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1.
Faecal worm egg counts of goats from two farms in Penang Island, West Malaysia, were monitored over a period of 14 months. The faecal egg count pattern followed that of total rainfall. The humid tropical environment was favourable for the development of various species of trichostrongylid nematodes, namely Haemonchus contortus, Trichostrongylus spp., Oesophagostomum spp. and Cooperia spp. Generally, H. contortus was observed to be the predominant species, more so in the monsoon months of the year.  相似文献   

2.
Over a period of 13 months, faecal samples were collected monthly from approximately 45 cattle over 3 months of age. Additionally, 74 calves of 1-2 months were sampled to determine the presence of Toxocara vitulorum eggs. Individual egg counts and infective strongyle larvae from pooled faecal samples were examined. Post-mortem worm counts were carried out on six groups of tracer calves (n=12) that had been kept for 4 weeks on pasture in and around the village studied. The following helminths were identified: T. vitulorum, Cooperia punctata, C. pectinata, C. oncophora, Oesophagostomum radiatum, Trichostrongylus axei, T. colubriformis, Haemonchus spp., Fasciola spp. and Paramphistomum spp. In 8% of the samples collected from young calves, individual egg counts for T. vitulorum were found indicative for pathogenic worm burdens. Strongyle egg counts and worm counts indicated that transmission is low without a distinct seasonality. In animals of 3-9 months old, a strongyle egg count peak can be demonstrated which at a higher age steadily and significantly decreased. In faecal cultures Cooperia spp. were most prominent in all age groups throughout the year with the exception of the period September-November when Haemonchus spp. and Oesophagostomum spp. were most prevalent. Fasciola spp. eggs were found in 22% of the collected faecal samples and the egg counts were low indicating that the intensity of Fasciola spp. infection is mild. Based on the present data, regular anthelmintic treatments seem not to be justified, except for a single treatment at the age of 2 weeks against toxocariosis.  相似文献   

3.
In a study on the seasonal dynamics of the gastro-intestinal nematode egg production in horses, one breeding farm also revealed a particularly high prevalence of Anoplocephala spp. infection. Consequently, this farm was chosen for analysing the seasonal pattern of the tapeworm egg excretion over a one year period in order to establish the most favourable periods for an appropriate and successful cestocidal treatment. The seasonal analysis showed a significantly higher (p < 0.05) Anoplocephala spp. egg excretion between July and October, i.e. during the second part of the grazing period. This result clearly underlines the importance of a cestocidal treatment during that period of the year. Subsequently, horses of this farm and of a second farm with a high prevalence of Anoplocephala spp. were used to evaluate the efficacy of praziquantel in a specific oral gel formulation for horses under field conditions. The efficacy of praziquantel was tested in a total of 33 horses from the two farms harbouring a coproscopically detected Anoplocephala spp. infection prior to treatment. Praziquantel (Droncit 9%, oral gel, 1 mg/kg bodyweight) was administered to the horses according to their body weight. The efficacy of the drug was evaluated ten days after treatment by a double faecal analysis. Thereby, no Anoplocephala spp. eggs were found in the faeces of 32 horses (97%). The single horse remaining positive for Anoplocephala spp. eggs did not completely swallow the anthelmintic gel and consequently, did not receive the appropriate dose of the drug.  相似文献   

4.
The relative prevalences of Trichostrongylus vitrinus, T. colubriformis and T. rugatus in sheep in south-west Western Australia were examined for evidence of associations with climatic conditions in different localities. The region has a mediterranean-type climate with hot, dry summers and cool, wet winters. The intestinal Trichostrongylus spp. populations in sheep sampled comprised 50% T. vitrinus, 38% T. colubriformis and 12% T. rugatus. The prevalence of T. vitrinus was negatively correlated with mean autumn, winter and spring temperatures of a locality. The prevalence of T. colubriformis was positively correlated with mean autumn, winter and spring temperatures. The prevalence of T. rugatus was not correlated with temperature of any season, but was negatively correlated with mean annual rainfall and length of growing season of a locality. There were suggestions of association of amount of rainfall of a locality and prevalence of T. rugatus was not correlated with temperature of any season, but was negatively correlated with mean annual rainfall and length of growing season of a locality. There were suggestions of association of amount of rainfall of a locality and prevalence of T. colubriformis and of differences in seasonal prevalence of T. vitrinus, but the significance of these was obscured by confounding of some climatic factors. The differences in prevalence of the three Trichostrongylus spp. at different locations was attributed to differences in preferred ambient conditions for development and survival of the free-living stages.  相似文献   

5.
Anthelmintic resistance in Australian sheep nematode populations   总被引：2，自引：0，他引：2  
SUMMARY The resistance status of gastro–intestinal nematodes to anthelmintics was evaluated on 881 sheep farms throughout Australia during 1991–92. Resistance was shown to be widespread. Overall, 85% of farms had sheep infected with nematodes resistant to benzimidazole, 65% to levamisole and 34% to combination (benzimidazole + levamisole) products. Resistance to ivermectin was not detcted. On only 9% of farms did all anthelmintic groups reduce egg counts by greater than or equal to 95%. The culture of faeces from untreated sheep showed Telodorsagia circumcincta, Trichostrongylus spp, Chabertia ovina and Haemonchus contortus to be the principal species. The nature and prevalence of resistance was not significantly correlated with stocking rate. However, resistance to combination products was almost twice as prevalent on farms in areas with an average annual rainfall of greater than 500 mm.  相似文献   

6.
OBJECTIVE: To relate trichostrongylid infections acquired by sheep during summer to prevailing weather conditions. PROCEDURE: Groups of worm-free 'tracer' sheep were put onto pastures, previously contaminated with trichostrongylid eggs, for successive periods of 2 weeks from December to March. After grazing the sheep were housed for 6 weeks. Weekly worm egg counts and worm counts were used to estimate the numbers of worms acquired and related to weather conditions during the grazing period. RESULTS: No worm eggs were detected in the faeces of sheep that grazed at the end of January when only 7 mm of rainfall was recorded. At other times rainfall between 12 and 24 mm occurred and strongyle egg counts were generally either < 50 or > 150 eggs per g (epg). Mean counts of 1,100 Ostertagia and Trichostrongylus adults gave rise to mean counts of about 350 epg whereas about 6,000 Nematodirus spp were associated with mean egg counts of about 200 Nematodirus spp epg. CONCLUSIONS: Rainfall events during summer determine the numbers of trichostrongylid larvae acquired by sheep in summer but further studies are necessary before the implications for strategic control programs in southern Australia can be fully assessed.  相似文献   

7.
A longitudinal survey was carried out to determine and describe the prevalence and intensity of gastrointestinal parasite infections and Dictyocaulus viviparus in a dairy and a beef cattle farm of two different ecological zones in Costa Rica. The influence of anthelmintic treatment, age and meteorological factors (rainfall, minimum and maximum temperatures) on gastrointestinal nematodes and D. viviparus counts was determined. Calves were subjected to monthly sampling of feces and blood between April 2002 and March 2003. Coprological techniques were used to detect gastrointestinal helminthes, protozoan and D. viviparus. Blood samples were analyzed for antibodies to D. viviparus by ELISA. The most prevalent gastrointestinal parasites detected on both farms (dairy cattle, A; beef cattle, B) were Eimeria spp. (94.7%, 93.7%), Strongylidae (75.0%, 81.4%), Buxtonella sulcata (38.0%, 21.6%) and Strongyloides papillosus (29.8%, 31.7%), whereas Moniezia benedeni (4.8%, 9.1%), Trichuris spp. (7.3%, 13.2%), Toxocara vitulorum (0.0%, 1.8%) and Entamoeba bovis (2.5%, 1.1%) were less prevalent. Mean fecal egg counts (FEC) showed highest values of Strongylidae in April, May and July (>335.3 eggs/g feces) on farm A, and April, May and August (>304.3 eggs/g feces) on farm B. S. papillosus presented low FEC throughout the year on farm A, on farm B the highest values were obtained in April (303.0 eggs/g feces). Trichuris spp. presented maximum FEC values in May (328.6 eggs/g feces) on farm A and in June (157.5 eggs/g feces) on farm B. Treatment and age had significant influence on infection intensity of Strongylidae (farms A and B), S. papillosus (farms A and B) and Trichuris spp. (farm A). Rainfall had significant effect on S. papillosus (farms A and B) and Trichuris spp. (farm B). Maximum temperature showed significant effect on S. papillosus (farm A) and Trichuris spp. (farms A and B). Minimum temperature had significant influence on Strongylidae (farm A), S. papillosus (farms A and B) and Trichuris spp. (farm B). Haemonchus spp. (57%, 66%) and Cooperia spp. (30.0%, 30.7%) were the most prevalent genera identified by coproculture on both farms, in contrast, Trichostrongylus spp. and Oesophagostomum spp. were less frequent. Patent lungworm infections were low on both farms (10.8%, 1.8%). On farm A, high prevalence of antibodies against D. viviparus was determined only at the beginning of the study, in contrast, on farm B the seroprevalence fluctuated throughout the year. Treatment, age and maximum temperature had significant effect on D. viviparus counts on farm A, but not on farm B.  相似文献   

8.
Haemonchus, Trichostrongylus, Ostertagia and Nematodirus worm populations of sheep based on differential egg counts are considered in relation to climatological and topographical data. Late spring, summer and early autumn rainfalls are related to ground slope to assess wetness. Egg counts indicated that the estimated worm populations in animals in flat areas with low rainfall were as heavy as or heavier than in animals on steep hilly areas with a high rainfall. It is proposed that tactical anthelmintic treatment be based on the degree of wetness of the grazing or farm.  相似文献   

9.
An investigation into the helminth species present in cattle in the East Kimberley and Victoria River Districts of Northern Australia was conducted over a 2-year period based on bi-monthly total and differential worm counts in weaner cattle as well as on a post mortem survey of adult cattle sent for slaughter. The most important species found in young cattle were Haemonchus placei and Cooperia spp. Only small numbers of Bunostomum phlebotomum, Nematodirus spathiger, Oesophagostomum radiatum and Moniezia benedini were present. Calicophoron calicophorum and nodules of Onchocerca spp. and Oe. radiatum were recorded in adult cattle. Seasonal fluctuations in helminth parasite burdens are discussed in relation to temperature and rainfall and the results are interpreted in relation to the effects of helminthosis on present and future beef production in this area.  相似文献   

10.
Identification of the presence and abundance of species is important when choosing therapies and control strategies for internal parasitism of livestock. Here we examine lectin binding characteristics of eggs isolated from sheep faeces as a means for identifying the parasite genera contributing to infection. The intensity of lectin staining varied with incubation time, incubation volume, concentration of lectin and concentration of eggs. Formalin fixed eggs had greater autofluorescence but exhibited the same lectin staining pattern as fresh eggs. The stage of egg development did not influence staining. Eggs from Haemonchus contortus, H. placei, Trichostrongylus colubriformis, T. vitrinus, Ostertagia circumcincta, Nematodirus spathiger and the cestode Monezia expansa were incubated with a panel of fluoroscein isothiocyanate (FITC)-labelled lectins. Lectin binding exhibited a genus specific pattern. Haemonchus spp. stained strongly positive with peanut agglutinin (PNA), and were positive for concanavalin A (ConA), Ricinus communis agglutinin (RCA) and Maclura pomifera lectin (MPA). Trichostrongylus spp. were PNA-, ConA-, RCA- and strongly MPA+. O. circumcincta were weakly positive for PNA, MPA, ConA and negative for RCA. N. spathiger were weakly positive for the four lectins, and M. expansa were weakly positive for PNA, RCA and MPA and were strongly ConA+. The genus specificity of lectin staining was used to identify the presence of Trichostrongylus and Haemonchus eggs in faeces from sheep with mixed field infections, however correspondence between lectin staining and larval differentiation for identifying a low prevalence of Ostertagia in the field infection was poor. Refinements in methods for rapid egg isolation may improve egg differentiation on the basis of lectin staining, which could be undertaken by flow cytometry or microscopy.  相似文献   

11.
Twenty-two Dorset Rambouillet lambs were moved to contaminated pasture on Apr 1, 1987. At regular intervals thereafter, pairs of lambs were withdrawn and euthanatized. Gastrointestinal parasites in the abomasum, small intestine, cecum, and large intestine were removed and counted. The last pair of lambs was euthanatized 8 months after original placement on the contaminated pasture. Fecal samples were taken at 3- to 4-week intervals throughout the grazing season and the fecal egg counts were used to estimate parasite fecundity (output of eggs per female parasite per day). The principal parasite genera found included Haemonchus spp, Trichostrongylus spp, and Nematodirus spp. In each of the genera examined, parasite fecundity remained the same irrespective of the intensity or duration of infection. Estimated average fecundities (eggs/female/day) were as follows: Haemonchus contortus, 6,582; Trichostrongylus spp, 262; Nematodirus spp, 40; and Oesophagostomum venulosum, 11,098.  相似文献   

12.
Surveys to determine the prevalence and degree of resistance of Haemonchus spp. of sheep and goats to the available anthelmintics in South Africa indicate that small ruminant production is entering a crisis situation. Three surveys employing the faecal egg count reduction (FECR) test to determine resistance were conducted in some of the main sheep-producing areas in the summer rainfall region of South Africa, where H. contortus is the principal worm species in sheep. After analyzing the data recorded in the surveys by six different methods, including the RESO test at two different levels of confidence, the results obtained in the least stringent one (geometric mean reduction of the worm egg counts of drenched, vs untreated group of sheep) are reported in this paper, so that if any bias was obtained it would be in the favour of the anthelmintic. In Mpumalanga and KwaZulu-Natal there was anthelmintic resistance in Haemonchus spp. on all the 52 farms surveyed. Sixteen percent of the strains of H. contortus were < 60% susceptible to three of the four anthelmintics tested, and 8% of the strains were < 40% susceptible to all four of the anthelmintics. FECR tests of sheep in six localities in the Lebowa district of Northern Province indicated that even in previously disadvantaged communities where anthelmintic treatment is less intensive, anthelmintic resistance is developing, and is possibly at the level at which the situation on commercial sheep and goat farms in South Africa was 25 years ago. From the data it appears that the level of anthelmintic resistance of H. contortus in South Africa is possibly the highest that has so far been recorded in the world and that strains of it are emerging that may soon not be controllable by treatment with any of the existing anthelmintics. Farmers in the summer rainfall region, if not the whole country, must be alerted to the immediate need for testing the parasite burdens of their sheep for susceptibility to preparations in all four groups of anthelmintic compounds currently available. Alternative methods of integrated worm control, including biological, must be sought and implemented with urgency, to reduce further selection for resistance and to induce reversion of the resistance that has already developed.  相似文献   

13.
Strategic application of moxidectin pour-on (Cydectin) was evaluated in Uganda for its effect on pasture larval counts and gastrointestinal nematode faecal egg counts in village cattle kept under tethering (semi-intensive) grazing management. The strategic deworming schedule involved treating cattle twice at an interval of 2 months, at the end of the 1st wet season and during the 2nd wet season. Two groups of 30 cattle, each consisting of a treated and a control group, were examined for nematode infections every 4 weeks from June 1999 to January 2000. The treated group had significantly lower mean faecal egg counts than the untreated groups (t-value = 2.47, P < 0.05). Generally, the pasture larval counts on treated farms were lower than on untreated ones, but not significantly so (t-value = 2.22, P = 0.068). Pasture larval counts with different nematode species on treated farms were lower than on untreated ones, but the differences were not significant for Haemonchus spp. (t-value = 1.68, P = 0.145), Oesophagostomum spp. (t-value = 1.87, P = 0.111), Trichostrongylus spp. (t-value = 1.93, P = 0.102), Dictyocaulus spp. (t-value = -0.74, P = 0.485) and Cooperia spp. (t-value = -1.00, P = 0.356). Treated farms did, however, have significantly lower pasture larval counts of Bunostomum spp. (t-value = 4.64, P < 0.05). This study has revealed that the application of moxidectin pour-on on cattle has an effect on faecal egg count and pasture contamination under the tethering grazing system. Moxidectin pour-on and the strategic deworming schedule evaluated here could be used for the control of gastrointestinal nematode infections in cattle by small-scale farmers who practise tethering or semi-intensive grazing management in Uganda and other tropical countries, especially where there is a bimodal rainfall pattern.  相似文献   

14.
Spionidae, particularly polydorids, are common polychaete parasites of edible mollusks around the world. However, our understanding of the regulatory factors and population structure of these parasites is scant. In this study involving Polydora bioccipitalis and the surf clam Mesodesma donacium we evaluated (1) the environmental correlates of the prevalence and mean intensity of the infestation, (2) the relationship between the number of egg capsules and juvenile and adult parasites and the time elapsed since infestation, and (3) the spatial patterns of juveniles and adults within the host. Environmental factors showed no significant correlations with prevalence and mean intensity, suggesting that these factors do not act directly as regulators. Rather, storm surges seemingly induced clam stranding, which in turn affected both the prevalence and intensity of the infestation. The numbers of juveniles and egg capsules in blisters were significantly related to the time since infestation, suggesting mechanisms of use and expansion of the space within the host. Juvenile worms showed an aggregated distribution that was probably related to the episodic nature of infestation events, whereas adults exhibited uniform distributions that probably reflect territorial behavior and reproductive strategies.  相似文献   

15.
Faecal samples were collected from 348 yaks(Bos poephagus) in and around Gurudogmer Plateau, a cold desert area in North Sikkim, India. The prevalence of gastrointestinal parasitic infection was recorded at 10.05% in both the organized and traditionally managed farms of yak. The pattern of infection was either single (2.58%) or mixed (7.47%) with a faecal egg count range of 100–200 eggs per gram of faeces in positive animals. Among the helminths, Haemonchus spp. infection was predominant (6.89%) followed by Nematodirus spp. (1.72%), Cooperia spp. (1.43%) and Dicrocoelium spp. (0.29%).  相似文献   

16.
The prevalence of gastrointestinal parasites in stray dogs, and dogs with owners was investigated by fecal examinations from 271 dogs employing sedimentation, simple flotation and centrifugation-flotation methods. The centrifugation-flotation method, when compared to simple flotation or sedimentation methods was generally more accurate in the diagnosis of all intestinal parasites, but statistical differences were detected only in relation to Giardia spp. and Cystoisospora spp. (synonym Isospora spp.). The following parasites, with their respective prevalence, were diagnosed in the fecal samples: Ancylostoma spp. (23.6%); Toxocara canis (5.5%); Trichuris vulpis (4.8%); Spirocerca lupi (1.9%); Dipylidium caninum (0.7%); Giardia spp. (12.2%); Hammondia heydorni (2.6%); Cystoisospora spp. (8.5%); and Sarcocystis spp. (2.2%). The prevalence of most parasites was similar for dogs of mixed-breed and for dogs of a defined-breed, except for Cystoisospora spp. and T. canis which showed a significantly higher prevalence in mixed-breed dogs. The prevalence of Ancylostoma spp. (17.1%) was significantly lower in stray dogs than in those with an owner (31.9%) and the prevalence of Giardia spp. and Cystoisospora spp. was higher in stray dogs (P < 0.05). No effect of season on the occurrence of the different parasite genera could be observed, except for Ancylostoma spp., for which an increase in the percentage of dogs shedding eggs was observed at the beginning of Summer with a peak occurrence during April and May (Autumn). The prevalence of Ancylostoma spp., T. canis, T. vulpis, Giardia spp. and Cystoisospora spp. was higher in adult males than in adult females, but significant differences between the two groups occurred only with Giardia spp. Young animals were found to more frequently shed Nematode eggs in feces than adult animals.  相似文献   

17.
Faecal samples were collected from 500 cattle and 385 buffaloes belonging to backyard farmers from 24 villages in the province of Bukidnon, Mindanao, the Philippines. Strongyle nematode infections were studied on these samples by faecal egg counts and infective larvae differentiation. The effects of animal species and age on the prevalence and intensity of infections were studied. The overall prevalence of strongyle infection was 53% for cattle and 28% for buffaloes. The prevalence decreased with increasing age in both animal species. Faecal egg counts were significantly lower in buffaloes than in cattle. Adult animals had lower egg counts than calves. This age effect was most pronounced in buffaloes. Six genera of strongyle nematodes were identified from the faecal cultures in both animal species, Mecistocirrus, Haemonchus, Trichostrongylus, Cooperia, Bunostomum and Oesophagostomum. The distribution of larvae did not vary much with age.  相似文献   

18.
A survey on the prevalence and intensity of infection with gastrointestinal helminths of Dorper sheep in relation to age and weather factors was carried out on a ranch in Kajiado district, a semi-arid area of Kenya for a period of 13 months (May 1999 to May 2000). Faecal samples from lambs (3 months to 1 year), yearlings (1-2 years) and adult breeding ewes (2-4 years) were examined for helminth egg output and helminth genus composition at 3-week intervals. The results indicated that the prevalence of strongyle and tapeworms infections were highest for lambs, followed by the adult breeding ewes and then for the yearlings. In all age groups the proportions of infected animals were higher during the wet season than in the dry season for both nematodes and tapeworms. The mean strongyle egg counts were higher during the dry season for lambs, but were higher during the wet season for the other age groups. Mixed strongyle infections were detected, with Trichostrongylus (55 %), Haemonchus (28 %), Cooperia (10.5 %) and Oesophagostomum (6.5 %) being the most frequently encountered genera throughout the study period. The trends in strongyle faecal egg counts indicated the occurrence of hypobiosis, with resumption of development towards the end of the dry season and at the onset of the short rains in October and November. Self-cure was also observed in September and November in all age groups, although less frequently in lactating ewes. The prevalence and intensities of infection with gastrointestinal helminths in this area appeared to be influenced by the age of the host and weather factors.  相似文献   

19.
A survey was carried out to determine the prevalence and seasonal abundance of the egg and adult stages of nematode parasites of sheep and goats in the semi-arid zone of north-eastern Nigeria between January and December 2002. Faecal samples collected from 102 sheep and 147 goats and examined by the modified McMaster technique using saturated solution of sodium chloride as the floating medium revealed that 44 (43.1%) and 82 (55.8%) of the samples, respectively, contained at least one nematode egg type. Three nematode egg types were recovered with strongyle egg type (22.5% in sheep and 35.4% in goats) being the most prevalent followed, respectively, by Trichuris (5.9% in sheep and 4.1% in goats) and Strongyloides (4.9% in sheep and 4.1% in goats) egg types. Mean faecal egg counts were generally moderate in both sheep (1052+/-922 strongyle, 1000+/-590 Strongyloides and 380+/-110 Trichuris eggs, respectively, per g of faeces) and goats (2092+/-3475 strongyle, 958+/-854 Strongyloides and 683+/-512 Trichuris eggs, respectively, per g of faeces) and showed the same trend irrespective of the age or sex of the animals. The prevalence and counts of strongyle nematode eggs showed a definite seasonal sequence that corresponded with the rainfall pattern in the study area during the period. In both sheep and goats, counts of strongyle egg type increased with the rains and reached peak levels at about the peak of the rainy season in September. The other egg types encountered during the study did not show much variation with the season of the year. Out of the 45 sheep and 75 goats examined at necropsy, 27 (60%) and 39 (52%), respectively, contained adult nematode species. Seven genera of adult nematodes including Strongyloides, Trichostrongylus, Haemonchus, Trichuris, Cooperia, Oesophagostomum and Bunostomum species were encountered during the study. Bunostomum species were recorded only in sheep. Adult worm burdens were generally low and showed seasonal variation that corresponded with the rainfall pattern in the study area during the period. Haemonchus and Trichostrongylus species attained peak counts together in both goats (June) and sheep (August). Strongyloides species were encountered throughout the year in both sheep and goats irrespective of the season. Other genera of nematodes encountered occurred in very low numbers and did not allow any meaningful comparison of seasonal sequence. The results suggest that Haemonchus, Trichostrongylus and Strongyloides species may be the major contributors to small ruminant helminthiasis in the study area.  相似文献   

20.
Infections with gastrointestinal parasites (Eimeria spp., Cryptosporidium spp., Buxtonella sulcata, Fasciola hepatica, Moniezia spp. and trichostrongyles) and lungworms were monitored in five cow-calf herds in the north German lowlands. Estimated prevalences of infections with Eimeria spp. (predominantly Eimeria bovis) ranged between approximately 2 and 48%. The highest prevalences were found during late summer and autumn. On one farm Cryptosporidium spp. were detected in July and August (prevalence: 8.5 +/- 2.7% and 6.7 < 2.0%). The latter finding coincided with diarrhoea in many calves. Buxtonella sulcata was found during the entire study period in highly variable estimated prevalences ranging between zero and 73%, but without any obvious association with clinical disease. Fasciola hepatica was detected on four out of five farms at estimated prevalences of approximately 1-20%. Lungworm infections played a minor role in at least three of five study herds. The estimated prevalence of trichostrongyle infections rose from August until November whereas the intensity of infection did not change significantly. No difference in the intensity of infection could be detected between one farm on which infections with gastrointestinal nematodes were controlled only by moving the animals to an uninfected pasture in July, and three other herds on which strategic anthelmintic control was in place.  相似文献   

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