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haematology, weight and condition of captive red grouse (lagopus lagopus scoticus) infected with caecal threadworm (trichostrongylus tenuis).red grouse infected with the caecal threadworm trichostrongylus tenuis developed a mild anaemia. haemoglobin and albumin levels in the blood fell but there were no significant changes in the number of red blood cells or their size. in infected birds the numbers of circulating eosinophils and heterophils increase, as did the concentration of alpha, beta and gamma globulin. body weights did not change but muscle masses shrank. birds that subsequently died had the lowest concentration of haemoglobi ...1978749086
factors affecting the establishment of the caecal threadworm trichostrongylus tenuis in red grouse (lagopus lagopus scoticus).the resistance of captive reared red grouse to trichostrongylus tenuis was measured as the proportion of ingested infective 3rd-stage larvae which failed to develop to adult worms. individual grouse showed wide, repeatable variations in resistance. seasonal variations may also have occurred. red grouse acquired little or no effective immunity to reinfection after challenge with a single dose of infective larvae. in trickle-dosed grouse, however, adult worms weakly inhibited the establishment of ...19892594417
development and survival of the free-living stages of trichostrongylus tenuis, a caecal parasite of red grouse lagopus lagopus scoticus.in the laboratory, yields of infective 3rd-stage larvae of trichostrongylus tenuis were determined by temperature when moisture was adequate. on the moor, eggs in caecal faeces did not develop to infective larvae during the winter. in summer, development did occur and yields of infective larvae were related to temperature: greatest yields were obtained when mean monthly soil surface temperatures ranged between 7.6 and 10.3 degrees c. rainfall was unimportant, as was desiccation. during summer th ...19892797866
arrested development of trichostrongylus tenuis as third stage larvae in red grouse.worms were counted in red grouse (lagopus lagopus scoticus) in north east scotland in march, april, august, september, november and december 1986. immature worms occurred as third (l3) and fourth (l4) stage larvae throughout. two kinds of evidence suggest that l3 larvae spent much of the winter in a state of arrested development. first, recently acquired l3 larvae could be distinguished by the fact that they retained outer l2 cuticles for a few days; these were present only in the august and sep ...19883194598
the effect of trichostrongylus tenuis on the caecal mucosa of young, old and anthelmintic-treated wild red grouse, lagopus lagopus scoticus.the caecal mucosa of wild young and adult grouse infected naturally with trichostrongylus tenuis was examined by means of scanning electron microscopy and compared with adult grouse which had been treated with an anthelmintic. the caecal mucosa of young red grouse with low worm burdens possessed longitudinal plicae and exhibited little damage. the caeca from adult grouse, most of which carried high worm burdens, showed a localized depression of plicae and atrophy and cell disruption in areas of ...19873588017
host specificity of trichostrongylus tenuis from red grouse and northern bobwhites in experimental infections of northern bobwhites.the red grouse (lagopus lagopus scoticus) and northern bobwhite (colinus virginianus) are parasitized by the cecal nematode, trichostrongylus tenuis. our objective was to determine if t. tenuis from red grouse is infective in bobwhites. we inoculated bobwhites with infective-stage t. tenuis larvae that originated from red grouse in northern england and bobwhites in florida. we also inoculated domestic chickens with larvae from the same sources. none of the 6 bobwhites inoculated with larvae from ...19938331474
caecal threadworms trichostrongylus tenuis in red grouse lagopus lagopus scoticus: effects of weather and host density upon estimated worm burdens.trichostrongylus tenuis eggs were counted in faeces from individually marked wild red grouse for 8 years. egg counts varied seasonally and annually. in some years, a sudden increase in mid-april was consistent with delayed maturation of larvae which had overwintered in the birds in a hypobiotic state. a more gradual increase in summer was probably due to uninterrupted maturation of larvae ingested then. despite 30-fold year-to-year variation in mean egg counts, relative differences in egg counts ...19938414674
hypobiosis of trichostrongylus tenuis in experimentally infected grey partridges.storage of infective larvae (l3) of trichostrongylus tenuis at +4 degrees c for six weeks before being given as single infections to grey partridges (perdix perdix) did not increase the proportion of worms subsequently found to be hypobiotic. however, after repeated infections, hypobiotic larvae were numerous. three infections given over three weeks resulted not only in the presence of many hypobiotic larvae, but also in the coincident loss of most adult worms. this indication of the role of imm ...19938460270
the effect of parasites on wildlife.populations of animals which live in the wild are regulated by many biotic and abiotic factors. parasites are one of the biotic factors. parasites may influence their hosts in different ways. they may cause the death of the host due to a direct lethal effect or an indirect effect. direct lethal effects may occur if killing is a part of the life cycle of the parasite or if hosts and parasites have not developed an equilibrium. the introduction of hosts or parasites into a new environment with sui ...19968933697
transmission dynamics and host-parasite interactions of trichostrongylus tenuis in red grouse (lagopus lagopus scoticus).two components of the transmission dynamics of trichostrongylus tenuis in red grouse are examined and quantified, namely parasite transmission rate and density-dependent reductions in egg production. age-intensity data for birds of known age suggest that the rate of parasite uptake increases during the first 6 mo of a bird's life and this increase reflects an increase in feeding rate with age and exhibits no signs of self-cure. analysis of these age-intensity curves permits us to estimate the tr ...19979105295
cestodiasis in the red grouse in scotland.little is known about the cestode parasites of red grouse lagopus lagopus scoticus. the carcasses of 71 free-living and grouse collected from northeastern scotland (uk) between june 1991 and september 1992 were examined for the cestode paroniella urogalli. over 70% of young and old birds were infected in summer and winter. cestode abundance ranged from 0 to 29 (mean +/- se = 5.54 +/- 0.81) worms per host and did not differ significantly between young and old grouse, or between seasons. cestode i ...199910231751
faecal egg counts provide a reliable measure of trichostrongylus tenuis intensities in free-living red grouse lagopus lagopus scoticus.the reliability of different egg counting methods for estimating the intensity of trichostrongylus tenuis infections in red grouse, lagopus lagopus scoticus, was investigated in the autumn, when grouse may harbour high parasite intensities. possible limitations to the use of these methods were also examined. faecal egg counts were found to accurately estimate t. tenuis worm intensities, at least up to an observed maximum of c. 8000 worms. two egg counting methods (smear and mcmaster) gave consis ...200414972040
population biology of trichostrongylus tenuis, a parasite of economic importance for red grouse management.the caecal nematode, trichostrongylus tenuis, is associated with dramatic decreases in the density of red grouse (lagopus lagopus scoticus) resulting in a significant loss of sporting income to many upland estates in the uk. in this article peter hudson and andrew dobson describe the dynamics of the grouse-t. tenuis system, show that the parasites can cause population crashes and present preliminary findings from the development of new control methods.198915463233
interactions between population processes in a cyclic species: parasites reduce autumn territorial behaviour of male red grouse.the causes of population cycles fascinate and perplex ecologist. most work have focused on single processes, whether extrinsic or intrinsic, more rarely on how different processes might interact to cause or mould the unstable population dynamics. in red grouse (lagopus lagopus scoticus), two causal mechanisms have been supported: territorial behaviour (changes in autumn aggressiveness) and parasites (parasite induced reduction in fecundity). here, we report on how these two regulatory processes ...200515891828
interactions between intrinsic and extrinsic mechanisms in a cyclic species: testosterone increases parasite infection in red grouse.field studies of mechanisms involved in population regulation have tended to focus on the roles of either intrinsic or extrinsic factors, but these are rarely mutually exclusive and their interactions can be crucial in determining dynamics. experiments on red grouse lagopus lagopus scoticus have shown that population instability can be caused both by the effects of a parasitic nematode, trichostrongylus tenuis, on host production or by changes in testosterone influencing aggressive behaviour and ...200516191643
nematode parasites reduce carotenoid-based signalling in male red grouse.carotenoids determine the yellow-red colours of many ornaments, which often function as signals of quality. carotenoid-based signalling may reliably advertise health and should be particularly sensitive to parasite infections. nematodes are among the commonest parasites of vertebrates, with well-documented negative effects on their hosts. however, to date, little is known about the effects that these parasites may have on carotenoid-based signalling. tetraonid birds (grouse) exhibit supra-orbita ...200717264052
absence of three known benzimidazole resistance mutations in trichostrongylus tenuis, a nematode parasite of avian hosts.benzimidazole (bz) resistance is widespread in nematode parasites of livestock, but very little is known about the levels of bz resistance in parasites with avian hosts. we investigated bz resistance in trichostrongylus tenuis, a nematode parasite of red grouse, lagopus lagopus scotica. bz anthelmintics had been in use in this system for up to 15 years, yet existing phenotypic evidence for resistance was inconclusive. we screened 1530 individuals from 14 populations at the principal beta-tubulin ...200819027239
fitting models of multiple hypotheses to partial population data: investigating the causes of cycles in red grouse.there are two postulated causes for the observed periodic fluctuations (cycles) in red grouse (lagopus lagopus scoticus). the first involves interaction with the parasitic nematode trichostrongylus tenuis. the second invokes delayed regulation through the effect of male aggressiveness on territoriality. empirical evidence exists to support both hypotheses, and each hypothesis has been modeled deterministically. however, little effort has gone into looking at the combined effects of the two mecha ...200919627232
quantifying fenbendazole and its metabolites in self-medicating wild red grouse lagopus lagopus scoticus using an hplc-ms-ms approach.on red grouse estates in the uk the nematode parasite trichostrongylus tenuis is often controlled by application of grit medicated with the anthelmintic fenbendazole (fbz). to date, assessment of the efficacy has been inhibited by the inability to quantify uptake of fbz by the birds. we have developed a simple and sensitive hplc-ms-ms method for detecting and quantifying fbz and its metabolites from a 300 mg sample of red grouse liver. this method could be used to improve the efficacy of medicat ...201021236579
condition- and parasite-dependent expression of a male-like trait in a female bird.in many species, females display brightly coloured and elaborate traits similar to those that males use in intra- and inter-sexual selection processes. these female characters are sometimes related to fitness, and might function as secondary sexual characteristics that have evolved through sexual selection. here, we used descriptive data from 674 females in 10 populations and an experimental removal of trichostrongylus tenuis parasites in four populations, to examine the effects of season, age, ...201121247939
identification of genes responding to nematode infection in red grouse.the identification of genes involved in a host's response to parasite infection provides both a means for understanding the pathways involved in immune defence and a target for examining host-parasite co-evolution. most studies rely on a candidate gene approach derived from model systems to identify gene targets of interest, and there have been a dearth of studies geared towards providing a holistic overview of immune response from natural populations. we carried out an experiment in a natural p ...201121429137
The ornament-condition relationship varies with parasite abundance at population level in a female bird.Environmental heterogeneity is expected to create variation in the ornament-condition relationship. This topic has been studied in males with less attention being given to females. Here, we explore inter-population variation in the relationship between the size of a male-like trait, supra-orbital combs, and body mass in female red grouse Lagopus lagopus scoticus. We used the abundance of the nematode Trichostrongylus tenuis, a parasite with strong negative effects on this species, as a proxy of ...201121858505
the effect of parasites on wildlife.summary populations of animals which live in the wild are regulated by many biotic and abiotic factors. parasites are one of the biotic factors. parasites may influence their hosts in different ways. they may cause the death of the host due to a direct lethal effect or an indirect effect. direct lethal effects may occur if killing is a part of the life cycle of the parasite or if hosts and parasites have not developed an equilibrium. the introduction of hosts or parasites into a new environment ...199622077112
parasitized mates increase infection risk for partners.individuals can gain fitness benefits and costs through their mates. however, studies on sexual selection have tended to focus on genetic benefits. a potentially widespread cost of pairing with a parasitized mate is that doing so will increase an individual's parasite abundance. such a cost has been overlooked in systems in which parasites are indirectly transmitted. we manipulated the abundance of the nematode parasite trichostrongylus tenuis, an indirectly transmitted parasite, within pairs of ...201222617268
insights into population ecology from long-term studies of red grouse lagopus lagopus scoticus.long-term studies have been the backbone of population ecology. the red grouse lagopus lagopus scoticus is one species that has contributed widely to this field since the 1950s. this paper reviews the trajectory and profound impact that these studies have had. red grouse research has combined long-term studies of marked individuals with demographic studies over wide geographical areas and replicated individual- and population-level manipulations. a main focus has been on understanding the causes ...201423800249
experimentally elevated levels of testosterone at independence reduce fitness in a territorial bird.environmental conditions and individual strategies in early life may have a profound effect on fitness. a critical moment in the life of an organism occurs when an individual reaches independence and stops receiving benefits from its relatives. understanding the consequences of individual strategies at the time of independence requires quantification of their fitness effects. we explored this period in the red grouse (lagopus lagopus scoticus). in this system, testosterone and parasite (trichost ...201424933821
fine-scale population epigenetic structure in relation to gastrointestinal parasite load in red grouse (lagopus lagopus scotica).epigenetic modification of cytosine methylation states can be elicited by environmental stresses and may be a key process affecting phenotypic plasticity and adaptation. parasites are potent stressors with profound physiological and ecological effects on their host, but there is little understanding in how parasites may influence host methylation states. here, we estimate epigenetic diversity and differentiation among 21 populations of red grouse (lagopus lagopus scotica) in north-east scotland ...201424943398
digging for gold nuggets: uncovering novel candidate genes for variation in gastrointestinal nematode burden in a wild bird species.the extent to which genotypic variation at a priori identified candidate genes can explain variation in complex phenotypes is a major debate in evolutionary biology. whereas some high-profile genes such as the mhc or mc1r clearly do account for variation in ecologically relevant characters, many complex phenotypes such as response to parasite infection may well be underpinned by a large number of genes, each of small and effectively undetectable effect. here, we characterize a suite of novel can ...201525752450
genome-wide association and genome partitioning reveal novel genomic regions underlying variation in gastrointestinal nematode burden in a wild bird.identifying the genetic architecture underlying complex phenotypes is a notoriously difficult problem that often impedes progress in understanding adaptive eco-evolutionary processes in natural populations. host-parasite interactions are fundamentally important drivers of evolutionary processes, but a lack of understanding of the genes involved in the host's response to chronic parasite insult makes it particularly difficult to understand the mechanisms of host life history trade-offs and the ad ...201526179597
the role of parasite-driven selection in shaping landscape genomic structure in red grouse (lagopus lagopus scotica).landscape genomics promises to provide novel insights into how neutral and adaptive processes shape genome-wide variation within and among populations. however, there has been little emphasis on examining whether individual-based phenotype-genotype relationships derived from approaches such as genome-wide association (gwas) manifest themselves as a population-level signature of selection in a landscape context. the two may prove irreconcilable as individual-level patterns become diluted by high ...201626578090
the pervalence of caecal threadworms (trichostrongylus tenuis) in red grouse (lagopus lagopus scoticus).ninety percent of wild red grouse examined carried threadworms in their intenstinal caeca. old birds had 30 times as many worms as young birds. some infections were as high as 30,000 worms. the occurrence of worms in old grouse conformed to the negative binomial distribution.198328310590
parasites and scottish ptarmigan numbers.unlike red grouse (lagopus lagopus scoticus), which have almost 100% prevalence of the parasitic threadworm trichostrongylus tenuis and frequently high tapeworm numbers, 70% (n=71) of scottish ptarmigan (lagopus mutus) had no threadworms and only 4% had tapeworms. other parasites and pathogenic bacteria were infrequent. threadworms occurred in 12% (n=25) of birds on granite hills where mean ptarmigan densities were low, and in 43% (n=46) of birds over schists and limestones where mean densities ...199128313796
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