Scala et al. Parasites Vectors (2021) 14:246 https://doi.org/10.1186/s13071-021-04747-w Parasites & Vectors RESEARCH Open Access Parascaris spp. eggs in horses of Italy: a large-scale epidemiological analysis of the egg excretion and conditioning factors Antonio Scala1†, Claudia Tamponi1†, Giuliana Sanna1, Giulio Predieri2, Luisa Meloni1, Stephane Knoll1, Giampietro Sedda1, Giorgia Dessì1, Maria Grazia Cappai1 and Antonio Varcasia1* Abstract Background: Equine ascariosis, caused by Parascaris spp., is a worldwide endoparasitic disease afecting young horses in particular. Despite the great number of horses reared in Italy, large-scale epidemiological surveys dealing with ascariosis prevalence in the country are not reported in the current literature. For this reason, the present survey aims to describe, for the frst time, the spread and infestation of Parascaris spp. in a large population of Italian horses (6896 animals) using faecal egg counts, and further to identify risk factors associated with ascarid egg shedding. Methods: Individual rectal faecal samples collected during routine veterinary examinations were used and Parascaris spp. prevalence was tested against the animal’s age, sex, housing conditions, geographic provenance as well as the respective sampling season. Results: Among the examined stables, 35.8% showed at least one horse to be positive for Parascaris spp. eggs and an overall prevalence of 6.3% was found. Ascariosis rates tended to decrease signifcantly with age and, proportionally, 80.0% of the recorded Parascaris spp. eggs were found in 0.7% of the examined animals. Statistically signifcant difer- ences among prevalence rates were found between the diferent geographic areas of provenance and prevalence was found to be higher in horses reared outdoors compared to those raised indoors. Analysis of data based on sex and season did not show any signifcant diferences. Despite the lower prevalence found compared to other Euro- pean countries, ascariosis was concluded to represent a signifcant health challenge for horses reared in Italy, espe- cially foals. Age (foals and yearlings) and outdoor rearing were identifed to be signifcant risk factors for Parascaris spp. egg shedding. Furthermore, the relevance of the infected horses over 6 years of age should not be underestimated as these represent a signifcant source of contamination for younger animals. Conclusions: The development of improved treatment protocols based on regular faecal examination combined with follow-up assessment of the efcacy of integrated action plans would prove benefcial in regard to animal health and anthelmintic resistance reduction in the feld. Keywords: Parascaris, Horses, Italy, Epidemiological survey, Treatments, Ascariosis Background Equine ascariosis is a worldwide endoparasitic disease caused by Parascaris spp. that predominantly afects *Correspondence: [email protected] the health status of young horses [1, 2]. In foals, these †Antonio Scala and Claudia Tamponi contributed equally to this work parasites can be found in up to 100% of cases [3, 4] and, 1 Dipartimento di Medicina Veterinaria, Università di Sassari, Sassari, Italy Full list of author information is available at the end of the article according to its severity and stage, is characterised by © The Author(s) 2021. 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The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdo- main/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Scala et al. Parasites Vectors (2021) 14:246 Page 2 of 8 nasal discharge, coughing, a rough or bristly hair coat, without prior faecal examination in 85.3% of cases, and slow growth and occasional small intestine rupture fol- in 57.8% with a dosage based solely on a visual weight lowing the heavy accumulation of worms [5–7]. Never- estimation of the animal. Furthermore, only 21.3% of the theless, the main clinical fnding related to Parascaris farmers generally removed horse faeces from pastures as spp. infection is small intestinal impaction [6, 7]. part of ascariosis prophylaxis [28]. Typically, ascariosis is defned as an infection caused by Despite the large number of horses (154,505 indi- Parascaris equorum; however, in the USA, Switzerland viduals) reared in Italy, to the best of our knowledge, no and Sweden, Parascaris univalens has recently been rec- large-scale epidemiological surveys dealing with ascari- ognized as the dominant species afecting horses [8–10]. osis prevalence in horses are reported in the present lit- In any case, the two species are considered morphologi- erature. Moreover, studies which do graze this subject are cally identical and can only be distinguished through mostly related to anthelmintic efcacy trials [22, 29]. karyotyping; P. univalens possesses one pair of germ line Against this background, the present survey aims to chromosomes with respect to the two of P. equorum [9, describe, for the frst time, the spread and infestation of 11]. Additionally, recent mitochondrial genome analysis Parascaris spp. in a large population of horses through- revealed these two to be very closely related and may rep- out Italy using faecal egg counts (FEC), and further to resent the same species after all [12]. identify risk factors associated with ascarid egg shedding. Te life cycle of Parascaris spp. initiates with the inges- tion of parasite eggs containing infective L2 larvae (lar- Methods vae develop within 9–14 days after egg excretion within Sampling and coprological examination the faeces of infected horses) by a suitable host [7]. Te study population for this research had been defned After hatching in the host’s intestine, larvae embark on a in a parallel study evaluating the excretion of gastrointes- migration following the hepato-tracheal migratory route tinal strongyle eggs [30]. before fnally returning to the small intestine [13, 14]. A total of 6896 randomly selected horses, ranging from Adult development occurs in the jejunum where females 6 months to 36 years old, were examined through copro- will start laying eggs within about 10–15 weeks of infec- scopic analysis for the presence of ascarid eggs between tion [5, 15, 16]. 2015 (n. 4164) and 2016 (n. 2732). Animals from 548 dif- Mature Parascaris spp. females are particularly fertile, ferent stables located throughout all regions and islands which can lead to high faecal egg counts (FEC) and sig- of Italy were included. nifcant soil and pasture contamination (requiring ade- Individual rectal faecal samples collected during rou- quate management), even in the case of limited parasite tine veterinary examinations were sent, vacuum-packed, burden [17, 18]. Overall, a single infected horse has been in refrigerated containers, to the parasitology laboratory reported to be able to output upwards of 50 million eggs of the Department of Veterinary Medicine of the Univer- per day [19]. Furthermore, eggs of Parascaris spp. can sity of Sassari through an express courier within 3 days survive in the external environment (pastures, paddocks, after collection. boxes, etc.) in excess of 1 year [13, 18, 20]. Each faecal sample was accompanied by a form flled Foal ascariosis control programs are based on year- in by the sampling veterinarian with the horse’s data round monthly rotational anthelmintic treatment with including age, sex, housing conditions and stable. Copro- benzimidazole (e.g. fenbendazole—FBZ), tetrahydropy- logical examination was carried out through the modifed rimidine (e.g. pyrantel—PYR) and macrocyclic lactones McMaster method as described by Raynaud [31], using a (e.g. ivermectin—IVM and moxidectin—MOX) [21]. In sodium chloride (NaCl) supersaturated solution (specifc Italy, the treatment of foals is predominantly carried out gravity = 1.2) for fotation and an egg detection limit of using IVM and PYR starting from 2 months of age and is 15 eggs per gram (EPG) of faeces. Parascaris spp. eggs repeated every 2 months up to 1 year of age [22]. were identifed by morphology [7]. In Parascaris spp., anthelmintic resistance (AR) to macrocyclic lactones, probably due to intensive use of Statistical analysis these drugs, has been widely reported since 2002 [23– Data were collected on a spreadsheet (Microsoft Excel ®) 25]. Additionally, recent reports have suggested AR to and subsequently processed using Minitab ® (Minitab, pyrantel salts and benzimidazole drugs to be present as Inc., State College, Pennsylvania, USA) and Epi Info ® well [1, 26, 27]. In Italy, AR to PYR and IVM in ascarids 6.0 (Centers for Disease Control and Prevention [CDC]/ in horses has been reported since 2009 [22]. World Health Organization [WHO], Atlanta, GA, USA) Recently,