The impact of daily Duddingtonia flagrans application to lactating ewes on gastrointestinal nematodes infections in their lambs in the Netherlands

Two experiments were performed in 2002 and 2003 to evaluate the effect of biological control of gastrointestinal nematodes in sheep through the daily feeding of 500,000 chlamydospores of Duddingtonia flagrans/kg bodyweight to lactating ewes during the first 9 weeks with their young lambs on pasture. In both experiments four groups of eight ewes and their April-borne lambs were used. They were turned out on four separate plots (plots A) at the beginning of May, moved to similar separate plots after 3 (plots B) and 6 weeks (plots C), respectively, and weaning occurred after 9 weeks. In both experiments, two groups were fed spores daily while the two other groups served as controls. The effect of D. flagrans application was evaluated through faecal egg counts of ewes and lambs, the yield of faecal cultures in ewes, pasture larval counts and worm counts of lambs and tracer lambs. The results demonstrated no effect of D. flagrans application during the first 5 (2002) or 4 (2003) weeks. Subsequently, fungus application strongly reduced the yield in faecal cultures of the ewes. This was, however, not reflected in the pasture larval counts, but lower worm burdens were observed in tracer lambs of 'treated' plots C in 2002 than on those of 'control' plots. In 2003 worm burdens in 'treated' lambs returned to plots B were lower than those of 'control' lambs and a tendency for the same was observed for plots C. However, in all groups, lambs and tracer lambs developed severe haemonchosis.     

Field studies on the biological control of nematode parasites of sheep in the tropics, using the microfungus Duddingtonia flagrans

Long-term field studies were conducted on two government managed small ruminant research farms, located in different geo-climatic regions and approximately 300 km separate from each other, on Peninsula Malaysia. The Infoternak trial (48 weeks) and the Chalok trial (43 weeks) each compared nematode parasite control in separately managed groups of young sheep, either short-term rotationally grazed around a suite of 10 paddocks in addition to receiving a daily supplement of Duddingtonia flagrans spores (Fungus Group); or similar groups of sheep being rotationally grazed alone (Control Group). The prevailing weather conditions at Infoternak farm were of below average rainfall conditions for the most of the trial. As a consequence, only very low worm infections (almost exclusively Haemonchus contortus) were acquired by the 17 sets of tracer lambs that grazed sequentially with the experimental lambs. However on all except 2 occasions in the early part of the trial, the mean tracer worm burdens were significantly lower (P < 0.05) and the experimental lambs grew significantly better (P = 0.054) in the Fungus Group. Rainfall at Chalok farm during the course of the trial was also below average. As a consequence infectivity of pastures was assumed to be relatively low based on faecal egg counts (epg) of the experimental sheep, which following an anthelmintic treatment prior to allocation, remained very low in both treatment groups. Faecal egg counts of undosed replacement lambs in the latter half of the Chalok study, showed a progressive increase in the Control Group to levels exceeding 3000 epg, whereas the Fungus Group remained static at approximately 500 epg. These results show that the deployment of the nematophagous fungus, D. flagrans, can improve the level of parasite control of sheep in the tropics above that which can be achieved by the short-term rotational grazing strategy alone.     

Efficiency of feeding Duddingtonia flagrans chlamydospores to grazing ewes on reducing availability of parasitic nematode larvae on pasture

Gastrointestinal nematodes are of concern in sheep production because of production and economic losses. Control of these nematodes is primarily based on the use of anthelmintic treatment and pasture management. The almost exclusive use of anthelmintic treatment has resulted in development of anthelmintic resistance which has led to the need for other parasite control options to be explored. The blood sucking abomasal parasitic nematode Haemonchus contortus causes severe losses in small ruminant production in the warm, humid sub-tropic and tropics. This study evaluated the effectiveness of a nematode trapping fungus, Duddingtonia flagrans, in reducing availability of parasitic nematode larvae, specifically H. contortus, on pasture. Chlamydospores of D. flagrans were mixed with a supplement feed which was fed daily to a group of crossbred ewes for the duration of the summer grazing season. A control group was fed the same supplement feed without chlamydospores. A reduction in infective larval numbers was observed in fecal cultures of the fungus-fed group. Herbage samples from the pasture grazed by the fungus-fed group also showed a reduction in infective larvae. There were no significant (P > 0.05) differences in overall fecal egg count, packed cell volume or animal weight between fungus-fed and control groups. Tracer animals were placed on the study pastures at the end of the study to assess pasture infectivity. Although tracer animals were only two per group, those that grazed with the fungus-fed group had substantially reduced (96.8%) nematode burdens as compared to those from the control group pasture. Results demonstrated that the fungus did have activity against nematode larvae in the feces which reduced pasture infectivity and subsequently nematode burdens in tracer animals. This study showed that D. flagrans, fed daily to grazing ewes, was an effective biological control agent in reducing a predominantly H. contortus larval population on pasture.     

Evaluation of Duddingtonia flagrans in reducing infective larvae of Haemonchus contortus in feces of sheep.

Consequences of nematode infections due to Haemonchus contortus are a serious constraint for the sheep industry worldwide. Development of anthelmintic resistance and increasing concern about the impact of anthelmintic use dictate the need of alternative control. Such an alternative is using the nematode trapping fungus Duddingtonia flagrans to reduce infective larvae levels on pasture. Two trials were conducted to determine the effect of D. flagrans in reducing infective larvae (predominantly H. contortus) in feces. The first trial determined the dose effect of D. flagrans in reducing infective larvae in feces. Eighteen ewes were dewormed to remove existing infections and randomly assigned to six treatment groups: 5 x 10(4), 1 x 10(5), 2.5 x 10(5), 5 x 10(5), 1 x 10(6) or no (control) spores of D. flagrans per kg of body weight mixed in their feed for 7 days. Fecal samples were collected daily from these and from infected donor ewes. Feces from individual-treated ewes were mixed with equal amounts of donor ewe feces, theoretically approximating oral dose spore concentrations of 2.5 x 10(4), 5 x 10(4), 1.25 x 10(5), 2.5 x 10(5), 5 x 10(5) and no spores, and were cultured. Across dosages and during the 7 days of fungus feeding, percent reduction of infective larvae ranged from 76.6 to 100.0%. The second trial determined the effect of D. flagrans at the dose of 10(5) spores per kg body weight on reducing infective larvae in feces from naturally infected lambs. Twenty lambs were randomly assigned to either treatment or control groups based on fecal egg count. Treatment lambs were fed spores mixed in feed for 7 days. Feces were collected daily and cultured. During the 7 days of fungus feeding, the percent reduction of infective larvae ranged from 82.8 to 99.7%. Results of these trials demonstrated that the nematode trapping fungus D. flagrans was highly effective in reducing infective larvae in sheep feces and should be considered as a biological control agent for integrated nematode control programs.     

Managing anthelmintic resistance: untreated adult ewes as a source of unselected parasites, and their role in reducing parasite populations

AIMS: To test the hypotheses that when untreated adult ewes are rotationally grazed (follow behind) on pastures after lambs receiving routine anthelmintic treatments, the ewes can function as a source of unselected parasites in refugia, capable of slowing the development of anthelmintic resistance, and suppress the build-up of parasites resulting from the development of anthelmintic resistance. METHODS: Firstly, the potential of untreated adult ewes to slow the development of anthelmintic resistance, and to suppress parasite populations under differing levels of anthelmintic efficacy, was investigated using a simulation model. Secondly, a field trial with three replicates of each treatment compared two grazing systems (lambs only vs lambs followed by ewes) and two types of anthelmintic, viz albendazole (ALB), to which resistance was present (faecal nematode egg count reduction (FECR)=57-59%) and ivermectin plus levamisole (IL), to which resistance was absent (FECR=97-99%), in a factorial treatment structure. Parasite populations were monitored using faecal nematode egg counts (FEC), faecal larval cultures, pasture larval sampling, and slaughter of tracer lambs. Animal performance was measured using liveweight, dag score, body condition score, and fleece weights. RESULTS: Model simulations indicated that parasites cycling in the untreated ewes could slow the development of resistance being selected for by the anthelmintic treatments given to lambs and this could occur without a nett increase in larval numbers on pasture. Further, as worm control in the lambs declined with increasing levels of anthelmintic resistance the ewes increasingly functioned as nett removers of parasite larvae, effectively reducing parasite population size. In the field trial, untreated adult ewes contributed to pasture infestations of most parasite species, but not Nematodirus spp. Parasite species on pasture and infecting lambs changed when ewes were present, but larval populations on pasture in the autumn were no greater than when lambs grazed alone. In the presence of anthelmintic resistance, parasite populations were reduced when ewes grazed in rotation with lambs, implicating the ewes as nett removers of parasite challenge. CONCLUSIONS: Untreated adult ewes were a source of unselected genotypes, capable of slowing the development of anthelmintic resistance in most, but not all, parasite species. Further, the potential of adult ewes to remove from pasture more parasite larvae than they contribute through faecal contamination indicates a potentially useful role in suppressing parasite populations, particularly when worm control in lambs is less effective as a result of anthelmintic resistance.     

The effect of Duddingtonia flagrans on trichostrongyle infections of Saanen goats on pasture

Four groups of nine Saanen goat does with a naturally acquired mixed trichostrongylid infection were grazed on four paddocks. Two groups received a daily dose of Duddingtonia flagrans at the rate of 5 x 10(7) chlamydospores per animal per day for the 26-day grazing period. After a 19-day pasture resting period, 20 worm free 12-week-old tracer kids were introduced to the paddocks for 14 days prior to removal for worm burden analysis. Four groups of five does and four kids were drenched then turned out onto the paddocks and faecal egg count (FEC) monitored. The FEC between groups was comparable throughout the initial grazing period. There were significant reductions in number of Teladorsagia circumcincta (54.8%, P=0.004) and Haemonchus contortus (85.0%, P=0.02) worms recovered from tracer animals. FEC of animals subsequently grazing pasture were significantly reduced (P=0.036) with reductions of 44% observed 4 weeks post-turnout. No significant difference was observed after 6 weeks grazing. This trial has demonstrated the potential of D. flagrans to reduce larval numbers on pasture grazed by goats under New Zealand conditions.     

Evaluation of biological control of sheep parasites using Duddingtonia flagrans under commercial farming conditions on the island of Gotland, Sweden

Field trials, conducted over 3 consecutive years, were aimed at assessing farmer opinions of the practicality and effectiveness of using Duddingtonia flagrans to control nematode parasites in their flocks on the Swedish island of Gotland. These trials were also monitored by intensive parasitological investigation. On Gotland, lambing occurs in spring, and around mid-summer (late June), ewes and lambs are moved to saved pastures due to pasture deterioration caused by dry conditions. Weaned lambs are then returned to original lambing pastures in early autumn for finishing. One farm (B) was used for 2001-2003 and a second farm (N) was also used in 2002 and 2003. On each farm, two flocks (each of 20 ewes + twin lambs) were managed separately, namely: fungus group which received a daily supplement + fungal spores from lambing until the summer move (6 weeks) and: control group which received supplement only. For Farm B, the numbers of lambs that were marketed prior to the end of the grazing season, were 13, 18, 19 for the fungus treatment whereas corresponding numbers for the control treatment were 8, 16 and 11 for years 2001, 2002 and 2003, respectively. Final weights of the remaining lambs at the end of each year were also consistently heavier, and the numbers of lambs retained for finishing during winter were less, on the fungus treatment compared with the control treatment. On Farm N, similar results were recorded, with more lambs marketed earlier in the fungus group (25 and 19) compared with the control (19 and 15) in 2002 and 2003, respectively. The weights of the remaining lambs at the end of the trial in 2003 showed a 4.5 kg weight gain advantage of the fungus group compared to the controls. Tracer tests during autumn 2001 on Farm B, showed that Teladorsagia circumcincta plus Trichostrongylus spp. levels were significantly less on the fungus treatment (P=0.018). The summer/autumn of 2002 was one of the driest on record for Gotland. This resulted in very low levels of infective larval availability. But on both farms, T. circumcincta numbers were less on the fungus than on the control paddocks (P=0.048 on Farm B). In 2003 very low numbers of infective larvae were recorded in the autumn tracers for both treatments on both farms. Both farmer co-operators were encouraged with these results and consider that biological control of nematode parasites in their flocks, using D. flagrans, is of practical value.     

Ostertagia circumcincta infection in lambs originating from larvae which survived the winter

Four worm-free lambs were grazed from May to October 1972 on a paddock carrying a low residual infection of O. circumcincta larvae whilst another group grazed a similar paddock carrying a substantial residual larval infection. On the first paddock the lambs acquired low worm burdens of mature worms passing large numbers of eggs, but in spite of this, pasture larval infection remained low. On the second paddock the lambs acquired high worm burdens, a large proportion of which were immature. On this paddock a rise in pasture larval count was observed and this reached a peak in July and August. In spite of the differences in worm burden of the two groups there was no significant difference in weight gain. The mechanism by which the differences in worm burdens may have developed as well as their implications in worm control are discussed.     

Nematodirus battus infection in calves

In studies on the control of parasitic gastroenteritis in calves and sheep, involving an annual rotation of pastures grazed by these host species, it was shown that young cattle could play an important role in the epidemiology of Nematodirus battus, a species usually regarded as a parasite of lambs. Thus, young cattle readily acquired heavy burdens of N battus in spring and the contamination of pastures with eggs from these infections resulted in significant populations of larvae on the herbage, which were infective to both calves and lambs grazed on these pastures in the following year. Although the majority of the N battus eggs hatched in the spring, some hatched in the autumn. The calves developed a strong immunity to N battus during the grazing season as demonstrated by the absence of worms at necropsy in the autumn, despite the presence of infective larvae on the pasture.     

Effect of different times of administration of the nematophagous fungus Duddingtonia flagrans on the transmission of ovine parasitic nematodes on pasture--a plot study

Investigations were made into the timing of administration of Duddingtonia flagrans as a biological control agent against ovine parasitic nematodes including stongylid and Nematodirus spp. Faeces from 3-4 months old male lambs were deposited onto pasture plots that had never been grazed by sheep. The trial was conducted over two consecutive years (1998 and 1999). For both years, the following three plot types were involved: Sim plots had faeces containing nematode eggs and Duddingtonia flagrans spores deposited simultaneously; Post plots had faeces containing nematode eggs followed 2 weeks later by faeces containing D. flagrans spores alone; Control plots had faeces containing only nematode eggs; Prior plots (included in 1999) had faeces containing D. flagrans spores alone followed 2 weeks later by faeces containing nematode eggs. In each year, two deposition periods were involved: July and August in 1998 and June and July in 1999. During the first year pasture samples were collected at 2, 4, 6, 8 and 12 weeks after initial deposition. In 1999, additional samples were collected at 10, 16 and 20 weeks. Larvae were extracted from the pasture samples and counts performed to estimate the number and species of infective third-stage (L(3), larvae) present. The number of third-stage strongylid larvae on pasture was significantly lower on Sim plots compared to the remaining plot types for both years at all deposition times (P<0.001). This was also the case for the number of Nematodirus infective larvae in August deposition plots in 1998 (P<0. 02). There was no significant difference between treatments in both deposition times in 1999 and July deposition plots in 1998 for the Nematodirus data. These results suggest that D. flagrans, if deposited at the same time as parasite eggs prevents transmission of third-stage larvae from the faecal deposit onto pasture, including occasionally Nematodirus species, but does not have an effect on third-stage parasitic nematode larvae in the surrounding soil.     

Environmental Impact on Soil Nematodes Following the Use of the Ivermectin Sustained-release Bolus or the Nematophagous Fungus Duddingtonia flagrans to Control Nematode Parasites of Cattle in Sweden

Management of nematode parasites of grazing livestock is essential, but there is concern about the potential environmental risk from agents used in their control. In this experiment, parasites in young cattle were controlled, using ivermectin boluses or the predacious fungus Duddingtonia flagrans , over 3 years. Treatment differences were sought among the soil nematodes recovered from soil samples collected from the paddocks on which treated animals grazed, and compared with similar samples taken from an untreated control paddock. Analysis of the soil nematode fauna on 21 occasions failed to demonstrate any impact of parasite management on soil nematodes. In 0-22 mm soil total nematode abundance averaged 524 000 m -2 , with 18 nominal taxa and H' diversity 2.41. There were both underlying paddock and year-to-year, climate-related, differences. The results of this trial not only confirm the lack of any adverse environmental impact of D. flagrans , a promising biological control agent, on soil nematodes, but also fail to show any impact arising from the use of ivermectin boluses.     

The Effects of a Controlled-Release Albendazole Capsule (Proftril-Captec) on Parasitism in Grazing Corriedale Ewes in the Nyandarua District of Kenya

Munyua, W.K., Githigia, S.M., Mwangi, D.M., Kimoro, C.O. and Ayuya, J.M., 1997. The effects of a controlled-release albendazole capsule (Profitril-Captec) on parasitism in grazing Corriedale ewes in the Nyandarua district of Kenya. Veterinary Research Communications, 21 (2), 85-99The effects of intraruminal sustained-release capsules (IRSRCs) on parasitism in grazing Corriedale ewes were investigated over a period of 119 days (4 June-30 September 1993) using 40 ewes aged approximately 2 years and randomly divided into two groups of 20 ewes each. Each of the ewes in the treatment group received an IRSRC while the controls were left untreated. The groups were placed on adjacent 2.5-acre paddocks obtained by subdividing a 5.0-acre permanent pasture which had previously been grazed by young untreated sheep, so exposing both groups of ewes to a similar challenge from a contaminated paddock. The faecal egg counts, herbage larval counts and worm burdens of the major gastrointestinal parasites of sheep were significantly reduced by the use of the IRSRC. These parasitological effects were reflected in the increased live weight gains and heavier fleeces of the IRSRC-treated ewes. The control ewes required occasional salvage treatments during the trial period and the herbage on their paddock was heavily contaminated with infected larvae, reflected in the high worm burdens in the control ewes necropsied at the end of the trial and in tracer sheep introduced into the paddocks during the initial (day 30), interim (day 58) and final (day 89) stages of the experiment. Most capsules were exhausted within 95 days of administration, leading to a rise in the count of eggs per gram in the faeces in the treated group towards the end of the study.     

A 3-year field evaluation of pasture rotation and supplementary feeding to control parasite infection in first-season grazing cattle: dynamics of pasture infectivity

A 3-year grazing trial (2002-2004) was conducted on a commercial beef cattle farm in south-central Sweden to assess different methods of parasite control. This paper focuses on the dynamics of the free-living larval stages, whereas data on performance and within-host parasitological variables are presented in a complementary paper. Each year in May, 4 groups of 10 first-season grazing (FSG) steers were turned out on to separate 2ha paddocks and subjected to the following strategies: (1) spring turn-out on to pasture which had been grazed the previous year by second-season grazing (SSG) steers (paddock RT), followed by a move to aftermath (paddock AM) after 10 weeks (mid-July), (2) supplementary feeding with concentrate and hay for 4 weeks following turn-out (paddock FD), set stocked, (3) untreated control (paddock UT), set stocked and (4) anthelmintic treated control (paddock DO), set stocked. All paddocks were assigned a new set of FSG cattle each year whereas the treatments remained the same. Pasture infectivity were monitored partly by two tracer calves that grazed each paddock along with the FSG calves for 3 weeks after turn-out and prior to housing, partly by analysis of herbage samples for infective larvae (L3) that were collected from each paddock at monthly intervals between April and October. The predominant genera found were Cooperia and Ostertagia. Tracers grazing paddock RT overall harboured less worms, and in particular less Ostertagia spp., and tracers grazing paddock AM in mid-July harboured insignificant numbers of nematodes compared to tracers on the FD and UT paddocks. Although total worm counts varied between groups, smaller numbers were generally observed early in the grazing-season (May), compared to close to housing (September) when inhibited early L4 larvae were almost exclusively found. Results observed from herbage samples showed high numbers of L3 in spring before the time of turn-out, compared to around housing. In conclusion, the rotation control strategy showed promising results and provided a turn-out pasture that was 'nematode safe' to FSG cattle the following spring, whereas the feeding strategy failed as applied in this experiment.     

Seasonal Fluctuation an Inhited Development of Populations of Dictyocaulus filaria in Ewes and Lambs

The fluctuation of populations of Dictyocaulus filaria in sheep was studied under field conditions in which animals are housed during the winter and grazed from late spring to autumn. A comparison was made between residual pasture contamination with overwintered larvae, the fecal larval deposition by ewes from June and both of these factors combined as sources of infection for spring born lambs. Ewes and lambs were killed serially over a year and worms were recovered from the lungs and counted. It was found that during the stabling period most of the ewes were carrying moderate numbers of D. filaria. However, while the vast majority of lungworm populations in the winter was inhibited in development at the early fifth larval stage, virtually all worms in the spring were adults. Any one source of infection studied contributed to the acquisition of important burdens of D. filaria by lambs as well as ewes. Worm counts reached peak in all lambs by November and this pointed to only one important Dictyocaulus generation per grazing season. It would also appear that larvae picked up by ewes and lambs as the grazing season advanced had become inhibited in development with the inhibition rate being most marked in autumn.     

Effect of nematophagous fungus Duddingtonia flagrans and energy supplementation on the epidemiology of naturally infected kids

Gastrointestinal (GI) nematode infection is a major constraint for grazing livestock production. The increasing prevalence and severity of anthelmintic-resistant nematodes in many parts of the world has led to a search for non-chemical control options. Under experimental conditions, the nematophagous fungus Duddingtonia flagrans is emerging as an alternative to chemotherapy for the control of GI nematode infection in biological production systems. Also, recent information points to the role of energy nutrition to increase the immune response against GI nematode infection. In this study the effect of D. flagrans and energy supplementation on the epidemiology of GI nematode infections is explored on grazing kids. Four groups of 10, 4-month old goats were turned out on infected pasture in the early spring and allocated to four separate paddocks where they were rotationally grazed for 16 weeks. One of these groups (F) received 0.5 x 10(6) D. flagrans spores/kg BW/d. Another group (S) was supplemented with 100 g barley grain per day. A third group (F+S) received both nematophagous fungi and barley supplement treatments simultaneously while the fourth group (C) was used as a non-treated control. Both nematophagous fungi and barley supplement had a significant effect (P<0.01) on reducing pasture infectivity, faecal egg excretion and worm burdens at slaughter that was particularly evident for Trichostrongylus colubriformis. The combination of both treatments showed a synergistic effect on the control of gastrointestinal nematode infections. At slaughter, the average total post-mortem worm count of the F+S group was reduced by 65% compared with the non-treated control. The results herein show that D. flagrans can act as an efficient biological control agent against kid GI nematode infections on pasture, which could further improve carcass characteristics. While small amounts of energy supplement can also reduce kid infection, the effect of D. flagrans as a biological control agent appeared clearly enhanced both in magnitude and duration by energy supplementation. This has clear implications for grazing animals and provides an efficient method for the practical control of parasitic nematodes in biological production systems.     

Interaction between copper oxide wire particles and Duddingtonia flagrans in lambs

An experiment was completed to determine if copper oxide wire particles (COWP) had any effect on the activity of the nematode-trapping fungus Duddingtonia flagrans in growing lambs. COWP has been used recently as a dewormer in small ruminants because of nematode resistance to anthelmintics. D. flagrans has been used to control free-living stages of parasitic nematodes in livestock. Katahdin and Dorper lambs, 4 months of age, were administered no or 4 g COWP (n=24/dose) in early October 2003. Haemonchus contortus was the predominant gastrointestinal parasite during the trial, which was acquired naturally from pasture. Half the lambs from each COWP group were supplemented with corn/soybean meal with or without D. flagrans for 35 days. Fecal egg counts (FEC) and packed cell volume (PCV) were determined weekly between days 0 (day of COWP administration) and 35. Feces from lambs in each treatment group were pooled and three replicates per group were cultured for 14 days at room temperature. Larvae (L3) were identified and counted per gram of feces cultured. Treatment with COWP was effective in decreasing FEC, which remained low compared with FEC from lambs not treated with COWP. This led to an increase in PCV in these lambs (COWP x day, P<0.001). Number of larvae was decreased in feces from lambs treated with COWP and D. flagrans between days 14 and 35 compared to the other groups of lambs (COWP x D. flagrans x day, P<0.003). Percentage of larvae identified as H. contortus decreased in feces collected from lambs treated with COWP and D. flagrans between days 14 and 28 compared with other treatments (COWP x D. flagrans x day, P<0.05). Other trichostrongyles were present and remained less than 7% in feces collected from control lambs. There was no adverse effect of COWP on the ability of D. flagrans to trap residual larvae after COWP treatment. With fewer eggs being excreted due to the effect of copper on H. contortus, and the additional larval reducing effect exerted by the nematode destroying fungus D. flagrans, the expected result would be a much lower larval challenge on pasture when these two tools are used together in a sustainable control strategy.     

Effects of helminth infection on the pre-weaning production of ewes and lambs: evaluation of pre- and post-lambing drenching and provision of safe lambing pasture

The pre-weaning production of ewes and lambs in spring on pastures grazed during the previous autumn and early winter by either weaner sheep, adult sheep, or cattle was investigated together with estimating the benefits of pre- and post-lambing drenches to ewes. These treatments were compared with one in which parasitism was uncontrolled in ewes lambing on pastures grazed previously by untreated weaner sheep, and another where parasitism was suppressed by 2-weekly drenching of the weaner sheep and also of the ewes and their lambs. Prior grazing by cattle effectively eliminated infection of pastures with intestinal Trichostrongylus and Nematodirus spp, but less so for Ostertagia spp. Worthwhile reductions in contamination were also achieved by grazing by adult sheep compared with grazing by undrenched weaners. Despite differences in the parasitological status of the pastures, there were no indications that pre-weaning growth rates of lambs were affected. However, wool growth in ewes was reduced by 10 to 20% by parasite infection. Wool growth of ewes on pastures grazed by cattle during the pre-experimental period exceeded that on any other treatment, and was significantly greater than that of ewes on pastures grazed by undrenched weaners. There was no production benefit in giving a pre-lambing drench to ewes on plots contaminated by weaners, or in giving the additional post-lambing drench to ewes grazing on plots contaminated by weaners, adult sheep or cattle.     

Production and characterization of a monoclonal antibody against recombinant fatty acid binding protein of Fasciola gigantica

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.     

The epidemiology of nematode infections of sheep

Nematode parasites have been a major factor limiting sheep production in New Zealand for more than 100 years. Twenty-nine species of nematodes were unintentionally introduced with sheep into New Zealand, but it is principally species of Haemonchus, Ostertagia, Trichostrongylus, Nematodirus and Cooperia that are associated with production losses and clinical disease. The seasonal dynamics of nematode infection are the consequence of complex inter-relationships between the sheep, their husbandry and the prevailing climate. The patterns of pasture contamination by nematode eggs and then larvae and the subsequent levels of infection in ewes and lambs are broadly similar throughout New Zealand. Numbers of infective larvae on pasture build up over summer to a peak in autumn/early winter with, in some years, a spring peak derived from the parturient rise in faecal nematode egg counts (FEC), expressed in eggs per gram of faeces (epg), in lactating ewes. The immune capability of lambs is initially low but increases with the magnitude and duration of exposure to infection. Once significant immunity has developed (usually by 10-12 months of age), sheep are capable of markedly restricting parasite infection, except during times of disease, malnutrition or stress. For the effective control of nematode parasites, farmers have come to rely almost exclusively on broad-spectrum anthelmintics. However, issues relating to resistance, residues and eco-toxicity increasingly threaten the sustainability of chemotherapy. In order to maintain present levels of parasite control and productivity in the long term, farmers need to integrate management practices aimed at minimising animal exposure to parasites with reduced reliance on anthelmintics.     

Comparative susceptibility of Romanov and Lacaune sheep to gastrointestinal nematodes and small lungworms

The susceptibility of Romanov and Lacaune sheep to nematode parasites was studied in a permanent flock grazing an extensive pasture. The output of strongyle eggs and protostrongyle larvae was higher in Romanov ewes. Faecal samples of the Romanov ewes more often harboured Nematodirus eggs while the larvae recovered from cultures of these samples contained a higher percentage of Teladorsagia. Romanov tracer lambs had a significantly heavier adult Teladorsagia burden. This higher natural susceptibility of the Romanov breed was confirmed by experimental infections with T. circumcincta and N. spathiger but not with Trichostrongylus colubriformis. In infections with Muellerius capillaris and Protostrongylus rufescens, the worm burdens were similar but parasite fertility (larvae per adult) seemed to be higher in Romanov tracer lambs.