Comparison Between Effects of Standard Feed and Whole Wheat Supplemented Diet on Experimental Eimeria tenella and Eimeria maxima Infections in Broiler Chickens

The effects of experimental infections with Eimeria tenella (Experiment 1, n = 144) or E. maxima (Experiment 2, n = 216) in broiler chickens fed whole wheat, with or without access to grit, as compared to a standard pelleted feed were studied. Inclusion of whole wheat was gradually increased up to 30% at 3 weeks of age. Grit was given separately. The chickens were kept on litter in a parasite-free environment with free access to water and feed. At 3 weeks of age half the number of chickens were individually inoculated with 500 sporulated oocysts of E. tenella (Experiment 1) or 3 000 sporulated oocysts of Eimeria maxima (Experiment 2), and the remaining birds were kept separate as uninfected controls. Neither coccidiostats nor growth enhancers were used. Oocyst concentration was determined from each group separately. Intestinal lesions were scored on 6 birds per feed regime 7 d postinoculation, and on the remaining birds at slaughter. Diet had no significant effect on bird performance during infection. However, there was an indication that the E. maxima infection had more negative effect on weight gain in birds given standard feed than in those given whole wheat supplement, but the difference was not significant (p<0.09). The number of oocysts shed or mean intestinal lesion scores did not differ between diets in either experiment. In both experiments, the number of Clostridium perfringens was higher in the caeca of inoculated birds, but there were no differences between diets.     

Eimeria acervulina, E. brunetti, and E. maxima: pathogenic effects of single or mixed infections with low doses of oocysts in chickens.

The pathogenic effects of E. acervulina, E. brunetti, and E. maxima were modified when chickens received mixed infections with these species.Six-week-old chickens were inoculated with doses of 20,000 oocysts of E. acervulina, 1250 oocysts of E. brunetti, and 5000 oocysts of E. maxima given as a single or mixed infection.Typical signs of coccidiosis were apparent in chickens infected with a single Eimeria sp. When birds were given infections composed of two species, the weight loss was greater than that due to either given alone but when three species were given, weight loss was slightly less than that due to infection will E. brunetti alone. Oocyst production due to E. acervulina tended to be similar in birds given this species alone or with E. brunetti. Output fell to less than 50% when E. acervulina was administered with E. maxima. Oocyst production due to E. brunetti and E. maxima decreased when these species were inoculated together and when they were administered with E. acervulina. Lesions of E. acervulina and E. brunetti were superimposed on those of E. maxima in birds given mixed infections.Growth retardation was not evident in chickens inoculated with E. acervulina alone, although weight loss increased when this species was administered with either E. brunetti or E. maxima.     

Eimeria maxima: characteristics of attenuated lines obtained by selection for precocious development in the chicken

Both the Weybridge strain and a mixture of six laboratory and field strains of Eimeria maxima have been attenuated by selection for early maturation of oocysts during serial passage in chickens. The prepatent times of the resultant precocious lines produces after selection were reduced from approximately 120 hr to less than 107 hr, and their reproduction and pathogenicity were less than those of the parent strains. Chickens which had been inoculated with a small number of oocysts of the Weybridge precocious or mixed field isolate precocious lines were immune to subsequent challenge with the parent strains. In a comparison made between the endogenous development of the precocious lines and their parent strains, it was found that asexual multiplication of the precocious lines was reduced, due to the earlier onset of gametogony. The results of this study also indicate that the parent (i.e., normal) strains of E. maxima probably undergo a minimum of four generations of schizogony.     

Immunological differences in Eimeria maxima: effect of a mixed immunizing inoculum on heterologous challenge.

The immunological differences known to exist between laboratory strains of Eimeria maxima was confirmed. Protection against challenge with different strains or field isolates of the species could be achieved by including small numbers (25 oocysts) of each in the immunizing inoculum. Similar protection was obtained when 4 distinct populations which were allowed to interbreed were used in the immunizing inoculum. This hybrid mixture of E. maxima was used to immunize chickens against challenge with 7 new isolates of E. maxima from poultry houses in different parts of England. The results show that although immunological differences exist within E. maxima good protection against many strains of this species may be achieved by initial infection with the hybrid mixture of E. maxima.     

Infections with Eimeria maxima and Eimeria acervulina in the fowl: effect of previous infection with the heterologous organism on oocyst production.

Judged by oocyst production, infections with Eimeria acervulina in birds immunized with E. maxima were consistently higher than in birds which had not been immunized. Oocyst production of E. maxima in birds previously infected with E. acervulina was greater, in three out of four experiments, than in control chickens, but some of the differences were slight. The findings are discussed but no satisfactory explanation can be offered. In general there was little or no difference between the oocyst production of the individual species when present as single or mixed infections.     

The immunity arising from continuous low-level infection with Eimeria maxima and Eimeria acervulina.

Chicks were given daily inoculations of 1 or 5 oocysts of Eimeria maxima or 5 or 20 oocysts of E. acervulina. The inoculations ceased after 20 days with E. maxima or 25 days with E. acervulina when oocyst production had stopped. The responses to subsequent heavy challenges showed that with both species the immunity arising from the serial inoculations was stronger and/or more enduring than that produced by single inoculations of comparable numbers of oocysts.     

Eimeria acervulina, E. brunetti, and E. maxima: immunity in chickens with low multiple doses of mixed oocysts.

Young chickens inoculated with multiple low doses of mixed oocysts of Eimeria acervulina, E. brunetti, and E. maxima had a high level of resistance to reinfection with a mixed challenge dose on Day 28, Day 84, or Day 140. Immunity was enhanced when the number of immunizing doses was increased from three to four. Resistance was also high in birds maintained on a proprietary mixture of amprolium, ethopabate, and sulphaquinoxaline (Pancoxin-Merck, Sharp and Dohme Ltd.) during immunization, although immunity to E. acervulina was lower in these birds. Oocyst production was lower in birds given mixed infections as compared with that of birds given pure infections with similar doses of oocysts. Competition between species did not inhibit the development of immunity in birds given low doses of mixed oocysts.     

Eimeria maxima (Apicomplexa): a comparison of sporozoite transport in naive and immune chickens

This study compared the early stages of infection in naive and immune chickens infected with Eimeria maxima. An immunoperoxidase stain was developed and used to detect sporozoites and early schizonts in tissue sections of intestinal epithelium. A significantly higher proportion of sporozoites was present in the crypts of naive chickens, 48 hr postinoculation of oocysts, compared to immune chickens. Sporozoites in immune birds tended to remain in the lamina propria rather than migrate to the crypts. Sporozoites were found within intraepithelial lymphocytes (IEL's) in the epithelium, the lamina propria, and the crypts of both naive and immune chickens. Parasites in IEL's of immune birds at the ultrastructural level and there were no apparent morphological abnormalities. Livers and spleens, of both immune and naive chickens that had been inoculated with Eimeria maxima, produced patent infections when fed to susceptible chickens. Infections could be transferred up to 72 hr post-inoculation of the donor birds. Peak oocyst production in the recipient birds occurred 7-8 days after the transfers. This time period approximates the prepatent period in a natural infection and thus implies that the extraintestinal stage was a sporozoite.     

Effects of simple and disposable chicken cages for experimental Eimeria infections

During experimental Eimeria infections in chickens, facilities are often contaminated by fecal oocysts known to be highly resistant to both chemical and enzymatic treatments. Thus, studies using experimental Eimeria infections have been limited due to the difficulty of complete elimination of residual oocysts from both cages and facilities. To overcome this limitation, simple, inexpensive, and disposable cages were constructed from cardboard boxes and tested during experimental Eimeria maxima infections. The cages were used in animal rooms with only a 1.7% evidence of coccidia contamination between adjacent cages. No significant differences in fecal oocyst output and body weight gain were noted between animals housed in disposable cages and animals housed in wire control cages. This cage design is a useful means for preventing oocyst contamination during experimental conditions, suggesting that this disposable cage design could be used for other avian infectious disease studies.     

Viability of preserved Cryptosporidium baileyi oocysts

The present study was undertaken to determine the viability and infectivity of oocysts of Cryptosporidium baileyi that had been stored from 1 to 40 months at 4 degrees C preserved in 2.5% potassium dichromate solution. Oocysts of C. baileyi were purified from the feces of experimentally infected chickens using discontinuous sucrose gradients. Subsequently, the purified oocysts were suspended in 2.5% potassium dichromate solution at a concentration of 1 x 10(7) organism/ml, and their viabilities were assessed by nucleic acid staining, histologic examination, and infectivity to 2-day-old chickens. All chickens inoculated with oocysts that had been stored for 1-18 months developed patent infections, while chickens infected with older oocysts remained uninfected. Between 5.8% and 82.2% of the oocysts, stored at 4 degrees C in 2.5% potassium dichromate solution, were found to be viable, as determined by nucleic acid staining. Parasite colonization in the bursa of Fabricius was detected in the microvillus border of bursal epithelium. The finding that C. baileyi oocysts remain infective to chickens for at least 18 months offers important time-saving advantages to investigators who frequently require large numbers of oocysts.     

Effect of the anticoccidial arprinocid on production, sporulation, and infectivity of Eimeria oocysts

Medication of broilers with arprinocid [MK-302, 9-(2-chloro-6-fluorbenzyl adenine)] had 3 distinct effects on oocysts; (1) the number of oocysts produced was decreased, (2) fewer of the oocysts sporulated, and (3) those oocysts which did sporulate were less infective than those from unmedicated birds. The drug level necessary to prevent passage of oocysts depended on the species and strain of coccidia. To essentially eliminate oocyst production (less than 5% of controls) required medication with the following levels of arprinocid: 70 ppm with Eimeria maxima; 60 ppm with E. mivati, E. E. necatrix, and E. brunetti; and 50 ppm with E. tenella. With E. acervulina, oocysts were completely eliminated by 60 ppm of arprinocid with one field strain but were still numerous at 70 ppm with a second field strain. Oocysts recovered from birds on medication often failed to sporulate. No sporulation was seen at drug levels of 30 ppm or above with E. maxima and E. mivati. The level of arpinocid required to prevent sporulation with other species depended on the strain being studied, but varied from 30 ppm to 70 ppm. The oocysts of E. acervulina, E. mivati, E. tenella, and E. brunetti recovered from medicated birds that subsequently sporulated, were less infective when inoculated into susceptible birds, than oocysts from unmedicated birds. Oocysts from low medication level with E. necatrix (30 ppm) and E. maxima (10 ppm), once sporulated, were as infective as oocysts from unmedicated control birds, even though the numbers produced were less. No differences were detected in the time oocysts were produced between medicated and unmedicated birds infected with E. acervulina, E. maxima, E. brunetti, and E. tenella.     

Eimeria spp. of domestic fowl: the migration of sporozoites intra- and extra-enterically

Chickens were dosed orally with sporulated oocysts of Eimeria acervulina, E. brunetti, E. maxima, or E. praecox and the subsequent presence, in various tissues, of parasites capable of inducing patent infections was detected by transferring the tissues to coccidia-free recipients. Similar results were obtained with each of the 4 species studied, irrespective of whether initial development occurs in the superficial (E. praecox, E. brunetti) or crypt (E. acervulina, E. maxima) epithelium. Infection was transferable by gut scrapings and liver homogenates at all time intervals (3, 6, 12, 18, 24, and 36 hr postinoculation) studied. Infection was also transferable with blood and with splenic homogenates but not consistently. Transfers made within a short time of the inoculation of donors were more successful in producing patent infections in the recipients. In all transfers the prepatent period was normal for the species. These findings suggest that sporozoites enter the mucosa very shortly after inoculation, and some of them pass to the liver and spleen and then leave these tissues at a somewhat slower rate, possibly to reenter the mucosa. Sporozoites in the lamina propria of the gut were found within host mononuclear cells in all 4 species studied. Most of the cells harbouring E. maxima and some of those with E. praecox were identified as intraepithelial lymphocytes while all others could only be identified as agranular mononuclear cells that were not characteristically macrophages.     

Partial protection against Eimeria acervulina and Eimeria tenella induced by synthetic peptide vaccine

Coccidiosis is a major parasitic disease of poultry industry and an ideal vaccine should induce long-lasting cross-species protective immunity. Broiler chickens (Cobb 500) were inoculated with single, double or triple injections of a synthetic peptide (derived from sequences of Eimeria acervulina and Eimeria tenella antigens) homogenized in Freund's complete and incomplete adjuvants. The immune responses to the vaccine were assessed by evaluation of antibody and lymphocyte proliferation responses, and the degree of resistance of vaccinated chickens to challenge with sporulated oocysts of E. acervulina or E. tenella determined by comparison of their oocyst output with those of control chickens. The results indicated that the synthetic peptide vaccine induced a high level of antibody and cellular responses associated with partial cross-species protection against challenge with sporulated oocysts of E. acervulina or E. tenella.     

Pathogenic mechanisms not operating in Eimeria necatrix infections.

Having investigated certain aspects of Eimeria necatrix coccidiosis in chickens, workers of the Hannover Veterinary School postulated "that death following a single inoculation of a large number of oocysts is due to an alarm reaction and not a specific pathogenic action of the parasites". Because this hypothesis is somewhat revolutionary in its consept, several pieces of evidence on which it is based and several logical deductions which can be made from it have been examined. It has been confirmed that injection of chichens with cysteamine or 5-hydroxytryptamine 30 min before inoculation of the birds with a lethal dose of E. necatrix oocysts reduces subsequent mortality; the reason for this, however, appears not to be the neutralisation of the proposed shock reaction, but rather an inhibition of the excystation process, brought about indirectly through the host. Inoculation of chickens with a non-lethal dose of E. necatrix oocysts 30 min before inoculation with a lethal dose of oocysts was followed by increased mortality rather than the decreased mortality which the hypothesis would predict. Treatment of chickens with sulphadimidine starting 48 h after inoculation resulted in survival of the birds rather than death which would ensue if in fact mortality was due to a shock reaction irreversibly initiated at the time of inoculation. A direct effect of sulphadimidine on the parasite has been shown both in vivo and in vitro.     

Eimeria acervulina,E. brunetti,E. maxima, and E. necatrix: Low doses of oocysts to immunize young chickens

Resistance to reinfection varied with the species of Eimeria and with the number of oocysts in the inoculum. Chickens immunized with doses of 20,000 and 80,000 oocysts of E. acervulina, 312 and 1250 oocysts of E. brunetti or E. necatrix, or 1250 and 5000 oocysts of E. maxima at 2 and 4 weeks of age, respectively, were almost completely immune to a challenge dose at 6 weeks of age. Resistance was slightly less in chickens immunized with 1250 and 5000 oocysts of E. acervulina or 312 and 1250 oocysts of E. maxima. Birds given three immunizing infections of 1250, 5000, and 20,000 oocysts of E. maxima were completely immune 8 weeks after the last dose. Resistance was slightly less in birds immunized with similar doses of E. brunetti or E. necatrix. Doses of 20,000, 80,000, and 320,000 oocysts appeared necessary to confer a high level of immunity to E. acervulina. More than three low doses of oocysts appear necessary to induce a complete and enduring immunity against a high challenge for E. acervulina, E. brunetti, and E. necatrix. Higher immunizing doses would not be satisfactory due to the pathogenic effects of the coccidia after the initial infection.     

A chicken embryo model for the maintenance and amplification of Cryptosporidium parvum and Cryptosporidium baileyi oocysts

Cryptosporidium is a genus of apicomplexan parasites that inhabit the respiratory and gastrointestinal tracts of vertebrates. Research of these parasites is limited by a lack of model hosts. This study aimed to determine the extent to which infection at the embryo stage can enhance the propagation of Cryptosporidium oocysts in chickens. Nine-day-old chicken embryos and one-day-old chickens were experimentally infected with different doses of Cryptosporidium baileyi and Cryptosporidium parvum oocysts. Post hatching, all chickens had demonstrable infections, and the infection dose had no effect on the course of infection. Chickens infected as embryos shed oocysts immediately after hatching and shed significantly more oocysts over the course of the infection than chickens infected as one-day-olds. In chickens infected as embryos, C. baileyi was found in all organs except the brain whereas, C. parvum was only found in the gastrointestinal tract and trachea. In chickens infected as one-day-olds, C. baileyi was only found in the gastrointestinal tract and trachea. Chickens infected as embryos with C. baileyi died within 16 days of hatching. All other chickens cleared the infection. Infection of chickens as embryos could be used as an effective and simple model for the propagation of C. baileyi and C. parvum.     

A Redescription of the Life Cycle of Eimeria mitis Tyzzer, 1929

Ten-day-old broiler chickens were inoculated with oocysts of a characterized strain of Eimeria mitis , and tissues were fixed at 4, 8, or 24-h intervals after inoculation for histopathological examination. Tissue collections were initiated at the time of inoculation and extended up to 168 h postinoculation. The preferred site of development of E. mitis was found to be the ileum although more limited development of the parasite also took in the jejunum, cecal pouches, cloaca, and bursa of Fabricius. No distinctive and consistent intestinal lesions were macroscopically evident even in heavily parasitized chickens. The prepatent period was approximately 92 h postinoculation. The histopathological features of the E. mitis infections were characterized using conventional bright-field microscopy as well as both scanning and transmission electron microscopy. No extra-intestinal development of the parasite was observed.     

A redescription of the life cycle of Eimeria mitis Tyzzer, 1929

Ten-day-old broiler chickens were inoculated with oocysts of a characterized strain of Eimeria mitis, and tissues were fixed at 4, 8, or 24-h intervals after inoculation for histopathological examination. Tissue collections were initiated at the time of inoculation and extended up to 168 h postinoculation. The preferred site of development of E. mitis was found to be the ileum although more limited development of the parasite also took in the jejunum, cecal pouches, cloaca, and bursa of Fabricius. No distinctive and consistent intestinal lesions were macroscopically evident even in heavily parasitized chickens. The prepatent period was approximately 92 h postinoculation. The histopathological features of the E. mitis infections were characterized using conventional bright-field microscopy as well as both scanning and transmission electron microscopy. No extra-intestinal development of the parasite was observed.     

The effect of cyclosporin A on the development of Eimeria in non-specific hosts.

The role of T lymphocytes on the development of turkey coccidia in chickens was investigated to further document the involvement of immune mechanisms in the reactions of non-specific hosts to infections with species of Eimeria. All chickens treated with the T cell-specific immunosuppressive drug, cyclosporin A (CsA), 1, 2 or 3 days before or for 3 consecutive days immediately before inoculation with sporulated oocysts of Eimeria from the turkey, shed oocysts in their feces 7–12 days after inoculation. Those chickens treated with CsA after inoculation produced no oocysts although in one experiment a small number of oocysts were discharged by birds injected with CsA 1 day after inoculation. High serum levels of CsA were maintained in the CsA-treated chickens for at least 24 h post-inoculation with the oocysts. Immunosuppressive activity of the drug was determined by measuring lymphocyte blastogenesis in response to concanavalin A. These results demonstrate that the suppression of T lymphocyte activity in a non-specific host early during an infection with a heterologous species of Eimeria permits the complete intracellular development of the parasite. Our findings are suggestive of a role for T lymphocytes in preventing the development of Eimeria in non-specific hosts possibly via a lymphokine-mediated mechanism.