A Survey of the Helminths of Scottish Hill Sheep

Parnell, I. W.; Rayski, C.; Dunn, A. M.; Mackintosh, G. M.

doi:10.1017/s0022149x00032715

Cited by 42 publications

(16 citation statements)

References 11 publications

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“…The large number of nematode parasite species that was identified in the unimproved Soay sheep grazed on natural pastures, without active management intervention, differed from the situation that usually pertains in improved sheep flocks kept on intensively managed grass and clover pastures and subject to active helminth parasite control. In managed flocks, it is commonplace to identify as few as four parasitic nematode species, with seasonal predominance of just one or two (Parnell et al, 1954;Barger, 1985;Boag and Thomas, 1971;Boag and Thomas, 1977) giving rise to diseases referred to as teladorsagiosis, nematodirosis, haemonchosis, or trichostongylosis (Sargison et al, 2007a). By contrast, co-infection with a larger and more diverse range of nematode parasites is pervasive in wildlife (Petney and Andrews, 1998;Lello et al, 2004) and has been shown in feral Soay sheep (Wimmer et al, 2004;Craig et al, 2006), which have not been subject to intensification and management.…”

Section: Discussionmentioning

confidence: 99%

Gastrointestinal nematode species diversity in Soay sheep kept in a natural environment without active parasite control

Sinclair

Melville

Sargison

et al. 2016

Veterinary Parasitology

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Molecular methods based on ITS2 sequence analysis were used to identify strongylid parasites and describe their diversity in a management intervention and anthelmintic drug treatment-free sheep flock. Fourteen different nematode parasite species were identified in the flock and the results showed a greater level of nematode species diversity than is normally reported in managed farmed flocks, with the presence of parasites such as Bunostomum trigonocephalum, Ostertagia leptospicularis, Spiculopteragia houdemeri and Trichostrongylus retortaeformis that are considered to be absent or rare in sheep kept in comparable localities. The implied prevalences of Haemonchus contortus in lambs, and of Trichostrongylus axei in lambs, ewes and rams, were higher than those in farmed sheep kept in similar regions, while those of Teladorsagia circumcincta and Trichostrongylus vitrinus were lower. Comparison of the patterns of nematode parasite infection between the summer and autumn sampling periods showed differences from the scenarios that are commonplace in comparable managed flocks; with T. vitrinus burdens of the lambs being higher in the summer than in the winter, and Oesophagostomum venulosum being the predominant nematode species in the adult sheep during the summer, while more-or-less absent from these groups during the winter. Rams played an important role in the epidemiology of certain parasitic nematode species. The relatively non-pathogenic O. venulosum was the only parasitic nematode species to predominate in any group during the study. This preliminary characterisation of the nematode parasite burdens of sheep extensively grazed on diverse unimproved pastures will aid in the understanding of the parasitological consequences of intensive grazing management and of the manner in which modern agriculture upsets the equilibrium between parasites and their hosts. These factors must be accounted for when defining the concept of sustainable parasite control and informing sustainability with reference to commercially efficient sheep farming.

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Section: Discussionmentioning

confidence: 99%

Gastrointestinal nematode species diversity in Soay sheep kept in a natural environment without active parasite control

Sinclair

Melville

Sargison

et al. 2016

Veterinary Parasitology

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“…Epidemiological surveys of helminth species infection in hill and lowland sheep flocks in northern Britain consistently identify Teladorsagia circumcincta as the most abundant species (Parnell et al 1954 ;Thomas, 1971, 1977 ;Reid and Armour, 1975 a, b;Stear et al 1997 ;Bartley et al 2003). Similarly, T. circumcincta has long been considered the most significant species infecting the feral population of Soay sheep on St Kilda.…”

Section: Introductionmentioning

confidence: 99%

Gastrointestinal nematode species burdens and host mortality in a feral sheep population

2006

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Every few years a large proportion of the feral sheep on Hirta, St Kilda die due to food shortage. The effects of malnutrition are exacerbated by gastrointestinal nematodes. As found in sheep flocks in mainland Britain, Teladorsagia circumcincta has long been considered the predominant and most pathogenic nematode species in all age classes of Soay sheep. Previous research indicated that intensity of this species showed a negative association with host age and comprised 75% of the entire gastrointestinal burden. Here we present new data that show Trichostrongylus axei and Trichostrongylus vitrinus to be the predominant worm pathogens in young Soay sheep. In the present study, Trichostrongylus spp. burdens declined with host age whereas T. circumcincta actually increased in burden over the first few age classes. Also, male hosts had significantly higher burdens of Trichostrongylus spp. than females, with this genus making up a higher proportion of the strongyle egg producing community in male hosts than female hosts. These new findings raise questions concerning our previous interpretation of the main nematode species contributing to strongyle egg count in the population, and the contrasting infection patterns of these nematode species in unmanaged St Kilda Soay sheep compared with domestic sheep in mainland Britain.

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“…Surveys carried out in Great Britain have shown that Trichostrongylus vitrinus is the species of Trichostrongylus most frequently found m the small intestine (PARNELL et al, 1954;CROFTON, 1955CROFTON, , 1957TAYLOR & CAWTHORNE, 1972;REID & ARMOUR, 1975;CORNWELL, 1975). T. vitrinus was considered to be the main cause of helminthiasis in hoggs in Scotland during the winter and spring (PARNELL et al, 1954) and, in association with Cooperia spp., to be the cause°f winter helminthiasis in Iambs in south-west England (CROFTON, 1957). The pathogenicity of this nematode has been investigated experimentally by TAYLOR & PEARSON (1979), SYKES et al, (1979) and COOP et al, (1979).…”

Section: Introductionmentioning

confidence: 99%

Observations on the bionomics of the free-living stages of Trichostrongylus vitrinus

Rose¹,

Small²

1984

J. Helminthol.

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Eggs of Trichostrongylus vitrinus in faecal pellets deposited on grass plots each month from April 1981 to March 1982 developed into infective larvae. From October to March development was slow and mortality of the pre-infective stages was very high. From April to September development was more rapid. The weather was generally dry and mortality of the pre-infective stages was high on plots with short herbage but was lower on most of the plots with long herbage, especially in July and August. In the laboratory, development of eggs into infective larvae was completed at temperatures ranging from 4°C to 27°C in faecal pellets which were either kept moist or dried out slowly, but not in faecal pellets which dried out rapidly. The rate of development increased as the temperature rose. Infective larvae survived for up to 16 months on the herbage of grass plots; some survived during very cold weather in the winter of 1981/82. In the laboratory, infective larvae suspended in tap water survived even longer at 4°C and 10°C but not at higher temperatures. They were rapidly killed by continuous freezing. They Survived for up to 8 weeks when subjected to desiccation, The relationship between climatic conditions and the development and survival of the free-living stages is discussed

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A Survey of the Helminths of Scottish Hill Sheep

Cited by 42 publications

References 11 publications

Gastrointestinal nematode species diversity in Soay sheep kept in a natural environment without active parasite control

Gastrointestinal nematode species diversity in Soay sheep kept in a natural environment without active parasite control

Gastrointestinal nematode species burdens and host mortality in a feral sheep population

Observations on the bionomics of the free-living stages of Trichostrongylus vitrinus

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