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1.
The targeted application of anthelmintic treatments represents one of the current available solutions to slow down the development of anthelmintic resistance within worm populations. Within an experimental flock of dairy goats, control of gastrointestinal parasitism by such selective treatments, targeting the most receptive animals within a flock, was previously found to be effective and to have no detrimental consequences on milk production. The objectives of the current study were to verify the validity of this method in farm conditions. Eleven dairy goat farms from three main areas of production in France were surveyed for 2 years. In six farms, the survey was prolonged for a third year. During year 1, systematic treatments were applied during the grazing season whereas in year 2 and or year 3, treatments were given exclusively to the goats in first lactation and to the multiparous ones with the highest potential of milk production. The level of nematode infection was measured four times per year through individual coproscopical examinations and the mean annual production of milk was recorded. No significant changes in egg excretion nor in milk production were noticed in any farm during years 2 or 3 after switching from the systematic to the selective mode of treatments. These results confirmed that targeted application of anthelmintics might represent a way to combine the control of trichostrongyles and the prevention of anthelmintic resistance.  相似文献   

2.
This study was undertaken to establish whether anthelmintic resistance was present in nematode parasites of horses in Denmark. Sixteen horse farms were selected for faecal egg count reduction (FECR) tests to measure the efficacy of the anthelmintic used. Resistance to benzimidazole anthelmintics was found on 13 of the 16 farms, with FECR values ranging from 80.0% to -101.3%. On the remaining 3 farms FECR was 100.0%, 99.3% and 97.2%. Results of a questionnaire study on anthelmintic usage, parasite control measures and management practices showed that horses in this study were treated on average 7.1 times/year. Horse owners changed between preparations of drugs but almost only within the same class of anthelmintics. Nine owners gave an anthelmintic treatment to purchased horses before they were introduced on the farm. On 14 farms, the same paddock was grazed every year and the average stocking rate was estimated to be 2.4 horses/ha. Strategies to avoid development of anthelmintic resistance are discussed and recommendations of parasite control on horse farms are presented.  相似文献   

3.
Worm control practices and anthelmintic usage in 177 cattle farms in Iringa district in the southern highlands of Tanzania was determined through a questionnaire survey. A total of 76 traditional, 92 small-scale dairy and 9 large-scale dairy cattle farms were included in the survey. Results indicated that 87.7% traditional, 97.8% small-scale dairy and 100% large-scale farmers relied solely on the use of anthelmintics, 2.7% traditional farmers used traditional medicines while 9.6% traditional farmers had not any form of worm control practice. Worm infection was ranked the second most important constraint of productivity in cattle in the three production systems. Most farms (57.6% traditional, 35.8% small-scale dairy, 66.7% large-scale dairy) used anthelmintics with a combination of levamisole and oxyclozanide. Benzimidazoles were used only in traditional (25.4%) and small-scale dairy (32.1%) farms while nitroxynil (Trodax) was mostly used in large-scale dairy farms (33.3%). Generally, 40% of farmers treated three or four times a year and the frequency in some farms was surprisingly high for resource poor small-scale farmers. The frequency of anthelmintic treatment was mostly the same regardless of the management system. Treatments in most farms depended on availability of money and drugs and not the epidemiology of parasites. A significant proportion (46.3%, P=0.007) of farmers especially in rural areas failed to follow their pre-planned treatment schedules due to lack of money (86%) and unavailability of drugs (6.6%). Many farmers (58.9%) had used the same type of anthelmintic for four or more consecutive years and 85.3% of them would continue with the same anthelmintic. Farmers in all management systems mostly purchased anthelmintics from private veterinary drug shops and about 43% traditional and 33.3% small-scale dairy farmers mostly in rural areas obtained anthelmintics from village extension officers. Despite the fact that all farmers were aware of worm infection and the associated signs in cattle, 42.5% had poor knowledge on the source of worm infection. Small-scale dairy farmers allowed only a 1-day withdraw period for milk regardless of the type of anthelmintic used and there was no milk and slaughter clearance in traditional farms. It was concluded from this study that worm control in Iringa faces serious constrains and that education of farmers and farm hands is not adequate. Moreover, poor quality control and high price of potent anthelmintics, few extension workers, low income and low education among farmers contributed significantly to erratic worm control practices and anthelmintic usage in peri-urban and rural areas.  相似文献   

4.
A survey was undertaken to assess the prevalence of anthelmintic resistance in sheep nematode populations on 40 commercial farms distributed throughout the central tablelands of New South Wales. Representatives of the 2 major groups of broad spectrum anthelmintics with different modes of action (thiabendazole and levamisole) were used at the manufacturer's recommended dose rates. Efficacy was assessed on the basis of the reduction in faecal strongyle egg counts 7 days after treatment. An efficacy of less than 90% using both anthelmintics was obtained on 4 farms. Thiabendazole had an efficacy of less than 90% on a further 21 farms and levamisole had an efficacy of less than 90% on an additional 4 farms. There was no evidence of anthelmintic resistance on 8 farms, while the remaining 3 had insignificant parasite burdens. Based on larval cultures from faeces, Ostertagia and Trichostrongylus were the most significant species in resistant populations. Haemonchus burdens were sporadic and levels of resistance relatively low. Nematodirus burdens were widespread but no evidence of resistance was detected.  相似文献   

5.
Twenty-eight farms in 7 shires in south western Victoria were selected and tested for presence of benzimidazole-resistant nematodes between November 1979 and June 1981. Mean faecal egg counts of sheep were less than 100 strongyloid eggs/g on 11 farms. Faecal egg count reduction tests were conducted on the remaining 17 farms and thiabendazole was less than 90% efficient in reducing egg counts in sheep from 5 (29%) of these farms. Thiabendazole-resistant Teladorsagia circumcincta were identified at necropsy of experimentally infected treated sheep. In further studies a survey of 104 farms was conducted in the Mount Rouse and Dundas shires of western Victoria in 1981 and 1982 respectively to determine the prevalence of anthelmintic resistance in these shires. Mean faecal egg counts among weaner sheep in the winter-spring of both years were less than 100 eggs/g which indicated low levels of parasitic nematode populations. A faecal egg count reduction test was conducted on 10 farms and thiabendazole was less than 90% efficient on 3; levamisole was greater than 90% efficient in all 10 tests. Most of the surveyed farms carried Merino or Merino crossbred sheep at 10 to 15 dry sheep equivalents per ha and weaners were treated with anthelmintics 3 to 6 times per year. Management procedures based mainly on anthelmintic therapy were effective in controlling nematode populations in weaner sheep, although many producers alternated between different groups of anthelmintics within the same year contrary to current recommendations for long-term preservation of anthelmintic efficacy. It was concluded that anthelmintic resistance was not of practical importance to the majority of sheep producers in the region.  相似文献   

6.
The occurrence of anthelmintic resistance in strongyles was investigated in 440 horses on 90 farms in Switzerland. The egg hatch assay suggested that benzimidazole (BZ)-resistance was present in 40 of 82 farms (49%). Faecal egg count reduction after pyrantel-treatment was above 96% in 14 of 15 farms. In the remaining farm the efficacy was only 80%. Ivermectin efficacy was investigated on 5 farms and the efficacy was recorded at 98-100%. Faecal cultures undertaken after treatment revealed almost exclusively larvae of the family Cyathostominae. Data about management practices, pasture hygiene and anthelmintic usage were obtained with a questionnaire. Horses were treated on average 3.5 times per year. In 75% of the farms BZ were a component of the seasonal treatment schedule. Only the use of BZ had a significant correlation with the presence of BZ-resistance (P < 0.01). Recommendations for the control of equine strongyles should include measures that minimize the risk of resistance developing against remaining effective anthelmintics.  相似文献   

7.
Although the molecular bases of resistance to anthelmintic families have been intensively studied, the contributing factors for the development of anthelmintic resistance are less well known. Clear recommendations must be given to farmers in order to delay the onset of anthelmintic resistance. Until now, the main advice has concerned the reduction of treatment frequency in order to slow down the spread of resistance. Anthelmintic resistance development depends mostly on an efficient selection pressure. This means that a high treatment frequency is neither necessary nor sufficient to select for resistance. The contribution of resistant worms, which have survived an anthelmintic treatment, to the subsequent generation is the key factor that controls resistance spread. This point is illustrated by five surveys conducted on sheep and goat farms from France and Morocco. In the 52 farms studied, less than three anthelmintic treatments were given each year. Three characteristics of breeding management can be identified in the build up of anthelmintic resistance: (1) the introduction of resistant worms through the purchase of sheep/goats or the use of common pastures, grazed by several herds/flocks, (2) under-dosing of hosts and the repeated use of one class of drugs, (3) the size of the population in refugia (infective larvae on pastures) at the time of the treatment. The role played by these breeding management factors in selecting for resistance is discussed. The most efficient way to limit the increase of anthelmintic resistance remains the reduction of the selection pressure by drugs, and optimal timing to maximise their efficacy.  相似文献   

8.
The present study included 19 stud farms, including 243 horses, that were investigated for the occurrence of anthelmintic resistant cyathostomes. The number of horses on the farms varied from nine to more than 100, and horses of all ages were included. A minimum of seven horses were used for faecal egg count reduction (FECR) tests. The anthelmintics included were: fenbendazole (paste formulation), ivermectin (paste formulation) and pyrantel (powder). Resistance to benzimidazoles was detected on 14 farms, with FECR values ranging from 65.1 to 86.3%. Larval cultures after fenbendazole treatment revealed exclusively cyathostome larvae. Ivermectin was tested on eight farms and proved to be effective on all. Pyrantel was tested on two farms and FECR test indicated high efficacy (92-97%). Egg hatch assay (EHA) results showed that mean concentrations of thiabendazole that inhibited hatching in 50% of the eggs (ED(50)) in resistant populations were over 0.1 microg ml(-1). The results of our study suggest widespread resistance to fenbendazole in equine cyathostomes in Slovakia, and possible strategies to delay anthelmintic resistance are discussed briefly.  相似文献   

9.
Six hundred and sixty-five New England sheep producers responded to a postal survey on management practices, anthelmintic use, and the perceived failure of anthelmintics to control nematodes. Although the average farm had 34.8 lambs and 29.8 stock sheep, 59.8% and 50.3% of the total number of lambs and stock sheep were on 16.5% of the farms, which had greater than 50 lambs. About 54% of the lambs were born in January and February. Spring markets and confinement rearing were popular, as only 45.7% of the total lambs grazed summer pasture. Most producers (81.5%) treated their stock sheep (and lambs) for nematodiasis 2 to 4 times per year (mean, 3.3), generally before lambing, before pasturing, midsummer, and/or before breeding. Only 27.5% of the producers indicated distinct drenching management for grazing lambs. There was little use of preventive control, such as spring prophylaxis (0.5%) or dosing in midsummer and moving animals to safe pasture (2.9%). More than one anthelmintic class was used on 59.6% of the farms, with a mean of 1.88 anthelmintics per farm. Though 53.7% of the producers had a policy of alternating anthelmintic classes within a year, only 11.6% alternated anthelmintics annually. Levamisole and thiabendazole were the anthelmintics most frequently used by 81.8% and 61.6% of producers, respectively. However, 26.5% and 16.2% of the farms used fenbendazole and phenothiazine, respectively. The presence of gastrointestinal nematode resistance to anthelmintics was suggested, because 35.4% of the producers had discontinued using at least one anthelmintic that they considered to be ineffective. The anthelmintic that was most frequently discontinued was thiabendazole.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

10.
During the past two decades anthelmintic resistance in equine parasites has been found in the group of small strongyle species (cyathostomins) and in the ascarid species Parascaris equorum. The ubiquitous nature and possible severe consequences of disease with these nematodes make them the prime targets of current worm control programmes. Traditional control strategies mainly rely on the strategic application of anthelmintics, currently represented by three major drug classes: benzimidazoles (BZ), the tetrahydropyrimidine pyrantel (PYR) and macrocyclic lactones (ML). Following decades of routine and frequent anthelmintic applications, many cyathostomin populations on horse farms in industrialised countries must be considered as resistant to BZ anthelmintics. However, to date no published cases of cyathostomin disease specifically associated with anthelmintic resistance were reported. Possibly this is due to the generally subclinical and unspecific symptoms associated with cyathostomin infections. Nevertheless, exclusive reliance on the ML drug class may increase the threat of clinical disease due to drug-resistant cyathostomins. More recently, P. equorum has been reported as having developed resistance against ivermectin and moxidectin, two representatives of the ML-class. These anthelmintics are currently the most frequently used drug class in horses. This nematode species is mainly found in foals and in younger horses due to the development of immunity following exposure to infection. Infection with P. equorum can result in clinically drastic consequences such as obstruction and/or penetration of the small intestine, the latter usually leading to death. In conclusion, on horse farms the efficacy of anthelmintic treatments should be examined routinely for each drug class. Several factors can influence the rate at which anthelmintic resistance develops; high frequency of treatment being one of the most important. Modern control strategies should therefore attempt to significantly reduce anthelmintic treatments. Several pasture and farm management practices found to be negatively associated with nematode and anthelmintic resistance prevalence will be discussed in the review presented here.  相似文献   

11.
Resistance to anthelmintics in nematode parasite of the digestive tract is a major concern in small ruminants and particularly in goats. One possible solution to limit the development and spread of resistance is to give treatments on a selective basis, i.e. by targeting the most susceptible animals within a flock rather than treating all the animals. In dairy goats, epidemiological studies have shown that, within a flock, goats in first lactation and the multiparous ones with the highest level of milk production were highly receptive to parasite infection. The objective of the study was to assess whether selective treatments could achieve a level of control of nematodes similar to systematic drenching. A similar experimental design was applied for two successive years. An experimental flock of 120 dairy goats was divided into two groups. All the goats from group SYS (systematic treatment) were drenched at mid-grazing season (July). In contrast, anthelmintics in group SEL (selective treatment) were restricted to the goats in first lactation plus the high producers. Overall, these treated goats represented 48% of the flock in year 1 and 66% in year 2. After treatments, both groups grazed on separate pastures. Parasitological and pathophysiological measurements were performed monthly. The results indicate a similar level of egg excretion in the two groups. The pathophysiological parameters (pepsinogen and phosphate concentrations) were also similar in the two groups, as well as the milk production for the 2 years. These results suggest that a targeted use of anthelmintics may allow efficient control of gastrointestinal nematodes whilst resulting in a predicted reduction in the selection pressure for the development of anthelmintic resistance.  相似文献   

12.
AIM: To report current farmer opinions and farming practices relating to control of gastrointestinal nematodes and anthelmintic resistance on sheep farms in New Zealand. METHODS: An interview-based cross-sectional study of grazing management and anthelmintic usage was conducted by veterinarians on 80 randomly selected sheep farms in New Zealand. RESULTS: Useable data were returned by 74/80 (92%) farmers who participated in the study. However, despite contacting 400 farmers the target sample size of 100 farms was not reached. The results indicated that only 31% of farms had previously tested for drench resistance, that effective quarantine-drenching of imported stock was not always carried out, and that farmers were more likely to integrate cattle than ewes into their grazing management of lambs. Furthermore, the number of drenches given to lambs had changed little in 25 years. The use of faecal egg counting by farmers has increased. CONCLUSIONS: Dependence on anthelmintics continues to be high on sheep farms in New Zealand. Whilst the number of drench treatments has changed little, there is more widespread use of persistent or long-acting treatments. Farmers need to be encouraged to monitor the resistance status of nematode populations on their farms and use this information to develop strategies aimed at maintaining susceptible alleles within the parasite populations and conserving the efficacy of existing drug families.  相似文献   

13.
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   

14.
AIM: To report current farmer opinions and farming practices relating to control of gastrointestinal nematodes and anthelmintic resistance on sheep farms in New Zealand.

METHODS: An interview-based cross-sectional study of grazing management and anthelmintic useage was conducted by veterinarians on 80 randomly selected sheep farms in New Zealand.

RESULTS: Useable data were returned by 74/80 (92%) farmers who participated in the study. However, despite contacting 400 farmers the target sample size of 100 farms was not reached. The results indicated that only 31% of farms had previously tested for drench resistance, that effective quarantine-drenching of imported stock was not always carried out, and that farmers were more likely to integrate cattle than ewes into their grazing management of lambs. Furthermore, the number of drenches given to lambs had changed little in 25 years. The use of faecal egg counting by farmers has increased.

CONCLUSIONS: Dependence on anthelmintics continues to be high on sheep farms in New Zealand. Whilst the number of drench treatments has changed little, there is more widespread use of persistent or long-acting treatments. Farmers need to be encouraged to monitor the resistance status of nematode populations on their farms and use this information to develop strategies aimed at maintaining susceptible alleles within the parasite populations and conserving the efficacy of existing drug families.  相似文献   

15.
High perinatal mortality, low milk yields and occasional ewe deaths were investigated in a Dorper sheep flock in Southern Germany. Parasitic gastroenteritis due to Trichostrongylus spp. associated with severe weight loss despite regular anthelmintic treatments of the flock was identified as the underlying cause. A faecal egg count reduction (FECR) test revealed zero reduction after treatment with ivermectin or albendazole, respectively, and a FECR of 57.9% following treatment with levamisole. These results indicate a lack of, or considerably reduced efficacy of substances from all three classical groups of anthelmintics and demonstrate that triple anthelmintic resistance is also present in Germany. The introduction of resistant worm populations with imported livestock, excessive use of anthelmintic drugs and under-dosing of goats have possibly led to the problem in the flock described. Veterinary advice on anthelmintic treatments and responsible parasite control programmes are therefore crucial in small ruminant flocks.  相似文献   

16.
The negative effects of nematodes in small ruminants can be reduced by use of dewormers but their effectiveness is increasingly limited by the emergence of anthelmintic resistance. The efficacy of benzimidazole (BZ) anthelmintics in the Philippines was estimated by an in vitro larval development assay using worm eggs recovered from faeces collected from goats and sheep. Two hundred and eighteen farms were selected to represent areas of the country with high goat and sheep populations and the full range of farm sizes, from smallholders with just a few animals to commercial and institutional farms with several hundred. Initial surveys of worm control advisers indicated that BZs have been in continuous widespread use for up to 20 years with little use of other chemical groups. A larval development assay (LDA: DrenchRite) was modified for use with BZs alone to allow up to five samples to be analysed on a single microtitre plate. The assay was validated by comparison with the faecal egg count reduction test (FECRT). The dominant nematode genera were Haemonchus and Trichostrongylus with small numbers of Oesophagostomum. The range of BZ efficacy estimated from the LDA results was 0-100% and the distribution of efficacy levels was continuous, with mean efficacy of 82 and 64% for goats and sheep, respectively. There were significant associations between efficacy and parameters measured to characterize the sampled farms: size of animal management group, FEC of sample, recent importation of stock and no access to common grazing were all correlated with decreased efficacy. Likewise, low efficacy was associated with reported frequency and number of years that BZ drenches had been used. The LDA was found to be highly suited to estimate efficacy in nematode populations from small farms where performance of a FECRT for even one chemical would be impractical. Using a larval development assay, we have demonstrated a wide efficacy range for BZs against nematodes from all sizes of goat and sheep farms in the tropics.  相似文献   

17.
The prevalence of anthelmintic resistance on 27 sheep farms in Slovakia was investigated in 2003 and 2004 using the faecal egg count reduction test (FECRT) according to the WAAVP guidelines. Resistance to albendazole was detected on one farm (3.7%) and suspected on two farms (7.4%) out of 27 sheep flocks. Resistance to ivermectin was tested on 26 farms. On six (23.1%) farms, results indicated the presence of ivermectin resistance. Resistance to ivermectin was suspected on eight farms (30.8%). However, it is also possible that generic ivermectin anthelmintics used in survey have a lower efficacy against sheep nematodes.  相似文献   

18.
In 2004-2006, 322 brood horses from 11 horse farms were examined using the faecal egg count reduction test (FECRT) to determine the presence and distribution of anthelmintic resistance in strongylids in Ukraine. The anthelmintic drugs "Albendazole-7.5" (7.5mg of albenazole, Ukraine) at a dose of 5mg per kg body weight and "Univerm" (0.2% aversectin C, Russia) at a dose of 0.5mg per kg body weight were used. Seventy-one horses from six farms were examined in vivo to investigate the influence of anthelmintic treatment on the gastrointestinal strongylid community structure. Horses were treated with anthelmintics; faecal sampling (200 g in each sample) for strongylid expulsion was performed 24, 36, 48 and 60 h after treatment; and all strongylids expelled (25,292 specimens) were collected and identified. Fourteen horses from the Dubrovsky horse farm were also examined to determine the benzimidazole-resistant cyathostomin species; 5208 specimens of benzimidazole-resistant cyathostomins were collected and identified. According to the FECRT data, benzimidazole resistance in strongylids was observed only at the Dubrovsky horse farm (FECRT=68.7%). No resistance to macrocyclic lactones in strongylids or in Parascaris equorum was observed. Twenty-nine strongylid species were found in horses from six horse farms. The number of species per horse ranged from 4-9 (5.8+/-1.5) to 10-20 (14.4+/-2.9) and depended on horse anthelmintic treatment strategies. From 4 to 13 strongylid species predominated (prevalence>66.7%) in the strongylid community. Eleven cyathostomin species (Cylicocyclus nassatus, C. ashworthi, C. leptostomum, Cyathostomum catinatum, C. pateratum, Cylicostephanus calicatus, C. longibursatus, C. goldi, C. minutus, Coronocyclus coronatus and C. labiatus) were found to be resistant to benzimidazoles at the Dubrovsky horse farm. Ten of these were the dominant species in the strongylid community; only C. labiatus was a rare species (prevalence 29.4%). Species richness and species diversity were significantly higher in horses from farms without treatment or with occasional treatments than from farms with regular treatments. The shape of the prevalence frequency distribution of strongylid species from farms with regular treatments was bimodal ("core" and "satellite" mode). This distribution was multimodal at farms without treatment or with occasional anthelmintic treatments. The results of the current study indicated the possibility of the further spread of anthelmintic resistance on horse farms in Ukraine and the necessity of monitoring the development of resistance in horse parasitic nematodes.  相似文献   

19.
In this study the helminthiasis and anthelmintic effectiveness in ewes and lambs were evaluated in a semiarid region of Brazil. Twelve sheep farms were investigated using semi-structured questionnaires and fecal egg count (FEC) reduction test was employed to analyze the profile of anthelmintic resistance. Groups of at least 10 animals with FEC ≥ 300 were selected. After 12 h of fasting, homogeneous groups of lambs or ewes were treated with albendazole, levamisole moxidectin, or oxfendazole and control groups were not treated. Feces were collected before treatments and 14 days after, and larvae genera were identified after cuprocultures in both periods. Extensive grazing was the predominant creation system, using hybrid Santa Ines animals. The separation by age was promoted in 75% of herds; however, maternity pickets there were only in three farms. The strategic treatments were performed only in 8.4% of sheep farms and 16.6% used the anthelmintic efficacy test and alternated anthelmintic classes after 1 year. The initial FEC means for lambs were significantly higher than ewe FEC averages. For lamb tests, moxidectin and levamisole showed higher efficacy (p ≤ 0.05) than benzimidazoles. For ewe tests, moxidectin and levamisole showed efficiencies >75%. Haemonchus spp. and Trichostrongylus spp. were the most frequent nematodes before treatments and the genus Haemonchus was the most prevalent after anthelmintic treatments (p < 0.05). Variations of anthelmintic susceptibility were observed for categories and herds evaluated, which emphasizes the importance of the effectiveness tests for the choice of anthelmintics for ewes and lambs.  相似文献   

20.
AIM: To establish the prevalence of anthelmintic resistance in parasitic nematodes on a random sample of beef cattle herds in the North Island of New Zealand. METHODS: A cross-sectional prevalence study was conducted using a standardised faecal nematode egg count (FEC) reduction (FECR) test (FECRT) for ivermectin, levamisole and albendazole on 60 calves on each of 62 farms in the North Island chosen at random from farms that conformed with the selection criteria. Resistance to an anthelmintic was inferred when there was <95% reduction in FEC 7-10 days after treatment. Larval cultures were performed for all control groups and for treated groups for which resistance was evident. RESULTS: Of the farms that completed the FECRT, 4/61 (7%) showed > or =95% reduction in FEC for all anthelmintics tested. Resistance to ivermectin was evident on 56/61 (92%) farms, to albendazole on 47/62 (76%) farms, and to both ivermectin and albendazole on 45/61 (74%) farms. Resistance to levamisole was evident on only 4/62 (6%) farms. The parasites most prevalent in resistant populations cultured were Cooperia spp. On 45/61 (74%) farms where Cooperia spp were present in sufficient numbers, resistance to both ivermectin and albendazole was evident. No cases of levamisole-resistant Cooperia spp were detected. Resistance of Ostertagia spp to ivermectin was evident on 4/45 (9%) farms, to albendazole on 15/46 (35%) farms, and to levamisole on 4/46 (9%) farms. CONCLUSION: Anthelmintic resistance in parasitic nematodes of cattle is common in the North Island of New Zealand. Beef farmers need to be aware of the risks posed by anthelmintic resistance, and routine FECR testing is recommended to ensure optimal productivity and to guide decision-making when purchasing anthelmintics to be used on-farm.  相似文献   

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