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At least 19 recordsLinked to original sources
PubMed1992

A preliminary study of the effect of microclimate on third-stage larvae of Haemonchus contortus and Haemonchus placei on irrigated pasture.

Assessments were made on the influence of several microclimatic variables on the availability of third-stage larvae of Haemonchus contortus and Haemonchus placei on four strata of irrigated Kikuyu pasture. Three replicates of these pasture samples were collected on 18 sample days over 12 months and the log10 mean counts of the larvae recovered were analysed by a step-wise regression model. Predictors for the log counts of the four strata for the two nematode species included relative humidity, illumination, air temperature and windspeed. The effect of air temperature on larvae of both Haemonchus species was similar; as air temperature increased, the number of larvae on pasture increased. The inverse was true for windspeed; as windspeed increased larval counts decreased. For H. contortus, relative humidity increased as the number of larvae increased on all strata except upper herbage. The R2 values ranged from 0.11 to 0.21 for H. contortus and from 0.04 to 0.12 for H. placei. Under the conditions of this study, only 21% of the effect on H. contortus and 12% on H. placei third-stage larvae on pasture can be explained by microclimatic conditions.

Animals↗
PubMed1991

Effects of time of day, season and stratum on Haemonchus contortus and Haemonchus placei third-stage larvae on irrigated pasture.

The effect of time of day, season and stratum of herbage and soil on the availability of Haemonchus contortus and Haemonchus placei third-stage larvae (L3) on pasture was assessed. Feces from infected calves and lambs were placed on pasture plots and samples of upper herbage, lower herbage, mat and soil were collected at five intervals per day throughout the daylight hours on 18 sample days over 12 months. Using recovery rate factors derived from a preliminary investigation on the efficacy of larval recovery from each stratum, the data on larval recoveries were analyzed for the effect of season, time and stratum, and their interactions. Significant (P less than 0.05) differences were found for season, stratum and the season-with-stratum interaction for both parasites. No significant differences were detected for larval counts at different times of the day. Larval recoveries of H. contortus were larger throughout the study than those of H. placei. Most H. contortus L3 were recovered in the summer and autumn, and H. placei in the spring and summer. For both parasites, the recoveries of larvae from the upper and lower herbage were larger than those from the mat and soil. The implications of these findings are discussed in terms of control strategies.

Animals↗
PubMed1997

Haemonchus placei and Haemonchus contortus are distinct species based on mtDNA evidence.

Debates continue over the extent to which the parasitic trichostrongylids Haemonchus placei and Haemonchus contortus hybridise in nature, and whether they deserve species status. Mitochondrial ND4 gene sequences from individuals of each putative species collected from populations around the United States indicate that the two species are highly differentiated at the mtDNA level. Furthermore, there was no evidence of introgressive hybridisation occurring in wild populations.

Amino Acid Sequence↗
PubMed2002

Redescriptions of Haemonchus mitchelli and Haemonchus okapiae (Nematoda: Trichostrongyloidea) and description of a unique synlophe for the haemonchinae.

In the course of a revision of Haemonchus Cobb, 1898 (Nematoda), commonly referred to as large stomach worms, significant new morphological information was discovered that allows the recognition of 2 species believed for more than 50 yr to be synonymous. Both species, Haemonchus mitchelli Le Roux, 1929, from the eland Taurotragus oryx and other African ruminants and H. okapiae van den Berghe, 1937, from the okapi Okapia johnstoni, have a synlophe of 42 ridges, but the synlophe of H. mitchelli is longer than that of H. okapiae. The distal tip of the left spicule of H. mitchelli bears a barb that is about twice as long as the short barb and half as long as the long barb on the right spicule. In contrast, the barb on the left spicule of H. okapiae is similar in size to the short barb and about 25% as long as the long barb of the right spicule. The dorsal ray of H. mitchelli is bifurcated distally for 25-39% (32%) of its length and its stem is expanded proximally, but the dorsal ray of H. okapiae is bifurcated 37-50% (42%) and its stem is of uniform thickness.

Animals↗
PubMed1995

Microclimatic effect on vertical migration of Haemonchus contortus and Haemonchus placei third-stage larvae on irrigated Kikuyu pasture.

The influence of microclimate on numbers of third-state larvae of haemonchus contortus and Haemonchus placei in four strata of irrigated Kikuyu pasture was assessed. On 36 different, interspersed days three replicates of pasture samples were collected on three occasions per day from 1990-1992 for larval recovery and the log10 mean counts of the larvae recovered were analysed by use of ANOVA models. Because the ground-surface area from which herbage was collected was standardized, estimated larval counts for the different strata could be compared; this was not possible in our previous studies. For H. contortus, the estimated larval counts in the four strata were predicted by microclimatic air temperature, relative humidity and soil moisture, with the coefficient-of-determination (R2) values ranging from 0.15-0.35. Of these, air temperature had the greatest effect. The same three predictors, together with illumination and wind speed, featured for H. placei, with R2 values of 0.19-0.52. With the exception of wind speed and illumination, which (for H. placei) had the opposite effect, all the microclimatic parameters listed, predicted an increase in numbers of larvae from a lower to an upper strata.

Africa↗
PubMed2003

Host specificity of Haemonchus spp. for domestic ruminants in the savanna in northern Ivory Coast.

Three Haemonchus species (Haemonchus contortus, Haemonchus placei and Haemonchus similis) live in sympatry in the savanna of North Côte d'Ivoire. Four domestic ruminant hosts (zebu-cattle, taurine-cattle, sheep and goats) share the same pastures throughout the year. Our post-mortem data imply that a Haemonchus spp. circulation exists among the different hosts species in the savanna of North Côte d'Ivoire. Under field conditions, mixed congeneric infections were the rule except in sheep where mono-specific H. contortus infections were the most frequent. The associations H.contortus+H.placei and H.placei+H.similis were dominant in goats and in cattle, respectively. In the populations examined, triple infections occurred in 11.5% of zebu-cattle and 29% of the taurine-cattle. Considering the intensities of infections, H. contortus was the main Haemonchus species of sheep and goats whereas H. similis was very rare in these host species. About 10% of the worms recovered in goats belong to the H. placei species. In cattle, H. contortus was very rare. H. placei was the dominant species in zebu-cattle (58.7% of the identified worms) and in taurine-cattle (73.9%) nevertheless, the proportion of H. similis was higher in zebu-cattle (38.6%) than in taurine-cattle (21.3%). Only few hybrids between H. placei and H. similis were found. The importance of such Haemonchus spp. circulation is discussed.

Animals↗
PubMed1998

Host range and the maintenance of Haemonchus spp. in an adverse arid climate.

Three Haemonchus species (Haemonchus contortus, Haemonchus placei and Haemonchus longistipes) live in sympatry in Sahelian areas such as Mauritania (West Africa). Four host species (dromedary, zebu cattle, sheep and goats) share the same pastures for several months per year. Experimental infection by H. contortus or H. placei was achieved only poorly in dromedaries, and H. contortus or H. longistipes infection failed to establish in zebu cattle. Conversely, H. placei and H. longistipes successfully infected sheep and goats. Under field conditions, mixed congeneric infections were very rare in dromedaries but frequent in zebu cattle (H. contortus represented 16% of Haemonchus spp. burden), in sheep (H. placei: 15%) and in goats (H. placei: 9% and H. longistipes: 6% of worms). The importance of the different host species was evaluated for Haemonchus spp.: small ruminants are the main hosts of H. contortus, dromedaries harboured the large majority of H. longistipes worms but 5% of them were found in goats which seemed to be additional hosts. The most striking finding was the role played by the small ruminants in the survival strategy of H. placei in Sahelian regions: 56% of the total of H. placei worms were found in sheep, 34% in goats and only 10% in zebu cattle. These results are consistent with the hypothesis that the extension of host range plays an important role in the survival strategy of H. placei, whereas H. longistipes or H. contortus might well survive utilising their usual hosts.

Animals↗
PubMed2000

Relative protective properties of three membrane glycoprotein fractions from Haemonchus contortus.

Jacalin lectin was used as a ligand to isolate a fraction containing two distinct protective antigens from detergent extracts of membranes from Haemonchus contortus. The first antigen was identified as a complex which appeared very similar to Haemonchus galactose-containing glycoprotein (H-gal-GP), which is a previously described protective protease complex, except that it was substantially depleted of one of the main H-gal-GP components, a 230 kDa metallopeptidase-containing band. The new complex was termed Haemonchus sialylated galactose-containing glycoprotein (H-sialgal-GP), because it bound to jacalin but not to peanut lectin and only jacalin will bind the sialylated form of galactosyl (beta-1, 3) N-acetylgalactosamine. Two protection trials with sheep showed that H-sialgal-GP and H-gal-GP were equally efficacious, reducing numbers of Haemonchus eggs by between 86% and 93% and worms by between 52% and 75%, respectively. The second jacalin-binding protective antigen fraction was separated from H-sialgal-GP by ion exchange and gel filtration chromatography. It was greatly enriched for two proteins termed p46 and p52 according to their apparent molecular weights. Immunization of sheep with these proteins gave protection values of 78% for eggs and 33% for worms, which are significantly lower than those obtained with either H-gal-GP or H-sialgal-GP. N-terminal amino acid sequence data from p46 and p52 showed that both proteins were closely related to a previously described 45 kDa Haemonchus membrane protein, which had conferred protection against Haemonchus in guinea-pigs.

Amino Acid Sequence↗
PubMed1999

A hybridisation technique to identify anthelmintic resistance genes in Haemonchus.

The identification of genes associated with anthelmintic resistance can be facilitated in Haemonchus contortus by the ability of this species to hybridise with Haemonchus placei. Although the hybrid males are sterile, the lines can be rescued by backcrossing the females to either parental species. Resistance genes can be retained in Haemonchus hybrids, while the unwanted contortus background is removed through backcrossing to H. placei and anthelmintic selection of the progeny. Under this selection, genes involved in resistance would retain the H. contortus nucleotide sequence, while those that are not would either be H. placei or a random mixture of both, depending on the amount of backcrossing that had occurred. The first candidate gene to be tested in this system was a Haemonchus P-glycoprotein, hcpgp-1. hcpgp-1 was amplified, cloned and sequenced from H. contortus and H. placei. Two restriction sites were then identified in the sequenced product; one specific to H. contortus hcpgp-1 and the other found only in the H. placei gene. These genes were identified from macrocyclic lactone selected and non-selected worms by restricting PCR products from individual worms. Fitted occurrence of the H. contortus allele was 49% of unselected worms and 69% of macrocyclic lactone selected worms. The probability of this percentage occurring by chance was P = 0.006. Thus macrocyclic lactone selection was acting to increase the percentage of hcpgp-1 from macrocyclic-lactone-resistant CAVRS.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2001

Expression of Haemonchus contortus pepsinogen in Caenorhabditis elegans.

A genomic copy of a gut-expressed Haemonchus contortus candidate vaccine antigen, pepsinogen, was isolated using the polymerase chain reaction (PCR). The isolated sequence was 4 kb in length and contained eight introns ranging in size from 54 to 1475 base pairs. This sequence, together with its 3' non-coding DNA region containing a polyadenylation signal sequence, was cloned into the Bluescript SK(+) vector immediately downstream of the Caenorhabditis elegans cpr-5 gene promoter. This promoter has been shown previously to direct protein expression to the gut of C. elegans. The construct was micro-injected into DR96 unc-76(e911) mutant C. elegans together with a rescue plasmid and transgenic worms identified by reversion back to wild-type phenotype. Two transgenic lines of C. elegans were established. The presence of the injected construct and of the Haemonchus pepsinogen transcript in transgenic worms was confirmed by PCR analysis. Correct splicing of intronic sequences was observed. Immunohistochemistry showed expression of the Haemonchus pepsinogen protein in the gut of transgenic C. elegans, with reactivity evident in the larval and adult stages. Expression of the Haemonchus pepsinogen in C. elegans affirms the role of C. elegans as a model for parasitic nematodes and demonstrates its potential as a vector for expression of candidate vaccine antigens from parasitic nematodes.

Animals↗
PubMed1976

Changes in the hatch rate of Haemonchus contortus eggs between geographic regions.

Vulvar phenotypes and the rate of development of eggs over a range of temperatures were used to compare Haemonchus contortus populations in New York State and Ohio. These parameters indicated that the westernmost boundary of the subspecies Haemonchus contortus cayugensis is the Chautauqua valley in New York. The Haemonchus ecotype in Ohio had a vulvar phenotype formula similar to that described for the subspecies Haemonchus contortus contortus. The relationship between slope and intercept of the regression of rate of egg hatch on temperature was different for morphs within ecotypes as well as between the New York and Ohio ecotypes. Linguiform-A appeared to be the cold-adapted morph in both ecotypes. Smooth was the warm-adapted morph in New York with linguiform-B filling that niche in Ohio.

Animals↗
PubMed1999

Molecular cloning and characterization of gut-derived cysteine proteinases associated with a host protective extract from Haemonchus contortus.

Cysteine proteinases have been implicated in the protection conferred by vaccination with detergent-soluble extracts of Haemonchus contortus. In the present study, antisera from sheep refractory to Haemonchus challenge following vaccination with a 'proteinase-enriched' Haemonchus gut membrane extract, were employed to screen a cDNA expression library of the adult parasite. This resulted in the isolation of 3 cDNAs (designated hmcp1, 4 and 6) encoding cathepsin B-like cysteine proteinases. Immunocytochemical studies specifically localized the products of these genes to the microvillar surface of the parasite's gut and RT-PCR experiments revealed that these were developmentally regulated, being expressed exclusively during the blood-feeding parasitic stages. In addition, a generic PCR approach was adopted in order to identify the predominant cysteine proteinases in a UK strain of Haemonchus. A panel of 5 cDNAs, including hmcp1 and 4, was amplified in this way. Genomic Southern blot analysis indicated that some of these enzymes were encoded by single-copy genes, whereas others were encoded by multi-copy genes. Subsequent sequence analysis revealed that the proteases identified in this study were distinct from those previously reported in USA strains of the parasite.

Animals↗
PubMed2001

Cross-protection studies with gut membrane glycoprotein antigens from Haemonchus contortus and Teladorsagia circumcincta.

Gel profiles of the peanut and ConA lectin binding integral membrane glycoproteins of Teladorsagia circumcincta and Haemonchus contortus were compared and found to be considerably different. However, some of the Teladorsagia polypeptides were recognized by antisera specific for Haemonchus amino-, metallo- or aspartyl peptidases, enzymes which are known to be protective antigens for that parasite. As expected, an experimental vaccine containing these Haemonchus proteases was extremely effective against homologous challenge, reducing egg and worm counts by more than 99% and 92%, respectively, but it did not provide any useful cross-protection against either T. circumcincta, Trichostrongylus axei or Cooperiaoncophora. A reciprocal experiment, where sheep were immunized with the equivalent glycoproteins from T. circumcincta, showed that, while they were not protected against homologous challenge, there was some cross-protection against Haemonchus as measured by a significant reduction in worm egg output.

Animals↗
PubMed2004

Phylogeny for species of Haemonchus (Nematoda: Trichostrongyloidea): considerations of their evolutionary history and global biogeography among Camelidae and Pecora (Artiodactyla).

Phylogenetic analysis of 25 morphological characters among the 12 species of Haemonchus resulted in 1 most parsimonious tree (60 steps; consistency index = 0.67, retention index = 0.80). Monophyly for Haemonchus was diagnosed by 3 unequivocal synapomorphies, including the asymmetric origin of the dorsal ray, relative size of the ventral rays, and the presence of a barb on each spicule tip. Species of Haemonchus have complex histories with respect to host and geographic associations: (1) origins in Africa with basal diversification in antelopes (H. krugeri, H. lawrencei, H. dinniki, H. horaki), (2) independent events of colonization for those species in Caprini and Bovinae (H. contortus, H. placei, H. bedfordi, H. similis), (3) colonization and development of core host associations within Camelidae (H. longistipes) and among Antilopinae, Tragelaphini, and Giraffidae (H. mitchelli, H. okapiae, H. vegliai), and (4) geographically widespread species that are represented only by those that have been translocated with domestic stock. The North American fauna is characterized by 3 introduced and exotic species, H. placei, H. contortus, H. similis, which emphasizes the importance of continued documentation of faunal diversity in the context of predictive foundations derived from phylogenetic studies. Satellite associations for species of Haemonchus, particularly among Cervidae and Camelidae in the Neotropics and Cervidae, Antilocapridae, and possibly wild Caprinae in the Nearctic, have been a consequence of introductions and exchange of parasites at historical interfaces for managed and natural ecosystems. Such distributions are emblematic of the overriding significance of anthropogenic factors as determinants of the global distributions for pathogenic parasites in domestic and wild ruminants.

Animals↗