Eimeria tenella: Sensitivity of Recent Field Isolants to Monensin

Tk, Jeffers

doi:10.2307/1589519

Cited by 18 publications

(6 citation statements)

References 14 publications

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“…A reduced sensitivity of Eimeria to some anticoccidials such as ionophores has been suspected for years (Chapman, 1982;Li et al, 2004;Stephan et al, 1997). The commercial success of ionophores indicates that the challenge conditions in the field are compatible with their different efficacy profiles (Bafundo and Jeffers, 1990;Chapman, 1984;Jeffers, 1978).…”

Section: Discussionmentioning

confidence: 99%

Efficacy and Characteristics of different Methods of Coccidiosis Infection in Broiler Chickens

Elmusharaf¹

2010

American Journal of Animal and Veterinary Sciences

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Problem statement: Different methods of experimental infection of broiler chickens withEimeria species have been described in the literature. These methods had not been compared and contrasted so as to contribute to the selection of the most appropriate model of coccidiosis in broiler chickens. Identifying such a model was important to speed up the screening of potential coccidiostatics. Approach: In five different experiments with broiler chickens, we used different methods of infection with Eimeria species. In this paper the different methods and the results have been evaluated. Results: Administration through gavage into the crop of relatively low doses of either Eimeria tenella alone, or in combination with Eimeria acervulina and Eimeria maxima, did not influence body-weight gain and feed intake, but did induce intestinal lesions and faecal shedding of oocysts. The administration of an identically high number of sporulated oocysts in the form of a mixture of the three Eimeria species, either through a single dose by gavage or through the litter, produced similar lowering effects on body-weight gain or feed intake, similar degrees of severity of intestinal lesions and similar rates of faecal oocyst shedding. Conclusion: Depending on the variables considered of interest, the present data may indicate the most appropriate model. The model using infection with oocysts through the litter may optimally mimic the field situation in combination with controlled conditions and allowing experimental flexibility and a high number of experimental units within the research facility.

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Section: Discussionmentioning

confidence: 99%

Efficacy and Characteristics of different Methods of Coccidiosis Infection in Broiler Chickens

Elmusharaf¹

2010

American Journal of Animal and Veterinary Sciences

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“…In the 1970s and the years that followed it became extremely important to establish whether resistance had developed to ionophorous anticoccidial drugs because these compounds became the most widely used anticoccidials in the field. In studies in chickens, Jeffers examined the sensitivity to monensin of field isolates of E. acervulina, E. maxima, and E. tenella obtained from monensin-medicated flocks (Jeffers, 1978c(Jeffers, , 1978d. No monensin-resistant isolates could be identified at that time.…”

Section: Biographymentioning

confidence: 99%

Thomas K. Jeffers: pioneer of coccidiosis research

Chapman

2012

Avian Pathology

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Thomas K. Jeffers has made many significant contributions to our understanding of the biology of the parasite Eimeria, the cause of coccidiosis in poultry. His work has had direct practical application for the control of this widespread disease. Topics discussed include Jeffers' pioneering work concerned with genetics of the host response to infection, the nature of biological and immunological intraspecific variation, drug resistance and discovery, field surveys of resistance, and his most recognized achievement-the demonstration that the lifecycle of coccidia may be altered by artificial selection. Parasites so modified are attenuated but retain their immunogenicity, a discovery that has led to the development of live vaccines that are inherently non-pathogenic. This article provides a brief biography and describes the contributions that Jeffers has made to our knowledge of coccidiosis.

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“…The methods used for isolation and propagation of the turkey coccidia from litter samples were similar to those previously described for studies on chicken coccidia (Jeffers, 1978a). Cultures were isolated from litter samples taken from monensin-medicated turkey flocks in Canada and from US turkey production houses in which monensin has never been used.…”

Section: Isolation and Propagation Of Coccidiamentioning

confidence: 99%

“…The monensin sensitivity of the turkey coccidia was evaluated using techniques described by Jeffers (1978a) for testing monensin sensitivity of chicken coccidia. Infective doses in the tests reported ranged from 40 X 10 3 to 3 50 X 10 3 oocysts/bird.…”

Section: Evaluation Of Monensin Sensitivitymentioning

confidence: 99%

Monensin Sensitivity of Recent Field Isolates of Turkey Coccidia

Jeffers

Bentley

1980

Poultry Science

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The efficacy of monensin at concentrations of 60 and 100 ppm was evaluated against 22 isolates not exposed to monensin and 16 monensin-exposed field isolates of coccidia obtained from US and Canadian turkey flocks, respectively. Isolates not previously exposed to monensin were effectively controlled by monensin. However, 7 monensin-resistant isolates (predominantly Eimeria meleagrimitis) were independently isolated from turkey flocks in Ontario, Canada where monensin was being used as an anticoccidial. Subsequent sensitivity evaluations of two of these isolates revealed cross-resistance to lasolocid, narasin, and salinomycin. Evaluation of the stability of monensin resistance in one isolate suggested that monensin sensitivity was not restored after 10 generations of relaxed selection. Although the extent of monensin resistance among field isolates of turkey coccidia is unknown, these results provide the first unequivocal characterization of monensin resistance in field isolates of coccidia. Contrarily, after more than eight years of intensive use of monensin as an anticoccidial in US broiler production facilities, this type of resistance to the polyether antibiotic anticoccidials has not been encountered in chicken coccidia.

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Eimeria tenella: Sensitivity of Recent Field Isolants to Monensin

Cited by 18 publications

References 14 publications

Efficacy and Characteristics of different Methods of Coccidiosis Infection in Broiler Chickens

Efficacy and Characteristics of different Methods of Coccidiosis Infection in Broiler Chickens

Thomas K. Jeffers: pioneer of coccidiosis research

Monensin Sensitivity of Recent Field Isolates of Turkey Coccidia

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