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1.
J L Duncan J Armour K Bairden G M Urquhart R J J?rgensen 《The Veterinary record》1979,104(13):274-278
In the West of Scotland the epidemiology of parasitic bronchitis in grazing calves was studied over a two year period with the aid of tracer calves and herbage examinations for Dictyocaulus viviparus larvae. The observations of both years emphasised the importance of overwintered lungworm larvae as a source of disease. In the first year it was shown that the ingestion and development of these overwintered larvae were, by themselves, directly responsible for severe morbidity, high faecal larval counts and deaths. In the second year it was shown that pasture ungrazed during the winter and spring and from which a hay crop was removed in mid-summer was still capable of producing clinical parasitic bronchitis in susceptible calves within three to four weeks of their introduction in later summer. In both years there was some evidence that the outbreaks appeared to be associated with the sudden availability of infective larvae on the herbage. The possibility that such larvae may have survived for many months in the soil is discussed. Despite the heavy challenge with lungworm larvae experienced by the grazing calves in the first year those vaccinated with lungworm vaccine survived, their clinical signs were mild and of short duration and their faecal larval output was greatly reduced. 相似文献
2.
Two groups of yearling cattle which had been treated with ivermectin either three and eight, or three, eight and 13 weeks after turn out to trichostrongyle contaminated pasture in their first grazing season were exposed in the following season to natural challenge with helminth parasites. To assess their immunity to this challenge each group shared a pasture with parasite naive first season calves. No anthelmintic treatments were administered at any time during the year. Throughout the grazing period the yearlings showed normal respiratory rates, negative faecal lungworm larval counts, and, relative to the calves, low faecal trichostrongyle egg counts. All the first season calves developed patent lungworm infections and on one occasion the mean respiratory rates of each group of calves were significantly greater than those of the yearling cattle. At the end of the grazing period, from early May until late September or October 1986, the cattle were removed from pasture and together with parasite naive controls challenged with either 10 or 22 third stage larvae of Dictyocaulus viviparus/kg bodyweight and necropsied between 18 and 23 days later. Although the experimental challenge resulted in relatively heavy lungworm infection of the naive controls, none of the yearlings and only three of the 11 calves which had been at pasture were found to be infected. However, large numbers of arrested fourth stage larvae of Ostertagia ostertagi were present in all the naturally infected yearlings and calves. 相似文献
3.
The efficacy of the morantel sustained release bolus in controlling gastrointestinal and lungworm parasites when used in first-season grazing animals which followed older animals onto spring pasture (deprime system) was assessed in three trials conducted in Normandy, France. In each trial first-season grazing calves were equally allocated onto two separate but equivalent paddocks where they remained throughout the grazing season. A morantel sustained release bolus was administered to one group of animals at turnout, the other group remained as controls. The effect of the treatment on contamination of pasture (herbage larval counts and tracer worm counts), on faecal worm egg and lungworm larval counts, and on weight gain performance of the principal animals was assessed. In all three trials, worm egg output in the bolus-treated animals was substantially lower throughout the season compared with the control animals. Worm burdens of tracer calves grazing pastures of the treated cattle were also reduced compared with tracer calves grazing control pastures. Clinical parasitic gastroenteritis occurred in the control animals but not in the bolus-treated animals in one trial. Overall the bolus-treated animals outperformed the controls by a mean weight gain advantage of 10.5 kg (P less than 0.01). 相似文献
4.
E. CLAEREBOUT W. HOLLANDERS H. DE COCK J. VERCRUYSSE H. HIDERSON 《Journal of veterinary pharmacology and therapeutics》1994,17(3):232-236
The effect of an ivermectin sustained-release bolus (I-SRB) on the epidemiology of nematode parasites and on calf productivity was evaluated in a field trial under Northwestern European conditions. Twenty parasite-naive female Friesian calves (principals) aged 5–9 months were used together with six male Friesian tracer calves. Principal calves were allocated by restricted randomization on day 0 body weight to either an untreated control group or a group given one I-SRB, designed to deliver 12 mg ivermectin per day for 135 days, orally on day 0. Each group was grazed on adjacent paddocks, naturally contaminated with parasitic nematode larvae, from 13 May 1991 (day 0) until housing on 30 September (day 140). Body weights of principal calves were recorded and individual blood and faecal samples taken at regular intervals throughout the trial. Pasture nematode contamination was monitored by larval counts on herbage and by worm counts of tracer calves grazed on each paddock from day 126 to day 140. Nematode contamination levels on the control paddock did not rise until the end of the grazing season, as a result of a mid-summer drought period. The period of exposure to a high larval challenge was too short to provoke body weight losses and clinical parasitic gastroenteritis in control calves. Use of the I-SRB resulted in zero faecal egg counts of trichostrongyles during the whole pasture season, thereby preventing a build-up of parasitic gastrointestinal nematodes on pasture. During the second grazing season no signs of parasitic gastroenteritis were detected in any animal, but an outbreak of parasitic bronchitis (PB) was observed in both experimental groups, indicating that PB can occur in older cattle regardless of the control measures taken to prevent clinical parasitism during the first grazing season. 相似文献
5.
G A Oakley 《The Veterinary record》1982,111(17):385-388
Seventy-one worm-free Friesian calves were allocated by weight to three trial groups (1, 3 and 4) of 18 and a control group (2) of 17 animals. Calves in group 1 were vaccinated with a bovine lungworm oral vaccine on days 0 and 28, and on day 42 all groups were turned out to graze together on pasture known to be infected with Dictyocaulus viviparus larvae. Twenty-eight days after first exposure to infection one control calf died of parasitic bronchitis. Anthelmintic medication consisting of two doses of levamisole (7 . 5 mg/kg) at 14 day intervals was promptly administered to group 3 calves and three doses at the same intervals to group 4 calves. All calves were challenged with 20,000 infective D viviparus larvae on day 147. Calves were weighed every 14 days throughout the trial which ended 42 days after challenge. Pasture contamination and infectivity were monitored by pasture larval counts and tracer calves. Statistically there was no significant difference between the performances of treated and vaccinated groups before challenge but all were significantly superior to the control group. After challenge the productivity of all experimental groups was temporarily depressed but the levamisole treated cattle recovered more rapidly becoming significantly heavier than the vaccinates at the end of the trial. The mean group weight gains over the trial period were 89 . 92, 63 . 87, 88 . 67 and 98 . 70 kg in groups 1, 2, 3 and 4 respectively. 相似文献
6.
M Eysker J H Boersema J B Cornelissen F N Kooyman W A de Leeuw 《Veterinary parasitology》1992,41(1-2):127-135
A study was made of the possibility of reducing lungworm infections in young grazing calves by rotational grazing for weekly periods on six paddocks. For this purpose three groups of four calves each were grazed on separate pastures in 1989, whereas a fourth group served as a permanently housed control group. Two groups of calves were infected experimentally with six doses of 10 larvae of Dictyocaulus viviparus during the first 3 weeks on pasture. In the third group, low natural infections with overwintered larvae occurred. One of the experimentally infected groups was rotationally grazed for weekly periods on six small plots while both other groups were set-stocked. Faecal larval counts and worm counts in tracer calves demonstrated lower lungworm infections in the rotationally grazed group than in both set-stocked groups. However, the numbers of worms found after challenge infection and subsequent necropsy were relatively high in the rotationally grazed group, indicating that development of immunity was less than in both other groups. Owing to the dry weather conditions in the summer of 1989, no serious clinical signs of husk developed in any of the three groups. These dry conditions, however, did not prevent the build-up of heavy pasture infectivity with gastrointestinal nematodes resulting in heavy worm burdens and serious clinical signs in tracer calves grazing for 4 days in August and September-October, respectively. This implies that rotational grazing did not have a clear effect on build-up of gastrointestinal nematode infections. 相似文献
7.
The patterns of gastrointestinal and lung helminth infections in grazing calves were studied in two small grazing experiments carried out between May and October in 1985 and 1986, respectively, at Utrecht State University. For lungworm a very rapid translation of infective larvae was seen in both experiments, resulting in a rapid build-up of the worm burdens, and in July the second generation of Dictyocaulus caused husk. After the end of patency for lungworm, in the beginning of August, a rapid decrease in pasture infectivity, measured by pasture larval counts and worm counts of tracer calves, was observed. For the gastrointestinal nematodes the translation of infective larvae was much slower as a distinct 'midsummer increase' of pasture infectivity was not seen before the end of July. The worm counts of the tracer calves and the pasture larval counts showed that these larvae remained on pasture much longer than the lungworm larvae. As in Dictyocaulus, patency stopped in August-September in Nematodirus but not in Ostertagia and Cooperia, indicating a slower rate of development of immunity in both latter genera. In contrast to lungworm, the results indicate a clear and predictable seasonal pattern for gastrointestinal helminth infections. 相似文献
8.
F H Borgsteede W P vd Burg W A de Leeuw J B Cornelissen J E van Dijk 《The Veterinary quarterly》1990,12(2):65-72
The efficacy of a levamisole sustained-release bolus to prevent parasitic bronchitis in calves in their first grazing season was compared to ivermectin treatment at three, eight and thirteen weeks after turn out. Contamination of the pasture was established by experimentally infected seeder calves. Twenty calves were split into two groups. Ten calves of one group received a bolus at the start of the experiment. In the other group the calves were treated with ivermectin at 21, 56 and 91 days. Two principal calves from each group were killed during the experiment to study histopathological changes. Pairs of tracer calves were introduced on both pastures at intervals of four weeks throughout the grazing period. The permanent calves were challenged with lungworm larvae at housing and slaughtered four weeks later. Both systems prevented parasitic bronchitis. Larval output was completely reduced in the ivermectin-treated calves while all bolus-treated calves excreted larvae at certain times. The highest group average was 4 larvae per gram faeces. Eosinophilia, ELISA-titres and histopathological changes confirmed the differences in larval uptake. Challenge infection was not successful in either group and no worms were found at slaughter. Weight gain was significantly different at housing in favour of the ivermectin-treated calves, but after challenge this was reduced due to a higher weight gain in the bolus-treated calves. The practical consequences of the results have been discussed. 相似文献
9.
R.Jess Jørgensen 《Veterinary parasitology》1980,7(2):153-167
A field experiment was conducted over two grazing seaons with calves on a permanent pasture in order to follow the pattern of infection with Dictyocaulus viviparus. Infective larvae persisted during the first, but not during the second, winter of observation. By means of the agar-bile herbage technique, a moderate first peak of infection was demonstrated in the pasture 2–3 weeks before the appearance of respiratory signs in the calves. Fluctuations in faecal larval output were reflected in the herbage contamination with infective larvae close to faecal pats. This, as well as the horizontal dispersion of larvae in the pasture, took place in less than a week. The proportion of lungworm larvae recovered away from faeces was low during a period of dry and hot weather while herbage sampling at two-hour intervals during two days showed an increase in herbage contamination with lungworm larvae, but not with trichostrongyle larvae between 10 a.m. and 12 noon.The infectivity of the pasture was monitored by tracer calves and compared with the results of the pasture sampling. The general course of the infection in the calves and in the pasture was the results of interaction between them. In addition, the pasture infection was influenced by climate and the infection in the calves by the development of immunity. The course of infection in individuals appeared to have an influence on the general course of the infection through the contamination of the pasture. 相似文献
10.
Effect of ivermectin delivered from a sustained-release bolus on the productivity of beef cattle in Oregon 总被引：1，自引：0，他引：1
The effect of ivermectin delivered from a sustained-release bolus (I-SRB) on the weight gain of beef cattle through a grazing season was evaluated using 20 yearling beef steer calves randomly divided into two groups of ten animals each. Calves in the control group each received a placebo bolus, while those in the treatment group each received an I-SRB designed to release 12 mg ivermectin day-1 for approximately 90 days. All animals were weighted and samples of feces were collected from the rectum at monthly intervals, beginning on Day 0, until trial termination (Day 148). Pasture larval counts were also conducted on herbage collected on each sampling date. On Day 119, two control and two treated calves were removed from pasture, housed in isolation for 3 weeks, then necropsied for recovery of gastrointestinal nematodes. Three sets of parasite-naive tracer calves were utilized to evaluate the initial, interim and final levels of pasture contamination by nematode larvae. A fourth set was used to evaluate the level of pasture contamination the following spring. The use of the I-SRB resulted in a greater than 99% reduction in fecal egg counts of trichostrongyles and numbers of gastrointestinal nematodes in the treated principals, as well as an average daily gain advantage of 0.114 kg over the 148 day period. A 67-98% reduction in pasture larval nematode contamination occurred on pastures grazed by the treated animals, as indicated by the parasite burden in tracer calves and pasture larval counts. The treatment effect was eventually lost by the following spring since tracer calves on the treated pasture had only 33% fewer nematodes than those on the control pasture. 相似文献
11.
On two dairy farms it was attempted to eradicate lungworm, Dictyocaulus viviparus, by means of a single mass-treatment of all cattle that had been grazed the previous year(s), before turnout in the spring. Both farms experienced two years of lungworm outbreaks in the adult dairy herd prior to this study. Following confirmation that both herds contained lungworm carriers, all animals older than approximately 6 months were treated with eprinomectin in March 2007. One week after treatment none of the animals were shedding lungworm larvae. Subsequently, animals were pastured according to normal farm routine. From August to November all first-calving heifers were coprologically and serologically monitored for lungworm infection. During 2007 both farms remained lungworm-negative and did not report any clinical sign indicative for a lungworm infection. The following year, on one of the farms replacements grazing on cow pastures, started showing signs of parasitic bronchitis which was serologically confirmed. The other herd remained free of parasitic bronchitis until at least the fourth year after the mass treatment, although some coughing was noticed in 2008 among first-lactation heifers. It was concluded that a single mass-treatment before the grazing season may be useful to break a series of annual lungworm outbreaks. However, it is not a secure method to prevent parasitic bronchitis for more than one year. 相似文献
12.
N E Downey 《Veterinary parasitology》1983,12(3-4):273-281
The morantel sustained release bolus was administered at turnout to first-season grazing calves in order to assess its efficacy in the seasonal control of infection by nematode parasites in Ireland. The pastures grazed by control calves showed a marked increase in gastrointestinal trichostrongylid infective larvae by September, while numbers of infective larvae on pasture grazed by bolus-treated calves remained at a low level throughout the grazing season. In consequence, the controls showed significantly higher worm egg counts in late season and significantly higher worm burdens (mainly Ostertagia spp) at necropsy carried out in November on representative number of principal animals selected from each group. These reduced worm burdens were attributed to the suppression of egg output during the early part of the season as a result of treatment with the morantel sustained release bolus at turnout in the spring. Pasture contamination with Dictyocaulus viviparus larvae was present on all treatment pastures. The bolus-treated calves however were subjected to an increase in D. viviparus infection which occurred on their pasture in late season after the active life of the bolus had expired. It was concluded that bolus treatment delayed (rather than prevented) the buildup of D. viviparus infection on the pasture by 60-90 days. 相似文献
13.
Rolf Jess Jrgensen 《Acta veterinaria Scandinavica》1980,21(4):658
A combined epidemiology and control investigation was performed with parasite-free calves turned out in May on a permanent pasture naturally contaminated with lungworm larvae the previous year. Before the start the field was divided into two plots. One plot was grazed by 12 calves after the first week of May. The other plot was grazed by 12 calves turned out two weeks later. Both groups as well as the plots grazed by them were subdivided six weeks after turning out. Based on a predicted rise in the pasture larval contamination with infective lungworm larvae, one subgroup of each main group was given a tactical anthelmintic treatment six weeks and again eight weeks after their date of turning out. Patent infections from overwintered larvae were detected in both main groups after four weeks of grazing, but not in all individuals of the late turned-out group. The excreted larvae gave rise to pathogenic pasture larval contaminations on the two initial plots five to six weeks after turning out. In the control groups, early turning-out resulted in approx. 10 times higher larval recoveries in faeces and pasture compared to late turning-out. Seven to eight weeks after turning-out critical, severe parasitic bronchitis had developed in the early turned-out control group. In the late turned-out controls, clinical signs were obvious but not critical. Outbreaks were not observed in any of the experimental subgroups, and no larval excretion was observed among them within four to five weeks following treatments. Similarly, no larvae were recovered from their pastures two weeks after treatment and onwards. A third treatment was given to both experimental groups on the same date (August 21) to suppress gastrointestinal parasitism. However, the level of this infection, appeared moderate, probably due to comparatively low precipitation and extensive supplementary feeding given in late summer to compensate for scarcity of grass. 相似文献
14.
Under experimental conditions, fenbendazole given at doses of 0.4 and 1.0 mg/kg body weight suppressed calves' faecal output of Ostertagia and Cooperia species eggs and Dictyocaulus viviparus larvae. Both dose levels were given in the form of small daily drenches and the higher level showed greater efficacy. In a grazing experiment, medication with fenbendazole at 1.0 mg/kg/day administered intermittently to calves using an automatic dose dispenser almost completely suppressed the output of trichostrongylid eggs. As a result, infection on the pasture and in the calves remained at a low level throughout the grazing season. By contrast, control pasture and control calves showed rather heavy infection from mid-August onwards with significantly lower weight gains and widespread signs of parasitic gastroenteritis. At post mortem examination of representative calves from each group in November, the medicated animals had 99 per cent less Ostertagia species, whether adults or larvae arrested at the early fourth stage, and 95 per cent less Cooperia species compared with controls. Medication in the drinking water suppressed the faecal output of D viviparus larvae for most of the grazing season by comparison with the controls but the medicated calves became infected with this parasite towards the end of the season. Until this problem is overcome, precautions against parasitic bronchitis are advised when this system of medication is adopted. 相似文献
15.
Two experiments were performed to study the effect of an oxfendazole pulse release intraruminal device (OPRB) on the development of lungworm infection and immunity in calves. Infections were monitored in OPRB-treated and control calves by faecal and pastural larval counts. Levels of immunity of grazing groups and helminth-free housed groups were compared by challenge infection. Even though signs of parasitic bronchitis were seen only in control animals, sufficient immunity had developed in OPRB-treated calves to prevent disease after a substantial challenge infection. However, the degree of immunity was less than in untreated grazing control groups and there were indications that it was related to initial infection levels. These results imply that the OPRB may successfully control parasitic bronchitis, provided that pasture larval infections are sufficient to allow the development of immunity. 相似文献
16.
An epidemiological investigation was conducted during a 1-year period on a permanent pasture naturally contaminated with Dictyocaulus viviparus and grazed by a varying number of yearling cattle. Seasonal variation in pasture infectivity to cattle was monitored by monthly slaughter of tracer calves, slaughter of pairs of resident yearlings at 30-60-day intervals, herbage larval recovery and by counts of first stage larvae in feces (modified Baermann technique) of resident cattle. A clinical outbreak of dictyocauliasis occurred during January-March 1986 and was associated with peak levels of pasture infectivity. Carrier animals were considered responsible for the survival of infection over summer. Although soil samples were taken regularly on a monthly basis to study the epidemiological importance of the soil as a source of infection, infective larvae were not recovered at any time. The epidemiological pattern observed in the present study provides basic information on the factors involved in infection and diseases outbreaks under sub-tropical conditions. 相似文献
17.
Sarkũnas M Malakauskas A Nansen P Hansen JW Paulikas V 《Acta veterinaria Scandinavica》1999,40(2):163-171
The effect of strategic treatments with ivermectin in first-season calves exposed to trichostrongyle nematodes on naturally contaminated pasture was studied. Twenty first season heifer calves were divided into 2 groups, according to live weight, and on 22nd May each group was turned out onto a 1 hectare pasture. Group A (Plot A) was treated with ivermectin at weeks 3, 8 and 13 after turn out, while group B (Plot B) served as an untreated control group. The study showed that control calves exhibited increase in trichostrongyle egg counts in August, while treated calves were excreting low numbers of trichostrongyle eggs. Pasture larval counts on Plot B (control animals) were low during the first part of the grazing season, followed by a steep rise towards the end of July. In contrast, the numbers of infective larvae recovered from Plot A remained low throughout the season. Both groups showed comparable weight gains from May up to the middle of July. However, from then on, Group B (controls) had lower weight gains than ivermectin treated Group A. From the end of July onwards, most untreated calves (Group B) showed clinical signs of parasitic gastroenteritis. It can be concluded that the strategical ivermectin treatments were successful, and faecal egg counts, pepsinogen levels and herbage larval counts clearly demonstrated that this was accomplished through suppression of pasture contamination with nematode eggs and subsequent reduction of pasture infectivity. 相似文献
18.
Some observations on the use of the morantel sustained-release bolus in first season-grazing calves on a Belgian dairy cattle farm 总被引：1，自引：0，他引：1
The efficacy of the morantel sustained-release bolus (MSRB) in controlling gastrointestinal parasites in first-season grazing calves was evaluated on a dairy cattle farm in Belgium. The calves grazed a pasture which had been used by bolus-treated animals in the three previous years. The effect of bolus administration was determined with respect to live weight gain, faecal egg shedding, herbage larval counts, serum pepsinogen levels and ELISA antibody titres. In spite of an incomplete reduction of faecal egg shedding during the first months of the grazing season, bolus administration resulted in the prevention of parasitic gastro-enteritis in the calves. A weight gain advantage of 35,2 kg of the bolus-treated animals over the controls was noted already at two months after turnout. This weight gain advantage was maintained until housing. The usefulness of serum pepsinogen values and ELISA antibody titres as parameters in prevention experiments is stressed. Both serological parameters gave more information concerning infection level than did the faecal egg output and the herbage larval counts. 相似文献
19.
Summary The efficacy of the morantel sustained‐release bolus (MSRB) in controlling gastrointestinal parasites in first‐season grazing calves was evaluated on a dairy cattle farm in Belgium. The calves grazed a pasture which had been used by bolus‐treated animals in the three previous years. The effect of bolus administration was determined with respect to live weight gain, faecal egg shedding, herbage larval counts, serum pepsinogen levels and ELISA antibody titres. In spite of an incomplete reduction of faecal egg shedding during the first months of the grazing season, bolus administration resulted in the prevention of parasitic gastro‐enteritis in the calves. A weight gain advantage of 35,2 kg of the bolus‐treated animals over the controls was noted already at two months after turnout. This weight gain advantage was maintained until housing. The usefulness of serum pepsinogen values and ELISA antibody titres as parameters in prevention experiments is stressed. Both serological parameters gave more information concerning infection level than did the faecal egg output and the herbage larval counts. 相似文献
20.
T Schnieder A Bellmer S Wheeler 《Zentralblatt für Veterin?rmedizin. Reihe B. Journal of veterinary medicine. Series B》1992,39(8):563-570
In two field trials vaccination or different anthelmintic treatments against Dictyocaulus viviparus infections were used in 6 groups of first year grazing cattle. The antibody response to lungworm infections was determined using an ELISA. Cattle treated once or repeatedly at long intervals with levamisole developed clinical signs of dictyocaulosis. The detection of anti-D. viviparus antibodies at the end of the grazing season confirmed that these anthelmintic treatments were not able to prevent lungworm infections. Cattle that received strategically administered treatments with ivermectin remained clinically healthy. These cattle were seronegative until the end of the trial which proved the efficacy of the strategic control. Cattle that received an intraruminal slow release bolus did not develop clinical disease. However one animal shed lungworm larvae and the herd became seropositive at the end of the grazing season indicating a history of infection. The serological examination of a cattle herd at the end of the grazing season is able to demonstrate a history of lungworm infections and to determine the efficacy of anthelmintic control measures. 相似文献