Development and survival ofhaemonchus contortus larvae on pasture in iraq

The survival of Haemonchus contortus infective larvae on pasture and soil was studied over a period of 12 months in the Baghdad area. Infective larvae were found on herbage and soil at all times except in the summer months. During autumn and winter infective larvae in pasture survived for periods of up to 32 weeks. Little larval migration into soil was observed during this study and larvae did not survive for long in the faecal pellets during the summer.     

THE EPIDEMIOLOGY OF EQUINE STRONGYLOSIS IN SOUTHERN QUEENSLAND 1. The Bionomics of the Free-Living Stages in Faeces and on Pasture

SUMMARY Development of the free-living stages of strongylid nematodes of the horse to the infective stage occurred in faeces in all months of the year in southern Queensland, at a rate which depended on the season. Most rapid development to the infective stage occurred in the warmer months, with the hatching of strongyle eggs being completed in 2 days in summer. During the winter, egg hatching continued for over 2 weeks. Larval moults proceeded at a faster rate in summer—all larvae were infective in 7 days during the hottest months, but it was as long as 5 weeks before all were infective in winter. However, even though development was rapid in summer, survival rates varied from 1 to 10%, in contrast to the spring and autumn, when over 80% reached the infective stage. One percent of larvae in faeces survived for up to 20 weeks in autumn and winter, but for only 4 weeks in summer. These results highlight the inadequacy of short-term pasture spelling for all but the hottest months. Infective larvae were found on herbage in all months of the year, but greatest numbers were recovered in spring and early summer, and in autumn and early winter. The relationship of pasture infestation to migration of larvae from Paecal reservoirs in response to rain was clearly shown. Most infective larvae were found within 30 cm of faecal masses, and in fact 89% of all larvae isolated from herbage in this study were found within 15 cm of faeces. Migration of larvae from faeces to herbage occurred with falls of rain as small as 25 mm. Horse faecal masses dried out completely in 6–8 days in summer and in 14–16 days in winter. Strongyle larvae developed to the infective stage in faeces in the absence of rain, although many remained in the pre-infective stage and completed their development when rain fell. This study shows that massive contamination of pastures with the eggs of strongylid nematodes must be prevented in spring and autumn if susceptible young horses are not to be at serious risk.     

Survival of infective Ostertagia ostertagi larvae on pasture plots under different simulated grazing conditions

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.     

Environmental factors influencing the transmission of Haemonchus contortus

Infection with the gastrointestinal nematode Haemonchus contortus causes considerable losses in the sheep industry. In this study, we evaluated the effect that climate has on third-stage larvae (L3) of H. contortus in terms of their migration from sheep feces to Brachiaria decumbens grass, as well as their distribution among the forage plants. Fecal samples containing H. contortus L3 was deposited on the soil among the herbage at an initial height of 30 cm. Sample collection began 24h after contamination and was performed on alternate days over 13 days. The L3 were recovered and quantified in three strata (heights) of grass (0-10 cm, 10-20 cm and >20 cm) as well as in the remaining feces and a superficial layer of soil, collected from beneath the feces. In order to obtain results under different environmental conditions, fecal samples containing H. contortus L3 were deposited on pasture in January (summer), in April (autumn), and July (winter). In all of the periods, the L3 were able to migrate from the feces to the herbage. However, rains, accompanied by high relative humidity and high temperatures, apparently favored migration. The highest L3 recovery rate in the pasture was in the summer observation period, which had the highest number of days with measurable precipitation, high relative humidity (>68.2%), and the highest temperatures at the soil level (minimum and maximum means of 19°C and 42°C, respectively). Under those conditions, larvae began to reach the upper stratum of the grass (>20 cm) by 24h after the deposition of fecal matter, the number of larvae having reached that stratum peaking at seven days after deposition. In the autumn observation period, there was no rainfall in the first five days post-contamination. During that period, high numbers of larvae were found in the fecal samples demonstrating that feces can act as a reservoir of larvae in the absence of rain. Except for two days in the summer observation period, when most of the L3 were recovered from the tops of blades of grass, L3 where located predominantly at the base of the herbage. In conclusion, rainfall favors the migration of L3 from feces to herbage. In addition, larval migration up and along blades of grass can occur relatively rapidly when the temperature is high.     

The origin and overwintering survival of the free living stages of cattle parasites in Sweden

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.     

Observations on the free-living stages of cattle gastrointestinal nematodes

A 4-year study on the free-living stages of cattle gastrointestinal nematodes was conducted to determine (a) the development time from egg to infective larvae (L3) inside the faecal pats, (b) the pasture infectivity levels over time, and (c) the survival of L3 on pasture. Naturally infected calves were allowed to contaminate 16 plots on monthly basis. Weekly monitoring of eggs per gram of faeces (epg) values and faecal cultures from these animals provided data for the contamination patterns and the relative nematode population composition. At the same time, faecal pats were shaped and deposited monthly onto herbage and sampled weekly to determine the development time from egg to L3. Herbage samples were collected fortnightly over a 16-month period after deposition to evaluate the pasture larval infectivity and survival of L3 over time. The development time from egg to L3 was 1-2 weeks in summer, 3-5 weeks in autumn, 4-6 weeks in winter, and 1-4 weeks in spring. The levels of contamination and pasture infectivity showed a clear seasonality during autumn-winter and spring, whilst a high mortality of larvae on pasture occurred in summer. Ostertagia spp., Cooperia spp. and Trichostrongylus spp. were predominant and a survival of L3 on pasture over a 1-year period was recorded in this study.     

Epidemiology of Dictyocaulus viviparus in Louisiana (U.S.A.)

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.     

Migration of gastrointestinal nematode larvae from cattle faecal pats onto grazable herbage

This study investigated the effect of successive harvests of grazable herbage around cattle faecal pats on the population dynamics of infective gastrointestinal nematode larvae (L(3)). Faecal material, collected from naturally infected calves, was deposited as pats during summer, autumn and winter on three different topographical aspects within a moist, temperate region of New Zealand. Herbage was harvested four times (22-248 days) from around the faecal pats to a height of 2cm in three radial zones (0-20cm, 20-35cm and 35-45cm from the centre of the faecal pat) and L(3) extracted. Harvest date was determined by herbage mass to simulate grazing events. L(3) extracted from herbage were predominantly Cooperia spp. More L(3) were recovered from faeces deposited in summer and autumn, than those deposited during winter. L(3) concentration on herbage was highest (P<0.001) in the zone nearest the pat for all except the fourth harvest. Mean concentrations of L(3) on herbage were 11,447, 3154, 337 and 102 L(3)/kg dry matter herbage, for the four successive harvests, respectively. Microclimate differences as affected by aspect had a marked effect on herbage growth, but did not significantly affect L(3) concentration on herbage. In this study, L(3) remained aggregated close to the faecal pats they emerged from even after two successive harvests and significant rainfall. Successive harvests simulated the effect of repeated grazing events by a non-infective stock class. Two such grazings and the associated time, reduced L(3) presence on grazable herbage to <3% of the original population. Grazing strategies to generate clean pasture for vulnerable cattle are discussed in relation to these results.     

Seasonal translation of equine strongyle infective larvae to herbage in tropical Australia

Longevity in faeces, migration to and survival on herbage of mixed strongyle infective larvae (approximately 70% cyathostomes: 30% large strongyles) from experimentally deposited horse faeces was studied in the dry tropical region of North Queensland for up to 2 years. Larvae were recovered from faeces deposited during hot dry weather for a maximum of 12 weeks, up to 32 weeks in cool conditions, but less than 8 weeks in hot wet summer. Translation to herbage was mainly limited to the hot wet season (December-March), except when unseasonal winter rainfall of 40-50 mm per month in July and August allowed some additional migration. Survival on pasture was estimated at 2-4 weeks in the summer wet season and 8-12 weeks in the autumn-winter dry season (April-August). Hot dry spring weather (pre-wet season) was the most unfavourable for larval development, migration and survival. Peak counts of up to 60,000 larvae kg-1 dry herbage were recorded. The seasonal nature of pasture contamination allowed the development of rational anthelmintic control programs based on larval ecology.     

Studies on the epidemiology of bovine parasitic bronchitis.

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.     

Development and survival of Haemonchus contortus larvae on pasture at Vom,Plateau State,Nigeria

The development and survival of the eggs of Haemonchus contortus on pasture at Vom were studied by depositing faecal pellets on grass plots over a period of 12 months. Development and survival to the infective larvae occurred throughout the study except during the dry season months of December to April. More infective larvae were recovered from the herbage in June, July and August than in other months. The survival time of the infective larvae ranged from 2 weeks in October to 10 weeks in June, July and August. Rainfall was the most important epizootiological factor influencing the development and survival of the infective larvae. Temperature was not a limiting factor.     

The origin of winter populations of infective larvae of nematode parasites of cattle in a Mediterranean-type climatic environment

An experiment to determine the origin of populations of infective larvae of cattle nematode parasites on pasture during winter was conducted in south-west Western Australia. Six pasture plots were contaminated with worm eggs by grazing worm-infected cattle for periods of a month during summer and autumn. Each plot was contaminated at a different time from the rest. The levels of infective larvae were determined by counting the worm burdens of tracer calves which test-grazed the plots the following winter.Tracer calves which grazed the plots contaminated during summer acquired few worms, whereas those that grazed the plots contaminated during autumn acquired many worms. It was concluded that the hot, dry conditions prevailing during summer and early autumn prevented the development of eggs or survival of larvae in dung pats or free on pasture. In this environment, a programme of worm control which relied on administration of anthelmintic to grazing cattle to prevent autumn contamination of pasture would be most likely to succeed if the first treatment was given in early autumn.     

Seasonal translation of infective larvae of gastrointestinal nematodes of cattle and the effect of Duddingtonia flagrans: a 3-year pilot study

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.     

Epidemiology of Nematodirus species infections of sheep in a subarctic climate: development and persistence of larvae on herbage

As part of a study on the epidemiology of Nematodirus species of sheep in subarctic Greenland, the development and persistence of eggs and larvae were investigated by experimentally contaminating plots of pasture with infected faeces and by placing tubes containing a suspension of eggs on to or into the soil. Despite low ambient temperatures, infective larvae appeared within a month during the summer. The greatest numbers of larvae were recovered from herbage in August and September. Eggs did not develop synchronously as development beyond the morula stage could be delayed for up to two years. Larvae were found on herbage for up to 37 months after faecal deposition. In the sheep rearing area of Greenland, therefore, Nematodirus species larvae can be present on herbage throughout the whole summer but peak numbers occur late in the grazing season.     

Observations on the epidemiology of Dictyocaulus viviparus in north west England

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.     

Development and survival of Haemonchus contortus isolated from sheep on a pasture at Bunia (Itiri, Zaire)]

Development and survival of Haemonchus contortus larvae were studied from December 1987 to November 1988 during three different periods (dry season, first and second rainy seasons) on an experimentally infected pasture at Bunia (Ituri, Za?re). Whatever the season, eggs developed into infective larvae within six days and the largest number of larvae on the herbage occurred between the 12th and the 18th day post deposition. However, the two rainy seasons were the most favourable for transmission because of the high number of larvae on the pasture and the increased survival of these larvae after 4 weeks.     

Seasonal availability of gastrointestinal nematode larvae to cattle on pasture in the central highlands of Kenya

The type and level of infective strongylid nematode larvae on pasture were monitored fortnightly from July 1995 to June 1996 in the central highlands of Kenya. The number of larvae on pasture was moderate, reaching > 1,200 kg(-1) dry matter of grass during the period of, and soon after, the rains, and remained low in the dry seasons. The number of larvae on pasture was directly related to the rain-fall pattern which was found to be the most important factor for the development of eggs and free-living stages. Haemonchus was the predominant genus, followed in decreasing order by Trichostrongylus, Cooperia, Oesophagostomum and Bunostomum. The mean total adult worm burdens of tracer calves released at monthly intervals were related to the levels of herbage larvae and there was a positive correlation between faecal worm egg counts and worm burdens (r = 0.58) during the study period. These results indicate that a reduction in the contamination of pasture with nematode eggs before the rains could result in pastures carrying fewer larvae and thus form the basis of effective worm control programmes for cattle.     

Strategic use of anthelmintics to prevent parasitic gastroenteritis in cow-calf herds in California

On the basis of the hypothesis that the peak numbers of infective nematode third-stage larvae (L3) on herbage in winter months results from fall contamination of pastures, 2 methods to reduce fall contamination were tested. In trial 1, morantal sustained-release boluses were administered to 15 fall-calving cows on Sept 7, 1982. Fifteen untreated cows (controls) were placed on separate pastures. Numbers of L3 on herbage during the winter and spring were assessed by use of worm-free tracer calves. In trial 2, 19 cattle due to calve in the fall were administered 200 micrograms of invermectin/kg of body weight, SC, on Sept 2, 1983. Also, 17 cattle similarly were given a placebo injection and served as control animals. Treated cattle were placed on the pasture used by control cattle in trial 1 and control cattle on the pasture used by treated cattle in trial 1. Worm-free tracer calves were again used to assess numbers of L3 on herbage. In trial 1, tracer calves grazing the control animal pasture from January 14 to 28 acquired 37 times as many nematodes as did those grazing the treated animal pasture. In trial 2, the greatest difference observed was a 10-fold increase of nematodes in calves grazing control animal pastures, compared with worm numbers in tracer calves grazing the treated animal pasture.     

Development and spatial distribution of the free-living stages of Teladorsagia circumcincta and Trichostrongylus colubriformis on pasture: A pilot study

Abstract

AIMS: To measure the development of Teladorsagia (=Ostertagia) circumcincta and Trichostrongylus colubriformis eggs to third-stage infective larvae (L3) at different times of the year. Also, to measure the spatial distribution of L3 across herbage, soil and faeces, in order to assess whether spatial issues could be important in larval dynamics on pasture.

METHODS: Field plots were contaminated with sheep faeces containing approximately 20,000 eggs of each of T. circumcincta and T. colubriformis on five separate occasions, viz 01 December 1996 (summer), 18 March 1998 (autumn), 17 June 1998 (winter), 15 October 1998 (spring), and 23 July 1999 (winter). Replicate plots (n=10) were harvested at intervals for up to 12 months after deposition of faeces, and the number and distribution of L3 were measured. Larvae were sampled from faeces (where these remained), herbage, and three soil zones to a depth of 145 mm.

RESULTS: There were large differences between contamination dates in the percentage of eggs that developed to L3. For both species the highest percentage development was for eggs deposited in December (7.8% and 25.9% for T. circumcincta and T. colubriformis, respectively) and the lowest for June (0.4% and 0.03% T. circumcincta and T. colubriformis, respectively). Development in winter was often delayed, and this was always associated with a low yield of larvae, probably due to compounding mortalities associated with long periods of exposure to low temperatures.

The relative distribution of L3 present on herbage, in faeces or in the soil varied between sampling times. However, overall the most L3 were recovered from soil (74% and 66% for T.circumcincta and T. colubriformis, respectively, averaged over all samples), and the lowest recoveries were from the herbage.

CONCLUSIONS: Although the data are limited, the results indicated that the highest percentage of eggs developed to infective larvae in summer and only minimal development occurred in winter. The data do not support the view that substantial contamination of pastures with sheep parasites occurs over winter. Large numbers of larvae were recovered from soil, which indicates that, assuming they can subsequently migrate onto herbage, soil is a potentially important reservoir ofinfective larvae in New Zealand. Therefore, the spatial distribution of L3 on pasture may affect both the dynamics and transmission of parasite populations. Further work on both these issues is warranted.     

Recirculating elutriator for extracting gastrointestinal nematode larvae from pasture herbage samples

Gastrointestinal nematode (GIN) parasites present an important limitation to ruminant production worldwide. Methods for quantifying infective larvae of GIN on pastures are generally tedious, time-consuming, and require bulky equipment set-ups. This limitation to expedient data collection is a bottleneck in development of pasture management practices that might reduce pasture infectivity. We modified a soil elutriator concept for extracting GIN larvae from fresh herbage samples. Elutriators were constructed from readily available parts and compared to the Baermann funnel sedimentation method for larvae extraction. More samples could be extracted per day in the elutriator than in a Baermann unit with extraction times of 8 min versus 24h, respectively. Accuracy, measured as maximum recovery of larvae seeded onto herbage samples, did not differ between extraction methods (62.3 vs. 69.8% for elutriator and Baermann, respectively, P>0.05). Larvae recovery from herbage in elutriators showed a strong log(e) relationship with extraction time (r(2)>0.98), which will allow development of accurate correction factors for specific herbages to predict total larvae densities at extraction times less than those needed for maximum recovery. An extraction time of 8 min per sample gave the best compromise of speed, accuracy, and precision as measured by regression confidence bands and root mean square error of analysis of variance. Precision of the elutriator extraction for pasture samples was comparable to published methods and was not affected by forage species or canopy strata. The elutriator method was sensitive enough to detect differences in larvae density as small as 8 larvae g(-1) DM among pasture treatments. Elutriators extracted nematode larvae from herbage samples with accuracy and precision similar to existing methods, but did it much faster. Elutriation shows promise as a rapid method for extracting infective GIN larvae from pasture herbage.