Strongyle Faecal Egg Counts Research Articles

Strongyle egg shedding and egg reappearance periods in horses with pituitary pars intermedia dysfunction

Pituitary pars intermedia dysfunction (PPID) is the most common endocrine disorder of older horses. Immune dysfunction in horses with PPID could increase susceptibility to infectious diseases, including strongyle infections; however, few data are available. The aim of this study was to determine if horses with PPID had increased strongyle faecal egg counts (FEC) compared with control horses, over a fourteen-week period in Victoria, Australia. Clinical signs and plasma adrenocorticotropic hormone (ACTH) concentrations were used to categorise horses into PPID (n=14) or control (n=31) groups. Faecal samples were collected for FEC determination prior to anthelmintic treatment, and fortnightly post-treatment for each horse. Generalised linear mixed modelling, using a gamma distribution, was used to compare differences between groups in the repeated measures study. The confounding variable of age was controlled for as a fixed effect. Following anthelmintic treatment, mean FEC was greater for the PPID group compared to the control group on day 56 (405 ± 756 eggs per gram [EPG] vs 40 ± 85 EPG, p=0.05) and day 70 (753 ±1598 EPG vs 82 ±141 EPG, p=0.04). There were no differences in mean FEC between groups on days 84 and 98. Cumulative FEC (day 14 to day 98) was significantly greater for the PPID horses than control horses (2118 ± 4016 EPG vs 798 ± 768 EPG, p<0.0001). Group egg reappearance period was shorter for PPID horses (day 56 post-anthelmintic treatment) compared to control horses (day 70) and 30% of the PPID horses reached a FEC threshold of >200 EPG on day 42, compared to 0% of control horses (p=0.02). These results suggest that the rate of a re-established patent infection between groups could be different due to a comprised immune response in PPID horses or differences in the host-parasite relationship regarding encysted stage larvae. However, despite differences between groups, some horses with PPID consistently had no detectable or low FEC (<200 EPG) during the study period. These findings highlight the importance of individual FEC monitoring to determine if anthelmintic treatment is required, in line with sustainable parasite management practices.

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 i) to assess 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.

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.

Strongyle faecal egg counts in Swiss horses: A retrospective analysis after the introduction of a selective treatment strategy

The standard parasite management of horses based on regular anthelmintic treatments, now practiced for decades has resulted in a worrying expansion of resistant helminth populations, which may considerably impair control on the farm level. The aim of the present study was to obtain a retrospective (year 2010 – 2016) nationwide analysis of faecal egg count (FEC) data from the Swiss adult horse population, related to horse age and geographic region. Thirteen labs provided a total of 16,387 FEC data of horses aged four to 39 years (average: 13.6 years). The annual number of performed FEC tests increased from 38 to 4,939 within the observation period. Independent of the annual sample size the yearly patterns of the FEC were very similar. Seventy-eight percent (n = 12,840) of the samples were negative and 90 % (n = 14,720) showed a FEC below 200 strongyle eggs per gram (EPG) of faeces. The annual mean strongyle FEC ranged between 60 and 88 EPG with a total mean of 75 EPG. Horses aged 4–7 years showed a significantly (p < 0.00001) higher mean FEC compared with the other age groups, differences were not significant among the older horses. Based on ZIP codes, samples were allocated by 70.0 %, 6.0 % and 0.2 % to the German-, French- and Italian-speaking regions of Switzerland, respectively. With 222 EPG the mean FEC in the French part of Switzerland was significantly higher (p < 0.05) than in the German-speaking region (60 EPG). Eggs of Parascaris spp., anoplocephalids and Strongyloides westeri were found in 0.36 %, 0.32 % and 0.01 % of the samples, respectively. Based on 3,813 questionnaire feedbacks from owners in 2017 covering a total of 12,689 horses, sixty-eight percent (n = 8,476) were dewormed without diagnosis, two percent (n = 240) were not dewormed at all, whereas for 30 % (n = 3,721) the selective anthelmintic treatment (SAT) concept was applied. The SAT implementation rate differed significantly (p < 0.0005) between regions, with 33 %, 20 % and 25 % for the German-, French- and Italian-speaking areas, respectively. The rate of horses spending 16–24 h on pasture per day was significantly higher in the French-speaking region compared to the German-speaking part of Switzerland (p < 0.0001). In addition, pasture hygiene was practiced at a significantly lower rate in the French-speaking part compared to the German- and Italian-speaking regions (both p < 0.0001). Overall, the shift towards the SAT-concept represents a very promising development with respect to mitigating the further spread of anthelmintic resistance.

Comparison of ovine faecal Strongyle egg counts from an accredited laboratory and a rapid, on-site parasite diagnostic system utilising a smartphone app and machine learning

Traditional treatment for gastrointestinal helminths in grazing livestock often involves untargeted, metaphylactic blanket treatment of animals with anthelmintics. As a result, resistance to anthelmintic drugs has become a significant issue for farmers and veterinarians worldwide, impacting farm profitability and animal welfare. Faecal egg counts (FECs) are an important diagnostic test to combat further anthelmintic resistance as they enable practitioners to better distinguish between animals that require treatment and those that do not. FECs are labour-intensive, time-consuming and require trained personnel to process the samples and visually identify the parasite eggs. Consequently, the time between sample collection, transport, analysis, results, and treatment can take days. This study aimed to evaluate a rapid, on-site parasite diagnostic system utilising a smartphone app and machine learning in terms of its capability to provide reliable egg counts while decreasing the turnaround time for results associated with outsourcing the analysis. A total of 105 ovine faecal samples were collected. Each sample was homogenised and split equally between two containers. One container per sample was processed using the on-site, app-based system, the second container was sent to an accredited laboratory. Strongyle egg counts were conducted via video footage of samples by the system’s machine learning (ML) and a trained technician (MT) and via microscopic examination by an independent laboratory technician (LAB). Results were statistically analysed using a generalised linear model using SAS® (Version 9.4) software. The ratio of means was used to determine non-inferiority of the ML results compared to the LAB results. Both system egg counts (ML and MT) were higher (p < 0.0001) compared to those obtained from the laboratory (LAB). There was no statistically significant difference between the ML and MT counts. The app-based system utilising machine learning has been found to be non-inferior to the accredited laboratory at quantifying Strongyle eggs in ovine faecal samples. With its quick result turnaround, low outlay cost and reusable components, this portable diagnostic system can help veterinarians to increase their testing capacity, perform on-farm testing and deliver faster and more targeted parasite treatment to combat anthelmintic resistance.

Estimating the Prevalence and Factors Affecting the Shedding of Helminth Eggs in Irish Equine Populations.

Gastrointestinal helminths are ubiquitous in horse populations across the world. Intensive anthelmintic treatments have succeeded in controlling some of the pathogenic effects of these parasites. However, the success of anthelmintic drugs has been threatened by the development of widespread resistance to those most commonly used. To develop improved control strategies, information on helminth distribution patterns is needed, which can be obtained by identifying animals regarded as high egg shedders and taking age, gender, and other risk factors into account. The aim of this study was to determine the prevalence of helminth infection in the Irish equine population using faecal egg counts and to evaluate the effects of risk factors on these faecal egg counts. For the 2700 horses that were included in the study, the prevalence of gastrointestinal helminth infection was 52.40%, 4.22%, 2.59%, and 0.89% for strongyle species, Parascaris spp., Anoplocephala spp., and Strongyloides westeri, respectively. Overall, strongyle faecal egg counts from 159 farms averaged 250.22 eggs per gram. Both age and season had significant effects on strongyle egg shedding. In conclusion, this study revealed high prevalence of strongyle worm infection in horses on Irish farms, which highlights the need to optimize and develop good management practices and strategic deworming.

Anthelmintic resistance of horse strongyle nematodes to fenbendazole in Lithuania

BackgroundControl of strongyle infections presents a global challenge for horse practitioners due to the development of anthelmintic resistance (AR), however comprehensive information on AR in Lithuania is still lacking. The aim of this study was to assess the current situation of fenbendazole (FBZ) AR in horses at stable level in Lithuania.ResultsFaecal samples from 121 horses from six stables were examined using the Mini-FLOTAC method. Of these, 89 horses met the inclusion criteria that included strongyle faecal egg counts (FEC) exceeding 200 eggs per gram (EPG). Faecal egg count reduction tests (FECRTs) were performed in these. AR was evaluated at horse stable level based on faecal egg count reduction (FECR) and the lower limit of the 95% credible interval (LLCI) using the Bayesian hierarchical model. This study confirmed that strongylids (Cyathostominae (CYA)) resistant to FBZ are pervasive in Lithuania. FBZ was ineffective in three of the six stables (FECR 77.1–79.0%; 49.8–99.8 LLCI), was suspected to be ineffective in one stable (FECR 93.6%; 85.4–100 LLCI) and was effective (FECR 99.8–100%; 99.8–100 LLCI) in two stables. FEC showed a significant (P < 0.01) difference between the treatment and control groups. Only CYA larvae were detected in larval cultures derived from strongyle-positive faecal samples collected 14 days after treatment of a test group with FBZ.ConclusionThis in vivo study showed that resistance to FBZ in the treatment of strongyle nematodes is prevalent in horse stables in Lithuania. These findings should guide the implementation of more sustainable management of strongyle infections in horses in Lithuania.

Associations between MHC class II variation and phenotypic traits in a free-living sheep population.

Pathogen-mediated selection (PMS) is thought to maintain the high level of allelic diversity observed in the major histocompatibility complex (MHC) class II genes. A comprehensive way to demonstrate contemporary selection is to examine associations between MHC variation and individual fitness. As individual fitness is hard to measure, many studies examine associations between MHC variation and phenotypic traits, including direct or indirect measures of adaptive immunity thought to contribute to fitness. Here, we tested associations between MHC class II variation and five phenotypic traits measured in free-living sheep captured in August: weight, strongyle faecal egg count, and plasma IgA, IgE and IgG immunoglobulin titres against the gastrointestinal nematode parasite Teladorsagia circumcincta. We found no association between MHC class II variation and weight or strongyle faecal egg count. We did, however, find associations between MHC class II variation and immunoglobulin levels which varied with isotype, age and sex. Our results suggest associations between MHC and phenotypic traits are more likely to be found for traits more closely associated with pathogen defence than integrative traits such as bodyweight and highlight the association between MHC variation and antibodies in wild populations.

Anthelmintic resistance of horse strongyle nematodes to ivermectin and pyrantel in Lithuania

BackgroundWith intensive use of anthelmintic drugs in recent decades, anthelmintic resistance (AR) in horse nematodes is becoming a growing issue in many countries. However, there is little available information about the parasites, treatment practices or AR in the horse population in Lithuania. The aim of this study was to assess the current situation of AR on horse farms in Lithuania. The study was conducted in 25 stables on horses with a strongyle faecal egg count (FEC) of ≥ 200 eggs per gram. A faecal egg count reduction test (FECRT) was performed on each farm after administration of ivermectin (IVM) or pyrantel (PYR).ResultsThe efficacy of IVM was comparatively high, with 98.8% of 250 horses having a zero egg count 14 days after treatment. Two conditions were used to interpret the FECRT results for PYR: firstly, resistance was determined when FECR was < 90% and the lower 95% confidence interval (LCL) was < 80%, and secondly when in addition the upper confidence level (UCL) was < 95%. Under the first condition, resistance against PYR was found in five stables (25% of all tested herds), while when considering the UCL as well, resistance was only detected in two stables (8%). The FEC showed a significant (P < 0.01) difference between the treatment and control groups. Only cyathostomin larvae were detected in larval cultures derived from strongyle-positive faecal samples collected 14 days after treatment of a test group with PYR.ConclusionsThis in vivo study showed that PYR resistance is prevalent on horse farms in Lithuania, while the efficacy of IVM still appears to be unaffected. However, further studies of ivermectin resistance are needed. These findings should guide the implementation of more sustainable management of strongyle infections in horses in Lithuania.

Gastrointestinal nematode infections in goats: differences between strongyle faecal egg counts and specific antibody responses to Teladorsagia circumcincta in Nera di Verzasca and Alpine goats.

Strongylida are gastrointestinal nematodes (GIN) of greatest importance in small ruminants throughout the world. Differences in resistance and resilience to GIN among goat breeds were reported. This study aims to investigate the mechanism underlying the breed-associated differences using a cosmopolitan (Alpine, AB) and an autochthonous (Nera di Verzasca, NV) goat breed. At first, fifteen goats from the same herd (NV = 7, AB = 8) at day 0 were infected with infective larvae (L3) of mixed GIN. From the 15th day post-infection (DPI), individual parasite egg excretion (faecal egg counts, FEC) was performed on all goats, once per week, until the 63rd DPI. Afterwards, in goats under field conditions (30 AB and 30 NV reared on the same farm), individual faecal and blood samples were collected; FEC-specific antibody and PCV levels were explored. In goats with experimental GIN infection, mean eggs per gram of faeces (EPG) values were consistently lower in NV goats. In goats with natural GIN infection, EPG and prevalence values showed high variability in both breeds; among individual variables, breed had a significant influence on EPG. Further, PCV and anti-T. circumcincta IgA levels were influenced by the breed. Lower PCV values were also associated with higher strongyle EPG in AB goats, and anti-T. circumcincta IgA levels were influenced by both strongyle EPG and breed, with IgA levels being higher in AB vs. NV goats and positively associated with EPG. Neither EPG nor breed had any influence on IgE levels. Both studies on experimental and natural infection confirmed that goats of NV are more resistant to infection with gastrointestinal nematodes.

Not playing by the rules: Unusual patterns in the epidemiology of parasites in a natural population of feral horses (Equus caballus) on Sable Island, Canada.

Sable Island, Nova Scotia, Canada hosts one of few natural populations of feral horses (Equus caballus) never exposed to anthelmintics. Coproculture revealed cyathostomes, Strongylus equinus, S. edentatus, and S. vulgaris, with S. equinus (unusually) dominating in adult horses and cyathostomes dominating in young horses (<3 years of age). We examined 35 horses found dead in the springs of 2017 and 2018, as well as fecal samples from live horses in spring (n = 45) and summer 2018 (n = 236) using McMaster fecal flotation and Baermann larval sedimentation on fresh samples, and modified Wisconsin flotation and sucrose gradient immunofluorescent assay for Giardia and Cryptosporidium on frozen samples. Mean strongyle fecal egg counts were 666 eggs per gram (EPG) in dead horses, 689 EPG in live horses in spring, and 1105 EPG in summer; domestic horses are usually treated at counts exceeding 200 EPG. Adult horses (unusually) had patent infections with the lungworm Dictyocaulus arnfieldi and ascarids (Parascaris spp.), and in spring, dead horses had 5 times higher odds of having patent ascarid infections than live horses, likely due to malnutrition and corresponding immunodeficiency. Fecal prevalence and intensity of D. arnfieldi and Parascaris spp. were significantly higher in young horses, and in spring versus summer. A higher proportion of fecal samples were positive for strongyle and ascarid eggs using a centrifugal flotation technique on previously frozen feces, as compared to a passive flotation method on fresh feces. Eggs of the tapeworm Paranoplocephala mamillana were present in fecal samples from 28% of live, and 42% of dead, horses in spring. This research represents several new geographic records (S. edentatus, D. arnfieldi, and Eimeria leuckarti), provides insight into unusual patterns of parasite epidemiology in a nutrition-limited environment, and has conservation and biosecurity implications for this unique equine population, as well as for parasite management in domestic horses.

Assessment of targeted selective treatment criteria to control subclinical gastrointestinal nematode infections on sheep farms

Control of sheep gastrointestinal nematode (GIN) infections mostly relies on the use of anthelmintics. Refugia-based control strategies as targeted selective treatments (TST) can delay anthelmintic resistance development, but the optimal decision criteria for selecting individuals to be treated in subclinical infection scenarios remain unclear. The present study aimed to evaluate the suitability of body condition score (BCS) and faecal egg counts (FEC) as treatment indicators and to determine their optimized threshold values for treatment in TST by determining the relationships of BCS, FEC and anthelmintic treatment with several productive parameters in pre-mating and pre-partum periods at an individual level. Deworming in pre-mating period increased BCS gain, but its magnitude was directly associated with strongyle FEC before treatment. Deworming also increased fertility in ewes with BCS < 2.75 and the proportion of lambing ewes that got pregnant during the first ovulation cycle. Nevertheless, treatment did not yield productive benefits in ewes with higher BCS values. On the other hand, deworming in the pre-partum lowered lamb peri-partum mortality and increased lamb weight at birth and the growth of lambs during lactation, especially in lambs born from ewes with strongyle FEC > 400 epg before treatment. These results showed that FEC and especially BCS can be potential decision criteria for the implementation of TST in these types of scenarios. The TST scheme derived from the present results on the control of GIN infections should include anthelmintic treatment of ewes with BCS lower than ≈ 3 approximately five weeks before mating and lambing. In the pre-lambing period, treatment may be unnecessary if flock mean strongyle FEC is lower than ≈ 200 epg, as the proportion of ewes with individual FEC > 400 epg would be very low. The results suggest that implementation of this TST scheme would provide benefits, such as the improvement of productivity, a rational management of parasites in refugia, and preservation of future efficacy of anthelmintics, in comparison to traditional deworming schemes.

Managing anthelmintic resistance in cyathostomin parasites: Investigating the benefits of refugia-based strategies

Selective anthelmintic therapy has been recommended as a sustainable strategy for cyathostomin control in horse populations for several decades. The traditional approach has been to determine strongyle fecal egg counts (FEC) for all horses, with treatment only recommended for those exceeding a predetermined threshold. The aims are to achieve a reduction of overall egg shedding, while leaving a proportion of the herd untreated, which lowers anthelmintic treatment intensity and reduces selection pressure for development of anthelmintic resistance. This study made use of the cyathostomin model to evaluate the influence of treatment strategies with between 1 and 8 yearly treatment occasions, where either 1) all horses were treated, 2) a predetermined proportion of the herd remained untreated, or 3) horses were treated if their FEC exceeded thresholds between 100 and 600 strongyle eggs per gram. Weather data representing four different climatic zones was used and three different herd age structures were compared; 1) all yearlings, 2) all mature horses 10–20 years old, and 3) a mixed age structure of 1–20 years of age. Results indicated a consistent effect of age structure, with anthelmintic resistance developing quickest in the yearling group and slowest among the mature horses. Development of anthelmintic resistance was affected by treatment intensity and selective therapy generally delayed resistance. Importantly, the results suggest that the effects of selective therapy on resistance development are likely to vary between climatic zones and herd age structures. Overall, a substantial delaying of resistance development requires that the average number of treatments administered annually across a herd of horses needs to be about two or less. However, results also indicate that an age-structured prioritisation of treatment to younger horses should still be effective. It appears that a ‘one-size-fits-all’ approach to the management of anthelmintic resistance in cyathostomins is unlikely to be optimal.

The application of faecal egg count results and statistical inference for clinical decision making in foals

This study investigated the impact of variability in Parascaris spp. and strongyle faecal egg counts (FEC) from foals on treatment decision-making and detection of a patent infection. A single faecal sample was collected once daily for three days from 53 foals and a FEC was performed on three separate portions of each sample (total of nine egg counts per foal). Differences in the decision to administer an anthelmintic using the results of a single count (C1), the mean of three (X¯1–3) or nine counts (X¯1–9) and the upper 5% confidence limit of the gamma confidence interval (CI) of the estimate of the distribution mean (μ) from three (UCL1–3) and nine counts (UCL1–9) were determined for a range of egg count thresholds. The UCL1–9 was used as the best estimate of μ, hypothesis testing for treatment and the comparison of treatment decision-making using C1, X¯1–3, X¯1–9 and UCL1–3. The results of this study demonstrated that a point estimate (C1 or X¯1–3) was of limited value for estimating the distribution mean of egg counts in faeces and there was overall poor agreement in treatment decision-making for individual foals using C1 compared with UCL1–9. Of the foals with C1 of zero eggs per gram, 54% and 47% had Parascaris and strongyle eggs in subsequent counts, respectively. The egg density in faeces is inhomogeneous, resulting in considerable variability in egg count results for an individual foal: between faecal piles, different portions of a faecal pile and days. The use of the negative binomial distribution CI for μ takes this variability into account and is recommended for use when interpreting FEC data from horses.

Wild horse populations in south-east Australia have a high prevalence of Strongylus vulgaris and may act as a reservoir of infection for domestic horses.

Australia has over 400,000 wild horses, the largest wild equid population in the world, scattered across a range of different habitats. We hypothesised that wild horse populations unexposed to anthelmintics would have a high prevalence of Strongylus vulgaris infections. Verminous endarteritis and colic due to migrating S. vulgaris larvae is now absent or unreported in domestic horses in Australia, yet wild horses may pose a risk for its re-emergence. A total of 289 faecal egg counts (FECs) were performed across six remote wild horse populations in south-east Australia, of varying densities, herd sizes and habitats. Total strongyle egg counts ranged from 50 to 3740 eggs per gram (EPG, mean 1443) and 89% (257/289) of faecal samples had > 500 EPG, classifying them as ‘high level shedders’. There were significant differences in mean total strongyle FECs between different locations, habitats and population densities. Occurrence of S. vulgaris was not predictable based on FECs of total strongyle eggs or small (<90 μm) strongyle eggs. A high prevalence of S. vulgaris DNA in faecal samples was demonstrated across all six populations, with an overall predicted prevalence of 96.7%. This finding is important, because of the ample opportunity for transmission to domestic horses. The high prevalence of S. vulgaris suggests vigilance is required when adopting wild horses, or when domestic horses graze in environments inhabited by wild horses. Appropriate veterinary advise is required to minimize disease risk due to S. vulgaris. Monitoring horses for S. vulgaris using larval culture or qPCR remains prudent. Gastrointestinal parasites in wild horse populations may also serve as parasite refugia, thus contributing to integrated parasite management when facing emerging anthelmintic resistance.

Prevalence of Strongylus vulgaris in horses after ten years of prescription usage of anthelmintics in Sweden

Strongylus vulgaris is considered the most pathogenic nematode parasite of the horse. Frequent deworming programs since the 1970s have reduced the prevalence of S. vulgaris to low levels, but to the price of widespread benzimidazole resistance in the small strongyles (cyathostominae) and ivermectin resistance especially in the equine roundworm Parascaris spp. To slow down the progression of anthelmintic resistance in Sweden, horse anthelmintics were made prescription only medicine in 2007 and selective therapy principles were introduced. This means that only individuals with high egg excretion or clinical signs of helminth infection were treated instead of blanket treatment of all horses on a farm. The aims of this study were to investigate the prevalence and risk factors associated with S. vulgaris infection in Sweden ten years after the introduction of a selective therapy regime. A total of 529 faecal samples from 106 farms were collected during March to June in 2016 and 2017. A web-based questionnaire was used to collect information about deworming routines. Strongyle faecal egg counts (FEC) were performed by McMaster and presence of S. vulgaris was demonstrated with a specific PCR on individual larval cultures. Results were analysed by mixed logistic (S. vulgaris prevalence) or linear (FEC) regression models, where farm was included as random factor. The overall prevalence of S. vulgaris at individual and farm levels was 28% and 61%, respectively. We observed a 2.9 increased odds risk of S. vulgaris infection on farms that based their treatment on strongyle FEC only as compared to farms that complemented strongyle FECs with larval cultures or dewormed regularly, 1–4 times per year, without prior diagnosis. We found no association between the prevalence of S. vulgaris and strongyle FEC level, horse age, geographical region or signs of colic. The prevalence of S. vulgaris was 25% in horses shedding ≤150 eggs per gram. Thus horses with low strongyle FECs that are left untreated could be an important source of S. vulgaris infection. This may be an important reason for the approximately three-fold increase in S. vulgaris prevalence since 1999 in Sweden. However, our combined results indicate that selective therapy based on a combination of strongyle FECs and larval cultivation was not associated with an increased risk of S. vulgaris infection. Still, S. vulgaris needs to be monitored continuously and should be taken into careful consideration when the treatment frequency is reduced.

Factors associated with strongyle infection in goats at the individual and farm level.

OBJECTIVE To identify factors associated with strongyle infection and parasite reduction strategies associated with low strongyle fecal egg counts (FECs) in goats on farms in North Carolina. DESIGN Cross-sectional study. ANIMALS 631 adult goats on 52 farms in North Carolina. PROCEDURES Participating farms were visited to collect fecal samples from goats and administer a survey regarding goat, environmental, and management factors. The McMaster technique was used to determine strongyle FEC for each sample. Univariate followed by multivariate modeling was performed to identify factors associated with FEC at the farm and individual goat level. RESULTS Multivariate analysis controlling for several other factors and multiple comparisons revealed that farms on which no anthelmintic drugs had ever been used had the lowest mean FECs, compared with farms on which specific strategies for parasite control were used; no other variables were significant. For individual goat FEC, significant variables included goat breed, breed type, owner-defined purpose, daily dietary protein intake, and fecal coccidia score. In particular, companion goats (vs meat or dairy goats) had the lowest FECs. Higher dietary protein intake and coccidia scores were associated with higher FECs. Among females, goats that had kidded in the last 6 weeks had the highest FECs. CONCLUSIONS AND CLINICAL RELEVANCE Various factors were identified that appeared to influence the likelihood of strongyle infection in goats. The finding that farms with no history of anthelmintic use had the lowest mean FECs suggested that a focus on preventative measures could reduce the need for anthelmintic drugs and, by extension, lessen the opportunity for the development of anthelmintic resistance.

Fecal strongyle egg counts in horses with suspected pre-clinical pituitary pars intermedia dysfunction before and after treatment with pergolide

Pituitary pars intermedia dysfunction (PPID) has been associated with diminished immune response in aged horses. This prospective study hypothesised that this may result in increased strongyle egg shedding in affected animals and that horses treated with pergolide would have reduced fecal egg counts (eggs per gram, EPG) compared to placebo-treated animals. Adrenocorticotropic hormone (ACTH) concentrations and EPG were tested in 48 horses. There were no significant differences in baseline EPG between horses with pre-clinical PPID and healthy controls. There was no significant difference in EPG between horses with PPID after treatment with pergolide and placebo-treated animals. Using EPG as a marker of immune function, these results did not support a proposed decrease in immune function in horses with pre-clinical PPID.

Helminth egg excretion in horses kept under tropical conditions—Prevalence, distribution and risk factors

Increasing levels of anthelmintic resistance observed in equine cyathostomin parasites have led to recommendations of selective anthelmintic treatment strategies to lower the selection pressure favoring resistant populations. This principle is based on determining strongyle fecal egg counts from all herd members, and treating those exceeding a predetermined treatment cutoff. However, epidemiological information is lacking from horses kept under tropical conditions, where parasite burdens may be of a different composition and magnitude compared to those of horses kept under temperate climate conditions. The aim of the present work was to characterize the strongylid fauna in horses kept in tropical Camagüey, Cuba and identify risk factors associated with strongylid and ascarid egg counts. A total of 396 horses from eight different establishments were included in the study. Coprocultures revealed that Strongylus vulgaris and cyathostomins, sensu lato, were detected in all of those establishments. Prevalence and mean value of strongylid eggs per gram of feces were 97% and 1436, respectively. Eggs of Parascaris spp. were observed in 10% of horses. A multivariate mixed linear model identified sex (p=0.022), month (p=0.044), operation type (p=0.037) and time since last deworming (p<0.001) to be significantly associated in with the magnitude of strongylid fecal egg counts. A multivariate logistic regression identified horses less than two years of age (p=0.010) and horses not receiving anthelmintic treatment (p<0.001) to be significantly more likely to harbor Parascaris spp. parasites. The high magnitude and prevalence of strongylid fecal egg counts observed and the common occurrence of S. vulgaris suggest that strongylid parasite burdens are substantially different from those typically observed in managed equines kept under more temperate conditions.

The effect of sericea lespedeza on strongyle fecal egg counts in mature horses

The effect of sericea lespedeza on strongyle fecal egg counts in mature horses