Helminths in horses: use of selective treatment for the control of strongyles

The current level of anthelmintic resistance in the horse-breeding industry is extremely high and therefore more emphasis is being placed on studies that focus on the judicious use of anthelmintic products. The aims of the study were to: 1) establish if there is variation in the egg excretion pattern of strongyles between the different age classes of Thoroughbred horses in the Western Cape Province (WCP), 2) test if a selective treatment approach successfully reduces the number of anthelmintic treatments and maintains acceptably low helminth burdens in adult Thoroughbred horses, and 3) evaluate the efficacy of subsampling large horse herds for faecal egg counts (FECs) to monitor the strongyle burden. In 2001 the FECs of 4 adult mare, 5 yearling and 3 weanling herds from 8 different farms were compared in the WCP Within the mare herds there were generally fewer egg-excreting individuals with lower mean FECs compared with the younger age classes. Individual faecal samples were collected every 3-4 weeks from 52 adult Thoroughbred mares from 1 farm in the WCP during a 12-month period (2002/2003). Animals with strongyle FECs > or =100 eggs per gram (epg ) were treated with an ivermectin-praziquantel combination drug (Equimax oral paste, Virbac). The mean monthly strongyle FEC for the entire group was <300 epg throughout the study and the number of treatments was reduced by 50 %. Resampling methods showed that an asymptote to mean FEC was reached at 55 animals for each of the pooled weanling, yearling and mare egg counts. Resampling within 4 different mare herds recorded asymptotes of between 24 and 28 animals. Subsampling entire herds for FECs therefore provided an effective approach to treatment management. This study demonstrates that selective treatment is both a practical and an effective approach to the management of anthelmintic resistance.     

Prevalence of benzimidazole resistance on horse farms in Germany

Faecal egg counts (FECs) were made on samples from 1383 horses on 64 farms in northern Germany between August 2000 and November 2001. There were significant differences between the mean FECs in the two years; in 2000, 59.6 per cent of 369 samples were positive and in 2001, 32.6 per cent of 1014 samples were positive for strongyle eggs. The results of a FEC reduction test indicated that resistance to fenbendazole was present on all 10 farms where it had been used, including in 33 of 60 horses tested. In contrast, treatment with ivermectin resulted in the complete elimination of nematode eggs in all the 77 horses tested. The mean LD50 values of the egg hatch test for thiabendazole indicated resistance on all 20 farms investigated and in 94 of 134 samples (70 per cent).     

Prevalence of strongyles and efficacy of fenbendazole and ivermectin in working horses in El Sauce, Nicaragua

Horses, mules and donkeys are indispensable farming and working animals in many developing countries, and their health status is important to the farmers. Strongyle parasites are ubiquitous in grazing horses world-wide and are known to constitute a threat to equine health. This study determined the prevalence of strongyle infection, the efficacy of ivermectin and fenbendazole treatment, and strongyle re-infection rates of working horses during the dry months in Nicaragua. One hundred and five horses used by farmers for transport of people and goods were randomly allocated into three treatment groups, i.e., the IVM group treated with ivermectin, the FBZ group treated with fenbendazole and the control group treated with placebo. Determined by pre-treatment faecal egg counts (FECs), horses showed a high prevalence (94%) of strongyle parasites with high intensities of infection (mean FEC of 1117 eggs per gram (EPG) with an SD of 860 EPG, n=102). Body condition scores of all horses ranged from 1.5 to 3.5 with a mean of 2.4 (scales 1-5). Fourteen days after treatment faecal egg count reductions (FECRs) were 100% and 94% in the IVM and the FBZ groups, respectively. The egg reappearance period (ERP) defined as the time until the mean FEC reached 20% of the pre-treatment level, was estimated as 42 days for the FBZ group and 60 days for the IVM group. Individual faecal cultures were set up and the larval differentiation revealed a 36% prevalence of Strongylus vulgaris before treatment (n=45). In the FBZ group, 25% of the horses were S. vulgaris-positive 70 days post treatment compared to 11% in the IVM group. Our results indicate that strongyle infection intensities in Nicaragua are high and that S. vulgaris is endemic in the area. Furthermore, efficacies and ERPs of IVM and FBZ were within the expected range with no signs of anthelmintic resistance.     

Daily variability of equine fecal strongyle egg counts.

Fecal egg counts often are used for diagnosing equine strongyle infections and estimating the number of eggs shed in the feces. An individual egg count should be interpreted in view of the normal fluctuation of egg numbers in an individual horse. In this study, the daily variability of strongyle fecal egg counts from horses was investigated. The Cornell-McMaster egg-counting technique was used to estimate the eggs per gram of feces in repeated daily fecal samples from 39 horses. The variation of the daily egg counts across 4 days was greater than would be expected if a consistent number of eggs were produced and dispersed randomly in the feces. The means and variances of the daily counts from each horse had a logarithmic relationship. For practical purposes, however, the fluctuation of egg counts is low enough for the fecal egg count to be used to identify horses for treatment, to estimate pasture contamination, or to assess response to therapy.     

Strongyle egg shedding consistency in horses on farms using selective therapy in Denmark

Knowledge of horses that shed the same number of strongyle eggs over time can lead to the optimization of parasite control strategies. This study evaluated shedding of strongyle eggs in 424 horses on 10 farms when a selective anthelmintic treatment regime was used over a 3-year period. Faecal egg counts were performed twice yearly, and horses exceeding 200 eggs per gram (EPG) of faeces were treated. The results are presented as probabilities of the egg count outcome, when two previous egg counts are known. A horse with no strongyle eggs detected in the two previous faecal examinations had an 82% probability of a zero, and a 91% of being below 200 eggs per gram in the third examination. A horse with the two previous egg counts below 200 EPG had an 84% probability of being below 200 EPG the third time as well. When faecal egg counts exceeded 200 EPG on the previous two counts, the probability for a horse exceeding 200 EPG the third time was 59%. In conclusion, these data demonstrate consistent shedding from one grazing season to another in a majority of horses despite treatment of horses exceeding 200 EPG.     

Endoparasite control management on horse farms – lessons from worm prevalence and questionnaire data

Reasons for performing study: Increasing prevalence of anthelmintic resistance in equine nematodes calls for a reexamination of current parasite control programmes to identify factors influencing control efficacy and development of resistance. Objectives: To investigate if associations occur between prevalence of parasitic nematodes and management practices. Methods: German horse farms (n = 76) were investigated in 2003 and 2004. Information on farm and pasture management with respect to endoparasite control measures obtained using a questionnaire survey. Faecal examinations were performed in parallel. Results: Horses (n = 2000) were examined by faecal nematode egg counts, grouped into foals, yearlings and mature individuals for statistical analyses. Farms were categorised into 3 types, riding, stud farms and small holdings. Count regression models were used to analyse strongyle faecal egg count data. Following dichotomisation of faecal egg count (FEC) data, prevalence of strongyle and Parascaris equorum infections were assessed by logistic regression models as a function from various management factors. Yearlings on stud farms showed a 2‐fold higher risk of being positive for strongyle FEC, higher (i.e. ≥3 per year) anthelmintic drug treatment frequencies were associated with reduced strongyle infection rates only in mature individuals but not in foals or yearlings, foals on farms fertilising pastures with horse manure had a significantly higher risk of being P. equorum FEC positive and yearlings on stud farms were more often showing incomplete FECR following anthelmintic treatment compared to yearlings on other farm types. The mean yearly treatment frequencies per age group were: foals 4.52, yearlings 3.26 and mature horses 2.72 times, respectively. Conclusion and potential relevance: To delay the development of anthelmintic, resistance management should include additional nonchemotherapeutic parasite control strategies, FEC‐monitoring, controlled quarantine treatment of new arrivals and control of efficacy by the faecal egg count reduction test on a regular basis.     

A comparison of the FECPAK and Mini-FLOTAC faecal egg counting techniques

Faecal egg counts (FECs) are used for detecting and quantifying nematode infections and are the basis for determining drug efficacy and anthelmintic resistance in faecal egg count reduction tests (FECRTs). Currently, several FEC techniques are available for detecting and quantifying eggs of sheep nematodes. A comparison of the egg counts from the FECPAK (with a minimum detection limit of 30 eggs per gram (epg)) and Mini-FLOTAC (with a minimum detection limit of 5 epg) showed better diagnostic performance with Mini-FLOTAC in terms of measurement error (level of over- or under-estimation of FEC) and precision (variability in FEC). A tendency to under-estimate FEC was observed with the FECPAK particularly at egg densities of less than 500 epg. It is concluded that Mini-FLOTAC is a reliable diagnostic tool offering reduced measurement error and a higher level of precision.     

Cyathostome fecal egg count trends in horses treated with moxidectin, ivermectin or fenbendazole

Commercial preparations of fenbendazole (Safe-Guard, Intervet), ivermectin (Eqvalan, Merial) or moxidectin (Quest, Fort Dodge) were administered once to horses scheduled for routine parasiticide treatment. In total, 93 horses from six cooperating farms were used in the study. Computer generated, random allocation of horses to treatment group was conducted at each farm. Fecal egg counts were determined for all horses on trial days 0, 56, 84 and 112, with corresponding calendar dates that were unique to each farm. Only strongyle egg counts from animals which were positive at day 0 were used for analysis of variance and comparisons. Counts for the three treatment groups were similar at day 0, moxidectin相似文献   

Field trial of the efficacy of a combination of ivermectin and praziquantel in horses infected with roundworms and tapeworms

Two hundred and thirty-three horses were screened for the presence of roundworms by faecal egg counts (FECs) and for tapeworms by an ELISA specific for antibodies to the immunodominant 12 kDa and 13 kDa tapeworms antigen. The 62 horses were found to be infected with both parasites were treated with a combination of 0.2 mg/kg ivermectin and 1.5 mg/kg praziquantel. The treatment suppressed the median FEC of the horses to zero for 10 weeks and significantly reduced their anti-12/13 kDa antibody levels. The estimated risk of tapeworm-associated colic in these horses was halved by 12 weeks after the treatment.     

Efficacy of avermectin B1 given orally against equine intestinal strongyles and Onchocera microfilaria

Three groups of horses and ponies (N = 13, 13 and 12) were treated with ivermectin paste (0.2 mg/kg p.o.), avermectin B1 solution (0.2 mg/kg p.o.), or fenbendazole suspension (10 mg/kg via nasogastric tube). The avermectin B1 was a 1% solution in a propylene glycolglycerol formal base. Faecal strongyle egg counts were performed before, and 14, 28, 42, 56 and 70 d, after treatment. Full-thickness skin biopsies from the neck, pectoral and umbilical regions were examined for Onchocera microfilaria before treatment, and again 14 and 70 d later. Ivermectin therapy produced a significant (P less than 0.01) decrease in mean strongyle egg counts 14, 28, 42 and 56 d after treatment. Avermectin B1 therapy resulted in significant (P less than 0.01) decreases in mean strongyle egg counts 14, 28 and 42 d after treatment. All horses given ivermectin or avermectin B1 had zero strongyle egg counts 14 and 28 d after treatment. Fenbendazole failed to significantly decrease strongyle egg counts. Both ivermectin and avermectin B1 resulted in zero microfilaria counts in all horses 14 d after treatment. On day 70 the percentage decrease in microfilaria counts were 100% and 99.6% respectively. Fenbendazole failed to significantly decrease microfilaria counts. The oral administration of this formulation of avermectin B1 appeared to be highly efficacious against intestinal strongyles and Onchocera microfilaria. The duration of anti-strongyle activity was, however, significantly (P less than 0.01) shorter than that of ivermectin paste.     

BENZIMIDAZOLE RESISTANCE IN SMALL STRONGYLES OF HORSES

Treatments with mebendazole, cambendazole or febantel were ineffective in reducing the faecal egg count of a group of 40 horses infected with small strongyle species. Evidence was also obtained that this apparent resistance extended to fenbendazole. In horses dosed with morantel tartrate egg counts were reduced to zero by 7 days after treatment. The development of resistance is discussed in relation to previous treatment of the horses and the mode of action of febantel.     

Anti-strongyle activity of a propylene glycol-glycerol formal formulation of ivermectin in horses (mares)

Four groups of 10 horses (mares) each were treated with a 1% solution of ivermectin (200 micrograms/kg of body weight) in a propylene glycol-glycerol formal base orally, a 1% solution of ivermectin (200 micrograms/kg) in a propylene glycol-glycerol formal base via nasogastric tube, a 1.87% paste of ivermectin (200 micrograms/kg) orally, or a 22.7% paste of oxibendazole (10 mg/kg) orally. Fecal examinations were done before treatment and on posttreatment days (PTD) 14, 28, 42, 56, and 70. Strongyle egg per gram counts and sugar flotation fecal examinations were performed. Results of fecal examinations before treatment were similar in all horses. All horses treated with ivermectin had similar percentages of reductions in mean strongyle egg per gram counts after treatment; 100% on PTD 14, 28, and 56 and 93.4% to 98.7% on PTD 70. All ivermectin treatment groups had 0 horses detected as passing strongyle eggs on PTD 14 and 28, 0 to 2 on PTD 42, 3 to 5 on PTD 56, and 8 to 9 on PTD 70. Horses treated with oxibendazole had 99.9%, 99.7%, 92.9% 78.6%, and 54.5% reductions in mean strongyle egg per gram counts and 5, 7, 8, 9, and 9 horses detected as passing strongyle eggs on PTD 14, 28, 42, 56, and 70, respectively. Adverse reactions to treatment were not observed.     

Expulsion of small strongyle nematodes (cyathostomin spp) following deworming of horses on a stud farm in Sweden

This study was conducted on a stud farm in Sweden to investigate the species composition of cyathostomins expelled in the faeces of horses after deworming using three different anthelmintic preparations. Twenty-seven horses excreting > or = 200 strongyle eggs per gram faeces (EPG) were divided into three comparable groups and dewormed on day 0 with either of following compounds: 0.2 mg ivermectin per kg body weight (bw), 19 mg pyrantel pamoate per kg bw or 7.5 mg fenbendazole per kg bw. For each of the 3 days following anthelmintic treatment faeces was collected from individual horses and subsamples were fixed in formalin. Four days after the anthelmintic treatment all horses were re-treated with ivermectin and faeces was collected on day 5. Individual subsamples from each of the four sampling occasions were examined for cyathostomin nematodes. Sixty-three to 270 worms per horse were identified to the species level. The majority of the worms recovered were expelled during the first day from horses treated with ivermectin or pyrantel pamoate, and during the second day from horses treated with fenbendazole. Fifteen cyathostomin species were identified and the six most prevalent were Cylicocyclus nassatus, Cyathostomum catinatum, Cylicostephanus longibursatus, Cylicocyclus leptostomus, Cylicostephanus minutus and Cylicostephanus calicatus. These species composed 91% of the total burden of cyathostomins. The number of species found per horse ranged from 6 to 13, with an average of 9. No significant differences in species composition or distribution were found between the treatment groups. On day 5, i.e. 1 day after the last ivermectin treatment, 93% of the adult worms were recovered from horses in the fenbendazole group.This study showed that it was possible to identify cyathostomins expelled in faeces of dewormed horses, and that the most prevalent species corresponded to those found in autopsy surveys performed in other countries.     

Association between variation in faecal egg count for a mixed field-challenge of nematode parasites and ovine MHC-DQA2 polymorphism

The selection of sheep that are resistant to gastrointestinal parasites and have lower faecal egg counts (FECs) has been the subject of extensive research. This has led to the speculation that the Major Histocompatibility Complex (MHC) genes could be used as markers to reduce FEC. In this study, associations between variation in ovine MHC-DQA2 and various measures of FEC recorded at two times (approximately 4 and 9 months of age) were investigated in a large group of New Zealand lambs (n=4676), derived from 185 different sire-lines, of a variety of breeds and raised on 25 separate farms. Pair-sample t-tests revealed that FEC for Nematodirus spp., Strongyle spp. and total FEC differed significantly between the two assessments. A total of twenty one DQA2 alleles or DQA2-DQA2-like haplotypes were identified, with allele/haplotype presence and frequency varying significantly between farms. For example, allele *0103 was observed on all farms, ranging in frequency from 0.2 to 60.9%, while haplotype *0101-*1601 was only present on one farm, in two lambs. A number of associations between the presence/absence of these alleles and egg counts were observed, but nearly all the allelic/haplotypic associations were age and parasite specific, suggesting that immune response is both age and challenge (parasite species mix) dependent. The exception was allele *1201 which was associated with increased total FECs at both 4 and 9 months of age; with it either being, or tending toward being, significantly associated with both increased Strongyle spp. and Nematodirus spp. counts as well. However, the observed increases in egg counts were small and ranged between 5 and 32 eggs per gram. In conclusion, we believe that the MHC plays an important role in parasite resistance, but that the MHC-nematode interaction is complex and thus the development of a single gene-marker based on the "MHC effect" is unlikely.     

Genetic parameters for strongyle and Nematodirus faecal egg counts in lambs and their relationships with performance traits

Genetic resistance to the gastro-intestinal parasites of lambs can contribute to sustainable systems of parasite control with associated benefits for health and welfare. This study reports estimates of the genetic parameters of strongyle egg counts (FEC), Nematodirus egg counts (NEM), faecal consistency scores (FCS) and their associations with growth and ultrasonic measurements of muscle (UMD) and fat (UFD) depths in lambs. The lambs were the progeny of 45 Bluefaced Leicester sires from Scottish Blackface and Hardy Speckled Face dams. Faecal samples were taken from lambs at 10, 14, 18, 22 and 26 weeks of age, giving 1024 to 3055 records per trait. Live weight was recorded for all lambs at 16 weeks and live weight, UMD and UFD were recorded in female lambs at 28 weeks. Mean FEC and NEM were significantly higher for twin versus single reared lambs, for male castrate versus female lambs and for the offspring of Scottish Blackface versus Hardy Speckled Face ewes. Heritability estimates for FEC were low (0.04 ± 0.02 to 0.20 ± 0.08) and showed a non-significant trend to increase with age. The phenotypic correlations between measures of FEC at different ages were low (0.06 to 0.34) but genetic correlations were not significantly different from one in most cases. Heritability estimates of NEM ranged from 0.05 ± 0.03 to 0.09 ± 0.05 and genetic correlations among counts at different ages were not significantly different from zero. FEC and NEM were strongly correlated genetically (0.62 to 0.93) and estimates of the genetic correlations between FEC and NEM with live weights (− 0.36 to 0.23), UMD (− 0.35 to 0.25) and UFD (0.08 to 0.55) were variable in sign, though not significantly different from zero. Heritability estimates for faecal consistency scores (FCS) were 0.06 ±0.03 to 0.11 ± 0.04, with strong genetic correlations between successive measures. FCS was not significantly correlated with FEC or lamb performance traits. It is concluded that selection for reduced strongyle egg counts in lambs at around 5–6 months of age will give favourable correlated responses in NEM in lambs, with limited correlated response in lamb performance or faecal consistency scores.     

Quantifying the sources of variability in equine faecal egg counts: implications for improving the utility of the method

The faecal egg count (FEC) is the most widely used means of quantifying the nematode burden of horses, and is frequently used in clinical practice to inform treatment and prevention. The statistical process underlying the FEC is complex, comprising a Poisson counting error process for each sample, compounded with an underlying continuous distribution of means between samples. Being able to quantify the sources of variability contributing to this distribution of means is a necessary step towards providing estimates of statistical power for future FEC and FECRT studies, and may help to improve the usefulness of the FEC technique by identifying and minimising unwanted sources of variability. Obtaining such estimates require a hierarchical statistical model coupled with repeated FEC observations from a single animal over a short period of time. Here, we use this approach to provide the first comparative estimate of multiple sources of within-horse FEC variability. The results demonstrate that a substantial proportion of the observed variation in FEC between horses occurs as a result of variation in FEC within an animal, with the major sources being aggregation of eggs within faeces and variation in egg concentration between faecal piles. The McMaster procedure itself is associated with a comparatively small coefficient of variation, and is therefore highly repeatable when a sufficiently large number of eggs are observed to reduce the error associated with the counting process. We conclude that the variation between samples taken from the same animal is substantial, but can be reduced through the use of larger homogenised faecal samples. Estimates are provided for the coefficient of variation (cv) associated with each within animal source of variability in observed FEC, allowing the usefulness of individual FEC to be quantified, and providing a basis for future FEC and FECRT studies.     

Evaluation of febantel used concurrently with piperazine citrate in horses

Fifty horses from a herd known to have benzimidazole-resistant small strongyles were treated with febantel (6 mg/kg), combinations of febantel (6 mg/kg) and piperazine citrate (25 or 55 mg base/kg), thiabendazole (44 mg/kg), or placebo (0.6 ml of water/kg). Pretreatment and 7-day posttreatment fecal examinations were done. Fecal cultures, strongyle egg per gram (epg) counts, sugar flotation fecal examinations, and in vitro testing for benzimidazole resistance were performed. Results of fecal examinations before treatment were similar in all horses, and results of testing were positive for benzimidazole resistance. Horses treated with febantel and piperazine at all dosages had significantly lower mean strongyle epg counts and greater percentage reduction in mean strongyle epg counts (99.7% to 99.9%) 7 days after treatment, compared with those determined for horses treated with febantel, thiabendazole, or placebo. Adverse reactions to treatment were not observed.     

Comparison of ivermectin, oxibendazole, and pyrantel pamoate in suppressing fecal egg output in horses

Thirty resident horses at a boarding stable in Alberta were used to evaluate the relative efficacies of ivermectin, oxibendazole, and pyrantel pamoate in reducing fecal egg output in adult horses under routine management conditions during spring and early summer, and to more clearly define the duration of suppression of fecal egg production following anthelmintic treatment. Horses were blocked according to pretreatment egg counts and randomly assigned to one of three treatments: pyrantel pamoate at 6.6 mg/kg body weight; oxibendazole at 10 mg/kg body weight; or ivermectin at 200 μg/kg body weight. All treatments were administered orally as a paste on day 0.Fecal samples were collected for examination by the modified Wisconsin procedure before treatment, and then at 4-11 day intervals up to day 72.

Very few if any strongyle eggs were found in the feces of any horses up to day 35. On days 42, 50 and 57, the geometric mean egg count for the ivermectin group was significantly (p<0.05) lower than that for the oxibendazole or pyrantel pamoate groups. Based on a survival curve analysis of the data, the mean number of days for recurrence of eggs in the feces was significantly longer for the ivermectin group than for the oxibendazole and pyrantel pamoate groups.

Under conditions encountered in this study, the posttreatment interval to resumption of fecal egg out-put in horses treated with ivermectin was eight to nine weeks, compared with five to six weeks for horses treated with oxibendazole or pyrantel pamoate.

     

Preliminary Analysis of the Results of Selective Therapy Against Strongyles in Pasturing Horses

Control of horse parasites often omits application of measures to eradicate the free-living stages in pastures and frequently relies on chemotherapy only. Selective therapy was used for Spanish Sport horses grazing either in the same pasture (continuous) or in rotated meadows. In each group, equines exceeding a cutoff value of 300 strongyle eggs per gram of feces received ivermectin or moxidectin. Efficacy of the treatment was assessed by estimating reduction of fecal egg counts and the number of horses shedding parasite eggs (PHR). Coprocultures revealed presence of the cyathostomins Cyathostomum and Gyalocephalus spp. In all treated groups, a 100% value for both reduction of fecal egg counts and PHR against cyathostomins was obtained, and PHR values ranged from 100% to 12%. The longest strongyle egg reappearance period was observed in horses undergoing rotation grazing and receiving ivermectin (9 weeks), compared with a 6-week period recorded for the other treated equines. Our results seem to point that the efficacy of selective therapy in equine herds could be reduced if the horses with fecal egg counts below the threshold value (thus not receiving chemotherapy) remain grazing in the same pastures with the treated ones. It is strongly suggested that interested parties consider performing periodic fecal analyses to monitor fecal egg counts, together with the percentage of horses passing eggs in feces, to improve the effect of this procedure.     

Comparison of the persistent activity of ivermectin, abamectin, doramectin and moxidectin in cattle in Zambia

The persistent efficacy of four commercially available macrocyclic lactones (ML) in maintaining reduced faecal egg counts in cattle grazing naturally infested pastures was evaluated in 44 zebu animals aged 1–2 years in Zambia. The study started in February (rainy season) when the strongyle egg output was increasing. Four days before the start of the trial, all animals were treated with a double dose of oxfendazole. They were then divided into five groups which were again treated on day 0. Groups A, D, I and M received 0.2 mg kg⁻¹ of abamectin, doramectin, ivermectin and moxidectin, respectively. Animals of group C received albendazole (7.5 mg kg⁻¹). Faecal samples were collected twice a week for egg counts and larval differentiation. Faecal egg counts in the C group increased from day 21 onwards and plateaued from day 42 between 180 and 380 eggs per gram. The main genera found in cultures were Cooperia (90%) and Haemonchus (7%). Faecal egg excretion in groups M, A, D and I started on day 35, 42, 42 and 45, respectively. subsequently and until day 84, average counts in these four groups were always significantly lower than in group C. Compared with albendazole, all four ML gave over 95% reduction in cumulative faecal egg counts for 42 days after treatment. The percentage efficacy was still over 84% by day 84 when an average cumulative egg count of 11 320 eggs per gram faeces was calculated in group C. In addition, there was no significant difference in efficacy between the four ML groups at any of the sampling dates. During the trial no significant difference in weight gain between any of the groups was observed.