Joyce Johnson

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.

Eimeria of American chickens: characteristics of six attenuated strains produced by selection for precocious development.

Six attenuated lines of Eimeria species of the chicken of USA origin were produced by selection for precociousness. These lines were less pathogenic, judged by body weight changes and intestinal lesions in infected chickens, than the parent strains from which they were derived. The immunogenicity of the precocious lines and their parent strains was similar. The use of these attenuated Eimeria Unes for immunological control of coccidiosis is discussed.

Histomoniasis in gnotobiotic chickens and turkeys: biological aspects of the role of bacteria in the etiology.

Abstract The bacterial requirements for producing infectious enterohepatitis in bacteria-free chickens were different from those for the disease in bacteria-free turkeys. When both Escherichia coli and Clostridium perfringens were introduced with Histomonas meleagridis, mild atypical cecal lesions were produced in 3 of 28 chickens while typical liver and cecal lesions were both present in all of 25 turkeys. When single species of bacterial agents were used, the rate of infection was less. More lesions were produced with C. perfringens than with E. coli. The cecal bacterial flora of conventional chickens, when introduced into bacteria-free chickens, fulfilled the requirement of H. meleagridis for induction of infectious enterohepatitis. Attempts to define the specific bacteria involved in the etiology of the disease in chickens from among 48 different bacterial isolates and Candida albicans were unsuccessful, although very mild disease was produced inconsistently with various combinations of strains of E. coli with Pseudomonas aeruginosa and Streptococcus faecalis or with C. perfringens. Eimeria adenoides, a cecal coccidium, survived when introduced with Histomonos-infected Heterakis eggs into bacteria-free turkeys and supported the growth of some histomonads but not Heterakis gallinarium larvae. Eimeria adenoides did not simulate the role of bacteria in producing infectious enterohepatitis. Disease was produced and Heterakis larvae did survive in conventional turkeys receiving E. adenoides and infected Heterakis eggs. The essential contributing factor of bacteria in the pathogenesis of infectious enterohepatitis was determined to be neither a favorable pH nor an oxidation-reduction potential value within the intestine of the host. The oxidation-reduction potential of bacteria-free cecal contents was strongly positive, that of the conventional chicken with its indigenous microflora was strongly negative, while the potential of the contents of ceca with infectious enterohepatitis was intermediate. The pH of the bacteria-free cecum closely approximates that of the parasite-infected intestine, while the pH of the uninfected conventional cecum was somewhat lower. In the pathogenesis of infectious enterohepatitis, the role of bacteria apparently was more vital for the survival of Heterakis than Histomonas.

Immunisation of young broiler chickens with low level infections of Eimeria tenella, E. acer vulina or E. maxima 1

Chickens given 200 oocysts of Eimeria tenella at day-old followed by a dose of between 300 to 500 oocysts at 8 days of age were afforded substantial protection against challenge at 15 and 22 days of age. Chickens given 2,000 oocysts of E. acervulina at day-old were partially protected against challenge infection given at 15 or 22 days of age. When chickens were given doses of 2,000 and 10,000 oocysts at 1 and 8 days, respectively, significant protection against challenge at 15 and 22 days was obtained. Chickens given five oocysts of E. maxima at day-old were partially protected against challenge at 15 or 21 days of age. A dose of 50 oocysts at day-old gave substantial protection judged by body weight changes and lesion scores. The protection was slightly greater when the immunising dose was given at 8 days of age. The results indicate that with chickens kept on wire floors where the conditions for reinfection were minimal, substantial immunity to challenge infection could be achieved by giving small numbers of oocysts to chickens 1 to 8 days of age.

Effects of Eimeria acervulina on Intestinal pH in Conventional and Gnotobiotic Chickens

White Leghorn cockerels inoculated with sporulated oocysts of Eimeria acervulina had lower mean pH values in the upper, middle, and lower small intestine than did uninoculated birds. Conversely, the pH increased in the ceca while no decrease of pH was found in the gizzard. The magnitude of the pH decrease was not correlated with oocyst dose or severity of infection as measured by lesion scores. In gnotobiotic chicks, infection decreased pH in the duodenum from that in uninoculated chicks. The decrease was the same within any experiment, irrespective of microbial status of the birds (germ-free, Streptococcus fecalis inoculated as a monoisolate, or conventional bacterial flora), indicating that bacteria played no role in lowering the intestinal pH.

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.

Transmission of histomoniasis with male Heterakis gallinarum (Nematoda)

Histomoniasis was transmitted to poults inoculated orally with recently harvested whole intact male worms in three trials (4/5, 5/6, 2/4), but not with female worms (0/5, 0/9, 0/3). When triturated male worms were given in two trials, the rate of transmission was reduced (3/5, 0/10). Triturated female worms given orally produced histomoniasis in 1/9 poults. These results suggest that further unknown steps may be involved in histomonad transmission by heterakid worms. This study was partially supported by NSF Grant GB-5227.

The pathogenicity, immunogenicity and endogenous development of a precocious line of Eimeria brunetti.

A precocious line of Eimeria brunetti with a prepatent period of 75 hours was compared with the parent strain (normal prepatent period of 120 hours) in a battery study. The precocious line was less pathogenic than the parent, and caused less weight depression and lower lesion scores in chickens given any dose of oocysts (1,000, 5,000, 25,000 or 125,000). No chickens receiving the precocious line died, whilst 19% and 25% mortality occurred in groups receiving 25,000 and 125,000 oocysts of the parent strain. The precocious line was also highly immunogenic. Chickens given 1,000 or 5,000 oocysts of the precocious line or parent strain developed immunity sufficient to protect against a challenge of the parent strain which caused 83% weight depression and 13% mortality in non-immunised, challenged controls. Histological observations showed that the endogenous development of the parent strain and precocious line was identical up to 48 hours. However, by 72 hours macrogametocytes and microgametes were seen only with the precocious line. The abbreviated asexual cycle of the precocious line would account for its lower reproductive potential.

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.

Efficacy of semduramicin and salinomycin against different stages of Eimeria tenella and E. acervulina in the chicken

The efficacy of a new ionophore, semduramicin, was compared with salinomycin in a series of in ovo and in vivo trials. Semduramicin was more efficacious than salinomycin against Eimeria tenella sporozoites as judged by oocyst production in embryonated eggs. When the two drugs were given in ovo at 93 h post inoculation (PI), both drugs exerted some effect against late schizogonous stages of E. tenella. In three battery studies, semduramicin (25 ppm) and salinomycin (60 and 66 ppm) were tested against E. tenella and E. acervulina. Medicated feed was withdrawn at 24-h intervals PI to study the stage of action of the anticoccidials. In E. tenella infected chickens, both anticoccidials exerted their maximum effect on weight gain and feed:gain ratio through the first 72 h PI. Semduramicin was more effective than salinomycin in controlling E. tenella lesions and coccidiosis mortality. With E. acervulina, both drugs acted similarly on early life cycle stages and no improvement in performance was recorded when medicated feed was given for longer than 72 h. Semduramicin was more effective than salinomycin in controlling E. acervulina lesions.