Haemonchus Placei Research Articles

Relação entre desempenho e infecções por nematódeos gastrintestinais em bovinos Nelore em crescimento

Este estudo teve por objetivo verificar a associação entre o desempenho e a carga parasitária de 28 machos inteiros da raça Nelore (a partir de um ano de idade), naturalmente infectados por nematódeos gastrintestinais. De novembro de 1999 a junho de 2000, os animais foram pesados quinzenalmente, período no qual foram colhidas amostras de fezes e de sangue para a realização, respectivamente, de exames coprológicos e sangüíneos. Os dados da contagem de ovos por grama de fezes (OPG) ajustaram-se ao modelo de distribuição binomial negativa, indicando que a distribuição de nematódeos no rebanho é agregada. Não ficou evidenciada associação entre ganho de peso e contagem de OPG, e entre contagem de OPG e volume globular (VG). De 10 coeficientes de correlação entre ganho de peso e VG, oito foram negativos, mas apenas dois significativos (P<0,05). As estimativas de repetibilidade da contagem de OPG, LOG (OPG+1) e VG foram de 0,26, 0,25 e 0,33, respectivamente. Cooperia punctata foi a espécie mais freqüentemente encontrada parasitando os animais. Além dessa espécie, foram detectados os seguintes nematódeos: Haemonchus placei, Haemonchus similis, Trichostrongylus axei, Bunostomum phlebotomum e Oesophagostomum radiatum. O parasitismo por nematódeos gastrintestinais aparentemente não prejudicou o desenvolvimento dos animais estudados.

Effect of dietary protein intake on calf resilience to Haemonchus placei infection

Vinte bezerros com 2 a 3 meses de idade criados livres de vermes foram divididos em 2 grupos com 10 animais cada alimentados com alta proteina (HP) e baixa proteina (LP) com 257 e 91 g kg-1 de proteina na materia seca respectivamente, devidamente balanceado em energia e minerais. Apos 4 semanas submetidos a estas duas dietas cada grupo original foi subdividido em 2 grupos, um contendo 4 animais nao infectado (C) e 6 animais infectados (I). O grupo infectado recebeu 5.000 larvas de Haemonchus placei duas vezes por semana por um periodo de 9 semamas, apos 4 semanas da ultima infeccao todos os animais foram sacrificados e realizada a contagem de vermes. Semanalmente foram feitas as pesagens dos animais, numero de ovos por grama de fezes e colheita de sangue para determinacao do hematocrito, hemoglobina, albumina e proteina total. A contagem de ovos por grama de fezes foi superior no grupo de HP em relacao ao grupo de LP, tendo em vista que o numero de vermes adultos no grupo HP (11.900 ± 7.660) foi maior que o grupo de LP (5.450 ± 7.895) . Apesar do numero superior de vermes encontrado no grupo HP, observou-se valores superiores de hematocrito e peso vivo quando comparado com o grupo de LP (p<0,05), demonstrado que a suplementacao proteica possibilita uma melhor resilience em bezerros infectados com Haemonchus placei.

Titration of subcutaneously administered eprinomectin against mature and immature nematodes in cattle.

Eprinomectin has been approved for use as a topically applied endectocide for beef and dairy cattle. To determine if eprinomectin has utility as an injectable anthelmintic, it was titrated at 0.05, 0.1, and 0.2 mg/kg s.c. against adult (Trial 1) and at 0.05, 0.1, 0.14, and 0.2 mg/kg s.c. against immature (Trial 2) stages of lung and gastrointestinal nematodes in cattle. In Trial 1, every dose of subcutaneously delivered eprinomectin showed maximal or near-maximal (> or = 99%) efficacy against Haemonchus placei, Ostertagia ostertagi, Trichostrongylus axei, T colubriformis, Cooperia punctata, Nematodirus helvetianus, Oesophagostomum radiatum, and Dictyocaulus viviparus. Adult C. oncophora was the only exception. However, even against this species, the lowest dose of 0.05 mg/kg showed 93% efficacy, and the efficacious dose necessary to kill 95% (ED95) of adults was 0.056 mg/kg. In Trial 2, every dose of subcutaneously delivered eprinomectin showed maximal or near-maximal (> or = 99%) efficacy against the immature stages of all of the above species of endoparasites. As a result, ED95 values could not be calculated. Consequently, the exquisite potency against endoparasites through parenteral administration suggests that eprinomectin may also have potential utility as an injectable product for cattle.

Freqüência e intensidade parasitária de helmintos gastrintestinais em bovinos abatidos em frigorífico da região noroeste do Estado de São Paulo, SP, Brasil

Parasitary gastrointestinal helminths frequency and intensity were studied in 48 female bovines, with different zebu and taurine crossbreeding degrees, ages ranging between 24 and 30 months, from eight counties in the Northwest of São Paulo State, slaughtered at Frigorífico Montenegro, Araçatuba, São Paulo (Brazil) and four animals were monthly necropsied over one year. The identified gastrointestinal helminth species were: Cooperia punctata, Cooperia pectinata, Haemonchus similis, Haemonchus placei and Oesophagostomum radiatum. Among the 48 animals, 21 (43,8%) were carrying Haemonchus spp. The Haemonchus similis and the Haemonchus placei species were identified isolated at an equivalent rate (10,4%), being simultaneous infection registered in 22,9% of the cases. In small intestine, 26 bovines (54,2%) showed Cooperia punctata. Ten male Cooperia pectinata were identified in only one bovine that also carried 310 Cooperia punctata. In the large intestine, 20 bovines (41,7%) showed Oesophagostomum radiatum. Mixed infections occurred in 52,1% of the animals, simple infections in 12%, and 22,9% of the bovines did not have gastrointestinal helminths.

A multiplex PCR assay for differentiating economically important gastrointestinal nematodes of cattle

A multiplex polymerase chain reaction (PCR) test was developed for identifying gastrointestinal (GI) nematodes that commonly infect cattle. This assay was developed using adult-derived genomic DNA and shown capable of discriminating parasite eggs from the feces of experimentally-infected animals at both the species and genus levels. Sequence data from internal (ITS) and external (ETS) transcribed spacers of the ribosomal DNA (rDNA) repeats as well as the 3′-end of the small subunit rDNA and 5′-end of the large subunit rDNA were used to generate five primer sets which, when used simultaneously in a multiplex PCR, produce a unique electrophoretic DNA banding pattern characterized by a single DNA fragment for Ostertagia ostertagi (257 bp), Haemonchus placei (176 bp), Oesophagostomum radiatum (329 bp), Trichostrongylus colubriformis (243 bp) and Cooperia oncophora (151 bp). In a similar manner, the constructed primer sets amplified DNA from Ostertagia lyrata, Haemonchus contortus, Trichostrongylus axei, Cooperia surnabada and Cooperia punctata. With respect to H. contortus, a closely migrating doublet was generated suggesting size heterogeneity in the ETS which is consistent with multiple rDNA repeat units within this species. PCR analyses using mixtures of monospecifically-purified nematode eggs indicated a sensitivity of less than 0.5 egg-DNA equivalent per species. Although, not designed as a quantitative technique, relative PCR signal intensities corresponded to relative egg burdens within the DNA samples from mixed species of eggs.

The epidemiology of gastrointestinal nematodes of dairy cattle in central Kenya.

The epidemiology of H. placei and of other gastrointestinal nematodes in yearling dairy cattle was examined on two farms in Kiambu District, central Kenya during each of 13 one-month periods from April 1993 to April 1994. On each farm, 32 newly weaned dairy calves were given a single dose of albendazole and then placed on experimental pastures. Twelve of the animals were designated for bimonthly slaughter (n = 2) and analysis of worm population characteristics and 20 were designated for blood and faecal collection and for weighing. Two parasite-free tracer calves were grazed alongside the weaner calves each month throughout the study period and were also slaughtered for analysis of worm populations. Faecal egg counts, haematological and serum pepsinogen determinations, herbage larval counts, and animal live weight changes were recorded monthly. The study revealed that Haemonchus placei, Trichostrongylus axei, Cooperia spp. and Oesophagostomum radiatum were responsible for parasitic gastroenteritis and that H. placei was the predominant nematode present in the young cattle on both farms. Faecal egg counts from resident cattle and necropsy worm counts revealed that pasture larval levels were directly related to the amount of rainfall. The total worm burdens in the animals were highest during the rainy season (March-June and October-December) and lowest during the dry seasons (July-September and January-February). The very low recovery of immature larvae of H. placei from the tracer calves indicated that arrested development is not a feature of the life cycle of this parasite in central Kenya. The maintenance of the parasite population depended on continuous cycling of infection between the host and the pasture. The agroclimatic conditions of the study area were such that, in general, favourable weather conditions for the development and survival of the free-living stages of gastrointestinal nematodes existed all year round.

Experimental cross-infections of Haemonchus placei (Place, 1893) in sheep and cattle

To examine effects on biology and morphology, Haemonchus placei infections were propagated in cattle or sheep and infective larvae were introduced into the same or opposite host. Ovine source larvae had a geometric mean (GM) prepatent period of 26.5 days regardless of host species, compared to 30.6 days for bovine source larvae regardless of host species. Similarly, ovine source H. placei had a higher GM percentage establishment versus bovine source larvae (9.6% versus 3.4%) regardless of host species. The patent daily egg count for ovine source versus bovine source H. placei was 109.1 versus 50.0 FEC regardless of host species. Mean spicule length for ovine source H. placei was 492.5 μm while bovine source measured 496.5 μm. Mean female tail length for ovine source H. placei was 586.5 and 589.5 μm for bovine source H. placei. Using synlophe morphology, all worms that were measured were identified as H. placei. Sixty-three percent of females examined for vulvar flap morphology had knob-like vulvar flaps while the remaining 37% had linguiform vulvar flaps.

In vitro activity of Brazilian strains of the predatory fungi Arthrobotrys spp. on free-living nematodes and infective larvae of Haemonchus placei.

In vitro tests were carried out to assess the activity of 26 Brazilian isolates of predatory fungi of the genus Arthrobotrys on a free-living nematode (Panagrellus sp.) and on infective larvae of Haemonchus placei, a parasitic gastrointestinal nematode of cattle. The results showed that the free-living nematode Panagrellus sp. was the most preyed upon, compared to H. placei, for all the fungal treatments. Also, variable predatory capacity was observed for different fungal isolates belonging to the same genus when applied to different nematode species.

Persistent efficacy of topical eprinomectin against nematode parasites in cattle.

Six studies were conducted to evaluate the persistent efficacy of eprinomectin pour-on against experimental challenges with infective nematode larvae in calves. In each study, calves were randomly assigned to one untreated group and up to four test groups, which were treated with eprinomectin at 500 microg/kg body weight at weekly intervals before single bolus challenge. The calves were necropsied approximately 4 weeks after challenge infection for nematode recovery. Eprinomectin pour-on provided > or =90% efficacy against challenge with Haemonchus placei, Trichostrongylus axei and T. colubriformis at 21 days after treatment and against Cooperia oncophora, C. punctata, C. surnabada, Dictyocaulus viviparus, Nematodirus helvetianus, Oesophagostomum radiatum and Ostertagia ostertagi at 28 days after treatment.

Ostertagia ostertagi challenge of calves vaccinated with Haemonchus placei intestinal homogenate

The protective capacity of vaccination with Haemonchus placei whole gut homogenate against challenge with the non-blood-feeding nematode Ostertagia ostertagi was evaluated in calves. Ten helminth-free calves were randomly assigned to two groups. Group 1 received 100 μg H. placei intestinal homogenate in the adjuvant 5% dextran sulfate/PBS, while Group 2 received the adjuvant alone. Injections were administered subcutaneously on Days 0 and 28. All calves were challenged with ∼26,100 O. ostertagi larvae on Day 42. Serum antibody response and counts of nematode eggs per gram of feces (EPG) were determined throughout the study. Calves were necropsied at 5.5 weeks post-challenge for recovery of nematodes. Although significant increases were detected in both serum IgG 1 and IgG 2 of Group 1 calves ( p<0.05), there was no significant difference in the total number of O. ostertagi recovered from the two groups ( p>0.05). Lengths of adult nematodes were not significantly different between groups nor were the numbers of eggs present in adult females recovered from each group significantly different ( p>0.05). There were also no significant differences between groups regarding fecal egg counts ( p>0.05). Results suggest either: (1) the antigens targeted by the induced antibodies were not present in O. ostertagi; (2) the antigens targeted by the induced antibodies were present, but not essential to O. ostertagi survival; or (3) the antigen was present and essential, but amount of antibody ingested was insufficient to cause damage to the nematode.

Vaccination of calves with Haemonchus placei intestinal homogenate

The ability of adult Haemonchus placei intestinal homogenate to confer protection against homologous challenge infection was evaluated. Calves were immunized twice with 100 μg H. placei intestinal protein in 5% dextran-sulfate/PBS (vaccinates) or PBS alone (controls) and were challenged with approximately 3300 infective H. placei larvae. There was no significant difference between groups in the total number of nematodes recovered but significantly fewer ( p < 0.001) adult females were recovered from vaccinates. The proportion of fourth-stage larvae in vaccinates was significantly greater ( p ≤ 0.05) than in controls. Lengths of adult male and female nematodes were significantly shorter ( p < 0.001) in vaccinated calves, and the numbers of eggs present in the uteri of female nematodes from vaccinates were significantly decreased ( p < 0.001). Counts of nematode eggs per gram of feces (EPG) of vaccinates were significantly less than that for controls on Days 29–49 post-challenge ( p ≤ 0.05). Vaccinates had significant increases in serum IgG 1 and IgG 2 log(10) titers ( p ≤ 0.05) but not in serum IgM. EPG, numbers of females, and size of males and females were negatively correlated with increased mean post-challenge IgG 1 and IgG 2 titers. Reduction in binding of periodate-treated gut homogenate by immune serum indicated a carbohydrate specific component in the immune response.

Description of Haemonchus placei (Place, 1893) (Nematoda, Trichostrongylidae, Haemonchinae), identification and intra-specific morphologic variability.

Haemonchus placei in cattle has never been completely described, possibly due to great morphological similarity with small ruminants Haemonchus contortus. It is newly described on one isolate from Argentina. It has clear distinct morphological features from sheep and goats Haemonchus contortus and presents only two female morphotypes (linguiform and knobbed) instead of three recorded in H. contortus. A key is proposed to identify females. Female as well as male Haemonchus placei from New World (Argentina, Mexico, USA) are morphologically different from those of Old World (Africa: Burkina-Faso, Mauritania and Ivory Coast) or Australia, possibly due to local evolution since their introduction several centuries ago from Africa or India. We propose to differentiate three sub-species, H. placei placei in Australia, H. placei africanus in western Africa and H. placei argentinensis in the New World.

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.

Persistent activity of doramectin injectable formulation against experimental challenge with Haemonchus placei in cattle

Two studies were conducted in North America to evaluate the persistent activity of doramectin injectable formulation against experimental challenge with Haemonchus placei. In both studies, calves were randomly assigned to 1 of 4 treatment groups ( n = 10 per group) or a larval viability group ( n = 2). Calves were treated subcutaneously in the lateral midline of the neck with saline (1 ml/50 kg) on Day 0, or with doramectin (200 mg/kg = 1 ml/50 kg) on Day 0, 7, or 14. Animals used to assess larval viability did not receive any treatment. Beginning on Day 14 and continuing through Day 28, each of the 40 treated calves were given approximately 300 infective larvae of H. placei per os. The two larval viability animals received approximately 10,000 larvae as a single dose on Day 28. Approximately two weeks later, all animals were slaughtered and the abomasum from each calf processed for nematode recovery. A 2% aliquot of abomasal contents plus wash was examined for enumeration and identification of nematodes. Geometric mean H. placei counts were calculated from the log ( H. placei count + 1) and used to estimate percentage reduction. Overall, doramectin was ≥96.9% efficacious in reducing infection with H. placei when challenged daily 14–28 days after treatment.

Comparisons of Two Polymorphic Species of Ostertagia and Phylogenetic Relationships within the Ostertagiinae (Nematoda: Trichostrongyloidea) Inferred from Ribosomal DNA Repeat and Mitochondrial DNA Sequences

The first internal transcribed spacer DNA (ITS-1) (rDNA) and the mitochondrial (mt) DNA-derived cytochrome oxidase I gene (COX-1) were enzymatically amplified, cloned and sequenced from 6 nominal species of Ostertagiinae as well as Haemonchus contortus and Haemonchus placei. The portion of the COX-1 gene analyzed was 393 base pairs (bp) in length and contained 33 within species polymorphic base changes at 28 synonymous sites. The ITS-1 rDNA consensus sequences ranged from 392 bp (Ostertagia ostertagi/Ostertagia lyrata, Teladorsagia circumcincta) to 404 bp (H. contortus, H. placei). These data were used both in a distance analysis to assess the concept of polymorphic species within the genus Ostertagia and in parsimony analysis to assess phylogenetic relationships within a limited group of Ostertagiinae. Pairwise similarity scores of both ITS-1 and COX-1 data showed the highest number of conserved sites between the proposed dimorphic species of Ostertagia. The level of similarity was lower in the COX-1 data due to the high number of synonymous base changes. Analysis by maximum parsimony of the same data did not refute O. ostertagi/O. lyrata and Ostertagia mossil/Ostertagia dikmansi as dimorphic species and supported monophyly of these ostertagiines relative to representatives of the haemonchine outgroup. In the single most parsimonious tree from ITS-1 rDNA data, a subclade of Ostertagia spp. included forms possessing parallel synlophes and long esophageal valves that typically occur in cervid hosts.

Demonstration of Shared Carbohydrate Epitopes in Intestinal Proteins of Some Bovine Gastrointestinal Nematodes

The presence of shared carbohydrate intestinal epitopes in bovine gastrointestinal nematodes was demonstrated. Proteins were extracted from the intestinal tissue of a laboratory strain of adult Haemonchus placei and used to produce monoclonal antibodies (mAb). Analysis of this detergent extract by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed 7-9 bands ranging from approximately 39 to 298 kDa. The mAbs reacted with periodate-sensitive epitopes and, in western blots, recognized high molecular weight protein bands (approximately 111-298 kDa). Immunohistochemical studies with the mAbs verified the intestinal location of the epitope(s) in the laboratory strain as well as in a recent field isolate of H. placei. Epitope(s) were conserved among species examined within the Trichostrongyloidea (Ostertagia ostertagi, Cooperia punctata, Haemonchus placei, and Haemonchus contortus), semiconserved among species within the Strongyloidea (present in Oesophagostomum radiatum, absent in Oesophagostomum venulosum), and absent in the only species examined in the Ancylostomatoidea (Bunostomum phlebotomum).

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.

An abattoir survey of gastrointestinal nematode infections in cattle in the central highlands of Kenya.

The gastrointestinal tracts of 672 crossbred cattle were obtained from various abattoirs in Kiambu District, Kenya from August 1992 to July 1993, and examined for the presence of gastrointestinal nematodes. Eight nematode species were found in 583 (86.8%) of the animals. The nematodes were, in order of prevalence: Haemonchus placei (67.0%), Cooperia pectinata (53.0%), Cooperia punctata (41.7%), Oesophagostomum radiatum (38.4%), Trichostronglyus axei (24.3%), Nematodirus helvetianus (19.6%), Trichuris globulosa (9.7%) and Strongyloides papillosus (3.6%). The intensity of the nematode infection was moderate; the mean burden being less than 7000 worms. H. placei accounted, on average, for 52.3% of the total burden. The total burden was least during the dry seasons and increased gradually during the rainy seasons. Adult H. placei persisted in the host throughout the year and there was no indication of hypobiosis. The heaviest gastrointestinal worm burdens were detected in 1.5- to 3-year-old animals. These findings are discussed with regard to their relevance for strategic control of gastrointestinal nematodes in cattle.

Epidemiology of Mecistocirrus digitatus and other gastrointestinal nematode infections in cattle in Mindanao, Philippines

Over a period of 14 months, faecal and serum samples were collected monthly from cattle of 1 to 30 months old on three ranches (20–25 animals ranch−1 sample−1) in Mindanao, Philippines. Individual faecal egg counts, serum pepsinogen levels and Mecistocirrus digitatus specific antibodies were determined, and infective larvae from pooled faecal samples were examined. Post mortem worm counts were carried out on tracer calves (n = 16) that had been kept for 30 days with the herds on two of the ranches. A number of gastrointestinal nematode species were present: M. digitatus, Haemonchus placei, H. similis, Trichostrongylus axei, Cooperia punctata, C. pectinata, Bunostomum phlebotomum and Oesophagostomum radiatum. Strongyle eggs first appeared in the faeces of calves of two months old, egg counts peaked when animals were 3–6 months old, after which they steadily and significantly declined. Faecal egg output of M. digitatus increased up to the age of 10 months, after which there was a steady but not significant decline until the age of 24 months. In faecal cultures the relative proportion of Cooperia larvae decreased from over 70% in 0–6 month old animals to 30% in 19–24 month old animals, and a corresponding 30% increase in the proportion of Mecistocirrus was observed. Both serum pepsinogen and M. digitatus specific antibodies levels increased during the first year of life, and then remained at the same level in older animals. Whereas the total faecal egg output did not significantly vary throughout the year, worm counts from tracer calves indicated a marked seasonality in transmission.

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.