The occurrence and genetic characterization of Cryptosporidium and Giardia species in foals in Belgium, The Netherlands, Germany and Greece

Highlights

• A study was performed in Belgium, The Netherlands, Germany and Greece to determine the occurrence and the zoonotic potential of Giardia spp. and Cryptosporidium spp. in foals.

• Only 2% of the examined foals were positive for Cryptosporidium, while 12.3% of the horses excreted Giardia cysts.

• No significant correlation between Giardia infection and diarrhoea was observed.

• Most of the identified Cryptosporidium and Giardia isolates belonged to animal-specific species/genotypes or genotypes that are predominantly found in animals, suggesting a low risk for zoonotic transmission.

Abstract

Faecal samples were collected from foals between the age of 1 week and 6 months in Belgium, The Netherlands, Germany and Greece. A quantitative direct immunofluorescence assay based on the commercial MERIFLUOR Cryptosporidium/Giardia kit was performed to evaluate the presence of (oo) cysts. Parasite positive samples were genotyped, based on the 18S ribosomal DNA gene and the heat shock protein (HSP70) gene for Cryptosporidium and on the β-giardin gene and the triose phosphate isomerase (TPI) gene for Giardia. In total, 134 foals from Belgium, 44 foals from The Netherlands, 30 foals from Germany and 190 foals from Greece were examined. No Cryptosporidium oocysts were identified in faecal samples from foals in Germany and The Netherlands. In Belgium and Greece, 4.5% and 1.1% of the foals examined were Cryptosporidium positive, respectively, all with a low oocyst excretion ranging from 100 to 2450 oocysts per gram of faeces. For Giardia, 14.2%, 11.4%, 10.0% and 11.6% of the foals in Belgium, The Netherlands, Germany and Greece, respectively, were found to excrete cysts, with a range of 50 up to 4,000,000 cysts per gram of faeces. Younger animals secreted significantly more Giardia cysts than older horses (p < 0.05), but no significant correlation between Giardia infection and diarrhoea was observed. Most Giardia positive samples belonged to assemblage AI and/or BIV, but also assemblage E was detected in two samples. Together with the identification of Cryptosporidium horse genotype, this suggests only a low risk for zoonotic transmission.

Introduction

Cryptosporidium spp. and Giardia spp. are protozoan parasites that have been reported worldwide in a wide range of hosts, including horses.

In horses, excretion of Cryptosporidium oocysts has been reported in different geographical areas, with infection rates ranging between 0.75% (De Souza et al., 2009) and 25% (Smith et al., 2010). In some studies, the prevalence was higher in foals (Veronesi et al., 2010), while in other studies, the peak prevalence was observed in adult animals (Majewska et al., 1999, Majewska et al., 2004. Part of this variation may be due to differences in study design, the limited number of animals and/or farms in the study, and the diagnostic technique that was used. Although an impact of Cryptosporidium infection on horse health has been reported (Netherwood et al., 1996, Majewska et al., 2004, Grinberg et al., 2008, Frederick et al., 2009), it seems to be less important compared to ruminants and especially intensively reared calves, in which infection with Cryptosporidium parvum is an important cause of neonatal diarrhoea (de Graaf et al., 1999).

Similarly, the prevalence of Giardia duodenalis has been reported in horses from various locations with considerable variation (0.5–35%) (Pavlásek et al., 1995, Olson et al., 1997, Atwill et al., 2000, De Souza et al., 2009, Veronesi et al., 2010, Traversa et al., 2012, Santin et al., 2013), but the number of studies on the prevalence of G. duodenalis in foals is more limited compared to studies on Cryptosporidium. Moreover, the impact of Giardia infection on equine health remains undefined, in contrast to calves and lambs, where Giardia infections have been associated with a decreased growth and diarrhoea (Olson et al., 1995, Geurden et al., 2010).

The relevance of animal infections is not only limited to the impact on animal health or production, but should also be considered from a public health point of view as they may also be a source of infection, either by infecting people by direct contact or by contaminating water supplies, since many outbreaks of infections by both parasites are waterborne (Baldursson and Karanis, 2011). An increasing number of studies seems to indicate a public health relevance of equine Cryptosporidium infections. Horses were frequently infected with the zoonotic C. parvum (Ryan et al., 2003, Grinberg et al., 2008, Imhasly et al., 2009, Smith et al., 2010, Laatamna et al., 2015) and occasionally the human species Cryptosporidium hominis was detected in horses (Laatamna et al., 2015). Similarly for G. duodenalis, the assemblages A and B have been identified, although the zoonotic potential of G. duodenalis in horses remains largely unexplored (Traub et al., 2005, Traversa et al., 2012, Santin et al., 2013).

In Europe, with the exception of Italy – where extensive studies have been performed (Veronesi et al., 2010, Traversa et al., 2012, Caffara et al., 2013) – there are only limited data on the prevalence of both protozoal infections in horses as well as their zoonotic importance. The objective of the present study was to acquire additional data on the occurrence and genotypes of Cryptosporidium and Giardia in foals in regions of Europe where no records were available.