The interaction of multiple environmental stressors affects adaptation to a novel habitat in the natterjack toad Bufo calamita

The potential to adapt to novel environmental conditions is a key area of interest for evolutionary biology. However, the role of multiple selection pressures on adaptive responses has rarely been investigated in natural populations. In Sweden, the natterjack toad Bufo calamita inhabits two separate distribution areas, one in southernmost Sweden and one on the west coast. We characterized the larval habitat in terms of pond size and salinity in the two areas, and found that the western populations are more affected by both desiccation risk and pond salinity than the southern populations. In a common garden experiment manipulating salinity and temperature, we found that toads from the west coast populations were locally adapted to shorter pond duration as indicated by their higher development and growth rates. However, despite being subjected to higher salinity stress in nature, west coast toads had a poorer performance in saline treatments. We found that survival in the saline treatments in the west coast populations was positively affected by larger body mass and longer larval period. Furthermore, we found negative genetic correlations between body mass and growth rate and their plastic responses to salinity. These results implicate that the occurrence of multiple environmental stressors needs to be accounted for when assessing the adaptive potential of organisms and suggest that genetic correlations may play a role in constraining adaptation of natural populations.

Inferring local adaptation from QST?FSTcomparisons: neutral genetic and quantitative trait variation in European populations of great snipe

We applied a phenotypic QST (PST) vs. FST approach to study spatial variation in selection among great snipe (Gallinago media) populations in two regions of northern Europe. Morphological divergence between regions was high despite low differentiation in selectively neutral genetic markers, whereas populations within regions showed very little neutral divergence and trait differentiation. QST > FST was robust against altering assumptions about the additive genetic proportions of variance components. The homogenizing effect of gene flow (or a short time available for neutral divergence) has apparently been effectively counterbalanced by differential natural selection, although one trait showed some evidence of being under uniform stabilizing selection. Neutral markers can hence be misleading for identifying evolutionary significant units, and adopting the PST-FST approach might therefore be valuable when common garden experiments is not an option. We discuss the statistical difficulties of documenting uniform selection as opposed to divergent selection, and the need for estimating measurement error. Instead of only comparing overall QST and FST values, we advocate the use of partial matrix permutation tests to analyse pairwise QST differences among populations, while statistically controlling for neutral differentiation.

A 3-year field evaluation of pasture rotation and supplementary feeding to control parasite infection in first-season grazing cattle—Dynamics of pasture infectivity

A 3-year grazing trial (2002-2004) was conducted on a commercial beef cattle farm in south-central Sweden to assess different methods of parasite control. This paper focuses on the dynamics of the free-living larval stages, whereas data on performance and within-host parasitological variables are presented in a complementary paper. Each year in May, 4 groups of 10 first-season grazing (FSG) steers were turned out on to separate 2ha paddocks and subjected to the following strategies: (1) spring turn-out on to pasture which had been grazed the previous year by second-season grazing (SSG) steers (paddock RT), followed by a move to aftermath (paddock AM) after 10 weeks (mid-July), (2) supplementary feeding with concentrate and hay for 4 weeks following turn-out (paddock FD), set stocked, (3) untreated control (paddock UT), set stocked and (4) anthelmintic treated control (paddock DO), set stocked. All paddocks were assigned a new set of FSG cattle each year whereas the treatments remained the same. Pasture infectivity were monitored partly by two tracer calves that grazed each paddock along with the FSG calves for 3 weeks after turn-out and prior to housing, partly by analysis of herbage samples for infective larvae (L3) that were collected from each paddock at monthly intervals between April and October. The predominant genera found were Cooperia and Ostertagia. Tracers grazing paddock RT overall harboured less worms, and in particular less Ostertagia spp., and tracers grazing paddock AM in mid-July harboured insignificant numbers of nematodes compared to tracers on the FD and UT paddocks. Although total worm counts varied between groups, smaller numbers were generally observed early in the grazing-season (May), compared to close to housing (September) when inhibited early L4 larvae were almost exclusively found. Results observed from herbage samples showed high numbers of L3 in spring before the time of turn-out, compared to around housing. In conclusion, the rotation control strategy showed promising results and provided a turn-out pasture that was 'nematode safe' to FSG cattle the following spring, whereas the feeding strategy failed as applied in this experiment.

A Field Study on the Effect of Some Anthelmintics on Cyathostomins of Horses in Sweden

The objective of the study was to investigate different aspects on the efficacy of three anthelmintics on cyathostomin nematodes of Swedish horses. A faecal egg count reduction (FECR) test was performed on 26 farms. Horses were treated orally with recommended doses of ivermectin, pyrantel pamoate or fenbendazole. Faecal samples were collected on the day of deworming and 7, 14 and 21 days later. No resistance was shown against ivermectin; the FECR was constantly >99%. The effect of pyrantel was assessed as equivocal in 6 farms 14 days after treatment; the mean FECR was 99%. As many as 72% of the fenbendazole-treated groups met the criteria for resistance; the mean FECR was 86%, ranging from 56% to 100%. A re-investigation of two farms where pyrantel resistance had been suspected clearly revealed unsatisfactory efficacy of pyrantel on one of these farms; the FECR varied from 72% to 89%. Twenty-six of the horses previously dosed with pyrantel or fenbendazole, and which still excreted >/=150 eggs per gram of faeces 14 days after treatment, were dewormed with ivermectin and fenbendazole or pyrantel in order to eliminate the remaining cyathostomins. A total of 13 cyathostomin species were identified from horses that initially received fenbendazole and seven species were identified from pyrantel-treated individuals. The egg reappearance period (ERP) following treatment with ivermectin and pyrantel was investigated on two farms. The shortest ERP after ivermectin treatment was 8 weeks and after pyrantel was 5 weeks. We conclude that no substantial reversion to benzimidazole susceptibility had taken place, although these drugs have scarcely been used (<5%) in horses for the last 10 years. Pyrantel-resistant populations of cyathostomins are present on Swedish horse farms, but the overall efficacy of pyrantel is still acceptable.

A 3-year field evaluation of pasture rotation and supplementary feeding to control parasite infection in first-season grazing cattle—Effects on animal performance

To evaluate non-chemical strategies to control pasture-borne parasites in first-season grazing (FSG) cattle, a 3-year grazing trial was conducted during 2002-2004 on naturally infected pastures on a commercial beef cattle farm in Sweden. A uniform pasture was divided in 4 equal 2 ha paddocks onto each of which 10, 5-9 months old dairy breed steer calves were allocated at turn-out in May each year. Two strategies were evaluated: (1) turn-out onto pasture which had been grazed the previous year by second-season grazing (SSG) steers, followed by a move to aftermath in mid-July (RT) and (2) supplementation with concentrate and roughage for 4 weeks from turn-out (FD). Comparisons were made with an untreated (UT), and an anthelmintic treated control group (DO). Animal parasitology and performance were monitored monthly throughout the 20 weeks grazing period. Additional sampling occasions were performed on day 9 (for coccidia) and 10 weeks after turn-out (mid-July). Due to clinical parasitic gastro-enteritis (PGE), salvage treatments were performed on all animals in group FD approximately 7 weeks after turn-out in 2003 and of three animals in group UT 5 weeks after turn-out in 2004. In 2003, the geometric mean oocyst excretion 9 days after turn-out was approximately 150,000 opg of mainly Eimeria alabamensis in group FD, and in 2004 approximately 180,000 opg in group UT. Apart from the DO group, geometric mean faecal egg counts (FEC) were between 80 and 400 epg 4 weeks after turn-out. Mean serum pepsinogen concentrations (SPC) of approximately 3.6 U tyrosine were recorded in the FD and UT groups from late August 2002. In 2003 and 2004, mean concentrations in these groups were between 4.1 and 7.2 U tyrosine 8 weeks after turn-out. By the end of the three grazing seasons the average weight gain difference compared to the DO group was for FD -29, -38 and -5 kg and for RT -4, -21 and +14 kg, and compared to the UT group -18, +2 and +22 for FD and +7, +19 and +41 kg for group RT. In conclusion, the rotation control strategy showed promising results, whereas the strategic feeding was poor from a parasite control standpoint.

DifferentialN-glycan- and protein-directed immune responses inDictyocaulus viviparus-infected and vaccinated calves

Calves with naturally acquiredDictyocaulus viviparusinfection mount an effective immune response. In the search for protection-inducing antigens, we found that severalD. viviparusthird-stage larval (L3) and adult ES products carry N-glycans. Deglycosylation of the worm antigens using PNGase F resulted in reduced IgA, IgE, IgG1 and IgG2 (but not IgM) reactivities in sera of primary infected animals, suggesting that the carbohydrate moieties contained immunodominant epitopes. Challenge infection resulted in increased specific serum antibody levels against ES and L3 in the re-infected and challenge control groups. Testing of sera by enzyme-linked immunosorbent assay (ELISA) demonstrated a significant increase in IgG1 and IgE (but not IgA or IgG2) reactivity against the deglycosylated antigens in the re-infected group compared with the challenge control group. Sera from calves vaccinated with irradiated larvae showed a strong anti-N-glycan response, but no booster response against the protein backbone after challenge infection, consistent with the absence of a memory response. Together, our results suggest thatD. viviparusproteins carry immunodominant N-glycan moieties that elicit a strong but short-lived immune response during infection and after vaccination, whereas the protein backbones effectively induce a memory response which results in a long-lasting, potentially protective immune response in re-infected, but not in vaccinated calves.

The development and overwintering survival of free-living larvae of Haemonchus contortus in Sweden

Five complimentary studies were undertaken with the overall aim to examine the ability of free-living stages of Haemonchus contortus to over-winter and tolerate cold stress. Two studies deal with the development and long-term survival of eggs and infective larvae of two geographically different isolates (Kenya and Sweden). Eggs and larvae were monitored in climatic chambers at temperatures that fluctuated daily between -1 degrees C and 15 degrees C, or at constant temperatures of 5 degrees C and 15 degrees C. The development from egg to larvae was dependent on temperatures over 5 degrees C. The long time survival was favoured at lower temperatures. Furthermore, the overwintering capacity of the free-living stages of these isolates was estimated under Swedish field conditions. Two groups of lambs were experimentally infected with different isolates, and kept separated on previously ungrazed plots. In early May the following year, two parasite-naive tracer lambs were turned out on each of the plots to estimate the pick up of overwintered larvae. This experiment was replicated in central and southern Sweden. In addition, two experiments were performed in 2003 on pasture previously grazed by naturally infected sheep. One trial was on a pasture in southern Sweden grazed by a commercial flock, where extreme numbers of H. contortus were found towards the end of the grazing season 2002. The other study was on a pasture plot in central Sweden grazed by a hobby flock in 2002, where three of six lambs died due to haemonchiasis. Overwintered H. contortus was recorded on three of four experimental sites. Worm burdens were in all instances extremely low. No differences in development and survival were found between the isolates. Consequently, overwintering on pasture is of no practical significance in the transmission of H. contortus between grazing-seasons in Sweden.

Population genetics of the bovine/cattle lungworm (Dictyocaulus viviparus) based on mtDNA and AFLP marker techniques

Mitochondrial DNA (mtDNA) sequence data and amplified fragment length polymorphism (AFLP) patterns were compared for the lungworm Dictyocaulus viviparus, a nematode parasite of cattle. Eight individual D. viviparus samples from each of 8 herds in Sweden and 1 laboratory isolate were analysed, with the aim of describing the diversity and genetic structure in populations using different genetic markers on exactly the same DNA samples. There was qualitative agreement between the whole-genome AFLP data and the mtDNA sequence data, both indicating relatively strong genetic differentiation among the Swedish farms. However, the AFLP data detected much more genetic variation than did the mtDNA data, even after allowing for the different inheritance patterns of the markers, and indicated that there was much less differentiation among the populations. The mtDNA data therefore seemed to be more informative about the most recent history of the parasite populations, as the general patterns were less obscured by detailed inter-relationships among individual worms. The 4 mtDNA genes sequenced (1542 bp) showed consistent patterns, although there was more genetic variation in the protein-coding genes than in the structural RNA genes. Furthermore, there appeared to be at least 3 distinct genetic groups of D. viviparus infecting Swedish cattle, 1 of which was predominant and showed considerable differentiation between farms, but not necessarily within farms. Second, the 2 smaller genetic groups occurred on farms where the predominant group also occurred, suggesting that these farms have had multiple introductions of D. viviparus.

Effects of single or concurrent infections with Eimeria alabamensis and gastrointestinal nematodes on the performance of calves on pasture

Twenty-four calves unexposed to pasture were allocated to four groups and inoculated with either two doses of 5 million Eimeria alabamensis oocysts at turn-out (E), 90,000 L3 of Ostertagia ostertagi and Cooperia oncophora divided on six occasions (N) or both oocysts and larvae as above (E + N). A control group was left uninoculated (C). For 10 weeks, the groups grazed in separate uniform paddocks not previously grazed by cattle. By day 5, most calves in groups E and E + N developed clinical coccidiosis that resulted in reduced weight gain compared to C and N. Mean trichostrongylid faecal egg counts in groups N and E + N never exceeded 300 eggs per gram of faeces, and average serum pepsinogen levels were less than 3.8 U tyrosine. This experiment demonstrates the potential impact of E. alabamensis on the performance of previously unexposed calves, whereas no aggravated effects were observed due to concurrent infections with gastrointestinal nematodes.

Phenotypic characterization of Haemonchus contortus: a study of isolates from Sweden and Kenya in experimentally infected sheep

The effects of cold storage of infective third-stage larvae (L3) of different isolates of the parasitic nematode Haemonchus contortus were studied with respect to infectivity, pre-patent period and propensity for larval arrestment. Two complementary experiments were conducted with 2 groups of lambs, each animal being inoculated with 2000 L3 of either Swedish or Kenyan origin. In a first experiment, L3s were cold treated at 5 °C for 9 months prior to infection, whereas in a second experiment larvae were newly hatched. Individual faecal egg counts (FECs), and worm burdens were determined for each experiment. The results showed that the greatest differences were associated with the pre-treatment of larvae. The pre-patent period and the FECs differed significantly between the experiments but not between the isolates used in each experiment. However, the extent of hypobiosis was significantly different between the two isolates when fresh larvae were used (36% Kenyan isolate and 70% Swedish). The storage of H. contortus at 5 °C had no apparent effect on the infectivity of L3s, as high establishment ranging from 43 to 74% were observed, irrespective of isolates used. This study showed that H. contortus exhibited similar phenotypic traits regardless of geographical origin. Thus, there was limited evidence for adaptations to temperate climatic conditions.

Mononuclear cell subsets in bronchoalveolar lavage fluid during Dictyocaulus viviparus infection of calves: a potential role for gamma/delta TCR-expressing cells in airway immune responses?

Mononuclear cell populations in the lungs of calves infected with Dictyocaulus viviparus were studied during primary infection and reinfection in order to identify cells involved in development of protective immunity to parasitic bronchitis. Three groups of calves were either inoculated with 500 third-stage larvae at both weeks 0 and 10 (n = 6), inoculated only at week 10 (n = 6), or remained uninfected (n = 3). The animals were monitored weekly by collection of bronchoalveolar lavage fluid (BALF), blood and faeces. Among mononuclear BALF-cell populations, the gamma/delta TCR-expressing cells showed a pronounced transient increase in proportion as well as in relative cell size 2 weeks post primary infection, whereas CD4-, CD8-, Ig- and CD14-expressing cells showed no significant differences related to the infection. The increase in gamma/delta TCR-expressing cells coincided with significantly increased proportions of eosinophils and recovery of adult worms in BALF. After reinfection, gamma/delta TCR-expressing cells increased again, but not until week 3 post inoculation, whereas eosinophils were increased by week 2 and reached higher levels than after primary infection. After reinfection, establishment of D. viviparus was less successful than after primary infection. In conclusion, these results indicate a role for gamma/delta TCR-expressing lymphocytes in the pathogenesis of D. viviparus infection.

Testing the hypothesis of recent population expansions in nematode parasites of human-associated hosts

It has been predicted that parasites of human-associated organisms (eg humans, domestic pets, farm animals, agricultural and silvicultural plants) are more likely to show rapid recent population expansions than are parasites of other hosts. Here, we directly test the generality of this demographic prediction for species of parasitic nematodes that currently have mitochondrial sequence data available in the literature or the public-access genetic databases. Of the 23 host/parasite combinations analysed, there are seven human-associated parasite species with expanding populations and three without, and there are three non-human-associated parasite species with expanding populations and 10 without. This statistically significant pattern confirms the prediction. However, it is likely that the situation is more complicated than the simple hypothesis test suggests, and those species that do not fit the predicted general pattern provide interesting insights into other evolutionary processes that influence the historical population genetics of host-parasite relationships. These processes include the effects of postglacial migrations, evolutionary relationships and possibly life-history characteristics. Furthermore, the analysis highlights the limitations of this form of bioinformatic data-mining, in comparison to controlled experimental hypothesis tests.

Major histocompatibility complex variation and mate choice in a lekking bird, the great snipe (Gallinago media)

Genes of the major histocompatibility complex (MHC) play a major part in the activation of the vertebrate immune system. In addition, they also appear to function as cues for mate choice. In mammals especially, several kinds of MHC-dependent mate choice have been hypothesized and observed. These include choice of mates that share no or few alleles with the choosing individual, choice of mates with alleles that differ as much as possible from the choosing individual, choice of heterozygous mates, choice of certain genotypes and choice of rare alleles. We investigated these different aspects of mate choice in relation to MHC in a lekking bird species, the great snipe (Gallinago media). We found no evidence for MHC disassortative mating, no preference for males with many MHC alleles and no preference for rare alleles. However, we did find that some allelic lineages were more often found in males with mating success than in males without mating success. Females do not seem to use themselves as references for the MHC-dependent mate choice, rather they seem to prefer males with certain allele types. We speculate that these alleles may be linked to resistance to common parasites.

Acute phase proteins in response to Dictyocaulus viviparus infection in calves

Three experiments were carried out to examine the acute phase response, as measured by the acute phase proteins (APP) haptoglobin, serum amyloid A (SAA) and fibrinogen, in calves infected with lungworm, Dictyocaulus vivparus. In addition, eosinophil counts were analysed. Three different dose models were used in 3 separate experiments: I) 250 D. viviparus infective third stage larvae (L3) once daily for 2 consecutive days, II) 100 D. viviparus L3 once daily for 5 consecutive days, and III) 2000 L3 once. All 3 dose regimes induced elevated levels of haptoglobin, SAA and fibrinogen, although there was considerable variation both between and within experiments. A significant increase was observed in all 3 APP at one or several time points in experiment I and III, whereas in experiment II, the only significant elevation was observed for fibrinogen at one occasion. The eosinophil numbers were significantly elevated in all 3 experiments. The results show that lungworm infection can induce an acute phase response, which can be monitored by the selected APP. Elevated APP levels in combination with high numbers of eosinophils in an animal with respiratory disease may be used as an indicator of lung worm infection, and help the clinician to decide on treatment. However, high numbers of eosinophils and low levels of APP do not exclude a diagnosis of lungworm. Thus, lungworm infection may not be detected if measurements of APP are used to assess calf health in herds or individual animals.

Evaluation of anthelmintic properties of some plants used as livestock dewormers against Haemonchus contortus infections in sheep

Gastrointestinal helminth infections remain a major constraint to livestock production globally. This study evaluated anthelmintic efficacy of 7 plants used as dewormers by farmers and pastoralists in Kenya. Thus 3 commercial anthelmintics and 7 plant preparations were tested in lambs infected with 5000 or 3000 L3 Haemonchus contortus in 4 experiments. In the first experiment, ivermectin, levamisole and albendazole were tested in 46 lambs. Seven plant preparations of Hagenia abyssinica, Olea europaea var. africana, Annona squamosa, Ananas comosus, Dodonea angustifolia, Hildebrandtia sepalosa and Azadirachta indica were tested in 151 lambs in 3 experiments. All 3 anthelminitics were highly effective in reducing faecal egg counts (FEC) and total worm counts (TWC) in lambs. Plant preparations had varying levels of crude proteins from 2.6% for O. europaea to 18.4% for A. indica. Compared with controls, no significant reductions in FEC were observed for any of the treated groups either 2 or 3 weeks post-treatment. Lambs treated with A. squamosa and A. comosus were slaughtered 4 weeks post-treatment. No significant differences were observed in mean TWC or number of eggs per female worm between treated animals and the controls. No significant improvements in weight gain were observed in treated lambs.

Disintegration of dung pats from cattle treated with the ivermectin anthelmintic bolus, or the biocontrol agent Duddingtonia flagrans

An experiment was performed during the grazing seasons of 1998, 1999 and 2000 to study the influence of the antiparasitic drug ivermectin and the nematophagous fungus Duddingtonia flagrans on cattle dung disintegration. The faeces originated from groups of animals that were part of a separate grazing experiment where different control strategies for nematode parasite infections were investigated. Each group consisted of 10 first-season grazing cattle that were either untreated, treated with the ivermectin sustained-release bolus, or fed chlamydospores of D. flagrans. Faeces were collected monthly on 4 occasions and out of pooled faeces from each group, 4 artificial 1 kg dung pats were prepared and deposited on nylon mesh on an enclosed pasture and protected from birds. The position of the new set of pats was repeated throughout the 3 years of the study. Each year, the dung pats were weighed 4, 6, 8 and 10 weeks after deposition and immediately afterwards replaced to their initial positions.

Results showed that there was no difference in faecal pat disintegration between groups. However, the time-lag between deposition and complete disintegration of the faeces varied significantly between deposition occasions. Dung pats disappeared within 2 weeks (visual observation) when subjected to heavy rainfall early after deposition, whereas an extended dry period coincided with faeces still remaining 12 months after deposition.

Genetic diversity assessed by amplified fragment length polymorphism analysis of the parasitic nematode Dictyocaulus viviparus the lungworm of cattle

We have examined the population genetic structure in a collection of nine isolates of the parasitic lungworm Dictyocaulus viviparus. Eight of the isolates were sampled from cattle in geographically separated farms throughout south-central Sweden, and one isolate was a laboratory strain that has been maintained in experimentally infected calves for almost four decades. A total of 72 worms were examined, with eight individual worms from the same individual host representing each isolate. The genetic variation as revealed by amplified fragment length polymorphism analysis using four selective primer combinations was high. Depending on the primer combination a total of 66-79 restriction fragments were amplified, with 26-44 peaks of similar complexity from each of the isolates. The heterozygosity within populations was relatively small, as were the population mutation and immigration rates, which seemed to be in neutral equilibrium. The genetic diversity was therefore reasonably well structured in the field; and the laboratory isolate was quite distinct from the field samples. There was no relationship between the patterns of genetic diversity and the geographical proximity of the farms. The estimates of heterozygosity were much larger and more consistent than those previously estimated for this nematode species using mitochondrial sequencing, and the genetic structuring was thus much less pronounced and the gene flow greater. We attribute these differences in estimation to the broader sampling of loci available using amplified fragment length polymorphism markers, which may therefore constitute a superior technique for the study of patterns of lungworm diversity. Furthermore, the data estimating gene flow for D. viviparus was less than previously reported for closely related species in North America. This might be related to different rates of movements of infected hosts. It seems likely that lungworm infections are rather persistent on different farms, and the sudden outbreaks of disease that can be observed with host movements are most likely to be related to the introduction of susceptible stock.

Expulsion of small strongyle nematodes (cyathostomin spp) following deworming of horses on a stud farm in Sweden

This study was conducted on a stud farm in Sweden to investigate the species composition of cyathostomins expelled in the faeces of horses after deworming using three different anthelmintic preparations. Twenty-seven horses excreting > or = 200 strongyle eggs per gram faeces (EPG) were divided into three comparable groups and dewormed on day 0 with either of following compounds: 0.2 mg ivermectin per kg body weight (bw), 19 mg pyrantel pamoate per kg bw or 7.5 mg fenbendazole per kg bw. For each of the 3 days following anthelmintic treatment faeces was collected from individual horses and subsamples were fixed in formalin. Four days after the anthelmintic treatment all horses were re-treated with ivermectin and faeces was collected on day 5. Individual subsamples from each of the four sampling occasions were examined for cyathostomin nematodes. Sixty-three to 270 worms per horse were identified to the species level. The majority of the worms recovered were expelled during the first day from horses treated with ivermectin or pyrantel pamoate, and during the second day from horses treated with fenbendazole. Fifteen cyathostomin species were identified and the six most prevalent were Cylicocyclus nassatus, Cyathostomum catinatum, Cylicostephanus longibursatus, Cylicocyclus leptostomus, Cylicostephanus minutus and Cylicostephanus calicatus. These species composed 91% of the total burden of cyathostomins. The number of species found per horse ranged from 6 to 13, with an average of 9. No significant differences in species composition or distribution were found between the treatment groups. On day 5, i.e. 1 day after the last ivermectin treatment, 93% of the adult worms were recovered from horses in the fenbendazole group. This study showed that it was possible to identify cyathostomins expelled in faeces of dewormed horses, and that the most prevalent species corresponded to those found in autopsy surveys performed in other countries.

Phylogeny of Dictyocaulus (lungworms) from eight species of ruminants based on analyses of ribosomal RNA data

In this study, we conducted phylogenetic analyses of nematode parasites within the genus Dictyocaulus (superfamily Trichostrongyloidea). Lungworms from cattle (Bos taurus), domestic sheep (Ovis aries), European fallow deer (Dama dama), moose (Alces alces), musk ox (Ovibos moschatus), red deer (Cervus elaphus), reindeer (Rangifer tarandus) and roe deer (Capreolus capreolus) were obtained and their small subunit ribosomal RNA (SSU) and internal transcribed spacer 2 (ITS2) sequences analysed. In the hosts examined we identified D. capreolus, D. eckerti, D. filaria and D. viviparus. However, in fallow deer we detected a taxon with unique SSU and ITS2 sequences. The phylogenetic position of this taxon based on the SSU sequences shows that it is a separate evolutionary lineage from the other recognized species of Dictyocaulus. Furthermore, the analysis of the ITS2 sequence data indicates that it is as genetically distinct as are the named species of Dictyocaulus. Therefore, either this taxon needs to be recognized as a new species, or D. capreolus, D. eckerti and D. viviparus need to be combined into a single species. Traditionally, the genus Dictyocaulus has been placed as a separate family within the superfamily Trichostrongyloidea. The present molecular phylogenetic analyses support the placement as a separate family, but the current data do not support the placement of the Dictyocaulidae within the Trichostrongyloidea without a reassessment of the placement of the superfamily Strongyloidea. While D. eckerti has been regarded as the one and only lungworm species of cervids, this study showed that 4 host species including 3 members of Cervidae (moose, reindeer, red deer) and 1 Bovidae (musk ox) were infected with this parasite. Host ranges of D. viviparus (cattle), D. filaria (sheep) and D. capreolus (moose and roe deer) were more restricted. No clear pattern of co-evolution between the dictyocaulid taxa and their bovid and cervid hosts could be determined.

From connectivity to isolation: genetic consequences of population fragmentation in capercaillie across Europe

The capercaillie inhabits a continuous range in large parts of the Palearctic boreal forest, but is patchily distributed in temperate Europe. An ongoing population decline, largely related to human land use changes, has been most pronounced in central and western Europe, where some local populations have become extinct. In this study, we document the genetic differentiation of capercaillie populations at different stages along a gradient of spatial structuring from high connectivity (continuous range in the boreal forest) to a metapopulation systems (Alps) and recent (central Europe) and historic (Pyrenees) isolation. Four hundred and sixty individuals from 14 sample sites were genotyped at 10 polymorphic microsatellite loci to assess genetic structure and variation of capercaillie populations across its European range. As expected, differentiation was least pronounced within the continuous range in the boreal forest. Within the metapopulation system of the Alps, differentiation was less than among the isolated populations of central Europe (Black Forest, Fichtelgebirge, Thuringia, Vosges). In the long-isolated population of the Pyrenees, and the recently isolated populations of central Europe, genetic diversity was significantly reduced compared with the Alps and boreal forest. Our results agree with the concept of a gradual increase in genetic differentiation from connectivity to isolation, and from recent to historic isolation. Anthropogenic habitat deterioration and fragmentation thus not only leads to range contractions and extinctions, but may also have significant genetic and evolutionary consequences for surviving populations. To maintain high levels of genetic variation in species in fragmented habitats, conservation should aim at securing connectivity between spatially distinct populations.

Evolution of high-level, multiple anthelmintic resistance on a sheep farm in Malaysia

Anthelmintic resistance in nematode parasites of sheep and goats on a government farm in north Malaysia was monitored over a 3-year period (1997-2000). The faecal egg count reduction test (FECRT) was conducted on young sheep at the beginning and end of this period. Changes in management, designed to reduce the selection pressure for the development of anthelmintic resistance, were also implemented during this time. By far the most important parasite problem was Haemonchus contortus. In 1997, this nematode was found to be resistant to levamisole, with suspected resistance to closantel and moxidectin. However, when the FECRT was repeated 3 years later, its resistance status had become much more severe, with resistance to benzimidazole, levamisole and ivermectin, and suspected resistance to moxidectin. This rapid evolution to multiple anthelmintic resistance is a major concern that needs to be arrested. There is an urgent need to evaluate other control strategies that incorporate livestock management, the 'smart' use of drugs and non-chemotherapeutic approaches, such as biological control agents.

Dictyocaulus capreolus n. sp. (Nematoda: Trichostrongyloidea) from roe deer, Capreolus capreolus and moose, Alces alces in Sweden

Dictyocaulus capreolus n. sp. recovered from roe deer, Capreolus capreolus and moose, Alces alces in Sweden is described and figured. Morphological studies revealed the new species to be closest to D. eckerti and D. africanus on the basis of mouth shape, all three species having an elongate mouth opening. The other species of the genus, including D. viviparus, all have a circular to oval mouth opening. Dictyocaulus capreolus n. sp. can be distinguished from D. eckerti and D. africanus on the basis of the morphology of the buccal capsule and the bursa. These morphological studies support earlier evidence of the presence of a new species of Dictyocaulus in roe deer and moose that could be distinguished from D. eckerti and D. viviparus using either a PCR-linked hybridization assay or image analysis software to study the dimensions of the buccal capsule.

Heterologous transmission with Dictyocaulus capreolus from roe deer (Capreolus capreolus) to cattle (Bos taurus)

Eight Swedish Red Breed cattle, about 2 months old, were experimentally infected with a Swedish isolate of Dictyocaulus viviparus (Dviv-Se) from cattle and D. capreolus from roe deer. The aims were to determine whether the roe deer lungworm is infective to cattle or if it can induce seroconversion in cattle against D. viviparus as measured with an ELISA. Four calves which were given 500 Dviv-Se infective larvae (L3) each by larval dosing for two successive days developed patent infection between days 23 and 25 post-inoculation (PI). Larval output varied among the calves and during the patent period. However, maximum recovery occurred between 28 and 56 days PI with peak shedding on day 37 PI. Shedding ceased at day 58 PI and adult worms were recovered from one calf at necropsy (day 67 PI). No immature worms were recovered from the lungs at necropsy. Seroconversion was detected on days 35-42 PI. One Dviv-Se infected calf became seronegative on day 67 PI whereas the other calves still remained seropositive during this period. Prepatency and patency periods of D. viviparus and serological findings in this study basically conform to previous studies. Each calf that was infected with 400 L3 of D. capreolus for two successive days, and about 800 L3 of the same species about 8 weeks later, did not develop to patency based on faecal and post-mortem examinations. Consequently, under the conditions of this study, D. capreolus was not infective to cattle. Two of the four calves that were infected with L3 from roe deer were challenged with L3 cultured from faeces of the Dviv-Se-infected calves. This infection did not develop to patency. Whether this was due to cross-protection as a result of the prior priming with L3 from roe deer is not clear. However, if it is so, it opens up the possibility of using D. capreolus L3 for preventing bovine dictyocauliasis.

Effect of permethrin impregnated plastic strips on Dermanyssus gallinae in loose-housing systems for laying hens

The effect of permethrin impregnated plastic strips (Die No Mite Strips) was evaluated on Dermanyssus gallinae populations in aviary systems for layers in Sweden. Two application strategies of the strips were tested: (A) attached in the housing system, allowing the birds to rub against the strips and thereby get the acaricide released onto their plumage, and (B) attached out of reach of the hens, at two different sites (perches and egg-belt lids) of the inner surfaces of the system, where the mites sheltered during the day. On two farms with 2030 (A) and 3384 (B) hens, and existing mite populations, strips were mounted for 20 and 10 weeks, respectively, and mite numbers were monitored by traps. With application A an overall mite reduction of 53% was observed, while with B the mean mite numbers decreased by 39% at the perches and 92% at the egg-belt lid. The strips were originally designed for caged hens afflicted by ectoparasites that stay on the host for most of their life cycle. However, since D. gallinae spends most of its time off the host, it was not possible to control the parasite with application A. Resistance tests performed on mites from both treated and control compartments where application A was used showed no indication of resistance to permethrin, while 95% of the mites survived a 48 h exposure to the compound where application B was performed. Thus, permethrin resistant mites appeared to be the main reason for the failure to control D. gallinae with application B.