Efficacy of Nequinate against Thirteen Strains of Eimeria tenella and the Development of a Nequinate-Resistant Strain

Dk, McLoughlin; Mb, Chute

doi:10.2307/1589038

Cited by 9 publications

(2 citation statements)

References 7 publications

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“…Laboratory experiments have shown that resistance to the quinolones develops more readily than to drugs such as clopidol or amprolium. McLoughlin (1970) and McLoughlin & Chute (1971,1973a, for example, found that resistance to buquinolate, decoquinate and methyl benzoquate had already developed by the 6th and 4th passages respectively, whereas resistance to clopidol was not consistently present until the 17th passage (McLoughlin & Chute, 19736). In an earlier study McLoughlin & Gardiner (1968) had shown that a reduction in sensitivity to amprolium was not apparent until 15 passages in the presence of drug.…”

Section: Discussionmentioning

confidence: 96%

Eimeria tenella: experimental studies on the development of resistance to amprolium, clopidol and methyl benzoquate

Chapman

1978

Parasitology

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SummaryThe development of resistance by the Houghton strain of Eimeria tenella to the anticoccidial drugs amprolium, clopidol and methyl benzoquate has been studied. Resistance to amprolium and clopidol developed more readily in experiments where a large number of coccidia were exposed to the drug, either by increasing the number of oocysts in the inoculum or by increasing the number of birds in the group. When 45 birds were given 2·0 × 106 oocysts, resistance to amprolium and clopidol appeared after 6 and 7 passages respectively. In previous experiments, under similar conditions, resistance to robenidine developed after 6 passages, suggesting little difference between these three drugs. Resistance to amprolium and clopidol arose gradually as the concentration of drug was increased, but resistance to methyl benzoquate appeared in a single step from sensitivity to high-level resistance. Both amprolium and clopidol-resistant lines showed an 8-fold reduction in drug sensitivity. Attempts to measure the degree of resistance by calculation of the ED50 were unsuccessful.

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Section: Discussionmentioning

confidence: 96%

Eimeria tenella: experimental studies on the development of resistance to amprolium, clopidol and methyl benzoquate

Chapman

1978

Parasitology

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“…The reason cannot be that there is cross-resistance between pyridones and quinolones, since the lack of such cross-resistance has been clearly demonstrated McLoughlin & Chute, 1973;Fry & Williams, 1984). The possibility of transferred resistance to quinolones and clopidol appears to be discounted by the consistent failure to demonstrate this phenomenon by Joyner & Norton (1975, 1977, although the very low infection rates they used would certainly not have favoured interbreeding between the coccidial lines.…”

Section: Discussionmentioning

confidence: 98%

Analysis of the phenotypes in field populations ofEimeria acervulinaexpressing dual drug‐resistance to decoquinate and clopidol

Williams¹

1998

Avian Pathology

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Two strains of Eimeria acervulina were derived from samples collected from broiler houses where chicken flocks were being medicated with decoquinate (a quinolone); previous flocks in the same houses had been medicated with clopidol (a pyridone). The strains were found to be resistant to both drugs. In the laboratory, a dichotomous series of selection passages through chicks medicated with decoquinate or clopidol was used to demonstrate that both the original field populations of E, acervulina included at least some parasites that expressed simultaneous resistance to both drugs, rather than comprising subpopulations that were each resistant only to one drug or the other. This is the first time that a phenotypic analysis of the individuals in an eimerian population has been carried out. The relevance of this finding to the efficacy of Lerbek, a synergistic mixture of clopidol and methyl benzoquate (another quinolone), originally introduced in an attempt to delay the emergence of drug-resistant coccidia, is discussed. It is concluded that Lerbek would have been completely effective if resistance to neither of its components had already emerged before Lerbek was launched; some efficacy would also have been retained if resistance to only one of its components had already developed. However, if resistance to both components had already developed, the dual resistance of some individual parasites would have rendered Lerbek less effective than if all parasites were resistant only to one or the other of its components.

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Anticoccidial Drugs and Vaccines

Conway¹,

McKenzie²

2007

Poultry Coccidiosis

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Efficacy of Nequinate against Thirteen Strains of Eimeria tenella and the Development of a Nequinate-Resistant Strain

Cited by 9 publications

References 7 publications

Eimeria tenella: experimental studies on the development of resistance to amprolium, clopidol and methyl benzoquate

Eimeria tenella: experimental studies on the development of resistance to amprolium, clopidol and methyl benzoquate

Analysis of the phenotypes in field populations ofEimeria acervulinaexpressing dual drug‐resistance to decoquinate and clopidol

Anticoccidial Drugs and Vaccines

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