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

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.

Anoplocephalid tapeworms in mountain gorillas (Gorilla beringei beringei) inhabiting the Volcanoes National Park, Rwanda

Cestodes of the family Anoplocephalidae parasitize a wide range of usually herbivorous hosts including e.g. rodents, ungulates, primates, elephants and hyraxes. While in some hosts, the epidemiology of the infection is well studied, information is lacking in others. In this study of mountain gorillas in the Virunga Massif, an extensive sample set comprising adult cestodes collected via necropsies, proglottids shed in feces, and finally, fecal samples from both night nests and identified individuals were analysed. Anoplocephala gorillae was the dominant cestode species detected in night nest samples and individually known gorillas, of which only 1 individual hosted a Bertiella sp. It was shown that the 2 species can be distinguished through microscopy based on egg morphology and polymerase chain reaction (PCR) assays for diagnostics of both species were provided. Sequences of mitochondrial (cox 1) and nuclear (ITS1, 18S rDNA, 28S rDNA) markers were used to evaluate the phylogenetic position of the 2 cestodes detected in mountain gorillas. Both types of fecal samples, from night nests and from identified individuals, provided comparable information about the prevalence of anoplocephalid cestodes, although the analysis of samples collected from identified gorilla individuals showed significant intra-individual fluctuation of A. gorillae egg shedding within a short period. Therefore, multiple samples should be examined to obtain reliable data for wildlife health management programmes, especially when application of anthelmintic treatment is considered. However, while A. gorillae is apparently a common symbiont of mountain gorillas, it does not seem to impair the health of its host.

Molecular diagnostics for gastrointestinal helminths in equids: Past, present and future

This review is aimed to (i) appraise the literature on the use of molecular techniques for the detection, quantification and differentiation of gastrointestinal helminths (GIH) of equids, (ii) identify the knowledge gaps and, (iii) discuss diagnostic prospects in equine parasitology. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines for systematic reviews, we retrieved 54 studies (horses: 50/54; donkeys and zebras: 4/54) from four databases. Polymerase chain reaction (PCR) was employed in all of the studies whereas PCR amplicons were sequenced in only 18 of them. Other techniques used (including modifications of PCR) were reverse line blot, quantitative (q)PCR, restriction fragment length polymorphism, nested-PCR, PCR-directed next-generation sequencing, Southern blotting, single strand conformation polymorphism, PCR-enzyme linked immunosorbent assay, matrix-assisted laser desorption/ionisation-time of flight and random amplification of polymorphic DNA. Most of the studies (53/54) used nuclear ribosomal RNA (including the internal transcribed spacers, intergenic spacer, 5.8 S, 18 S, 28 S and 12 S) as target loci while cytochrome c oxidase subunit 1 and random genomic regions were targeted in only three and one studies, respectively. Overall, to date, the majority of molecular studies have focused on the diagnosis and identification of GIHs of equids (i.e. species of Anoplocephala, Craterostomum, cyathostomins, Oesophagodontus, Parascaris, Strongylus, Strongyloides and Triodontophorus), with a recent shift towards investigations on anthelmintic resistance and the use of high-throughput nemabiome metabarcoding. With the increasing reports of anthelmintic resistance in equid GIHs, it is crucial to develop and apply techniques such as advanced metabarcoding for surveillance of parasite populations in order to gain detailed insights into their diversity and sustainable control. To the best of our knowledge, this is the first systematic review that evaluates molecular investigations published on the diagnosis and quantification of equid GIHs and provides useful insights into important knowledge gaps and future research directions in equid molecular parasitology.

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.

Equine helminth prevalence and management practices on Australian properties as shown by coprological survey and written questionnaire

Context Parasite control is an essential part of a broader equine health-management strategy and is often completely administered by the horse owner, with little or no supporting evidence on which to base decisions. Practical and sound advice relies on knowledge of the resident parasite species, the anthelmintic resistance status of important species, and the strategies currently being utilised by owners and managers of horses. Much of this farm-level information is lacking in the Australian literature. Aims The present study aimed to gather both farm- and horse-level prevalence data for four important equine helminth species and to gather information on the current worm-management practices conducted on Australian horse farms. Methods We conducted a coprological survey of cyathostomins, Strongylus vulgaris, Parascaris spp. and equine tapeworm on 102 horse properties, using a combination of classical and molecular parasitological methods, including a tapeworm polymerase chain reaction developed as part of the study. A questionnaire canvasing horse owners on internal parasite-control practices was also distributed. Key results Cyathostomin were present on all farms surveyed and S. vulgaris, despite being considered rare, was present on 7.8% (95% CI: 3.9–15.0) of farms. The prevalence of Parascaris spp. and equine tapeworm was 33.3% (95% CI: 19.6–50.6) and 3.9% (95% CI: 1.5–10.1) respectively. Questionnaire responses showed that the majority (85.0%) of horse owners administer anthelmintics at regular intervals of 12 weeks or less, and only 2.6% utilise faecal egg counts to inform treatment decisions. Conclusions Prevalence data confirmed the endemic nature of cyathostomin and P. equorum infections, as well as low levels of tapeworm and S. vulgaris infections on Australian horse farms. Worm-management practices were reminiscent of traditional interval-style treatment regimens that rely heavily on macrocyclic lactone anthelmintics. Implications These results suggest a need for more strategic approaches to internal-parasite control in horses to slow the development of anthelmintic resistance. Such programs need to consider the risk of re-establishment of the pathogenic S. vulgaris in significant numbers.

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.

Comparison of the sensitivity of coprological methods in detecting Anoplocephala perfoliata invasions

The autopsy of 487 slaughter horses revealed the presence of Anoplocephala perfoliata in 36 animals. The invasions varied in the intensity (3 to 2,069 tapeworms) and in the level of tapeworms’ proglottid maturity. Twenty nine horses were found to contain tapeworms with gravid proglottid. Fecal samples collected from the rectum were tested using following techniques: flotation with solution-saturated NaCl, decantation, McMaster’s, and modified sedimentation-flotation methods (50 g feces samples, flotation solution-saturated NaCl and sucrose, specific gravity 1.25 g/ml). The number of A. perfoliata positive fecal samples was significantly higher using the sedimentation-flotation methods 21 (58.33 %) than flotation 6 (16.66 %), decantation 3 (8.33 %), and McMaster’s 1 (2.77 %) techniques. The sensitivities of the coprological methods during the patent period were 20.69, 10.34, 3.45, and 72.41 % for the flotation, decantation, McMaster’s, and sedimentation-flotation method, respectively. Sedimentation–flotation techniques proved to be more sensitive than other one. The lowest intensity of invasion possible to detect using this method was nine tapeworms with gravid proglottid.

Differential diagnosis of Moniezia benedeni and M. expansa (Anoplocephalidae) by PCR using markers in small ribosomal DNA (18S rDNA)

Moniezia benedeni and M. expansa are common ruminant tapeworms of worldwide distribution, causing gastrointestinal disorders and even death in sheep and goats. In this study, a polymerase chain reaction- (PCR-) based approach for precise species identification was developed and also applied to faecal DNA diagnosis of the tapeworm infection. Since nuclear ribosomal DNA (rDNA) appears to be a useful target for species and/or strain markers, the 18S regions of the rDNA of M. benedeni and M. expansa were amplified and sequenced. The lengths and GC contents of the regions sequenced were 2476-2487 bp and 51.9-52.1% for M. benedeni and 2473 bp and 51.9-52.0% for M. expansa, respectively. Alignment and comparison of the 18S sequences of the two species showed 92.5-93.3% homology. No matches for the 18S regions of M. benedeni and M. expansa were found with other species by BLAST search, which made the 18S sequences appropriate markers for the design of distinctive primers for the two Moniezia species. Our 18S-based PCR could detect as low levels as 0.5 pg genomic DNA or the DNA extracted from 0.2 g faecal sample collected from the rectum of an M. expansa-infected goat. The results indicate that this PCR approach is a reliable alternative for the differential diagnosis of Moniezia species in faecal samples.

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.

Factors influencing Dipylidium sp. infection in a free-ranging social carnivore, the spotted hyaena (Crocuta crocuta)

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We investigated Dipylidium infection in a social carnivore, the spotted hyaena.

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Infection predominantly occurred in juveniles, most adults were probably immune.

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Juvenile infection prevalence increased with the number of hyaenas visiting dens.

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Infection prevalence in juveniles decreased when they were least well fed.

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The use of communal dens maintains Dipylidium infection in spotted hyaena clans.

We provide the first genetic sequence data for a Dipylidium species from a wild carnivore plus an analysis of the effects of ecological, demographic, physiological and behavioural factors on Dipylidium sp. infection prevalence in a social carnivore, the spotted hyaena (Crocuta crocuta), in the Serengeti National Park, Tanzania. Our sequence data from a mitochondrial gene fragment (1176 base pair long) had a similarity of between 99% and 89% to Dipylidium caninum. We determined infection prevalence in 146 faecal samples from 124 known animals in three social groups (termed clans) using molecular screening and Dipylidium proglottid presence. Our analysis revealed significantly higher infection prevalence in juveniles (55%) than adults (15.8%), indicating that predominantly juveniles maintained infection in clans. The likelihood of infection in juveniles significantly: (1) increased as the number of adults and older juveniles (>6 months) at communal dens increased, implying a positive relationship between this factor and the size of the intermediate host (probably a flea species) population at communal dens; (2) decreased as the number of younger juveniles (<6 months) increased, suggesting that the chance of susceptible juveniles ingesting infected fleas during self-grooming declined as the number of infected fleas per younger juvenile declined; and (3) decreased during periods of low prey abundance in clan territories when an increased reliance on long-distances foraging excursions reduces the number of clan members visiting communal dens, possibly resulting in a decline in flea populations at dens. Long-distance foraging also increases the intervals (in days) between nursing visits by lactating females to their offspring. Lengthy intervals between milk intake by infected juveniles may reduce adult Dipylidium fecundity and hence decrease infection prevalence in the den flea population. Our study provides useful insights into Dipylidium epidemiology in a social carnivore population subject to large fluctuations in prey abundance.

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.

Redescription and resurrection of Bertiella satyri (Cestoda, Anoplocephalidae) parasitizing the orangutan (Pongo abelii) in Indonesia

The tapeworm species Bertiella satyri from a semi-wild Sumatran orangutan (Pongo abelii: Ponginae) is redescribed and the sequence of its 18S rDNA is presented. The tapeworms parasitizing the genera Pan, Pongo, Homo and Hylobates from Muséum National d'Histoire Naturelle, Paris and from Muséum d´Histoire Naturelle, Genève are also presented. The validity of B. satyri is confirmed. B. satyri (BSA) differs from the most similar species Bertiella studeri (BSTU) in the following characteristics: (1) testes number, BSTU 300-400; BSA 116-124, (2) genital opening, BSTU regularly alternate; BSA irregularly alternate, (3) Cirrus-sac, BSTU short, 0.250-0.320, does not reach excretory ducts; BSA long, 0.630 × 0.495, reaches excretory ducts, (4) egg size, BSTU 0.053-0.060; BSA 0.030-0.051, (5) host BSTU Pan troglodytes, Africa; BSA Pongo pygmaeus, P. abelii, Indonesia (Borneo, Sumatra). Both species differ according to our material and the name B. satyri (Blanchard, 1891) is resurrected.

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.

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.