Abomasal Worm Counts Research Articles

114 The efficacy of a natural fungus (Duddingtonia flagrans) in reducing gastrointestinal nematode indicators in lambs

Abstract Sustainable and profitable small ruminant production in the US is affected by infections with gastrointestinal nematodes (GIN), especially the blood sucking GIN, Haemonchus contortus. The overuse and misuse of available drug classes has led to multi-drug resistant GIN that pose significant challenges to parasite control on many farms. The objective of this study was to evaluate the effectiveness of a natural fungus (Duddingtonia flagrans; Bioworma, International Animal Health) in reducing GIN larval counts and other GIN indicators in hair sheep wethers. Eighteen St. Croix (n = 9) and Barbados Blackbelly (n = 9) wethers (227 ± 1.4 days of age and 29.7 ± 0.6 kg BW) were dewormed (d 0) with a combination of levamisol (Prohibit; 8 mg/kg BW) moxidectin (Cydectin; 0.2 mg/kg BW) and albendazole (Valbazen; 7.5 mg/kg BW) prior to the start of feeding according to the manufacturer’s recommendations for feeding BioWorma. At this time, lambs were separated into two treatment groups (n = 9/group), split into 3 replications per treatment group and placed on six pasture paddocks (0.06 ha; n = 3 per paddock) after accounting for breed, initial fecal egg count (FEC) and BW. Lambs were then fed daily either a grain supplement ration (corn and soybean meal) with Livamol with Bioworma (LIV) or without (CON) at 2% of their BW for 98 d. LIV was added to the ration based on total lamb BW/paddock. To evaluate the effect of LIV treatment, BW and body condition scores (BCS) were recorded every 2 wk for 98 d. Blood and fecal samples were also collected for determination of packed cell volume (PCV) and FEC. Pooled treatment group feces (d 0 – 98) were collected and cultured to determine GIN genera. A subset of animals/treatment (n = 3) will be harvested to determine abomasal worm counts. Data were analyzed using repeated measures in a mixed model, and FEC were log transformed before analysis. Following deworming (d 0), FEC were reduced by 100% by d 14. There was a mixed population of GIN at the start of the study (averaging 54%, 42%, 1.2% and 1.8% for H. contortus, Tricostrongylus spp., Oesphagostomum spp. and Nematodirus spp., respectively). LIV with Bioworma supplementation had no impact on BW, BCS, PCV or FEC in this study averaging 34.2 ± 0.3 kg, 2.5 ± 0.04, 34.7 ± 0.5% and 150.9 eggs per gram, respectively. Under the conditions of this study, Bioworma® supplementation had no influence on GIN indicators measured up to 100 d of grazing. This research will be continued during subsequent grazing seasons to determine the effect of continued supplementation on lamb parasite load and performance as well as pasture infestation levels.

Antibody response and abomasal histopathology of lambs with haemonchosis during supplementation with medicinal plants and organic selenium

We evaluated the effects of dietary supplementation with medicinal plants (Herbmix) or organic selenium (Selplex) on the immune responses and histopathology of lambs infected with Haemonchus contortus. Twenty-seven lambs were infected and reinfected with approximately 11,000 third-stage larvae of H. contortus during the experiment (on days 0, 49 and 77). Lambs were divided into two supplemented experimental groups (Herbmix and Selplex) and unsupplemented group (Control). The abomasal worm counts at necropsy on day 119 were lower for Herbmix (4230) and Selplex group (3220) than to the Control (6613) which resulted in 51.3% and 36.0% of reduction, respectively. The mean length of adult female worms was in the order Control > Herbmix > Selplex (2.1, 2.08, and 2.01 cm, respectively). The specific IgG response against adults was significantly affected by time (P < 0.001). Serum-specific and total mucus levels of IgA in the Herbmix group were highest on day 15. Mean levels of serum IgM against adults were influenced by treatment (P = 0.048) and time (P < 0.001). The Herbmix group had strong local inflammation in the abomasal tissue, with the formation of lymphoid aggregates and the infiltration of immune cells, but the tissues of the Selplex group had higher numbers of eosinophils, globule leukocytes, and plasma cells. The lymph nodes of each animal had reactive follicular hyperplasia due to the infection. Dietary nutritional supplementation with a mixture of medicinal plants or organic selenium could improve local immune responses and thus enhance the resistance of animals to this parasitic infection.

Natural chemotherapeutic alternatives for controlling of haemonchosis in sheep

BackgroundParallel in vitro and in vivo experiments were designed to evaluate promising chemotherapeutic alternatives for controlling haemonchosis in ruminants. In vitro anthelmintic activities (egg hatch test – EHT; larval development test – LDT) of aqueous and methanolic herbal extracts Mix1 and Mix2 were investigated. The in vivo effects of dietary supplementation with Mix1 and Mix2 on the parasitological status, inflammatory response, antioxidant parameters and microbial community of the lambs infected experimentally with Haemonchus contortus were investigated. Lambs were divided into four groups for the in vivo study: uninfected control lambs (C), infected lambs (I), infected lambs supplemented with Mix1 (I + Mix1) and infected lambs supplemented with Mix2 (I + Mix2). The experimental period was 70 days.ResultsThe number of eggs per gram (EPG) of feces was quantified 22, 30, 37, 44, 51, 58, 65 and 70 days post-infection, and mean abomasal worm counts were assessed 70 days post-infection. Quantitative analyses identified 57.3 and 22.2 mg/g phenolic acids, 41.5 and 29.5 mg/g flavonoids and 1.4 and 1.33 mg/g protoberberine-type alkaloids in Mix1 and Mix2, respectively. The methanolic extracts of the herbal mixtures in both in vitro tests had higher anthelmintic effects (P < 0.01) than the aqueous extracts, but the effects did not differ significantly between Mix1 and Mix2 (P > 0.05). I + Mix1 and I + Mix2 lowered mean EPGs between 44 and 70 d by 58.1 and 51.6%, respectively. The level of IgG antibodies against H. contortus increased significantly after infection in each infected group.ConclusionThese results represent the first monitoring of the in vitro anthelmintic effects of herbal mixtures on H. contortus. The in vivo experiment indicated that the anthelmintic effect was not sufficient for the elimination of parasites, but this herbal treatment may affect the host over a longer term, reducing the parasitic infection in the host.

Peanut skin in dietalters average daily gain, ruminal and blood metabolites, and carcass traits associated with Haemonchus contortus infection in meat goats.

The aim of this study was to determine the effects of tannin-rich peanut skin (PS) supplementation on growth performance, ruminal and blood metabolites, and carcass traits associated with internal parasite infection in meat goats under confined conditions. Twenty-one Kiko crossbred male goats were blocked by body weight (BW) and randomly assigned to one of 3 treatment groups. Experimental diets contained different levels of peanut (Arachis hypogaea) skin replacing alfalfa (Medicago sativa) pellets (ALP) in a control diet. Experimental treatments included: 30% ALP (control), 15% PS and 15% ALP, and 30% PS. Peanut skin was incorporated in the grain mix portion of the diets. Animals were fed once daily, and the intake was adjusted every 3 to 4 d. Each animal was each artificially infected with 5,000 larvae of the 3rd stage of barber's pole worm (Haemonchus contortus). Body weights, dry matter intake (DMI), and fecal samples for fecal egg counts (FEC) were taken at d 0, 12, 23, and 41. Rumen fluid and blood samples were collected at d 45. The performance period lasted 45 d and at the completion of the study, goats were harvested, and carcass characteristics, abomasal worm counts were measured. The results showed that DMI, BW, carcass traits, and meat color were not affected by PS supplementation, whereas average daily gain (ADG, P < 0.01), blood glucose (P < 0.001), phosphorus (P < 0.05), and cholesterol levels (P < 0.001) significantly increased with increasing levels of PS supplementation. There was a linear (P < 0.01) reduction in rumen acetate to propionate ratio, ammonia-nitrogen, FEC, and H. contortus worm counts, with increasing levels of PS supplementation. This study shows that PS supplementation up to 30% of the diet can improve ADG and rumen fermentation while reducing gastrointestinal parasite infection in meat goats.

Effects of herbal nutraceuticals and/or zinc against Haemonchus contortus in lambs experimentally infected

BackgroundThe gastrointestinal parasitic nematode Haemonchus contortus is a pathogenic organism resistant to several anthelmintics. This study assessed the efficacy of a medicinal herbal mixture (Herbmix) and organic zinc, as an essential trace element for the proper functioning of both unspecific and specific immune defensive mechanisms, against experimental infections with H. contortus in lambs. All lambs were infected orally with approximately 5000 third-stage larvae of a strain of H. contortus susceptible to anthelmintics (MHco1). Twenty-four female lambs 3–4 months of age were divided into four groups: unsupplemented animals (control), animals supplemented with Herbmix (Hmix), animals supplemented with organic zinc (Zn) and animals supplemented with Herbmix and organic zinc (Hmix+Zn). Eggs per gram (EPG) of faeces were quantified 20, 28, 35, 42, 49, 56, 62 and 70 d post-infection and mean abomasal worm counts were assessed 70 d post-infection. Samples of blood were collected from each animal 7, 35, 49 and 70 d post-infection.ResultsQuantitative analyses of the bioactive compounds in Herbmix identified three main groups: flavonoids (9964.7 μg/g), diterpenes (4886.1 μg/g) and phenolic acids (3549.2 μg/g). Egg counts in the lambs treated with Hmix, Zn and Hmix+Zn decreased after 49 d. The EPGs in the Zn and Hmix+Zn groups were significantly lower on day 56 (P < 0.05 and P < 0.01, respectively), and the EPGs and mean worm counts were significantly lower on day 70 in all supplemented groups (P < 0.05 and P < 0.01). Hemograms of complete red blood cells of each animal identified clinical signs of haemonchosis after day 35. Serum calprotectin concentrations and IgA levels were significantly affected by treatment. The treatment influenced serum malondialdehyde concentrations (P < 0.05) and sulfhydryl groups (P < 0.01) of antioxidant status. The mineral status was unaltered in all lambs.ConclusionA direct anthelmintic impact on the viability of nematodes was not fully demonstrated, but the treatments with herbal nutraceuticals and zinc likely indirectly contributed to the increase in the resistance of the lambs to nematode infection.

A Novel Application of an Anthelmintic Mixture for Use against Gastrointestinal Parasites of Red Deer (Cervus elaphus).

A mixture of proprietary anthelmintics delivering 0.5 mg/kg moxidectin, 9.06 mg/kg oxfendazole, 15 mg/kg levamisole, and 0.08 mg/kg selenium on bodyweight basis per os to red deer is investigated. On a deer farm with a history of parasite problems, six weaner red deer were treated orally with a 50/50 mixture of Exodus Pour-On and Oxfen C Plus (Ex/Ox) at a dose rate of 1 ml/5 kg bodyweight. Six herd mates were untreated. Eleven days later abomasal worm counts for the untreated deer revealed an arithmetic mean burden of 2,566 Ostertagia-type worms and 300 Trichostrongylus axei. No worms were detected in the abomasa of the treated group. Six yearling red deer were treated with the Ex/Ox combination and sent 39 days later to a slaughter plant where tissue samples were collected for residue analysis. Moxidectin was the only anthelmintic compound to show residues and the concentrations measured were well below maximum residue limits. Laboratory analysis of the Ex/Ox product after six-week storage at ambient temperature indicated good physical and chemical stability. These investigations support the hypothesis that the Ex/Ox combination can be an effective and practical anthelmintic option for use in red deer against a background of widespread gastrointestinal parasite resistance to the registered alternatives.

Tropical plant supplementation effects on the performance and parasite burden of goats.

ObjectiveExamine the effects of supplementing bahiagrass hay (BG) with potentially anthelmintic quantities of hays of perennial peanut (PEA) or sericea lespedeza (LES) or seeds of velvet bean (Mucuna pruriens L.; MUC) or papaya (PAP) on the intake and nutritive value (Experiment 1), and the performance and parasite burden (Experiment 2) of goats.MethodsIn Experiment 1, 38 male goats (27.4±5.7 kg body weight) were randomly assigned to each of 5 treatments: i) BG alone and BG plus; ii) PEA; iii) LES; iv) MUC; and v) PAP. Goats were fed for ad libitum consumption and adapted to the diets for 14 d followed by 7 d of measurement. The PEA, LES, MUC (50%, 50%, and 10% of the diet dry matter [DM], respectively), and PAP (forced-fed at 10 g/d) were fed at rates that would elicit anthelmintic effects. In Experiment 2, goats remained in the same treatments but were allocated to 15 pens (3 pens per treatment) from d 22 to 63. All goats were infected with parasites by grazing an infected bahiagrass pasture from 0800 to 1500 h daily and then returned to the pens.ResultsDry matter intake tended to be greater in goats fed PEA and LES than those fed BG (757 and 745 vs 612 g/d, respectively). Digestibility of DM (59.5% vs 54.9%) and organic matter (60.8% vs 56.0%) were greater in goats fed MUC vs BG, respectively. In Experiment 2, feeding PAP, LES, and PEA to goats reduced nematode fecal egg counts by 72%, 52%, and 32%, reduced abomasal adult worm counts by 78%, 52%, and 42%, and decreased plasma haptoglobin concentrations by 42%, 40%, and 45% relative to feeding BG alone, respectively.ConclusionSupplementation with PEA, LES, and PAP decreased the parasite burden of goats but did not increase their performance. PAP was the most effective anthelmintic supplement.

Variable exon usage of differentially-expressed genes associated with resistance of sheep to Teladorsagia circumcincta

The resistance and susceptibility of sheep to the common abomasal nematode parasite, Teladorsagia circumcincta is strongly associated with the differential polarization of the immune response. Resistant animals control larval colonization by the production of a protective antibody response regulated by Th2 T cells. Susceptible sheep respond to infection by developing an inflammatory Th1/Th17 response that fails to control infection. Previous microarray analysis identified genes associated with T cell polarization that were differentially expressed between the resistant and susceptible sheep. RT-qPCR confirmed the microarray data for ALOX15 and IL13. Both ALOX15 exon 9 and IL13 exon 4 were significantly increased in resistant animals and copy number RT-qPCR showed that expression levels of these exons were significantly negatively correlated with quantitative phenotypic traits, including abomasal worm counts and faecal egg counts. Sequencing of the intronic regions 5′ to these genes failed to identify any potential genetic links to differential exon usage.

Gastro-intestinal nematodes of goats reared under communal small scale farming conditions in Botswana

The study was carried out in goats reared under communal small scale farming conditions near Gaborone, Botswana, to evaluate two sample preparation methods for McMaster egg counting technique, determine worm egg counts (WEC), identify nematode genera by larval culture, and determine abomasal and intestinal worm counts. Goat faecal samples (n = 30) were collected, split, and paired for preparation by either the simple method or the standard method and WEC was performed using the McMaster technique. The simple method resulted in significantly higher WEC than the standard method (p =0.04). The WEC of a cohort of goats from Modipane communal small scale farmers (n = 30) was found to be 995±229 eggs per gram (EPG). Larval culture of Modipane herds identified Trichostrongylus spp at 86 percent and Haemonchus spp, Ostertagia spp, Oesophagostomum spp, and Chabertia spp all occurring at less than 5 % each. Abomasal worm counts of two separate groups of goats at slaughter were found to be 110 ± 28 Haemonchus spp (n = 21) and 277 ± 129 Haemonchus spp (n = 30) in goats with WEC of 836 ± 236 EPG and 642 ± 120 EPG respectively. Intestinal worms were not found in the group (n = 30) that was tested for them. It was concluded that there is a significant worm burden among goats reared under communal small scale farming conditions in Botswana. Keywords: Nematodes, McMaster technique, goats, abomasal worm count, worm burden

Nutrient partitioning of Merino sheep divergently selected for genetic difference in resistance to Haemonchus contortus

This research was designed to determine if divergent genetic selection for resistance to Haemonchus contortus had produced correlated changes in the metabolism of amino-nitrogen in the absence or presence of H. contortus infection. Partitioning of amino acid-nitrogen between tissues was determined in 42 Merino weaner wethers from the CSIRO Haemonchus selection flock, increased resistance to Haemonchus (IRH), decreased resistance to Haemonchus (DRH) and random bred control (C) selection lines. Weaner wethers were fed a restricted diet (9.8MJME/kgDM, 86gMP/kgDM) calculated to allow a gain of 125g/d bodyweight throughout the experimental period and were either worm-free or trickle infected with H. contortus. At 8 weeks post-infection animals were injected with 15N-labelled duckweed directly into the abomasums. Animals were euthanased at either 6 or 24h after the injection to collect tissue samples for calculation of percentage recovery of 15N in tissue and to determine abomasal worm counts. Worm egg count and worm counts at week 8 of infection were lower in animals from the IRH line. IRH animals had a lower N digestibility, increased oxidation of amino acids and lower N balance but whole-body protein flux was unaffected. Amino acid metabolism, as assessed from 15N uptake and excretion in response to H. contortus infection, differed between IRH and DRH animals. In IRH animals a greater recovery of 15N in the thymus and abomasal smooth muscle indicated greater partitioning of amino acids towards the immune response. In DRH animals an increased recovery of 15N in the spleen, in response to infection, may be a possible adaptation. It appears that divergent selection for worm egg count has not been associated with symmetrical changes in amino acid metabolism, but rather the partitioning of amino acid resources reflects each selection line's independent response to infection.

Vaccination of lambs against Haemonchus contortus infection with a somatic protein (Hc23) from adult helminths

A somatic protein from adult Haemonchus contortus (Hc23), the most abundant component in a low molecular weight fraction with known immunizing effect against experimental haemonchosis, has been purified by immunochromatography. The immunoprophylactic value of Hc23 was tested in groups of 5–6months old Assaf lambs using Al(OH)3 or Escherichia coli lipopolysaccharide+inactivated Propionibacterium acnes as adjuvant and the results compared with uninfected control, uninfected and challenged or infected and challenged lambs. Immunization with Hc23 in either adjuvant elicited significant reductions in fecal egg counts after challenge with 15,000 L3s (70.67%–85.64%, respectively) and reduced (67.1% and 86%) abomasal worm counts (45days post-challenge). Immunized lambs displayed higher peripheral eosinophil counts, were less anaemic and had weight gains than challenged controls. The results suggest that the Hc23 antigen can induce a partially protective response against haemonchosis in lambs.

Investigation of sainfoin (Onobrychis viciifolia) cultivar differences on nitrogen balance and fecal egg count in artificially infected lambs1

Research in ruminant nutrition and helminth control with forages, which contain condensed tannins (CT), suggests that varying responses may depend not only on CT concentration but also on CT composition. An experiment was designed to test this by feeding 2 dried sainfoin cultivars (Visnovsky and Perly), which differed in CT properties, to lambs that were artificially infected with the abomasal blood-sucking nematode Haemonchus contortus. Twenty-four infected lambs received 1 of these 2 cultivars; the feeds were either untreated or treated with the CT-binding polyethylene glycol over 4 wk (n = 6). The 2 cultivars were also fed to 2 × 6 uninfected lambs. Nutrient digestibility, N balance, ADG, plasma urea, together with indicators of infection [fecal egg count (FEC), abomasal worm count, per capita female fecundity, erythrocytic indices, and serum protein], were determined. The specific effects of sainfoin cultivar, CT, and infection were evaluated by contrast analysis. Digestibility of both NDF and ADF were less (P < 0.001) with Perly compared with Visnovsky. The apparent nutrient digestibility was reduced (P < 0.001) by CT. However, no clear cultivar effects were evident on N excretion and retention. Condensed tannins reduced (P = 0.05) body N retention and shifted (P < 0.001) N excretion from urine to feces. Unlike cultivar and CT, infection decreased (P = 0.002) ADG. Plasma urea concentration was decreased (P = 0.007) in Perly- compared with Visnovsky-fed lambs and was decreased (P < 0.001) by CT. Plasma concentrations of essential and semiessential AA were increased (P < 0.001) by CT. The groups of infected lambs did not clearly differ in abomasal worm counts and erythrocytic indicators. In the last 2 to 3 wk of the experiment, FEC was decreased (P ≤ 0.01) when feeding CT. The lack of substantial cultivar effects suggests that the differences in CT properties may have been too small to result in nutritional and anthelmintic effects. The present results indicate that sainfoin CT had a mitigating effect on FEC and, consequently, pasture infectivity. However, the reduction was too small to expect any significant benefits in an Haemonchus-dominated system. Therefore, the use of sainfoin for controlling H. contortus should only be one component within an integrated worm control system.

The efficacy of a combined oral formulation of derquantel–abamectin against anthelmintic resistant gastro-intestinal nematodes of sheep in the UK

The objective of the present studies was to evaluate the efficacy of a combined formulation (Startect® Dual Active Oral Solution for Sheep, Pfizer Animal Health) of derquantel (DQL) and abamectin (ABA) for the treatment of: (1) sheep experimentally infected with a moxidectin (MOX)-resistant isolate of Teladorsagia circumcincta, and (2) multi-drug resistant gastrointestinal nematode parasites under UK field conditions. In the first study, a total of 40 animals were allocated into 4 treatment groups, and were either left untreated or treated with DQL+ABA, MOX or ABA. Faecal samples were collected on days 1–5 and on day 7 after treatment to examine the reduction in faecal egg excretion and to evaluate the egg viability. On day 14 post treatment all animals were euthanised for abomasal worm counts. There was a 100% reduction in geometric mean worm counts for the DQL+ABA treated animals compared to the untreated control animals (P<0.0001), whereas the percentage reduction in worm counts for the MOX- (P>0.05) and ABA-treated (P=0.0004) animals was 12.4% and 71.8%, respectively. The data from the egg hatch assay (EHA) indicated that in the MOX-treated and the ABA-treated animals, the majority of the eggs hatched after treatment. In the field study, performed on four farms, animals were allocated into 6 groups of 11–15 animals each in order to conduct a faecal egg count reduction test (FECRT), based on arithmetic mean egg counts. One group of animals remained untreated, whereas the other animals were treated with DQL+ABA, MOX, fenbendazole (FBZ), levamisole (LV) or ivermectin (IVM). On each of the farms the reduction in egg excretion after treatment with FBZ, LV or IVM was below 95.0%, indicating anthelmintic resistance. The efficacy of DQL+ABA ranged from 99.1 to 100%, yielding significantly lower egg counts compared to the untreated control group (P≤0.003). For MOX the egg counts were significantly (P≤0.003) lower compared to the untreated group at each farm, with reductions varying from 98.2 to 100%. The post-treatment copro-cultures for larva identification indicated that T. circumcincta was the most abundant worm species after treatment (52–99% of the larvae). The results of these studies confirm the high efficacy of the DQL+ABA combination formulation against anthelmintic resistant nematodes in the UK.

Rumen function and digestion of Merino sheep divergently selected for genetic difference in resistance to Haemonchus contortus

The aim of this experiment was to investigate the effect of Haemonchus contortus infection on rumen function and digestion of Merino sheep from lines divergently selected for genetic resistance to H. contortus. Rumen function and whole-tract digestibility were determined in 29 Merino weaner wethers from the CSIRO Haemonchus selection flock, increased resistance to Haemonchus (IRH), decreased resistance to Haemonchus (DRH) and random bred control (C) selection lines. Wethers were fed a restricted low quality roughage diet (5.9 MJ ME/kg DM, 29 g MP/kg DM) to maintain weight and were either uninfected (NIL) or infected with H. contortus (INF). Measurements were taken at week 7 of infection, while animals were housed in metabolic crates. Animals were then euthanased to determine abomasal worm counts. IRH had significantly lower worm egg count than DRH and C lines however, adult worm and larval counts, though lower in IRH animals, did not differ significantly. DM and OM digestibility and in sacco degradability of IRH and DRH selection lines were greater than C animals. Rumen function of animals from the IRH line was altered in response to H. contortus infection with an increase in fluid outflow and turnover rate and a decrease in propionic acid concentration. These changes may be a component of a greater host resistance and begin to explain the failure of IRH animals to translate lower worm egg count into greater bodyweight gain.

Effect of feeding Mucuna pruriens on helminth parasite infestation in lambs

Ethnopharmacological relevance Mucuna pruriens is a tropical legume anecdotally reputed to have anthelmintic properties. This study was conducted to examine the validity of such claims. Aim of the study The aim of this study was to determine if ingestion of Mucuna seeds reduces helminth parasite infestation in lambs. Materials and methods Thirty-six Dorper × Katahdin ram lambs were assigned to three treatments, a cottonseed meal based control diet, a diet in which Mucuna replaced cottonseed meal and the control diet with levamisole (7.5 mg/kg body weight) administration. All diets were isonitrogenous and isocaloric. The 12 lambs in each treatment were assigned randomly to 4 pens, each containing 3 lambs. Lambs were trickle infected three times per week by gavage with infectious Haemonchus contortus larvae (2000 larvae/lamb) for 3 weeks. Results Levamisole treatment decreased fecal egg counts by 87% and abomasal worm counts by 83%. Mucuna intake did not statistically affect fecal egg counts or abomasal worm counts, though numerical ( P > 0.10) reductions of 7.4% and 18.1%, respectively were evident. Anemia indicators, feed intake, and lamb growth were unaffected by treatment. Conclusions Levamisole reduced the Haemonchus parasite burden in lambs significantly but feeding Mucuna reduced the burden by levels unlikely to eliminate the clinical effects of parasitism.

Pathophysiology in Teladorsagia (Ostertagia) circumcincta-infected sheep selected for high fleece weight

Resilience to parasitism is considered to be the maintenance of growth and production during infection, probably associated with an immune response with lesser detrimental effects on the host relative to adverse effects on the parasite. Resilience to infection with Teladorsagia circumcincta was investigated in lambs from a flock selected for forty generations for high fleece weight (HFW), but with higher FEC and worm burdens than their unselected control (C) flock run in parallel. After recovery from surgery to implant abomasal cannulae, four parasite-naïve lambs from each flock were infected intraruminally at 6.5 months-of-age with 50,000 T. circumcincta L3, then from Day 35 to 70 post infection with 10,000 larvae at weekly intervals. Blood, abomasal fluid and faecal samples were collected daily to Day 35 and thence twice weekly for measurement of serum gastrin and pepsinogen concentrations, blood eosinophils, abomasal pH and FEC. Abomasal worm counts were made after necropsy on Day 94. Skin biopsies were collected weekly for estimation of the percentage of wool follicles containing paracortical cells. Total serum immunoglobulin and IgG1, IgG2, IgA and IgM titres specific for T. circumcincta antigens were estimated twice weekly to Day 42 p.i., then weekly. After the primary challenge, FEC were higher in the HFW lambs, whereas neither group shed many eggs during the 5-week trickle infection; worm burdens were small at post mortem. Resilient HFW lambs showed a lesser inflammatory response, but relatively small differences in abomasal secretion. Circulating eosinophil counts increased moderately in both groups, less in the HFW lambs, during the primary infection and more markedly during the subsequent trickle infection, when the increase in the C lambs became significantly greater. All measured serum antibody titres were low in both groups throughout. Selection for HFW altered the wool characteristics of parasite-naïve lambs (fewer follicles containing paracortical cells). There was a slower increase in the percentage of follicles containing these cells after primary infection. Abomasal function was similar in the two groups, both exhibiting typical increases in abomasal pH and serum gastrin and pepsinogen concentrations. The most marked differences in the HFW lambs were a greater rise in serum pepsinogen during the primary infection and the 2-day delay in onset of hypoacidity. Resilience to parasitism in this flock is consistent with maintenance of wool quality and small differences in abomasal secretion resulting from an attenuated immune response causing fewer detrimental effects on host tissues.

The use of chicory for parasite control in organic ewes and their lambs.

The aim of the present study was to investigate the potential benefits of grazing lactating ewes and their lambs on chicory (Cichorium intybus). Fifty-six certified organic twin-rearing ewes were either drenched with an anthelmintic or not, within 2 days after parturition and were grazed upon either grass/clover or chicory pastures. Around 12 weeks after parturition a subset of 12 lambs per treatment was slaughtered for worm number and parasite species determination. The faecal egg counts of lambs from undrenched ewes grazing on chicory were significantly lower than those of lambs from undrenched ewes grazing on grass. Lambs grazing on chicory had similar abomasal worm counts as those grazing on grass at 12 weeks of age; the predominant species was Teladorsagia circumcincta. There was no difference between the intestinal worm counts in lambs grazing on grass or chicory, with Trichostrongylus vitrinus being the predominant species. Liveweight gains over the 126-day experimental period were significantly higher in lambs from drenched than those from undrenched ewes. Lambs from undrenched ewes grazing on chicory had higher liveweight gains compared to those from undrenched ewes grazing on grass. Although chicory grazing did not affect ewe nematode egg excretion, it resulted in lower egg counts in lambs and improved their liveweight gains to the same level as those deriving from drenched ewes.

Towards the eradication of Haemonchus contortus from sheep flocks in Sweden

Previous studies have shown that between-year transmission of Haemonchus contortus in Swedish sheep flocks is almost entirely as over-wintered populations within housed animals, and not on pasture. This suggests that eradication of this parasite is a realistic possibility. Thus, two sheep farms with a history of H. contortus infection on the Swedish island of Öland were selected for study. During the winter housing period of 2003/2004 all ruminants (sheep and cattle) on both farms were treated with ivermectin. Monitoring by faecal egg counts and infective larval differentials of ewes and lambs for the subsequent two grazing seasons, together with total abomasal worm counts of 10 lambs from each farm at the end of the first grazing year, showed that this objective was achieved.

Pasture deworming and (or) subsequent feedlot deworming with fenbendazole. II, Effects on abomasal worm counts and abomasal pathology of yearling steers

734 steers, weighing 286 kg, were used during a 118-day grazing period, after which 640 were placed in a feedlot for finishing (average of 121 days, range of 111 to 133 days) to measure the main effects and interactions of 2 pasture deworming treatments (negative control, strategically dewormed with fenbendazole) and 2 feedlot deworming treatments (negative control, dewormed with fenbendazole) on faecal egg counts, abomasal worm counts and abomasal pathology. Seven to 10 abomasa from steers on each of the 4 pasture-feedlot treatments (pasture control-feedlot control; pasture control-dewormed in the feedlot; strategically dewormed on pasture-feedlot control; strategically dewormed on pasture-dewormed in the feedlot) were selected at slaughter to determine total worm counts, and to evaluate gross pathology and histopathology of the abomasal mucosa. Pasture deworming with fenbendazole (FBZ) in a strategic programme on days 0, 28 and 56 reduced adult and L4 and EL4 larval stages of Ostertagia ostertagi and adult and L4 stages of Trichostrongylus axei residing in the abomasum at slaughter. Feedlot deworming with FBZ reduced L4 and EL4 stages of O. ostertagi and adult and L4 stages of T. axei. An interaction between pasture deworming treatment and feedlot deworming treatment showed that pasture deworming had a significant effect on reducing the number of Trichostrongylus adult parasites, which was not further reduced by feedlot deworming. Strategic pasture deworming with FBZ followed by FBZ administration at the beginning of the finishing period reduced total O. ostertagi, T. axei and Haemonchus adult and larval stages by 99.13%, compared with untreated controls. There was no relationship between faecal egg counts and total worm counts. Gross pathology showed that strategic deworming on pasture reduced the mean abomasal lesion score at slaughter. An interaction between pasture treatment and feedlot treatment showed that feedlot deworming of pasture control steers reduced mean histopathology score, while feedlot deworming of steers strategically dewormed on pasture had no impact. Distribution of histopathology scores showed that strategic deworming on pasture resulted in more steers without histopathological changes to the abomasal mucosa and fewer steers with higher histopathology scores.

Nematode parasites of adult dairy cattle in the Netherlands

Abomasa, blood samples and faecal samples for examination of nematode infections were collected from 125 dairy cows during the period November 1997–October 1998. Of these, 12 had no grazing history and were, therefore, excluded from this study. From the remaining 113, 88.5% had nematode eggs in the faeces. Larval identification of the positive cultures showed that Ostertagia spp. larvae were most frequent (97%), followed by Trichostrongylus spp. (29%), Oesophagostomum spp. (23%), Cooperia punctata (20%), Cooperia oncophora (4%), Haemonchus contortus (2%) and Bunostomum phlebotomum (1%). The geometric mean EPG was 2.4. Two cows excreted larvae of Dictyocaulus viviparus (0.1 and 0.6 LPG resp.). Worms were found in the abomasa of 108 cows (96%). In all these abomasa Ostertagia spp. was present (100%). Trichostrongylus axei was found in 47 abomasa (43.5%) and two cows (2%) were infected with Capillaria bovis. The geometric mean of the total abomasal worm counts was 1743 and of Ostertagia spp. alone 1615. Almost all male worms were Ostertagia ostertagi, only occasionally Skrjabinagia lyrata was found. Early fourth larval stages (EL-4) were particularly present during the winter months: maximum in December (91.7%) and lowest in October (3.3%). Worm burdens were highest in young cows (<3 years) and older cows (>10 years). The highest individual abomasal worm count was 99,800 with 86% EL-4. Eighty-six cows (76%) had a low to moderate (100–10,000) and 22 cows (20%) a high (>10,000) total worm burden. Ostertagia specific antibodies were highest in late summer and autumn and lowest in spring and early summer. The same pattern, although not so pronounced, was observed for the serum pepsinogen values. No clear seasonal pattern was found for the Cooperia specific antibodies. Antibodies against D. viviparus were detected in seven cows (6%).