用虫卵孵化试验对江苏羊场线虫抗药性的检测

用虫卵孵化试验对江苏羊场线虫抗药性进行了检测,测得其虫卵经半数抑制量ＥＤ５０为０．０６３３μｇ／ｍＬ丙硫苯咪唑,是敏感株的２０余倍。该方法操作方便,快速,结果客观,敏感,可以用于检测虫株抗药性的发生和抗药性动态变化规律分析,为寄生虫病防止抗药提供有效依据。     

河北省坝上地区绵羊消化道线虫对丙硫苯咪唑抗药性的检测

目的　为了查明绵羊消化道线虫对丙硫苯咪唑的抗药性。方法　应用粪便虫卵减少试验 (FECRT)对河北省坝上地区绵羊消化道线虫的抗药性进行了检测。结果　应用 5 m g/ kg丙硫苯咪唑对 5组绵羊进行驱虫的虫卵减少率分别为 4 3.9% ,38.4 6 % ,4 9.0 9% ,37.6 3%和 4 3.35 % ,驱净率分别为 2 0 % ,15 % ,15 % ,2 5 %和 10 %。结论　根据 FECRT 95 %置信域小于 90 % ,表明试验羊对该药有抗药性     

用虫卵孵化试验对江苏某羊场线虫抗药性的检测

用虫卵孵化试验对江苏某羊场线虫抗药性进行了检测,测得其虫卵孵化半数抑制量ＥＤ５０为０．０６３３μｇ／ｍＬ丙硫苯咪唑,是敏感株（０．００２６μｇ／ｍＬ丙硫苯咪唑）的２０余倍。该方法操作方便、快速、结果客观、敏感,可以用于检测虫株抗药性的发生和抗药性动态变化规律分析,为寄生虫病防止抗药性提供有效依据。     

虫卵孵化试验对某羊场关线虫抗药性的检测

为了解家畜寄生线虫对使用较久的驱虫药丙硫咪唑的抗药性情况，用虫卵孵化对江苏某羊场进行抗药性检测，测得内硫咪唑虫卵孵化半数抑制量ＩＤ５０＝０．０６０２μｇ／ｍＬ，约是敏感株（０．０１９４μｇ／ｍＬ）的３倍，但较世界兽医寄生虫促进协会提出的线虫抗药性临界值０．１μｇ／ｍＬ）小。虫卵减少试验也证实了该羊场不存在抗药性。因此该场羊寄生线虫尚无抗药性。     

虫卵孵化试验对山羊捻转血矛线虫左旋咪唑抗药性检测

在多次使用左旋咪唑后不能有效控制羊线虫病的羊场是否有线虫抗药性产生,我们用改良的虫卵孵化试验进行抗药性检测,在控制温度的条件下进行样品中的虫卵浓集和孵化,当虫卵发育到即将孵化时加入不同剂量的左旋咪唑让其暴露于不同药物浓度中继续孵化,适时终止孵化,并计算虫卵孵化抑制率。结果表明加入药物继续孵化6和9 h,药物浓度自然对数值与虫卵死亡机率值呈直线回归关系,ED50分别为0.295ug/mL和0.406 ug/mL,与文献报道左旋咪唑捻转血矛线虫敏感株的ED50接近,经虫卵减少试验证实该羊场未产生左旋咪唑抗药性。     

丙硫苯咪唑驱除绵羊胃肠道线虫的试验

丙硫苯咪唑驱除绵羊胃肠道线虫的试验宗泽群汪作民石剑华斯钦昭日格１昭日格图２内蒙古赤峰市畜牧兽医科学研究所赤峰０２４０３１；１巴林右旗幸福之路苏木兽医站；２巴林右旗巴彦他拉苏木兽医站据调查，赤峰地区六月龄以上的放牧绵羊胃肠道线虫感染率达１００％，强度在...     

宁夏羊胃肠道线虫对现行驱虫药的抗药性调查

采用粪便虫卵减少试验对宁夏地区所属灵武、贺兰、盐池、吴忠、中宁、中卫、永宁和银川市郊8个县（市）的12个绵羊场、6个山羊场进行了丙硫苯咪唑和阿维菌素抗药性的随机调查。结果表明：在用丙硫苯咪唑调查的10个绵羊场和6个山羊场中，虫卵减少率在95％以下和95％的置信域下限在90％以下的有山羊场2个、绵羊场2个，证明对丙硫苯咪唑有抗药性；1个绵羊场和1个山羊场的虫卵减少率是96．3％、95．9％，但95％置信域的下限在90％以下，具有抗药性可疑；山羊群中丙硫苯咪唑的抗药性为33．3％，绵羊群为20．0％。用同样的方法调查了1个山羊场和5个绵羊场（其中有4个羊场曾执行了丙硫苯咪唑的试验），查出1个山羊场和1个绵羊场对阿维菌素具有抗药性可疑，其虫卵减少率分别为97．3％和95．5％，置信域下限在90％以下。揭示了宁夏地区羊消化道线虫对现行驱虫药的抗药状态，为今后防治提供了依据。     

虫卵孵化试验对某羊场羊线虫抗药性的检测

为了解家畜寄生线虫对使用较久的驱虫药丙硫咪唑的抗药性情况, 用虫卵孵化试验对江苏某羊场进行抗药性检测, 测得丙硫咪唑虫卵孵化半数抑制量ＩＤ５０ ＝ ０－０６０ ２ μｇ／ｍＬ, 约是敏感株（０－０２０ ４ μｇ／ｍＬ） 的３ 倍, 但较世界兽医寄生虫促进协会提出的线虫抗药性临界值（０－１ μｇ／ｍＬ） 小。虫卵减少试验也证实了该羊场不存在抗药性。因此该场羊寄生线虫尚无抗药性。     

灭虫丁与丙硫苯咪唑驱除山羊胃肠道线虫对比试验

灭虫丁对牛羊寄生线虫有良好的驱虫作用，目前国内广泛应用的驱虫药丙硫苯咪唑也被公认为良好的驱除家畜寄生线虫的药物，为了便于使用者择优选用，我们进行了两种药物驱除羊寄生线虫的比较试验。     

黑龙江大山种羊场羊线虫抗药性的检测：粪便虫卵减少试验检查线虫 …

为了查明羊线虫对某种药物的抗药性,本试验用粪便虫卵减少试验对黑龙江大山种羊场羊线虫的抗药性进行了检测。结果表明该羊场的羊线虫对丙硫苯咪唑产生了抗药性;改用佳灵三特,羊佳２号进行治疗,获得了较为满意的结果。     

Comparison of in vitro methods and faecal egg count reduction test for the detection of benzimidazole resistance in small strongyles of horses

The objective of the study was to compare the in vitro egg hatch test (EHT), larval development test (LDT) and in vivo faecal egg count reduction test (FECR test) for the detection of benzimidazole resistance in equine strongyles. The presence of resistant or susceptible strongyle populations was determined in 25 stud farms using the in vivo FECR test and in vitro EHT. On the basis of the FECR values, resistance to fenbendazole was detected on 15 of the 25 farms (60%). The ED₅₀ value (anthelmintic concentration producing 50% inhibition of hatching) for suspected resistant populations varied from 0.110 to 0.222 g/ml thiabendazole (TBZ). Final LD₅₀ values (anthelmintic concentration inhibiting development of 50% of eggs into L₃ infective larvae) above 0.029 g/ml TBZ in the in vitro larval development test on samples from 11 stud farms revealed the presence of populations of small strongyles suspected of being benzimidazole-resistant.     

Effect of single and divided dose administration on thepharmacokinetics of albendazole in sheep and goat

The pharmacokinetics of albendazole were studied in sheep and goats following single and divided doseadministration at nematocidal and flukicidal dose rates. The disposition curves of the metabolites indicated increased uptake of the drug both in sheep and goats at divided dose schedules compared to single dose administration (P<0.05). The increased bioavailability of benzimidazole anthelmintics in divided dose schedules could improve their efficacy and help in extending their lives.     

A survey of the prevalence of emerging macrocyclic lactone resistance and of benzimidazole resistance in sheep nematodes in the lower North Island of New Zealand

AIM: To investigate the occurrence of emerging macrocyclic lactone (ML) resistance and of resistance to benzimidazole anthelmintics on a number of sheep farms in the North Island of New Zealand.

METHODS: On commercial sheep farms (n=30) in the Taihape district in the North Island of New Zealand, 30 animals were randomly allocated to one of two equal-sized groups and treated with either half of the recommended dose rate of ivermectin (half of 0.2 mg/kg), or with the full recommended dose rate of oxfendazole (4.5 mg/kg). The ivermectin treatment only was used on a further six properties. Faecal egg counts, accompanied by pooled larval cultures, were conducted on all samples at the time of treatment and 7–10 days later.

RESULTS: Resistance, as indicated by a <95% faecal egg count reduction (FECR) in both instances, was found to oxfendazole on 13/30 (43%) farms and to a half dose of ivermectin on 12/36 (33%) properties. For oxfendazole, such resistance was found to involve all six nematode genera whereas for ivermectin it was almost entirely restricted to Ostertagia and Cooperia infections.

CONCLUSIONS: These results indicate that emerging ML resistance may be more common on sheep farms in New Zealand than is generally realised. They also suggest that the half-dose ivermectin faecal egg count reduction test (FECRT) may offer some very practical benefits for parasite control by providing early warning of developing resistance to ML drenches and by signalling the possible imminent failure of these at their therapeutic dose rates. The sensitivity and reliability of this procedure may be further enhanced by the inclusion of larval cultures.     

Benzimidazole resistance of sheep nematodes in Norway confirmed through controlled efficacy test

Background

Resistance against benzimidazoles (BZ) has recently been detected in Norwegian sheep flocks through a large scale prevalence survey based on the faecal egg count reduction test (FECRT). The use of this test in combination with bulk larval culture only gives an indication of which gastrointestinal nematodes genera that are involved and these results have to be confirmed by a controlled efficacy test (CET) to get accurate information about resistant nematodes populations at species level. A CET was therefore performed with larvae from two flocks where BZ resistance was previously detected through FECRT.

Results

The latter test confirmed the previous results in both flocks. In flock A, the BZ resistant nematode population consisted solely of Haemonchus contortus, whereas H. contortus and Teladorsagia circumcincta comprised the resistant worm population in flock B.

Conclusions

Some discrepancies that have been recorded between FECRT and CET results regarding time for post-treatment coproscopical examination and a temporary suppression of faecal egg excretion are discussed.     

An evaluation of techniques used for the detection of anthelmintic resistance in nematode parasites of domestic livestock

In vitro and in vivo techniques used for the detection of anthelmintic resistance are reviewed in terms of their versatility, reliability, accuracy, cost and simplicity. The faecal egg count reduction test is considered the most suitable for field screening of resistance but the larval development assay is likely to prove a valuable adjunct in such investigations. Other in vitro techniques, such as egg hatch tests, larval motility and tubulin binding assays are recommended as suitable only for research investigations. Similarly, in vivo procedures such as the critical and controlled anthelmintic efficacy tests are considered to be appropriate only for specific research purposes because of the costs involved in such studies.     

Resistance to a triple combination of broad-spectrum anthelmintics in naturally-acquired Ostertagia circumcincta infections in sheep

Extract

To the veterinary practitioner, the challenge of managing a cat with renal failure is very real. The specific goals of therapy are to:     

Managing anthelmintic resistance: Modelling strategic use of a new anthelmintic class to slow the development of resistance to existing classes

AIM: To test the hypothesis that a single strategic treatment with a new class of anthelmintic could slow the development of resistance to existing classes of anthelmintic.

METHODS: An existing model was used to simulate nematode parasite dynamics and the development of anthelmintic resistance. Variations on a five-drench preventive programme of treatments for lambs, in which either zero, the first, third or fifth treatment was substituted with a different class of drug, were compared for the time to reach treatment failure (defined as efficacy <95%). The sensitivity to variations in the death rate of adult worms, that varied from 1 to 5%, and the dominance of resistance genes were also assessed.

RESULTS: Replacing one of the five treatments with a different class of anthelmintic almost always slowed the development of resistance, and was never worse than using the same drug for all treatments. Further, there were large differences in the relative time to treatment failure depending on which treatment was substituted. Changing the first treatment always had the least benefit, whereas changing the fifth treatment always had the greatest. This pattern was independent of the daily death rate of adult worms, and was not influenced by the dominance of resistance under treatment.

CONCLUSIONS: The results indicated that strategic substitution of a single treatment with a new class of anthelmintic, at the end of a series of preventive treatments to lambs using an existing class, could slow the further development of resistance to the latter. This strategic use of a new anthelmintic class has the potential to greatly extend the life of existing anthelmintics if these are still effective.