W. Malcolm Reid

Anticoccidial drugs: Lesion scoring techniques in battery and floor-pen experiments with chickens

Abstract Although lesion scoring is a commonly accepted criterion for determining the pathogenicity of coccidial species, no previous attempt has been made to standardize and describe the scoring scale. In battery trials using pure species, the six species Eimeria tenella, E. necatrix, acervulina, E. mivati, E. maxima , and E. brunetti have been scored on a 0 to + 4 scale with descriptions of the gross pathologic changes for each score. Eimeria maxima and E. brunetti were found to be the most difficult species to score since the gross pathologic picture has been difficult to correlate with weight gains or other indications of pathogenicity. Birds from floor-pen trials infected with more than one species were also graded on a 0 to +4 scale. Four sections of the intestine (upper, middle, lower, and ceca) were each scored separately. No attempt was made to determine species, but microscopic examination of scrapings was made to confirm the presence of coccidia.

Histomonas meleagridis and several bacteria as agents of infectious enterohepatitis in gnotobiotic turkeys

Abstract A dual etiology, involving a protozoan ( Histomonas meleagridis ) and a single species of bacteria ( Escherichia coli, Clostridium perfringens , or Bacillus subtilis ), has been demonstrated for infectious enterohepatitis, using gnotobiotic (“bacteria-free”) turkeys. Kochs postulates for suspected disease organisms have been applied to the combination of H. meleagridis and E. coli and each of the four postulates was fulfilled, indicating that this combination of organisms represented a true etiological pattern for infectious enterohepatitis of turkeys. Negative results for disease production were obained with H. meleagridis alone; H. meleagridis and Aerobacter cloacae + Streptococcus fecalis ; or H. meleagridis and Proteus mirabilis , as inocula for gnotobiotic turkeys. Similarly, negative results were obtained from the administration of killed or filtered E. coli + viable H. meleagridis .

Relative value of oocyst counts in evaluating anticoccidial activity.

Birds medicated with roxarsone and in another experiment with zoalene in the feed produced higher oocysts counts than unmedicated control birds receiving the same oocyst dose of Eimeria tenella or a mixture of six species (E. tenella, E. necatrix, E. brunetti, E. maxima, E. acervulina, and E. mitvati). These experiments confirm the conclusion that oocyst counts constitute an unsatisfactory and unreliable parameter for judging effectiveness of an anticoccidial even though such increases are a relatively rare occurrence in anticoccidial evaluation experiments.SUMMARY Birds medicated with roxarsone and in another experiment with zoalene in the feed produced higher oocyst counts than unmedicated control birds receiving the same oocyst dose of Eimeria tenella or a mixture of six species (E. tenella, E. necatrix, E. brunetti, E. maxima, E. acervulina, and E. mivati). These experiments confirm the conclusion that oocyst counts constitute an unsatisfactory and unreliable parameter for judging effectiveness of an anticoccidial even though such increases are a relatively rare occurrence in anticoccidial evaluation experiments.

Techniques in parasitology. I. Gnotobiotic poultry in plastic film isolators and some applications to parasitological research.

Abstract The techniques for producing gnotobiotic chickens and turkeys in plastic film isolators have been outlined along with methods for preparing parasitic organisms to be used as inocula for the gnotobiotic birds. The protozoan, Histomonas meleagridis , and the cestode, Raillietina cesticillus , are used as examples in application of the techniques to parasitological research. The experimental design illustrated for H. meleagridis was aimed at determining the etiology of infectious enterohepatitis in turkeys; for R. cesticillus , the design was to demonstrate satisfactory growth and development of a cestode in its natural host, in the absence of bacteria.

Ascaridia galli (Nematoda): Development and survival in gnotobiotic chickens

Infection and growth rates of the fowl nematode Ascaridia galli were compared in germ-free, conventional, and other gnotobiotic chickens. Uniform experimental infections induced in chickens at 7–12 days of age showed that significantly fewer (P < 0.01) worms established themselves in germ-free chickens than in chickens with conventional flora. Numbers of worms established in monoassociated hosts (Bacillus subtilis, B. cereus, and Penicillium sp.) were intermediate between those in grossly contaminated and germ-free hosts. Mean worm lengths were shorter from germ-free than conventional hosts but differences were not statistically significant. These experiments demonstrate that some A. galli larvae may establish themselves and grow for 14 or 21 days postinoculation in a germ-free environment.

Histomoniasis in Chickens: Age of Greatest Susceptibility and Pathogenicity Studies

EPORTS from the field and from diagnostic laboratories have suggested an increase in the incidence of histomoniasis in chickens. This may constitute a threat to the concentrated broiler industry of the Southeast. Experimental studies were carried out to determine the age of greatest susceptibility in growing chicks. The results are herein correlated with a review of diagnostic reports from different parts of the United States on the incidence of this disease in chickens and the ages of greatest susceptibility.

Effects of Ascaridia galli on chicks with infectious bronchitis.

HIGH incidence of light infections of the intestinal roundworm Ascaridia galli commonly occurs in broiler production. This is a remarkable build-up of worm population considering the fact that the minimum life cycle requires 51/2 weeks and broilers are marketed at 9 weeks. Furthermore, the excellent balanced rations used for growing chicks has eliminated nutritional deficiencies which are important predisposing factors to heavier worm populations. A recently completed survey of broilers in north Georgia (Reid1), showed that 59 percent of 100 flocks had birds infected with roundworms at the time they were marketed. Each flock was represented by 10 bird samples. A total of 240 or 24 percent of the 1,000 birds examined was infected. The average number of worms in infected birds was 6.2. TWo flocks could be classified as heavily parasitized with 100 percent infection averaging 33.2 worms each. The other 57 were classified as lightly infected with an average of 4.3 worms each.

Coccidiosis: Selection of the most useful parameters for anticoccidial drug testing

Abstract For somewhat different reasons, pharmaceutical houses, governmental regulatory agencies, and poultry producers must pass judgment on new anticoccidial drugs. A diversified group of parameters and formulas for combining them have been developed to assist in making decisions. These formulas have been used for comparisons following laboratory floorpen and field experimentation. Final judgment will ultimately be based on field performance measured by financial savings provided to the poultry producer.

Egg characteristics as aids in species identification and control of chicken tapeworms.

EW poultry pathologists are equipped to make specific identification of poultry tapeworms. If species could be determined quickly,the diagnostician could make valuable suggestions to poultrymen in terms of intermediate host control. Wehr5 has reviewed the extensive life history studies which have been completed on the eight common chicken tapeworms. A careful study of the list of intermediate hosts reveals many possible control suggestions after specific identification has been completed. Davainea proglottina calls for slug and snail control. Raillietina echinobothrida and R. tetragona suggest ant control while Amoebotaenia sphenoides is carried by earthworms. Hymenolepis carioca, H. cantaniana and Raillietina cesticillus are largely beetle problems while Choanotaenia infundibulum represents a beetle, housefly or grasshopper problem. Specific identification can assist the diagnostician also in making a flock prognosis since various species range from highly pathogenic to almost harmless parasites. Specific diagnosis has been delayed in the past by the time consuming methods of staining the specimen. Few laboratories are equipped to complete this identification procedure rapidly enough to be of use to poultrymen. Species identification can be achieved rapidly on fresh specimens

Severe coccidiosis in a breeder flock following high-level medication for mycoplasma and coccidia control.

SUMMARY Losses of valuable breeder stock from coccidiosis were heavy in a flock subjected to a program of high-level medication planned for mycoplasma eradication. The three different drugs - tylosin, chlortetracycline, and zoalene - were used from one day of age until 3, 3-6, and 10 weeks, respectively, and then withdrawn. The combination prevented acquisition of protective immunity, resulting in coccidioses at 16 weeks from Eimeria tenella, E. necatrix, E. acervulina, and E. brunetti. In subsequent flocks the program was successfully modified by eliminating zoalene, reducing chlortetracycline medication while continuing tylosin treatment, and using planned coccidiosis immunization. Efficacy experiments on tylosin tartrate administered subcutaneously in oil indicate moderate coccidiostatic activity of tylosin against Eimeria tenella, little activity against E. maxima and E. mivati and no activity against E. acervulina, E. brunetti, and E. necatrix. The role of the tylosin administered in this manner in suppressing coccidial cycling is more questionable than that of the other two drugs, which have well established anticoccidial activity when ad