectives for adding nutritional intervention to current parasite management strategies.

Advances in diagnosis of gastrointestinal nematodes in livestock and companion animals

Diagnosis of gastrointestinal nematodes in livestock and companion animals has been neglected for years and there has been an historical underinvestment in the development and improvement of diagnostic tools, undermining the undoubted utility of surveillance and control programmes. However, a new impetus by the scientific community and the quickening pace of technological innovations, are promoting a renaissance of interest in developing diagnostic capacity for nematode infections in veterinary parasitology. A cross-cutting priority for diagnostic tools is the development of pen-side tests and associated decision support tools that rapidly inform on the levels of infection and morbidity. This includes development of scalable, parasite detection using artificial intelligence for automated counting of parasitic elements and research towards establishing biomarkers using innovative molecular and proteomic methods. The aim of this review is to assess the state-of-the-art in the diagnosis of helminth infections in livestock and companion animals and presents the current advances of diagnostic methods for intestinal parasites harnessing (i) automated methods for copromicroscopy based on artificial intelligence, (ii) immunodiagnosis, and (iii) molecular- and proteome-based approaches. Regardless of the method used, multiple factors need to be considered before diagnostics test results can be interpreted in terms of control decisions. Guidelines on how to apply diagnostics and how to interpret test results in different animal species are increasingly requested and some were recently made available in veterinary parasitology for the different domestic species.

Characterisation of serum IgG(T) responses to potential diagnostic antigens for equine cyathostominosis

Cyathostomins are ubiquitous parasitic nematodes of horses. These worms spend substantial periods as intestinal wall stage encysted larvae, which can comprise up to 90% of the total burden. Several million larvae have been reported in individuals. Emergence of these larvae from the gut wall can lead to life-threatening colitis. Faecal egg count tests, increasingly used by horse owners to inform anthelmintic treatments, do not correlate with the intra-host burden of cyathostomins; this represents a key gap in the diagnostic toolbox. Previously, a cyathostomin Gut Associated Larval Antigen was identified as a promising marker for the intra-host stages of infection. Here, cyathostomin Gut Associated Larval Antigen and an additional protein, Cyathostomin Immuno-diagnostic antigen, were investigated to examine their value in providing information on cyathostomin burden. ELISA analyses examined serum IgG(T) responses to recombinant proteins derived from individual cyathostomin species. Receiver Operator Characteristic curve analysis was performed on the ELISA data; proteins with the highest Area Under the Curve values were selected to test protein combinations to investigate which were the most informative in identifying the infection status of individuals. Three cocktail combinations were tested, comprising: (a) Cy-GALA proteins from two species and a Cy-CID protein from a third species (CT3), (b) Cy-GALA proteins from five species (CT5), and (c) all CT5 components, plus a Cy-CID protein from an additional species (CT6). The best predictive values for infection were obtained using CT3 and CT6, with similar values achieved for both. Proteins in CT3 are derived from the most commonly reported species, Cyathostomum catinatum, Cylicocyclus nassatus and Cylicostephanus longibursatus. This combination was selected for future development since it represents a more commercially viable format for a diagnostic test.

Removal of adult cyathostomins alters faecal microbiota and promotes an inflammatory phenotype in horses

The interactions between parasitic helminths and gut microbiota are considered to be an important, although as yet incompletely understood, factor in the regulation of immunity, inflammation and a range of diseases. Infection with intestinal helminths is ubiquitous in grazing horses, with cyathostomins (about 50 species of which are recorded) predominating. Consequences of infection include both chronic effects, and an acute inflammatory syndrome, acute larval cyathostominosis, which sometimes follows removal of adult helminths by administration of anthelmintic drugs. The presence of cyathostomins as a resident helminth population of the equine gut (the "helminthome") provides an opportunity to investigate the effect helminth infection, and its perturbation, has on both the immune system and bacterial microbiome of the gut, as well as to determine the specific mechanisms of pathophysiology involved in equine acute larval cyathostominosis. We studied changes in the faecal microbiota of two groups of horses following treatment with anthelmintics (fenbendazole or moxidectin). We found decreases in both alpha diversity and beta diversity of the faecal microbiota at Day 7 post-treatment, which were reversed by Day 14. These changes were accompanied by increases in inflammatory biomarkers. The general pattern of faecal microbiota detected was similar to that seen in the relatively few equine gut microbiome studies reported to date. We conclude that interplay between resident cyathostomin populations and the bacterial microbiota of the equine large intestine is important in maintaining homeostasis and that disturbance of this ecology can lead to gut dysbiosis and play a role in the aetiology of inflammatory conditions in the horse, including acute larval cyathostominosis.

Nematode Species Identification-Current Status, Challenges and Future Perspectives for Cyathostomins

Human and animal health is globally affected by a variety of parasitic helminths. The impact of co-infections and development of anthelmintic resistance requires improved diagnostic tools, especially for parasitic nematodes e.g., to identify resistant species or attribute pathological effects to individual species or particular species combinations. In horses, co-infection with cyathostomins is rather a rule than an exception with typically 5 to 15 species (out of more than 40 described) per individual host. In cyathostomins, reliable morphological species differentiation is currently limited to adults and requires highly specialized expertize while precise morphological identification of eggs and early stage larvae is impossible. The situation is further complicated by a questionable validity of some cyathostomins while others might actually represent cryptic species complexes. Several molecular methods using different target sequences were established to overcome these limitations. For adult worms, PCR followed by sequencing of mitochondrial genes or external or internal ribosomal RNA spacers is suitable to genetically confirm morphological identifications. The most commonly used method to differentiate eggs or larvae is the reverse-line-blot hybridization assay. However, both methods suffer from the fact that target sequences are not available for many species or even that GenBank® entries are unreliable regarding the cyathostomin species. Recent advances in proteomic tools for identification of metazoans including insects and nematodes of the genus Trichinella will be evaluated for suitability to diagnose cyathostomins. Future research should focus on the comparative analysis of morphological, molecular and proteomic data from the same cyathostomin specimen to optimize tools for species-specific identification.