chiniofon and Poultry-Diseases

The anticoccidial mode of action of quinolones (6-decyloxy-4-hydroxyquinoline-3-carboxylates) against Eimeria tenella and E. acervulina in chickens has been investigated, using decoquinate and M&B 15,584 as examples. The well known static effect on sporozoites of relatively high continuous drug concentrations in the food masked other components of the mode of action, newly described here. Lower concentrations of quinolones allowed sporozoites to continue their development. First-stage schizonts were susceptible to a secondary cidal effect, although later schizonts seemed to be rather refractory. Furthermore, the sporulation of oocysts produced by E. tenella that completed its life cycle in the presence of suboptimal concentrations of quinolones was inhibited: this probably reflects a drug effect on gametocytes. Quinolones were absorbed rapidly from the chicken intestine, probably in less than 1 h. Drug withdrawal experiments showed that quinolones persisted in chicken tissues at active concentrations for up to 48 h. Despite their static effect on sporozoites, they may nevertheless be expected to exert a therapeutic effect against drug-sensitive coccidia in interrupted regimes that allow the later cidal effect to come into play. This allows immunity to coccidiosis to develop in the presence of drug. These new results, with the previously available data have been combined in an updated account of the anticoccidial mode of action of quinolones in the chicken.

Topics: Animals; Chickens; Coccidiosis; Coccidiostats; Decoquinate; Drug Administration Schedule; Eimeria; Eimeria tenella; Hydroxyquinolines; Male; Poultry Diseases; Regression Analysis; Time Factors

Donor chickens given feed medicated with one or two levels of decoquinate or given non-medicated feed were infected with oocysts of Eimeria tenella or E. maxima per os. Twelve hours after inoculation with oocysts liver, mid-intestine or ceca homogenates were fed to previously uninfected recipient chickens. The results showed that continuous medication with decoquinate was effective in preventing the transfer of sporozoites from the intestine to the liver. Oocysts were detected in the feces of all recipients of tissue from non-medicated donors, showing that some sporozoites of E. maxima and E. tenella are normally transferred to liver. Young broiler chickens were immunized by oral inoculation of E. maxima oocysts. The immune status of similar chickens inoculated with sporozoites of the same species directly into the liver or spleen were assessed. During the experimental period half of the chicks were provided with non-medicated food and the remainder were given feed supplemented with decoquinate; decoquinate was effective in arresting the development of the sporozoites. Two weeks after initial infection the birds were challenged with oocysts of E. maxima per os. Injection of sporozoites into the spleen did not protect against challenge. Birds inoculated with sporozoites into the liver were unable to develop a significant level of immunity. When the drug pressure was removed from these birds, parasitism of the intestine occurred and immunity developed.

Topics: Animal Feed; Animals; Chickens; Coccidiosis; Decoquinate; Eimeria; Feces; Hydroxyquinolines; Immunity; Immunization; Intestines; Liver; Poultry Diseases

Resistance to arprinocid was developed in Eimeria tenella after seven serial passages in chickens given progressively greater concentrations of drug. Resistance to the quinolone decoquinate developed after eight passages. These results taken together with the observation that resistance to both drugs developed within a year of their introduction suggest that some indication of the likelihood of the emergence, in the field, of resistance to a given drug, may be obtained by comparing it with a standard reference drug in experimental studies.

Topics: Adenine; Animals; Chickens; Coccidiosis; Coccidiostats; Decoquinate; Drug Resistance, Microbial; Eimeria; Hydroxyquinolines; Poultry Diseases

The effect was studied of introducing about equal numbers of decoquinate-sensitive or decoquinate-resistant Eimeria tenella oocysts into a floor pen of susceptible unmedicated chickens. "Sentinel" birds introduced 2, 3, 4, 5, and 6 weeks later were used to recover populations of E. tenella oocysts. In drug sensitivity tests, populations of oocysts harvested at 4 weeks were partially resistant to decoquinate medication. Oocysts obtained after 5 and 6 weeks were highly sensitive to decoquinate medication. The results indicate that drug-sensitive E. tenella parasites are more likely to dominate in absence of medication.

Topics: Animals; Chickens; Coccidiosis; Decoquinate; Drug Resistance; Eimeria; Female; Hydroxyquinolines; Male; Poultry Diseases

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.

Topics: Amprolium; Animals; Anti-Bacterial Agents; Clopidol; Coccidiosis; Coccidiostats; Dinitolmide; Drug Resistance; Eimeria; Feces; Female; Hydroxyquinolines; Lasalocid; Male; Nicarbazin; Poultry Diseases; Sulfaquinoxaline

Topics: Amprolium; Animals; Chickens; Clopidol; Coccidiosis; Coccidiostats; Drug Evaluation, Preclinical; Hydroxyquinolines; Poultry Diseases; Quinolines; Robenidine; Sulfaquinoxaline