Studies on the sensitivity of field isolates of eimeria maxima to combinations of anticoccidial drugs

Hd, Chapman

doi:10.1080/03079458008418387

Cited by 26 publications

(19 citation statements)

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“…Whilst such mixtures of a quinolone and clopidol are highly potent against sensitive coccidia, poorer efficacy may be observed if the parasites are resistant to one or the other of the components . However, in contrast, Chapman (1980) found that if coccidia are sensitive to one component, Lerbek can retain efficacy in the field. This parallels the finding of White & Williams (1983) that a synergistic mixture of trimethoprim and sulphaquinoxaline could control a sulphaquinoxaline-resistant strain of E. acervulina.…”

Section: Discussionmentioning

confidence: 92%

“…The induction of resistance to either decoquinate or clopidol may also result in an increased sensitivity of electron transport to in vitro inhibition by the other drug (Fry & Williams, 1984). In view of these demonstrations of 'collateral sensitivity', it is surprising that field strains of coccidia dually resistant to clopidol and quinolones have been found to be so common (Williams, 1969;Millard, 1970;Jeffers, 1974a,b;Chapman, 1976Chapman, , 1980Mathis & McDougald, 1982;Chapman & Hacker, 1994).…”

Section: Discussionmentioning

confidence: 99%

“…It is unfortunate, therefore, that Kawazoe et al (1991) did not test the sensitivity of their field isolates to the individual components of Lerbek as well as to the drug mixture. However, in another study, Chapman (1980) showed that isolates resistant to Lerbek were also resistant to both its components.…”

Section: Discussionmentioning

confidence: 99%

“…In summary, although there are some conflicting points of evidence Chapman, 1980), it seems probable that Lerbek might well have been useful originally in delaying the emergence of dual resistance if both of its components had not been used in the field previously. However, this was not the case and isolates resistant to Lerbek have been shown to be common (Chapman, 1980).…”

Section: Discussionmentioning

confidence: 99%

“…Many populations of chicken Eimeria species resistant to two or more anticoccidial drugs have been isolated from the field (see Warren et al, 1966;Hodgson et al, 1969;Williams, 1969;Millard, 1970;Ryley & Betts, 1973;Jeffers, 1974a,b;Chapman, 1980;Mathis & McDougald, 1982). There are several potential ways in which coccidial populations might have acquired such traits:…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Discussionmentioning

confidence: 92%