Isolation and selection of ionophore-tolerant Eimeria precocious lines: E. tenella, E. maxima and E. acervulina

Anticoccidial activity of natural plants extracts mixture against Eimeria tenella: An in vitro and in vivo study

Coccidiosis, an acute epidemic intestinal disease of poultry, is caused by the parasitic protozoan genus Eimeria, with Eimeria tenella being the most pathogenic spp. Novel approaches are required to address the limitations of current treatments for this disease. We investigated the effects of eight plant extracts and essential oils and their mixture on Eimeria tenella as potential treatments for coccidial infection. The anticoccidial effects of non-toxic concentrations of Punica granatum L. (0.005 mg/mL), Plantago asiatica L. (0.780 mg/mL), Bidens pilosa L. (0.390 mg/mL), Acalypha australis L. (0.390 mg/mL), Pteris multifida Poir (0.050 mg/mL), and Portulaca oleracea L. sp. Pl. (0.050 mg/mL) extracts; Artemisia argyi Levl. et Vant. (0.010 μL/mL) and Camellia sinensis (L.) O. Ktze (0.050 μL/mL) essential oils; and their mixture (0.500 mL/mL) on Eimeria tenella were determined using cell viability assays, flow cytometry, and in vivo studies. The eight plant extracts and essential oils and their mixture inhibited Eimeria tenella sporozoites from invading chicken embryo fibroblast cells in vitro. The extract and essential oil mixture improved the feed conversion ratio and body weight gain, reduced fecal oocyst excretion, substantially reduced the mortality of Eimeria tenella-infected chickens, and reduced Eimeria tenella-induced cecal damage in vivo. The results suggest that the extract and essential oil mixtures inhibit Eimeria tenella invasion both in vitro and in vivo, demonstrating their potential as anticoccidial agents.

Effect of dietary sophorolipids on growth performance and gastrointestinal functionality of broiler chickens infected with Eimeria maxima

Two experiments were conducted to evaluate the effects of dietary sophorolipids (SLs) supplementation as antibiotic alternatives on growth performance and gut health of chickens infected with Eimeria maxima. In experiment 1, 336 (zero-day-old) male broilers were used. The chickens were weighed and randomly allocated to the following 6 treatments groups with 7 chickens/cage and 8 cages/treatment: control group that received a basal diet (NC), positive control group that received a basal diet and was challenged with E. maxima (PC), PC+C18:1 lactonic diacetyled SL (SL1), PC+C18:1 deacetyled SL (SL2), PC+C18:1 monoacetyled SL (SL3), and PC+C18:1 diacetyled SL (SL4). Each SL (200 mg/kg feed) was added to the corresponding treatment group. In experiment 2, 588 (zero-day-old) male broilers were used. The chickens were randomly allocated to the following experimental groups with 10 or 11 chickens/cage and 8 cages/treatment: NC, PC, PC+ monensin at 90 mg/kg feed (MO), PC+SL1 at 200 mg/kg feed (SL1 200), PC+SL1 at 500 mg/kg feed (SL1 500), PC+SL4 at 200 mg/kg feed (SL4 200), and PC+SL4 at 500 mg/kg of feed (SL4 500). The chickens and feed were weighed at 0, 7, 14, 20, and 22 d to determine growth performance. In both experiments, all chickens except the NC group were orally infected with E. maxima (10,000 oocysts/chicken) at d 14. One chicken per cage was euthanized at d 20 to sample jejunal tissue to measure lesion scores, cytokines, and tight junction (TJ) proteins. Excreta samples were collected daily between d 20 and 22 to measure oocyst numbers. Data were analyzed using Mixed Model (PROC MIXED) in SAS. In experiment 1, SLs did not affect the growth of broiler chickens, but SL4 decreased (P < 0.05) the lesion score and oocyst number compared to PC chickens. In terms of cytokines and TJ protein gene expression, SLs increased (P < 0.05) IL-1β, IL-6, IL-17F, IL-4, IL-13, occludin, and ZO1 levels compared to PC chickens. In experiment 2, monensin increased (P < 0.05) body weight, and decreased (P < 0.05) the lesion score and oocyst number compared to the PC group. SL4 500 increased (P < 0.05) average daily gain and feed conversion ratio but decreased (P < 0.05) lesion score and fecal oocyst number. SL4 decreased (P < 0.05) IL-6, IL-17F, TNFSF-15, IL-2, and IL-10 levels but increased (P < 0.05) occludin and ZO-1 levels. Overall, dietary SL supplementation, especially SL4, improved growth and gastrointestinal functionality of young broiler chickens, demonstrating significant potential as an antibiotic alternative.

Survey of coccidia on commercial broiler farms in Colombia: frequency of Eimeria species, anticoccidial sensitivity, and histopathology

Avian coccidiosis continues to be one of the costliest diseases of commercial poultry. Understanding the epidemiology of Eimeria species in poultry flocks and the resistance profile to common anticoccidials is important to design effective disease prevention and control strategies. This study examined litter samples to estimate the prevalence and distribution of Eimeria species among broiler farms in 4 geographic regions of Colombia. A total of 245 litter samples were collected from 194 broiler farms across representative regions of poultry production between March and August 2019. The litter samples were processed for oocysts enumeration and speciation after sporulation. End-point polymerase chain reaction (PCR) analysis was conducted to confirm the presence of Eimeria species. Anticoccidial sensitivity was determined with 160 Ross AP males in 5 treatment groups: noninfected, nonmedicated control (NNC), infected, nonmedicated control (INC), infected salinomycin treated (SAL, dose: 66 ppm), infected diclazuril treated (DIC, dose: 1 ppm), and infected methylbenzocuate-Clopidol treated (MET.CLO, dose: 100 ppm), All birds were orally inoculated with 1 × 106 sporulated oocysts using a 1 mL syringe, except for the NNC- group who received 1ml of water.Eimeria spp. were found in 236 (96.3%) out of 245 individual houses, representing 180 (92.8%) out of 194 farms. Eimeria acervulina was the most prevalent species (35.0%) followed by Eimeria tenella (30.9%), Eimeria maxima (20.4%), and other Eimeria spp. (13.6%). However, mixed species infections were common, with the most prevalent combination being mixtures of E. acervulina, E. maxima, E. tenella, and other species in 31.4% of the Eimeria-positive samples. PCR analysis identified E. acervulina, E. maxima, E. tenella, Eimeria necatrix, Eimeria mitis, and Eimeria praecox with variable prevalence across farms and regions. Anticoccidial sensitivity testing of strains of Eimeria isolated from 1 region, no treatment difference (P > 0.05) was observed in final weight (BW), weight gain (BWG) or feed conversion (FCR). For the global resistance index (GI) classified SAL and MET.CLO as good efficacy (85.79 and 85.49, respectively) and DIC as limited efficacy (74.52%). These results demonstrate the ubiquitous nature of Eimeria spp. and identifies the current state of sensitivity to commonly used anticoccidials in a region of poultry importance for Colombia.

Comparative Transcriptome Analyses of Drug-sensitive and Drug-resistant Strains of Eimeria tenella by RNA-sequencing

Avian coccidiosis is a widespread and economically significant disease in poultry. At present, treatment of coccidiosis mainly relies on drugs. Anticoccidial drugs can be divided into two categories: ionophorous compounds and synthetic drugs. However, the emergence of drug-resistant strains has become a challenge for coccidiosis control with anticoccidial drugs. To gain insights into the molecular mechanism governing the drug resistance of Eimeria tenella, two drug-resistant strains of E. tenella, one maduramicin-resistant (MRR) strain and one diclazuril-resistant (DZR) strain, were generated. We carried out comparative transcriptome analyses of a drug-sensitive strain (DS) and two drug-resistant MRR and DZR strains of E. tenella using RNA-sequencing. A total of 1,070 differentially expressed genes (DEGs), 672 upregulated and 398 downregulated, were identified in MRR vs. DS, and 379 DEGs, 330 upregulated and 49 downregulated, were detected in DZR vs. DS. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were performed to better understand the functions of these DEGs. In the comparison of DZR vs. DS, some DEGs were involved in peroxisome, biosynthesis of unsaturated fatty acids, and fatty acid metabolism. In the comparison of MRR vs. DS, some DEGs were involved in glycolysis/gluconeogenesis, regulation of actin cytoskeleton, and DNA replication. In addition, some DEGs coded for surface antigens that were downregulated in two drug-resistant strains involved invasion, pathogenesis, and host-parasite interactions. These results provided suggestions for further research toward unraveling the molecular mechanisms of drug resistance in Eimeria species and contribute to developing rapid molecular methods to detect resistance to these drugs in Eimeria species in poultry.

Comparison of the host cells apoptosis induced by precocious strains and virulent strains of Eimeria tenella

The present study aims to investigate the similarities and differences between the host cells apoptosis induced by virulent line of Eimeria tenella (Tsx) and precocious line (PTsx), which can provide a theoretical basis for the study of drugs and vaccines against coccidiosis. HE staining, Hoechst 33342/AnnexinV-FITC/PI composite staining, and ELISA were used to detect the infection rate, apoptosis rate, and Caspase-3 enzyme activity of host cells infected by PTsx or Tsx, respectively. The apoptotic rates and Caspase-3 absorbance of the inoculation groups were lower (P < 0.05 or P < 0.01) than those of the control group at 4 h, whereas the apoptotic rates and Caspase-3 absorbance of the inoculation groups were higher (P < 0.05 or P < 0.01) than those of the control groups at 24 to 120 h. At the same inoculation dose, there was no significant difference in the infection rate, apoptosis rate or Caspase-3 absorbance between Tsx groups and PTsx groups after E. tenella inoculation for 4 to 72 h (P > 0.05). However, these indicators of PTsx groups were lower (P < 0.01) than those of the same dose inoculated Tsx groups at 120 h. The apoptosis rates of cecal and glandular epithelial cells in the inoculated groups were higher (P < 0.01) than those in the control group after inoculated E. tenella 5 D in vivo, and the apoptosis rates of cecal and glandular epithelial cells in PTsx group was lower (P < 0.01) than that in the same dose inoculated Tsx group. These observations indicate that both Tsx and PTsx inhibit host cell apoptosis in the early development of E. tenella, induce host cell apoptosis in the middle and late stages, and the apoptosis-inducing effect on host cells increases with increasing dose. However, when the same dose of oocysts was inoculated, the amount of apoptosis induced by PTsx in late development was less than Tsx.

Establishing a Model for Evaluating Chicken Coccidiosis Resistance Based on Principal Component Analysis

Simple Summary

Avian coccidiosis, an infectious disease caused by seven species of Eimeria that can infect a bird’s digestive tract and significantly retard its growth, is a serious economic disease for chickens. Many studies have demonstrated that host resistance to coccidiosis related to genetic variations can be improved by selective breeding. The parameters for evaluation of resistance to coccidiosis could be objective indicators, such as body weight gain and cecal lesion score, or biochemical indices, such as immune factors or cytokines in the plasma or serum. The aim of the study is to establish an optimal comprehensive evaluation model including a resistance index that can be detected in live chickens (slaughter traits cannot be selected in breeding) based on principal component analysis. The value of individual chickens calculated with the optimal evaluation model is associated with the cecum lesion score; the larger the value, the stronger the resistance to coccidiosis. This illustrated that the optimal model is effective in coccidiosis resistance selection.

Abstract

To establish a coccidiosis resistance evaluation model for chicken selection, the different parameters were compared between infected and control Jinghai yellow chickens. Validation parameters were selected for principal component analysis (PCA), and an optimal comprehensive evaluation model was selected based on the significance of a correlation coefficient between coccidiosis resistance parameters and principal component functions. The following six different parameters were identified: body weight gain 3–5 days post infection and catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), malondialdehyde (MDA) and γ-interferon (IFN-γ) concentrations on the eight day post inoculation. Six principal components and one accumulated contribution of up to 80% of the evaluation models were established by PCA. The results showed that the first model was significantly or highly significantly related to nine resistance parameters (p < 0.01 or p < 0.05), especially to cecal lesions (p < 0.01). The remaining models were related to only 2–3 parameters (p < 0.01 or p < 0.05) and not to cecal lesions (p > 0.05). The values calculated by the optimal model (first model) were significantly negatively correlated with cecal lesion performance; the larger the value, the more resistant to coccidiosis. The model fi1 = −0.636 zxi1 + 0.311 zxi2 + 0.801 zxi3 − 0.046 zxi4 − 0.076 zxi5 + 0.588 zxi6 might be the best comprehensive selection index model for chicken coccidiosis resistance selection.

Oral inoculation of ultraviolet-irradiated Eimeria species oocysts protects chickens against coccidiosis

Prevention of coccidiosis is one of the best ways of controlling disease. Therefore, the present study was carried out to evaluate the protective effect of ultraviolet (UV)-irradiated sporulated oocysts of Eimeria species against coccidiosis in layer chickens. One hundred forty-four one-day-old layer chicks were randomly divided into 4 groups (n = 36), including non-immunized/non-challenged negative control group (NC group), non-immunized/challenged control group (NIC group), non-irradiated sporulated oocyst/challenged group (CA group), and UV-irradiated sporulated oocyst/challenged (UV group). At the age of 4 days, chickens in groups UV and CA were both orally inoculated with 1.0 × 10⁴ UV-irradiated and non-irradiated sporulated oocysts of Eimeria species, respectively. Chickens in groups NIC and NC were served as positive and negative controls, respectively. Chickens in all groups were orally challenged with 7.5 × 10⁴ sporulated oocysts of Eimeria species except the NC group at the age of 21 days. The results revealed that chicks receiving UV-irradiated sporulated oocysts had no signs of illness with minimal or no changes in the cecal integrity and a significantly lower oocyst shedding (OPG) than in the NIC group. Additionally, the cytokine gene expression profiles were evaluated. Expression levels of IL-2, IL-12, and IFN-γ were significantly higher in the spleen of chicks in the UV and CA groups than in the NC group post-challenge. As expected, treatment with irradiated oocysts resulted in a significant reduction in oocyst shedding and maintenance of cecal mucosal integrity. Furthermore, the body weight was higher in chickens inoculated with UV-irradiated oocysts than their non-irradiated counterparts. In conclusion, our results demonstrate that inoculation with UV-irradiated sporulated oocysts of Eimeria species can produce a substantial reduction in infection symptoms.

Protective potential of diclazuril-treated oocysts against coccidiosis in layer chicks

Diclazuril, which is widely used for the prevention of coccidiosis in chickens, has a lethal effect on asexual and sexual stages of Eimeria spp. However, little is known about its effect on the exogenous stages of Eimeria spp. In this study, we evaluated the effect of in vitro treatment with 0.2% diclazuril on unsporulated and sporulated oocysts of Eimeria spp. For this purpose, a total of 180 male layer chicks aged one day were randomly divided into 5 experimental groups. Each group was divided into 3 replicates of 12 chicks each. Group 1 (G1) and Group 2 (G2) were negative (non-immunized and non-challenged) and positive (non-immunized and challenged) controls, respectively. Group 3 (G3) was immunized per os with 1.0 × 10⁴ non-diclazuril treated-sporulated oocysts. Groups 4 (G4) was immunized per os with 0.2% diclazuril treated-unsporulated oocysts (1.0 × 10⁴) in which diclazzuril didn't affect sporulation. Group 5 (G5) was immunized per os with 0.2% diclazuril treated-sporulated oocysts (1.0 × 10⁴). Chicks of G2, G3, G4, and G5 were challenged with 7.5 × 10⁴ untreated sporulated oocysts at the age of 21 days, while the group 1 chicks remained unchallenged. G4 and G5 animals immunized with 0.2% diclazuril-treated oocysts showed a significant decrease in bloody diarrhea severity, lesion scores, and oocyst counts in comparison to those immunized with untreated oocysts. Furthermore, histopathologic findings showed a low number of parasitic stages in cecal tissues in G4 and G5. A significant increased body weight gain was observed in Gs 4 and 5 in comparison to G2. In addition, expression levels of IL-2, IL-12, and IFN-γ were significantly increased in G4 and G5. In conclusion, diclazuril is effective in attenuating Eimeria oocysts and thus provides an alternative approach for using diclazuril-treated oocysts to protect chicks against Eimeria challenge.

FRANGOS DESAFIADOS EXPERIMENTALMENTE COM Salmonella enterica SOROVAR ENTERITIDIS E Eimeria tenella E TRATADOS COM ÁCIDOS ORGÂNICOS

Resumo Foi avaliado um composto comercial de ácidos orgânicos, adicionado à ração, no controle da Salmonella de frangos de corte desafiados com Salmonella Enteritidis e Salmonella Enteritidis associadas à Eimeria tenella. Foram utilizados 504 pintos de um dia, fêmeas, da linhagem Hubbard®, sendo o delineamento inteiramente casualizado em esquema fatorial 2x3, totalizando seis tratamentos com seis repetições e 14 aves a unidade experimental. Foi analisado o pH intestinal, o escore de lesão dos cecos, contagem de oocistos fecais e a presença de salmonela no baço e tonsilas cecais das aves. Aves desafiadas com S. Enteritidis que receberam ácidos apresentaram menor frequência de isolamento da bactéria nos órgãos linfoides analisados. Assim como apresentaram redução no número de oocistos de E. tenella nas excretas coletadas diretamente na bandeja e redução dos escores de lesão intestinal provocadas pela infecção por Eimeria tenella. Os ácidos orgânicos promoveram benefício à saúde intestinal dos frangos de corte com reflexos positivos no controle da Salmonella Enteritidis juntamente com a Eimeria tenella.

Molecular Characterization and Immune Protection of a New Conserved Hypothetical Protein of Eimeria tenella

The genome sequences of Eimeria tenella have been sequenced, but >70% of these genes are currently categorized as having an unknown function or annotated as conserved hypothetical proteins, and few of them have been studied. In the present study, a conserved hypothetical protein gene of E. tenella, designated EtCHP559, was cloned using rapid amplification of cDNA 5'-ends (5'RACE) based on the expressed sequence tag (EST). The 1746-bp full-length cDNA of EtCHP559 contained a 1224-bp open reading frame (ORF) that encoded a 407-amino acid polypeptide with the predicted molecular weight of 46.04 kDa. Real-time quantitative PCR analysis revealed that EtCHP559 was expressed at higher levels in sporozoites than in the other developmental stages (unsporulated oocysts, sporulated oocysts and second generation merozoites). The ORF was inserted into pCold-TF to produce recombinant EtCHP559. Using western blotting, the recombinant protein was successfully recognized by rabbit serum against E. tenella sporozoites. Immunolocalization by using EtCHP559 antibody showed that EtCHP559 was mainly distributed on the parasite surface in free sporozoites and became concentrated in the anterior region after sporozoites were incubated in complete medium. The EtCHP559 became uniformly dispersed in immature and mature schizonts. Inhibition of EtCHP559 function using anti-rEtCHP559 polyclonal antibody reduced the ability of E. tenella sporozoites to invade host cells by >70%. Animal challenge experiments demonstrated that the recombinant EtCHP559 significantly increased the average body weight gain, reduced the oocyst outputs, alleviated cecal lesions of the infected chickens, and resulted in anticoccidial index >160 against E. tenella. These results suggest that EtCHP559 plays an important role in sporozoite invasion and could be an effective candidate for the development of a new vaccine against E. tenella.

The Molecular Characterization and Immunity Identification of Microneme 3 of Eimeria acervulina

The gene of Eimeria acervulina microneme protein 3 (EaMIC3) was cloned and characterized. According to the conserved sequence, the 3'- and 5'-ends of EaMIC3 were amplified by the rapid amplification of cDNA ends (RACE). The full length cDNA of this gene was obtained by overlapping the sequences of 3'- and 5'-extremities and amplification by reverse transcription PCR. The sequence analysis revealed that the opening reading frame (ORF) of EaMIC3 was 2,607 bp and encoded a protein of 868 amino acids with 93.04 kDa. Western blotting assay showed that the recombinant protein was successfully recognized by the sera of chickens experimentally infected with E. acervulina, whereas the native protein in the somatic extract of sporozoites was as well detected by sera from rats immunized with the recombinant protein of EaMIC3. Immunofluorescence analysis indicated that EaMIC3 was expressed in the sporozoites and merozoites stages of E. acervulina. Animal challenge experiments demonstrated that the recombinant protein of EaMIC3 could significantly increase the average body weight gains, decrease the mean lesion scores and the oocyst outputs of the immunized chickens and presented anticoccidial index (ACI) more than 165. Moreover, EaMIC3 protein produced significantly high level of IgG antibody, IFN-γ, IL-10, IL-17 TGF-β, CD4⁺ , and CD8⁺ .

Protective efficacy in chickens of recombinant plasmid pET32a(+)-ADF-3-1E of Eimeria acervulina

This experiment was conducted to study the protective efficacy of recombinant plasmid pET32a(+)-ADF-3-1E in coccidian-infected breeding chickens. The 7-day-old chickens were randomly divided into five groups: a recombinant plasmid pET32a(+)-ADF-3-1E group, a pET32a(+)-ADF group, a pET32a(+)-3-1E group, a control group, and an infection control group. The chickens were immunized intramuscularly with recombinant plasmid DNA in a dose of 200 μg, respectively, and a booster vaccination was given at the same dosage 1 week later. The peripheral blood T lymphocyte proliferation, serum IgG antibody response, and levels of interleukin 2 (IL-2) and interferon gamma (IFN-γ) were detected, respectively. The chickens were inoculated with 4 × 10(6) Eimeria acervulina-sporulated oocysts (Baoding strain) on the seventh day after the last immunization to evaluate the protective efficiency of the recombinant plasmid DNA. The results showed that the lymphocyte proliferation, serum IgG antibody, and IL-2 and IFN-γ levels in recombinant plasmid DNA group were significantly higher than those in control group (P < 0.01). The lymphocyte proliferation, serum IgG antibody, and IL-2 and IFN-γ levels in pET32a(+)-ADF-3-1E group were significantly higher than those in pET32a(+)-3-1E group and pET32a(+)-ADF group, respectively (P < 0.05). It indicated that the pET32a(+)-ADF-3-1E could produce stronger immune responses. The relative body weight gain rate in pET32a(+)-ADF-3-1E group was 88.36 %, which was significantly higher than that in control group (P < 0.05) and infection control group (P < 0.01). The reductions of oocyst production and lesion scores in pET32a(+)-ADF-3-1E group were 67.88 and 67.13 %, respectively. The oocyst excretion and the lesion score of chickens in pET32a(+)-ADF-3-1E group were lower than those in infection control group, respectively. Anticoccidial index (ACI) value in group immunized with pET32a(+)-ADF-3-1E was 169.82. ACI value of 160-179 was considered as effective. These results demonstrated that the pET32a(+)-ADF-3-1E recombinant plasmid DNA could effectively improve the cellular responses and humoral immune responses of the chickens, and it might provide protection against coccidiosis in chickens.

Poultry coccidiosis: recent advancements in control measures and vaccine development

Coccidiosis is recognized as the major parasitic disease of poultry and is caused by the apicomplexan protozoan Eimeria. Coccidiosis seriously impairs the growth and feed utilization of infected animals resulting in loss of productivity. Conventional disease control strategies rely heavily on chemoprophylaxis and, to a certain extent, live vaccines. Combined, these factors inflict tremendous economic losses to the world poultry industry in excess of USD 3 billion annually. Increasing regulations and bans on the use of anticoccidial drugs coupled with the associated costs in developing new drugs and live vaccines increases the need for the development of novel approaches and alternative control strategies for coccidiosis. This paper aims to review the current progress in understanding the host immune response to Eimeria and discuss current and potential strategies being developed for coccidiosis control in poultry.

Construction of novel cytokine by fusion of chicken IL-2 signal peptide to mature chicken IL-15 and comparison of the adjuvant effects by DNA immunization against Eimeria challenge

A novel fusion cytokine was constructed by replacing signal peptide (SP) of chicken IL-15 (ChIL-15) with SP of chicken IL-2 (ChIL-2). The fusion cytokine (NChIL-15) was cloned into the expression vector pcDNA3.1(+) to generate pcDNA-NChIL-15. An animal experiment was carried out to evaluate the adjuvant effects of NChIL-15 on DNA vaccine pcDNA-3-1E against Eimeria acervulina challenge. The mRNA profiles of ChIL-2 and ChIFN-γ in spleen were characterized by means of real-time PCR. The recombinant positive eukaryotic expression plasmid pcDNA-NChIL-15 were constructed successfully. The protective effects provided by co-immunization with 100 μg pcDNA-3-1E and 50 μg pcDNA-NChIL-15, measured by relative body weight gain (BWG), average lesion score in duodenum and oocyst decrease ratio, showed no significant difference with 50 μg pcDNA-ChIL-15 as an adjuvant on day 6 post infection (PI). However, chickens co-immunized with pcDNA-3-1E and pcDNA-NChIL-15 exhibited significant upregulated level of ChIL-2 and ChIFN-γ transcripts in spleen. Our original data suggests the constructed novel cytokine NChIL-15 could be a potential adjuvant used to enhance the immune protective effects, although the optimized dosage need to be explored further.

Anticoccidial effects of a novel triazine nitromezuril in broiler chickens

The anticoccidial efficacy of 2-(3-methyl-4-(4-nitrophenoxy)phenyl)-1,2,4-triazine-3,5(2H,4H)-dione (nitromezuril, NZL), a novel triazine compound, was evaluated in three different studies under experimental conditions. The anticoccidial efficacy was chiefly evaluated using the anticoccidial index (ACI). The resistance level was determined by calculating ACI, percentage optimum anticoccidial activity (POAA), reduction in lesion scores (RLS) and relative oocyst production (ROP). In the dose determination study (study A), NZL was added to the diet at doses of 1, 2, 3, 4, 5 and 6 mg/kg to test its efficacy against coccidiosis caused by Eimeria tenella. Groups treated with NZL 1mg/kg feed could observe the faecal dropping scores and caecal lesions. ACIs of NZL-treated groups reached 179-199. In the study on the anticoccidial efficacy of 3mg/kg NZL in the diet (study B), only a few faecal oocysts and slight lesions were observed. NZL significantly promoted weight gain (WG) and reduced lesion scores (LS) compared to controls receiving diclazuril (DZL) (P<0.05). ACIs of NZL-treated groups were 193, 192, 191 and 163 for E. tenella, Eimeria necatrix, Eimeria acervulina and Eimeria maxima, respectively, whereas those of DZL-treated groups were 185, 176, 176 and 148. In the cross-drug resistance study (study C), ACIs of NZL and toltrazuril (TZL)-treated groups ranged from 188 to 204, which were significantly higher than those of DZL-treated groups (P<0.05). NZL- and TZL-treated groups were sensitive to experimentally induced DZL-resistant E. tenella, whereas DZL-treated groups showed complete resistance. No cross-resistance was observed between DZL and NZL or TZL. Based on the abovementioned studies, it was concluded that diets containing 3 mg/kg NZL had an excellent efficacy in preventing coccidiosis in broiler chickens. The activity of 3mg/kg NZL in the diet was equal or superior to that of 1 mg/kg DZL. These results are of great significance for the future applications of NZL; however, its actual mechanism of action remains unknown. NZL is a potential novel anticoccidial agent suitable for further development.

Isolation of an Eimeria ninakohlyakimovae field strain (Canary Islands) and analysis of its infection characteristics in goat kids

The current study was conducted to isolate a field strain of Eimeria ninakohlyakimovae, characterize its infectivity and the response to challenge under experimental conditions. The isolated strain (GC) induced a prepatent period of 14-15 days p.i., a patency of 7±2 days and a noticeable pathogenicity in infected goat kids. Challenge trials resulting in a decrease of oocysts per gram counts as well as a milder intensity of clinical signs in re-infected animals indicated the capacity of this strain to induce protective immune response. Altogether, the data reported in the present study suggest that the strain E. ninakohlyakimovae GC is a useful tool for the investigation of mechanisms of pathogenicity as well as host protective immune response in caprine coccidiosis, representing a valuable prerequisite for the development of future strategies in prophylaxis and control of this important parasitic disease in goat.

Induction of Cellular Immune Response by DNA Vaccine Coexpressing E. acervulina 3-1E Gene and Mature CHIl-15 Gene

We previously reported that the chimeric DNA vaccine pcDNA-3-1E-linker-mChIL-15, fused through linking Eimeria acervulina 3-1E encoding gene and mature chicken IL-15 (mChIL-15) gene with four flexible amino acid SPGS, could significantly offer protection against homologous challenge. In the present study, the induction of cellular immune response induced by the chimeric DNA vaccine pcDNA-3-1E-linker-mChIL-15 was investigated. Spleen lymphocyte subpopulations were characterized by flow cytometric analysis. The spleen lymphocyte proliferation assays were measured by 3-[4,5-dimethylthiazol-2-y1]-2,5-diphenyltetrazolium bromide (MTT) method. The mRNA profiles of ChIL-2 and ChIFN-γ in spleen were characterized by means of real-time PCR. Chickens immunized with pcDNA-3-1E-linker-mChIL-15 exhibited significant upregulated level of ChIL-2 and ChIFN-γ transcripts in spleen following two immunizations compared with chickens in other groups (P < 0.01). In comparison with pcDNA3.1-immunized and control groups, lymphocyte proliferation, percentage of CD8α(+) cell, and levels of ChIL-2 and ChIFN-γ transcripts in the group immunized with pcDNA-3-1E-linker-mChIL-15 were significantly increased on day 6 following challenge (P < 0.05, P < 0.01, and P < 0.01, resp.). Our data suggested that the fusion antigen 3-1E-linker-mChIL-15 could be a potential candidate for E. acervulina vaccine development.

Synthesis and Anticoccidial Activity of 3-(2-(Benzofuran)-2-yl)-2-Oxoethylquinazolinone Derivatives

In order to develop novel and effective anticoccidial compounds, a series of 3-(2-(benzofuran)-2-yl)-2-oxoethylquinazolinone derivatives were designed, synthesised and evaluated as potential anticoccidial drugs. The structures of these compounds were characterised by 1H NMR, IR, HRMS spectra and elemental analysis. These compounds were tested for anticoccidial activities against Eimeria tenella according to the anticoccidial index method. 6-Chloro-3-(2-(benzofuran-2-yl)-2-oxoethyl) quinazolin-4-(3H)-one exhibited significant anticoccidial activities in the chicken's diet with a dose of 18 mg kg−1.

Synthesis and Anticoccidial Activities of Eight Novel Ethyl 7-Alkyl-6-(2-Aryloxyethoxy)-4-Hydroxyquinoline-3-Carboxylates

Eight novel ethyl 7-alkyl-6-(2-aryloxyethoxy)-4-hydroxyquinoline-3-carboxylates were synthesised and their structures were identified by 1H NMR, MS, and IR spectra. The anticoccidial activities of these compounds were evaluated according to the ACI (the anticoccidial index) method. The results showed that two of these compounds exhibited anticoccidial activities against Eimeria tenella in the chicken’ diet with a dose of 27 mg kg−1.

Immunostimulatory complexes containing Eimeria tenella antigens and low toxicity plant saponins induce antibody response and provide protection from challenge in broiler chickens

Immunostimulating complexes (ISCOMs) are unique multimolecular structures formed by encapsulating antigens, lipids and triterpene saponins and are one of the most successful antigen delivery systems for microbial antigens. In the current study, both the route of administration and the antigen concentration of ISCOMs, containing Eimeria tenella antigens and saponins from native plants, were evaluated in their ability to stimulate humoral immunity and to protect chickens against a challenge infection with E. tenella. Broiler chickens were immunized with ISCOM preparations containing E. tenella antigens and the purified saponins Gg6, Ah6 and Gp7 isolated from Glycyrrhiza glabra, Aesculus hippocastanum and Gipsophila paniculata, respectively. The effects of the route of administration, dose of antigen and type of saponin used for construction of ISCOMs were evaluated for ability to stimulate serum IgG and IgM and to protect chickens against a homologous challenge. A single intranasal immunization was the most effective route for administering ISCOMs although the in ovo route was also quite effective. Dose titration experiments demonstrated efficacy after single immunization with various ISCOM doses but maximum effects were observed when ISCOMs contain 5-10mug antigen. Immunization of birds by any of the three routes with E. tenella antigens alone or antigens mixed with alum hydroxide adjuvant resulted in lower serum antibody and reduced protection to challenge relative to immunization with ISCOMs. Overall the results of this study confirm that significant immunostimulation and protection to challenge are achieved by immunization of chickens with ISCOMs containing purified saponins and native E. tenella antigens and suggest that ISCOMs may be successfully used to develop a safe and effective vaccine for prevention of avian coccidiosis.

Synthesis and Anticoccidial Activity of ethyl 6-substitutedbenzyloxy-7-alkoxy-4-hydroxyquinoline-3-carboxylates

A series of novel ethyl 6-substitutedbenzyloxy-7-alkoxy-4-hydroxyquinoline-3-carboxylates have been designed and synthesised from 4-nitro-2-alkoxyphenol. Their structures have been characterised by 1H NMR, HRMS and IR spectra. Anticoccidial activities of these compounds were evaluated according to the ACI (the anticoccidial index) method. The results indicated that three of the tested compounds exhibited anticoccidial activities against Eimeria tenella in chicken feed with a dose of 27 mg/kg.

Eimeria tenella: analysis of differentially expressed genes in the monensin- and maduramicin-resistant lines using cDNA array

Drug resistance in coccidial populations has been a major problem to the prophylactic chemotherapy. Nevertheless, the mechanisms of the resistance are still poorly understood. In this report, cDNA array was designed based on the cDNA library for analysis of gene expression profile of the drug-resistant lines and their sensitive parental lines of Eimeria tenella. Two thousand eight hundred and six ESTs (expressed sequence tags) were obtained from 9600 clones which were randomly derived from the cDNA library with the 3' end sequencing. A total of 1424 TUTs (tentative unique transcripts) were determined from the database of our ESTs by bioinformatics analysis, from which a cDNA array was developed. The comparison of monensin-resistant line (MonR) and maduramicin-resistant line (MadR) with their sensitive parental lines was undertaken independently. It was observed that the number of the up-regulated genes was 5.58-fold more than that of the down-regulated genes in MonR when compared with its parental line. The up-regulated genes were mainly involved in cytoskeletal rearrangements and energy metabolism. In MadR, the number of the down-regulated genes was 3.07-fold more than the up-regulated genes, which were mainly related to invasion and cytoskeletal genes. However, in MadR the level of the glycometabolism-related and potential transporter genes were reduced. Our data suggest that the mechanisms of monensin and maduramicin resistance of E. tenella might be a very complex process.

Efficacy of decoquinate against drug sensitive laboratory strains of Eimeria tenella and field isolates of Eimeria spp. in broiler chickens in China

The efficacy of decoquinate against Eimeria infections in broiler chickens was evaluated using two drug sensitive laboratory strains of Eimeria tenella and 20 field isolates of Eimeria spp. collected from farms in China where various anticoccidials (including maduramicin) had been used. Decoquinate (20-40 ppm in feed) and maduramicin (5 ppm) were efficacious against E. tenella laboratory strains, but decoquinate more so than maduramicin. Body weight gains of E. tenella infected chickens were significantly improved, and caecal lesions were prevented, by feeding either decoquinate or maduramicin. Decoquinate also prevented oocyst production, but maduramicin did not. Most (18/20) Eimeria field isolates were resistant to maduramicin, judged by oocyst production; decoquinate at > or =20 ppm completely controlled all 20 field isolates. Decoquinate has potential value as a broiler anticoccidial in China and other countries where it has not been previously used.

Vaccination as a control strategy against the coccidial parasitesEimeria,ToxoplasmaandNeospora

The protozoan parasitesEimeriaspp.Toxoplasma gondiiandNeospora caninumare significant causes of disease in livestock worldwide andT. gondiiis also an important human pathogen. Drugs have been used with varying success to help control aspects of these diseases and commercial vaccines are available for all three groups of parasites. However, there are issues with increasing development of resistance to many of the anti-coccidial drugs used to help control avian eimeriosis and public concerns about the use of drugs in food animals. In addition there are no drugs available that can act against the tissue cyst stage of eitherT. gondiiorN. caninumand thus cure animals or people of infection. All three groups of parasites multiply within the cells of their host species and therefore cell mediated immune mechanisms are thought to be an important component of host protective immunity. Successful vaccination strategies for bothEimeriaandToxoplasmahave relied on using a live vaccination approach using attenuated parasites which allows correct processing and presentation of antigen to the host immune system to stimulate appropriate cell mediated immune responses. However, live vaccines can have problems with safety, short shelf-life and large-scale production; therefore there is continued interest in devising new vaccines using defined recombinant antigens. The major challenges in devising novel vaccines are to select relevant antigens and then present them to the immune system in an appropriate manner to enable the induction of protective immune responses. With all three groups of parasites, vaccine preparations comprising antigens from the different life cycle stages may also be advantageous. In the case ofEimeriaparasites there are also problems with strain-specific immunity therefore a cocktail of antigens from different parasite strains may be required. Improving our knowledge of the different parasite transmission routes, host-parasite relationships, disease pathogenesis and determining the various roles of the host immune response being at times host-protective, parasite protective and in causing immunopathology will help to tailor a vaccination strategy against a particular disease target. This paper discusses current vaccination strategies to help combat infections withEimeria,ToxoplasmaandNeosporaand recent research looking towards developing new vaccine targets and approaches.

Influence of monensin on cation influx and Na+ -K+ -ATPase activity of Eimeria tenella sporozoites in vitro

The experiments were conducted to determine intrasporozoite Na+/K+ concentrations (by AAS) and membrane-bound Na+ -K+ -ATPase activity (measured by UV-VIS with a Na+ -K+ -ATPase Detection Kit) of Eimeria tenella sporozoites of the sensitive line (i.e., the parent line, coded as OS) and 2 resistant lines, derived from the parent line (coded as OR125 and OR200), with and without in vitro exposure to monensin. These parameters for OR125 and OR200 were significantly lower than those for OS. In vitro exposure to monensin increased intrasporozoite Na+/K+ concentrations and Na+ -K+ -ATPase activity, but the stimulation on OS was significantly higher than those on OR125 and OR200, indicating that monensin had less effect on resistant parasites. The results of this study suggest that altered biochemical or physiological properties, or both, in the membranes of E. tenella might be related to a reduced sensitivity to monensin.

Experimentally induced monensin-resistant Eimeria tenella and membrane fluidity of sporozoites

Two resistant lines of Eimeria tenella (H) to monensin were developed after 35 passages in chickens medicated with 100-125 ppm or 125-200 ppm monensin in the diet. Drug sensitivity of the induced lines to different level drugs were estimated with mean lesion scores (LS), mean oocyst productions (OP), percentage optimum anticoccidial activity (POAA), reduction of lesion scores (RLS), relative oocyst production (ROP), anticoccidial index (ACI) and global index (GI), respectively. Membrane fluidity of sporozoites of the sensitive line (i.e. the parent line, coded as MON-S((S))) and two resistant lines (coded as MON-R((S))-1 and MON-R((S))-2) with and without in vitro exposure to monensin were determined. Membrane fluidity of MON-R((S))-1 and MON-R((S))-2 were significantly lower than that of MON-S((S)). In vitro exposure to monensin significantly increased membrane fluidity of MON-S((S)), but had a much less effect on those of MON-R((S))-1 and MON-R((S))-2. Sporozoits of the MON-S((S))and MON-R((S))-2 with or without in vitro exposure to monensin were examined by SEM, and the sensitive sporozoites (MON-S((S))) appeared swollen and bulgy after treatment with monensin, while there was no obvious morphological deformation in the resistant sporozoites (MON-R((S))-2). The results suggest that the altered membrane fluidity in the membranes of E. tenella may be related to the decreased sensitivity to monensin.

Guidelines for evaluating the efficacy and safety of live anticoccidial vaccines, and obtaining approval for their use in chickens and turkeys

These guidelines are intended to aid those engaged in poultry research in the design, implementation and interpretation of laboratory, floor-pen and field studies for the assessment of the efficacy and safety of live anticoccidial vaccines for immunization of chickens and turkeys against Eimeria species. In addition to efficacy and safety requirements, manufacture, quality control and licensing considerations are discussed. The guidelines do not address subunit vaccines comprising non-viable material, but many of the principles described will be relevant to such vaccines if they are developed in the future. Guidelines are available in some countries for avian vaccines of bacterial or viral origin but specific standards for anticoccidial vaccines in poultry have not, as far as we know, been produced. Information is provided on general requirements of registration authorities (based upon regulations applicable in the European Union and the USA) for obtaining marketing authorizations for vaccines. These guidelines may assist poultry specialists in providing specific information for administrators involved in the decision-making process leading to registration of new vaccines, and are intended to facilitate the worldwide adoption of consistent, standard procedures.

Intercurrent coccidiosis and necrotic enteritis of chickens: rational, integrated disease management by maintenance of gut integrity

Coccidiosis and necrotic enteritis (NE) are globally common, sometimes intercurrent, diseases of poultry. The risk of NE, due to the Gram-positive bacterium Clostridium perfringens, has increased in recent years because of the voluntary or legally required withdrawal of the use of certain in-feed antibiotic growth promoters with anticlostridial activity. In-feed ionophorous anticoccidial drugs incidentally also possess anticlostridial activity. Such ionophores, although not banned, are usually precluded when live anticoccidial vaccines are used, potentially increasing yet further the risk of NE. This review provides information for the design of rational, integrated management strategies for the prevention and control of coccidiosis and NE in chickens by maintaining gut integrity. Because of differences in local availability of feed ingredients and national legislations regarding antibiotic growth promoters and anticoccidial vaccine licensing, no universal strategy is applicable. The diseases and their interactions are described under the headings of forms of disease, diagnosis, sources of infection, pathophysiological effects, predisposing factors, and control methods. Elements of gut integrity, which influences host predisposition and clinical responses to disease, include physical development, immune competence, gut enzyme activity, mucin production, gut flora and epithelial damage. Experimental studies of coccidiosis and NE are compared, and where possible reconciled, with field observations. Gaps in knowledge and necessary further experiments are identified. Insights are provided regarding interactions between coccidiosis, NE, and the use of live anticoccidial vaccines. Recent changes in NE prevalence in commercial flocks, and their possible causes, are discussed. The necessarily wide range of topics reviewed emphasizes the enormous complexity of this disease combination, and indicates the importance of a multidisciplinary approach in order to reduce its harmful impact on the world's poultry industry.

Responses of chickens vaccinated with a live attenuated multi-valent ionophore-tolerant Eimeria vaccine

Coccidiosis, caused by Eimeria species, is a serious economic disease of chickens (Gallus gallus) and the search for vaccines to control the disease is intensifying especially with the increasing threat of drug resistance. A live attenuated multi-valent ionophore-tolerant Eimeria vaccine has been developed that contains three ionophore-resistant Eimeria species, E. tenella, E. maxima and E. acervulina. The attenuated lines were derived from virulent field strains resistant to monensin ionophore by selection for early development in chicks. The vaccine was administered by gavage and through drinking water to broiler chickens, Chinese Yellow strain, reared in wire cages. Vaccinated medicated birds performed better than vaccinated unmedicated and medicated unvaccinated groups. The final mean weights of vaccinated medicated birds were significantly higher (P<0.05), and a better vaccine protection index, using both vaccinating methods, was achieved. Results indicated that concomitant use of ionophores and vaccines could be a useful adjunct to planned immunization in the control of coccidiosis.