Metabarcoding study to reveal the structural community of strongylid nematodes in domesticated horses in Thailand.

BACKGROUND: Mixed strongylid infections significantly impact equine health and performance. Traditional microscopy-based methods exhibit limitations in accurately identifying strongylid species. Nemabiome deep amplicon sequencing approach previously succeeded in describing the strongylid communities in livestock including equids. However, there are no available studies that describe the structural communities of strongylid parasites in horses in Thailand. Therefore, this study was undertaken encompassing the ITS-2 rDNA metabarcoding assay to characterize strongylid species within horse fecal samples collected from a cohort of yearlings at the largest domesticated stud farm in Thailand. In addition, to investigate the capability of ITS-2 rDNA in assessing the phylogenetic relationships among the identified strongylid species. RESULTS: The study identified 14 strongylid species in the examined equine populations, each with varying prevalence. Notably, Cylicocyclus nassatus and Cylicostephanus longibursatus were identified as the predominant species, with Strongylus spp. conspicuously absent. The phylogenetic analysis of 207 amplicon sequence variants (ASVs) displayed a complex relationship among the investigated cyathostomin species, with some species are positioned across multiple clades, demonstrating close associations with various species and genera. CONCLUSION: The ITS-2 nemabiome sequencing technique provided a detailed picture of horse strongylid parasite species in the studied population. This establishes a foundation for future investigations into the resistance status of these parasites and enables efforts to mitigate their impact.

Patterns of Equine Small Strongyle Species Infection after Ivermectin Intervention in Thailand: Egg Reappearance Period and Nemabiome Metabarcoding Approach.

The indiscriminate use of anthelmintics to control parasitic nematodes in horses has led to the emergence of anthelmintic resistance worldwide. However, there are no data available on using ivermectin for treating strongyle infections within domesticated horses in Thailand. Therefore, this study aimed to use the fecal egg count reduction (FECR) test to determine the strongylid egg reappearance period (ERP). Additionally, the nemabiome metabarcoding approach is incorporated to study patterns of strongyle species infection following ivermectin treatment. The study results indicate that, although ivermectin effectively eliminated adult strongyle parasites within two weeks post-treatment, the ERP was shortened to 6 weeks post-treatment with a mean FECR of 70.4% (95% CI 46.1-84.0). This potentially indicates a recent change in drug performance. In addition, nemabiome metabarcoding revealed that strongyle species have different levels of susceptibility in response to anthelmintic drugs. The reduction in ERP was associated with the early reappearance of specific species, dominated by Cylicostephanus longibursatus and Cylicocyclus nassatus, indicating the lower susceptibility of these species. In contrast, Poteriostomum imparidentatum, Triodontophorus nipponicus, and Triodontophorus serratus were not found post-treatment, indicating the high level of susceptibility of these species. This information is vital for comprehending the factors contributing to the emergence of resistance and for devising strategies to manage and control strongyle infections in horses.

Prevalence of gastrointestinal nematodes, parasite control practices and anthelmintic resistance patterns in a working horse population in Egypt.

BACKGROUND: Anthelmintic resistance is commonly reported in horse populations in developed countries, but evidence in some working horse populations is either lacking or inconclusive. OBJECTIVES: To estimate prevalence of GI nematode infections in working horses in Egypt and to evaluate strongyle resistance to ivermectin, doramectin and fenbendazole. STUDY DESIGN: Cross-sectional study. METHODS: Faecal egg count was performed on 644 working horses from 2 provinces in Egypt. A short questionnaire about horse signalment and worming history was completed for each horse. Horses identified with ≥50 strongyle type egg/g (n = 146) underwent faecal egg count reduction testing (FECRT) following treatment with ivermectin (n = 33), doramectin (n = 33) or fenbendazole (n = 30). Risk factors for strongyle (≥200 egg/g) and Parascaris equorum (>0 egg/g) infection were investigated using multivariable logistic regression analyses. RESULTS: The prevalence of low (0-199 epg), medium (200-500 epg) and high (>500 epg) strongyle infection was 88.4%, 5.9% and 5.8%, respectively. P. equorum eggs were detected in 5.1% (n = 33) of horses. Strongyle FECR was 100%, 99.97% and 100% following treatment with ivermectin, doramectin and fenbendazole respectively. Anthelmintic treatment in the 12 months preceding examination was associated with reduced likelihood of strongyle infection (odds ratio [OR] = 0.26, 95% confidence interval [CI] = 0.14, 0.47, P < .001). The likelihood of P. equorum infection was significantly associated with horses' age (OR = 0.78, 95% CI = 0.69, 0.90; P < .001). Male horses were more likely to have P. equorum infection (OR = 2.86, 95% CI = 1.37, 5.93, P = .005). MAIN LIMITATIONS: Nonrandomised selection of study areas and larval cultures was unsuccessful for some samples. CONCLUSIONS: There were low prevalence of strongyle and P. equorum infection and no evidence of macrocyclic lactones or benzimidazole resistance in strongyles in the studied working horse population.

Equine pythiosis in Egypt: clinicopathological findings, detection, identification and genotyping of Pythium insidiosum.

BACKGROUND: Equine pythiosis is an emerging, devastating disease that is hard to treat. The tumour-like nodular skin masses grow rapidly and the outcome is generally fatal, and thus early diagnosis and intervention are important. OBJECTIVES: (i) To highlight the clinical, histological and haematological findings in pythiosis, and (ii) to evaluate the efficacy of direct sample multiplex-PCR targeting the single nucleotide polymorphisms within the ribosomal DNA region for detection and genotyping of Pythium insidiosum. ANIMALS: Two hundred and twenty horses including 204 Arabian and 16 draft horses were surveyed. METHODS: Case series study diagnosis was based on clinical, pathological and haematological findings typical of P. insidiosum infection, culture identification, immunohistochemical investigation and direct sample PCR. RESULTS: The affected horses (24 of 220, 10.91%) presented with unifocal or multiple lesions on the abdomen, limbs, chest, face and mammary gland. Cases commonly had a history of access to stagnant water, ponds and intentionally flooded rice fields. Most were pregnant mares (58.33%). Histopathology revealed granulomatous reaction, blood vessel endotheliosis, heavy infiltration of eosinophils in the dermal layer, multifocal necrosis and Splendore-Hoeppli phenomenon. Unlike direct microscopy (50%) and culture (91.6%), multiplex-PCR assay identified P. insidiosum (Clade II) in all tested samples. To the best of the authors knowledge, this is the first study determining a clade of P. insidiosum causing equine pythiosis in Egypt. CONCLUSIONS AND CLINICAL IMPORTANCE: Direct sample multiplex-PCR assay is a potential tool for the early and rapid diagnosis of equine pythiosis. It overcomes limitations associated with morphological identification and provides a definitive diagnosis.