THE INCIDENCE OF THIABENDAZOLE RESISTANCE IN FIELD POPULATIONS OF HAEMONCHUS CONTORTUS ON THE NORTHERN TABLELANDS OF NEW SOUTH WALES

A survey was undertaken to assess the incidence of thiabendazole resistance in field populations of H. contortus in sheep flocks on 40 farms distributed throughout the sheep grazing area of the northern tablelands of New South Wales. Treatment with thiabendazole at 66 mg/kg reduced H. contortus ova output by 96-100% in 18 flocks while in the remaining 22 there was a range of responses down to levels where the anthelmintic was without apparent effect. Factors which may contribute to the high incidence of anthelmintic resistance are discussed and the possibility of widespread resistance occurring in other sheep raising areas is considered.     

THE ISOLATION OF A FIELD STRAIN OF HAEMONCHUS CONTORTUS IN QUEENSLAND SHOWING MULTIPLE ANTHELMINTIC RESISTANCE

SUMMARY Following the apparent failure of levamisole to control infections of Haemonchus contortus in sheep at Lawes in south eastern Queensland, a strain of this parasite was isolated at the Animal Research Institute, Yeerongpilly. This strain was used to infect sheep at Yeerongpilly and the Merrindale Research Station, Victoria where four experiments to classify the resistance pattern of the parasite were carried out. Resistance to thiabendazole was first suspected in 1969, and these experiments confirmed that resistance to this drug was still present. They also showed that a strong degree of resistance had been developed to both levamisole and morantel tartrate. Other benzimidazole anthelmintics and also the organophosphorus compound naphthalophos were only moderately effective against the original isolate but rafoxanide, nitroxynil and phenothiazine were almost 100% effective. Other highly effective chemicals were disophenol and closantel. After passaging the strain for four generations with both levamisole and albendazole, resistance to both naphthalophos and the newer benzimidazole anthelmintics increased dramatically. This is the first report of a field strain of H. contortus exhibiting resistance to benzimidazole, non-benzimidazole and organophosphorus anthelmintics.     

用虫卵孵化试验检查羊捻转血矛线虫的抗药性

用虫卵孵化试验对上海某羊肠的羊捻转血矛线虫的抗药性进行了检查,结果表明该羊肠有抗丙硫苯咪唑捻转血矛线虫存在,其５０％抑制虫卵有效孵化率（ＥＤ５０）为０．０８７,０．０１μｇ／ｍＬ,噻苯咪唑或０．０４８,０．０２μｇ／ｍＬ丙硫苯咪唑,而敏感株ＥＤ５０为０．００４５,０．００８５μｇ／ｍＬ噻苯咪唑或０．００６４,０．００２３μｇ／ｍＬ丙硫苯咪唑,抗药株ＥＤ５０值明量高于敏感株,改用羊佳１号进行治疗,取     

捻转血矛线虫离体培养的研究

本实验研究了:(1)三种人工合成培养基:M199、NCTC109、F_(12);(2)小牛脱纤维蛋白血(以下简称小牛脱纤血)、Filde’s试剂,Bovine hemin;(3)pH值等几种因素对离体培养中捻转血矛线虫(Haemonchou contortus)L_3发育至L_4的影响。结果表明:(1)在相同条件下,NCTC109和M199培养系中的L_3可发育至L_4晚期,F_(12)中L_3只发育至L_4早期;三种培养系中L_3发育至L_4的虫体数占存活虫体数的90％以上,以NCTC109中的发育率为最高,达100％。(2)小牛脱纤血、Filde’s试剂和Bovine hemin对L_3发育至L_4均有促进作用,虫体的存活率明显提高,晚四期幼虫的存活时间延长;小牛脱纤血和Filde’s试剂可使L_3至晚L_4的时间缩短。(3)pH 5.8～6.2时,L_3发育至L_4;速度明显减慢,发育率不到50％;pH 6.6～6.8时,L_3发育至L_4的同步性及发育率明显提高,以pH6.6为最佳。     

EFFICACY OF OXFENDAZOLE AGAINST AN OVINE ISOLATE OF BENZIMIDAZOLE RESISTANT HAEMONCHUS CONTORTUS

SUMMARY Eighteen parasite-free sheep were each infected with 6000±25 infective larvae of the AH-2, benzimidazole-resistant strain of Haemonchus contortus on each of experimental days -27, -15, -8 and -1. The sheep were subsequently randomized into 3 groups of 6 sheep each. Group 1 served as untreated controls; Groups 2 and 3 were treated orally with oxfendazole at dose levels of 5 mg/kg and 10 mg/kg body weight, respectively. At both dosage levels, oxfendazole was 100% effective against third, fourth, early fifth, and adult stages of the worms.     

苏云金芽孢杆菌毒素对羊捻转血矛线虫第三期幼虫毒力研究

从人工感染捻转血矛线虫山羊的直肠内取出粪便，在２５℃温箱中培养７ｄ，用贝尔曼法分离出第三期幼虫，将它们加入含苏云金芽孢杆菌以色列亚种伴孢晶体毒素的培养液中，置２５℃下培养。当伴孢晶体蛋白含量为４００ｇ／ｍｌ时，幼虫的死亡率２４ｈ后为９４．７％，４８ｈ后为９７．３％。毒素对幼虫作用２４ｈ与４８ｈ，其毒力无显著差异（Ｐ〉０．０５），并且作用２４ｈ与４８ｈ，其ＬＤ５０值伴孢晶体蛋白含量分别为８４．０５μ     

应用计算机和气象资料预测牧地上捻转血矛线虫（Haemonchus contortus）数量季节消长的研究

根据土源性寄生线虫体外发育期间受温度、湿度、季节和宿主动物影响的原理，采用电子计算机对上述多因子和捻转血矛线虫从卵发育到侵袭性幼虫的速度、数量进行分析回归，制定出模拟模型，设计出牧地上该种线虫从印发育到侵袭性幼虫数量的预测预报公式，将气象资料代入公式计算出的侵袭性幼虫季节消长曲线，与牧地上羊体内成虫数量消长曲线相互对比，初步显示可以采用气象资料通过计算机计算处理预测牧地上捻转血矛线虫侵袭性幼虫数量的季节动态，从而为防治措施的制订提供依据。     

THE ANTHELMINTIC EFFICACY OF NON-BENZIMIDAZOLE ANTHELMINTICS AGAINST BENZIMIDAZOLE RESISTANT STRAINS OF HAEMONCHUS CONTORTUS AND TRICHOSTRONGYLUS COLUBRIFORMIS IN SHEEP

The anthelmintic efficacy of 6 non-benzimidazole compounds and thiabendazole against standardised, benzimidazole resistant strains of H. contortus and T. colubriformis in sheep was determined using a controlled test. All compounds were administered intraruminally at their recommended therapeutic dose rates and 4 of the compounds were also assessed at half their recommended therapeutic dose rates. Levimisole at a dose of 6.4 mg/kg body weight, morantel at 4.4 mg/kg and 8.8 mg/kg, naphthalophos at 6.25 mg/kg and 12.5 mg/kg, rafoxanide at 7.5 mg/kg and phenothiazine at 530 mg/kg were 98% or more effective in removing adult infections of benzimidazole resistant H. contortus. Rafoxanide at 3.75 mg/kg, phenothiazine at 265 mg/kg and carbon tetrachloride at 0.05ml/kg were less effective, removing 80%, 73% and 72% respectively of the benzimidazole resistant H. contortus worm burdens. Against the benzimidazole resistant T. colubriformis levamisole at 6.4 mg/kg, and morantel at 4.4 mg/kg and 8.8 mg/kg removed 99%, 68% and 86% respectively of the adult infections. All other anthelmintics had little or no efficacy at the dose rates tested. Thiabendazole at 44 mg/kg had no significant effect against these strains of H. contortus and T. colubriformis. Several non-benzimidazole anthelmintics have shown high efficacy in this experiment and should be suitable for treating infections with benzimidazole resistant H. contortus. Of the anthelmintics tested, only levamisole and morantel show high efficacy against benzimidazole resistant T. colubriformis.     

INSECTICIDE RESISTANCE IN FIELD STRAINS OF LUCILIA CUPRINA

A survey was conducted in 1977–78 to determine the level of insecticide resistance in field strains of Lucilia cuprina from a wide area of Queensland. Discriminating dose data showed that all 19 strains tested were resistant to diazinon, dichlofenthion, fenthion-ethyl and chlorfenvinphos, but resistance factors in all strains were low, the highest being 18.9 for diazinon. Six strains showed no resistance to butacarb.
A strain collected in 1967 and selected with diazinon for 117 generations, attained resistance factors for organophosphorus compounds far higher than those of the present field strains.