Gastrointestinal parasite community structure in horses after the introduction of selective anthelmintic treatment strategies.
Abstract: 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.
Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.
Publication Date: 2023-12-25 PubMed ID: 38218052DOI: 10.1016/j.vetpar.2023.110111Google Scholar: Lookup
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Summary
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This research paper sets out to compare nematode parasite species in different groups of horses, by performing deep sequencing on parasite mixtures. The results showed that the introduction of a selective treatment strategy didn’t notably change the nematode community structure in Swedish horses. The method used also confirmed that this type of analysis is a valid approach to studying horse parasite communities.
Research Methodology
- The study involved the collection of horse faecal samples from almost 300 horses, both domestic and trotting breeds, from various locations around Sweden.
- The team then undertook a process referred to as ‘deep sequencing’ on these samples. This technique involves advanced DNA analysis to identify individual parasite species within the samples.
- For the DNA sequence analysis, researchers used a specific region of the genome known as the ITS2 sequence – a well-documented area for identifying nematode species.
- These sequences were then analysed using bioinformatics tools to assign each to an operational taxonomic unit (OTU) – essentially categorising each by their species.
Results and Findings
- The majority – 89% – of the larval samples contained the parasite ITS2 sequences.
- These sequences were assigned to 28 different species or taxa.
- The most common seven species found only represented 87% of the overall dataset, pointing to a high level of diversity among the colonising parasites.
- Multiple species were frequently present in the samples, although three – Cyathostomum catinatum, Cylicocyclus nassatus and Cylicostephanus calicatus – were the most present.
- The needles parasite types in the domestic horses and trotters were Strongylus vulgaris and S.edentatus.
- There were a variety of relationships with the host’s age, with some species decreasing in prevalence as the horses aged while others, namely C. catinatum and S. vulgaris, increased in prevalence.
Conclusions
- The study’s outcomes suggested that the parasite community structures have remained largely unchanged, despite the introduction of selective anthelmintic treatment strategies.
- The researchers also confirmed that the nemabiome analysis alongside diversity index analysis could provide an objective means of studying these parasite communities in horses.
Cite This Article
APA
Halvarsson P, Grandi G, Hägglund S, Höglund J.
(2023).
Gastrointestinal parasite community structure in horses after the introduction of selective anthelmintic treatment strategies.
Vet Parasitol, 326, 110111.
https://doi.org/10.1016/j.vetpar.2023.110111 Publication
Researcher Affiliations
- Swedish University of Agricultural Sciences, Department of Biomedical Sciences and Veterinary Public Health, Section for Parasitology, P.O. Box 7036, Uppsala, Sweden.
- Swedish University of Agricultural Sciences, Department of Biomedical Sciences and Veterinary Public Health, Section for Parasitology, P.O. Box 7036, Uppsala, Sweden.
- Vidilab AB, P.O. Box 33, SE-745 21 Enköping, Sweden.
- Swedish University of Agricultural Sciences, Department of Biomedical Sciences and Veterinary Public Health, Section for Parasitology, P.O. Box 7036, Uppsala, Sweden. Electronic address: johan.hoglund@slu.se.
Conflict of Interest Statement
Declaration of Competing Interest We hereby declare that the information disclosed is accurate and that I am not aware of any other situation of actual, potential or apparent conflict of interest. I undertake to inform you of any change in these circumstances, including if a problem arises in the course of the meeting or the work itself.
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