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Submitted to: Meeting Abstract
Publication Type: Abstract Only Publication Acceptance Date: 5/31/2014 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Applying ionophore drugs and synthetic chemicals to poultry feed has been used for over 50 years to control avian coccidiosis. While this strategy has been and continues to be effective, drug resistance has prompted alternatives such as drug rotation or vaccination with live Eimeria oocysts. Often there is no a priori way of determining the level of drug resistance in the Eimeria population in litter until a decrease in performance or an increase in necrotic enteritis occurs. The most common method of measuring drug resistance involves testing several anti-coccidial drugs in susceptible chickens, a process that is both time-consuming and labor-intensive. The purpose of the present study was to develop an in vitro assay for testing ionophore sensitivity of E. tenella. Preliminary dose titration experiments revealed an optimum concentration of monensin and salinomycin that did not affect host cell integrity, but inhibited invasion and development of E. tenella sporozoites. These assay conditions were used to develop a rapid and highly sensitive polymerase chain reaction (PCR) for determining inhibitory effect of the ionophores on intracellular E. tenella. Moreover, both assays showed excellent agreement with counting intracellular sporozoites. Time-course studies revealed an optimum effect of monensin at 24 hr and salinomycin at 48 hr post-invasion. The in vitro assay for ionophore sensitivity can be completed within 1 week after collection of oocysts from litter. Studies are underway to assay E. tenella sensitivity to synthetic chemicals, and apply the assay to other Eimeria species, such as E. acervulina and E. maxima. |
