Use of excretory/secretory antigens for the serodiagnosis of Anoplocephala perfoliata cestodosis

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.

Equine tapeworm (Anoplocephala spp.) infection: evaluation of saliva- and serum-based antibody detection methods and risk factor analysis in Slovak horse populations

A lack of accurate information on the prevalence and distribution of Anoplocephala spp. infections on horse farms has led to insufficient attention to tapeworm control and increasing horse anoplocephaloses in Europe. Our study aimed to examine the occurrence of Anoplocephala spp. infection using coprological, serum- and saliva-based antibody detection methods and to analyze the risk factors associated with tapeworm infection in domestic horses in Slovakia. Fecal, serum, and saliva samples were collected from 427 horses from 31 farms in Slovakia. Additionally, a questionnaire study was conducted to collect information on tapeworm distribution on horse farms and analyze risk factors associated with infection. Fecal samples were examined by the mini-FLOTAC and the double centrifugation/combined sedimentation-flotation techniques. Serum and saliva samples were analyzed by ELISA to determine antibody levels against Anoplocephala spp. The effects of variables associated with an individual horse were tested for the positive result of the saliva ELISA test on Anoplocephala spp. Cestode eggs were detected in 1.99% of fecal samples (farm prevalence 12.90%), with no differences between the two coprological methods. Serum-based tapeworm ELISA results revealed that 39.39% of horses tested positive (farm prevalence 83.87%); while saliva-based tapeworm ELISA results revealed 56.95% positive horses (farm prevalence 96.77%). Binary logistic regression analysis revealed four meaningful predictors that significantly impacted the likelihood of detecting tapeworm infection in horses: horse age, pasture size, anthelmintic treatment scheme, and access to pasture. The influences of other variables associated with an individual horse were not significantly associated with detecting tapeworm infection.

The Use of Innovative Diagnostics to Inform Sustainable Control of Equine Helminth Infections

Helminths are commonly found in grazing equids, with cyathostomin nematodes and the cestode Anoplocephala perfoliata being the most prevalent. Most horses harbour low burdens of these parasites and do not develop signs of infection; however, in a small number of animals, high burdens can accumulate and cause disease. Cyathostomins are associated with a syndrome known as larval cyathostominosis. This occurs when large numbers of larvae emerge from the large intestinal wall. This disease has a case fatality rate of up to 50%. A. perfoliata infection has been associated with various types of colic, with burdens of >20 worms associated with pathogenicity. Anthelmintic resistance is a serious problem in cyathostomins and is emerging in A. perfoliata. Control methods that reduce reliance on anthelmintics now need to be applied, especially as no new dewormer compounds are on the horizon. Sustainable control methods must employ diagnostics to identify horses that require treatment. Coprological tests (faecal egg counts, FECs) have been used for several decades to inform treatment decisions to reduce helminth egg shedding. These tests cannot be used to assess host burdens as FECs do not correlate with cyathostomin or A. perfoliata burdens. In the last decade, new tests have become available that measure parasite-specific antibodies, the levels of which have been shown to correlate with parasite burden. These tests measure antigen-specific IgG(T) and are available in serum (cyathostomin, A. perfoliata) or saliva (A. perfoliata) formats. Tests for other helminths have been developed as research tools and need to be translated to support equine clinicians in practice. A key element of sustainable control strategies is that diagnostics must be used in combination with management approaches to reduce environmental transmission of helminths; this will help limit the proportion of horses harbouring parasite burdens that need to be targeted by treatment. This manuscript provides a review of the development, performance and general utility of various diagnostic methods for informing equine helminth management decisions.

Horse and donkey parasitology: differences and analogies for a correct diagnostic and management of major helminth infections

In June 2022, at the XXXII Conference of the Italian Society of Parasitology, the parallels of the main endoparasitic infections of horses and donkeys were discussed. Although these 2 species are genetically different, they can be challenged by a similar range of parasites (i.e. small and large strongyles, and Parascaris spp.). Although equids can demonstrate some level of resilience to parasites, they have quite distinct helminth biodiversity, distribution and intensity among different geographical locations and breeds. Heavily infected donkeys may show fewer clinical signs than horses. Although parasite control is primarily provided to horses, we consider that there may be a risk of drug-resistance parasitic infection through passive infection in donkeys when sharing the same pasture areas. Knowing the possible lack of drug efficacy (<90 or 80%), it is advocated the use of selective treatment for both species based on fecal egg counts. Adult horses should receive treatment when the threshold exceeds 200–500 eggs per gram (EPG) of small strongyles. Moreover, considering that there are no precise indications in donkeys, a value >300 EPG may be a safe recommendation. We have highlighted the main points of the discussion including the dynamics of helminth infections between the 2 species.

Apparent treatment failure of praziquantel and pyrantel pamoate against anoplocephalid tapeworms

Anoplocephalid tapeworms are commonly occurring in grazing horses around the world. Two currently available anthelmintics have documented high efficacy against Anoplocephala perfoliata; praziquantel in various dosages ranging from 1.0 to 2.5 mg/kg and pyrantel pamoate administered at 13.2 mg base/kg. Anthelmintic resistance has not been reported in A. perfoliata, but anecdotal reports made during 2022 have suggested a possible loss of efficacy for both actives. This paper reports fecal egg count data from a Thoroughbred operation in Central Kentucky in 2023. Fifty-six yearlings were first dewormed with a combination of ivermectin (200 μg/kg) and praziquantel (1.5 mg/kg) and subsequently treated with pyrantel pamoate (13.2 mg base/kg). Fecal egg counts were determined at the day of treatment and again 14 days post-treatment. Two groups of mares (n = 39 and 45) were also treated with ivermectin/praziquantel and examined pre- and post-treatment. Low efficacy of ivermectin and pyrantel pamoate was demonstrated against strongylid parasites in the yearlings with mean Fecal Egg Count Reductions (FECRs) at 75.6% or below and upper 95% credible interval (CI) limits below 90% in all cases. Overall anti-cestodal FECR levels in the yearlings were 23.5% (95% CI: 11.2-48.0) for praziquantel and 50.9% (20.5-72.0) for pyrantel pamoate. Praziquantel eliminated anoplocephalid eggs from three of 17 yearlings, but another 5 yearlings went from negative to positive status following treatment. Pyrantel pamoate failed to eliminate anoplocephalid eggs from any of 14 treated tapeworm-positive yearlings. Nine of 84 mares tested positive for anoplocephalid eggs, and seven of these were still positive post praziquantel treatment. These findings sharply contrast data from historic field efficacy studies conducted for both actives and raise concern about anthelmintic resistance having possibly developed. This emphasizes the need for developing and refining antemortem methodologies for evaluating anti-cestodal treatment efficacy and for searching for possible alternative treatment options.

What about the Cytoskeletal and Related Proteins of Tapeworms in the Host's Immune Response? An Integrative Overview

Recent advances have increased our understanding of the molecular machinery in the cytoskeleton of mammalian cells, in contrast to the case of tapeworm parasites, where cytoskeleton remains poorly characterized. The pertinence of a better knowledge of the tapeworm cytoskeleton is linked to the medical importance of these parasitic diseases in humans and animal stock. Moreover, its study could offer new possibilities for the development of more effective anti-parasitic drugs, as well as better strategies for their surveillance, prevention, and control. In the present review, we compile the results of recent experiments on the cytoskeleton of these parasites and analyze how these novel findings might trigger the development of new drugs or the redesign of those currently used in addition to supporting their use as biomarkers in cutting-edge diagnostic tests.

Label-free quantitative proteomics and immunoblotting identifies immunoreactive and other excretory-secretory (E/S) proteins of Anoplocephala perfoliata

Anoplocephala perfoliata is a common tapeworm in horses causing colic and even mortalities. Current diagnostic tests to detect A. perfoliata infections have their limitations and an improved method is needed. Immunoreactive excretory/secretory proteins (E/S proteome) of this parasite can provide promising candidates for diagnostic tests. We compared E/S proteins produced by small (length < 20 mm, width < 5 mm) and large (length 20 to 40 mm, width 5 to 10 mm) A. perfoliata worms in vitro by label-free quantitative proteomics using a database composed of related Hymenolepis diminuta, Echinococcus multilocularis/granulosus and Taenia aseatica proteins for protein identifications. Altogether, 509 E/S proteins were identified after incubating the worms in vitro for three and eight hours. The greatest E/S proteome changes suggested both worm size- and time-dependent changes in cytoskeleton remodeling, apoptosis, and production of antigens/immunogens. The E/S proteins collected at the three-hour time point represented the natural conditions better than those collected at the eight-hour time point, and thereby contained the most relevant diagnostic targets. Immunoblotting using antibodies from horses tested positive/negative for A. perfoliata indicated strongest antigenicity/immunogenicity with 13-, 30- and 100-kDa proteins, involving a thioredoxin, heat-shock chaperone 90 (Hsp90), dynein light chain component (DYNLL), tubulin-specific chaperone A (TBCA) and signaling pathway modulators (14-3-3 and Sj-Ts4). This is among the first studies identifying new diagnostic targets and A. perfoliata antigens eliciting a IgG-response in horses.

A Comparison of the Colonic Microbiome and Volatile Organic Compound Metabolome of Anoplocephala perfoliata Infected and Non-Infected Horses: A Pilot Study

Simple Summary

In horses, tapeworm infection is associated with specific forms of colic (abdominal pain) that can be life-threatening without surgical treatment. There is growing evidence that intestinal parasites interact with the gut bacteria, and the consequences of these interactions may influence the ability of the host to resist infection and parasite-associated disease. We aimed to compare the intestinal bacteria and the gases produced by metabolic processes in the gut between horses that had varying levels of tapeworms and those with no tapeworm present. Overall, the diversity of gut bacteria was similar in horses with and without tapeworms. There were some decreases in beneficial bacteria in horses with tapeworms, indicating a possible negative consequence of infection. Intestinal gases correlated with some bacteria indicating their functionality and use as potential markers of active bacteria. Our study validates further research investigating tapeworm and gut bacteria interactions in the horse.

Abstract

Anoplocephala perfoliata is a common equine tapeworm associated with an increased risk of colic (abdominal pain) in horses. Identification of parasite and intestinal microbiota interactions have consequences for understanding the mechanisms behind parasite-associated colic and potential new methods for parasite control. A. perfoliata was diagnosed by counting of worms in the caecum post-mortem. Bacterial DNA was extracted from colonic contents and sequenced targeting of the 16S rRNA gene (V4 region). The volatile organic compound (VOC) metabolome of colonic contents was characterised using gas chromatography mass spectrometry. Bacterial diversity (alpha and beta) was similar between tapeworm infected and non-infected controls. Some compositional differences were apparent with down-regulation of operational taxonomic units (OTUs) belonging to the symbiotic families of Ruminococcaceae and Lachnospiraceae in the tapeworm-infected group. Overall tapeworm burden accounted for 7–8% of variation in the VOC profile (permutational multivariate analysis of variance). Integration of bacterial OTUs and VOCs demonstrated moderate to strong correlations indicating the potential of VOCs as markers for bacterial OTUs in equine colonic contents. This study has shown potential differences in the intestinal microbiome and metabolome of A. perfoliata infected and non-infected horses. This pilot study did not control for extrinsic factors including diet, disease history and stage of infection.

Investigations on the occurrence of tapeworm infections in German horse populations with comparison of different antibody detection methods based on saliva and serum samples

Background

Effective and sustainable worm control in horses would benefit from detailed information about the current regional occurrence of tapeworms. Different diagnostic methods are currently available to detect Anoplocephala spp. infections in horses. However, the format as well as the sensitivity and specificity of the methods vary considerably.

Methods

A coprological, serological and questionnaire study was conducted to investigate the prevalence and risk factors of tapeworm infections on 48 horse farms in the region of Berlin and Brandenburg, Germany. In total, faecal samples of 484 horses were analysed using the double centrifugation/combined sedimentation-flotation and mini-FLOTAC. Serum (n = 481) and saliva (n = 365) samples were analysed by ELISAs to determine antibody levels against Anoplocephala spp. 12/13 kDa excretory/secretory (E/S) antigens.

Results

Cestode eggs were detected in 0.6% of faecal samples (farm prevalence 6.3%) without differences between the two methods. In contrast, antibodies against Anoplocephala spp. were detected in 16.2% (farm prevalence 52.1%) and in 29.5% (farm prevalence 75.7%) of the serum and saliva samples, respectively. Both ELISA based methods for detection of tapeworms reported a greater number of infected animals requiring treatment than were positively identified by coproscopy. Logistic regression analysis identified permanent pasture access, large pastures and regular pasture changes and high strongyle egg counts as risk factors for positive serum antibody responses to Anoplocephala spp. while last treatment with praziquantel was protective. Other protective factors were the presence of foals and high numbers of horses on the farm. Daily removal of faeces from the pasture and horse age did not have a significant effect.

Conclusions

The findings of the present serological investigation indicate that tapeworm prevalence in Berlin/Brandenburg horse farms is much higher than would be anticipated by using conventional/coproscopic analyses. Moreover, the majority of tapeworm-positive horses had not received a cestocidal drug at their last treatment. Considering the already known low sensitivity of the coproscopic detection, the equine veterinary diagnostics can be enhanced by the use of antibody detection methods such as the saliva-based ELISA.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-020-04318-5) contains supplementary material, which is available to authorized users.

Validation of a novel saliva-based ELISA test for diagnosing tapeworm burden in horses

BACKGROUND

Tapeworm infections pose a significant threat to equine health as they are associated with clinical cases of colic. Diagnosis of tapeworm burden using fecal egg counts (FECs) is unreliable, and, although a commercial serologic ELISA for anti-tapeworm antibodies is available, it requires a veterinarian to collect the blood sample. A reliable diagnostic test using an owner-accessible sample such as saliva could provide a cost-effective alternative for tapeworm testing in horses, and allow targeted deworming strategies.

OBJECTIVES

The purpose of the study was to statistically validate a saliva tapeworm ELISA test and compare to a tapeworm-specific IgG(T) serologic ELISA.

METHODS

Serum samples (139) and matched saliva samples (104) were collected from horses at a UK abattoir. The ileocecal junction and cecum were visually examined for tapeworms and any present were counted. Samples were analyzed using a serologic ELISA and the saliva tapeworm test. The test results were compared to tapeworm numbers and the various data sets were statistically analyzed.

RESULTS

Saliva scores had strong positive correlations with both infection intensity (0.74) and serologic results (Spearman's rank coefficients; 0.74 and 0.86, respectively). The saliva tapeworm test was capable of identifying the presence of one or more tapeworms with 83% sensitivity and 85% specificity. Importantly, no high-burden (more than 20 tapeworms) horses were misdiagnosed.

CONCLUSIONS

The saliva tapeworm test has statistical accuracy for detecting tapeworm burdens in horses with 83% sensitivity and 85% specificity, similar to those of the serologic ELISA (85% and 78%, respectively).

New multiplex PCR method for the simultaneous diagnosis of the three known species of equine tapeworm

Although several techniques exist for the detection of equine tapeworms in serum and feces, the differential diagnosis of tapeworm infection is usually based on postmortem findings and the morphological identification of eggs in feces. In this study, a multiplex polymerase chain reaction (PCR)-based method for the simultaneuos detection of Anoplocephala magna, Anoplocephala perfoliata and Anoplocephaloides mamillana has been developed and validated. The method simultaneously amplifies hypervariable SSUrRNA gene regions in the three tapeworm species in a single reaction using three pairs of primers, which exclusively amplify the internal transcribed spacer 2 (ITS-2) in each target gene. The method was tested on three types of sample: (a) 1/10, 1/100, 1/500, 1/1000, 1/2000 and 1/5000 dilutions of 70 ng of genomic DNA of the three tapeworm species, (b) DNA extracted from negative aliquots of sediments of negative control fecal samples spiked with 500, 200, 100, 50 and 10 eggs (only for A. magna and A. perfoliata; no A. mamillana eggs available) and (c) DNA extracted from 80, 50, 40, 30, 10 and 1 egg per 2 μl of PCR reaction mix (only for A. magna and A. perfoliata; no A. mamillana eggs available). No amplification was observed against the DNA of Gasterophilus intestinalis, Parascaris equorum and Strongylus vulgaris. The multiplex PCR method emerged as specific for the three tapeworms and was able to identify as few as 50 eggs per fecal sample and as little as 0.7 ng of control genomic DNA obtained from the three species. The method proposed is able to differentiate infections caused by the two most frequent species A. magna or A. perfoliata when the eggs are present in feces and is also able to detect mixed infections by the three cestode species.

Serum Strongylus vulgaris-specific antibody responses to anthelmintic treatment in naturally infected horses

Strongylus vulgaris is the most pathogenic helminth parasite of horses, causing verminous endarteritis with thromboembolism and infarction. A serum enzyme-linked immunosorbent assay (ELISA) has been validated for detection of antibodies to an antigen produced by migrating larvae of this parasite. The aim was to evaluate ELISA responses to anthelmintic treatment in cohorts of naturally infected horses. Fifteen healthy horses harboring patent S. vulgaris infections were turned out for communal grazing in May 2013 (day 0). On day 55, horses were ranked according to ELISA titers and randomly allocated to the following three groups: no treatment followed by placebo pellets daily; ivermectin on day 60 followed by placebo pellets daily; or ivermectin on day 60 followed by daily pyrantel tartrate. Fecal and serum samples were collected at ∼28-day intervals until study termination on day 231. Increased ELISA values were observed for the first 53 days following ivermectin treatment. Titers were significantly reduced 80 days after ivermectin treatment. Horses receiving daily pyrantel tartrate maintained lower ELISA values from 137 days post ivermectin treatment until trial termination. These results illustrate that a positive ELISA result is indicative of either current or prior exposure to larval S. vulgaris infection within the previous 5 months.

Systemic and mucosal IgE antibody responses of horses to infection with Anoplocephala perfoliata

Infection of horses with Anoplocephala perfoliata induces a severe inflammatory reaction of the caecal mucosa around the site of parasite attachment adjacent to the ileocecal valve. Lesions show epithelial erosion or ulceration of the mucosa with infiltration by eosinophils, lymphocytes and mast cells leading to oedema, gross thickening and fibrosis of the caecal wall. Despite this evidence of an inflammatory reaction to A. perfoliata within the mucosa of the caecum there is little information about the nature of the local immune response to A. perfoliata. An ELISA which assays serum IgG(T) antibodies to A. perfoliata excretory/secretory antigens has been developed as a diagnostic test. However, the specificity of the ELISA remains sub-optimal and the role of other isotypes in the immune response to A. perfoliata has not been reported. This study measured IgA, IgE and IgG(T) antibody responses to A. perfoliata excretory/secretory antigens in sera of 75 horses presented for slaughter. The prevalence of A. perfoliata infection, as confirmed by the presence of parasites in the terminal ileum, caecum or proximal colon, was 55%. A. perfoliata-specific IgG(T) and IgE antibodies were significantly elevated in infected horses compared to controls; IgA antibodies were also detected but did not differ between infected and control horses. Diagnosis by serum IgG(T) ELISA had a sensitivity of 78% and a specificity of 80%, by comparison the serum IgE ELISA had a sensitivity of just 44% with a specificity of 82% and therefore did not provide an improved diagnostic test. Western blots with sera from infected horses demonstrated IgE-binding to at least 10 separate components of excretory/secretory (E/S) antigens. A similar pattern was also found with IgG(T). Around 30% of horses had high levels of serum IgE which bound fucose-containing carbohydrate antigens on the parasite surface but this was unrelated to the presence of A. perfoliata infection. Immunoperoxidase staining detected numerous IgE-positive cells within lymphoid follicles in the caecal mucosa close to the site of A. perfoliata attachment and quantitative RT-PCR detected high levels of IgE transcription in the caecal mucosa of all horses. Mucosal synthesis of antibodies was confirmed by the demonstration of A. perfoliata-specific IgG(T) and IgE in the supernatant of lamina propria explant cultures that discriminated clearly between infected and uninfected horses. We conclude that there is an active immune response to A. perfoliata within the caecal mucosa involving local production of both IgG(T) and IgE antibody isotypes; but it remains unclear whether this immune response can reduce or eliminate parasite burden.

Equine cestodosis: a sero-epidemiological study of Anoplocephala perfoliata infection in Ethiopia

A 12/13 kDa antigen, tapeworm ELISA test, developed for use in horses, was used to detect parasite-specific serum antibody, IgG(T), in the serum of donkeys. In a pilot study the 12/13 kDa antigen was tested and proved to detect the antibody, IgG(T), in donkey sera. Blood samples from 797 donkeys, naturally exposed to cestode infection, from four geographical localities were collected and sera were prepared and analysed. There was substantial serological evidence that donkeys were potentially infected with A. perfoliata. A range of ELISA OD values were obtained from the serological assay. Over 26% and 7.5% of the donkeys were moderately and highly infected, respectively, showing at least a 34% sero-prevalence. The rest, 66.1%, were either with low infection intensity or negative for A. perfoliata infection. The risk of infections, both in sero-prevalence and intensity, as determined by ELISA optical density (OD), were highest in the highland areas of Ethiopia where pastures are low-lying and wet, and permanent pasture management is regularly practised. Sex, age and body condition of the donkeys had no significant effect either on prevalence of the infection or on the serum antibody level. These results indicate a risk of intestinal disorders, particularly, colic, associated with A. perfoliata infection in donkeys.

A survey of health care and disease in geriatric horses aged 30 years or older

This study reports on aspects of preventive health care and on the prevalence of disease in geriatric (≥30 years old) horses and ponies in North-West England and North Wales. Of 128 questionnaires mailed to horse owners, 87 useable responses were received and 69 horses were subject to veterinary examination. Of the animals examined, 16% were underweight with body condition scores (BCS)<2/5, and 10% were overweight (BCS>3/5). This contrasted with the owner responses that reported 23% of the animals surveyed to be underweight and only 3% to be overweight. When assessed at trot, 77% of the horses were lame on at least one limb, with 97% having a reduced range of motion in at least one joint. Only 16% of these animals were reported by owners to have been lame within the previous 12 months. Owner-reported changes to hair coat were significantly associated with hirsutism or abnormal moulting detected at clinical examination (39%). At least one ophthalmic lesion was identified in all of the horses and ponies examined and 17% of owners reported that their animal had experienced visual problems within the previous year. Although dental abnormalities were detected in all animals where an oral examination was performed, only 42% of owners reported that their horse suffered from a known dental disorder. In general, despite a high prevalence of disease detected in these geriatric animals and with the majority having multiple abnormalities at clinical examination, there was under-reporting/under-recognition of these health problems by owners.

Evaluation of a double centrifugation technique for the detection of Anoplocephala eggs in horse faeces

Faecal samples of 250 horses from farms with a known history of tapeworm infection were examined comparatively for cestode eggs using a double centrifugation/combined sedimentation–floatation technique. From each faecal sample, three 5 g and three 15 g subsamples were processed, each using either saturated NaCl solution, specific gravity (sp. g.) 1.2 [NaCl]; concentrated sugar solution, sp. g. 1.26 [sugar]; or concentrated ZnSO4 solution, sp. g. 1.3 [ZnSO4] for floatation. In total, faeces from 187 horses ( = 74.8%) tested ‘positive’ for Anoplocephala eggs. Percentages of samples testing ‘positive’ for Anoplocephala ova were: 57.2% for 5 g faeces/NaCl, 66% for 15 g faeces/NaCl, 66% for 5 g faeces/sugar, 72.8% for 15 g faeces/sugar, 55.6% for 5 g faeces/ZnSO4, and 61.2% for 15 g faeces/ZnSO4, respectively. Processing of 15 g faecal samples resulted in a significant (P < 0.05; McNemar's χ2-test) increase in the percentage of Anoplocephala egg detection compared to processing of 5 g samples for all floatation solutions. By processing 15 g faecal samples using sugar solution for floatation, 97.3% of all samples that tested ‘positive’ for Anoplocephala eggs were identified; there was no significant difference between the rate of samples that tested ‘positive’ using 15 g faeces/sugar (72.8%) and the total rate of samples that tested ‘positive’ (74.8%). Conversely, percentages of ‘positive’ samples from other test combinations were significantly (P < 0.0001, McNemar's χ2-test) lower than the total rate of samples testing ‘positive’. Processing faecal samples using sugar solution for floatation gave significantly (P < 0.05, Wilcoxon test) higher Anoplocephala egg counts than using NaCl and ZnSO4 solutions, for both 5 g and 15 g faecal samples. The double centrifugation technique using 15 g faecal samples and concentrated sugar solution for floatation appeared to offer an advantage for the detection of Anoplocephala eggs in horse faeces compared to the other test combinations.

Protein expression profile of Gasterophilus intestinalis larvae causing horse gastric myiasis and characterization of horse immune reaction

Background

Little information is available on the immunological aspect of parasitic Gasterophilus intestinalis (Diptera, Oestridae) larvae causing horse gastric myiasis. The objectives of this research were to analyze the protein content of larval crude extracts of the migrating second and third larvae (L2 and L3) of G. intestinalis in order to characterize the immune response of horses.

Results

The proteomic profile of L2 and L3, investigated by using one and two dimensional approaches, revealed a migration pattern specific to each larval stage. Furthermore, Western blots were performed with horse sera and with sera of Balb/c mice immunised with the larval crude extracts of L2 or L3, revealing a different immune reaction in naturally infected horses vs. artificially induced immune reaction in mice. The comparisons of the immunoblot profiles demonstrate that the stage L2 is more immunogenic than the stage L3 most likely as an effect of the highest enzymatic production of L2 while migrating through the host tissues. Fifteen proteins were identified by mass spectrometry.

Conclusion

This work provides further information into the understanding of the interaction between G. intestinalis and their host and by contributing a novel scheme of the proteomic profile of the main larval stages.

Molecular diagnosis and equine parasitology

The future implementation of improved and sustainable control strategies for the major equine parasites will be dependent on a greater insight into their basic biology, pathogenicity and epidemiology together with an enhanced ability for accurate diagnosis. This paper will provide a review of the current molecular methods under development for the detection of equine parasites and their application to current scientific questions. In particular, the strongyles are recognised as important pathogens of horses and recent advances made in the study of this parasitic group at the single species level will be addressed. The ribosomal (r)DNA region of the parasite genome has been employed to distinguish between closely related species. Molecular probes designed to this target region were used in combination with PCR technology to allow the identification of individual species within mixed infections. They have been applied to all parasite stages to look at the role of individual species in natural infection, disease and drug resistance. Similar techniques have been developed to detect other equine parasites and these will also be discussed. Further opportunities for employing existing techniques and the need for new diagnostic tools will be highlighted.

Prevalence and diagnosis of parasites of the stomach and small intestine in horses in south-west England

Parasites were extracted from the stomach and small intestine of 118 horses at slaughter. The most abundant species was the tapeworm Anoplocephala perfoliata. Maximum likelihood analysis was used to investigate the relationship between the number of worms and their total weight, and the ability of an antibody-based elisa to diagnose the level of infection. The total weight of tapeworms increased towards a maximum as the number of worms increased, suggesting a population density-dependent constraint on the weight. The number of A perfoliata present could be predicted approximately from the results of the elisa. Although wide variation in elisa optical densities confound interpretation in individual animals, tests on groups of animals could provide a useful reflection of overall levels of infection.

Anoplocephala perfoliataof horses – significant scope for further research, improved diagnosis and control

Anoplocephala perfoliatais the commonest tapeworm parasite of horses and is incriminated as a significant cause of clinical disease (e.g., ileocaecal intussusception, caeco-caecal intussusception and/or caecal perforation), particularly in horses chronically infected with large numbers of worms. The high prevalence (~20–80%) of the parasite in some countries suggests an increased risk of clinical cases. In spite of research, there is still a paucity of information regarding the pathogenesis of the disease, the epidemiology of the parasite in different geographical regions and there are significant limitations with the diagnosis of infection. The present article provides an account of the biology, epidemiology and pathogenic effects ofA. perfoliata, the diagnosis of infection and treatment. It highlights some gaps in knowledge of the parasite and the disease it causes, and suggests opportunities for future research and prospects for improved diagnosis, prevention and control.

Anoplocephala perfoliata coproantigen detection: a preliminary study

Anoplocephala perfoliata has a prevalence as high as 60% in some geographical areas and has been associated with increased risk for serious conditions in the horse including bowel irritation, ileal impaction, and spasmodic colic. Identification of infected animals based upon detection of eggs in feces is labor intensive and unreliable. This study involved the development of a test for A.perfoliata coproantigen using an antigen capture enzyme linked immunosorbent assay (ELISA) and correctly distinguished between infected and uninfected animals in a trial with a small sample size.

Amplification of ribosomal DNA of Anoplocephalidae: Anoplocephala perfoliata diagnosis by PCR as a possible alternative to coprological methods

The diagnosis of tapeworm infections in horses relies on copro-diagnostic methods, which are time-consuming and of limited sensitivity for determination of the exact prevalence. The development of serological tests has slightly improved the detection of tapeworm infections, but more sensitive methods are still required. A polymerase chain reaction (PCR)-based approach may constitute a valuable tool to improve tapeworm diagnosis. Nuclear ribosomal DNA (rDNA) is a useful target for species and/or strain markers. Partial 18S, the internal transcribed spacer 1 (ITS-1), the 5.8S, the internal transcribed spacer 2 (ITS-2), and partial 28S rDNA of the equine tapeworms Anoplocephala perfoliata and Anoplocephaloides mamillana were amplified and sequenced. The lengths and GC contents of the regions sequenced were 2087-2091bp and 49.35-49.69% for A. perfoliata, and 2110-2119bp and 49.15-49.32% for A. mamillana, respectively. Sequence alignment and comparison of both taxa showed 79.3-80.2% identity. The lowest identities were found in the ITS regions with 39.9-43.5% for the ITS-1 and 59.5-61.2% for the ITS-2. No matches of the ITS-2 of A. perfoliata and A. mamillana were found with other species by BLAST search. For this reason, ITS-2 sequences seemed appropriate as accurate species markers and A. perfoliata ITS-2 primers were developed. The ITS-2 PCR enabled the detection of genomic DNA as low as 0.5 pgs. First efforts on the practical application of the PCR-based approach were made. A 6-mg fragment of a tapeworm proglottid was detected in 0.5 and 1g of faeces.

Field trial of the efficacy of a combination of ivermectin and praziquantel in horses infected with roundworms and tapeworms

Two hundred and thirty-three horses were screened for the presence of roundworms by faecal egg counts (FECs) and for tapeworms by an ELISA specific for antibodies to the immunodominant 12 kDa and 13 kDa tapeworms antigen. The 62 horses were found to be infected with both parasites were treated with a combination of 0.2 mg/kg ivermectin and 1.5 mg/kg praziquantel. The treatment suppressed the median FEC of the horses to zero for 10 weeks and significantly reduced their anti-12/13 kDa antibody levels. The estimated risk of tapeworm-associated colic in these horses was halved by 12 weeks after the treatment.

Tapeworms as a cause of intestinal disease in horses

Until recently, the equine tapeworm Anoplocephala perfoliata was difficult to diagnose and considered to be of questionable pathogenicity. Here, Chris Proudman and Sandy Trees describe recent advances in the immunodiagnosis of this parasite that have facilitated epidemiological studies. These studies suggest that A. perfoliata may be an important cause of intestinal disease in the horse and demonstrate a dose-response relationship between infection intensity and risk of disease. If tapeworm infection is a risk factor for ileocaecal colic, the identification and treatment of infected individuals would be a rational approach to disease prevention.

Tapeworm infection is a significant risk factor for spasmodic colic and ileal impaction colic in the horse

The association between the equine intestinal tapeworm Anoplocephala perfoliata and specific types of intestinal disease was investigated by matched case-control study using coprological and serological diagnosis. We have previously shown that the host IgG(T) response to 12/13 kDa antigens of A. perfoliata correlates well with infection intensity, therefore this antibody response was used to investigate the risk of colic at different levels of parasite infection intensity. One hundred and three spasmodic colic cases with an equal number of controls matched for age, breed and gender, and 20 ileal impaction cases each with 2 similarly matched controls were obtained. Cases of spasmodic colic were much more likely (odds ratio = 8.0) to be associated with A. perfoliata infection detected coprologically than controls. Serological diagnosis revealed an increasing risk of spasmodic colic with increasing infection intensity. Calculation of an aetiological fraction suggests that 22% of spasmodic colic cases in this study were tapeworm associated. No significant association was found between colic and strongyle egg count. Conditional logistic regression analysis demonstrated that the relationship between colic and A. perfoliata infection intensity was not confounded by strongyle egg count and there was a linear relationship between infection intensity and the log-odds of spasmodic colic. For cases of ileal impaction, a strong association was found between colic and A. perfoliata as diagnosed by coprological means (odds ratio of 34.0). Serological diagnosis also revealed a strong association that increased with higher levels of infection intensity (odds ratio = 26.0). The aetiological fraction for the ileal impaction data suggests that 81% of the ileal impaction cases in this study were tapeworm associated. This study concludes that A. perfoliata is a significant risk factor for spasmodic colic and ileal impaction colic in the horse; and that the risk of spasmodic colic increases with infection intensity.

Epidemiology of Anoplocephala perfoliata infection in foals on a stud farm in south-western Sweden

The egg output and humoral antibody response to scolex antigens of the equine tapeworm Anoplocephala perfoliata were monitored in naturally infected foals by an egg flotation/centrifugation method and an indirect enzyme-linked immunosorbent assay (ELISA). The study was performed on a stud farm in south-western Sweden between May 1994 and April 1995. Sequential blood and faecal samples were taken from 21 foals during their first summer on pasture and until tapeworm eggs were detected. Results were expressed separately for 10 and 11 foals born before and after the end of April 1994, respectively. Increased levels of antibodies were noticed from October and onwards in both groups whereas tapeworm eggs were detected in the faeces of all foals about 4 months later. The antibody response was similar in both groups but it was more pronounced in foals born before April 1994. All foals were treated in March 1995 with an oral paste formulation of pyrantel pamoate at a dose rate of 38 mg/kg bodyweight. Most animals responded to the anthelmintic treatment and one month later, tapeworm eggs were only detected in one out of the 18 foals examined one month after treatment. Thus, the treatment reduced the number of A. perfoliata egg positive horses by 94%. A concomitant decline in antibody levels was also observed. Western immunoblot analysis of sequential individual serum samples showed that at least 10 different scolex antigens in the molecular weight range 10-200 kDa were recognised. Banding intensities, especially of the 10 kDa, 45 kDa and 66 kDa proteins were different in the sequential sera taken during the course of infection.

Reliability of coprological diagnosis of Anoplocephala perfoliata infection

Three coprological methods were tested to establish the reliability of in vivo diagnosis of Anoplocephala perfoliata. A total of 107 faecal samples were analyzed, and the presence of tapeworms were confirmed postmortem in 24 animals with burdens that ranged from 1 to 248 worms; most of them (71%) with less than 100 parasites. Best results were obtained with a combination of two sedimentation/flotation methods, detecting only half the parasitized animals (54% sensitivity). No relationship could be established between tapeworm burden and egg detection, but results indicate that coprological methods have a lower likelihood of diagnosing cestode infection when horses have less than 100 tapeworms.