Rumen fluke in Irish sheep: prevalence, risk factors and molecular identification of two paramphistome species

Abstract

BackgroundRumen flukes are trematode parasites found globally; in tropical and sub-tropical climates, infection can result in paramphistomosis, which can have a deleterious impact on livestock. In Europe, rumen fluke is not regarded as a clinically significant parasite, recently however, the prevalence of rumen fluke has sharply increased and several outbreaks of clinical paramphistomosis have been reported. Gaining a better understanding of rumen fluke transmission and identification of risk factors is crucial to improve the control of this parasitic disease. In this regard, a national prevalence study of rumen fluke infection and an investigation of associated risk factors were conducted in Irish sheep flocks between November 2014 and January 2015. In addition, a molecular identification of the rumen fluke species present in Ireland was carried out using an isolation method of individual eggs from faecal material coupled with a PCR. After the DNA extraction of 54 individual eggs, the nuclear fragment ITS-2 was amplified and sequenced using the same primers.ResultsAn apparent herd prevalence of 77.3 % was determined. Several risk factors were identified including type of pasture grazed, regional variation, and sharing of the paddocks with other livestock species. A novel relationship between the Suffolk breed and higher FEC was reported for the first time. The predominant rumen fluke species found was C. daubneyi. Nevertheless, P. leydeni was unexpectedly identified infecting sheep in Ireland for the first time.ConclusionsAn exceptionally high prevalence of rumen fluke among Irish sheep flocks has been highlighted in this study and a more thorough investigation is necessary to analyse its economic impact. The isolation of individual eggs coupled with the PCR technique used here has proven a reliable tool for discrimination of Paramphistomum spp. This technique may facilitate forthcoming studies of the effects of paramphistomosis on livestock production. The most noteworthy finding was the identification of P. leydeni affecting sheep in Ireland, however further studies are required to clarify its implications. Also, a significant relationship between Suffolk breed and a heavier infection was found, which can be used as a starting point for future research on control strategies of rumen fluke infection.

Paramphistomosis of Ruminants: An Emerging Parasitic Disease in Europe

“…Studies across Western Europe, in the Netherlands [49], Belgium [50], Italy [51] and Spain [17] have also confirmed, using molecular tools, the predominant rumen fluke species identified in livestock to be C. daubneyi. A study in Ireland [18] confirmed a high prevalence of C. daubneyi in Irish sheep flocks, but also identified infection with another rumen fluke species, Paramphistomum leydeni, in a single animal. One case of P. leydeni infection in cattle has also been reported in the Netherlands [49].…”

“…However, in recent years, significant increases in the prevalence of rumen fluke infections have been noted in ruminant livestock populations across western European countries. Using molecular sequence data, the species Calicophoron daubneyi has been clearly identified as the primary rumen fluke parasite infecting cattle, sheep and goats in Europe [17][18][19][20]. Prevalence levelsas high as 29-36% in Spain [21,22], 20% in France [23], and 59% in Wales [24] in cattle, and up to 77% in Ireland [18] and 42% in Wales [24] in sheep have now been reported ( Table 1).…”

Paramphistomidose – eine Übersicht zu Epidemiologie und klinischer Symptomatik

“…Küstennahe walisische Rinder-und Schafbetriebe waren stärker betroffen als Betriebe in Gebieten im Landesinneren [26]. Ein vergleichbares geographisches Bild zeigte sich bei Schafen in Irland [40]. In einer neueren Studie aus Irland werden Bodenbedeckung, Vegetation, Niederschlag, Wassergehalt des Bodens und Vorkommen von Zwischenwirthabitaten als wesentliche Risikofaktoren für Paramphistomidose angesehen [45].…”

“…In allen Fällen wurden dafür starke Niederschläge und massive Vernässung des Bodens als Hauptursache ausgemacht, sodass es zu einer starken Ausbreitung des Zwischenwirts und Vermehrung der infektiösen Stadien des Egels kommen konnte. Grundsätzlich sind die hohen Prävalenzen nicht infrage zu stellen, auch wenn die Werte mit wenigen Ausnahmen [7][26] [40]nicht wahre Prävalenzen widerspiegeln. Schlachthofuntersuchungen und retrospektive Betrachtungen von Sektionen und Kotuntersuchungen bergen die Gefahr einer Fehleinschätzung der Prävalenz, da es sich um selektive Untersuchungen handelt.…”

“…Die Prävalenzen in Küstenregionen mit feuchten Böden scheinen höher zu sein als im Landesinneren, wie in Wales [26], Irland [40] [45] und Spanien [17] beobachtet. Die Ausbreitung in trockenere Gebiete wird begünstigt durch Vernässung des Bodens infolge starker Regenfälle oder aus ökologischen Gründen bei Anhebung des Grundwasserspiegels [51], wodurch geeignete Lebensbedingungen für den Zwischenwirt geschaffen werden [45].…”