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1.
Romanov X Rasa Aragonesa ewes rearing twins and kept on pasture at a mean stocking density of 35 ewes ha-1 were used to study the epidemiology of parasitic gastro-enteritis under an intensive grazing system on irrigated land in the northeast of Spain. Measurements were made of the population of infective larvae on the pasture, level of serum pepsinogen, faecal worm eggs in ewes and lambs, and lamb growth rates. In addition, postmortem worm counts from "indicator" lambs were used to establish the level of infection at each rotational grazing cycle. Two generations of parasites were identified in the experiment. One of them, derived from the eggs deposited the previous autumn, gave rise to the first infection of the animals in March and April. This was responsible for the first outbreak of parasitism in the lambs. This was indicated by an increase in serum pepsinogen levels, the appearance of diarrhoea and a significant decrease in lamb growth rates. Ostertagia spp., Nematodirus spp. and Trichostrongylus spp. were present. The second generation, which appeared during May, was derived from the eggs of the previous generation and gave rise to an outbreak of parasitism in the lambs at the beginning of May and the middle of June. Haemonchus spp. and Chabertia ovina were present. Under the conditions of this experiment, the overwintering larvae have an important epidemiological significance as the gastro-intestinal nematodes are one of the main limiting factors for developing intensive sheep production systems.  相似文献   

2.
The effectiveness of albendazole in a controlled-release bolus in controlling gastrointestinal nematodes in lambs was assessed during the summer of 1986. Faecal egg counts were almost entirely negative throughout in the treated group and larval challenge remained low at below 2000 larvae kg-1. Untreated control lambs showed a characteristic pattern of auto-infection, culminating in a peak pasture larval count of over 70,000 larvae kg-1 and an outbreak of parasitic gastroenteritis in September associated with a serum pepsinogen concentration of 1.183 IU tyrosine and a mean worm burden of 91,165 nematodes at necropsy, including Ostertagia, Trichostrongylus and Nematodirus species. Subject to the restrictions imposed by the size of the bolus, this was considered to be a highly effective method of seasonal parasite control.  相似文献   

3.
Faecal egg counts were determined twice weekly for two groups of four-month-old worm free cross Suffolk lambs experimentally infected with 100 and 320 Ostertagia circumcincta larvae, five times per week for 20 weeks. The group mean egg count in both groups rose to a maximum of approximately 500 eggs per gram during weeks 12 to 14 and had fallen to less than half of that value at slaughter. There was no statistical difference in egg output between these two groups or between them and a comparable group of lambs receiving 4000 Ostertagia circumcincta larvae per day. No significant changes in live weight gain or serum pepsinogen levels were observed in the lambs given 100 and 320 larvae per day.  相似文献   

4.
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.  相似文献   

5.
The effect of forward (F) and lateral (L) creep grazing, as two possible management alternatives of intensive production systems, on the gastro-intestinal nematode epidemiology of ewes and lambs was studied. Two groups of Romanov x Rasa Aragonesa ewes rearing twins and maintained on an autumn-contaminated pasture at a mean stocking density of 35 ewes ha-1, were used. Measurements were made of the population of infective larvae on the pasture, level of serum pepsinogen, worm eggs in faeces of ewes and lambs, and lambs' growth rate. In addition, post-mortem worm counts from 'indicator' lambs were used to establish the level of infection at each rotational grazing cycle. Two different waves of nematode infection were identified. In both treatments, the over-wintering larvae were responsible for the first outbreak of parasitism which was particularly important for lambs on Treatment F. The second wave of infection apparently came up with several overlapped L3 generations and had different effects on the animals of each group. While early pasture contamination was suffered by the lambs of Treatment F, lambs on Treatment L were not seriously affected until the end of the third grazing cycle (end of May). The different grazing behaviour of lambs in both treatments appeared to be related to the outbreak of parasitism in lambs. The general pattern of liveweight gains was similar for both groups of animals. However, during the first 90 days on pasture lamb growth rate under Treatment L (193 g day-1) was significantly higher than that under Treatment F (164 g day-1). The serum pepsinogen values, worm burdens and liveweight gains indicate that under intensive systems where lateral creep grazing is allowed for lambs, the level of parasite infection is maintained within acceptable limits for the first 90 days on pasture with lambs' growth rate close to their potential. However, the parasitic consequences of grazing under a forward creeping system indicate that anthelmintic drenchings should be used at lambing and at 3-week intervals thereafter during the first 42 days on pasture, after which the risk of contamination from the over-wintering population is over.  相似文献   

6.
AIMS: To compare the susceptibility to parasitism by Ostertagia circumcincta of lambs fed entirely with bovine milk or weaned on to solid feed at 3 weeks of age. In addition, the effect of a single daily feed of milk on worm burdens was assessed. METHODS: Eight lambs were assigned to each of the 3 diets: milk (M), milk plus solid feed (cereal-based pellets and lucerne chaff) (MS), or solid feed only (S). Those to be fed solid feed were converted from complete milk feeding to the designated diet during their third week of life. From 3 weeks of age, all lambs were infected with 1000 O. circumcincta larvae twice weekly for 6 weeks; 4 lambs from each diet group were given normal sheathed L3 and another 4 were infected with exsheathed larvae. Faecal egg counts (FEC) and serum gastrin and pepsinogen concentrations were monitored from Day 17 after first infection, and worm burdens and abomasal pH and morphology were determined at necropsy. RESULTS: Total worm burdens and FEC were significantly lower in the M than MS and S groups, whereas there was no significant difference between those receiving sheathed and exsheathed larvae. The milk-fed lambs had a smaller reticulo-rumen and omasum and a more acidic abomasal pH. Serum gastrin and pepsinogen were increased in all groups, irrespective of diet or type of larvae used for infection. CONCLUSIONS: The cause of the lower worm establishment in lambs fed only milk was probably not failure to exsheath in the immature gastro-intestinal tract, as there were similar worm burdens in lambs whether sheathed or exsheathed larvae were administered. The lower pH of the abomasal contents of the preruminant lambs may have been a factor, as the parasites have previously been shown to die more rapidly in vitro at low pH. Alternatively, the milk itself had adverse effects on the parasites, but was ineffective when combined with solid feed. There was no benefit from feeding a milk plus solid diet over a solid diet.  相似文献   

7.
Serum pepsinogen levels and Ostertagia ostertagi populations in clinically normal grass-fed bullocks were investigated in three groups of 10 prime cattle aged between 2.5 and 2.75 years slaughtered in late summer (February), early autumn (March) and late autumn (May) respectively. Apart from occasional foci of mucosal hyperplasia abomasa were grossly normal. Serum pepsinogen levels ranged between 0.2 and 2.5 i.u./l with group means of 1.4, l.5 and 1.3 i.u./l. O. ostertagi counts ranged between 0 and 5,194 with group means of 734,630 and 701 worms. The composition of the worm populations varied with a higher proportion of adults recovered in February and very few worms from most cattle in March, suggesting the termination of a parasite generation. An increase in numbers of early fourth-stage larvae in May indicated exposure to a new generation. These changes were not reflected in the pepsinogen levels. The findings are discussed in relation to the adequacy of the pepsinogen assay as a diagnostic aid in field infections, animal age, and correlations between pepsinogen levels and parasite populations.  相似文献   

8.
A study was conducted of the monthly fluctuations of worm burdens and arrested development of gastrointestinal (GI) nematodes in sheep from a commercial farm of the Ebro valley (Spain). Twenty-four previously helminth-free female lambs (permanent lambs) grazed together with a flock of 500 resident ewes for 12 months following a three lambing/2-year reproductive management system. Two helminth-free lambs (tracer lambs) were added to the flock each month and allowed to graze for 4 weeks. Measurements were made of the population of infective larvae on the pasture, and of levels of serum pepsinogen and faecal worm eggs in ewes and lambs. Additionally, post-mortem worm counts from two tracer and two permanent lambs were used to establish the level of infection at monthly intervals. Three generations of parasites were identified in the experiment. The generation derived from eggs deposited the previous autumn gave rise to the first infection of the animals in January and May. This infection had low consequences for the animals, but it signified the initiation of infection and the resumption of the annual cycle of pasture contamination. The second generation, appearing between June and July, was the year's most important source of infection and gave rise to an outbreak of parasitism in permanent lambs. This was indicated by an increase in levels of serum pepsinogen, the appearance of diarrhoea, and an important decrease in lamb growth rates. The third wave of infection, occurring in October and November, there was less impact than the previous one with respect to the level of infection, but it was the origin of the future over-wintering population. Teladorsagia circumcincta was the predominant species, followed by Haemonchus contortus and Trichostrongylus colubriformis. The highest numbers of worm recovered from both the tracer and permanent lambs were observed in July, with average numbers of 7900 and 19,200, respectively.The inhibition phenomenon was more evident in permanent than in tracer lambs, and mainly affected H. contortus as evidenced by populations exhibiting arrested larvae values of over 70% in January and February.Results obtained in this study confirm the epidemiological importance of the over-wintering L(3) generation as the initial source of the animal's infection and the origin of the annual resumption of pasture contamination cycles.  相似文献   

9.
A flock of spring born lambs was continuously exposed to natural parasite infection from birth until selected for slaughter in groups of two or three, at monthly intervals throughout winter and spring for abomasal worm counts. Meteorological data were recorded and regular estimates of infective pasture larval availability were made. Parasite population changes and inhibition patterns for Ostertagia spp, Haemonchus contortus and Trichostrongylus axei were recorded. Ostertagia spp were found to survive well both on the pasture and within the host, principally as arrested larvae. H contortus overwintered almost entirely in the host in the inhibited form and T axei overwintered mainly in the host, but in the adult stage.  相似文献   

10.
Serum pepsinogen levels and Ostertagia ostertugi populations in clinically normal grass-fed bullocks were investigated in three groups of 10 prime cattle aged between 2.5 and 2.75 years slaughtered in late summer (February), early autumn (March) and late autumn (May) respectively. Apart from occasional foci of mucosal hyperplasia abomasa were grossly normal. Serum pepsinogen levels ranged between 0.2 and 2.5 i.u./l with group means of 1.4,l.S and 1.3 i.u./l. O. ostertagi counts ranged between 0 and5,194 with group means of 734,630 and 701 worms. The composition of the worm populations varied with a higher proportion of adults recovered in February and very few worms from most cattle in March, suggesting the termination of a parasite generation. An increase in numbers of early fourth-stage larvae in May indicated exposure to a new generation. These changes were not reflected in the pepsinogen levels.

The findings are discussed in relation to the adequacy of the pepsinogen assay as a diagnostic aid in field infections, animal age, and correlations between pepsinogen levels and parasite populations.  相似文献   

11.
As part of a trial to test the profitability of finishing weaner lambs over winter and spring on the Highveld of Gauteng province, an investigation was carried out over 4 consecutive years as to whether or not worm control was necessary while the lambs were on irrigated, improved pastures. Pastures that had not been grazed by sheep or other livestock for at least 5 years were planted to annual ryegrass (Lolium multiflora) that was ploughed under and replanted annually. Weaner lambs were randomly divided into either 2 (A and B) or 3 (A, B and C) groups and finished from April/May to November/December on a separate pasture per group. While Group A lambs were dewormed before being placed on pasture, those in Groups B and C were not. Faecal egg counts were performed at irregular intervals, and when the lambs were sold at the conclusion of each year's trial, the gastrointestinal tracts of 4-5 lambs per trial group were processed for worm recovery. Haemonchus contortus was the dominant worm species, while Trichostrongylus colubriformis, Ostertagia circumcincta and Trichuris spp. were encountered sporadically. From the results obtained it seems unlikely that there is appreciable 'carry-over' of the various worm species from year to year on pastures that are ploughed and replanted annually; thus it is improbable that there will be a build-up of anthelmintic-resistant worms. While on pasture, no drenching was required for the Group A lambs (dewormed before placing on the pasture), nor in 2 of the 4 years in Groups B or B+C that were not drenched and were lightly infected at the start. In the remaining 2 years Groups B or B+C were drenched once only during the course of each trial. Thus, under the conditions as in this study, little worm control is necessary, provided faecal worm egg counts are done to gauge the levels of infection before the lambs are placed on pasture, and to guard against the possibility of an increase in worm burdens thereafter in some years. Also, because of the apparent lack of carry-over between years, anthelmintic treatment at the time of introduction of the lambs or during the period of finishing should be safe as regards progressive selection for anthelmintic resistance. It is also likely to be cost-effective, considering the low cost of anthelmintics in relation to the price of lambs, to counter the possibility of a loss in production if lambs were to harbour relatively heavy worm burdens when introduced.  相似文献   

12.
Six-month-old lambs that had been naturally infected with predominantly Teladorsagia (Ostertagia) circumcincta were tested for plasma pepsinogen concentrations because pepsinogen concentrations may reflect the extent of damage to the abomasum. The distribution of pepsinogen concentrations among these lambs was positively skewed with most individuals having relatively low concentrations. Pepsinogen concentrations were more strongly associated with variation in the mean length of the adult female worms than with variation in the number of nematodes present. Previous trials have suggested that genetic variation in the growth of lambs is strongly influenced by genetic variation in worm length. Together these results imply that variation among lambs in the pathogenic effects of T. circumcincta depends upon the mean size of the worms as well as the number of worms present.  相似文献   

13.
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.  相似文献   

14.
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)  相似文献   

15.
A study was conducted to examine the role of nutrition in the development of gastrointestinal (GI) parasitism, performance and pathophysiology of parasitism in female lambs. Forty-four months old ewe lambs received for 6 weeks 0, 1500 or 7000 L(3) larvae of Teladorsagia circumcincta in two doses per week. The animals were given access to a pelleted diet to meet energy requirements for gaining weight close to their potential (H) or approximately 50% of it (L). The level of protein in the diet was 20-30% above requirements for both planes of nutrition.Measurements of body weight, serum pepsinogen concentration and faecal egg counts were taken at weekly intervals. All animals were slaughtered 2 weeks after the last larval dosing for estimation of worm count, carcass composition and reproductive tract development.Voluntary intake of infected animals decreased by approximately 10%. Both nutrition and infection influenced lamb performance and carcass composition. However, no direct effects on reproductive tract parameters due to the presence of infection were observed.The level of L(3) infection showed a significant effect not only on faecal egg counts and on worm burden, as it could be expected, but also on the proportion of females to males, which increased significantly with the level of infection.While the plane of nutrition did not show a significant effect on faecal egg counts or on worm burden, surprisingly, both female worm size and their fecundity decreased significantly with the level of nutrition. This response was accompanied by a significant increase in the concentration of circulating eosinophils suggesting that the immune response of lambs consuming high levels of energy was enhanced compared to that of lambs kept on a restricted diet.Results herein show that in young female lambs fed on adequate levels of protein, an improvement in energy supply does not only improve carcass characteristics but clearly enhances the development of resistance to GI nematodes infection. This may have decisive management implications for the control of parasitic infections in sustainable production systems.  相似文献   

16.
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.  相似文献   

17.
In order to determine whether the efficacy of moxidectin against Ostertagia circumcincta is enhanced by its persistency, therapeutic efficacy was compared at intervals after treatment and with that of ivermectin, a closely related but more transient endectocide. Groups of 7-month-old New Zealand Romney lambs were infected with a strain of O. circumcincta known to be resistant to moxidectin. At patency of the infections, groups of lambs were treated with either moxidectin or ivermectin at the manufacturer's recommended dosages, or left untreated. At 3, 6 and 10 days post-treatment, faecal egg count was measured and groups of lambs were slaughtered for estimation of adult worm burden. Drug-resistant worm burdens were significantly reduced in those animals treated with moxidectin but not in those treated with ivermectin. No effect of time of slaughter on worm burden was observed with either drug, demonstrating that the higher therapeutic efficacy of moxidectin against this parasite was not due to an increased period of drug exposure. Faecal egg counts in the moxidectin treated animals increased with time after treatment indicating a temporary suppression of egg output by surviving worms. The implications of these findings on selection for anthelmintic resistance are discussed.  相似文献   

18.
Fifteen worm-free lambs (two-and-a-half to three months or four to four-and-a-half months old) were infected with 3500 or 4000 Ostertagia ostertagi larvae on five days each week for six weeks, and their performance compared to that of controls. Eleven lambs were killed after eight weeks and four were challenged with O circumcincta to determine whether any cross resistance had developed. A feature of the O ostertagi infection was the considerable variation in response. Overall liveweight gain was lowered by 24 per cent in the two-and-a-half to three-month-old infected lambs, mainly due to reductions of 27 to 40 per cent in four of the seven lambs. There was no consistent effect in the older lambs. The worm populations consisted mainly of early fourth stage larvae and developing worms, but a small percentage reached sexual maturity and these produced a low faecal egg count (1 to 63 eggs per gram). Numerous intraluminal refractive crystals were present in the gut of both adult worms and developing stages, possibly reflecting degenerative changes. Hypertrophy of the abomasal mucosa with patchy loss of differentiation was a feature of the infection, and in four lambs serum pepsinogen concentrations were elevated. Exposure to O ostertagi did confer some protection against challenge with O circumcincta in that worm counts were reduced to about 60 per cent of those in controls, although no increase was observed in the numbers of arrested larvae. The successful passage of O ostertagi through young lambs could be important in mixed or alternate grazing systems by providing a reservoir of infection for the alternate host.  相似文献   

19.
Attempts were made to immunise lambs by the intramuscular injection of either lyophilised or concentrated metabolites produced by Ostertagia circumcincta when grown in vitro, or macerated fourth and fifth stage worms. The lyophilised metabolites did not stimulate protection against the establishment of worms in nine-months-old lambs but the macerated worms and concentrated metabolites elicited protection in six-months-old and three-months-old lambs respectively. The worm burdens and worm egg counts of the immunised lambs were less than those of control lambs.  相似文献   

20.
Over a period of one year, from March 1984 to April 1985, the abomasa of 157 dairy cows in East Flanders (Belgium) were collected and examined for the presence of nematodes. Faeces and blood were also collected from the animals. No worms were recovered from 18 cows (11.5%), 118 cows (75%) had a low to moderate worm burden (10-10,000) and 21 cows (13.5%) a high worm burden (greater than 10,000). The geometric mean total number was 2171. Ostertagia ostertagi and Trichostrongylus axei were the main species involved, with the former accounting for 90% of all trichostrongyles recovered. For both worms a seasonal pattern was evident, with the highest worm counts in December-January. Between December and February greater than 97% of the Ostertagia spp. worm burden were EL4. For all animals the average pepsinogen level was 1391 +/- 494 mU tyrosine with no statistically significant relationship between pepsinogen levels and the total number of gastric nematodes. Only 45% of the faeces samples were positive for strongylid eggs with a mean of 43 eggs per gram. The percentage generic composition of L3 larvae collected from faeces was 62% Ostertagia, 18% Trichostrongylus, 6% Cooperia, 4% Oesophagostomum and 0.2% Bunostomum.  相似文献   

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