Strongylids of Domestic Horses in Eastern Slovakia: Species Diversity and Evaluation of Particular Factors Affecting Strongylid Communities

Acta Parasitologica (2024) 69:1284–1294 https://doi.org/10.1007/s11686-024-00854-7 ORIGINAL PAPER Strongylids of Domestic Horses in Eastern Slovakia: Species Diversity and Evaluation of Particular Factors Affecting Strongylid Communities Tetiana A. Kuzmina1,2 · Alzbeta Königová1 · Ludmila Burcáková1,3 · Michal Babjak1 · Yaroslav Syrota1,2 Received: 17 March 2024 / Accepted: 25 April 2024 / Published online: 22 May 2024 © The Author(s) 2024 Abstract Purpose This study aimed to examine the species diversity and structure of the strongylid community in domestic horses in Eastern Slovakia. Also, an analysis of the impact of age, sex, and collection location factors on the strongyid communities was performed. Methods Twenty-seven horses 1.5–21 years old from two farms in eastern Slovakia with different horse-management conditions were studied. Strongylids were collected after horse treatments with Noromectin (0.2 mg ivermectin); 66,170 specimens were collected and identified. Faecal egg count reduction test (FECRT) was performed following fenbendazole (FBZ) and ivermectin (IVM) treatments. Results Twenty-four strongylid species were found; horses were infected with 6 to 16 (average = 11.7) species. Six cyathostomin species (Cylicocyclus nassatus, Cyathostomum catinatum, C. pateratum, Cylicostephanus longibursatus, C. goldi, C. calicatus) were the most prevalent; C. catinatum was the dominant species in both farms (Berger-Parker index 0.34 and 0.42). The structure of the strongylid community was multimodal with dominant, subdominant, background, and rare species. The Mantel test showed that horse age and sex did not significantly affect the nematode infracommunity composition (p > 0.05), while the impact of the collection location (farm) was significant (p = 0.03). Additionally, C. longibursatus was identified as the species contributing significantly to the observed farm differences. Strong resistance to FBZ was documented on both farms (FECRT was 36.4% and 22.7%); IVM resistance was not observed (FECRT = 100%). Conclusion This study presents the first report on the strongylids parasitizing domestic horses in Eastern Slovakia and gives basic information for further studies of horse parasites and their control in the region. Keywords Nematoda · Strongylidae · Parasite community · Horse-management conditions · FECRT · Slovakia Introduction Among more than 90 species that parasitize equids [1], strongylid nematodes are by far one of the most widespread and pathogenic group of parasites [2–6]. Strongylids parasitize all wild and domestic equids worldwide and can cause severe health problems, including loss of weight, Tetiana A. Kuzmina ; 1 Institute of Parasitology, Slovak Academy of Sciences, Hlinkova 3, 04001 Kosice, Slovakia 2 I. I. Schmalhausen Institute of Zoology NAS of Ukraine, Bogdan Khmelnytsky street, 15, Kyiv, Ukraine 3 University of Veterinary Medicine and Pharmacy in Kosice, Komenskeho 73, 04181 Kosice, Slovakia 13 colic, watery diarrhoea and ventral oedema, decreasing the productivity and breeding qualities of horses [7–10]. The pathogenic influence of different strongylids species in the horse is different; large strongylids (subfamily Strongylinae), especially representatives of the genus Strongylus, are the most pathogenic because they have complex tissue migrations through different abdominal organs over several months causing severe tissue damage and can lead to lifethreatening complications [11–14]. Pathogenicity of small strongylids (subfamily Cyathostominae) is not as severe; usually, cyathostomin infection in horses is asymptomatic. However, synchronous emerging of cyathostomin parasitic larvae from the intestinal wall can cause a life-threatening syndrome known as ‘‘larval cyathostominosis’’ with a casefatality rate reported up to 50% [10, 15, 16]. An individual horse may be co-infected with as many as 15–25 species of strongylids [5, 6, 17–19]. Accordingly, the Acta Parasitologica (2024) 69:1284–1294 horse strongylid community has a complex structure [5, 8; 20–25]. The prevalence and proportion of each species in the strongylid community may vary depending on the age, sex, and horse-management conditions, in particular, the frequency of anthelmintic treatments [5, 22]. The proportion of large strongylids in the communities of domestic horses is remarkably low– from less than 1–2% [5, 23]; small strongylids (Cyathostominae) comprise more than 95% of the overall strongylid communities. In recent decades, due to the frequent use of highly effective anthelmintics, the proportion of large strongylids in the communities has been decreasing, and cyathostomins have become the main group of horse parasites [2, 4, 6, 26–30]. Moreover, cyathostomins have developed resistance to various groups of anthelmintics worldwide [27; 31–33]. It has been shown that not all strongylid species were found to be resistant; so far, resistance to benzimidazole (BZ) drugs has been documented for 10–11 cyathostomin species [34–38], while seven cyathostomin species demonstrated ivermectin (IVM) resistance [35]. Therefore, for effective parasitological monitoring and the elaboration of efficient parasite control methods, it is imperative to know the species composition of the strongylid community on particular horse farms. Of 64 strongylid species described to date [3], domestic horses are parasitized by more than 40 species [3, 5, 8]. Meta-analysis of published data collected worldwide revealed that three cyathostomin species (Cylicocyclus nassatus, Cylicostephanus longibursatus, and Cyathostomum catinatum) were the most prevalent and relatively abundant species of equine strongylids [6]. Simultaneously, the species composition of strongylid communities varies in different countries [25]. In Europe, horse strongylid studies have been performed in different countries for more than 50 years [5, 8, 20, 22, 23, 28–30, 40–44]. Despite the horse industry being widely developed in the Slovak Republic, where more than 22,500 horses of 40 breeds are kept and bred [45], studies of the species diversity and structure of strongylid communities have not been carried out. In the late 1950s, a study of strongylids was performed in former Czechoslovakia [40]; as a result, 35 strongylid species were found in domestic horses. Later, a study of equine strongylids in Slovakia was conducted using the Reverse line blot hybridization assay for the species-specific identification of cyathostomins [46]. Through this method, 13 cyathostomin species were detected in faecal samples from domestic horses; information on the prevalence or proportion of these species in the strongylid community has not been documented. Several studies of strongylids in Slovak horse farms have been carried out using coprological methods, presumably to examine the distribution of anthelmintic resistance [47–51]. However, an analysis of all available literature sources revealed that data on the species compositio (...truncated)