A retrospective study of the prevalence in equine postmortems of cranial mesenteric arteritis caused by Strongylus vulgaris in Alberta (2010 to 2022).

Background: Strongylus vulgaris is one of the most pathogenic nematodes affecting equids. Larval migration through the cranial mesenteric artery (CMA) with attendant arteritis and thromboembolism can result in fatal non-strangulating intestinal infarction. Once considered a historical disease, recent studies have described the reemergence of this pathogen in several European countries; however, little is known of the current prevalence of S. vulgaris in the Canadian horse population. Objective: To determine the prevalence of active S. vulgaris cranial mesenteric arteritis in horses submitted for postmortem examination to the Diagnostic Services Unit (DSU) at the University of Calgary Faculty of Veterinary Medicine. Animals and procedure: We conducted a retrospective review of all equine postmortem cases submitted to the DSU between July 1, 2010 and June 30, 2022. Over 12 y, 510 horses > 2 mo of age from Alberta were submitted to the DSU for necropsy. Active cases were defined as those with endarteritis and thrombosis in the CMA or its branches. Those cases with only intimal scarring of the CMA were classified as historical. Results: The prevalence of all CMA lesions (both historical and active) over the study period was 17.3% (88/510). Active S. vulgaris cranial mesenteric arteritis was documented in 6.1% (31/510) of equine postmortems and the sequelae of verminous arteritis were the cause of euthanasia or death in 1.5% (8/510) of the cases submitted. Conclusion and clinical relevance: Even after historically intense efforts to eradicate this parasite, the continued effects of S. vulgaris are demonstrated by the results of this study. Strongylus vulgaris should not be regarded as a parasite of the past and verminous arteritis remains an important differential diagnosis for horses in western Canada presenting with mild colic or dull demeanor and anorexia of duration > 24 h. Furthermore, S. vulgaris should be taken into careful consideration when implementing antiparasitic control strategies. Practitioners should remain current on prevention, diagnosis, and treatment of this potentially reemerging and fatal equine disease.

Étude rétrospective de la prévalence lors d'autopsies équines de l'artérite mésentérique crâniale causée par Strongylus vulgaris en Alberta (2010 à 2022). Contexte: Strongylus vulgaris est l'un des nématodes les plus pathogènes affectant les équidés. La migration des larves à travers l'artère mésentérique crâniale (CMA), accompagnée d'artérite et de thromboembolie, peut entraîner un infarctus intestinal non étranglant mortel. Autrefois considérée comme une maladie historique, des études récentes ont décrit la réémergence de cet agent pathogène dans plusieurs pays européens; cependant, on sait peu de choses sur la prévalence actuelle de S. vulgaris dans la population équine canadienne. Objectif: Déterminer la prévalence de l'artérite mésentérique crâniale active à S. vulgaris chez les chevaux soumis pour examen post mortem au Diagnostic Service Unit (DSU), College of Veterinary Medicine, University of Calgary. Animaux et procédure: Nous avons effectué un examen rétrospectif de tous les cas post-mortem d'équidés soumis au DSU entre le 1er juillet 2010 et le 30 juin 2022. Sur 12 ans, 510 chevaux âgés de plus de 2 mois de l'Alberta ont été soumis au DSU pour autopsie. Les cas actifs ont été définis comme ceux présentant une endartérite et une thrombose dans la CMA ou ses branches. Les cas présentant uniquement des cicatrices à l'intima de la CMA ont été classés comme anciens. Résultats: La prévalence de toutes les lésions de CMA (anciennes et actives) au cours de la période d'étude était de 17,3 % (88/510). Une artérite mésentérique crâniale active à S. vulgaris a été documentée dans 6,1 % (31/510) des autopsies équines et les séquelles de l'artérite vermineuse ont été la cause de l'euthanasie ou du décès dans 1,5 % (8/510) des cas soumis. Conclusion et pertinence clinique: Malgré des efforts historiquement intenses pour éradiquer ce parasite, les effets continus de S. vulgaris sont démontrés par les résultats de cette étude. Strongylus vulgaris ne doit pas être considéré comme un parasite du passé et l'artérite vermineuse demeure un diagnostic différentiel important pour les chevaux de l'ouest du Canada présentant des coliques légères ou un comportement abattu et une anorexie de durée > 24 h. De plus, S. vulgaris doit être attentivement pris en compte lors de la mise en œuvre de stratégies de contrôle antiparasitaire. Les praticiens doivent rester informés de la prévention, du diagnostic et du traitement de cette maladie équine potentiellement ré-émergente et mortelle.(Traduit par Dr Serge Messier).

Detection of SNPs and benzimidazole resistance in strongyle nematode eggs of horses by allele-specific PCR.

This study was conducted to determine single nucleotide polymorphisms (SNPs) and the benzimidazole (BZ) resistance in strongyle nematode egg populations in horses using molecular techniques. A total of 200 fecal samples were collected from horses in 26 farms in two provinces (Kayseri and Nevsehir) of the Central Anatolia Region of Türkiye between May and August 2022. The flotation method was used to detect strongyle nematode eggs in the fecal samples of the horses. Afterward, strongyle nematode eggs were collected, and the allele-specific polymerase chain reaction (AS-PCR) technique was used to detect the BZ resistance. BZ-susceptible and BZ-resistant PCR products were sequenced to determine single nucleotide polymorphisms (SNPs) in the ß-tubulin isotype 1 gene. The strongyle nematode eggs were determined in 85 (42.5%) out of 200 fecal samples. AS-PCR detected 50.58% (43/85) BZ-resistant (homozygous resistant) and 36.4% (31/85) BZ-susceptible (homozygous susceptible) genes in the strongyle eggs. Both BZ-resistant and BZ-susceptible genes (heterozygous) were determined in 11 samples. BZ-resistant and BZ-susceptible allele frequencies were determined as 57.0% (48.5/85) and 43.0% (36.5/85), respectively. SNPs were detected only in codon 200 of the ß-tubulin isotype 1 gene in four sequenced isolates of the two resistant and two susceptible isolates. This study is the first molecular report on BZ resistance in strongyle nematode eggs in horses in Türkiye. The widespread prevalence of BZ-resistant alleles in equine strongyle nematodes shows the requirement for the immediate usage of other anthelmintics instead of the BZ group drugs for the effective management and control of equine strongyle nematodes.

Prevalence, intensity and risk factors of infestation with major gastrointestinal nematodes in equines in and around Shashemane, Southern Ethiopia.

Prevalence, intensity and risk factors of major gastrointestinal nematode infestation in equines were studied through a cross-sectional survey in 384 equids from October 2013 to April 2014 in and around Shashemane, southern Ethiopia. Three hundred and fifteen equids (82 %) were demonstrated harbouring one or more gastrointestinal (GIT) nematodes using the faecal flotation technique. The prevalence of GIT nematode infestation was 73.4, 85 and 86.5 % for horses, mules and donkeys, respectively. The identified nematodes were strongyle type (73.4 %), Parascaris equorum (21.4 %) and Oxyuris equi (4.4 %). Species of equines had a significant (χ (2) = 9.35, P < 0.01) association with the occurrence of GIT nematode infestation. Donkeys were two times (OR = 2.3, 95 % CI 1.27-4.28, P < 0.01) more likely getting GIT nematode infestation than horses. Moreover, donkeys had the highest mean faecal egg counts (1831.2 egg per gram (EPG)) followed by mules (915.7 EPG) and horses (772.5 EPG). There was a significant association (P < 0.05) between mean EPG and body condition score in each equine species. In conclusion, this study provides information which might help in designing upcoming control strategies to control nematode infestation in equines. Moreover, suitable tropical climatic conditions, low level of management and owners' awareness, and poor animal health services are expected to contribute for high nematode infestation. Therefore, emphasis should be given to awareness creation about the strategic deworming, animal welfare and management.

Strongyle infections and parasitic control strategies in German horses - a risk assessment.

BACKGROUND: As a consequence of the increasing levels of anthelmintic resistance in cyathostomes, new strategies for equine parasite control are being implemented. To assess the potential risks of these, the occurrence of strongyles was evaluated in a group of 1887 horses. The distribution of fecal egg counts (FECs), the frequency of anthelmintic drug use, and the deworming intervals were also analyzed. Between June 2012 and May 2013, 1887 fecal samples from either selectively or strategically dewormed horses were collected at 195 horse farms all over Germany and analyzed quantitatively with a modified McMaster technique. All samples with FEC ≥20 eggs per gram (EPG) were subjected to coproculture to generate third-stage larvae (LIII) for species differentiation. RESULTS: Egg counts were below the limit of detection (20 EPG) in 1046 (55.4%) samples and above it in 841 (44.6%) samples. Strongylus vulgaris larvae were identified in two of the 841 positive samples. Infections with cyathostomes were found on every farm. The most frequently applied anthelmintic was ivermectin (788/50.8%), followed by pyrantel (336/21.6%). The mean time since last treatment was 6.3 months. High-egg-shedding (>500 EPG) strategically dewormed horses (183/1357) were treated, on average, three times/year. The planned treatment date was already exceeded by 72.5% of the high egg-shedders and by 58.1% of the moderate (200-500 EPG) and low egg-shedders (20-199 EPG). CONCLUSIONS: S. vulgaris seems to be rare in Germany and no difference in its frequency has yet been found between selectively treated horses and horses receiving treatment in strategic intervals. However, inconsistent parasite control has been observed. Therefore, to minimize the risks for disease, consistent and efficient parasite control should be implemented.

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

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

Association between large strongyle genera in larval cultures--using rare-event poisson regression.

Decades of intensive anthelmintic treatment has caused equine large strongyles to become quite rare, while the cyathostomins have developed resistance to several drug classes. The larval culture has been associated with low to moderate negative predictive values for detecting Strongylus vulgaris infection. It is unknown whether detection of other large strongyle species can be statistically associated with presence of S. vulgaris. This remains a statistical challenge because of the rare occurrence of large strongyle species. This study used a modified Poisson regression to analyse a dataset for associations between S. vulgaris infection and simultaneous occurrence of Strongylus edentatus and Triodontophorus spp. In 663 horses on 42 Danish farms, the individual prevalences of S. vulgaris, S. edentatus and Triodontophorus spp. were 12%, 3% and 12%, respectively. Both S. edentatus and Triodontophorus spp. were significantly associated with S. vulgaris infection with relative risks above 1. Further, S. edentatus was associated with use of selective therapy on the farms, as well as negatively associated with anthelmintic treatment carried out within 6 months prior to the study. The findings illustrate that occurrence of S. vulgaris in larval cultures can be interpreted as indicative of other large strongyles being likely to be present.

Variation in fecal egg counts in horses managed for conservation purposes: individual egg shedding consistency, age effects and seasonal variation.

Cyathostomins are the most prevalent equine intestinal parasites and resistance has been reported in these nematodes against all 3 licensed anthelmintic classes. Strategies need to be developed that are less dependent upon drugs and more reliant on management-based control. To develop these we need to understand natural transmission patterns better. Here, we analysed longitudinal fecal egg count (FEC) data from 5 pony populations used for conservation purposes. We tested how egg excretion varied amongst populations and individuals, and how this was affected by age and climate. There was evidence for consistency in FECs over time at the individual level; this was generally weak and accounted for <10% of the total variance. Animals <5 years old had higher FECs and there was profound seasonal variation in FECs, with highest levels recorded in spring/summer. Effects of monthly temperature and rainfall explained most, but not all, of the observed seasonal variation and associations between climate measures and FECs were stronger in younger versus adult animals. One population was occasionally treated with anthelmintics and analysis of this population suggested that treatment substantially altered the seasonal dynamics. This paper highlights the variability in strongyle egg excretion amongst individuals and the factors involved in this variation.

Occurrence and control of equine strongyle nematode infections in Prince Edward Island, Canada.

Widespread overuse of anthelmintics has produced a growing population of intestinal parasites resistant to control measures. A paradigm shift in equine parasite control is warranted to prevent continued resistance development and maintain equine health. Small strongyles, which are ubiquitous in horses, are currently the most important intestinal parasites of adult horses. Sustainable management programs consider the variation in egg shedding by individual horses, and varied risks associated with age, use, density, climate, and environment. To develop regional recommendations for Prince Edward Island (PEI), Canada, it is important to first characterize strongyle egg shedding patterns and parasite management practices in use. Study objectives were to conduct a cross-sectional observational survey and risk factor analysis of parasite control programs, strongyle egg shedding and Strongylus vulgaris serology. A total of 339 horses from 40 PEI farms were sampled. Mean farm size was 8 horses and ranged from 2 to 30. Mean horse age was 11.6 years (Std. Dev. =7.2) and ranged from 2 months to 32 years. Mean fecal egg count (FEC) was 322 eggs per gram (EPG) (Std. Dev. =648). On average, 32% (Std. Dev. =16%) of horses shed 80% of strongyle eggs across 32 eligible farms. When considering all horses (n = 313) as one large herd, 18.7% of horses shed 80% of strongyle eggs. Use of FEC was identified in 4.6% of horses at 15% (n = 6) of PEI farms. Reported deworming intervals included 37.4% (n = 123) every 2-3 months and 58% (n = 191) every 3-4 months. Positive S. vulgaris titers were identified in 60% of horses (n = 200). Univariate analysis revealed that months since last deworming, age, and body condition score (BCS) were associated with strongyle shedding. The estimated odds of being in the high FEC category (>500 EPG) was 1.4 (95% CI, 1.1-1.8) times higher when last deworming increased by one month. Under-conditioned (BCS <4.5) horses had 3.6 (95% CI, 1.2-10.6) times odds of being in the higher FEC category than over-conditioned horses. Non-racing horses had 5.4 times odds of having a positive S. vulgaris titer than racehorses. This cross-sectional observational study is the first to report on the occurrence, risk factors and control of equine strongyle nematode infections in PEI, Canada. We conclude that the 80:20 rule can be used to develop control recommendations in PEI. Very few farms in PEI currently use FEC to guide parasite management. These findings provide a basis for future client education and investigations aimed at providing region specific recommendations.

Anthelmintic resistance of horse strongyle nematodes to fenbendazole in Lithuania.

BACKGROUND: Control 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. RESULTS: Faecal 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. CONCLUSION: This 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.

Field tests demonstrating reduced activity of ivermectin and moxidectin against small strongyles in horses on 14 farms in Central Kentucky in 2007-2009.

Efficacy of ivermectin (IVM) and moxidectin (MOX) against small strongyles was evaluated in horses (n=363) in field tests on 14 farms in Central Kentucky between 2007 and 2009. Most of the horses were yearlings but a few were weanlings and mares. The number of horses treated with IVM was 255 and those treated with MOX was 108. Horses on six farms were allotted into two groups. One group was treated with each of the two drugs, whereas horses on the other eight farms were treated with only one of the two drugs--IVM on six farms and MOX on two farms. Strongyle eggs per gram of feces (EPGs) compared to initial use of IVM and MOX returned almost twice as quickly after treatment of horses on all of the farms. IVM has been used much more extensively in this geographical area than MOX. Reduced activity of MOX was evident even on farms with rare or no apparent previous use of MOX but with probable extensive use of IVM.

Observations on development of natural infection and species composition of small strongyles in young equids in Kentucky.

Early development and maturation of species of small strongyles have not been studied extensively. Most information is on the first appearance of strongyle eggs in feces of foals. However, species cannot be determined in this manner because of similarity of the morphological features of the eggs. To determine more definitive knowledge on development and species composition of natural infections of small strongyles, eight equid foals were necropsied and examined at various ages (31 to 92 days of age). The entire contents of the large intestine were examined, and all worms (6,671) recovered were identified. This was done to recover small strongyle specimens in an effort to find the stage of development of the worms for different time periods. The primary interest was to obtain data on the potential prepatent period. A total of 17 species of small strongyles were recovered. The earliest gravid female was Cylicostephanus longibursatus in a 57-day-old foal; then Cylicostephanus goldi was positive at 64 days, Cyathostomum catinatum at 68 days, Coronocyclus coronatus and Cylicostephanus calicatus at 70 days, Coronocyclus labiatus, Cylicocyclus leptostomus, Cylicocyclus nassatus, Cylicostephanus hybridus, and Cylicostephanus minutus at 74 days, and Cylicostephanus bidentatus at 92 days. While it is not known exactly when the foals began eating pasture vegetation (typically they begin to graze a short time after birth) and first ate infective free-living third-stage larvae, the results give an indication of the natural prepatent period of several species of small strongyles. Additional data are presented on the number of worms per foal, distribution of the worms in the parts (cecum, ventral colon, and dorsal colon) of the large intestine, and proportion of species found.

ß-Tubulin genotypes in six species of cyathostomins from anthelmintic-naive Przewalski and benzimidazole-resistant brood horses in Ukraine.

Resistance to benzimidazoles (BZ) in the gastrointestinal nematodes of livestock is characterised by the presence of specific polymorphisms in the ß-tubulin isotype 1 protein, a component of microtubules. The most prevalent polymorphism associated with resistance in nematodes infecting cattle, sheep, and goats is found at codon 200, with minor occurrences of polymorphisms at codons 167 and 198. In the cyathostomins that infect horses, however, a polymorphism at codon 167 appears to be more common than the codon 200 polymorphism. In the present study, a focussed analysis of PCR-amplified ß-tubulin fragments incorporating the above-mentioned three polymorphic sites in isotype 1 and 2 genes in worms of six species of cyathostomins, Cylicocyclus nassatus, Cylicocyclus ashworthi, Cyathostomum catinatum, Cylicostephanus goldi, Cylicostephanus longibursatus, and Coronocyclus coronatus, was performed. Worms were collected from two distinct horse populations, i.e. they were collected from Przewalski horses of the Askania-Nova Biosphere Reserve that had never received any anthelmintic treatment and from brood horses of the Dubrovsky farm where benzimidazole resistance had become established. DNA was extracted and sequenced from three worms of each species and population as well as from pools of 50 male C. nassatus and C. catinatum from both populations. The vast majority of putatively BZ resistance-associated TAC alleles were found at codon 167, compared to codon 200. The former allele occurred in isotype 1 in all six species of the supposedly benzimidazole-resistant cyathostomins from Dubrovsky horses. None of the polymorphisms associated with resistance was found in the corresponding isotype 2 codons nor at codon 198 in any of the six species of cyathostomins (neither single nor pooled worm DNA) from either of the two populations. These findings further support the predominant association of ß-tubulin isotype 1 and therein codon 167 with BZ resistance in cyathostomins.

Coprological prevalence and intensity of helminth infection in working horses in Lesotho.

This study aimed to (1) estimate infection prevalence of strongyle, Oxyuris equi and Parascaris equorum species and the intensity of infection with strongyles in working horses in lowland Lesotho and (2) investigate associations between infection and horse age, sex and owner-reported use of anthelmintics. In a cross-sectional survey, fresh faecal samples were obtained from 305 randomly selected horses and worm egg counts performed using a validated field laboratory kit. Details of anthelmintic use were collected using a standardised face-to-face owner questionnaire. Infection prevalence estimates for each species were calculated, as were infection intensity estimates for strongyle species. Logistic regression was used to investigate associations between exposure variables and infection status/intensity. Prevalence of strongyle infection was 88.2%; 11.8% of horses were not infected and infection intensity was low (1-500 eggs per gram (epg)) in 19.7%, medium (501-1,000 epg) in 19.7%) and high (>1,001 epg) in 48.8%. Decreasing strongyle infection intensity was associated with the use of proprietary equine anthelmintic products (OR 0.18, 95%CI 0.11-0.30, p<0.0001). Prevalence of O. equi infection was 6.2%; the odds of infection with this parasite decreased with increasing horse age (OR 0.84, 95%CI 0.72-0.97, p = 0.02). P. equorum infection prevalence was 21.6%; no statistically significant associations with the investigated exposure variables were found. In conclusion, strongyle infection is endemic in working horses in lowland Lesotho, but proprietary equine anthelmintics assist in managing infection. The apparent lack of age-acquired immunity to P. equorum infection may deserve further investigation. Although O. equi infection is less widespread, measures to protect younger animals may be appropriate.

Strongylus vulgaris: Infection rate and molecular characterization from naturally infected donkeys at Sadat City, Egypt.

Strongylus vulgaris has high pathogenicity to equines. It causes aneurysm and thrombosis in the arteries particularly an anterior mesenteric artery, that is fatal to equines. In this study, we aimed to diagnose microscopically the natural infection of donkeys with Strongylus vulgaris from Sadat City, Minoufiya Governorate, Egypt. Fecal egg culture was used after the diagnosis of strongyle eggs to identify the species. Hematological and biochemical parameters were assessed. Adult worms were collected after post mortem examination of the infected animal. The sequence of ITS-2 was used to confirm the species of the parasite. The infection rate was 15.85% using the microscopical examination. The larval culture confirmed the infection with strongyle eggs as Strongylus vulgaris larvae. The sequence of ITS-2 was highly identical (about 95%) to sequences from Germany, China, and Turkey and occurred in the same genetic clade with the sequence from Germany. In conclusion, the study presented the diagnosis, the changes in the hematological and biochemical parameters in the infected animals, and the genetic characterization of Strongylus vulgaris from Sadat City, Minoufiya Governorate Egypt for the first time.

Eficacy of ivermectin, moxidectin and febendazole in equine in Brazil.

The objectives of the present study were to evaluate the efficacy of three anthelmintic drugs, i.e. fenbendazole, ivermectin and moxidectin; to determine the genera and species of the most abundant strongyles; and to investigate parasite control measures used in herds of horses in the western region of the state of São Paulo, Brazil. This study was onducted between February and December 2013 on 10 farms in this region. Coprological evaluations were conducted for counting the numbers of eggs per gram of feces (EPG) and coprocultures were made in order to identify third-stage larvae (L3) of strongyles. Parasite control measures were investigated by surveying each farm's management and characteristics. A fecal egg count reduction test (FECRT) was used to determine the anthelmintic efficacy based on EPG count results before and after treatment. The FECRT showed that anthelmintic resistance to fenbendazole was present and that ivermectin and moxidectin had high effectiveness in the western region of the state of São Paulo. Identification of L3 revealed that there was high prevalence of cyathostomins among strongyle larvae. The highest prevalence of Strongylus vulgaris occurred on farms where the intervals between deworming were long. The questionnaire applied showed that ivermectin was the drug most used among these farmers.

Compilation of 29 years of postmortem examinations identifies major shifts in equine parasite prevalence from 2000 onwards.

Horses are infected by a wide range of parasite species that form complex communities. Parasite control imposes significant constraints on parasite communities whose monitoring remains, however, difficult to track through time. Postmortem examination is a reliable method to quantify parasite communities. Here, we compiled 1,673 necropsy reports accumulated over 29 years, in the reference necropsy centre from Normandy (France). The burden of non-strongylid species was quantified and the presence of strongylid species was noted. Details of horse deworming history and the cause of death were registered. Building on these data, we investigated the temporal trend in non-strongylid epidemiology and we determined the contribution of parasites to the deaths of horses throughout the study period. Data analyses revealed the seasonal variations of non-strongylid parasite abundance and reduced worm burden in race horses. Beyond these observations, we found a shift in the species responsible for fatal parasitic infection from the year 2000 onward, whereby fatal cyathostominosis and Parascaris spp. infection have replaced cases of death caused by Strongylus vulgaris and tapeworms. A concomitant break in the temporal trend of parasite species prevalence was also found within a 10 year window (1998-2007) that has seen the rise of Parascaris spp. and the decline of both Gasterophilus spp. and tapeworms. A few cases of parasite persistence following deworming were identified, which all occurred after 2000. Altogether, these findings provide insights into major shifts in non-strongylid parasite prevalence and abundance over the last 29 years. They also underscore the critical importance of Parascaris spp. in young equids.

Evaluation of the effectiveness of programs combating the invasions of strongyles (Strongylidae) in horses in selected stables of Western Pomerania

The emergence of drug resistance among parasites is a side effect of the common use of chemotherapeutic agents in horses. Combating parasites typically involves routine deworming treatments twice a year (before and after the grazing season). However, in grazing farming this treatment may be insufficient. The aim of the study was to evaluate the effectiveness of programs to combat the invasion of strongyles (Strongylidae) in horses in the selected stables of Western Pomerania. Coprological examination was conducted in 85 horses from three stables located in Western Pomerania. Horses from all three stables remained in the pastures in the period from spring to late autumn, and deworming treatment was performed twice. The examination of horses has found nematodes of the family Strongylidae. The average prevalence of infection in horses in the studs tested was 36.16% for Strongylinae, and 58.49% for Cyathostominae. Administration of the medication twice did not eradicate the invasion of strongyles in the horses investigated. A significant reduction of strongyle invasion was observed directly after treatment, followed by rapid reinvasion. It appears necessary to monitor the effectiveness of deworming treatments by performing parasitological examination of feces. The participating stables should develop and implement new strategies to combat parasitic invasions in horses that will be adapted to the environmental conditions (the life cycle of parasites).

Correlation between fecal egg count, presence of Strongylus vulgaris, and body score of feral horses on Fort Polk, Louisiana.

Approximately 700 feral horses, dubbed "trespass horses" by the United States Army, occupy Fort Polk, Louisiana and the surrounding Kisatchie National Forest. These horses are considered a nuisance and hazard, and the military is seeking to remove the horses via adoption. The aim of this research was to evaluate the fecal egg count (FEC), body condition score (BCS), and the presence of Strongylus vulgaris within this previously unstudied horse population prior to removal. The feral horse data was compared to domestic horses living on a single farm in the same area. A modified McMaster FEC, Henneke body scoring via photography, and PCR were used to evaluate 10 domestic horses and 28 feral horses. A significantly higher FEC was identified for feral horses when compared to domestic horses (p = 0.004), and 69.2% of feral horses were positive for S. vulgaris while all domestic horses tested negative. Additionally, no correlation was found between FEC and BCS for domestic (p = 0.213) or feral (p = 0.099) horses, and no association was found between FEC and S. vulgaris presence (p = 0.21) or BCS and S. vulgaris presence (p = 0.52). This study provides insight into S. vulgaris and strongyle prevalence in a previously unstudied group of horses and indicates a need for anthelmintic treatment and monitoring of the feral horses once they are adopted.

Risk factors associated with strongylid egg count prevalence and abundance in the United States equine population.

Equine strongyle parasites are considered ubiquitous in grazing equids across the world, and cyathostomin parasites are known pathogens causing well-described disease complexes in horses. Decades of intensive anthelmintic treatments have led to anthelmintic resistance in cyathostomins, and current recommendations are to lower treatment intensity and base control strategies on fecal egg count surveillance. Little is known about risk factors associated with strongyle parasite egg shedding patterns in the United States equine population, as the most recent national survey was conducted 20 years ago. The present study was carried out as part of the National Animal Health Monitoring Systems (NAHMS) Equine 2015-2016 study. The aims were to describe strongyle parasite egg shedding patterns in the United States equine population and identify risk factors associated with prevalence and egg count magnitude. Data were collected from equine operations in 28 states via questionnaires and fecal samples submitted to a parasitology research laboratory for fecal egg count analysis and the data gathered underwent comprehensive statistical analyses. Though region and season were related, overall, the summer months and the fall in the southeast tended to have the greatest odds of presence of strongyles eggs on a FEC. Generally, equids resident in the Western region (Arizona, California, Colorado, Montana, Oregon, and Wyoming) had significantly lower strongyle prevalence, no matter the season, as well as a markedly different distribution between strongyle egg shedding levels (p = 0.0005). Overall, egg counts were over-dispersed with about 27% of equids (95% Confidence Interval (CI): 20-34%) contributing 80% of the egg output. Pasture history was significantly associated with strongyle egg prevalence (p = 0.0003) and egg shedding levels (p = 0.0063) with daily access in the previous 30 days being associated with higher odds of presence and greater median egg count levels. Equid gender was significantly associated with strongylid presence (p = 0.0081) and egg count level (p = 0.0008), with male equids having significantly lower odds and median egg counts than female equids, and age was significantly negatively associated with strongylid prevalence (p < 0.0001). Time since last deworming was significantly positively associated with prevalence of strongyle eggs, and this was dependent on the class of dewormer used (p = 0.0086), with equids treated with macrocyclic lactone class of drugs having lower odds of strongyle egg presence at 120 days since the last deworming. These data provide useful insights into strongylid egg shedding patterns in the United States equine population, and they can help refine parasite control recommendations depending on region, pasture access, and age distribution.

Management practices associated with strongylid parasite prevalence on horse farms in rural counties of Kentucky.

Anthelmintic resistance among cyathostomin parasites is a wide-spread problem. The parasite control guidelines written by the American Association of Equine Practitioners (AAEP) encourages the preservation of anthelmintic efficacy by reducing treatment frequency, using targeted deworming, and implementing environmental management practices. While there is knowledge regarding parasite management practices of affluent horse farms in the United States, surveys rarely explore the rural and underserved regions. The purpose of this study was to observe the management practices of horse farms in rural regions Kentucky, including working Amish farms, and determine factors associated with strongyle prevalence. A total of 160 horses among 38 owners from 28 different farms were enrolled in this study. A questionnaire survey regarding equine information, farm management, and deworming history was performed with each owner. Fecal samples were collected to determine fecal egg counts, perform coprocultures for subsequent strongyle larvae identification, and Strongylus vulgaris specific PCR. Serum samples were collected for the S. vulgaris antibody specific ELISA. The mean number of deworming treatments given in the last year was 2.1 with a 95% confidence interval of 1.9-2.3 with ivermectin being the most common active used. Statistical analysis showed horses treated within the last three months with a macrocylic lactone (ML) drug had significantly lower egg counts than horses treated with a ML 7-9 months ago (p = .0005). Despite the AAEP recommendations to reduce the overall number of treatments by using a surveillance-based approach and to no longer rotate treatments, only 17 horses reportedly had a fecal sample submitted for a fecal egg count and 65 horses were dewormed in a rotational manner. Horses whose owners utilized an informative deworming source (i.e., veterinarian, internet, magazine, local feed store) also had significantly lower counts (p = .0026). All coprocultures were negative for S. vulgaris while five horses were PCR positive. Interestingly, 95 horses tested ELISA positive for S. vulgaris. The strongyle egg counts of the working Amish horses were not significantly different from the other horses in this study and deworming practices including the use of efficacious drugs and low treatment frequencies were in accordance with the AAEP guidelines. This study was the first to summarize deworming management practices of rural regions in Kentucky, including a working Amish community. Overall, horse owners employed deworming practices recommended by the AAEP, however rotational deworming is still commonly implemented and fecal egg counts are rarely used.