The Biology of Avian Eimeria with an Emphasis on their Control by Vaccination

Transgenic Eimeria mitis expressing chicken interleukin 2 stimulated higher cellular immune response in chickens compared with the wild-type parasites

Chicken coccidiosis, caused by Eimeria sp., occurs in almost all poultry farms and causes huge economic losses in the poultry industry. Although this disease could be controlled by vaccination, the reduced feed conservation ratio limits the widespread application of anticoccidial vaccines in broilers because some intermediate and/or low immunogenic Eimeria sp. only elicit partial protection. It is of importance to enhance the immunogenicity of these Eimeria sp. by adjuvants for more effective prevention of coccidiosis. Cytokines have remarkable effects on the immunogenicity of antigens. Interleukin 2 (IL-2), for example, significantly stimulates the activation of CD8+ T cells and other immune cells. In this study, we constructed a transgenic Eimeria mitis line (EmiChIL-2) expressing chicken IL-2 (ChIL-2) to investigate the adjuvant effect of ChIL-2 to enhance the immunogenicity of E. mitis against its infection. Stable transfected EmiChIL-2 population was obtained by pyrimethamine selection and verified by PCR, genome walking, western blotting and indirect immunofluorescence assay. Cellular immune response, E. mitis-specific IFN-γ secretion lymphocytes in the peripheral blood mononuclear cells, stimulated by EmiChIL-2 was analyzed by enzyme-linked immunospot assay (ELISPOT). The results showed that EmiChIL-2 stimulated a higher cellular immune response compared with that of the wild-type parasite infection in chickens. Moreover, after the immunization with EmiChIL-2, elevated cellular immune response as well as reduced oocyst output were observed These results indicated that ChIL-2 expressed by Eimeria sp. functions as adjuvant and IL-2 expressing Eimeria parasites are valuable vaccine strains against coccidiosis.

Induction of protective immunity against Eimeria tenella, Eimeria necatrix, Eimeria maxima and Eimeria acervulina infections using multivalent epitope DNA vaccines

Avian coccidiosis is mostly caused by mixed infection of several Eimeria species under natural conditions and immunity to avian coccidiosis is largely dependent on T-cell immune response. In this study, 14 T-cell epitope fragments from eight antigens of Eimeria tenella (E. tenella), Eimeria necatrix (E. necatrix), Eimeria maxima (E. maxima) and Eimeria acervulina (E. acervulina) were ligated with pVAX1 producing 14 monovalent DNA vaccines, respectively. Protective immunity of the monovalent DNA vaccines was assessed by in vivo challenge experiments and then four most protective fragments of each species were chosen to construct multivalent epitope DNA vaccines with or without chicken IL-2 as genetic adjuvant. Protective efficacies of the epitope DNA vaccines on chickens against E. tenella, E. necatrix, E. maxima and E. acervulina were evaluated. The results showed that the constructed multivalent epitope DNA vaccines significantly increased body weight gain, alleviated enteric lesions and reduced oocyst output of the infected birds. Especially, the multivalent epitope DNA vaccines of pVAX1-NA4-1-TA4-1-LDH-2-EMCDPK-1 and pVAX1-NA4-1-TA4-1-LDH-2-EMCDPK-1-IL-2 not only significantly increased body weight gain, alleviated enteric lesions and reduced oocyst output of the infected birds, but also resulted in anti-coccidial index (ACI) more than 170 against E. tenella, E. necatrix, E. maxima and E. acervulina, which indicated they could induce protective immunity against E. tenella, E. necatrix, E. maxima and E. acervulina. Our findings suggest the constructed multivalent epitope DNA vaccines are the potential candidate multivalent vaccines against mixed infection of Eimeria.

Prevalence of poultry coccidiosis in Jammu region of Jammu & Kashmir State

In this study prevalence of chicken coccidiosis in Jammu division were undertaken in both organized and backyard chickens during the year 2010-2011, with an overall prevalence of 39.58 % on examination of 720 faecal samples. Five Eimeria species were identified viz., E. tenella, E. necatrix, E. maxima, E. acervulina and E. mitis. E. tenella was the predominant species in both organized and unorganized farms. The highest prevalence percentage was found in July, 2011 (68.9 %) and the lowest percentage was found in May, 2011 (12.5 %). Coccidial prevalence was found to be 53.61 % in unorganized (backyard poultry birds) as compared to organized birds (25.55 %). Maximum positive cases of coccidian infection was found in monsoon season (60.55 %) and least in summer season (21.66 %). Birds of age 31-45 days showed more prevalence percentage (58.86 %). Higher oocysts count was recorded from July to September with a peak value (38973.00 ± 3075.6) in July and lowest (12914.00 ± 595.48) in the month of May.

Loop-mediated isothermal amplification (LAMP) assays for the species-specific detection of Eimeria that infect chickens

Eimeria species parasites, protozoa which cause the enteric disease coccidiosis, pose a serious threat to the production and welfare of chickens. In the absence of effective control clinical coccidiosis can be devastating. Resistance to the chemoprophylactics frequently used to control Eimeria is common and sub-clinical infection is widespread, influencing feed conversion ratios and susceptibility to other pathogens such as Clostridium perfringens. Despite the availability of polymerase chain reaction (PCR)-based tools, diagnosis of Eimeria infection still relies almost entirely on traditional approaches such as lesion scoring and oocyst morphology, but neither is straightforward. Limitations of the existing molecular tools include the requirement for specialist equipment and difficulties accessing DNA as template. In response a simple field DNA preparation protocol and a panel of species-specific loop-mediated isothermal amplification (LAMP) assays have been developed for the seven Eimeria recognised to infect the chicken. We now provide a detailed protocol describing the preparation of genomic DNA from intestinal tissue collected post-mortem, followed by setup and readout of the LAMP assays. Eimeria species-specific LAMP can be used to monitor parasite occurrence, assessing the efficacy of a farm's anticoccidial strategy, and to diagnose sub-clinical infection or clinical disease with particular value when expert surveillance is unavailable.

Anti-Eimeria activity of berberine and identification of associated gene expression changes in the mouse jejunum infected with Eimeria papillata

Plant-based natural products are promising sources for identifying novel agents with potential anti-Eimeria activity. This study explores possible effects of berberine on Eimeria papillata infections in the jejunum of male Swiss albino mice. Berberine chloride, when daily administered to mice during infection, impairs intracellular development and multiplication of E. papillata, evidenced as 60% reduction of maximal fecal output of oocysts on day 5 p.i. Concomitantly, berberine attenuates the inflammatory response, evidenced as decreased messenger RNA (mRNA) expression of IL-1β, IL-6, TNFα, IFNγ, and iNOS, as well as the oxidative stress response, evidenced as impaired increase in malondialdehyde, nitrate, and H2O2 and as prevented decrease in glutathione and catalase activity. Berberine also alters gene expression in the infected jejunum. On day 5 p.i., mRNA expression of 29 genes with annotated functions is more than 10-fold upregulated and that of 14 genes downregulated. Berberine downregulates the genes Xaf1, Itgb3bp, and Faim3 involved in apoptotic processes and upregulates genes involved in innate immune responses, as e.g., Colec11, Saa2, Klra8, Clec1b, and Crtam, especially the genes Cpa3, Fcer1a, and Mcpt1, Mcpt2, and Mcpt4 involved in mast cell activity. Additionally, 18 noncoding lincRNA species are differentially expressed more than 10-fold under berberine. Our data suggest that berberine induces hosts to exert anti-Eimeria activity by attenuating the inflammatory and oxidative stress response, by impairing apoptotic processes, and by activating local innate immune responses and epigenetic mechanisms in the host jejunum. Berberine has the potential as an anti-Eimeria food additive in animal farming.

Protective immunity against Eimeria tenella infection in chickens induced by immunization with a recombinant C-terminal derivative of EtIMP1

Immune mapped protein-1 (IMP1) is a new protective protein in apicomplexan parasites, and exits in Eimeria tenella. Cloning and sequence analysis has predicted the antigen to be a novel membrane protein of apicomplexan parasites. In order to assess the immunogenicity of EtIMP1, a C-terminal derivative of EtIMP1 was expressed in a bacterial host system and was used to immunize chickens. The protective efficacy against a homologous challenge was evaluated by body weight gains, lesion scores and fecal oocyst shedding. The results showed that the subunit vaccine can improve weight gains, reduced cecal pathology and lower oocyst fecal shedding compared with non immunized controls. The results suggested that the C-terminal derivative of EtIMP1 might be considered as a candidate in the development of subunit vaccines against Eimeria infection.

Towards identifying novel anti-Eimeria agents: trace elements, vitamins, and plant-based natural products

Eimeriosis, a widespread infectious disease of livestock, is caused by coccidian protozoans of the genus Eimeria. These obligate intracellular parasites strike the digestive tract of their hosts and give rise to enormous economic losses, particularly in poultry, ruminants including cattle, and rabbit farming. Vaccination, though a rational prophylactic measure, has not yet been as successful as initially thought. Numerous broad-spectrum anti-coccidial drugs are currently in use for treatment and prophylactic control of eimeriosis. However, increasing concerns about parasite resistance, consumer health, and environmental safety of the commercial drugs warrant efforts to search for novel agents with anti-Eimeria activity. This review summarizes current approaches to prevent and treat eimeriosis such as vaccination and commercial drugs, as well as recent attempts to use dietary antioxidants as novel anti-Eimeria agents. In particular, the trace elements selenium and zinc, the vitamins A and E, and natural products extracted from garlic, barberry, pomegranate, sweet wormwood, and other plants are discussed. Several of these novel anti-Eimeria agents exhibit a protective role against oxidative stress that occurs not only in the intestine of Eimeria-infected animals, but also in their non-parasitized tissues, in particular, in the first-pass organ liver. Currently, it appears to be promising to identify safe combinations of low-cost natural products with high anti-Eimeria efficacy for a potential use as feed supplementation in animal farming.

Genomic analysis of the causative agents of coccidiosis in domestic chickens

Global production of chickens has trebled in the past two decades and they are now the most important source of dietary animal protein worldwide. Chickens are subject to many infectious diseases that reduce their performance and productivity. Coccidiosis, caused by apicomplexan protozoa of the genus Eimeria, is one of the most important poultry diseases. Understanding the biology of Eimeria parasites underpins development of new drugs and vaccines needed to improve global food security. We have produced annotated genome sequences of all seven species of Eimeria that infect domestic chickens, which reveal the full extent of previously described repeat-rich and repeat-poor regions and show that these parasites possess the most repeat-rich proteomes ever described. Furthermore, while no other apicomplexan has been found to possess retrotransposons, Eimeria is home to a family of chromoviruses. Analysis of Eimeria genes involved in basic biology and host-parasite interaction highlights adaptations to a relatively simple developmental life cycle and a complex array of co-expressed surface proteins involved in host cell binding.

Pichia pastoris expressed EtMic2 protein as a potential vaccine against chicken coccidiosis

Chicken coccidiosis caused by Eimeria species leads to tremendous economic losses to the avian industry worldwide. Identification of parasite life cycle specific antigens is a critical step in recombinant protein vaccine development against Eimeria infections. In the present study, we amplified and cloned the microneme-2 (EtMIC2) gene from Eimeria tenella wild type strain SD-01, and expressed the EtMic2 protein using Pichia pastoris and Escherichia coli expression systems, respectively. The EtMic2 proteins expressed by P. pastoris and E. coli were used as vaccines to immunize chickens and their protective efficacies were compared and evaluated. The results indicated that both P. pastoris and E. coli expressed EtMic2 proteins exhibited good immunogenicity in stimulating host immune responses and the Pichia expressed EtMic2 provided better protection than the E. coli expressed EtMic2 did by significantly increasing growth rate, inducing high specific antibody response, reducing the oocyst output and cecal lesions. Particularly, the Pichia expressed EtMic2 protein exhibited much better ability in inducing cell mediated immune response than the E. coli expressed EtMic2.

Molecular characterization and analysis of a novel protein disulfide isomerase-like protein of Eimeria tenella

Protein disulfide isomerase (PDI) and PDI-like proteins are members of the thioredoxin superfamily. They contain thioredoxin-like domains and catalyze the physiological oxidation, reduction and isomerization of protein disulfide bonds, which are involved in cell function and development in prokaryotes and eukaryotes. In this study, EtPDIL, a novel PDI-like gene of Eimeria tenella, was cloned using rapid amplification of cDNA ends (RACE) according to the expressed sequence tag (EST). The EtPDIL cDNA contained 1129 nucleotides encoding 216 amino acids. The deduced EtPDIL protein belonged to thioredoxin-like superfamily and had a single predicted thioredoxin domain with a non-classical thioredoxin-like motif (SXXC). BLAST analysis showed that the EtPDIL protein was 55–59% identical to PDI-like proteins of other apicomplexan parasites. The transcript and protein levels of EtPDIL at different development stages were investigated by real-time quantitative PCR and western blot. The messenger RNA and protein levels of EtPDIL were higher in sporulated oocysts than in unsporulated oocysts, sporozoites or merozoites. Protein expression was barely detectable in unsporulated oocysts. Western blots showed that rabbit antiserum against recombinant EtPDIL recognized only a native 24 kDa protein from parasites. Immunolocalization with EtPDIL antibody showed that EtPDIL had a disperse distribution in the cytoplasm of whole sporozoites and merozoites. After sporozoites were incubated in complete medium, EtPDIL protein concentrated at the anterior of the sporozoites and appeared on the surface of parasites. Specific staining was more intense and mainly located on the parasite surface after merozoites released from mature schizonts invaded DF-1 cells. After development of parasites in DF-1 cells, staining intensified in trophozoites, immature schizonts and mature schizonts. Antibody inhibition of EtPDIL function reduced the ability of E. tenella to invade DF-1 cells. These results suggested that EtPDIL might be involved in sporulation in external environments and in host cell adhesion, invasion and development of E. tenella.

Co-expression of EtMic2 protein and chicken interleukin-18 for DNA vaccine against chicken coccidiosis

In the present study, a naked EtMIC2 DNA vaccine, a ChIL-18 expression vector and a EtMIC2 and ChIL-18 co-expression DNA vaccine were constructed and their protective efficacies against homologous challenge were compared and evaluated by examining the body weight gain, oocyst shedding, cecal lesion, ACI as well as specific anti-EtMic2 antibody level, the proliferation ability and percentages of CD4+ and CD8+ of splenocytes. The results showed the naked EtMIC2 DNA vaccine could increase the weight gain and decrease the oocyst shedding, but could not alleviate the cecal lesion of immunized chickens compared to unimmunized chickens. Chickens immunized with the co-expression vector pVAX1-MIC2-IL-18 exhibited much improved immune protection against challenge compared to chickens immunized with naked EtMIC2 DNA vaccine, or with naked EtMIC2 DNA vaccine and ChIL-18 expression vector applied separately. These results suggest that the co-expression of ChIL-18 with EtMic2 together could significantly improve the immune protection of the EtMic2 protein.

In vivo anticoccidial activity of berberine [18, 5,6-dihydro-9,10-dimethoxybenzo(g)-1,3-benzodioxolo(5,6-a) quinolizinium]--an isoquinoline alkaloid present in the root bark of Berberis lycium

Coccidiosis, caused by various Eimeria species, is a major parasitic disease in chicken. However the increasing resistance of these parasites to currently used anticoccidial drugs has stimulated the search for new methods of control. As part of this effort we investigated the root bark of Berberis lycium (barberry) as a potential source of compounds with anticoccidial activity. In the present study anticoccidial activity of different solvent extracts of the root bark of B. lycium and berberine was evaluated in vivo using broiler chicken. Results of the study demonstrated equipotent efficacy of pure berberine in comparison to that of standard drug amprolium on the basis of reduction in coccidian oocyst output, body weight gain of chicken and feed conversion ratio. Among the extracts crude methanolic extract showed highest anticoccidial activity tested at 300 mg/kg body weight which could be due to the presence of alcohol-soluble active ingredients in root bark of B. lycium. Toxicological studies revealed that B. lycium extracts as well as berberine were not lethal up to dosage of 2000 mg/kg body weight. LD(50) was not determined as mortalities were not recorded in any of the five groups of chicken. From the present study it can be concluded that root bark of B. lycium has the immense potential to contribute to the control of coccidian parasites of chicken. Our results corroborate the use of berberine for treatment of severe diarrhoea, amoebiasis and intestinal infections and could justify its use in folk medicine for treatment of haemorrhagic dysentery.

Seasonal impact on the prevalence of coccidian infection in broiler chicks across poultry farms in the Kashmir valley

The information on the epidemiology and control of coccidian parasites of broilers in Kashmir valley is based on the reports available from other regions of the world. With this background, the present study was conducted to investigate the seasonal prevalence of the disease in the temperate agro-climatic conditions of Kashmir valley. A standard protocol for sampling was followed according to which five birds per 10,000 is sufficient to diagnose coccidiosis. Microscopic examination (under 10× and 40× objective lens) was used to reveal the presence of coccidial oocysts. Different species of genus Eimeria were identified on the basis of their predilection site, morphology and size. Coccidiosis was most prevalent in autumn 45.12 ± 2.55 (September 47.5 %, October 42.42 % and November 45.46 %) followed by summer 30.84 ± 6.86, spring 23.81 ± 2.81 and winter 20.29 ± 6.40. In summer, prevalence of disease was low but afterwards prevalence of disease rose up from August to October. In spite of high relative humidity in winter, disease showed low prevalence rate. Over all prevalence for the whole year was 29.87 %. Among species Eimeria tenella was the most dominant parasite showing highest prevalence of 18.13 %. Variation in incidence of coccidiosis with respect to seasons showed a strong correlation and data was found to be statistically significant with P < 0.05. The results obtained would be quite useful to devise appropriate and effective control strategies and prophylactic programs for coccidiosis in poultry unique to this climatic zone and other parts of the world with similar climatic and poultry production systems.

A selective review of advances in coccidiosis research

Coccidiosis is a widespread and economically significant disease of livestock caused by protozoan parasites of the genus Eimeria. This disease is worldwide in occurrence and costs the animal agricultural industry many millions of dollars to control. In recent years, the modern tools of molecular biology, biochemistry, cell biology and immunology have been used to expand greatly our knowledge of these parasites and the disease they cause. Such studies are essential if we are to develop new means for the control of coccidiosis. In this chapter, selective aspects of the biology of these organisms, with emphasis on recent research in poultry, are reviewed. Topics considered include taxonomy, systematics, genetics, genomics, transcriptomics, proteomics, transfection, oocyst biogenesis, host cell invasion, immunobiology, diagnostics and control.

Occurrence of Eimeria species parasites on small-scale commercial chicken farms in Africa and indication of economic profitability

Small-scale commercial poultry production is emerging as an important form of livestock production in Africa, providing sources of income and animal protein to many poor households, yet the occurrence and impact of coccidiosis on this relatively new production system remains unknown. The primary objective of this study was to examine Eimeria parasite occurrence on small-scale commercial poultry farms in Ghana, Tanzania and Zambia. Additionally, farm economic viability was measured by calculating the farm gross margin and enterprise budget. Using these economic measures as global assessments of farm productivity, encompassing the diversity present in regional husbandry systems with a measure of fundamental local relevance, we investigated the detection of specific Eimeria species as indicators of farm profitability. Faecal samples and data on production parameters were collected from small-scale (less than 2,000 birds per batch) intensive broiler and layer farms in peri-urban Ghana, Tanzania and Zambia. All seven Eimeria species recognised to infect the chicken were detected in each country. Furthermore, two of the three genetic variants (operational taxonomic units) identified previously in Australia have been described outside of Australia for the first time. Detection of the most pathogenic Eimeria species associated with decreased farm profitability and may be considered as an indicator of likely farm performance. While a causal link remains to be demonstrated, the presence of highly pathogenic enteric parasites may pose a threat to profitable, sustainable small-scale poultry enterprises in Africa.

Protecting chickens against coccidiosis in floor pens by administering Eimeria oocysts using gel beads or spray vaccination

Control of avian coccidiosis is increasingly being achieved by the administration of low doses of Eimeria oocysts to newly hatched chicks. The purpose of this study was to test the efficacy of gel beads containing a mixture of Eimeria acervulina, Eimeria maxima, and Eimeria tenella oocysts as a vaccine to protect broilers raised in contact with litter. Newly hatched chicks were either sprayed with an aqueous suspension of Eimeria oocysts or were allowed to ingest feed containing Eimeria oocysts-incorporated gel beads. Control, 1-day-old chicks were given an equivalent number of Eimeria oocysts (10(3) total) by oral gavage or received no vaccine (nonimmunized controls). All chicks were raised in floor-pen cages in direct contact with litter. At 4 wk of age, all chickens and a control nonimmunized group received a high-dose E. acervulina, E. maxima, and E. tenella challenge infection. Chickens immunized with Eimeria oocysts in gel beads or by spray vaccination displayed significantly (P < 0.05) greater weight gain (WG) compared to nonimmunized controls. Feed conversion ratio (FCR) also showed a significant (P < 0.05) improvement in both groups relative to nonimmunized controls. Moreover, WG and FCR in both groups was not significantly different (P > 0.05) from chickens immunized by oral gavage or from nonimmunized, noninfected controls. Oocyst excretion after Eimeria challenge by all immunized groups was about 10-fold less than in nonimmunized controls. These findings indicate that immunization efficacy of gel beads and spray vaccination is improved by raising immunized chicks in contact with litter.

The effects of combiningArtemisia annuaandCurcuma longaethanolic extracts in broilers challenged with infective oocysts ofEimeria acervulinaandE. maxima

Due to an increasing demand for natural products to control coccidiosis in broilers, we investigated the effects of supplementing a combination of ethanolic extracts ofArtemisia annuaandCurcuma longain drinking water. Three different dosages of this herbal mixture were compared with a negative control (uninfected), a positive control (infected and untreated), chemical coccidiostats (nicarbazin+narazin and, later, salinomycin), vaccination, and a product based on oregano. Differences in performance (weight gain, feed intake, and feed conversion rate), mortality, gross intestinal lesions and oocyst excretion were investigated. Broilers given chemical coccidiostats performed better than all other groups. Broilers given the two highest dosages of the herbal mixture had intermediate lesion scores caused byEimeria acervulina, which was higher than in broilers given coccidiostats, but less than in broilers given vaccination, oregano and in negative controls. There was a trend for lower mortality (P= 0·08) in the later stage of the growing period (23–43 days) in broilers given the highest dosage of herbal mixture compared with broilers given chemical coccidiostats. In conclusion, the delivery strategy of the herbal extracts is easy to implement at farm level, but further studies on dose levels and modes of action are needed.

An optimised protocol for molecular identification of Eimeria from chickens

Molecular approaches supporting identification of Eimeria parasites infecting chickens have been available for more than 20 years, although they have largely failed to replace traditional measures such as microscopy and pathology. Limitations of microscopy-led diagnostics, including a requirement for specialist parasitological expertise and low sample throughput, are yet to be outweighed by the difficulties associated with accessing genomic DNA from environmental Eimeria samples. A key step towards the use of Eimeria species-specific PCR as a sensitive and reproducible discriminatory tool for use in the field is the production of a standardised protocol that includes sample collection and DNA template preparation, as well as primer selection from the numerous PCR assays now published. Such a protocol will facilitate development of valuable epidemiological datasets which may be easily compared between studies and laboratories. The outcome of an optimisation process undertaken in laboratories in India and the UK is described here, identifying four steps. First, samples were collected into a 2% (w/v) potassium dichromate solution. Second, oocysts were enriched by flotation in saturated saline. Third, genomic DNA was extracted using a QIAamp DNA Stool mini kit protocol including a mechanical homogenisation step. Finally, nested PCR was carried out using previously published primers targeting the internal transcribed spacer region 1 (ITS-1). Alternative methods tested included sample processing in the presence of faecal material, DNA extraction using a traditional phenol/chloroform protocol, the use of SCAR multiplex PCR (one tube and two tube versions) and speciation using the morphometric tool COCCIMORPH for the first time with field samples.

An Eimeria vaccine candidate based on Eimeria tenella immune mapped protein 1 and the TLR-5 agonist Salmonella typhimurium FliC flagellin

Immune mapped protein-1 (IMP1) is a new protective protein in apicomplexan parasites, and exits in Eimeria tenella. But its structure and immunogenicity in E. tenella are still unknown. In this study, IMPI in E. tenella was predicted to be a membrane protein. To evaluate immunogenicity of IMPI in E. tenella, a chimeric subunit vaccine consisting of E. tenella IMP1 (EtIMP1) and a molecular adjuvant (a truncated flagellin, FliC) was constructed and over-expressed in Escherichia coli and its efficacy against E. tenella infection was evaluated. Three-week-old AA broiler chickens were vaccinated with the recombinant EtIMP1-truncated FliC without adjuvant or EtIMP1 with Freund's Complete Adjuvant. Immunization of chickens with the recombinant EtIMP1-truncated FliC fusion protein resulted in stronger cellular immune responses than immunization with only recombinant EtIMP1 with adjuvant. The clinical effect of the EtIMP1-truncated FliC without adjuvant was also greater than that of the EtIMP1 with adjuvant, which was evidenced by the differences between the two groups in body weight gain, oocyst output and caecal lesions of E. tenella-challenged chickens. The results suggested that the EtIMP1-flagellin fusion protein can be used as an effective immunogen in the development of subunit vaccines against Eimeria infection. This is the first demonstration of antigen-specific protective immunity against avian coccidiosis using a recombinant flagellin as an apicomplexan parasite vaccine adjuvant in chickens.

Protective effects of oral immunization with live Lactococcus lactis expressing Eimeria tenella 3-1E protein

The codon-optimized Eimeria tenella 3-1E gene was introduced into the lactic acid bacterial vector pTX8048 to construct plasmid pTX8048-3-1E. The plasmid pTX8048-3-1E was transformed into Lactococcus lactis NZ9000 by electroporation to create the strain of L. lactis pTX8048-3-1E. The expression of objective protein was verified by Western blot. The live bacteria L. lactis pTX8048-3-1E were administered orally, and an animal challenge experiment was carried out to evaluate the protective efficacy. The results indicated the strain of L. lactis pTX8048-3-1E was constructed successfully. Oral immunization to specific pathogen-free (SPF) chickens with L. lactis pTX8048-3-1E provided partial protection against homologous challenge including significant increased oocyst decrease ratio, reduced average lesion score in cecum, and improved body weight gain compared to control bacteria L. lactis pTX8048. These results demonstrate the use of Lactococcus as live vector for delivery of Eimeria antigen is feasible and promising method to control coccidiosis in poultry.

Characterization of Eimeria brunetti Isolated from a Poultry Farm in Japan

None of anticoccidial vaccines (Trivalent TAM™, monovalent Neca™ and imported pentavalent Paracox(®)-5) contain Eimeria brunetti in Japan, which has not been regarded as a cause of coccidiosis, because of its low prevalence. However, we have recently reported the evidence of a high nationwide prevalence of this species. In this report, we describe the characteristics of E. brunetti which have never been clearly defined in Japan. Mortality rates and other disease characteristics caused by our strain (Nb strain) were similar to those reported previously in other studies. Despite great reduction of body weight gains among groups infected with over 1 × 10(3) oocysts, the intestinal lesions in the infected chickens were rather mild compared to previous studies. Sulfa drugs and lasalocid were so effective that the E. brunetti infection was almost completely blocked. Consequently, it is suggested that the characteristics of E. brunetti are various among the strains, but the pathogenicity of the Japanese Nb strain is enough strong to cause clinical coccidiosis.

Interferon-γ enzyme-linked immunosorbent spot assay as a tool to study T cell responses to Eimeria tenella infection in chickens

The enzyme-linked immunosorbent spot (ELISPOT) assay is a sensitive and easy-to-use tool to quantify the number of interferon (IFN)-γ-producing cells and offers a viable alternative for the quantitative measurement of T cell functions in chickens. To study the development of cell-mediated immunity in Eimeria-infected chickens, we measured the number of IFN-γ-producing cells in peripheral blood mononuclear cells by ELISPOT after 3 oral inoculations of Eimeria tenella oocysts at 2-wk intervals. We found that the number of IFN-γ-producing cells was significantly increased at 2 wk after the primary infection compared with the control group. The IFN-γ-producing cells were further increased after repeated infections, and there was a statistically significant increase in the number of IFN-γ-producing cells after the third infection than after the first infection. Our results indicated that the ELISPOT assay can be used to quantitatively measure antigen-specific T cell responses to coccidia or other avian pathogens.

Induced metabolic disturbance and growth depression in rabbits infected with Eimeria coecicola

Eimeria coecicola causes intestinal coccidiosis in rabbits and, thereby, enormous economic losses in rabbit farms. This study aimed to investigate the effect of intestinal coccidial infection, E. coecicola on metabolic status and growth of rabbits. Animals were allocated into two groups with eight rabbits each; one group was orally inoculated with saline and served as control while the other group was orally inoculated with 5 × 10(4) sporulated oocysts. On day 7 postinfection, fecal expulsion of E. coecicola oocysts is maximal (1.2 × 10(6) oocyst/g feces) and rabbits have lost approximately 23% of their weight. Infection induced a severe depletion in plasma growth hormone level. In addition, the energy metabolic status was significantly (P ≤ 0.05) altered by the infection as, both blood glucose and total lipid levels were significantly elevated with mutual depletion in carbohydrate stores in liver sections. Also, the thyroid-stimulating hormone and cortisol concentrations were raised as a consequence of the infection. Moreover, protein status was affected by the infection as both liver and plasma total proteins were significantly decreased with concurrent disturbance in the blood protein electrophoretic pattern and duplication of blood urea nitrogen concentration. Finally, the infection induced plasma electrolyte imbalance as indicated by a significant decrease in sodium, potassium, calcium, phosphorus, ferrous, and selenium ions. Our data suggested that the intestinal coccidial infection of rabbits with E. coecicola has serious effects on rabbit growth and metabolism and could disrupt endocrine and electrolyte homeostasis.

Transcriptome analysis in chicken cecal epithelia upon infection by Eimeria tenella in vivo

Coccidiosis, caused by various Eimeria species, is a major parasitic disease in chickens. However, our understanding on how chickens respond to coccidian infection is highly limited at both molecular and cellular levels. The present study employed the Affymetrix chicken genome array and performed transcriptome analysis on chicken cecal epithelia in response to infection for 4.5 days in vivo by the cecal-specific species E. tenella. By Significance Analysis of Microarrays (SAM), we have identified 7,099 probe sets with q-values at <0.05, in which 4,033 and 3,066 genes were found to be up- or down-regulated in response to parasite infection. The reliability of the microarray data were validated by real-time qRT-PCR of 20 genes with varied fold changes in expression (i.e., correlation coefficient between microarray and qRT-PCR datasets: R (2) = 0.8773, p<0.0001). Gene ontology analysis, KEGG pathway mapping and manual annotations of regulated genes indicated that up-regulated genes were mainly involved in immunity/defense, responses to various stimuli, apoptosis/cell death and differentiation, signal transduction and extracellular matrix (ECM), whereas down-regulated genes were mainly encoding general metabolic enzymes, membrane components, and some transporters. Chickens mustered complex cecal eipthelia molecular and immunological responses in response to E. tenella infection, which included pathways involved in cytokine production and interactions, natural killer cell mediated cytotoxicity, and intestinal IgA production. In response to the pathogenesis and damage caused by infection, chicken cecal epithelia reduced general metabolism, DNA replication and repair, protein degradation, and mitochondrial functions.

Differing susceptibilities of Eimeria acervulina, Eimeria maxima, and Eimeria tenella oocysts to desiccation

Outbreaks of avian coccidiosis may occur when susceptible chickens are raised on litter containing viable Eimeria oocysts. The purpose of this study was to compare the relative sensitivities of Eimeria acervulina, Eimeria maxima, and Eimeria tenella oocysts to dessication. Sporulated E. acervulina, E. maxima, or E. tenella oocysts were incorporated into gelatin beads and incubated at 32 C for 0, 1, 2, or 3 days. In vitro oocyst excystation rates were measured for each combination of Eimeria species and incubation time. Day-old broiler chicks were allowed to ingest the oocysts-containing beads, and total oocyst production was measured from days 5-8 post-inoculation. Although no effect on excystation was observed, E. maxima oocysts displayed greater resistance to drying compared to E. acervulina and E. tenella oocysts. Eimeria acervulina oocyst production decreased 100-fold after 1-2 days incubation. Eimeria tenella oocysts were slightly more resistant to drying in that a 100-fold decrease in oocyst production was delayed until 2 days. For both E. acervulina and E. tenella , very few oocysts were observed after 3 days incubation. Eimeria maxima oocyst production remained high at all time points. Subsequent studies revealed E. maxima oocyst production was ablated only after 5 days incubation. These findings may explain in part the observed prevalence of E. maxima in litter from commercial poultry operations.

Partial protective of chickens against Eimeria tenella challenge with recombinant EtMIC-1 antigen

Eimeria tenella microneme protein 1 (EtMIC-1) is highly conserved with TgMIC-2, which is involved in parasite binding specifically to host cells. Little is known about the immune responses and protective efficacy against E. tenella infection with EtMIC-1 antigen. In the present study, the recombinant proteins of E. tenella mature MIC-1 and adhesive domain (von Willebrand factor type A domain, EtMIC-1-VD) were obtained, protective efficacy against E.tenella infection and the mucosal immune response, which is induced in broilers was evaluated. The antibody levels and the transcription profiles of cytokine of chickens, such as interleukin-12 (IL-12) and interferon-γ (IFN-γ), were detected after being immunized three times with the recombinant EtMIC-1 and EtMIC-1-VD by ELISA assay and quantitative real-time PCR, respectively. The results showed that both groups of chickens, after being immunized with 100 μg EtMIC-1 or EtMIC-1-VD antigen, induced about tenfold higher IgG levels compared to the nonimmune groups. The transcription profiles of IL-12 and IFN-γ of the immunized groups were significantly higher than the control groups as well. The anticoccidial index of the group immunized with 100 μg EtMIC-1 and the group immunized with 100 μg EtMIC-1-VD were 167.2 and 165.5, respectively, which are significantly higher than low-dose immunized groups and challenged control groups. Our data suggests that VD domain is the key functional structure of EtMIC-1 that could trigger a significant humoral and cellular response against E. tenella infection, and EtMIC-1 had the potential in imparting partial protection in chickens against homologous challenge.

Genetic mapping and coccidial parasites: past achievements and future prospects

Coccidial parasites including Cryptosporidium parvum, Cyclospora cayetanensis, Neospora caninum, Toxoplasma gondii and the Eimeria species can cause severe disease of medical and veterinary importance. As many as one-third of the human population may carry T. gondii infection, and Eimeria are thought to cost the global poultry production industry in excess of US$2 billion per annum. Despite their significance, effective vaccines are scarce and have been confined to the veterinary field. As sequencing and genotyping technologies continue to develop, genetic mapping remains a valuable tool for the identification of genes that underlie phenotypic traits of interest and the assembly of contiguous genome sequences. For the coccidian, cross-fertilization still requires in vivo infection, a feature of their life cycle which limits the use of genetic mapping strategies. Importantly, the development of population-based approaches has now removed the need to isolate clonal lines for genetic mapping of selectable traits, complementing the classical clone-based techniques. To date, four coccidial species, representing three genera, have been investigated using genetic mapping. In this review we will discuss recent progress with these species and examine the prospects for future initiatives.

Edible vaccines against veterinary parasitic diseases--current status and future prospects

Protection of domestic animals against parasitic infections remains a major challenge in most of the developing countries, especially in the surge of drug resistant strains. In this circumstance vaccination seems to be the sole practical strategy to combat parasites. Most of the presently available live or killed parasitic vaccines possess many disadvantages. Thus, expression of parasitic antigens has seen a continued interest over the past few decades. However, only a limited success was achieved using bacterial, yeast, insect and mammalian expression systems. This is witnessed by an increasing number of reports on transgenic plant expression of previously reported and new antigens. Oral delivery of plant-made vaccines is particularly attractive due to their exceptional advantages. Moreover, the regulatory burden for veterinary vaccines is less compared to human vaccines. This led to an incredible investment in the field of transgenic plant vaccines for veterinary purpose. Plant based vaccine trials have been conducted to combat various significant parasitic diseases such as fasciolosis, schistosomosis, poultry coccidiosis, porcine cycticercosis and ascariosis. Besides, passive immunization by oral delivery of antibodies expressed in transgenic plants against poultry coccidiosis is an innovative strategy. These trials may pave way to the development of promising edible veterinary vaccines in the near future. As the existing data regarding edible parasitic vaccines are scattered, an attempt has been made to assemble the available literature.

Macrophage migration inhibitory factor (MIF) of the protozoan parasite Eimeria influences the components of the immune system of its host, the chicken

Macrophage migration inhibitory factor (MIF) is a soluble factor produced by sensitized T lymphocytes that inhibits the random migration of macrophages. Homologues of MIF from invertebrates have been identified, making it an interesting molecule from a functional perspective. In the present study, the localization of a parasite MIF protein as well as its effect on the host was characterized. Western blot analysis shows that Eimeria MIF (EMIF) is found during all parasite developmental stages tested. Transmission electron microscopy shows that MIF is distributed throughout cytosol and nucleus of Eimeria acervulina merozoites. Immunohistochemical analysis suggests that EMIF may be released into the surrounding tissues as early as 24 h after infection, while later during oocyst formation, MIF expression is localized to areas immediately surrounding the oocysts, as well as in wall-forming bodies. The chemotaxis assay revealed an inhibitory function of EMIF on chicken monocyte migration. Quantitative real-time PCR was performed to examine the effect of EMIF on host immune system by measuring the transcripts of inflammatory mediators. An ex vivo stimulation study showed that E. acervulina MIF (EaMIF) enhanced expression of pro-inflammatory cytokines and chemokines in the presence of lipopolysaccharide (LPS). Furthermore, sequential treatment of adherent peripheral blood mononuclear cells with EaMIF, chicken MIF, and LPS in 2-h intervals led to the highest levels of interleukin (IL)-1B, chemokine CCLi3, IL-18, and interferon-gamma mRNA expression. This study shows that parasite MIF is widely expressed and may have potential effects on the immune system of the host.

The Eimeria transcript DB: an integrated resource for annotated transcripts of protozoan parasites of the genus Eimeria

Parasites of the genus Eimeria infect a wide range of vertebrate hosts, including chickens. We have recently reported a comparative analysis of the transcriptomes of Eimeria acervulina, Eimeria maxima and Eimeria tenella, integrating ORESTES data produced by our group and publicly available Expressed Sequence Tags (ESTs). All cDNA reads have been assembled, and the reconstructed transcripts have been submitted to a comprehensive functional annotation pipeline. Additional studies included orthology assignment across apicomplexan parasites and clustering analyses of gene expression profiles among different developmental stages of the parasites. To make all this body of information publicly available, we constructed the Eimeria Transcript Database (EimeriaTDB), a web repository that provides access to sequence data, annotation and comparative analyses. Here, we describe the web interface, available sequence data sets and query tools implemented on the site. The main goal of this work is to offer a public repository of sequence and functional annotation data of reconstructed transcripts of parasites of the genus Eimeria. We believe that EimeriaTDB will represent a valuable and complementary resource for the Eimeria scientific community and for those researchers interested in comparative genomics of apicomplexan parasites.

Database URL:http://www.coccidia.icb.usp.br/eimeriatdb/

Molecular characterization and analysis of a novel calcium-dependent protein kinase from Eimeria tenella

The calcium-dependent protein kinases (CDPKs) are unique enzymes found only in plants, green algae, ciliates and apicomplexan parasites. In this study, a novel CDPK gene of Eimeria tenella, designed EtCDPK3, was cloned using rapid amplification of cDNA ends (RACE) based on the expressed sequence tag (EST). The entire cDNA of EtCDPK3 contained 1637 nucleotides encoding 433 amino acids and the deduced EtCDPK3 protein had canonical characteristic domains identified in other CDPKs, including a well-conserved amino-terminal kinase domain and a carboxy-terminal calmodulin-like structure with 4 EF-hand motifs for calcium binding. The expression profiles of the EtCDPK3 gene in different development stages were investigated by real-time quantitative PCR. Messenger RNA levels from the EtCDPK3 gene were higher in sporozoites than in other stages (unsporulated oocysts, sporulated oocysts and merozoites). Western blot analysis showed that rabbit antiserum against recombinant EtCDPK3 could recognize a native 49 kDa protein band of parasite. Indirect immunofluorescent antibody labelling revealed dispersed localization of EtCDPK3 during the first schizogony and intense specific staining. EtCDPK3 was located at the apical end of the sporozoites after early infection of DF-1 cells and the protein was highly expressed. Inhibition of EtCDPK3 function using specific antibodies reduced the ability of E. tenella to invade host cells. These results suggested that EtCDPK3 may be involved in invasion and survival of the parasite intracellular stages of E. tenella. Because this kinase family is absent from hosts, it represents a valid target that could be exploited for chemotherapy against Eimeria spp.

Two new Eimeria species parasitic in corncrakes (Crex crex) (Gruiformes: Rallidae) in the United Kingdom

In this study we describe 2 new species of coccidia (Apicomplexa: Eimeriidae) parasites isolated from the feces of corncrake (Crex crex) (Gruiformes: Rallidae), bred in captivity in the U.K. Oocysts of Eimeria crecis n. sp. were approximately spherical and measured 15.3 μm (13-18) × 14.3 (12-16), providing an oocyst shape index of 1.1. A micropyle and oocyst residuum were absent, but a polar granule was present. Oocysts of Eimeria nenei n. sp. were ellipsoidal and measured 23.6 (21-26) × 18.1 (17-20), providing an oocyst shape index of 1.3. A micropyle and polar granule were present. Surveying free-living, wild adult corncrakes in Scotland (U.K.) demonstrated both parasite species to be widespread. These are the first species described to infect the corncrake, and they are distinct from those previously found to infect members of the closely related crane family (Gruiformes: Gruidae). Partial amplification and sequencing of the 18S rRNA gene and internal transcribed spacer 2 indicated a close relationship between the 2 proposed new species as a group distinct from the Eimeria species known to infect cranes. These newly identified parasite species have been associated with enteric disease in corncrakes being prepared for reproduction in captivity and reintroduction into England (U.K.).

Eimeria tenella: interleukin 17 contributes to host immunopathology in the gut during experimental infection

Although IL-17 is a key factor in Th17 lineage host responses and plays critical roles in immunological control of a variety of infectious diseases, the contribution of IL-17 to immune function during Eimeria tenella infection is unknown. In the present study, we used an experimental E. tenella infection model to clarify the role of Th17-associated response in the resulting immune response by quantitative real-time PCR assays. We observed robust production of STAT-3 (the transcription factors), IL-1β, IL-6 and IL-17 in cecal intraepithelial lymphocytes during the early infection, peaking at 6h p.i. and declining thereafter. The expression of TGF-β was moderately upregulated and had 2 peaks at 6 and 72h p.i. during the early infection. To further investigate the role of chIL-17 during the infection, we treated the infected chickens with IL-17 and its neutralized antibody. As a result, the reduced fecal oocyst shedding and cecal lesion scores, but enhanced body weight gains were observed in IL-17 neutralized chickens. The results of histopathology showed that the neutrophils recruitment diminished and the parasite burden in IL-17 neutralized chickens decreased. These results may be due to the significant decrease in the production of IL-17, IL-6 and TGF-β, but enhanced IL-12 and IFN-γ expression in IL-17 neutralized chickens. The converse results were shown in IL-17 treated infected-chickens in which chickens showed increased fecal oocyst shedding, exacerbated lesion scores, and reduced body weight gains. These results suggested that chicken IL-17 might mediate E. tenella - induced immunopathology during the infection.

A review of the infection, genetics, and evolution of Neospora caninum: from the past to the present

This paper is a review of current knowledge on Neospora caninum in the context of other apicomplexan parasites and with an emphasis on: life cycle, disease, epidemiology, immunity, control and treatment, evolution, genomes, and biological databases and web resources. N. caninum is an obligate, intracellular, coccidian, protozoan parasite of the phylum Apicomplexa. Infection can cause the clinical disease neosporosis, which most notably is associated with abortion in cattle. These abortions are a major root cause of economic loss to both the dairy and beef industries worldwide. N. caninum has been detected in every country in which a study has been specifically conducted to detect this parasite in cattle. The major mode of transmission in cattle is transplacental (or vertical) transmission and several elements of the N. caninum life cycle are yet to be studied in detail. The outcome of an infection is inextricably linked to the precise timing of the infection coupled with the status of the immune system of the dam and foetus. There is no community consensus as to whether it is the dam's pro-inflammatory cytotoxic response to tachyzoites that kills the foetus or the tachyzoites themselves. From economic analysis the most cost-effective approach to control neosporosis is a vaccine. The perfect vaccine would protect against both infection and the clinical disease, and this implies a vaccine is needed that can induce a non-foetopathic cell mediated immunity response. Researchers are beginning to capitalise on the vast potential of -omics data (e.g. genomes, transcriptomes, and proteomes) to further our understanding of pathogens but especially to identify vaccine and drug targets. The recent publication of a genome for N. caninum offers vast opportunities in these areas.

Gel-Bead Delivery of Eimeria oocysts protects chickens against coccidiosis

Vaccines composed of either virulent or attenuated Eimeria spp. oocysts have been developed as an alternative to medication of feed with ionophore drugs or synthetic chemicals. The purpose of this study was to evaluate the use of gel-beads containing a mixture of Eimeria acervulina, Eimeria maxima, and Eimeria tenella oocysts as a vaccine against coccidiosis. Newly hatched chicks (Gallus gallus domesticus) were either sprayed with an aqueous suspension of Eimeria oocysts or were allowed to ingest feed containing Eimeria oocysts-incorporated gel-beads. Control day-old chicks were given an equivalent number of Eimeria oocysts (10(4) total) by oral gavage. After 3 days, chicks were randomly assigned to individual cages, and feces were collected between days 5 and 8 postinfection. All samples were processed for total Eimeria oocysts. At 4 wk of age, all chickens and a control nonimmunized group received a high-dose E acervulina, E maxima, and E. tenella challenge infection. Oocyst excretion by chicks fed gel-beads or inoculated by oral gavage was 10- to 100-fold greater than that of chicks spray-vaccinated with the Eimeria oocysts mixture (log 6.3-6.6 vs. log 4.8). Subsequent protection against challenge as measured by weight gain and feed conversion efficiency was significantly greater (P < 0.05) in gel-bead and oral gavage groups compared with spray-vaccinated or nonimmunized groups. Also, gel-bead and oral gavage groups showed no significant difference (P > 0.05) in weight gain and feed conversion efficiency compared with nonchallenged controls. These findings indicate that incorporation of Eimeria spp. oocysts in gel-beads may represent an effective way to deliver live oocyst vaccines to day-old chicks for preventing subsequent outbreaks of coccidiosis in the field.