Development of attenuated strains of Eimeria in the turkey

DEVELOPMENT OF ATTENUATED STRAINS OF EIMERIA IN THE TURKEY

Sponsoring Institution

National Institute of Food and Agriculture

Project Status

COMPLETE

Funding Source

ANIMAL HEALTH

Reporting Frequency

Annual

Accession No.

0206140

Grant No.

(N/A)

Cumulative Award Amt.

(N/A)

Proposal No.

(N/A)

Multistate No.

(N/A)

Project Start Date

Jan 1, 2006

Project End Date

Sep 30, 2011

Grant Year

(N/A)

Program Code

[(N/A)]- (N/A)

Recipient Organization
UNIVERSITY OF ARKANSAS
(N/A)
FAYETTEVILLE,AR 72703

Performing Department
Poultry Sciences

Non Technical Summary
The objective of this project is to develop lines of Eimeria species that can be used to safely vaccinate turkeys against the important parasitic disease coccidiosis that is widespread in turkey flocks. The project aims to develop an alternative method of control that does not involve the use of drugs.

Animal Health Component

(N/A)

Research Effort Categories

Basic

(N/A)

Applied

(N/A)

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
311	3230	1110	50%
311	4050	1110	50%

Knowledge Area
311 - Animal Diseases;

Subject Of Investigation
4050 - Protozoa; 3230 - Turkey, live animal;

Field Of Science
1110 - Parasitology;

Keywords

Goals / Objectives
Coccidiosis is an important disease of the turkey caused by parasites of the genus Eimeria and millions of dollars are spent every year on anticoccidial medication. Despite the use of drugs, however, the parasites remain widespread and are the cause of significant economic loss. In recent years the use of drugs in animal feeds has come under close scrutiny and in some Countries they have been banned from use. There is an urgent need, therefore, to find reliable, safe, alternative methods of control. Vaccines are available for immunizing turkeys against coccidiosis but these are based upon the oral ingestion of live, infectious oocysts of virulent isolates of the parasites. Thus they have the potential, if not carefully managed, to cause the disease they are intended to prevent. Live vaccines have been developed for the chicken comprising attenuated lines of Eimeria with reduced pathogenicity that are capable of inducing a protective immune response in the bird. Such vaccines are inherently safer than their potentially virulent counterparts. So far attenuated lines have not been developed for the turkey. Attenuated lines of Eimeria species will be developed in the turkey for potential use in a vaccine to control coccidiosis in this host. Attenuation will be achieved by selection for precocious (early) development and a consequent reduction in pathogenicity of the selected lines will be demonstrated. The prepatent and patent period of the attenuated lines will be established and any differences in stages of the life cycle that may be responsible for attenuation determined. The ability of the attenuated lines to induce a protective immune response in the turkey against challenge with homologous and heterologous strains of Eimeria obtained from principal turkey-growing regions of the USA will be investigated.

Project Methods
Vaccines against coccidiosis have been developed in the chicken based upon live attenuated oocysts of all species of Eimeria that parasitize this host; the organisms have lost their pathogenicity but retain the ability to stimulate a protective immune response in the bird. It is hypothesized that the methodology used to develop such lines in the chicken can also be employed to develop attenuated lines of Eimeria in the turkey. Experiments will be carried out with pure lines of turkey Eimeria that have been maintained in our laboratory and were derived from a single oocyst. Poults will be infected with a parent line and from 96 hours post-infection feces will be processed for second generation oocysts. The process will be repeated for at least twenty generations or until a significant reduction in the prepatent period is observed. The prepatent period, pathogenicity, and immunogenicity of the selected and parental lines will be compared. Groups of birds will be inoculated with large numbers of oocysts of the selected and parent lines and their intestines examined histologically for developmental stages of the parasite. Sections taken from ten regions of intestine will be examined. By comparing the attenuated line with the parent line it should be possible to identify the number of schizont generations and any morphological differences (e.g. schizont size and numbers of merozoites) that may be associated with attenuation. Immunogenicity of the attenuated and parental lines will be compared in floor-pens by inoculating poults at one-day of age with 100 oocysts of the respective lines. Four weeks later they will be challenged with a dose of the parental strain sufficient to cause a reduction in weight gain without mortality. Additional poults will be reared in pens maintained in an isolation facility but not inoculated to serve as susceptible-challenged and susceptible-nonchallenged controls. Procedures to evaluate heterologous protection will be similar except that isolates will be obtained from three separate regions turkey-growing regions of the US (North Carolina, Arkansas, and Minnesota). Thus, attenuated lines of Eimeria will be developed by repeated propagation of the parasites and collection of the very first oocysts that are produced following inoculation. After approximately 10-20 propagations it is anticipated that the prepatent period will be reduced and the fecundity of the parasites lowered. Changes responsible for reduced development time may include loss of a schizont generation and reduction in the numbers of viable infective stages (merozoites). These changes in the life cycle will confer reduced pathogenicity but immunogenicity will be retained thus making them suitable candidates for inclusion in a putative turkey coccidiosis vaccine.

Progress 01/01/06 to 09/30/11

Outputs
OUTPUTS: Coccidiosis is a widespread disease of turkeys caused by protozoan parasites of the genus Eimeria that is controlled by the inclusion of drugs in the feed. We conducted a survey of isolates of Eimeria from turkey farms throughout the USA and showed resistance to commonly used drugs was widespread (Chapman and Rathinam, 2007; Rathinam and Chapman, 2009). In view of this, alternative methods for control, such as vaccination, are desirable. Unfortunately commercial vaccines comprise live organisms that are potentially pathogenic. Our approach has been to develop an attenuated line of one species (E. meleagridis) for use in vaccination and this has been successful (Matsler and Chapman, 2007). Selection resulted in a line with a life cycle of reduced duration, due to a reduced number of asexual generations, and reduced numbers of parasites within those stages. The selected line had lost its pathogenicity to young turkeys but was capable of inducing a solid immune response to challenge with large numbers of the parasite. Lack of funding has prevented this work being extended to other species of Eimeria. We also provided new information on the life cycle of this species and its pathogenicity (Matsler and Chapman, 2007). Unlike other species that are restricted in development to one location in the gut, this species was found to develop in epithelial cells of the lining of the small intestine and the ceca. Four cycles of asexual multiplication were shown to occur in the host. No lesions were apparent in the intestine but infection resulted in a significant reduction in weight gain suggesting that the parasite interfered with the absorption of nutrients by the gut. During the course of this work it became evident that no published information was available on the cellular immune responses shown by turkey poults following infection with Eimeria parasites. We showed a significant inflammatory response to a primary infection with the widespread and pathogenic species E. adenoeides (Gadde et al., 2009). These included elevated concentrations of monocytes, eosinophils, and CD4+ and CD8+ lymphocyte subpopulations in peripheral blood. Cellular immune responses in the ceca, the region of the gut parasitized, were also investigated. Increased expression of the cytokines CXCLi2, IL10, IFNγ, IL1β, and IL13 was noted (Gadde et al., 2011). The increased leukocyte infiltration, alterations in the lymphocyte subpopulations, and changes in expression of chemokines and cytokines are an indication of the cell mediated immune mechanisms occurring in the host due to infection. We have also undertaken, in collaboration with the USDA Beltsville laboratory, molecular characterization and phylogenetic analysis of Eimeria species in the turkey and shown similarities between turkey and chicken species that develop in different regions of the gut. This may indicate two separate ancestral colonizations of these hosts by Eimeria parasites (Miska et al., 2010). A comprehensive review of coccidiosis in the turkey has been published (Chapman, 2008). PARTICIPANTS: Chapman, H. D. PhD, ARCS. Principal Investigator Rathinam, T. Program Associate Matsler. P. BS. Program Associate Gadde U.D. BVS, Graduate Research Assistant TARGET AUDIENCES: Audience includes turkey farmers, turkey industry, poultry veterinarians,research scientists. Results communicated by invited presentations at poultry meetings both in the USA and abroad and popular articles in poultry magazines. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
The objective of this project was to develop lines of Eimeria species that can be used to safely vaccinate turkeys against the important parasitic disease coccidiosis that is widespread in turkey flocks. The project aimed to develop an alternative method of control that does not involve the use of drugs. This was considered important because we demonstrated the widespread occurrence of resistance to the common drugs used to control coccidiosis in turkeys. This work was the first comprehensive survey of resistance conducted in the United States. We were successful in developing an attenuated line of one species that infects the turkey, E. meleagridis. We were able to demonstrate unique aspects of the life cycle and pathogenicity of this organism previously unpublished. This was the first demonstration of this important pathogen in Arkansas. Unfortunately lack of funding prevented the work being extended to other important species that infect the turkey. We have also conducted the most extensive studies on cellular immune responses to Eimeria infection in the turkey ever published. A better understanding of such immune mechanisms should facilitate the development of vaccines against coccidiosis in the future. In collaborative studies, isolates of two pathogenic species of Eimeria that infect the turkey have been cloned from a single oocyst and DNA extracted for molecular analysis. DNA from three genomic regions, internal transcribed spacer regions (ITS 1 & 2), the cytochrome oxidase subunit (cox-1), and small subunit ribosomal RNA (SSU) were PCR amplified, cloned, and sequenced. The results suggest that turkey Eimeria form a specific clade distinct from species that infect other galliforme birds. This work is the first molecular characterization of Eimeria from turkeys.

Publications

Gadde, U., H. D. Chapman, T. Rathinam, and G. F. Erf. (2010). Altered leukocyte profiles in turkey poults following a primary infection with Eimeria adenoeides. 55th Annual Meeting of the American Association of Veterinary Parasitologists. Atlanta, GA.
Gadde, U., H. D. Chapman, T. Rathinam, and G. F. Erf. (2010). Acquisition of immunity to the protozoan parasite Eimeria adenoeides in turkey poults and the peripheral blood leukocyte response to a primary infection. Southern Conference on Avian Diseases, Atlanta, GA.
Rathinam, T. and H. D. Chapman. (2010). Sensitivity of isolates of Eimeria from turkey flocks to the anticoccidial drugs amprolium, clopidol, diclazuril, and monensin. Southern Conference on Avian Diseases, Atlanta, GA.
Rathinam, T. and H. D. Chapman. (2009). Sensitivity of isolates of Eimeria from turkey flocks to the anticoccidial drugs amprolium, clopidol, diclazuril, and monensin. Avian Diseases 53:405-408.
Gadde, U., H. D. Chapman, T. Rathinam, and G. F. Erf. (2009). Acquisition of immunity to the protozoan parasite Eimeria adenoeides in turkey poults and the peripheral blood leukocyte response to a primary infection. Poultry Science 88:2346-2352.
Chapman, H. D. (2008). Coccidiosis in the turkey. Avian Pathology 37:205-223.Matsler, P. L. and H. D. Chapman. (2007). Selection for early (precocious) development of Eimeria meleagridis in the turkey. Avian Diseases 51:122-124.
Chapman, H. D. and T. Rathinam. (2007). Sensitivity of field isolates of Eimeria to monensin in the turkey. Avian Diseases 51:954-957.
Matsler, P. L. and H. D. Chapman. (2006). Characterization of a strain of Eimeria meleagridis from the turkey. Avian Diseases 50:599-604.
Miska, K. B., T. Rathinam, R. S. Schwarz, and H. D. Chapman. (2009). Molecular characterization of Eimeria species infecting turkeys. In: Convention Notes 146th AVMA convention, Seattle.
Chapman, H. D. (2008). Coccidiosis in the turkey: the contribution of Michael Clarkson. In: Current topics in veterinary research and education. 62nd meeting of the Association for Veterinary Teaching and Research Workers, Scarborough, UK.
Chapman, H. D. S. R. Clark, and M. Marien (2008). Turkey coccidiosis, World Poultry, 24: No. 10.
Chapman, H. D. and T. Rathinam. (2007). Characterization and attenuation of Eimeria meleagridis in the turkey. In: Proceedings of the American Association of Veterinary Pathologists Meeting, Washington, DC.
Chapman, H. D. (2007). Future prospects for coccidiosis control in the turkey. In: Proceedings of the 1st Turkey Science and production Conference. Macclesfield, UK.
Chapman, H. D. (2006). Managing coccidiosis in turkeys. Poultry Symposium, Springdale, AR.
Chapman, H. D., B. Roberts, M. W. Shirley, and R. B. Williams. (2005). Guidelines for evaluating the efficacy and safety of live anticoccidial vaccines, and obtaining approval for their use in chickens and turkeys. Avian Pathology 34: 279-290.
Chapman, H. D. (2005). Turkey coccidiosis: historical overview and future prospective toward prophylaxis and control. In: Proceedings of the 3rd International Symposium on turkey production. Berlin, Germany.

Progress 01/01/10 to 12/31/10

Outputs
OUTPUTS: Extensive studies with turkeys have documented the widespread incidence of resistance to widely used drugs and underly the need for development of a turkey vaccine. We have demonstrated that a species of Eimeria previously thought to be nonpathogenic (Eimeria meleagridis)is in fact virulent for young turkeys and have shown for the first time that this is present in Arkansas. This parasite has now been attenuated by selection for precocious development and is capable of immunizing the bird. However, we find that successful vaccination strategies require better knowledge of the cellular immune responses that occur in the bird following infection. Hence we have initiated studies designed to elucidate such mechanisms. The goal of this research is to provide the turkey industry with a science based understanding of processes that underly successful vaccination of turkeys against coccidiosis. We have collaborated with the USDA in a study designed to understand the evolutionary relationships of Eimeria parasites that infect turkeys and chickens. Molecular characterization and phylogenetic analysis has elucidated that at least two ancestral colonizations of these hosts occurred. One lineage develops in the ceca while the other develops in the small intestine. Thus the cecal parasites E. tenella in the chicken and E. adenoeides in the turkey are more closely related than species from both hosts that colonize the upper intestinal tract. These results have been disseminated by means of talks, lectures, refereed journal publications, invited reviews, and popular presentations in the USA and overseas. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Humoral and cellular immune responses in peripheral blood, and cellular responses, chemokine, and cytokine profiles in gut tissue were investigated following an infection with E. adenoeides, a protozoan parasite of the genus Eimeria that develops in the ceca and one of the most important pathogens in the turkey. CD4+ and CD8+ lymphocytes in the spleen, determined by direct immunofluorescent staining and flow cytometry, were elevated following infection and the percent area occupied by CD4+ and CD8+ cells was significantly greater. Inflammation, assessed by scoring the extent of cellular infiltration of leukocytes in sections of ceca, was significantly higher in infected poults. Gene expression of the chemokine CXCLi2, the cytokines IL-10, IL-13, IL-1β, IFN γ, and IL-10 were also elevated. Alteration in lymphocyte subpopulations and expression of a chemokine and cytokines has not previously been reported from turkeys infected with Eimeria.

Publications

Miska, K. B., Schwarz, R. S., Jenkins, M. C. Rathinam, T. and H. D. Chapman. 2010. Molecular characterization and phylogenetic analysis of Eimeria from turkeys and gamebirds: implications for evolutionary relationships in galliform birds. Journal of Parasitology 96:982-986
Gadde, U., Chapman, H. D., Rathinam, T. R., and G. F. Erf. (2010). Cellular Immune responses, chemokine, and cytokine profiles in turkey poults following infection with the intestinal parasite Eimeria adenoeides. Poultry Science. In Press.
Gadde, U., Chapman, H.D., Rathinam, T., and Erf, G. F. 2010. Acquisition of immunity to the protozoan parasite Eimeria adenoeides in turkey poults and the peripheral blood leukocyte response to a primary infection (page 77). Southern Conference on Avian Diseases, International Poultry Scientific Forum, January 25, 2010, Atlanta, GA.
Rathinam, T., and Chapman H. D. 2010. Resistance of field isolates of Eimeria to the anticoccidial drugs amprolium, clopidol, diclazuril, and monensin in the turkey (Page 78). Southern Conference on Avian Diseases, International Poultry Scientific Forum, January 25, 2010, Atlanta, GA.
Chapman, H. D. 2010. Forty years of monensin for the control of coccidiosis. European Coccidiosis Discussion Group Meeting, May 27, 2010, Veterinary Laboratories Agency, Weybridge, UK.
Chapman, H. D., Jeffers, T. K., and R. B. Williams (2010). Forty years of monensin for the control of coccidiosis. Poultry Science 89:1788-1801.
Gadde, U., T. Rathinam, H. D. Chapman, G. F. Erf. 2010. Leukocyte profile of turkeys infected with Eimeria adenoeides and development of immunity during subsequent challenge. Pages 323-324. In: Proceedings of the XXVII Annual Conference and National Symposium of Indian Poultry Science Association. September 16-18, 2010, Chennai, India.
T. Rathinam, and H. D. Chapman. Resistance of field isolates of Eimeria to the anticoccidial drugs amprolium, clopidol, diclazuril and monensin in the turkey. Pages 331-332. In: Proceedings of the XXVII Annual Conference and National Symposium of Indian Poultry Science Association. September 16-18, 2010, Chennai, India.

Progress 01/01/09 to 12/31/09

Outputs
OUTPUTS: NON-TECHNICAL SUMMARY: Coccidiosis is a widespread disease of considerable economic importance to the turkey industry, as is evident by the fact that many millions of dollars are spent annually on its control. Despite this little research has been conducted on the causative organisms - protozoan parasites of the genus Eimeria. Unfortunately current methods of control are unsatisfactory, resistance has developed against many of the drugs used to control the disease and the few available vaccines can cause the disease they are supposed to prevent. Better methods of control are hampered by lack of basic knowledge regarding life cycles of the parasites, their differentiation and speciation, pathology, pathogenicity, epidemiology, and immunogenicity. Furthermore almost no research is currently carried out on these important pathogens. The experiments reported here are designed to provide a baseline for future work on this disease. OBJECTIVE: Investigate coccidiosis in poultry and develop improved methods of control. PARTICIPANTS: H. D. Chapman. Principal Investigator T. Rathinam. Technical Support TARGET AUDIENCES: Professional poultry scientists, veterinarians. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
PROGRESS: In collaborative studies, isolates of two pathogenic species of Eimeria that infect the turkey have been cloned from a single oocyst and DNA extracted for molecular analysis. DNA from three genomic regions, internal transcribed spacer regions (ITS 1 & 2), the cytochrome oxidase subunit (cox-1), and small subunit ribosomal RNA (SSU) were PCR amplified, cloned, and sequenced. The results suggest that turkey Eimeria form a specific clade distinct from species that infect other galliforme birds. This work is the first molecular characterization of Eimeria from turkeys. We have investigated cellular mechanisms in the acquisition of immunity to Eimeria adenoeides in turkey poults and peripheral blood leukocyte responses to infection. Changes in white blood cell profiles (monocytes, eosinophils, CD4+ and CD8+ lymphocyte subpopulations) suggest initiation of both innate and adaptive cellular immune activities to cope with a parasitic intracellular pathogen. We have documented the extent of resistance to anticoccidial drugs used to control coccidiosis in the turkey. Isolates were obtained from turkey producing States throughout the USA and many proved resistant or partially resistant to the drugs. In a collaborative study, serum ovotransferrin has been shown to be a useful biomarker of inflammatory diseases in chickens and specifically for coccidiosis. IMPACT: parasites of the genus Eimeria that can be found in all turkey flocks and cause the disease coccidiosis cost the poultry industry millions of dollars per annum. The studies concerned with species identification, immunogenicity, and drug resistance provide baseline information upon which appropriate control measures can be developed. DISSEMINATION: These results have been disseminated by means of refereed publications, conference proceedings, articles in the poultry press, and lectures in the USA and overseas.

Publications

Chapman, H. D. 2009. A landmark contribution to Poultry Science, prophylactic control of coccidiosis in poultry. Poult. Sci. 88:813-815.
Rath, N.C., Anthony, N. B., Kannan, L., Huff, W. E., Huff, G. R., Chapman, H. D., Erf, G. F., & Wakenell, P. 2009. Serum ovotransferrin as a biomarker of inflammatory diseases in chickens. Poult. Sci. 88:2069-2074.
Rathinam, T. and Chapman, H. D. 2009. Sensitivity of isolates of Eimeria from turkey flocks to the anticoccidial drugs amprolium, clopidol, diclazuril, and monensin. Avian Dis. 53:405-408.
Gadde, U., Chapman, H. D., Rathinam, T. R. and Erf, G. F. 2009. Acquisition of immunity to the protozoan parasite Eimeria adenoeides in turkey poults and the peripheral blood leukocyte response to a primary infection. Poult. Sci. 88: 2346-2352.
Chapman, H. D. & Miska, K. 2009. Turkey coccidiosis, what a load of gobblers. European Coccidiosis Discussion Group Meeting, May 21, 2009, Institute for Animal Health, Compton, Berks, UK.
Miska, K. B., Rathinam, T. R., Schwarz, R. S. and Chapman, H. D. 2009. Molecular characterization of Eimeria species infecting turkeys. In Convention Notes.146th American Veterinary Medical Association Convention, July 11, 2009, Seattle.
Chapman, H. D. 2009. Coccidiosis and the poultry industry. Poultry Times January 30, 2009.
Chapman, H. D. 2009. Drugs, vaccines and natural products for coccidiosis control, will they help the poultry industry grow better chickens The Poultry Federation Annual Nutrition Conference, Bentonville, AR, September 8-10, 2009.

Progress 01/01/08 to 12/31/08

Outputs
OUTPUTS: NON-TECHNICAL SUMMARY: Coccidiosis is a widespread disease of poultry caused by protozoan parasites of the genus Eimeria that has been estimated to cost the United States poultry industry approximately $733 million per annum. Currently, coccidiosis is controlled by the inclusion of anticoccidial drugs in the feed. The most widely used compounds are a class of drugs known as the polyether ionophorous antibiotics. Little is known, however, regarding their efficacy in the field and whether they share a common mode of action. The sensitivity of isolates obtained from turkey farms throughout the USA was therefore investigated and it was shown that resistance to the two most widely used ionophores, monensin and lasalocid was widespread and that resistance to one drug was shared with the other (cross resistance). Concerns have been expressed regarding the use of drugs in poultry feeds and the possibility that drug residues might occur in poultry meat. We have investigated whether one drug, a synthetic chemical, can be transferred via poultry litter to subsequent generations of unmedicated birds. There is an urgent need to develop alternative methods of control such as by vaccination. We have completed our investigation to characterize the life cycle and pathogenicity of one species of Eimeria from the turkey and develop an attenuated strain for inclusion in a putative turkey vaccine. We are extending this investigation to other species of economic importance in the turkey. OBJECTIVE: Investigate coccidiosis in poultry and develop alternative means of control. APPROACH: Coccidia were isolated from fecal and litter samples from turkey flocks throughout the USA and their characteristics defined. Pathogenicity and drug sensitivity were determined in battery experiments. One isolate showing characteristics of E. adenoeides was cloned by micromanipulation from a single oocyst and utilized in immunological studies with the eventual goal to develop an attenuated strain suitable for use in a vaccine against coccidiosis. Floor pen experiments were undertaken to investigate the possible transmission of a drug via chicken litter. Residues in liver, breast, and thigh tissue were determined by an HPLC procedure specific for the compound concerned. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
PROGRESS: Experiments to investigate the use of drugs to control coccidiosis in poultry, the incidence and mechanisms of drug resistance, and the occurrence of certain drug residues in poultry tissue have been undertaken. Work on the development of attenuated strains suitable for inclusion in a vaccine against coccidiosis, a long term project continues. IMPACT: Parasites of the genus Eimeria that can cause coccidiosis in poultry are found in all turkey and chicken flocks and cost the industry millions of dollars per annum. It is important therefore to investigate present and future methods of control. The studies concerned with anticoccidial drugs, resistance to them and the development of strains suitable for vaccination facilitate better control of this disease. DISSEMINATION: These results have been disseminated by means of talks, lectures, refereed Journal, and popular publications in the USA and overseas.

Publications

Chapman, H.D. 2008. Coccidiosis in the turkey. Avian Pathology 37: 205-223.
Chapman, H.D., Clark, S. R. and Marien, M. 2008. Turkey coccidiosis importance and best control practices. World Poultry 24:10-12.
Chapman, H.D., Clark, S.R. and Marien, M. 2008. Turkey coccidiosis proper control demands effective prevention. World Poultry 24:13-15.
Chapman, H.D. 2008. Coccidiosis in the turkey: the contribution of Michael Clarkson (pp. 18). In: Current Topics in Veterinary Science and Education. 62nd Meeting of the Association for Veterinary Teaching and Research Workers, 17-20 March, Scarborough, UK.
Chapman, H.D. 2008. Efficacy of Avatec and Coban against isolates of Eimeria from turkey flocks (pp. 1-74). ALPharma Inc., NJ.
Chapman, H.D. 2008. Efficacy of Avatec against isolates of Eimeria from turkey flocks that are resistant to Coban (pp. 1-52). ALPharma Inc., NJ.
Chapman, H.D. 2008. Coyden residue study in broilers (pp. 1-27). Huvepharma, Inc.
Chapman, H.D. 2008. A landmark contribution to Poultry Science. Landmark symposium. Centennial meeting of the Poultry Science Association, Niagara Falls, ON, Canada.
Clark, S.R., Chapman, H.D., Somers, F. and Gussem, M. 2008. Efficacy of lasalocid against isolates of Eimeria from turkey flocks (pp. 24). 145th American Veterinary Medical Association Meeting, 19-22 July, New Orleans, LA.

Progress 01/01/07 to 12/31/07

Outputs
NON-TECHNICAL SUMMARY: Coccidiosis is an important disease of the turkey caused by parasites of the genus Eimeria and millions of dollars are spent every year on anticoccidial medication. Despite the use of drugs, however, the parasites remain widespread and are the cause of significant economic loss. In recent years the use of drugs in animal feeds has come under scrutiny and there is an urgent need to find alternative methods of control. Vaccines are available for immunizing turkeys against some species of Eimeria but these are based upon the administration of live parasites of virulent isolates that, if not carefully managed, have the potential to cause the disease they are intended to prevent. Live vaccines have been developed for the chicken comprising attenuated lines of Eimeria with reduced pathogenicity that are capable of inducing a protective immune response in the bird. In this study an attenuated line of one species that infects the turkey, E. meleagrimitis, was developed. This line has lost its pathogenicity but retains immunogenicity and, therefore, is a candidate for inclusion in vaccines to control coccidiosis in the turkey. OBJECTIVE: Develop an attenuated line of an important protozoan parasite of the turkey. APPROACH: Attenuation was achieved by serial propagation of the very earliest parasites produced during the patent period of parasite development. DISSEMINATION: These results have been disseminated to the scientific community and the poultry industry by means of talks, lectures, refereed, and popular publications.

Impacts
PROGRESS: Selection resulted in the development of a line with a life cycle of reduced duration, a consequence of a reduced number of asexual replicative generations (schizogony), and reduced numbers of infective parasites within those stages. The selected line had lost its pathogenicity to young turkeys but was capable of inducing a solid immune response to challenge with large numbers of the parasite. IMPACT: This is the first published report that it is possible to attenuate an economically significant protozoan parasite that infects the turkey. This species is widespread in the field and therefore it is important that an attenuated line of E. meleagridis be included in vaccines for immunizing turkeys against coccidiosis, thus providing an alternative to medication for control of this common disease.

Publications

Matsler, P. L. and H. D. Chapman. (2007). Selection for early (precocious) development of Eimeria meleagridis in the turkey. Avian Diseases 51: 122-124.
Chapman, H. D. and T. Rathinam. (2007). Sensitivity of field isolates of Eimeria to monensin in the turkey. Avian Diseases 51: 954-957.
Chapman, H. D. and P. L. Matsler. (2007). Characterization and attenuation of Eimeria meleagridis from the turkey (p. 25). In: Proceedings of the 56th Western Poultry Disease Conference, Las Vegas, NV.
Chapman, H. D. and Rathinam, T. (2007). Characterization and attenuation of Eimeria meleagridis from the turkey. In: Proceedings of the American Association of Veterinary Parasitologists (p. 64), Washington, DC. 4.
Chapman, H. D. (2007). Tendencias mundiales en el control de coccidiosis: tratamiento, medicamentos anticoccidianos y vacunas. In: Proceedings of the International Novartis Poultry Symposium (p. 101-104). Puerto Vallarta, MX.
Chapman, H. D. (2007). Future prospects for coccidiosis control in the turkey. In: Proceedings of the first Turkey Science and Production Conference, (p. 25-27), Macclesfield, UK.

Progress 01/01/06 to 12/31/06

Outputs
NON-TECHNICAL SUMMARY: Coccidiosis is a widespread disease of turkeys caused by protozoan parasites of the genus Eimeria that is controlled by the inclusion of anticoccidial drugs in the feed. Despite this the parasites are widespread and the cause of significant economic loss to the turkey industry. Seven species of Eimeria are recognized from the turkey but only four are considered pathogenic. Vaccination is possible using live organisms but immunity is species specific, it is necessary therefore to include all pathogenic species in commercial vaccines for successful control of coccidiosis. One species, Eimeria meleagridis, is common in turkey flocks, but its biology and pathogenicity is poorly described. This investigation demonstrated the importance of including this species in vaccines for the control of coccidiosis in the turkey. APPROACH: An isolate of E. meleagridis was obtained from northwest Arkansas, a pure line established in the laboratory, and its life cycle and pathogenicity investigated. Unlike other species that are restricted in development to one location in the intestine, this species was found to develop in epithelial cells of the lining of the small intestine and intestinal ceca. Four cycles of asexual multiplication were shown to occur in the host. No lesions were apparent in the intestine but infection resulted in a significant reduction in weight gain suggesting that the parasite interfered with the absorption of nutrients by the gut. PROGRESS: Progress has been made in understanding the life cycle of an Eimeria parasite that infects turkeys and its potential pathogenicity to this host. KEYWORDS: Coccidiosis, Eimeria, vaccines, parasite control, attenuation, immunity, turkey.

Impacts
IMPACT: Previous studies have suggested that E. meleagridis is not pathogenic to turkeys but the present findings indicate that this is not the case. Currently available vaccines for the control of coccidiosis in the turkey do not contain E. meleagridis and have had only limited success in the field. In view of the widespread incidence of this species in commercial turkey flocks, the inclusion of E. meleagridis in commercial vaccines may facilitate better control of coccidiosis in turkeys.

Publications

Chapman, H.D. (2006). Managing coccidiosis in turkeys. The 2006 Poultry Federation Symposium, 4 October 2006, Holiday Inn, Springdale AR.
Chapman, H. D., Roberts, B. Shirley, M. W. & Williams, R. B. (2006). Guidelines for the development and registration of anticoccidial vaccines for poultry. In: Proceedings of the Australian Poultry Science Symposium 18: 248-251.
Chapman, H.D. (2006). World tendencies in coccidiosis control: management, anticoccidial drugs, and vaccines. In: Proceedings of the Coccidiosis Symposium, September 8 2006, Puerto Vallarta, Mexico.
Chapman, H.D. (2006). Crossroads for coccidiosis control: anticoccidial drugs, and vaccines. In: Proceedings of the 4th Simposium Internacional de patologia aviar. October 27 2006, Cordoba, Mexico.
Chapman, H. D. (2006). Guidelines for coccidiosis vaccines (pages 14-19). In: Cocciforum, Number 12, Published by Schering-Plough Animal Health Corp.
Chapman, H. D. (2006). Safety and toxicity of polyether ionophores in poultry. In: FeatherData, An Update of recent poultry research (8 pages). Published by ALPharma Animal Health, Fort Lee, NJ.
Chapman, H. D. (2006). Guidelines for the development and registration of anticoccidial vaccines for poultry. Australian Poultry Science Symposium, February 20-22, 2006, Sydney, Australia.
Chapman, H.D. (2006). Characterisation of E. meleagridis from the turkey. European Coccidiosis Discussion Group, Weybridge, UK. May 24, 2006.
Chapman, H.D. (2006). World tendencies in coccidiosis control. Poultry Coccidiosis Symposium, September 8th, 2006, Puerto Vallarta, Mexico.
Chapman, H.D. (2006). Perspectives for the control of coccidiosis in broilers by chemotherapy and vaccination. 4th Simposium Internacional de Patologia Aviar. October 27th 2006, Cordoba, Mexico.