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Biomedical subjects

L R McDougald

Publications and source records attributed to L R McDougald.

14 recordsLinked to original sources
PubMed1979

Eimeria tenella: anticoccidial action of drugs in birds with surgically closed ceca.

Surgical ligation of chick ceca was used to study the role of absorption and extraintestinal transport in the action of anticoccidial drugs. The administration of drugs in the feed was started after ligation of one of the paried ceca. Birds were inoculated orally with oocysts of Eimeria tenella before cecal ligation or were given bilateral cecal injections of sporozoites after ligation. Cecal lesions caused by the coccidia were evaluated and compared on day 6 postinoculation. Lesions in ligated and unligated ceca were reduced by feeding robenidine (33 ppm), arprinocid (70 ppm), zoalene (125 ppm), aklomide (250 ppm), clopidol (125 ppm), nicarbazin (125 ppm), monensin (120 ppm), salinomycin (60 ppm), and lasalocid (75 ppm). The lesions were more severe in the ligated cecum than in the intact cecum, whether in nonmedicated or medicated birds, but the differences were statistically significant only upon treatment with amprolium, aklomide, robenidine, and clopidol. Generally, however, all drugs except amprolium, significantly reduced the lesions in the ligated cecum in comparison with the control, nonmedicated ligated cecum. Therefore, we concluded that the systemic absorption of most anticoccidial drugs contributes significantly to their efficacy against coccidia in the intestinal mucosa.

Absorption↗
PubMed1979

Attempted cross-transmission of coccidia between sheep and goats and description of Eimeria ovinoidalis sp. n.

Attempted infection of 2 young lambs with oocysts of Eimeria christenseni from a goat was unsuccessful. Negative results were obtained also when young kids were fed oocysts of Eimeria ninakohlyakimovae from sheep. There was no difficulty in infecting lambs with the sheep coccidium resembling E. ninakohlyakimovae nor goats with the goat coccidium E. christenseni. Oocysts from the goat measured 38.4 X 26.7 microns, but were easily distinguished from Eimeria ahsata from the sheep by sporocyst size and shape, and from Eimeria ovina by oocyst size. Eimeria ninakohlyakimovae-like oocysts from sheep averaged 23.0 X 18.2 microns and were morphologically indistinguishable from previously reported goat coccidia. Since no cross infections of sheep and goats could be accomplished with oocysts of Eimeria sp. characteristic of one or the other host, I concluded that sheep coccidia previously known as E. ninakohlykimovae are distinct from morphologically similar goat coccidia and therefore constitute a separate species. Since the name E. ninakohlyakimovae was first used for coccidia from the goat, the sheep coccidium is renamed Eimeria ovinoidalis with oocyst structure and endogenous stages similar to those previously described from the sheep.

Animals↗
PubMed1979

Floor pen studies on the anticoccidial efficacy of arprinocid in turkeys.

Arprinocid was tested against coccidiosis in turkeys reared in floor pens. Contamination of pens with Eimeria meleagrimitis, E. adenoeides, and E. gallopavonis was accomplished by the infected seeder bird technique. Performance improved with increasing levels of arprinocid through 120 ppm, but weight gains were depressed at 180 ppm. Lesion scores were significantly and progressively reduced by treatment with 60, 90, 120, and 180 ppm of arprinocid. Control of lesion scores and performance of birds treated with 120 ppm of arprinocid were comparable to the amprolium (125 ppm) treatment. In a separate experiment, the oocyst passage of E. meleagrimitis and of E. adenoeides was progressively reduced by increasing levels of arprinocid, and sporulation rate was decreased. Sportulation was not obtained in oocysts from birds fed arprinocid at 120 ppm or higher.

Adenine↗
PubMed1979

Efficacy and compatibility of amprolium and carbarsone against Coccidiosis and blackhead in turkeys.

Amprolium and carbarsone were tested separately and in combination for efficacy in prevention of occidiosis and histomoniasis, respectively. In these studies, amprolium at .0125% in the diet was efficacious in prevention of coccidiosis, and carbarsone had no deleterious effects when fed simultaneously at .0375%. Carbarsone at .0250% was efficacious in prevention of histomoniasis, and amprolium had no deleterious effects when fed concurrently at .025%. These results indicated that both drugs could be used in combination without interference of efficacy against the target diseases.

Amprolium↗
PubMed1978

Efficacy of monensin against coccidiosis in lambs.

Lambs fed monensin mixed in a complete fattening ration at concentrations of 5, 10, or 20 ppm were protected against death, impaired body weight gain, and diarrhea due to infections of Eimeria ninakohlyakimovae and E ahsata. Monensin given at the concentration of 10 ppm reduced oocyst passage and, at the concentration of 20 ppm, almost completely controlled oocyst passage. Protection was afforded by monensin given at the concentration of 5 ppm, although oocyst passage was excessive and body weight gains were suboptimal. Infected control lambs were severely affected, with mortality rate of 30% to 50% on days 14 to 18 and oocyst passage averaging 286,000,000 oocyst/lamb, Oocyst production peaks on days 12 to 15 and 21 to 27 correlated with the appearance of oocysts of E ninakohlyakimovae and E ahsata, respectively. Body weight gains and feed consumption of lambs fed monensin at the concentration of 10 or 20 ppm indicated that the drug was well tolerated at these dose levels and this route of administration. The compound was efficacious in Dorset and Suffolk X Hampshire lambs, and caused no problems when fed to pregnant ewes.

Animals↗
PubMed1978

Monensin for the prevention of coccidiosis in calves.

Young calves (Holstein-Friesian) were inoculated with Eimeria bovis on the 3rd day after the start of 31 days' feeding of a ration containing added monensin in 2 dose levels: 16.5 g or 33 g/metric ton of feed. Monensin-treated calves were free of clinical signs of coccidiosis, but inoculated control calves developed diarrhea and had excessive oocyst discharge on days 19 to 28 after they were inoculated. Weight gains and feed efficiency in monensin-treated calves were equal or superior to those factors in noninoculated control calves for the 31-day period.

Administration, Oral↗
PubMed1976

Comparative in vitro development of precocious and normal strains of Eimeria tenella (Coccidia).

Eimeria tenella strain Wis-F is known to develop in chickens with a significantly shortened prepatent period and its pathogenicity is virtually completely attenuated. In vitro development of this strain paralleled development of the control (Wisconsin) strain through the first asexual generation. Instead of entering 2nd generation schizogony, however, most of the Wis-F merozoites developed into microgamonts or macrogamonts. Wall-forming bodies were prominent in developing macrogametes at 80-88 hr and began coalescing into the oocyst wall by 88 hr. Microgamete development paralleled that of macrogametes, with the appearance of multinucleate, immature forms at 72-80 hr and with recognizable, spermlike microgametes being prominent at 88-96 hr. Pathogenicity attenuation and reduction of the length of the prepatent period clearly resulted from omission of a portion of the life cycle (2nd generation schizogony).

Animals↗
PubMed1976

Anticoccidial action of monensin in turkey poults.

Monensin was effective within the range 60-100 p.p.m. in control of coccidiosis in turkey poults in a series of laboratory experiments. Under conditions of heavy infections with Eimeria meleagrimitis and E. adenoides, 100 p.p.m. of monesin was significantly more effective than 60 p.p.m. in protecting weight gains. When light or moderate infections with E. meleagrimitis, E. adenoides and E. gallopavonis were used, there were no significant differences among monesin-medicated treatments. In all instances the monensin-medicated treatments gained significantly more weight than noninfected, nonmedicated controls, when measured at 7 days post-inoculation. Similarly, oocyst, passage was reduced, feed conversion was protected and mortality was controlled in monensin-treated poults.

Animals↗
PubMedDate not supplied

Interaction of infectious bursal disease and coccidiosis in layer replacement chickens.

During a floor-pen study on anticoccidial programs for layer-replacement pullets, there was a natural outbreak of infectious bursal disease (IBD). The interaction of coccidiosis and IBD was characterized by: excessive deaths from coccidiosis; and apparent failure of some anticoccidial drug treatments. Immunity to coccidiosis was not blocked by the IBD infection, although immunity was less in some treatments than would be expected with the degree of coccidiosis exposure.

Animals↗
PubMedDate not supplied

Innate and acquired immunity vs. anticoccidial medication in managing coccidiosis in turkeys.

Turkeys 2, 6, or 10 weeks old that had been reared free of coccidial infection were susceptibe to infection with Eimeria meleagrimitis, E. adenoeides, and E. gallopavonis. The 6- or 10-week-old birds were more resistant to infection than the 2-week-old birds (no deaths from coccidiosis vs. 100% mortality). Lesion scores were lower in 10-week-old birds than in 6-week-old birds, but significantly greater weight losses occurred in the older birds. Turkeys reared in floor pens contaminated experimentally with coccidia were immune to homologous challenge at 10 weeks old, with only slight (numerical) reduction of weight gains following challenge with 50,000 oocysts/bird of each species. These results demonstrated some degree of innate resistance associated with age, although not enough to protect against heavy challenge. The resistance of birds reared in floor pens was due largely to acquired immunity resulting from infection with coccidia. Amprolium (125 ppm), monensin (100 ppm), or Polystat (250 ppm) protected the turkeys against experimental infections in floor pens, as measured by weight gains, feed efficiency, death due to coccidiosis, and lesion scores.

Age Factors↗
PubMedDate not supplied

Efficacy of monensin against turkey coccidiosis in laboratory and floor-pen experiments.

Monensin at 60, 80, or 100 ppm in feed reduced mortality and lesion scores while protecting against weight loss of turkeys infected with the major pathogenic species: Eimeria adenoides, E. meleagrimitis, and E. gallopavonis. With single and mixed infections in battery-cage experiments, the death rate of unmedicated turkey poults was 33-75%. Weight gains were significantly (P is less than or equal to 0.05) better with 100 ppm monensin than 60 ppm, as were also lesion scores. Under floor-pen conditions there were no significant differences among monensin treatments. Moisture content of the litter was significantly lower in all monensin-medicated pens (40%, compared with 52% moisture in pens of unmedicated controls).

Animals↗