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Poults naturally infected with L. smithi demonstrated a significant (P less than 0.01) decrease in arterial PO2 (mm. Hg) during the second and third weeks after exposure to black fly bites. Poults fed Clopidol (0.0125%) during the exposure period and subsequent experimental periods showed very little parasitemia and no significant reduction in arterial PO2.
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Six experiments were carried out to study the effect of feed additive antibiotics on body weight, mortality and oocyst production in chickens infected with coccidiostat-susceptible or -resistant strain of E. tenella. Levels of antibiotic and coccidiostat in fed (mg./kg.) were: thiopeptin, 2; zinc bacitracin, 20; penicillin, 12; chlortetracycline, 22; amprolium plus ethopabate, 125 plus 8; clopidol, 125. All experiments included 7 groups; 2 of these groups were uninfected and infected controls, and the 5 remaining groups were all infected and given diet containing antibiotic, amprolium plus ethopabate, antibiotic and amprolium plus ethopabate, clopidol, or antibiotic and clopidol. Chickens in each group were fed respective diet beginning one day prior to coccidia exposure. In two experiments, infection with a coccidiostat-susceptible strain resulted in severe clinical coccidiosis in chickens on the basal ration and on thiopeptin-diet, but dietary thiopeptin prompted recovery of body weight. In one experiment where chickens were infected with a strain resistant to amprolium plus ethopabate and clopidol, birds on dietary thiopeptin attained higher body weight than birds on the basal ration. In three experiments when a strain resistant to amprolium plus ethopabate was inoculated, birds given the basal ration, bacitracin, penicillin, chlortetracycline, or amprolium plus ethopabate diet developed cecal coccidiosis. Chickens on ration containing antibiotic alone attained higher body weight than chickens on the basal ration. Combination of antibiotic and amprolium plus ethopabate resulted in higher weight attained than amprolium plus ethopabate alone. Clopidol suppressed development of coccidiosis, and the combination of antibiotic and clopidol resulted in higher gains than in clopidol alone.
The gas chromatographic response of four perfluoro derivatives, of four agricultural chemical [diethylstilbestrol] (DES) clopidol, linuron and carbofuran] was examined. The derivatives varied in fluorine content from 3 to 30 atoms per molecule. The sensitivities of the derivatives were found to be ca. 10-100 times greater by electron-capture detection than by electrolytic conductivity detection (halogen mode). The sensitivity also was found to increase with increasing fluorine content for all derivatives by electrolytic conductivity, whereas by electron capture, DES and clopidol exhibited similar responses with either the penta-, hepta-, or pentadeca-fluoro derivatives. The sensitivity of linuron and carbofuran derivatives by electron capture varied with increasing fluorine content. For detection by electron capture, the hepta-fluorobutyryl derivatives were preferred for DES and clopidol, and either the hepta-fluorobutyryl or the pentadecafluorooctanoyl derivatives for linuron and carbofuran. For detection by electrolytic conductivity, the pentadecafluorooctanoyl derivatives were superior for all four compounds.
Infections in the chicken embryo have been used to study the development of drug resistance in an embryo adapted strain of E. tenella. Resistance was developed to decoquinate, clopidol and robenidine by serially passaging this strain, but evidence for the development of resistance to amprolium was inconclusive. Resistance to decoquinate developed more readily than to the other drugs. Attempts to increase resistance to clopidol, robenidine and amprolium by increasing the sporozoite inoculum and by the use of a mutagenic agent were unsuccesful. No cross-resistance was found between the 4 drugs. Drug resistant lines of the Houghton strain (H) of E. tenella, made resistant to the 4 anticoccidial drugs by passage in chickens, were found to be resistant when evaluated using chicken embryo infections. Lines made resistant to decoquinate were not controlled by any concentration of this drug, suggesting that resistance, once developed, was absolute and not dependent on drug concentration. Lines made resistant to robenidine, clopidol and amprolium, however, were controlled by higher drug concentrations suggesting that in this case resistance was dependent on drug concentration.
The chemotherapeutic efficacy of 6 in-feed compounds against Ichthyophthirius multifiliis Fouquet, 1876 was assessed using experimental infections of rainbow trout Oncorhynchus mykiss (Walbaum) fingerlings. Trial doses of 104 ppm amprolium hydrochloride or 65 ppm clopidol fed to fish for 10 d prior to infection significantly reduced the number of trophonts establishing in trout fingerlings by 62.0 and 35.2% respectively. In-feed treatments of infected trout with either 63 or 75 ppm amprolium hydrochloride, 92 ppm clopidol, or 38, 43 or 47 ppm salinomycin sodium for 10 d also significantly reduced the number of surviving trophonts by 77.6 and 32.2% for amprolium, 20.1% for clopidol and 80.2, 71.9 and 93.3% respectively for salinomycin sodium.
A series of experiments is described in which two drug-resistant strains of Eimeria maxima were passaged together in untreated chicks. The resultant oocysts were then inoculated into chicks treated with both drugs. When strains resistant to methyl benzoquate and sulphaquinoxaline or clopidol and sulphaquinoxaline were used the resultant infections were not controlled by the double treatment, indicating the acquisition of resistance factors by one strain from the other. When strains resistant to clopidol and methyl benzoquate were used the phenomenon was not observed.
Eimeria tenella was passaged in the presence of suboptimal and optimal concentrations of lasalocid (X-537A, sodium salt) in feed. Lasalocid was equally active at concentrations of 0.006 and 0.0075% against the 10th and 15th passage of E. tenella lasalocid exposed strains. Resistance to lasalocid could not be induced. Lasalocid administered in the feed at 0.0075% was tested in controlled battery experiments against E. tenella strains resistant to known anticoccidials in chicks. These studies demonstrated that lasalocis, at the optimal feed concentration of 0.0075% was highly effective against coccidiosis induced by strains of E. tenella resistant to sulfaquinoxaline, nicarbazine, zoalene, emprolium, clopidol and 4-hydroxyquinoline. Lasalocid medicated chicks were heavier, converted feed more efficiently, showed less pathologic lesions, and had lower mortality (P less than or equal to .05) than the infected unmedicated controls as well as sulfaquinoxaline, nicarbazine, zoalene, amprolium-ethopabate, clopidol, buquinolate, decoquinate and nequinate medicated groups. Cross-resistance to lasalocid was not demonstrated.