To determine whether chemotherapeutic compounds available for use in domestic poultry are effective at controlling
coccidiosis in northern bobwhites (Colinus virginianus), we tested 13 chemotherapeutic anticoccidials including
amprolium (250 parts per million [ppm]),
clopidol (125 ppm),
diclazuril (1 ppm and 2 ppm),
decoquinate (30 ppm),
lasalocid (120 ppm),
monensin (90 ppm),
narasin/
nicarbazin (36/36 ppm),
robenidine (33 ppm),
roxarsone (50 ppm),
sulfadimethoxine/ ormetoprin (125/75 ppm),
salinomycin (60 ppm),
semduramicin (25 ppm), and
zoalene (125 ppm and 150 ppm). Three tests were conducted using two replicates of 10 birds each: Infected, unmedicated controls and medicated birds were challenged with 1 x 10(6) oocysts of a field isolate consisting primarily of Eimeria lettyae. Subsequently, we tested
clopidol,
lasalocid,
salinomycin,
diclazuril (1 ppm), and
monensin against mixed-species field isolates containing E. lettyae, E. dispersa, E. colini, or all.
Weight gain, gross intestinal lesions, severity of
diarrhea, and feed conversion ratio (FCR) 6 days postinfection were recorded. Lesion score, as previously reported, was unreliable as a measure of severity of
infection in comparison with
weight gain, fecal scores, and FCR. Excellent to good efficacy was found in
clopidol,
decoquinate,
diclazuril (1 ppm and 2 ppm), and in
lasalocid,
narasin and
nicarbazin,
robenidine,
sulfadimethoxine/ormetoprin, and
zoalene (150 ppm). Marginal protection was found using
monensin,
salinomycin,
semduramicin, or a
roxarsone/
semduramicin combination.
Amprolium,
roxarsone, and
zoalene (125 ppm) were ineffective at controlling coccidia. Two of the six isolates tested against
diclazuril 1 ppm and
clopidol demonstrated a high degree of resistance, but none of the six isolates was resistant to
lasalocid. Four of the eight isolates showed mild to moderate, and moderate to high, resistance against
monensin and
salinomycin, respectively. These findings indicate that several available compounds are effective at controlling
coccidiosis in bobwhites.