| the systematics of nematodes that cause ostertagiasis in domestic and wild ruminants in north america: an update and a key to species. | studies of medium stomach worms (subfamily ostertagiinae) of domestic and wild ruminants in north america have refined our understanding of the systematics, host distribution and biogeography of these nematodes. strong support for recognition of monophyly for the ostertagiinae has resulted from preliminary phylogenetic analyses of morphological characters among these and other trichostrongylids. evaluation of morphological and biochemical characters in our laboratory and elsewhere has not refute ... | 1993 | 8484224 |
| parasites, biodiversity, and population dynamics in an ecosystem in the high arctic. | the abomasa of 163 svalbard reindeers (rangifer tarandus platyrhynchus) from nordenskiöld land, spitsbergen (78 degrees n, 15 degrees e) were examined for adult and juvenile nematodes. spitsbergen has midnight sun from late april to late august, arctic night from late october to mid-february, permafrost, and snow cover from october to june. plant growth is restricted to 6-8 weeks, usually starting mid-june. in the reindeer calves, which are born in june prevalence and intensity of infection incr ... | 1999 | 10456416 |
| life-history strategies and population dynamics of abomasal nematodes in svalbard reindeer (rangifer tarandus platyrhynchus). | the observation that the total abundance of adult nematodes in the abomasum of svalbard reindeer increases between october and april suggests adaptation to cope with the arctic winter. here we investigate the extent to which selection has led to similar life-history strategies in the 3 most numerous trichostrongyle species. the life-histories are found to differ markedly. we use flexible statistical models for the abundance and dispersion of parasites in the host population. one of the taxa, mar ... | 2000 | 10759088 |
| dna evidence that ostertagia gruehneri and ostertagia arctica (nematoda: ostertagiinae) in reindeer from norway and svalbard are conspecific. | dna sequences of its-1 and its-2 of rdna were determined for 16 individual adult males each of ostertagia gruehneri and ostertagia arctica from svalbard reindeer (rangifer tarandus platyrhynchus) and eurasian tundra reindeer (r. t. tarandus). each its was virtually identical in o. gruehneri and o. arctica and the three mixed bases detected were shared by both species. our results strongly suggest that o. gruehneri and o. arctica are dimorphic males of the same species. | 2000 | 10779581 |
| identification by polymerase chain reaction (pcr) of marshallagia marshalli and ostertagia gruehneri from svalbard reindeer. | a polymerase chain reaction (pcr) assay to identify two common abomasal nematodes marshallagia marshalli and ostertagia gruehneri of svalbard reindeer was developed. species-specific pcr primers were designed from internal transcribed spacer (its)-2 sequences of rdna and validated using morphologically identified adult male and female nematodes. using the species-specific primers, a 110 bp fragment was amplified from m. marshalli and its minor morph marshallagia occidentalis and a 149 bp fragmen ... | 2000 | 10899533 |
| contrasting regulation of fecundity in two abomasal nematodes of svalbard reindeer (rangifer tarandus platyrhynchus). | stability of trichostrogylid populations indicates that some form of density-dependent regulation occurs which could act through fecundity. we present evidence for intraspecific density-dependent effects in 1 of 2, dominant, abomasal nematodes species (ostertagia gruehneri) of svalbard reindeer (rangifer tarandus platyrhynchus). we found evidence in o. gruehneri, for density-dependent regulation of female worm length in april, july and october 1999. however, it is only in july that female worm l ... | 2001 | 11444620 |
| dna evidence that marshallagia marshalli ransom, 1907 and m. occidentalis ransom, 1907 (nematoda: ostertagiinae) from svalbard reindeer are conspecific. | the gastro-intestinal parasitic nematodes of ruminants marshallagia marshalli and m. occidentalis are morphs of a single species according to indirect evidence. in this study, their taxonomic status and molecular identification were assessed more directly in isolates from the abomasal nematode community of svalbard reindeer using genetic data. dna sequences of the first and second internal transcribed spacers of nuclear ribosomal rna genes were obtained from individual nematodes by the polymeras ... | 2001 | 11586078 |
| the population dynamics of ostertagia gruehneri in reindeer: a model for the seasonal and intensity dependent variation in nematode fecundity. | the gastrointestinal nematode ostertagia gruehneri is a parasite of reindeer that can have a significant impact on host population dynamics. to gain a better understanding of the population dynamics of o. gruehneri, we parameterise a model for its fecundity that describes the observed seasonal and intensity dependent pattern of faecal egg counts well. the faecal egg count model is combined with a model for the seasonal faecal production rate of svalbard reindeer to obtain quantitative estimates ... | 2002 | 12076628 |
| the role of parasites in the dynamics of a reindeer population. | even though theoretical models show that parasites may regulate host population densities, few empirical studies have given support to this hypothesis. we present experimental and observational evidence for a host-parasite interaction where the parasite has sufficient impact on host population dynamics for regulation to occur. during a six year study of the svalbard reindeer and its parasitic gastrointestinal nematode ostertagia gruehneri we found that anthelminthic treatment in april-may increa ... | 2002 | 12184833 |
| sex ratio variation in gastrointestinal nematodes of svalbard reindeer; density dependence and implications for estimates of species composition. | estimates of the intensity and abundance of species provide essential data for ecological, evolutionary and epidemiological studies of gastrointestinal nematode communities. these estimates are typically derived from the species composition of adult males when only males have readily scorable species-specific morphological traits. such estimation assumes that all species in the community have the same adult sex ratio. we evaluated this assumption for the trichostrongyle nematodes ostertagia grue ... | 2005 | 15700761 |
| resistance to abomasal nematodes and individual genetic variability in reindeer. | resistance to parasites is believed to have a widespread influence on demographic and adaptive processes. in systems where parasites impose a fitness cost on their host, heterozygotes may be selected because they are more resistant to parasites than homozygotes. our objective was to assess the relationships between genomewide individual heterozygosity and abomasal nematode burdens in female svalbard reindeer (rangifer tarandus platyrhynchus) after the effects of host age, locality, season, and y ... | 2005 | 16262866 |
| population dynamics of nematode parasites of reindeer in the sub-arctic. | nematode parasite infections of semi-domestic reindeer grazing in their natural habitat in northern finland were monitored for approximately 2 years. this was achieved by monthly faecal egg counts of male and female calves and adult females from an experimental reindeer herd, in addition to estimating the acquisition of nematode infection from pasture using tracer reindeer calves. the most abundant parasite was ostertagia gruehneri in the worm counts of tracer animals and in faecal egg counts of ... | 2006 | 16934935 |
| amplification of the second internal transcribed spacer ribosomal dna of individual trichostrongylid nematode larvae by nested polymerase chain reaction. | the second internal transcribed spacer (its2) of ribosomal dna (rdna) is used as a genetic marker to identify trichostrongylid nematodes. however, it is often difficult to amplify by polymerase chain reaction (pcr) the its2 rdna of a single trichostrongylid nematode larva or egg. a nested pcr (npcr) assay was, therefore, developed to amplify the its2 from individual trichostrongylid nematode larvae. the results show that the its2 rdna of a significantly greater proportion of individual larvae wa ... | 2010 | 20453221 |
| the reindeer abomasal nematode (ostertagia gruehneri) is naturally transmitted to sheep when sharing pastures. | the increasing number of sheep (ovis aries) in northern finland, often alternately corralled with winter-fed reindeer (rangifer tarandus tarandus), creates potential for cross-infection of gastrointestinal nematodes. the aim of this study was to elucidate this possibility with 43 animals. eleven reindeer and 8 sheep had shared a corral by turns, reindeer during winters, and sheep in summers. another 12 reindeer had no known contact with sheep. twelve sheep had no close contact to other ruminants ... | 2014 | 25106839 |
| divergent parasite faunas in adjacent populations of west greenland caribou: natural and anthropogenic influences on diversity. | gastrointestinal parasite diversity was characterised for two adjacent populations of west greenland caribou (rangifer tarandus groenlandicus) through examinations of abomasa and small intestines collected from adult and subadult females during late winter. three trichostrongyline (trichostrongylina: nematoda) species were identified from the abomasa, although none were recovered from the small intestines, with faunal composition differing between the caribou populations. in caribou from kangerl ... | 2013 | 24533335 |
| parasites, stress and reindeer: infection with abomasal nematodes is not associated with elevated glucocorticoid levels in hair or faeces. | stress hormones (glucocorticoids), incorporated into hair/fur and faeces, have been proposed as biomarkers of overall health in wildlife. although such biomarkers may be helpful for wildlife conservation and management, their use has rarely been validated. there is a paucity of studies examining the variation of stress hormones in mammals and how they relate to other health measures, such as parasitism. parasites are ubiquitous in wildlife and can influence the fitness of individual animals and ... | 2016 | 27957334 |
| obligate larval inhibition of ostertagia gruehneri in rangifer tarandus? causes and consequences in an arctic system. | larval inhibition is a common strategy of trichostrongylidae nematodes that may increase survival of larvae during unfavourable periods and concentrate egg production when conditions are favourable for development and transmission. we investigated the propensity for larval inhibition in a population of ostertagia gruehneri, the most common gastrointestinal trichostrongylidae nematode of rangifer tarandus. initial experimental infections of 4 reindeer with o. gruehneri sourced from the bathurst c ... | 2012 | 22953998 |
| development and availability of the free-living stages of ostertagia gruehneri, an abomasal parasite of barrenground caribou (rangifer tarandus groenlandicus), on the canadian tundra. | climate change in the arctic is anticipated to alter the ecology of northern ecosystems, including the transmission dynamics of many parasite species. one parasite of concern is ostertagia gruehneri, an abomasal nematode of rangifer ssp. that causes reduced food intake, weight loss, and decreased pregnancy rates in reindeer. we investigated the development, availability, and overwinter survival of the free-living stages of o. gruehneri on the tundra. fecal plots containing o. gruehneri eggs were ... | 2012 | 22717158 |