P. L. Long

Sampling broiler house litter for coccidial oocysts

1. A method of sampling the surface litter of commercial broiler houses for laboratory estimation of numbers of coccidial oocysts is described. 2. The resulting estimates can be regarded as indices of the total number of oocysts present in the house at the time of sampling. 3. Using material from a variety of sources it was shown that reliable estimates for many practical purposes can be achieved with few samples, unless the birds are less than 3 weeks old. 4. Oocyst numbers usually reached a peak 4 to 5 weeks after introduction of the birds and then rapidly declined in the next few weeks.

Studies on the Stage of Action of Ionophorous Antibiotics against Eimeria

Sporozoites of Eimeria tenella were treated with different anticoccidial drugs in vitro and their subsequent viability was tested by inoculating them into chicken embryos. Monensin, salinomycin, lasalocid, and arprinocid, at concentrations between 0.01 and 1.0 micrograms/ml, greatly reduced sporozoite viability as judged by mortality, hemorrhage and specific lesions in the embryo chorioallantois. Monensin was also effective in reducing the viability of sporozoites of E. mivati and E. tenella as judged by oocyst production occurring in embryos; activity of monensin was greater against E. tenella than against E. mivati. Monensin (0.1 mg) inoculated into embryos inhibited development of E. tenella. Oocysts which were produced in the presence of the drug sporulated normally and sporozoites obtained from them were fully infective. By initiating treatment of chickens with monensin at different times in relation to infection, it was shown that the drug exerts its anticoccidial effect on the primary invasive stage and on the gametogonous stage of E. tenella and E. necatrix. The effect of gametogony was tested by initiating infections with second generation merozoites of E. tenella. Significant reduction in oocyst production occurred in three of four strains of E. tenella tested. Medication with monensin initiated before merozoite inoculation was effective in inhibiting oocyst production, but medication starting 5 hr after merozoite inoculation was not. This differed from the effects of arprinocid and sulfaquinoxaline which were expressed both before and 5 hr after merozoite inoculation. The results show that the ionophorous anticoccidial drugs exert their anticoccidial action primarily against the invasive stages of Eimeria.

Purification and partial characterization of the pancreatic proteolytic enzymes trypsin, chymotrypsin, and elastase from the chicken.

The purpose of this work was to isolate, purify and partially sequence trypsin, chymotrypsin and elastase from the chicken pancreas. The extraction of the pancreatic zymogens with 0.5 M CaCl2 at pH 7.5 for 9 h appeared to be most effective in obtaining maximum recovery of the three enzymes. The sequential Cucurbita maxima trypsin inhibitor I/bovine pancreas trypsin inhibitor/soybean trypsin inhibitor affinity chromatography gave the best result for the isolation of trypsin, chymotrypsin and elastase, respectively, from the same extract. For each proteinase, multiple form of enzymatic activity could be observed after gel electrophoresis and each form was further purified on an ion-exchange column. The N-terminal amino acid sequence of trypsin and chymotrypsin showed homologies with the bovine enzymes whereas elastase showed homologies with the porcine enzyme. The molecular mass of trypsin, chymotrypsin and elastase were estimated to be 23,500, 25,700 and 25,000, respectively, which are values close to those in mammalian species. Although some kinetic constants (Km and k(cat)/Km) appeared different from those observed in other species, the pH dependent enzymatic activities were similar to those reported in other animal species.

Coccidiosis in broilers: Evaluation of infection by the examination of broiler house litter for Oocysts

A study was made of the incidence of coccidial oocysts in approximately 1,660 samples of litter from 48 broiler houses on 5 broiler farms during a 12 month period during 1974-75. Oocysts of Eimeria acervulina and Eimeria maxima predominated in the samples but oocysts resembling Eimeria brunetti and Eimeria tenella were sometimes present. Oocyst numbers were extremely low and variable at 2 weeks, probably because of the small proportion of faecal material present at this time, reached a peak at 4-6 weeks and dropped to a low level at 8-9 weeks. For the last 3 crops of birds reared in these houses, the anticoccidial drug Monensin was used and extremely small numbers of oocysts were found in the litter. Significantly improved food conversion ratios and body weights were noted in these broilers. The results indicate that the examination of a few litter samples for oocysts, provided that they are taken from broiler houses at regular intervals after the 3rd week, could provide useful information on the effectiveness of anticoccidial drugs in controlling coccidiosis.

Eimeria tenella: Immunogenicity of arrested sporozoites in chickens

Groups of chickens were medicated with the anticoccidial drug, decoquinate, and starting 1 day after this medication they were given daily inoculations of either 1 X 10(4) (Experiment 1) or 1 X 10(5) (Experiment 2) oocysts of a decoquinate-sensitive strain of Eimeria tenella. This assured the presence of large numbers of drug-inhibited sporozoites in the cecal tissues. The immunity arising from the presence of these inhibited sporozoites was assessed by challenging the medicated chickens with a 2.5 X 10(5) oocysts of a decoquinate-resistant strain of E. tenella. The response to challenge was assessed by weight gain, the severity of cecal lesions, hematocrits, and cecal oocyst numbers. The inhibited sporozoites promoted little (if any) immunity judged by clinical signs of disease. However, judged by body weight changes after challenge, the presence of inhibited sporozoites provided substantial protection against the body-weight-depressing effects of the challenge dose. These findings emphasize the importance of stage-specific antigen expression in Eimeria spp. infections and support the notion that immunogenicity is associated with tropic stages of the parasite.

Intestinal and Extraintestinal Life Cycles of Eimeriid Coccidia

Publisher Summary This chapter discusses the certain aspects of the life cycles of the genera Zsospora, Caryospora, and Eirneria, in the family Eimeriidae and focuses on some new information on facets of the intestinal cycle. The novel concept of possible intermediate hosts in the life cycles of some coccidians is also discussed. The extra-intestinal migration of the species of Eimeria is known for some time in fishes; several species multiplying in viscera have now been recorded in birds and mammals. Species of Caryospora and Isospora also have extra-intestinal stages. Considering the experimental evidence involving the effects of immunosuppressive drugs or intercurrent infections on coccidial development, it seems probable that some rare extra-intestinal infections are caused by aberrant intestinal species. The chapter also reviews the various hypotheses concerning the evolution of protozoa within the Apicomplexa. Infection of the intestinal tract by coccidian ancestors preceded their invasion deeper into intestinal tissue and ultimate development in extra-intestinal sites. Further investigation is needed for determining how widespread the phenomenon of dissemination among members of the genus Eimeria is. The means by which this dissemination occurs in intestinal species of Eimeria and how similar it might be to the mechanism in Zsospora, Toxoplasma, Caryospora and species of Eimeria occurring outside the gastrointestinal tract, remain to be explored.

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.

Strain variation within Eimeria meleagrimitis from the turkey

During the course of a field study of coccidiosis in turkeys, Eimeria oocysts were found which had much smaller dimensions that any previously recorded isolate from the turkey. These oocysts were purified by single oocyst infection of a turkey. The first oocysts (mean dimensions 16-15 X 14-75 micrometer) were recovered 103 h later. Inoculation of between 0-5 and 2-5 X 10(5) oocysts of this isolate caused severe effects on body weight gain. Cross-immunity studies showed the parasite to be a strain of E. meleagrimitis. Electrophoretic analyses of two enzymes showed that the strain could be differentiated from another strain of E. meleagrimitis (Weybridge strain B). The results show that strain variation occurs within the species E. meleagrimitis and extreme caution should be used in identifying species of Eimeria from the turkey by the oocyst characters.

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.

Studies to determine the taxonomic status of Eimeria mitis , Tyzzer 1929 and E. mivati , Edgar and Seibold 1964

We have examined several taxonomic features of a number of strains of Eimeria from many sources world wide. The strains were isolated on the basis of their small spherical (or sub-spherical) oocysts. From a study of mean oocyst dimensions, electrophoretic variation of enzymes, ability to develop in embryonated eggs, absence of gross lesions in heavily infected chickens, and cross-immunity, all the strains were found to belong to one species. For convenience, the parasites when isolated, were referred to as strains of E. mitis/mivati-type, but after characterization they were clearly found to be E. mitis. In contrast, a laboratory strain of E. mivati supplied to one of us (M.W.S.) was found to be a mixture of E. acervulina and E. mitis. Evidence from these and other studies supports the notion that E. mivati is a nomina dubia.