Dynamics of infestation of cattle and pasture by gastrointestinal nematodes in an Atlantic temperate environment

The objective of the present study was to determine the dynamics of infestation of cattle and pasture by gastrointestinal nematodes in a mild humid environment in northwestern Spain. For this, infestation of pasture by free-living stages (L3), dynamics of faecal egg output, blood pepsinogen levels and worm burden in slaughtered animals were quantified. The results showed a high degree of annual variability, which was dependent on weather conditions. The seasons were clearly defined in the study area, with mild humid winters and relatively dry summers registered throughout the years of the study. Infestation of pasture by larvae varied from year to year, peaking during August in the first year, between August and December in the second year, and during October in the third year. The annual variation was mainly due to weather conditions, particularly the amount of rain in summer. The patterns of faecal egg output were similar in the first and third grazing seasons, with maximum levels observed in May/June; however, in the second year, the peak was reached in October. Blood pepsinogen levels increased from pasture turnout (March/April) until the end of the grazing season (November/December), reaching maximum values from August/September onwards. The nematode parasite species identified at necropsy were Ostertagia osteragi, O. lyrata, Cooperia oncophora, C. macmasteri, C. punctata and Trichuris ovis, with O. ostertagi and C. oncophora predominating. In faecal cultures, the following genera were also identified: Haemonchus, Trichostrongylus, Nematodirus, Bunostomum, Oesophagostomum and Strongyloides. There was a significant correlation (r=0.97, P<0.01) between worm burden (Ostertagia spp.) and pasture infestation (Ostertagia L3) 3 weeks prior to slaughter of the calves, and also between blood pepsinogen levels and pasture infestation by Ostertagia L3 (r=0.33, P<0.02). Correlations between worm burden and faecal egg output and between blood pepsinogen level and faecal egg output were not significant. The results obtained in the present study confirm that there is annual variability in the time-course of nematodosis in cattle, and demonstrate the importance of weather, particularly summer rainfall, in an Atlantic temperate environment.     

Genetic control of immunity to gastrointestinal nematodes of cattle

Previous studies have indicated that host genetics significantly affects the number of gastrointestinal nematode eggs per gram (epg) in the feces of calves during their first grazing season. An entire calf crop of approximately 190 animals was monitored monthly until weaning to verify these earlier results, and to begin to discern the basis for this phenomenon. A significant genetic effect on fecal epg values was not observed until calves had been on pasture for 2-3 months, and was demonstrable until late in the grazing season when the effect was lost. The loss of a genetic effect coincided with the appearance of significant numbers of the more highly fecund nematode species Haemonchus placei and Oesophagostomum radiatum, and with an apparent increase in Ostertagia ostertagi transmission, indicating that the observed genetic control of epg values may be species specific, dose dependent or both. Calves were selected from the population, and grouped according to their epg phenotype over the grazing season as either high or low epg calves. Postmortem examination of some of these calves indicated that worm burdens in the low epg calves were 60% of those of the high epg calves. Experimental challenge inoculation of the remaining calves indicated that: (1) challenge with Cooperia oncophora resulted in low epg calves harboring worm numbers that were 65% of those of high epg calves; (2) challenge with O. ostertagi resulted in similar numbers of worms in both groups, but the fecundity of worms in the low epg groups was significantly lower (P less than 0.05) than in the high epg group. Analysis of serum anti-Ostertagia antibody levels in the grazing calf population showed rises in serum IgG1, IgG2, IgM and IgA antibody levels during the grazing season. Peak serum IgG2 and IgG1 anti-Ostertagia antibody levels were found to be significantly affected by host genetic factors while IgA and IgM levels were not under such control.     

Relationship of pasture rotation to acquisition of gastrointestinal nematodes by sheep.

In a study of the relationship between pasture rotation in Illinois and acquisition of nematodes (mostly Haemonchus contortus) and body weight gains by lambs grazing with their ewes, 2 pasture rotation systems were tested. (1) Lambs and ewes were rotated through a series of 12 alfalfa-bromegrass-lespedeza pastures, each pasture being grazed for 3 to 4 days and rested for 5.5 weeks; 4 complete rotations were done during a 168-day grazing season. (2) Lambs and ewes were moved every 2 days, and 3 complete rotations of 50, 42, and 54 days, respectively, were done during the 146-day grazing season. The lambs under rotation had more nematodes and gained less weight than nonrotated control lambs, although rotation increased the amount of pasturage. Rotation is not recommended to control nematode parasitism of sheep in Illinois.     

Effectiveness of grazing management in controlling gastrointestinal nematodes in weaner lambs on pasture in Denmark.

A dose and move to clean pasture strategy for nematode control in weaner sheep was compared to a move only strategy. Sixteen ewes with twin lambs (2-3 weeks old) were turned out on infected pasture on 4 May 1999. On 1 July, the lambs were allocated to four groups of eight and weaned on to clean pasture. Two groups (DM1+2) were treated with anthelmintics, while the other two (M1+2) were not treated. Each group was allocated to a separate paddock and set stocked until 27 September when all the animals were slaughtered to perform worm counts.Moving the weaned lambs to clean pasture reduced the faecal egg counts to less than one third within 4 weeks while the treatment reduced it to zero for 4 weeks. Faecal egg counts of the dose and move groups remained significantly lower for 6 weeks (P<0.0001) after moving to the clean pasture. After this period the differences were not significant as the dose and move groups started shedding eggs in faeces. The pasture infectivity was lower in the paddocks grazed by groups (DM1+2). The weight gains and the serum albumin levels were comparable in all four groups. O. circumcinta and Trichostrongylus vitrinus were the major species recovered. The total worm counts were significantly lower in (DM1+2) compared to M1+2, particularly the mean counts in the small intestines (T. vitrinus) (P<0.01). It was concluded that weaning lambs at the beginning of July and moving them before the expected mid-summer rise in herbage infection to a clean pasture will prevent parasitic gastroenteritis and achieve good production whether the move is accompanied by anthelmintic treatment or not. The effects will be subject to prevailing nematode species, local climatic conditions and length of the grazing season.     

Development and survival of infective larvae of gastrointestinal nematodes of cattle on pasture in central Kenya

On a series of pasture plots, 2 kg pats of bovine faeces containing known numbers of strongylid (Haemonchus, Cooperia, Oesophagostomum and Trichostrongylus) eggs were deposited at intervals of 4 weeks from July 1995 to June 1996. The plots were sampled every 2 weeks after contamination and infective larvae were identified and counted. Larvae of all the genera developed throughout the year, but the pats exposed during the rainy season yielded more abundant larvae on the herbage. Irrespective of the season of deposition of the pats, larvae were found in larger numbers from 2 to 6 weeks after deposition and generally declined to below detectable levels within 12 to 16 weeks of contamination. The comparatively short survival times noted in this experiment may present opportunities for manipulation of the population dynamics of the gastrointestinal nematodes in the tropical environment of Kenya.     

Efficacy of moxidectin against gastrointestinal nematodes of cattle.

Three groups of 11 naturally infected crossbred beef calves were injected subcutaneously with moxidectin 1 per cent injectable at 0.2 or 0.3 mg moxidectin/kg bodyweight or with the unmedicated vehicle. Nematode infections had been acquired during grazing from December to April. Based on the faecal egg counts and total worm counts of the control calves at necropsy (11 to 13 days after treatment) most of the calves had heavy parasitic burdens. Ostertagia ostertagi was predominant and the mean numbers of adults, developing fourth stage larvae (L4) and inhibited early L4 were 45,906, 10,061 and 68,918, respectively. Haemonchus placei and Trichostrongylus axei were also present in the abomasa. Three species of Cooperia, Oesophagostomum radiatum L4 and T colubriformis adults were found in the intestinal tract. Both dosages of moxidectin were equally effective (P < 0.05) against all the abomasal nematodes (99.9 to 100 per cent) and the intestinal tract nematodes (99.4 to 100 per cent). No adverse reactions to the moxidectin treatment were observed. Abomasal pathology characteristic of heavy O ostertagi infection was observed in the control calves, but not in the treated calves.     

Seasonal changes in pasture populations of infective larvae of gastrointestinal nematodes of cattle in eastern Nigeria

The seasonal changes in the populations of trichostrongylid infective larvae (L3) on herbage and in soil samples collected from pastures grazed by beef cattle were studied at Nsukka, eastern Nigeria, from April 1980 to July 1981. Large numbers of L3 were recovered from all samples collected during the rainy season (April to October). The rainy season herbage infestation was characterised by three clearly defined peaks. The first, which followed an 'early rains' (April) rise, occurred in the second half of May while the larger second and third peaks occurred in late July and October respectively. It is suggested that each of these peaks represented a distinct wave of infestation by a separate generation consisting of the three trichostrongylids concerned, namely Cooperia, Haemonchus and Trichostrongylus species. Although there was a sharp fall in pasture infestation following the onset of the dry season, appreciable numbers of L3 were still present on herbage in early December. The implications of these findings have been discussed in relation to the choice of effective strategic anthelmintic programmes for the prophylaxis and control of bovine parasitic gastroenteritis in the Nsukka area.     

Effect of strategic anthelmintic treatment and pasture management on productivity and control of nematode parasites in weaner-yearling beef cattle

Three groups of 17 beef calves were used to evaluate effects of strategic anthelmintic treatment on safe (group 1) and contaminated (group 2) pasture in comparison with minimal treatment at weaning and contaminated pasture (group 3). The investigation extended from weaning in November 1982 to the following August. Results of faecal egg counts, herbage larval counts, plasma pepsinogen and tracer calf worm counts in autumn and spring indicated minimal levels of infection on safe pastures provided in November and April (group 1). A decided weight gain advantage for group 1 was achieved from November to April, but the rate of gain was not consistent after April and transfer to the second safe pasture. Final average weights in late August were: group 1, 368 kg; group 2, 336 kg; group 3, 262 kg. All were significantly different (P less than 0.05). Worm counts from representative yearlings in September revealed low to moderate levels of Ostertagia ostertagi in group 1. In contrast group 2 cattle had large, almost exclusively O ostertagi infections; group 3 cattle had exceedingly high levels of Trichostrongylus axei infection and moderate to high levels of O ostertagi. Marginal evidence of type 2 ostertagiasis was observed in individual animals of group 2 and group 3.     

Cow-calf herds in eastern Germany: status quo of some parasite species and a comparison of chemoprophylaxis and pasture management in the control of gastrointestinal nematodes.

Infections with gastrointestinal parasites (Eimeria spp., Cryptosporidium spp., Buxtonella sulcata, Fasciola hepatica, Moniezia spp. and trichostrongyles) and lungworms were monitored in five cow-calf herds in the north German lowlands. Estimated prevalences of infections with Eimeria spp. (predominantly Eimeria bovis) ranged between approximately 2 and 48%. The highest prevalences were found during late summer and autumn. On one farm Cryptosporidium spp. were detected in July and August (prevalence: 8.5 +/- 2.7% and 6.7 < 2.0%). The latter finding coincided with diarrhoea in many calves. Buxtonella sulcata was found during the entire study period in highly variable estimated prevalences ranging between zero and 73%, but without any obvious association with clinical disease. Fasciola hepatica was detected on four out of five farms at estimated prevalences of approximately 1-20%. Lungworm infections played a minor role in at least three of five study herds. The estimated prevalence of trichostrongyle infections rose from August until November whereas the intensity of infection did not change significantly. No difference in the intensity of infection could be detected between one farm on which infections with gastrointestinal nematodes were controlled only by moving the animals to an uninfected pasture in July, and three other herds on which strategic anthelmintic control was in place.     

Use of a mixed sericea lespedeza and grass pasture system for control of gastrointestinal nematodes in lambs and kids

Because of a high prevalence of anthelmintic resistance and consumer demand for chemical free meat products, management tools to minimize the need for deworming are needed. The objective was to examine the effectiveness of grazing sericea lespedeza (SL) in a mixed grass or a pure forage system for control of gastrointestinal nematodes (GIN); in other words pasture systems included grass, grass plus SL, or SL alone (Experiments 2 and 3). Selective use of copper oxide wire particles (COWP) based on the FAMACHA(?) system was used to aid in GIN control. In Experiment 1, lambs co-grazed bermudagrass (BG; n=21) or SL in a mixed grass pasture (SLM; n=22) with dams for 14 days. In Experiment 2, lambs grazed BG (n=14), SLM (n=13), or pure SL (SLP; n=13) pastures for 56 days. In Experiment 3, doe kids grazed BG (n=12), SLM (n=13), or SLP (n=13) for 84 days. Animals were fed a 16% crude protein supplement based on NRC requirements and estimated forage quality of pastures, so that 454, 389, and 200 g/lamb (Experiment 2), or 454, 300, and 150 g of supplement/goat (Experiment 3) was fed to BG, SLM, and SLP, respectively. Animals were dewormed with COWP if FAMACHA(?) was >3. Coprocultures were conducted to identify GIN genus. In Experiment 1, FEC were reduced in lambs grazing SLM compared with BG pastures. In Experiment 2, FEC were reduced in SLP compared with BG lambs on all days, and reduced in SLM compared with BG lambs on day 56. Initially, Haemonchus contortus was the predominant nematode, but the population shifted to other species in the SL groups by the end of the study. The mean number of dewormings/lamb was 0.71, 0.20, and 0.21±0.13 for BG, SLM, and SLP groups, respectively. In goats in Experiment 3, Trichostrongylus spp. was the predominant nematode in May and June and H. contortus in July. There was little meaningful effect of forage treatments on GIN infection in kids. Because H. contortus was not the predominant nematode in kids, the integrated approaches used may not have been effective in controlling GIN. Grazing SL was effective for GIN control in lambs in early summer, but the effect was delayed in lambs grazing a mixed SL/grass pasture unless lambs initially grazed with dams. An integrated approach used that included SL grazing and COWP for deworming was effective in lambs.     

Control of gastrointestinal nematodes in dairy heifers by two strategic treatments with ivermectin

Dairy replacement heifers given two strategic treatments with ivermectin (0.2 mg/kg) three and eight weeks after turnout to spring pastures in northern USA had mean adjusted weight gains (62.3 kg) that were 62 per cent (P less than 0.02) greater than those of control heifers (38.5 kg) at the time of winter housing. Pasture infectivity was consistently higher in control pastures and there was a sixfold difference between treatment (56 L3/kg) and control (358 L3/kg) pastures by the time of winter housing on October 18. This study confirmed earlier studies in northern USA demonstrating the value of two strategic treatments in achieving significant increases in weight gains and hastening the time of first breeding by one to three months at a saving of $40 to $140 per heifer. It was concluded that this dosing strategy is a satisfactory method of parasite control for dairy replacement heifers in northern USA without undue selection for drug resistance.     

Occurrence and seasonal behavior of gastrointestinal nematodes infecting Maine dairy cattle.

Gastrointestinal tracts of 48 yearling Maine dairy cattle were examined (8 animals every 2 months) for 1 year. Adult and immature nematodes were identified and counted. Species recovered were Bunostomum phlebotomum, Cooperia mcmasteri, Cooperia oncophora, Cooperia pectinata, Cooperia punctata, Haemonchus placei, Nematodirus helvetianus, Oesophagostomum radiatum, Ostertagia circumcincta, Ostertagia lyrata, Ostertagia ostertagi, Trichostongylus axei, and Trichuris ovis. Strongyle parasitism was observed during every sampling period and the overall incidence was 93.7%. The most commonly encountered genera were Ostertagia spp (85.4%) and Cooperia spp (81.2%). Seasonal fluctuations in the worm burden of various nematodes were observed, with largest numbers seen in the fall. The incidence and degree of parasitism appeared to be related to environmental conditions. Proportions of adult and immature worms were shown to fluctuate with the time of year. Greatest numbers of immature worms were observed during the fall and winter.     

An assessment of residual ovine nematodes on pasture under maritime conditions.

Residual ovine nematode pasture infections were assessed by grazing groups of ewes and their lambs on permanent sheep and cattle pastures and by the use of tracer lambs. Ostertagia spp., Cooperia oncophora, Nematodirus spp., Chabertia ovina and Trichuris spp. eggs and/or larvae survived on pastures overwinter. Second generation Ostertagia larvae were present in greatest numbers on pasture during the latter part of August and early September. The failure of a significant build-up of Cooperia oncophora was attributed to negligible worm egg output of this species in sheep. A build-up of Nematodirus spp. on pasture was not detected in this study.     

Effects of ivermectin on control of gastrointestinal nematodes and weight gain in weaner-yearling beef cattle

Four groups of 16 crossbred beef calves were used in evaluating different anthelmintic treatment schedules: group 1 was given ivermectin (IVM) at weaning only (October 31) and grazed on initially safe pasture; group 2 was given IVM at weaning, on January 28, and on April 22, and grazed on contaminated pasture; and group 3 was given IVM at weaning and on April 22, and grazed on contaminated pasture; and group-4 was group treated with fenbendazole (FBZ) at weaning only, with provision for individual salvage treatment, and grazed on contaminated pasture. The investigation was from Oct 31, 1984, to Oct 9, 1985. Initially high fecal egg counts at weaning were more effectively reduced by IVM than by FBZ, and the effect of safe pasture was evident in minimal worm burdens in tracer calves grazed with group-1 cattle during November and least amount of weight loss in group-1 yearlings during winter. Fecal egg counts, pasture larval counts, and plasma pepsinogen concentrations remained low in group 2 after the January treatment. Fecal egg counts of the other groups increased substantially during late winter and spring, but pasture larval counts increased only on group-1 and group-4 pastures. During spring, highest worm burdens were found in group-1 and group-4 tracer calves (grazed in April) and in group-3 and group-4 yearlings (slaughtered in early April). Six cattle of group 4 were salvage treated with FBZ in February and April. Greatest gains were observed from March through June, with group-2 and group-1 cattle gaining the most.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of first season chemoprophylaxis in calves on second season pasture contamination and acquired resistance and resilience to gastrointestinal nematodes

Two groups of second grazing season cattle, which had been treated with an ivermectin-sustained-release bolus (ISRB) in their first grazing season, were monitored during consecutive years (1995 and 1996) on the same second grazing season pasture. In the preceding year (1994), this pasture had been grazed by yearlings that had not received chemoprophylaxis in their first grazing season. The objectives of the study were, firstly, to investigate whether the chemoprophylactic-treated yearlings were less resistant to gastrointestinal nematodes upon subsequent exposure, and hence excreted more strongyle eggs compared to the control yearlings; secondly, whether an increased susceptibility of the previously treated animals resulted in a yearly increase of the pasture infestation on the second grazing season pasture; and finally, whether this affected the second year weight gain of the animals. In 1996, the yearlings that had been chemoprophylactic-treated in 1995 excreted higher numbers of nematode eggs, compared to the previously ‘untreated' yearlings. In addition, the proportion of Cooperia larvae was markedly higher in the faecal cultures from the chemoprophylactic treated-animals, suggesting a negative effect of preventive treatment with an ISRB on the acquired resistance of the animals. However, there was no evidence that the slightly higher egg output in the previously treated yearlings had an effect on the larval contamination of the second grazing season pasture. A significant yearly decrease in the second season average daily weight gains was observed, but it could not be inferred from the results of the parasitological parameters that the differences in second year growth were caused by different levels of resilience between chemoprophylactic-treated and -untreated animals. As the study covered three consecutive second grazing seasons, an effect of differences between years (e.g. in weather conditions or grass growth) on the results cannot be excluded.     

The epizootiology of gastrointestinal nematodes of cattle in selected areas of Oregon.

A study was initiated to (1) determine species of gastrointestinal nematodes present in cattle in selected areas of Oregon, (2) examine seasonal abundance of these nematodes as an indicator of periods of transmission, and (3) determine when developmental inhibition occurs in the major genera of nematodes encountered. Four study sites were chosen: Corvallis, Langlois, near Fort Rock, and southeast of Klamath Falls on the Oregon-California border. Eight sets of three to four tracer calves each were introduced onto pasture at each site over a 2 year period with time of turn out onto pasture corresponding to late spring, mid-summer, late fall and late winter. At Corvallis, a distinct seasonality in parasite transmission was evident, peaking during the fall and winter. At Langlois, transmission was fairly constant throughout the year. No discernible patterns were evident at either Klamath Falls or Fort Rock. Eight nematode genera were found during the study. Ostertagia, Cooperia, Nematodirus and Trichostrongylus were present at all study sites and were the most common genera at each. Trichuris was found at all sites except Klamath Falls. Oesophagostomum was present in tracers only from Langlois and Corvallis while Haemonchus was found only at Klamath Falls and Fort Rock. Capillaria was only present at Klamath Falls. Where possible, specific transmission patterns for Nematodirus, Cooperia, and Ostertagia were determined for each site. Nematodirus was transmitted fairly steadily at both Langlois and Corvallis but was quite variable at Fort Rock. Developmental arrest was detected in this genus at all study sites during the fall and/or winter. Cooperia exhibited the most seasonally defined pattern of transmission, peaking during the fall and winter at Langlois, Corvallis and Klamath Falls. Hypobiotic larvae of Cooperia were present during the fall and/or winter only at Langlois and Corvallis. Peak transmission of Ostertagia at Langlois and Corvallis occurred during the fall and winter. At Fort Rock, transmission was lowest in the fall and increased in the winter. Hypobiotic larvae were evident in the fall and winter at Corvallis, Fort Rock and Klamath Falls. These data suggest Type II ostertagiasis may occur in late winter through spring in these areas. Hypobiotic larvae of Ostertagia were not detected at Langlois. The lack of appropriate environmental stimuli is one possible explanation for the apparent lack of hypobiosis at that site.     

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 (257bp), Haemonchus placei (176bp), Oesophagostomum radiatum (329bp), Trichostrongylus colubriformis (243bp) and Cooperia oncophora (151bp). 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.     

Growing cattle on winter wheat pasture: management and herd health considerations.

Some management and supplementation strategies that have potential to improve efficiency of production of wheat pasture stocker and feeder cattle; decrease production risk and income variability, and thereby increase growth of the industry; and strengthen the economies of rural communities in the southern Great Plains are presented in this article.     

Efficacy of orally administered moxidectin against naturally acquired gastrointestinal nematodes in cattle.

Anthelmintic efficacy of moxidectin, an experimental antiparasitic macrocyclic lactone, was evaluated in a group of 15 calves harboring naturally acquired gastrointestinal nematodes. Three groups of 5 calves each served as untreated controls (group 1) or principals that were given moxidectin PO at the rate of 0.2 mg/kg (group 2) or 0.4 mg/kg (group 3) of body weight. Equal numbers of control and treated calves were necropsied for parasite recovery on days 10 (3 control and 3 of each treatment group) and 11 (2 control and 2 of each treatment group) after treatment. Efficacies at both doses were greater than 99.8 and 99.9% against active and inhibited larvae and adults of Ostertagia spp, respectively. The overall mean efficacy of each dose was greater than 99.9%.