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1.
An involvement of Pilobolus species fungus in the dispersal of Dictyocaulus viviparus third stage larvae from dung to surrounding herbage under Irish conditions was investigated. The presence of Pilobolus kleinii on artificial dung pats containing first stage larvae of D viviparus was associated with a 19-fold increase (P less than 0.05) in numbers of third stage larvae recovered from the surrounding herbage. A subjective examination of natural dung pats showed that the presence of Pilobolus species was significantly correlated with hours of bright sunshine (r = -0.5, P less than 0.01), total rainfall (r = 0.41, P less than 0.05) and the height of herbage surrounding the pats (r = 0.31, P less than 0.001). A multiple regression analysis showed that meteorological parameters and the height of surrounding herbage accounted for 38 per cent of the variation in growth of Pilobolus species on dung pats. The incidence of extensive damage to natural dung pats within five days of deposition, caused by biotic factors, another possible cause of D viviparus third stage larvae dispersal, varied from 0 to 92 per cent of the pats depending on their degree of dryness. 相似文献
2.
R C Krecek K D Murrell L W Douglass 《The Onderstepoort journal of veterinary research》1990,57(2):133-135
Assessments were made of the influence of several microclimatic variables on the availability of third-stage larvae of Ostertagia ostertagi, on pasture herbage. Variables most closely related to recovery of larvae from the lower herbage samples were: maximum air, mat and dung temperatures. Recovery of larvae from the upper portion of the herbage was closely correlated with dung temperature, sampling-time air temperature and maximum air temperature. Bearing in mind that the moisture threshold was maintained throughout the trial the results of this study suggest that under field conditions, larval movement of third-stage O. ostertagi larvae on herbage is regulated primarily by temperature. 相似文献
3.
Between 10 and 25% of the Dictyocaulus arnfieldi larvae excreted in faeces from a naturally infected donkey were harvested as infective stages from faecal cultures by means of Pilobolus fungi. The faeces were collected between 24 and 56 hours after drenching the donor animal with Pilobolus spores and kept at 16 +/- 2 degrees C. Most larvae were collected between the 5th and the 8th day of culturing during which period fructification and sporangium discharge also peaked. The sporangia and the adhering larvae were collected in Petri dishes inserted between the faecal mass and a light source. All recovered larvae were viable. A mean larval length of 368 microns (range 312-440 microns) and width of 14.6 microns (range 12-20 microns) was recorded for the infective stage. The method was found suitable for the recovery of infective stages for experimental purposes. The authors suggest that the Pilobolus mechanism play an important part in the spread of equine lungworm infection under field conditions similar to the situation in bovine lungworm (Dictyocaulus viviparus) infection. 相似文献
4.
C J Somers 《Research in veterinary science》1985,39(1):124-126
Recoveries of third stage Dicytocaulus viviparus larvae (L3) from Pilobolus species sporangia ranged from 23 per cent at 21 days to 3 per cent after 90 days for sporangia attached to polythene discs positioned on pasture. There was a continuous release of L3 for up to 16 days from sporangia which were placed under conditions simulating those occurring on pasture. 相似文献
5.
G A Oakley 《Research in veterinary science》1982,32(2):163-169
A five year ley pasture was used as a source of natural infection with Dictyocaulus viviparus for cattle in anthelmintic trials. Pasture larval counts, faecal larval counts of permanently grazing calves and lungworm burdens harboured by tracer calves were monitored in three grazing seasons to assess the pattern of infection. Carrier calves were introduced at the beginning of the grazing season in the first two years of the study but not in the third. In the fourth year the pasture was subdivided into two paddocks where overwintered infection with and without carrier infection were compared. A control paddock exposed to carrier infection but no overwintered infection was also monitored. Pasture larvae survived the winter but carrier infection appeared to make a larger contribution to pasture larval counts and the onset of parasitic bronchitis in susceptible calves. In the absence of grazing cattle at the end of the grazing season the concentration of D viviparus larvae on the herbage fell rapidly to undetectable levels. Discrepancies between contamination of herbage by infective D viviparus larvae and infectivity of pasture for susceptible cattle occurred in all years but were particularly marked on the third year when natural immunity appeared to influence the number of lungworms accumulating in tracer calves. Failure to recover lung worms from tracer calves cannot be regarded as an accurate indication of lungworm free pasture. In the first three years the proportion of the lungworm population which was inhibited in tracer calves was higher early and late in the grazing season and negligible in mid season. This suggests that a predisposition to inhibition in larvae which have overwintered on pasture may influence the time of onset of parasitic bronchitis in the next grazing season, but results from the fourth year did not support this hypothesis. 相似文献
6.
M Eysker 《Research in veterinary science》1991,50(1):29-32
Dispersal of Dictyocaulus viviparus larvae by Pilobolus sporangia was studied on 29 faecal pats deposited between the end of June and late October 1988. Faecal pats were covered daily from day 3 to 4 after deposition with a large petri dish to measure the numbers of sporangia released and the numbers of larvae carried. The yield of both was variable. Dispersal of lungworm larvae was lowest on over-grazed pasture or when Pilobolus growth was very poor. When faecal pats were sheltered by a long sward, 17 per cent or more of larvae present at deposition were transported in this manner. In July and August, peak dispersal of lungworm larvae was on day 5, in September on day 6 and in October on day 7, the increasing time intervals being probably associated with decreasing temperature. 相似文献
7.
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
8.
Sirisriro A Grams R Vichasri-Grams S Ardseungneon P Pankao V Meepool A Chaithirayanon K Viyanant V Tan-Ariya P Upatham ES Sobhon P 《Veterinary parasitology》2002,104(2):119-129
Biological options for nematode parasite control are being sought, as the long-term efficacy of conventional anthelmintics comes increasingly under threat from drug-resistant parasites. Three biological methods with the potential to reduce pasture contamination by parasitic nematode larvae were examined: (a) killing of larvae developing in dung by nematophagous fungi; (b) removal of dung through earthworm ingestion; (c) burial of dung in soil as might occur through the action of dung beetles. Field trials with the test bio-control agents were carried out in autumn and spring by adding dung from sheep infected with Ostertagia (Teladorsagia) circumcincta to pots of ryegrass/white clover. The factorial treatment structure included five fungal treatments (individual applications of Duddingtonia flagrans, Monacrosporium gephyropagum and Harposporium helicoides, a combination of all the three fungi together and an untreated control), two dung burial treatments (dung buried or deposited on the soil surface) and two earthworm treatments (earthworms present or absent). D. flagrans and H. helicoides, individually or in combination, reduced recovery of infective stage larvae in experiment 1, while only H. helicoides reduced recovery in experiment 2. In both the experiments, dung burial increased the total number of larvae recovered, while the number of infective larvae were reduced by the action of earthworms. Increased recovery following burial, along with the fact that larvae moved rapidly from soil onto herbage, suggests that soil may provide a protective reservoir for infective larvae infesting herbage. 相似文献
9.
During the 1997 Swedish grazing season, faeces were collected every 3 weeks on 7 occasions from young grazing cattle with moderate nematode parasite infections. From this source 12, 400 g dung pats were set up on each sampling occasion on a specially designated area of pasture. Half of these pats were placed on pasture where it was aimed to prevent snow cover during the subsequent winter. During the grazing season, herbage growth was kept at reasonably uniform height by clipping and the dung pats were protected from destruction by animals and birds. At the time of animal turn-out the following year (7th April 1998), it was observed that all dung pats had disappeared. Assessments of the survival of infective larvae, both on pasture and in soil, were made in a circular area encompassing the location of each pat. These sampling procedures were completed within a 3 week period. All faecal deposits yielded infective larvae at turn-out the following year, with proportionally greater numbers developing from nematode eggs deposited in cattle dung during the mid third of the previous grazing season. The surface layer of soil was found to be an important reservoir for infective larvae, with numbers recovered being approximately half those found in the overlying pasture samples. No significant differences were found between the normal pasture and snow excluded pasture in the number of infective larvae recovered from both pasture and soil samples. The epidemiological consequences of these findings are discussed. 相似文献
10.
A S Fernández M Larsen P Nansen J Gr?nvold S A Henriksen H Bj?rn J Wolstrup 《Veterinary parasitology》1999,85(4):289-304
A series of experiments was carried out to examine the effects of two different isolates of the nematode-trapping fungus Duddingtonia flagrans to reduce the number of free-living larvae of the bovine lungworm, Dictyocaulus viviparus. A laboratory dose-titration assay showed that isolates CI3 and Troll A of D. flagrans significantly reduced (P < 0.05 to P < 0.001) the number of infective D. viviparus larvae in cultures at dose-levels of 6250 and 12,500 chlamydospores/g of faeces. The larval reduction capacity was significantly higher for Troll A compared to CI3 when lungworm larvae were mixed in faecal cultures with eggs of Cooperia oncophora or Ostertagia ostertagi and treated with 6250 chlamydospores/g of faeces. Both fungal isolates showed a stronger effect on gastrointestinal larvae than on lungworm larvae. Two plot trials conducted in 1996 and 1997 involved deposition of artificial faecal pats containing free-living stages of D. viviparus and C. oncophora on grass plots. Herbage around the pats was collected at regular intervals and infective larvae recovered, counted and identified. These experiments showed that both D. flagrans isolates reduced the number of gastrointestinal as well as lungworm larvae in faecal pats. During both plot trials, the transmission of C. oncophora larvae, but not D. viviparus, from faecal pats to the surrounding herbage was clearly affected by climatic conditions. After collection of faecal pats from the grass plots one month after deposition, the wet and dry weight of pats as well as organic matter content were determined. No differences were found between the fungus-treated and non-treated control pats. This indicated that the rate of degradation of faeces was not affected by the addition of the fungus. 相似文献
11.
12.
A study was conducted over 3 years (1998-2000) to investigate larval availability of gastrointestinal nematodes from faeces of cattle reared under different parasite control schemes. These cattle were part of a parallel, but separate grazing trial, and were used as donor animals for the faecal material used in this experiment. At monthly intervals, faeces were collected and pooled from three groups of first-season grazing cattle. These groups were either untreated, ivermectin bolus treated or fed the nematophagous fungus Duddingtonia flagrans. The untreated and fungus treated animals were infected with gastrointestinal nematodes and the number of eggs per gram (epg) pooled faeces ranged between 50 and 700 in the untreated group and between 25 and 525 epg in the fungus treated group. Each year between June and September, artificial 1 kg dung pats were prepared and deposited on pasture and protected from birds. The same treatments, deposition times and locations were repeated throughout the study. Larval recovery from herbage of an entire circular area surrounding the dung pats was made in a sequential fashion. This was achieved by clipping samples in replicate 1/4 sectors around the dung pats 4, 6, 8 and 10 weeks after deposition. In addition, coinciding with the usual time of livestock turn-out in early May of the following year, grass samples were taken from a circular area centred where the dung pats had been located to estimate the number of overwintered larvae, which had not been harvested during the intensive grass sampling the previous year. It was found that recovery and number of infective larvae varied considerably within and between seasons. Although the faecal egg counts in 1999 never exceeded 300 epg of the faecal pats derived from the untreated animals, the abnormally dry conditions of this year generated the highest level of overwintered larvae found on herbage in early May 2000, for the 3 years of the study. Overall, biological control with D. flagrans significantly reduced larval availability on herbage, both during and between the grazing seasons, when compared with the untreated control. However, the fungus did not significantly reduce overwintered larvae derived from early season depositions (June and July), particularly when dung pats disappeared within 2 weeks after deposition. Very low number of larvae (<3 per kg dry herbage) were sporadically recovered from grass samples surrounding the ivermectin bolus faecal pats. 相似文献
13.
Dictyocaulus species larvae were obtained from young red deer which had become infected on pastures considered to be carrying the Dictyocaulus species indigenous to the red deer of Scotland. These larvae were cultured to third stage and transmitted to five bovine calves. Five other bovine calves were infected with third stage Dictyocaulus viviparus larvae of bovine origin. Microscopic appearances of both groups of larvae were indistinguishable and their lengths were similar. Results indicated that the Dictyocaulus species derived from deer induced milder though similar clinical and pathological responses in cattle than did the D viviparus derived from cattle. It was concluded that there are strains of different pathogenicity within the species D viviparus, that the deer derived Dictyocaulus species was a strain of D viviparus, and that the hazards to animal health associated with infection by D viviparus in farming systems where red deer and cattle may graze alternately are likely to be acceptable. 相似文献
14.
Fifteen calves, each infected with approximately 3000 third stage larvae, were used to compare the tendencies of two strains of Dictyocaulus viviparus to inhibit at the fifth larval stage and to evaluate the efficacy of ivermectin. There were notable differences between the strains. While greater than 99% of worms developing from infection with an Alpine strain remained inhibited 42 days after infection, only 0-26% of those recovered following infection with a U.K. laboratory strain were arrested. Neither adult nor immature D. viviparus were present in the lungs of animals treated with ivermectin subcutaneously at 200 micrograms/kg body weight 28 days after infection with the Alpine larvae. 相似文献
15.
G Gettinby Q A McKellar K Bairden Y Theodoridis A Whitelaw 《Research in veterinary science》1985,39(1):99-102
The recovery of gastrointestinal nematode infective larvae from herbage collected manually was compared with the recovery from herbage ingested by sheep with oesophageal fistulae, on five occasions during the grazing season. At least three times more larvae were recovered from the oesophageal fistulates than by manual collection. There was no significant variation between the numbers of larvae collected at 09.00, 12.00 and 15.00, nor was there any difference in the distribution of genera recovered by the two methods. The worm burdens of tracer lambs and the larval counts from the fistulated sheep were used to estimate the rate of larval establishment. 相似文献
16.
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
17.
The development of the free-living stages and yields of infective third stage strongyle larvae in faeces from a horse with a mixed natural infection deposited on pasture plots were studied over a 2-year period in a coastal area in tropical north Queensland. Two sets of faecal masses (one exposed to, and the other protected from the action of a natural population of dung beetles) were deposited monthly and after 7 days faecal samples were taken for larval recovery and counts. Hatching and development of the free-living stages occurred in faeces on pasture throughout the year. Development was rapid as infective stages were reached within a week of faecal deposition in all months. Yields of infective larvae were affected by the season and the action of dung beetles on the faecal masses. Highest yields were obtained from both beetle-exposed and protected faeces during winter (June to August) and lowest yields were in spring (September to November). High temperatures in spring and summer resulted in low yields of larvae, however, the dry conditions in spring made this season the most unfavourable period. In autumn and winter the temperatures were never low enough to stop or markedly slow down the rate of development, and allowed the development of large numbers of infective larvae. Dung beetle activity was observed throughout the year, and exposed faeces were usually completely dispersed within 24 h of deposition. This resulted in lower yields of infective larvae from these than from protected faeces. Though larval yields were lower, the actual numbers were still substantial so as to cast doubt on the usefulness of these beetles as biological control agents for equine strongylosis in the dry tropics. 相似文献
18.
In a study originally designed to determine the seasonal origin of the high levels of availability of nematode larvae to cattle in winter and spring, plots were serially contaminated with eggs of Ostertagia ostertagi and Cooperia oncophora by naturally-infected calves at monthly intervals from February 1980 to September 1980. The availability of infective larvae was monitored by monthly pasture sampling and larval recovery. Because of the intervention of a 15 month drought, recoveries of larvae from the pastures were very low until March 1981 (autumn in Australia) when large numbers of larvae appeared on pastures contaminated in the preceding spring. Examination of dry dung pats at that time showed that significant numbers of larvae were present in pats deposited up to a year previously, and particularly in pats deposited in May, August and September. Following the resumption of normal rainfall in May 1981, larval numbers in pats rapidly declined and concentrations of larvae on the pastures increased to extremely high levels. It is suggested that survival of infective larvae in dry dung pats was enhanced by the drought, with implications for control of nematode infections of cattle, particularly in winter rainfall environments. 相似文献
19.
The effect of time of day, season and stratum of herbage and soil on the availability of Haemonchus contortus and Haemonchus placei third-stage larvae (L3) on pasture was assessed. Feces from infected calves and lambs were placed on pasture plots and samples of upper herbage, lower herbage, mat and soil were collected at five intervals per day throughout the daylight hours on 18 sample days over 12 months. Using recovery rate factors derived from a preliminary investigation on the efficacy of larval recovery from each stratum, the data on larval recoveries were analyzed for the effect of season, time and stratum, and their interactions. Significant (P less than 0.05) differences were found for season, stratum and the season-with-stratum interaction for both parasites. No significant differences were detected for larval counts at different times of the day. Larval recoveries of H. contortus were larger throughout the study than those of H. placei. Most H. contortus L3 were recovered in the summer and autumn, and H. placei in the spring and summer. For both parasites, the recoveries of larvae from the upper and lower herbage were larger than those from the mat and soil. The implications of these findings are discussed in terms of control strategies. 相似文献
20.
This study was carried out to examine the survival of infective Ostertagia ostertagi larvae (L(3)) on pasture under different simulated conditions of grazing, i.e. mixed grazing of cattle and nose-ringed sows, or grazing by cattle alone. Standardised pats of cattle faeces containing O. ostertagi eggs were deposited on three types of herbage plots, which were divided into zone 1: faecal pat; zone 2: a circle extending 25cm from the edge of the faecal pat; zone 3: a circle extending 25cm from the edge of zone 2. For "tall herbage" (TH) plots, the herbage in zone 2 was allowed to grow naturally, while the herbage in zone 3 was cut down to 5-7cm fortnightly, imitating a cattle-only pasture. For "short herbage" (SH) plots, the herbage in both zones 2 and 3 were cut down to 5-7cm fortnightly, imitating mixed grazing of cattle and sows. The grass in the "short herbage and scattered faeces" (SH/SF) plots were cut as for SH plots, and the faeces were broken down 3 weeks after deposition and scattered within zone 2, imitating the rooting behaviour of co-grazing sows. Five faecal pats from each plot group were collected on monthly basis, along with the herbage from zones 2 and 3 cut down to the ground. Infective larvae were then recovered from both faeces and herbage. The numbers of L(3) recovered from zone 1 were higher in the TH plots than in the other two groups and, furthermore, the larval counts from SH plots were always higher than from SH/SF plots. The three groups followed a similar pattern during the season regarding numbers of L(3) in zone 2, and no clear patterns between plot types were obtained. The presence of L(3) in zone 3 was almost negligible. Important differences were seen throughout the study from the biological point of view; more L(3) were able to survive in faeces on the TH plots, presumably reflecting a better protection from heat and desiccation compared to those in the other plots. The overall results support the idea that mixed grazing of cattle and pigs favour the reduction of O. ostertagi larval levels in pasture. This reduction is mainly due to the grazing behaviour of pigs, which by grazing up to the very edge of the cattle faeces, will either expose the larvae in faeces to adverse environmental summer conditions or ingest cattle parasite larvae, or both. 相似文献