The effect of various periods of infection with the nematode Haemonchus contortus on the development of the nematode Nematodirus battus.
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Abomasum↗
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Results for “STRONGYLOIDEA”
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On the relationship between abomasal electrolytes and some population parameters of the nematodes Haemonchus contortus and Nematodirus battus.
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Abomasum↗
Extrinsic factors affecting the reproduction of Nippostrongylus brasiliensis.
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Anesthetics↗
Species richness in helminth communities: the importance of multiple congeners.
Using data sets derived from published literature, the contribution of congeneric species to helminth component community richness is evaluated. Consideration of the frequency distribution of congeners in relation to host and parasite groups reveals that the distributions are unimodal, that singletons are the commonest class and that the frequency of occurrence of congeners decreases with increasing number of species per genus. Congeners may be found in any group of hosts or parasites, but are more common amongst cestodes of aquatic birds. Two patterns of occurrence of congeneric species are recognized: one in which from a few to multiple congeners are found within a single helminth genus, exemplified by dactylogyrid monogeneans and cloacinid nematodes, and the other in which there is a simultaneous occurrence of congenerics and confamilials such that there are several genera involved, but each represented by fewer species, exemplified by strongyles in horses. The question of whether these patterns can be considered examples of species flocks is discussed. We conclude that multiple congeners and species flocks are interesting phenomena but, except in isolated cases, they make insignificant contributions to community richness.
Animals↗
SOME NEMATODA (STRONGYLINA AND OXYURINA) FROM KANGAROOS (MACROPUS SPP.) FROM EASTERN AUSTRALIA.
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Animals↗
Investigation of the chemosensory function of amphids of Syngamus trachea using electrophysiological techniques.
Syngamus trachea, the gape nematode, has been used as a model to study the chemosensory function of amphids. Extracellular electrophysiological recordings were performed directly on amphids. The amphids were stimulated by blood serum from a host bird and by D-tryptophan. The spike frequency produced by the amphid increased significantly after the application of the serum and the application of D-tryptophan. Two types of amphidial neurones responded to the presence of the stimuli. These extracellular recordings have verified the chemosensory function of the amphids.
Action Potentials↗
Analysis of the beta-tubulin codon 200 genotype distribution in a benzimidazole-susceptible and -resistant cyathostome population.
To study the prevalence of the polymorphism in position 200 of the beta-tubulin gene in the mechanism of benzimidazole (BZ) resistance in cyathostomes of horses, an allele-specific PCR was used to detect the genotype of individuals of BZ-susceptible and BZ-resistant populations. The molecular analysis of 100 adults recovered from an anthelmintic-naïve horse revealed 80% homozygous TTC/TTC individuals, 17% heterozygous TTC/TAC and 3% homozygous TAC/TAC. A naturally infected horse was treated with increasing fenbendazole (FBZ) dosages to select a BZ-resistant population of cyathostomes. The PCR based analysis of 3rd-stage larvae (L3) during the experiment revealed a decrease of the homozygous TTC/TTC genotype and an increase in heterozygous TTC/TAC and homozygous TAC/TAC individuals. After treatment 42.3% of the adults (n=104) were homozygous TTC/TTC, 55.8% were heterozygous TTC/TAC and only 1.9% showed the homozygous genotype TAC/TAC. The results of the molecular analysis lead to the proposal that polymorphism within codon 200 is not the only reason for the development of BZ resistance in small strongyles.
Alleles↗
TaqMan minor groove binder real-time PCR analysis of beta-tubulin codon 200 polymorphism in small strongyles (Cyathostomin) indicates that the TAC allele is only moderately selected in benzimidazole-resistant populations.
TaqMan minor groove binder probes were evaluated as to their suitability for the real-time allelic discrimination of the beta-tubulin codon 200 TTC/TAC single nucleotide polymorphism in cyathostomin species. Amplification of titrated cloned full-length beta-tubulin cDNA revealed that the TaqMan minor groove binder PCR is capable of specifically detecting as few as 10 copies. Testing of DNA from single adult and larval stages of several different species of cyathostomin allowed reproducible genotyping of individual worms. Using the real-time PCR approach, the throughput of samples was considerably increased compared with conventional post-PCR readout procedure. Only 7.8% homozygous TAC L3 were found among 102 L3 which were genotyped from phenotypically BZ-resistant small strongyle populations. The percentages of the homozygous TTC and heterozygous TTC/TAC were 41.3% and 50.9%, respectively. This resulted in a total TAC-allele percentage of only 33.3%. These findings correspond to data obtained by genotyping of an experimentally selected BZ-resistant cyathostomin population. It is concluded that the beta-tubulin codon 200 polymorphism is not the sole mechanism involved in the process of BZ resistance in cyathostomins.
Alleles↗
Definition of genetic markers in nuclear ribosomal DNA for a neglected parasite of primates, Ternidens deminutus (Nematoda: Strongylida)--diagnostic and epidemiological implications.
Ternidens deminutus (Strongylida) is a parasitic nematode infecting non-human and human primates in parts of Africa, Asia and the Pacific islands. The present study genetically characterized T. deminutus and defined genetic markers in nuclear ribosomal DNA (rDNA) as a basis for developing molecular-diagnostic tools. The sequences of the second internal transcribed spacer (ITS-2) of rDNA were determined for adult specimens of T. deminutus (Nematoda: Strongylida: Oesophagostominae) from the Olive baboon and the Mona monkey. The length and G+C content of the ITS-2 sequences was 216 bp and approximately 43%, respectively. While there was no sequence variation among individual T. deminutus specimens from the baboon, 6 (2.8%) nucleotide differences were detected in the ITS-2 between the parasite from baboon and that of the Mona monkey, which is similar to the difference (3.2%) between 2 other species of Oesophagostominae (Oesophagostomum bifurcum and O. stephanostomum) from non-human primates, suggesting significant population variation or the existence of cryptic (i.e. hidden) species within T. deminutus . Pairwise comparisons of the ITS-2 sequences of the 2 operational taxonomic units of T. deminutus with previously published ITS-2 sequences for selected members of the subfamilies Oesophagostominae and Chabertiinae indicated that species from primates (including those representing the subgenera Conoweberia and Ihleia) are closely related, in accordance with previous morphological studies. The sequence differences (27-48.3%) in the ITS-2 between the 2 taxonomic units of T. deminutus and hookworms (superfamily Ancylostomatoidea) enabled their identification and delineation by polymerase chain reaction (PCR)-based mutation scanning. The genetic markers in the ITS-2 provide a foundation for improved, PCR-based diagnosis of T. deminutus infections and for investigating the life-cycle, transmission patterns and ecology of this parasite.
Animals↗
The effects of a controlled-release albendazole capsule (Proftril-Captec) on parasitism in grazing Corriedale ewes in the Nyandarua district of Kenya.
The effects of intraruminal sustained-release capsules (IRSRCs) on parasitism in grazing Corriedale ewes were investigated over a period of 119 days (4 June-30 September 1993) using 40 ewes aged approximately 2 years and randomly divided into two groups of 20 ewes each. Each of the ewes in the treatment group received an IRSRC while the controls were left untreated. The groups were placed on adjacent 2.5-acre paddocks obtained by subdividing a 5.0-acre permanent pasture which had previously been grazed by young untreated sheep, so exposing both groups of ewes to a similar challenge from a contaminated paddock. The faecal egg counts, herbage larval counts and worm burdens of the major gastrointestinal parasites of sheep were significantly reduced by the use of the IRSRC. These parasitological effects were reflected in the increased live weight gains and heavier fleeces of the IRSRC-treated ewes. The control ewes required occasional salvage treatments during the trial period and the herbage on their paddock was heavily contaminated with infected larvae, reflected in the high worm burdens in the control ewes necropsied at the end of the trial and in tracer sheep introduced into the paddocks during the initial (day 30), interim (day 58) and final (day 89) stages of the experiment. Most capsules were exhausted within 95 days of administration, leading to a rise in the count of eggs per gram in the faeces in the treated group towards the end of the study.
Albendazole↗
The prevalence and intensity of helminth and coccidial infections in dairy cattle in central Kenya.
A survey of gastrointestinal parasite infections of young (< 6 months old), immature (6-12 months old) and adult (> 12 months old) dairy cattle on 16 farms in Kiambu District, Kenya was conducted during a dry season (September 1991 to January 1992) and during a wet season (March to July 1992). The survey was based on monthly coproparasitological examination of cohorts and worm counts in tracer calves. The effects of age, sex, farm and season on the prevalence and intensity of helminth and coccidial infections were determined. Faecal egg and oocyst counts revealed that the overall prevalences were: strongyles (including trichostrongyles) (85.5%), liver flukes (Fasciola gigantica) (34.0%), coccidia (30.9%) and tapeworms (9.6%). Eight species of the protozoan Eimeria were identified, the most prevalent species being E. bovis and E. zuernii. The most prevalent nematode genera were Haemonchus, Cooperia, Oesophagostomum and Trichostrongylus. Season, farm and age of the animals had a significant (p<0.05) influence on the intensity of infection with strongyles, liver flukes and coccidia, whereas the sex of the animals had no significant (p>0.05) effect on the prevalence or intensity of infections. A higher intensity of infection with strongyles and coccidia was found in the wet season than in the dry season (p<0.05). The age-specific intensity was in the following order: for strongyles, immature animals of 6-12 months of age had the highest egg counts, followed by young calves and adults. Calves had significantly (p<0.05) higher oocyst counts than immatures or adults. Liver fluke egg counts did not differ significant (p>0.05) between immatures and adult cattle.
Animals↗
Comparison of in vitro methods and faecal egg count reduction test for the detection of benzimidazole resistance in small strongyles of horses.
The objective of the study was to compare the in vitro egg hatch test (EHT), larval development test (LDT) and in vivo faecal egg count reduction test (FECR test) for the detection of benzimidazole resistance in equine strongyles. The presence of resistant or susceptible strongyle populations was determined in 25 stud farms using the in vivo FECR test and in vitro EHT. On the basis of the FECR values, resistance to fenbendazole was detected on 15 of the 25 farms (60%). The ED50 value (anthelmintic concentration producing 50% inhibition of hatching) for suspected resistant populations varied from 0.110 to 0.222 microg/ml thiabendazole (TBZ). Final LD50 values (anthelmintic concentration inhibiting development of 50% of eggs into L3 infective larvae) above 0.029 microg/ml TBZ in the in vitro larval development test on samples from 11 stud farms revealed the presence of populations of small strongyles suspected of being benzimidazole-resistant.
Animals↗
[Equine strongyles. I. Development of anthelmintic resistance].
Small strongyles (cyathostomes) that are resistant against anthelmintics have become a major problem in equine medicine in the recent years. In many European countries benzimidazole-resistant cyathostomes are widespread and are now present in well over 50% of equine populations investigated. In contrast, resistance against ivermectin has not been reported despite its widespread use in the recent years. Optimising the frequency of treatments based on quantitative faecal monitoring is of great importance to preserve remaining anthelmintic efficacy.
Animals↗
[Equine strongyles II. Occurrence of anthelmintic resistance in Switzerland].
The occurrence of anthelmintic resistance in strongyles was investigated in 440 horses on 90 farms in Switzerland. The egg hatch assay suggested that benzimidazole (BZ)-resistance was present in 40 of 82 farms (49%). Faecal egg count reduction after pyrantel-treatment was above 96% in 14 of 15 farms. In the remaining farm the efficacy was only 80%. Ivermectin efficacy was investigated on 5 farms and the efficacy was recorded at 98-100%. Faecal cultures undertaken after treatment revealed almost exclusively larvae of the family Cyathostominae. Data about management practices, pasture hygiene and anthelmintic usage were obtained with a questionnaire. Horses were treated on average 3.5 times per year. In 75% of the farms BZ were a component of the seasonal treatment schedule. Only the use of BZ had a significant correlation with the presence of BZ-resistance (P < 0.01). Recommendations for the control of equine strongyles should include measures that minimize the risk of resistance developing against remaining effective anthelmintics.
Animal Husbandry↗
Induction of immunity in mice to the nematode parasite, Nematospiroides dubius.
The data presented in this paper show that mice may be immunised against re-infection with Nematospiroides dubius by giving live third-stage larvae orally, intravenously, intraperitoneally or subcutaneously. Immunity is directed not against the adult worm but against third-stage larvae following their penetration of the wall of the intestine.
Administration, Oral↗
Immunity to Nematospiroides dubius: cell and immunoglobulin changes associated with the onset of immunity in mice.
The effect of one or more immunising infections on the susceptibility of mice to a subsequent challenge dose of Nematospiroides dubius larvae has been investigated. Following a single infection, animals developed a partial resistance characterized by their capacity to kill no more than half of the challenge dose of larvae. This low degree of immunity prevailed for some weeks after initial infection. A second immunising infection was found to induce a sudden increase in resistance such that at least 95% of a subsequent challenge dose of larvae was killed. This increase occurred 6 to 8 days after the second immunisation. Similar results were observed for mice immunised orally or intravenously. During the course of immunisations, absolute and differential cell levels in the blood and peritoneum as well as serum concentrations of the various immunoglobulin classes were determined. The results are considered in terms of the possible involvement of two distinct mechanisms of immunity to N. dubius, one requiring the participation of macrophages and the other, eosinophils.
Animals↗
Studies in vitro on the reaction of peritoneal exudate cells from mice immune to infection with Nematospiroides dubius with the infective third stage larvae of this parasite.
The results of the present study show that peritoneal exudate cells from mice immune to infection with Nematospiroides dubius are able in vitro to damage the third stage infective larvae as measured by a loss in infectivity. The ability of these cells to function in the absence of specific antibody seems to be related to the presence of trypsin labile factors on their surfaces. Lymphocytes from immune mice are also able to damage the larvae. The suggestion is made that 'activated' macrophages may play an important role in immunity to this infection.
Animals↗
Efficacy of ivermectin delivered via a controlled-release capsule against small lungworms (Protostrongylidae) in sheep.
To evaluate the efficacy of an ivermectin controlled-release capsule (CRC), which delivers 1.6 mg ivermectin per day intraruminally for 100 days to sheep weighing 40-80 kg (IVOMEC Maximizer CR Capsule for adult sheep, Merial), against small lungworms two studies with 48 naturally infected adult female Merino Landrace sheep were conducted. The sheep were allocated by restricted randomization based on bodyweight to untreated controls or received an ivermectin CRC. Eight sheep per group were necropsied 35, 70 or 105 days post-treatment. Lungworms were recovered by dissection or peptic digestion of the lungs. Baermann/Wetzel technique was used for faecal lungworm larval counts at weekly intervals. The efficacy of treatment was 100% against Dictyocaulus filaria and Protostrongylus rufescens (P < 0.05) at each necropsy day. The efficacy against Protostrongylus brevispiculum, Cystocaulus ocreatus and Neostrongylus linearis increased from 35 to 105 days after administration of the CRC and was found to be 100% (P < 0.01), 96.6% (P < 0.01) or 99% (P < 0.01), respectively, at 105 days post-treatment. The reductions of Muellerius capillaris counts varied and were 96.2% (P < 0.05) at 70 days post-treatment and 44.6% (P > 0.1) at 105 days post-treatment. Faecal lungworm larvae disappeared nearly completely from at least 3 weeks after the ivermectin CRC administration for all protostrongylid species including M. capillaris so that pasture infectivity will be subsequently significantly reduced.
Administration, Oral↗