A selective review of advances in coccidiosis research

Anticoccidial and jejunum-protective effects of Krameria lappacea roots extract on experimental Eimeria papillata infection

Coccidiosis is a protozoan parasitic disease caused by Eimeria species and affects wild and domestic animals. Coccidiostats are currently available to control this disease, although drug resistance has been confirmed for all of them. As a result, there is an urgent need to identify eco-friendly agents to control and treat this disease. This study aimed to investigate the ameliorative role of the Krameria lappacea roots extract (KLRE) on the outcome of coccidiosis induced by Eimeria papillata. Male C57BL/6 mice were divided into seven groups (5 mice/group), as follows: Group 1: noninfected-nontreated (control group), Group 2: noninfected-treated group with KLRE (200 mg/kg), Group 3: infected-nontreated group, Group 4: infected-treated group with KLRE (50 mg/kg), Group 5: infected-treated group with KLRE (100 mg/kg), Group 6: infected-treated group with KLRE (200 mg/kg), and Group 7: infected-treated group with amprolium (120 mg/kg). Groups (3-7) were inoculated orally with 1 × 103 sporulated E. papillata oocysts. One hour after infection, groups (4-6) were daily treated for 5 days with KLRE and amprolium. On day 5 postinfection, oocyst output was determined, and mice were euthanized for the collection of jejuna then preparation of histological sections and jejunal homogenate was used for the determination of biochemical and oxidative damage markers. The coccidial infection induced weight loss of mice by 3.971%, which improved after KLRE to -1.512%. After KLRE treatment, the rate of feed intake was improved to be 52.21 ± 2.30 than those in infected group (40.47 ± 2.25). Oocyst output was significantly reduced in mice treated with KLRE (1.308 × 106 oocysts/g.feces) compared with those in the infected group (5.387 × 106 oocysts/g.feces). E. papillata infection induced marked histological alterations within jejunum tissue. After treatment, KLRE was able to impair the development of parasite stages (meronts, gamonts, and developing oocysts) in the jejunum through a significant reduction of number and size in comparison with the infected group. Infection with E. papillata induced a disturbance in the nutrient absorption in the jejunal mice tissue, which improved after the treatment with KLRE and amprolium. Also, KLRE counteracted significantly the E. papillata-induced loss of reduced glutathione and total antioxidant capacity. Our findings indicate that KLRE could be used as an alternative to the available coccidiostats currently available. RESEARCH HIGHLIGHTS: Krameria lappacea exhibit significant anticoccidial and antioxidant activities induced by E. papillata infection. Krameria lappacea exhibit significant improvement in the pathological alterations of the jejunal tissue induced by E. papillata infection.

Supplementing low protein diets with methionine or threonine during mixed Eimeria challenge

We investigated the effects of supplementing low protein diets with methionine (Met) or threonine (Thr) during a mixed Eimeria (consisting of E. acervulina, E. maxima and E. tenella) challenge in broilers. All birds were fed the same starter diet (d1-9) and finisher diet (d28-35) which met Cobb 500 nutrient specifications. Birds were allocated to 1 of 4 dietary treatments from d9 to 28: a standard protein diet (19% CP); a low protein diet (16% CP); or the low protein diet supplemented with Met or Thr at 50% above recommendations. On d14, half of the birds were challenged, and half of the birds were unchallenged. From d14 to 28, feed intake was recorded daily and BW every 3 or 4 d. Oocyst excretion was measured daily from d18 to 27. On d21 and 28, 3 birds per pen were euthanized to assess nutrient digestibility, cytokine expression and intestinal histology. During the acute stage of the challenge, challenged birds reduced ADFI and ADG (P < 0.05). In the pre-patent and recovery stages, birds given the 16% CP diets increased ADFI (P < 0.05), meanwhile there were no differences in ADG in these stages (P > 0.05). Nutrient digestibility was reduced in challenged birds in the acute stage (P < 0.05) but tended to be greater than in unchallenged birds during the recovery stage. There was no significant effect of diet on oocyst excretion or intestinal histology (P > 0.05). Interactions were observed between diet and challenge on IL-10 and IL-21 expression in the cecal tonsils during the acute stage of the challenge (P < 0.05), due to reduced IL-10 expression in challenged Thr birds and greater IL-21 expression in challenged Met birds. Supplementation with Thr or Met had limited effects on the outcomes of a mixed Eimeria challenge but provides benefits to the host by enhancing their immune response.

Prevalence of coccidia in lagomorphs in China between 1981 and 2023: A systematic review and meta-analysis

Lagomorpha coccidiosis, caused by coccidia, is a prevalent disease affecting rabbits, hares and pikas. This meta-analysis aimed to estimate the pooled prevalence of coccidia infection in lagomorphs and identify potential risk factors. A systematic search of six databases yielded 102 studies published between 1981 and 2023. The pooled prevalence of Eimeriidae, Sarcocystidae and Cryptosporidiidae in lagomorphs was 76.4%, 6.2% and 3.9%, respectively. Rabbits had the highest prevalence of Eimeriidae (76.8%) and Sarcocystidae (7.4%), while pikas had the highest prevalence of Cryptosporidiidae (6.2%). Juvenile rabbits exhibited the highest prevalence of Eimeriidae (84.6%) and Cryptosporidiidae (9.9%). Northwest China had the highest prevalence of Eimeriidae (87.8%). Over time, the prevalence of Eimeriidae declined (Coefficient: -0.0062; P<0.05), but remained high (65.0%) in the past five years. Our findings highlight the prevalence of Eimeriidae infection in lagomorphs and the need for further research on Sarcocystidae and Cryptosporidiidae infections. We emphasize the importance of developing lagomorpha coccidia vaccines and implementing vaccination schedules for juvenile rabbits to mitigate coccidia infections.

Metaphylactic strategies using toltrazuril against coccidiosis in goat kids

Goat coccidiosis compromises animal welfare, reduces productivity and may cause mortality and delayed growth rates in goat kids around the weaning period worldwide. This field study was conducted to evaluate the efficacy of metaphylactic treatments with two doses of toltrazuril (20 or 40 mg/kg body weight - BW, p. o.), at different timing, in kids naturally infected with Eimeria spp. A total of 97 healthy goat kids (Majorera milk aptitude breed) were divided into five groups, depending on the age of treatment (2 or 7 weeks). One group remained untreated as a negative control until the end of the study. Faecal oocyst shedding, faecal consistency, and body weight of the animals were monitored at day 0 and at weekly intervals. Counts of oocysts per gram of faeces (OPG) were determined by a modified McMaster technique. Morphometric identification of Eimeria species was carried out on individual faecal samples from each experimental group after oocyst sporulation. Goat kids treated at two weeks of age maintained OPG values close to zero during the 5 weeks post-treatment and, overall, had lower faecal oocyst counts than untreated control animals. No significant differences were observed between the two doses of toltrazuril used in two-week-old treated animals. By contrast, when treatment was carried out at seven weeks of age, the dose of 40 mg/kg BW of toltrazuril reduced oocyst levels for longer and to a greater extent than the 20 mg/kg dose. Irrespectively of the treatment and dose, toltrazuril delayed the appearance of pathogenic Eimeria species, i. e. Eimeria ninakohlyakimovae and Eimeria arloingi. As a whole, Eimeria christenseni, with a rather moderate pathogenicity, was highly predominant throughout the study period, including the untreated control group, which was probably the reason why clinical signs of coccidiosis were barely observed throughout the experiment. Under these circumstances, the positive effect of toltrazuril on body weight condition observed in some treated groups was difficult to correlate to the timing and doses. Metaphylactic treatments with 20 mg/kg BW toltrazuril given at two weeks of age are sufficient to control oocyst excretion in goat kids; whereas if administered later in 7-week-old animals, thereby coinciding with the frequently observed peak of oocyst elimination in goat kids under field conditions, a higher dose might be advisable to prevent environmental contamination with infectious oocysts.

Integrated application of transcriptomics and metabolomics provides insight into the mechanism of Eimeria tenella resistance to maduramycin

Avian coccidiosis, caused by Eimeria parasites, continues to devastate the poultry industry and results in significant economic losses. Ionophore coccidiostats, such as maduramycin and monensin, are widely used for prophylaxis of coccidiosis in poultry. Nevertheless, their efficacy has been challenged by widespread drug resistance. However, the underlying mechanisms have not been revealed. Understanding the targets and resistance mechanisms to anticoccidials is critical to combat this major parasitic disease. In the present study, maduramycin-resistant (MRR) and drug-sensitive (DS) sporozoites of Eimeria tenella were purified for transcriptomic and metabolomic analysis. The transcriptome analysis revealed 5016 differentially expressed genes (DEGs) in MRR compared to DS, and KEGG pathway enrichment analysis indicated that DEGs were involved in spliceosome, carbon metabolism, glycolysis, and biosynthesis of amino acids. In the untargeted metabolomics assay, 297 differentially expressed metabolites (DEMs) were identified in MRR compared to DS, and KEGG pathway enrichment analysis indicated that these DEMs were involved in 10 pathways, including fructose and mannose metabolism, cysteine and methionine metabolism, arginine and proline metabolism, and glutathione metabolism. Targeted metabolomic analysis revealed 14 DEMs in MRR compared to DS, and KEGG pathway analysis indicated that these DEMs were involved in 20 pathways, including fructose and mannose metabolism, glycolysis/gluconeogenesis, and carbon metabolism. Compared to DS, energy homeostasis and amino acid metabolism were differentially regulated in MRR. Our results provide gene and metabolite expression landscapes of E. tenella following maduramycin induction. This study is the first work involving integrated transcriptomic and metabolomic analyses to identify the key pathways to understand the molecular and metabolic mechanisms underlying drug resistance to polyether ionophores in coccidia.

Comparative proteomic analysis across the developmental stages of the Eimeria tenella

Eimeria tenella is the main pathogen responsible for coccidiosis in chickens. The life cycle of E. tenella is, arguably, the least complex of all Coccidia, with only one host. However, it presents different developmental stages, either in the environment or in the host and either intracellular or extracellular. Its signaling and metabolic pathways change with its different developmental stages. Until now, little is known about the developmental regulation and transformation mechanisms of its life cycle. In this study, protein profiles from the five developmental stages, including unsporulated oocysts (USO), partially sporulated (7 h) oocysts (SO7h), sporulated oocysts (SO), sporozoites (S) and second-generation merozoites (M2), were harvested using the label-free quantitative proteomics approach. Then the differentially expressed proteins (DEPs) for these stages were identified. A total of 314, 432, 689, and 665 DEPs were identified from the comparison of SO7h vs USO, SO vs SO7h, S vs SO, and M2 vs S, respectively. By conducting weighted gene coexpression network analysis (WGCNA), six modules were dissected. Proteins in blue and brown modules were calculated to be significantly positively correlated with the E. tenella developmental stages of sporozoites (S) and second-generation merozoites (M2), respectively. In addition, hub proteins with high intra-module degree were identified. Gene Ontology (GO) and Kyoto Encyclopedia of Gene and Genomes (KEGG) pathway enrichment analyses revealed that hub proteins in blue modules were involved in electron transport chain and oxidative phosphorylation. Hub proteins in the brown module were involved in RNA splicing. These findings provide new clues and ideas to enhance our fundamental understanding of the molecular mechanisms underlying parasite development.

Quercetin as a Promising Antiprotozoan Phytochemical: Current Knowledge and Future Research Avenues

Despite tremendous advances in the prevention and treatment of infectious diseases, only few antiparasitic drugs have been developed to date. Protozoan infections such as malaria, leishmaniasis, and trypanosomiasis continue to exact an enormous toll on public health worldwide, underscoring the need to discover novel antiprotozoan drugs. Recently, there has been an explosion of research into the antiprotozoan properties of quercetin, one of the most abundant flavonoids in the human diet. In this review, we tried to consolidate the current knowledge on the antiprotozoal effects of quercetin and to provide the most fruitful avenues for future research. Quercetin exerts potent antiprotozoan activity against a broad spectrum of pathogens such as Leishmania spp., Trypanosoma spp., Plasmodium spp., Cryptosporidium spp., Trichomonas spp., and Toxoplasma gondii. In addition to its immunomodulatory roles, quercetin disrupts mitochondrial function, induces apoptotic/necrotic cell death, impairs iron uptake, inhibits multiple enzymes involved in fatty acid synthesis and the glycolytic pathways, suppresses the activity of DNA topoisomerases, and downregulates the expression of various heat shock proteins in these pathogens. In vivo studies also show that quercetin is effective in reducing parasitic loads, histopathological damage, and mortality in animals. Future research should focus on designing effective drug delivery systems to increase the oral bioavailability of quercetin. Incorporating quercetin into various nanocarrier systems would be a promising approach to manage localized cutaneous infections. Nevertheless, clinical trials are needed to validate the efficacy of quercetin in treating various protozoan infections.

Developing efficient strategies for localizing the enhanced yellow fluorescent protein subcellularly in transgenic Eimeria parasites

Eimeria species serve as promising eukaryotic vaccine vectors. And that the location of heterologous antigens in the subcellular components of genetically modified Eimeria may determine the magnitude and type of immune responses. Therefore, our study aimed to target a heterologous fluorescent protein to the cell surface or microneme, two locations where are more effective in inducing protective immunity, of Eimeria tenella and E. acervulina sporozoites. We used an enhanced yellow fluorescent protein (EYFP) as a tagging biomarker, fusing variously with some localization or whole sequences of compartmental proteins for targeting. After acquiring stable transgenic Eimeria populations, we observed EYFP expressing in expected locations with certain strategies. That is, EYFP successfully localized to the surface when it was fused between signal peptides and mature products of surface antigen 1 (SAG1). Furthermore, EYFP was efficiently targeted to the apical end, an optimal location for secretory organelle known as the microneme, when fused to the C terminus of microneme protein 2. Unexpectedly, EYFP exhibited dominantly in the apical end with only weak expression on the surface of the transgenic sporozoites when the parasites were transfected with plasmid with EYFP fused between signal peptides and mature products of E. tenella SAG 13. These strategies worked in both E. tenella and E. acervulina, laying a solid foundation for studying E. tenella and E. acervulina-based live vaccines that can be further tailored to the inclusion of cargo immunogens from other pathogens.

Prevalence and Risk Factors of Eimeria spp. in Broiler Chickens from Pichincha and Santo Domingo de los Tsáchilas, Ecuador

Coccidiosis in chickens is a parasitic disease of economic importance for the poultry industry. In Ecuador, there is limited information regarding the prevalence of Eimeria spp. on commercial broiler farms. Therefore, a total of 155 poultry farms in the provinces of Pichincha and Santo Domingo de los Tsáchilas were surveyed. The analysis of fresh fecal samples was conducted to determine the parasitic load of six of the seven chicken Eimeria species (excluding E. mitis) through multiplex PCR. Additionally, an epidemiological survey was performed to assess the risk factors associated with the infection using a multivariable logistic regression model. All samples tested positive for the presence of Eimeria spp., despite the farmers having implemented prophylactic measures, and no clinical coccidiosis cases were recorded. The parasitic load varied between 25 and 69,900 oocyst per gram. The species prevalence was as follows: Eimeria spp. 100%, E. maxima 80.4%, E. acervulina 70.6%, E. praecox 55.4%, E. tenella 53.6%, E. necatrix 52.2%, and E. brunetti 30.8%. The main species combination was E. cervuline, E. maxima, E. necatrix, and E. praecox (23.90%), followed by E. tenella, as a unique species (10.69%), and then E. acervulina, E. maxima, and E. praecox (8.81%). It was observed that farms operated by independent producers had a higher amount of Eimeria spp. and higher probability of the presence of E. brunetti, E. necatrix, E. praecox, and E. tenella. Poultry houses located below 1300 m above sea level were associated with a higher parasitic load and the presence of E. brunetti. Birds younger than 35 days of age and from open-sided poultry houses (with rudimentary environmental control) had a higher probability of presenting E. maxima. Drinking water from wells increased the risk of E. praecox presence. Research aimed at designing control strategies to improve health management on poultry farms in the region would help minimize the impact of coccidiosis.

Microbiota promotes recruitment and pro-inflammatory response of caecal macrophages during E. tenella infection

BACKGROUND

Eimeria genus belongs to the apicomplexan parasite phylum and is responsible for coccidiosis, an intestinal disease with a major economic impact on poultry production. Eimeria tenella is one of the most virulent species in chickens. In a previous study, we showed a negative impact of caecal microbiota on the physiopathology of this infection. However, the mechanism by which microbiota leads to the physiopathology remained undetermined. Macrophages play a key role in inflammatory processes and their interaction with the microbiota during E. tenella infection have never been investigated. We therefore examined the impact of microbiota on macrophages during E. tenella infection. Macrophages were monitored in caecal tissues by immunofluorescence staining with KUL01 antibody in non-infected and infected germ-free and conventional chickens. Caecal cells were isolated, stained, analyzed and sorted to examine their gene expression using high-throughput qPCR.

RESULTS

We demonstrated that microbiota was essential for caecal macrophage recruitment in E. tenella infection. Furthermore, microbiota promoted a pro-inflammatory transcriptomic profile of macrophages characterized by increased gene expression of NOS2, ACOD1, PTGS2, TNFα, IL1β, IL6, IL8L1, IL8L2 and CCL20 in infected chickens. Administration of caecal microbiota from conventional chickens to germ-free infected chickens partially restored macrophage recruitment and response.

CONCLUSIONS

Taken together, these results suggest that the microbiota enhances the physiopathology of this infection through macrophage recruitment and activation. Consequently, strategies involving modulation of the gut microbiota may lead to attenuation of the macrophage-mediated inflammatory response, thereby limiting the negative clinical outcome of the disease.

Live attenuated anticoccidial vaccines for chickens

Chicken coccidiosis, caused by infection with single or multiple Eimeria species, results in significant economic losses to the global poultry industry. Over the past decades, considerable efforts have been made to generate attenuated Eimeria strains, and the use of live attenuated anticoccidial vaccines for disease prevention has achieved tremendous success. In this review, we evaluate the advantages and limitations of the methods of attenuation as well as attenuated Eimeria strains in a historical perspective. Also, we summarize the recent exciting research advances in transient/stable transfection systems and clustered regularly interspaced short palindromic repeats (CRISPR)-based genome editing developed for Eimeria parasites, and discuss trends and challenges of developing live attenuated anticoccidial vaccines based on transgenesis and genome editing.

Protection against Eimeria intestinalis infection in rabbits immunized with the recombinant elongation factors EF1α and EFG

Eimeria intestinalis is the most pathogenic species of rabbit coccidiosis, causing weight loss, diarrhea, and even acute death. The currently used anticoccidial drugs against E. intestinalis in rabbits are associated with drug resistance and residues. Immunological control might be a potential alternative. We cloned and expressed the E. intestinalis recombinant EF1α and EFG (rEi-EF1α and rEi-EFG, respectively). Rabbits were immunized subcutaneously every 14 days with 100 µg of rEi-EF1α and rEi-EFG and followed by 5 × 104 E. intestinalis sporulated oocysts orally challenge. Serum samples were collected every 7 days to measure the levels of specific antibodies and cytokines. On post-challenge day 14, rabbits were sacrificed and the anticoccidial index was evaluated. The rabbits of PBS challenged groups exhibited anorexia, diarrhea, marked intestinal wall thickening, and white nodules that formed patches, while rabbits from the rEi-EF1α or rEi-EFG challenged group exhibited milder symptoms. The rEi-EF1α group showed a 75.18% oocyst reduction and 89.01%wt gain; the rEi-EFG group had a 60.58% oocyst reduction and 56.04%wt gain. After vaccination, specific IgG levels increased and stayed high (P < 0.05). The IL-4 and IL-2 levels of rEi-EF1α immunized groups showed a significant increase after immunization (P < 0.05). Both rEi-EF1α and rEi-EFG could induce humoral and cellular immune responses. In contrast, rabbits immunized with rEi-EF1α were better protected from challenge by E. intestinalis than rEi-EFG.

Impacts of Eimeria coinfection on growth performance, intestinal health and immune responses of broiler chickens

Coccidiosis caused by Eimeria is one of the most severe chicken diseases and imposes huge economic losses to the poultry industry globally. Multi-Eimeria species coinfections are common with the most prevalent combination being mixtures of Eimeria acervulina and Eimeria tenella. Although detrimental impacts of either E. acervulina or E. tenella on chicken health are well recognized, no information is available regarding their coinfection effects so far. This study was designed to investigate the influence of coinfection with E. acervulina and E. tenella on broiler chickens. 144 one-day-old broiler chickens within each of trials (trial I or II) were divided into four groups, namely, control group (CG), E. acervulina infection group (EAIG), E. tenella infection group (ETIG) and dual (E. acervulina and E. tenella) infection group (DIG). Then, chickens were measured for weight loss, lesion scores, oocyst outputs, histological changes and expressions of pro-inflammatory (interleukin [IL]-6, IL-8 and IL-18), regulatory (IL-10 and IL-22) cytokines and Toll-like receptors (TLR; TLR2 and TLR4) as well as intestinal barrier (mucin 2 [MUC2] and fattey acid-bingding proteins 2 and 6 [FABP2 and FABP6])- and tight junction (TJ; zonula occluden-1 [ZO-1], occludin [OCLN], and claudins 1 and 5 [CLDN1 and CLDN5])-related proteins at 3, 5, 7, 10, 14 and 21 days post-infection, respectively. Our results consistently showed that although ETIG and DIG exhibited a higher level of weight loss and a more amount of oocyst excretion than EAIG, DIG had lighter lesions than EAIG in the early phase because of coinfection with E. tenella. A higher (P < 0.05) ratio of duodenal villous height to crypt depth was also observed in DIG than EAIG. Moreover, histological changes in the duodenum and cecum varied by single and dual Eimeria infections. Expressions of the intestinal barrier- and TJ-related genes of EAIG, ETIG and DIG were significantly (P < 0.05) upregulated but their levels exhibited differential changes among infected chickens. Similarly, the infected chickens showed significant (P < 0.05) inflammatory responses and higher (P < 0.05) expressions of TLRs in the intestines in comparison to CG. These results presented a comprehensive physiological, pathological and immunological characterization of E. acervulina and E. tenella coinfection in broiler chickens and also shed insights into pathogenesis of multi-coccidia coinfections.

Gastrointestinal parasites of domestic sheep from Patagonia throughout historical times: A paleoparasitological approach

Sheep husbandry in Patagonia, Argentina, started at the beginning of the 20th century from European settlers. Sanitary management is minimal, which has serious implications for the sheep health. Sheep can be infested by diverse parasites, with well over 150 species of internal and external parasites reported worldwide. Gastrointestinal parasitism is one of the most common and important infections in sheep concerning the health status, and is the cause of significant morbidity and mortality, which generates considerable production losses. The present work is the first paleoparasitological study of sheep coprolites from Patagonia throughout historical times. Fifty-seven coprolites from the 'Cueva Peligro' archaeological site (Patagonia, Argentina) were analyzed using the Lutz spontaneous sedimentation technique and the modified Faust flotation technique. Ancient DNA (aDNA) study was carried out in order to identify the zoological origin of coprolites. The results obtained from Cytb analysis confirmed the identity of the host as Ovis aries (domestic sheep). A total of 39 coprolites examined were positive for parasites by at least one of the studied methods. Thirty eight samples were positive by spontaneous sedimentation and 10 samples were positive by the modified Faust technique. The parasitic fauna found was Trichuris sp. (Trichinellida: Trichuridae), Nematodirus sp., Nematodirus spathiger (Strongylida, Trichostrongyloidea), two unidentified Strongylida-type egg morphotypes, Fasciola hepatica (Trematoda: Digenea) and coccidia oocysts of Eimeria spp. (Apicomplexa: Eimeriidae). The modified Faust technique provided satisfactory results in terms of sensitivity for the detection of Eimeria spp. The use of this methodology as a routine procedure enables the processing of ancient samples, in order to increase recoveries. These results show the importance of integrating different diagnostic approaches in order to optimize parasitic findings. The recorded parasite diversity appears to have not changed over the last 120 years. The study displayed the presence of different parasitic species which suggests potential exposure to parasitic diseases through the historical times, both for sheep and for other domestic and wild mammals from Patagonia. Also, suggests the presence of fasciolosis, a zoonotic disease that implies a potential risk for Patagonian populations in the past.

Molecular characterization of methionine aminopeptidase1 from Eimeria tenella

Coccidiosis, a serious intestinal parasitic disease caused by Eimeria spp., can result in huge annual economic losses to the poultry industry worldwide. At present, coccidiosis is mainly controlled by anticoccidial drugs. However, drug resistance has developed in Eimeria because of the long-term and unreasonable use of the drugs currently available. In our previous study, RNA-seq showed that the expression of methionine aminopeptidase1 (EtMetAP1) was up-regulated in diclazuril-resistant (DZR) and maduramicin-resistant (MRR) strains compared to drug-sensitive (DS) strain of Eimeria tenella. In this study, EtMetAP1 was cloned and expressed, and the function and characteristics of the EtMetAP1 protein were analyzed. The transcription and translation levels of EtMetAP1 in DS strain of E. tenella at different developmental stages were analyzed by qPCR and western blotting. We found that the transcription and translation levels of EtMetAP1 in second-generation merozoites (SM) were higher than those of the other three stages (unsporulated oocyst, sporulated oocyst, and sporozoites). Simultaneously, qPCR was used to analyze the mRNA transcription levels of EtMetAP1 in DS, DZR, MRR, and salinomycin-resistant (SMR) strain. The results showed that compared to the sensitive strain, the transcription levels of EtMetAP1 in DZR and MRR were up-regulated. There was no significant difference in transcription level in SMR. Indirect immunofluorescence localization showed that the protein was mainly localised in the cell membrane and cytoplasm of sporozoites and SM. An invasion inhibition test showed that anti-rEtMetAP1 polyclonal antibody could effectively inhibit the sporozoite invasion of host cells. These results suggest that the protein may be involved in the growth and development of parasites in host cells, the generation of drug resistance, and host cell invasion.

The effects of protease, xylanase, and xylo-oligosaccharides on growth performance, nutrient utilization, short-chain fatty acids, and microbiota in Eimeria-challenged broiler chickens fed low-protein diet

A total of 392 Cobb 500 off-sex male broiler chicks were used in a 21-day experiment to study the effect of protease, xylanase, and xylo-oligosaccharides (XOS) on improving growth performance, nutrient utilization (ileal digestibility and total tract retention), gene expression of nutrient transporters, cecal short-chain fatty acids (SCFAs), and microbiota profile of broilers challenged with Eimeria spp. Chicks at 0-day old were allocated to 8 treatments in a 4 × 2 factorial arrangement: 1) corn-soybean meal diet with no enzyme (Con); 2) Con plus 0.2 g/kg protease alone (PRO); 3) Con plus 0.2 g/kg protease combined with 0.1 g/kg xylanase (PRO + XYL); or 4) Con plus 0.5 g/kg xylo-oligosaccharides (XOS); with or without Eimeria challenge. The 4 diets were formulated to be marginally low in crude protein (183 g/kg). Challenged groups were inoculated with a solution containing E. maxima, E. acervulina, and E. tenella oocysts on d 15. Eimeria depressed (P < 0.01) growth performance and nutrient utilization. Supplemental protease improved (P < 0.05) body weight gain and feed intake in the prechallenge phase (d 0-15) but had no effect during the infection period (d 15-21). There was no interaction between infection and feed supplementation for nutrient utilization. The supplementations of either PRO or XOS alone increased (P < 0.01) total tract retention of Ca and tended (P < 0.1) to improve total tract retention of N, P, AME, and AMEn. Eimeria decreased (P < 0.05) expressions of GLUT2, GLUT5, PepT1, ATP2B1, CaSR, Calbidin D28K, NPT2, and ZnT1 but increased (P < 0.01) expression of GLUT1. XOS supplementation increased (P < 0.05) ATP2B1 expression. Protease decreased (P < 0.05) isobutyrate concentration in unchallenged treatments but not in challenged treatments. Eimeria decreased (P < 0.01) cecal saccharolytic SCFAs acetate and propionate but increased (P < 0.01) branched-chain fatty acid isovalerate. The supplementation of PRO + XYL or XOS increased (P < 0.05) cecal butyrate or decreased cecal isobutyrate concentrations, respectively. PRO + XYL and XOS decreased cecal protein levels in unchallenged birds but not challenged ones. Eimeria challenge significantly (P < 0.05) decreased the microbial richness (Observed features) and diversity (Shannon index and phylogenetic diversity) and changed the microbial composition by reducing the abundance of certain bacteria, such as Ruminococcus torques, and increasing the abundance of others, such as Anaerostipes. In contrast, none of the additives had any significant effect on the cecal microbial composition. In conclusion, PRO or XOS supplementation individually improved nutrient utilization. All the additives decreased the cecal content of branched-chain fatty acids, consistent with decreased cecal N concentration, although the effects were more pronounced in unchallenged birds. In addition, none of the feed additives impacted the Eimeria-induced microbial perturbation.

Molecular characterization and protective efficacy of vacuolar protein sorting 29 from Eimeria tenella

Introduction

Vacuolar protein sorting 29 (VPS29) is a core component of the retromer-retriever complex and is essential for recycling numerous cell-surface cargoes from endosomes. However, there are no reports yet on VPS29 of Eimeria spp.

Methods

Here, we cloned and prokaryotically expressed a partial sequence of Eimeria tenella VPS29 (EtVPS29) with RT-PCR and engineered strain of Escherichia coli respectively. The localization of the VPS29 protein in E. tenella sporozoites was investigated with immunofluorescence (IFA) and overexpression assays. And its protective efficacy against E. tenella infection was investigated in chickens with the animal protection test.

Results

An EtVPS29 gene fragment with an ORF reading frame of 549 bp was cloned. The band size of the expressed recombinant protein, rEtVPS29, was approximately 39 kDa and was recognized by the chicken anti-E. tenella positive serum. EtVPS29 protein was observed widely distributing in the cytoplasm of E. tenella sporozoites in the IFA and overexpression assays. rEtVPS29 significantly increased average body weight gain and decreased mean lesion score and oocyst output in chickens. The relative weight gain rate in the rEtVPS29-immunized group was 62.9%, which was significantly higher than that in the unimmunized and challenged group (P < 0.05). The percentage of reduced oocyst output in the rEtVPS29 immunized group was 32.2%. The anticoccidial index of the rEtVPS29-immunized group was 144.2. Serum ELISA also showed that rEtVPS29 immunization induced high levels of specific antibodies in chickens.

Discussion

These results suggest that rEtVPS29 can induce a specific immune response and is a potential candidate for the development of novel vaccines against E. tenella infections in chickens.

Amplicon sequencing allows differential quantification of closely related parasite species: an example from rodent Coccidia (Eimeria)

BACKGROUND

Quantifying infection intensity is a common goal in parasitological studies. We have previously shown that the amount of parasite DNA in faecal samples can be a biologically meaningful measure of infection intensity, even if it does not agree well with complementary counts of transmission stages (oocysts in the case of Coccidia). Parasite DNA can be quantified at relatively high throughput using quantitative polymerase chain reaction (qPCR), but amplification needs a high specificity and does not simultaneously distinguish between parasite species. Counting of amplified sequence variants (ASVs) from high-throughput marker gene sequencing using a relatively universal primer pair has the potential to distinguish between closely related co-infecting taxa and to uncover the community diversity, thus being both more specific and more open-ended.

METHODS

We here compare qPCR to the sequencing-based amplification using standard PCR and a microfluidics-based PCR to quantify the unicellular parasite Eimeria in experimentally infected mice. We use multiple amplicons to differentially quantify Eimeria spp. in a natural house mouse population.

RESULTS

We show that sequencing-based quantification has high accuracy. Using a combination of phylogenetic analysis and the co-occurrence network, we distinguish three Eimeria species in naturally infected mice based on multiple marker regions and genes. We investigate geographical and host-related effects on Eimeria spp. community composition and find, as expected, prevalence to be largely explained by sampling locality (farm). Controlling for this effect, the novel approach allowed us to find body condition of mice to be negatively associated with Eimeria spp. abundance.

CONCLUSIONS

We conclude that amplicon sequencing provides the underused potential for species distinction and simultaneous quantification of parasites in faecal material. The method allowed us to detect a negative effect of Eimeria infection on the body condition of mice in the natural environment.

First report of Eimeria myoxi in the garden dormouse (Eliomys quercinus Linnaeus, 1766) from Doñana Natural Area (Andalusia, SW Spain)

This work reports for the first time the presence and molecular characterization of Eimeria myoxi in the garden dormouse (Eliomys quercinus) from the Doñana Natural Area (Andalusia, SW Spain). Fresh faecal samples were collected from a total of 28 garden dormice, which were caught following current guidelines for the ethical use of animals in research, and processing by a standard flotation technique with saturated saline solution. Then, wet drops were examined microscopically, and the number of oocysts was semi-quantified. Eimeria oocysts were observed in 16 of the 28 (57.1%) faecal samples, showing most of them a very low number of oocysts (≤1 oocyst per microscopic field × 400). The unsporulated oocysts visualized in 16 faecal samples were subspherical and of length 19.2 ± 1.2 μm and width 17.4 ± 1.1 μm, being morphologically compatible with E. myoxi. This finding was supported by molecular analysis of the small subunit ribosomal RNA (SSU-rRNA) gene, identifying the same species in 22 of the 28 (78.6%) dormice, including 15 samples in which oocyst size was compatible with E. myoxi. Moreover, the subsequent analyses of the apicoplast open reading frame 470 (ORF470) and the mitochondrial cytochrome c oxidase subunit I (COI) genes confirmed the molecular identification of the isolates as E. myoxi. The phylogeny analyses were consistent with previous phylogenetic studies and support the existence of three lineages of rodent-infecting Eimeria species.

Forward genetic analysis of monensin and diclazuril resistance in Eimeria tenella

Worldwide distributed coccidiosis is caused by infection of both Eimeria species and Cystoisospora in the host intestine and causes huge economic losses to the livestock industry, especially the poultry industry. The control of such diseases relies mainly on chemoprophylaxis with anticoccidials, which has led to a very common drug resistance in this field. However, the genetic mechanisms underlying resistance to many anticoccidial drugs remain unknown. In this study, strains of E. tenella resistant to 250 mg/kg monensin were generated and characterized. Forward genetic approaches based on pooled genome sequencing, including experimental evolution and linkage group selection, were used to locate candidate targets responsible for resistance to monensin and diclazuril in E. tenella. A total of 16 nonsynonymous mutants in protein-coding genes were identified in monensin-resistant strains, and two genomic regions with strong selection signals were also detected in diclazuril-resistant strains. Our study reveals the genetic characterization of the experimental evolution and linkage group selection in Eimeria species, and also provides important information that contributes to the understanding of the molecular mechanism of drug resistance in coccidia.

Transcriptome mining of RNA viruses (family Totiviridae ) in Eimeria necatrix and Eimeria stiedai

Coccidian protozoa from the genus Eimeria are widespread parasites of vertebrates, causing serious disease (coccidiosis) and economic loss most notably in poultry. Several species of Eimeria are themselves infected with small RNA viruses assigned to the family Totiviridae . In this study, the sequences of two such viruses were newly determined, one of which represents the first complete protein-coding sequence of a virus from E. necatrix , an important pathogen of chickens, and the other of which is from E. stiedai , an important pathogen of rabbits. Sequence features of the newly identified viruses, compared with those of ones reported previously, provide several insights. Phylogenetic analyses suggest that these eimerian viruses constitute a well-demarcated clade, probably deserving of recognition as a distinct genus.

In Vitro Transcriptional Response of Eimeria tenella to Toltrazuril Reveals That Oxidative Stress and Autophagy Contribute to Its Anticoccidial Effect

Intestinal coccidiosis is a common parasitic disease in livestock, caused by the infection of Eimeria and Cystoisospora parasites, which results in great economic losses to animal husbandry. Triazine compounds, such as toltrazuril and diclazuril, are widely used in the treatment and chemoprophylaxis of coccidiosis. Unfortunately, widespread drug resistance has compromised their effectiveness. Most studies have focused on prophylaxis and therapeutics with toltrazuril in flocks, while a comprehensive understanding of how toltrazuril treatment alters the transcriptome of E. tenella remains unknown. In this study, merozoites of E. tenella were treated in vitro with 0.5 μg/mL toltrazuril for 0, 1, 2 and 4 h, respectively. The gene transcription profiles were then compared by high-throughput sequencing. Our results showed that protein hydrolysis genes were significantly upregulated after drug treatment, while cell cycle-related genes were significantly downregulated, suggesting that toltrazuril may affect parasite division. The expression of redox-related genes was upregulated and elevated levels of ROS and autophagosomes were detected in the parasite after toltrazuril treatment, suggesting that toltrazuril may cause oxidative stress to parasite cells and lead to its autophagy. Our results provide basic knowledge of the response of Eimeria genes to toltrazuril and further analysis of the identified transcriptional changes can provide useful information for a better understanding of the mechanism of action of toltrazuril against Eimeria.

A Europium Nanosphere-Based Time-Resolved Fluorescent Immunochromatographic Assay for the Rapid Screening of 4,4'-Dinitrocarbanilide: Aiming at Improving Strip Method Performance

Considering that the strip method is simple and convenient for users, a Europium nanosphere-based time-resolved fluorescent immunochromatographic assay (TRFICA) for the rapid screening of 4,4'-dinitrocarbanilide (DNC) was developed to improve the performance of strip assays. After optimization, TRFICA showed IC₅₀, the limit of detection, and cut-off values of 0.4, 0.07, and 5.0 ng mL^-1, respectively. No significant cross-reactivity (CR < 0.1%) with 15 DNC analogs was observed in the developed method. TRFICA was validated for DNC detection in spiked chicken homogenates, and recoveries ranged from 77.3% to 92.7%, with coefficients of variation of <14.9%. Moreover, the time needed for the detection procedure, including the sample pre-treatment, was less than 30 min for TRFICA, which had never been achieved before in other immunoassays. The newly developed strip test is a rapid, sensitive, quantitative, and cost-effective on-site screening technique for DNC analysis in chicken muscle.

Microbiome of Ceca from Broiler Chicken Vaccinated or Not against Coccidiosis and Fed Berry Pomaces

American cranberry (Vaccinium macrocarpon) and lowbush/wild blueberry (V. angustifolium) pomace are polyphenol-rich products having potentially beneficial effects in broiler chickens. This study investigated the cecal microbiome of broiler-vaccinated or non-vaccinated birds against coccidiosis. Birds in each of the two groups (vaccinated or non-vaccinated) were fed a basal non-supplemented diet (NC), a basal diet supplemented with bacitracin (BAC), American cranberry (CP), and lowbush blueberry (BP) pomace alone or in combination (CP + BP). At 21 days of age, cecal DNA samples were extracted and analyzed using both whole-metagenome shotgun sequencing and targeted-resistome sequencing approaches. Ceca from vaccinated birds showed a lower abundance of Lactobacillus and a higher abundance of Escherichia coli than non-vaccinated birds (p < 0.05). The highest and lowest abundance of L. crispatus and E. coli, respectively, were observed in birds fed CP, BP, and CP + BP compared to those from NC or BAC treatments (p < 0.05). Coccidiosis vaccination affected the abundance of virulence genes (VGs) related to adherence, flagella, iron utilization, and secretion system. Toxin-related genes were observed in vaccinated birds (p < 0.05) in general, with less prevalence in birds fed CP, BP, and CP + BP than NC and BAC (p < 0.05). More than 75 antimicrobial resistance genes (ARGs) detected by the shotgun metagenomics sequencing were impacted by vaccination. Ceca from birds fed CP, BP, and CP + BP showed the lowest (p < 0.05) abundances of ARGs related to multi-drug efflux pumps, modifying/hydrolyzing enzyme and target-mediated mutation, when compared to ceca from birds fed BAC. Targeted metagenomics showed that resistome from BP treatment was distant to other groups for antimicrobials, such as aminoglycosides (p < 0.05). Significant differences in the richness were observed between the vaccinated and non-vaccinated groups for aminoglycosides, β-lactams, lincosamides, and trimethoprim resistance genes (p < 0.05). Overall, this study demonstrated that dietary berry pomaces and coccidiosis vaccination significantly impacted cecal microbiota, virulome, resistome, and metabolic pathways in broiler chickens.

Comprehensive molecular characterization of complete mitogenome assemblies of 33 Eimeria isolates infecting domestic chickens

BACKGROUND

Coccidiosis caused by Eimeria is one of the most severe chicken diseases and poses a great economic threat to the poultry industry. Understanding the evolutionary biology of chicken Eimeria parasites underpins development of new interactions toward the improved prevention and control of this poultry disease.

METHODS

We presented an evolutionary blueprint of chicken coccidia by genetically characterizing complete mitogenome assemblies of 33 isolates representing all seven known Eimeria species infecting chickens in China. Further genome- and gene-level phylogenies were also achieved to better understand the evolutionary relationships of these chicken Eimeria at the species level.

RESULTS

33 mitogenomes of chicken eimerian parasites ranged from 6148 bp to 6480 bp in size and encoded typical mitochondrial compositions of apicomplexan parasites including three protein-coding genes (PCGs), seven fragmented small subunit (SSU) and 12/13 fragmented large subunit (LSU) rRNAs. Comparative genomics provided an evolutionary scenario for the genetic diversity of PCGs-cytochrome c oxidase subunits 1 and 3 (cox1 and cox3) and cytochrome b (cytb); all were under purifying selection with cox1 and cox3 being the lowest and highest evolutionary rates, respectively. Genome-wide phylogenies classified the 33 Eimeria isolates into seven subgroups, and furthermore Eimeria tenella and Eimeria necatrix were determined to be more closely related to each other than to the other eight congenic species. Single/concatenated mitochondrial protein gene-based phylogenies supported cox1 as the genetic marker for evolutionary and phylogenetic studies for avain coccidia.

CONCLUSIONS

To our knowledge, these are the first population-level mitogenomic data on the genus Eimeria, and its comprehensive molecular characterization provides valuable resources for systematic, population genetic and evolutionary biological studies of apicomplexan parasites in poultry.

Evidence of high-efficiency cross fertilization in Eimeria acervulina revealed using two lines of transgenic parasites

Eimeria species are apicomplexan parasites with a direct life cycle consisting of a replicative phase involving multiple rounds of asexual replication in the intestine or other organs including kidneys, liver, and gallbladder, depending on the species, followed by a sexual phase or gamogony involving the development and fertilization of gametes, an essential process for Eimeria transmission. Recent advances in the genetic manipulation of these parasites made it possible to conduct genetic crosses combined with genomic approaches to elucidate the genetic determinants of Eimeria development, virulence, drug resistance, and immune evasion. Here, we employed genetic techniques to generate two transgenic Eimeria acervulina lines, EaGAM56 and EaHAP2, each expressing two unique fluorescent proteins, with one controlled by a constitutive promotor for cross-efficiency analysis and the other by a male or female gametocyte stage-specific promoter to observe sexual development. The expression of fluorescent proteins in the transgenic lines was analyzed in different developmental stages of the E. acervulina life cycle by immunoblotting and by examination of frozen sections using fluorescence microscopy. The effect of infective doses on cross-fertilization was further investigated by conducting several genetic crosses between the two transgenic lines at different doses and ratios. Two transgenic lines expressing constitutive and gametocyte-specific fluorescence proteins were generated and characterized. These transgenic parasites display synchronous development in chickens, comparable with that of the wild type. Genetic crosses between the two transgenic parasites showed that a high rate of oocysts co-expressing the two reporters could be achieved following inoculation with high doses of infective oocysts. We further showed that the proportion of co-transfected oocysts can be modulated by altering the ratio of the transgenic parental lines. Higher infective doses and similar numbers of functional gametocytes from the parents increase the rate of cross-fertilization. Our data highlight the usefulness of genetic manipulation and fluorescently-labeled transgenic gametocytes as tools to study Eimeria development and to elucidate the factors that modulate sexual development. This work sets the stage for the implementation of novel approaches to investigate other aspects of Eimeria pathogenesis, virulence, and drug susceptibility and resistance.

Construction of a Lactobacillus plantarum-based claudin-3 targeting delivery system for the development of vaccines against Eimeria tenella

Avian coccidiosis causes huge economic losses to the poultry industry worldwide and currently lacks effective live vector vaccines. Achieving efficient antigen delivery to mucosa-associated lymphoid tissue (MALT) is critical for improving the effectiveness of vaccines. Here, chicken claudin-3 (CLDN3), a tight junction protein expressed in MALT, was identified as a target, and the C-terminal region of Clostridium perfringens enterotoxin (C-CPE) was proven to bind to chicken CLDN3. Then, a CLDN3-targeting Lactobacillus plantarum NC8-expressing C-CPE surface display system (NC8/GFP-C-CPE) was constructed to successfully express the heterologous protein on the surface of L. plantarum. The colonization level of NC8/GFP-C-CPE was significantly increased compared to the non-targeting strain and could persist in the intestine for at least 72 h. An oral vaccine strain expressing five EGF domains of Eimeria tenella microneme protein 8 (EtMIC8-EGF) (NC8/EtMIC8-EGF-C-CPE) was constructed to evaluate the protective efficacy against E. tenella infection. The results revealed that CLDN3-targeting L. plantarum induced stronger mucosal immunity in gut-associated lymphoid tissues (GALT) as well as humoral responses and conferred better protection in terms of parasite replication and pathology than the non-targeting strain. Overall, we successfully constructed a CLDN3-targeting L. plantarum NC8 surface display system characterized by MALT-targeting, which is an efficient antigen delivery system to confer enhanced protective efficacy in chickens against E. tenella infection.

Genomic heterozygosity is associated with parasite abundance, but the effects are not mediated by host condition

Whether, when, and how genetic diversity buffers individuals and populations against infectious disease risk is a critical and open question for understanding wildlife disease and zoonotic disease risk. Several, but not all, studies have found negative relationships between infection and heterozygosity in wildlife. Since they can host multiple zoonotic infections, we sampled a population of wild deer mice (Peromyscus maniculatus), sequenced their genomes, and examined their fecal samples for coccidia and nematode eggs. We analyzed coccidia infection status, abundance, and coinfection status in relation to per-locus and per-individual measures of heterozygosity, as well as identified SNPs associated with infection status. Since heterozygosity might affect host condition, and condition is known to affect immunity, it was included as a co-variate in the per-individual analyses and as response variable in relation to heterozygosity. Not only did coccidia-infected individuals have lower levels of genome-wide per-locus diversity across all metrics, but we found an inverse relationship between genomic diversity and severity of coccidia infection. We also found weaker evidence that coinfected individuals had lower levels of private allelic variation than all other groups. In the per-individual analyses, relationships between heterozygosity and infection were marginal but followed the same negative trends. Condition was negatively correlated with infection, but was not associated with heterozygosity, suggesting that effects of heterozygosity on infection were not mediated by host condition in this system. Association tests identified multiple loci involved in the inflammatory response, with a particular role for NF-κB signaling, supporting previous work on the genetic basis of coccidia resistance. Taken together, we find that increased genome-wide neutral diversity, the presence of specific genetic variants, and improved condition positively impact infection status. Our results underscore the importance of considering host genomic variation as a buffer against infection, especially in systems that can harbor zoonotic diseases.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10682-022-10175-8.

A century of "anticoccidial drugs": bibliometric analysis

Publications are an important measure of scientific and technological progress. The quantitative examination of the number of publications in a certain research topic is known as bibliometrics. Bibliographic studies are widely used to analyse the condition of research, future potential, and current growth patterns in a certain topic. It can serve as a basis for making decisions and implementing strategies to achieve long-term development goals. To our knowledge, no research has been conducted in these domains; so, this work aims to employ bibliometric analysis to provide comprehensive data on publications related to anticoccidial drugs. As a result, the current study uses bibliometric analysis to track the evolution of anticoccidial drugs and its consequences in the academic and public worlds via a survey of relevant scientific and popular publications. The Dimensions database was used to retrieve the bibliographical statistics, which were then cleaned and analyzed. The data was also loaded into the VOS viewer, which generated a network visualization of the authors with the most joint articles. The investigation discovered three stages of publications and citations since the first article on anticoccidial drugs in 1949. The first stage, which ran from 1920 to 1968, was characterized by a scarcity of research articles on anticoccidial drugs. From 1969 to 2000, the second stage was marked by a stable and marginally increased number of articles. The scientific field was characterized by an increasing trend in the number of publications and their citations from 2002 to 2021. The study gave a complete list of the top anticoccidial drugs funding agents, countries, research institutes, most cited publications, and important co-authorship and partnerships. The outcomes of the study will help veterinary practitioners and researchers understand the trends and best sources of knowledge in the field of anticoccidial medications.

Phenotypic characterization of Eimeria tenella-specific chicken T-cells responding to in vitro parasite antigen re-stimulation

Introduction. Coccidiosis, caused by protozoan parasites of genus Eimeria, is a disease with large impact on poultry production worldwide. It is well known that Eimeria immunity is dependent on Th1-type responses.Gap Statement. In vitro assessment of Eimeria-specific T-cell activity would therefore be a valuable research tool but has so far proven difficult to establish.Aim. The present study aimed to evaluate in vitro induced blast transformation and CD25 expression in defined chicken T-cell populations as a measure of Eimeria immunity.Methodology. Three E. tenella infection experiments were performed and PBMC and/or spleen cells were collected between 6 and 16 days after infection of chickens. Cells were stimulated in vitro with E. tenella antigens and T-cell activation was assessed by immunofluorescence labelling and flow cytometry.Results. The results consistently showed statistically significant E. tenella specific activation of TCRα/β+T cells within a 'window' from 8 to 14 days after infection for both spleen cells and PBMC. Responding T-cells were identified as CD4+CD8-, CD4+CD8αα+ and CD4-CD8αβ+ where the CD4+CD8αα+ cells generally showed the highest responses. All three of these TCRα/βT-cell subsets showed significant E. tenella induced blast transformation and/or CD25 expression albeit not always in concert on the same days after infection indicating complex kinetics of T-cell responses. In general, responses were higher for spleen cells compared to PBMC for all responding T-cell populations.Conclusions. This methodology shows promise to study Eimeria-specific T-cells, e.g. to evaluate vaccine responses. Results indicated that a Th1-type response was induced and suggested a role for CD4+CD8αα+ cells in Eimeria immunity.

A reliable and low-cost deep learning model integrating convolutional neural network and transformer structure for fine-grained classification of chicken Eimeria species

Chicken coccidiosis is a disease caused by Eimeria spp. and costs the broiler industry more than 14 billion dollars per year globally. Different chicken Eimeria species vary significantly in pathogenicity and virulence, so the classification of different chicken Eimeria species is of great significance for the epidemiological survey and related prevention and control. The microscopic morphological examination for their classification was widely used in clinical applications, but it is a time-consuming task and needs expertise. To increase the classification efficiency and accuracy, a novel model integrating transformer and convolutional neural network (CNN), named Residual-Transformer-Fine-Grained (ResTFG), was proposed and evaluated for fine-grained classification of microscopic images of seven chicken Eimeria species. The results showed that ResTFG achieved the best performance with high accuracy and low cost compared with traditional models. Specifically, the parameters, inference speed and overall accuracy of ResTFG are 1.95M, 256 FPS and 96.9%, respectively, which are 10.9 times lighter, 1.5 times faster and 2.7% higher in accuracy than the benchmark model. In addition, ResTFG showed better performance on the classification of the more virulent species. The results of ablation experiments showed that CNN or Transformer alone had model accuracies of only 89.8% and 87.0%, which proved that the improved performance of ResTFG was benefit from the complementary effect of CNN's local feature extraction and transformer's global receptive field. This study invented a reliable, low-cost, and promising deep learning model for the automatic fine-grain classification of chicken Eimeria species, which could potentially be embedded in microscopic devices to improve the work efficiency of researchers and extended to other parasite ova, and applied to other agricultural tasks as a backbone.

Automated enumeration of Eimeria oocysts in feces for rapid coccidiosis monitoring

Coccidiosis represents a major driver in the economic performance of poultry operations, as coccidia control is expensive, and infections can result in increased feed conversion ratios, uneven growth rates, increased co-morbidities with pathogens such as Salmonella, and mortality within flocks. Shifts in broiler production to antibiotic-free strategies, increased attention on pre-harvest food safety, and growing incidence of anti-coccidial drug resistance has created a need for increased understanding of interventional efficacy and methods of coccidia control. Conventional methods to quantify coccidia oocysts in fecal samples involve manual microscopy processes that are time and labor intensive and subject to operator error, limiting their use as a diagnostic and monitoring tool in animal parasite control. To address the need for a high-throughput, robust, and reliable method to enumerate coccidia oocysts from poultry fecal samples, a novel diagnostic tool was developed. Utilizing the PIPER instrument and MagDrive technology, the diagnostic eliminates the requirement for extensive training and manual counting which currently limits the application of conventional microscopic methods of oocysts per gram (OPG) measurement. Automated microscopy to identify and count oocysts and report OPG simplifies analysis and removes potential sources of operator error. Morphometric analysis on identified oocysts allows for the oocyst counts to be separated into 3 size categories, which were shown to discriminate the 3 most common Eimeria species in commercial broilers, E. acervulina, E. tenella, and E. maxima. For 75% of the samples tested, the counts obtained by the PIPER and hemocytometer methods were within 2-fold of each other. Additionally, the PIPER method showed less variability than the hemocytometer counting method when OPG levels were below 100,000. By automated identification and counting of oocysts from 12 individual fecal samples in less than one hour, this tool could enable routine, noninvasive diagnostic monitoring of coccidia in poultry operations. This approach can generate large, uniform, and accurate data sets that create new opportunities for understanding the epidemiology and economics of coccidia infections and interventional efficacy.

RPA assay coupled with CRISPR/Cas12a system for the detection of seven Eimeria species in chicken fecal samples

Chicken coccidiosis is one of the most common and economically important diseases in the global poultry industry, and it is caused by at least one of the seven Eimeria species. A simple and reliable way to distinguish Eimeria species in infected chicken is critical for the surveillance, control, and eradication of chicken coccidiosis. In this study, a recombinase polymerase amplification (RPA) assay coupled with the clustered regularly interspaced short palindromic repeats (CRISPR)/Cas12a system (RPA-CRISPR/Cas12a) was developed for the detection of Eimeria species in chicken fecal samples. This assay is highly specific to the seven Eimeria species and it does not cross react between species. Assessment of analytical sensitivity revealed that a single copy of plasmid DNA could be detected. Comparative analysis revealed strong agreement between RPA-CRISPR/Cas12a assays and real-time qPCR to reliably detect all seven Eimeria species in fecal chicken samples. Importantly, the cleavage products could be visualized under a blue light instrument, making it possible for the rapid detection of Eimeria species for on-site testing. Collectively, our study demonstrated that RPA-CRISPR/Cas12a assays offer a simple and reliable diagnostic method for Eimeria species.

Genetic selection of Eimeria parasites in the chicken for improvement of poultry health: implications for drug resistance and live vaccine development

AbstractApicomplexan parasites of the genus Eimeria are widespread in poultry flocks and can cause the intestinal disease coccidiosis. Early studies, concerned with intraspecific variation in oocyst morphology, indicated that phenotypic changes may be induced by selection experiments conducted in vivo. Genetic selection driven by targeted selection for specific phenotypes has contributed to our understanding of the phenomenon of drug resistance and the development of live attenuated vaccines. Our present knowledge regarding genetics of Eimeria is largely based upon the utilization of such selected strains as genetic markers. Practical advantages of working with Eimeria spp. in the chicken are discussed. The selection of drug resistant strains by serial propagation has provided useful information regarding the mechanisms of drug resistance and likely longevity of anticoccidial drugs when introduced in the field. Selection experiments to develop precocious strains of Eimeria and growth in chicken embryos have contributed to the development of safe and effective live attenuated vaccines for control of coccidiosis. Establishment of protocols for genetic complementation by transient or stable transfection of Eimeria is now supporting direct manipulation of parasite genotypes, creating opportunities to expand the range and value of live parasite vaccines. Procedures for developing drug resistant and precocious lines of Eimeria and/or genetic markers described here are likely to prove useful for researchers investigating the propensity for resistance development to novel compounds and the development of new attenuated vaccines. Such investigations can be helpful in providing a better understanding of biochemical and molecular aspects of the biology of these parasites.

Identification and Characterization of Eimeria tenella Rhoptry Protein 35 (EtROP35)

Simple Summary

Rhoptry proteins (ROPs) of phylum Apicomplexa parasites are important secretory virulence factors as well as candidate vaccines. However, studies on ROPs of Eimeria tenella are limited. In this study, the coding sequence of E. tenella rhoptry protein 35 (EtROP35) was cloned, and then its localization, expression in parasite, potential role within invasion, and protective efficacy were investigated. Sequence analysis and subcellular localization revealed that EtROP35 is a rhoptry protein of E. tenella. Sporozoite invasion-blocking assay and protective efficacy indicated that EtROP35 might be involved in the parasite invasion process and may be a potential vaccine candidate against E. tenella.

Abstract

Rhoptry proteins (ROPs) of Apicomplexa are crucial secreted virulence factors and sources of vaccine candidates. To date, Eimeria tenella ROPs are not well studied. This study identified and characterized a novel E. tenella ROP (EtROP35), which showed the highest levels among 28 putative ROPs in previous sporozoite and merozoite transcriptomes. Sequence analysis showed that EtROP35 contains an N-terminal secretory signal and a protein kinase domain including eight conserved ROP35-subfamily motifs. Subsequent experiments confirmed that it is a secretory protein. Subcellular localization revealed it localized at the apical end of the sporozoites and merozoites, which was consistent with the ROPs of other Apicomplexan parasites. To further understand the biological meaning of EtROP35, expression levels in different developmental stages and sporozoite invasion-blocking assay were investigated. EtROP35 showed significantly higher levels in sporozoites (6.23-fold) and merozoites (7.00-fold) than sporulated oocysts. Sporozoite invasion-blocking assay revealed that anti-EtROP35 polyclonal antibody significantly reduced the sporozoite invasion rate, suggesting it might participate in host cell invasion and be a viable choice as a vaccine candidate. The immunological protective assays showed that EtROP35 could induce a high level of serum IgY and higher mean body weight gain, and lower cecum lesion score and oocysts excretion than the challenged control group. These data indicated that EtROP35 had good immunogenicity and may be a promising vaccine candidate against E. tenella.

An update on T2-toxins: metabolism, immunotoxicity mechanism and human assessment exposure of intestinal microbiota

Mycotoxins are naturally produced secondary metabolites or low molecular organic compounds produced by fungus with high diversification, which cause mycotoxicosis (food contamination) in humans and animals. T-2 toxin is simply one of the metabolites belonging to fungi trichothecene mycotoxin. Specifically, Trichothecenes-2 (T-2) mycotoxin of genus fusarium is considered one of the most hotspot agricultural commodities and carcinogenic compounds worldwide. There are well-known examples of salmonellosis in mice and pigs, necrotic enteritis in chickens, catfish enteric septicemia and colibacillosis in pigs as T-2 toxic agent. On the other hand, it has shown a significant reduction in the Salmonella population's aptitude in the pig intestinal tract. Although the impact of the excess Fusarium contaminants on humans in creating infectious illness is less well-known, some toxins are harmful; for example, salmonellosis and colibacillosis have been frequently observed in humans. More than 20 different metabolites are synthesized and excreted after ingestion, but the T-2 toxin is one of the most protuberant metabolites. Less absorption of mycotoxins in intestinal tract results in biotransformation of toxic metabolites into less toxic variants. In addition to these, effects of microbiota on harmful mycotoxins are not limited to intestinal tract, it may harm the other human vital organs. However, detoxification of microbiota is considered as an alternative way to decontaminate the feed for both animals and humans. These transformations of toxic metabolites depend upon the formation of metabolites. This study is complete in all perspectives regarding interactions between microbiota and mycotoxins, their mechanism and practical applications based on experimental studies.

Efficacy of Ficus sycomorus (Sycamore Fig) Extract on Intestinal Coccidiosis in Experimentally Infected Rabbits

This study was conducted to investigate the effect of the Ficus sycomorus extract on Eimeria intestinalis in experimentally infected rabbits. For this purpose, forty male 30-day-old rabbits (Blanc de Bouscat) were divided into four groups (n = 10 in each group). Rabbits kept in the first group served as negative control (non-treated-non-infected). Rabbits kept in the second, third, and fourth groups were challenged at 10 weeks old with 3 × 10⁴E. intestinalis sporulated oocysts. The third and fourth groups were treated orally with diclazuril 10% (0.05 mg/kg body weight) and F. sycomorus (100 mg/Kg) for three consecutive days, respectively. The efficacy was assessed based on the growth performance parameters, clinical symptoms, oocyst shedding, histopathological findings, and hematological parameters for 16 days post challenge. The study revealed that rabbits treated with F. sycomorus methanolic extract and diclazuril showed mild clinical symptoms with a significant decrease in oocyst shedding compared with the positive control. Moreover, the diclazuril-treated group showed the highest leukocytic count and the lowest monocytes percentage compared with other groups. Furthermore, the lowest lymphocytes percentage was recorded in the control positive group. Histopathologically, moderate coccidia infestation in the intestinal mucosa and moderate hydropic degeneration of hepatocytes were observed in the diclazuril treated group compared with the negative control. However, mild coccidia infestation in the intestinal mucosa and slight coagulative necrosis of hepatocytes was found in the F. sycomorus treated group. In conclusion, F. sycomorus methanolic extract had promising effects on the live performance, oocyst count, and blood variables, while it possesses adverse consequences on the hepatic tissues. Further studies are required to optimize the dose and extraction method to mitigate its side effects.

PCR identification and prevalence of Eimeria species in commercial turkey flocks of the Midwestern United States

The present study used a PCR approach to characterize prevalence of coccidial species in fecal samples obtained from 40 individual Midwestern turkey flocks to characterize distribution of species in commercial flocks. Each sample was screened for 6 prominent Eimeria species using species-specific primers and was supplemented with a primary nested-PCR approach for amplification of mitochondrial cytochrome c oxidase subunit gene I where initial sample DNA concentrations were low. All samples were positive for at least one species of Eimeria, while most presented 2 (20/40) or 3 (14/40) species in total. Prevalence across farms was primarily dominated by E. meleagrimitis (97.50%), E. adenoeides (95%), and E. gallopavonis (40%). Of the samples positive for E. adenoeides and E. meleagrimitis, almost half (17/40) contained additional species. Data presented here offer insight into Eimeria species currently challenging the Midwestern US turkey industry and potential need to evaluate flocks for species prior to implementing vaccination programs.

An Eimeria maxima Antigen: Its Functions on Stimulating Th1 Cytokines and Protective Efficacy Against Coccidiosis

A consensus is that the Th1 immune response plays a predominant role against avian coccidiosis. Therefore, an antigen with the ability to induce Th1 cytokine responses is an ideal candidate for the development of coccidiosis vaccines. In our previous study, EmARM-β, a Th1 cytokines-stimulating antigen, was screened from the cDNA expression library of Eimeria maxima (E. maxima). Herein, we verified its stimulative effects on Th1 cytokine productions and evaluated its protective efficacy against E. maxima infection. Recombinant EmARM-β protein was expressed, and eukaryotic expression plasmid pVAX1-EmARM-β was also constructed for the immunization of birds. An immunofluorescence assay was performed to detect the native form of EmARM-β protein in the stage of sporozoites. Expressions of specific transcription factors and cytokines in immunized chickens were measured using qPCR and ELISA to verify its stimulating function on Th1 cytokines. Specific IgG antibody levels and T lymphocyte subpopulation in the immunized chickens were detected using ELISA and indirect flow cytometry to determine induced immune responses. The results showed that EmARM-β native protein is massively expressed in the sporozoites stage of E. maxima. Effective stimulation from the EmARM-β antigen to T-bet and Th1 cytokines (IL-2 and IFN-γ) was observed in vivo. After being immunized with rEmARM-β or pVAX1-EmARM-β, significant promotion to the proportion of CD4+ and CD8+ T cells and the level of antigen-specific IgG antibodies in immunized chickens was also observed. Furthermore, vaccination with rEmARM-β antigen or pVAX1-EmARM-β resulted in alleviated weight loss and enteric lesion, reduced oocyst output, and higher anticoccidial index (ACI) in challenged birds. These results indicate that EmARM-β antigen can effectively stimulate the expression of Th1 cytokines and initiate host immune responses, providing moderate protective efficacy against E. maxima. Notably, EmARM-β protein is a promising candidate for developing a novel anticoccidial vaccine.

Differential expression of microRNAs in the caecal content and faeces of broiler chickens experimentally infected with Eimeria

AbstractCoccidiosis caused by Eimeria spp. incurs significant morbidity and mortality in chickens, and is thus of great economic importance. Post-mortem intestinal lesion scoring remains one of the most common means of diagnosis, and therefore alternative, non-invasive methods of diagnosis and monitoring would be highly desirable. Micro-RNAs (miRNAs) have been shown to be stable in faeces of human and animal species with expression altered in gastrointestinal disease. We hypothesised that miRNA is stable in caecal content of chickens, and that differential miRNA expression patterns would be seen in Eimeria infected versus uninfected individuals. Initially, RNA was extracted from Eimeria tenella infected (n = 3; seven days post-infection) and uninfected (n = 3) chicken caecal content to demonstrate miRNA stability. Subsequently, next generation miRNA sequencing was performed on caecal content from E. tenella infected chickens with high (lesion score (LS) 3-4; n = 3) or low (LS1; n = 3) levels of pathology and uninfected controls (n = 3). Comparative analysis identified 19 miRNAs that exhibited significantly altered expression in the caecal content of E. tenella infected chickens versus uninfected chickens (t-test, False Discovery Rate (FDR) < 0.05). Eight of these miRNAs showed significant up-regulation in infection (fold change of 9.8-105, FDR <0.05). Quantitative PCR was performed using separate biological replicates to confirm differential regulation in 8 of these miRNA candidates in caecal and faecal content. This work has identified a panel of miRNA candidates which may be appropriate for use as non-invasive faecal markers of active caecal coccidiosis without the need for culling.

Generation and Characterization of an Anti-diclazuril Monoclonal Antibody and Development of a Diagnostic Enzyme-Linked Immunosorbent Assay for Poultry

An anti-diclazuril monoclonal antibody (mAb) was developed for use in enzyme-linked immunosorbent assay (ELISA)-based detection of diclazuril with high sensitivity and specificity, which can be used to measure anti-coccidial drug residues. The anti-diclazuril mAb had a half-maximal inhibitory concentration of 0.449–0.517 ng/mL. The mAb cross-reactivity with toltrazuril, toltrazuril 18 sulfone, clozaril, monesin, madurmycin, and salinomycin was very minimal (< 0.1%). The detection limit of the ELISA using this mAb was 0.10 ng/mL and the sensitivity was 0.05 ng/mL. A standard curve generated in the range of 0.05–16.2 ng/mL had a linear correlation coefficient value of ≥ 0.99. The average recoveries of diclazuril from chicken and duck samples ranged from 85.0 to 102.5%.Intra- and inter-assay coefficients of variation ranged from 5.9 to 8.5% and 9.2 to 12.6%, respectively. Using the International Immunogenetics Information System^®, the VH domain of the mAb was found to be encoded by an IGHV3 family gene and had the following complementarity determining region (CDR) sequences: GFTFSRY (CDR1), SRGGS (CDR2), and GDDNYAFAY (CDR3). The VL domain was encoded by an IGKV1 family gene and had the following CDR sequences: KSSQSLLNSRTRKNYLA (CDR1), WASTRES (CDR2), and KQSYNLHT (CDR3). This study provides a method to generate anti-diclazuril mAbs and determine their variable region sequences. The diagnostic ELISA developed using this mAb may drive additional studies on the monitoring and detection of food and veterinary drug residues.

Shifting focus from resistance to disease tolerance: A review on hybrid house mice

Parasites have been proposed to modulate the fitness of hybridizing hosts in part based on observations in the European house mouse hybrid zone (HMHZ), a tension zone in which hybrids show reduced fitness. We here review evidence (1) for parasite load differences in hybrid versus parental mice and (2) for health and fitness effects of parasites promoting or preventing introgression and hybridization. The question of relative resistance or susceptibility of hybrids to parasites in the HMHZ has long been controversial. Recent field studies found hybrids to be more resistant than mice from parental subspecies against infections with pinworms and protozoans (Eimeria spp.). We argue that the field studies underlying the contradictory impression of hybrid susceptibility have limitations in sample size, statistical analysis and scope, focusing only on macroparasites. We suggest that weighted evidence from field studies indicate hybrid resistance. Health is a fitness component through which resistance can modulate overall fitness. Resistance, however, should not be extrapolated directly to a fitness effect, as the relationship between resistance and health can be modulated by tolerance. In our own recent work, we found that the relationship between health and resistance (tolerance) differs between infections with the related species E. falciformis and E. ferrisi. Health and tolerance need to be assessed directly and the choice of parasite has made this difficult in previous experimental studies of house mice. We discuss how experimental Eimeria spp. infections in hybrid house mice can address resistance, health and tolerance in conjunction.

DNA-based quantification and counting of transmission stages provides different but complementary parasite load estimates: an example from rodent coccidia (Eimeria)

Background

Counting parasite transmission stages in faeces is the classical measurement to quantify “parasite load”. DNA-based quantifications of parasite intensities from faecal samples are relatively novel and often validated against such counts. When microscopic and molecular quantifications do not correlate, it is unclear whether oocyst counts or DNA-based intensity better reflects biologically meaningful concepts. Here, we investigate this issue using the example of Eimeria ferrisi (Coccidia), an intracellular parasite of house mice (Mus musculus).

Methods

We performed an infection experiment of house mice with E. ferrisi, in which the intensity of infection correlates with increased health impact on the host, measured as temporary weight loss during infection. We recorded the number of parasite transmissive stages (oocysts) per gram of faeces (OPG) and, as a DNA-based measurement, the number of Eimeria genome copies per gram of faeces for 10 days post-infection (dpi). We assessed weight loss relative to the day of experimental infection as a proxy of host health and evaluated whether DNA or oocyst counts are better predictors of host health.

Results

Absolute quantification of Eimeria DNA and oocyst counts showed similar but slightly diverging temporal patterns during 10 dpi. We detected Eimeria DNA earlier than the first appearance of oocysts in faeces. Additionally, Eimeria OPGs within each dpi did not explain parasite DNA intensity. Early dpi were characterized by high DNA intensity with low oocyst counts, while late infections showed the opposite pattern. The intensity of Eimeria DNA was consistently a stronger predictor of either maximal weight loss (1 value per animal during the infection course) or weight loss on each day during the experiment when controlling for between-dpi and between-individual variance.

Conclusions

Eimeria ferrisi oocyst counts correlate weakly with parasite intensity assessed through DNA quantification. DNA is likely partially derived from life-cycle stages other than transmissive oocysts. DNA-based intensities predict health outcomes of infection for the host more robustly than counts of transmissive stages. We conclude that DNA-based quantifications should not necessarily require validation against counts of transmissive stages. Instead, DNA-based load estimates should be evaluated as complementary sources of information with potential specific biological relevance for each host-parasite system.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-05119-0.

Nigericin exerts anticancer effects through inhibition of the SRC/STAT3/BCL-2 in osteosarcoma

The treatment of osteosarcoma has reached a bottleneck period in recent 30 years, there is an urgent need to find new drugs and treatment methods. Nigericin, an antibiotic derived from Streptomyces hygroscopicus, has exerted promising antitumoral effect in various tumors. The anticancer effect of Nigericin in human osteosarcoma has never been reported. In the present study, we explored the anticancer effects of Nigericin in osteosarcoma in vitro and in vivo. Our results showed that nigericin treatment significantly reduced tumor cell proliferation in dose-dependent and time-dependent in human osteosarcoma cells. Nigericin can inhibit cell growth of osteosarcoma cells, in addition to S-phase cycle arrest, the nigericin induces apoptosis. Furthermore, bioinformatics predicted that Nigericin exerts anticancer effects through inhibiting SRC/STAT3 signaling pathway in osteosarcoma. The direct binding between SRC and activator of transcription 3 (STAT3) was confirmed by Western blot. Nigericin can down regulate STAT3 and Bcl-2. In order to further elucidate the inhibitory effect of nigericin on SRC / STAT3 / Bcl-2 signal transduction mechanism, we established human osteosarcoma cancer cells stably expressing STAT3. Western blot confirmed that nigericin exerts anticancer effects on human osteosarcoma cancer cells by directly targeting STAT3. In addition, Nigericin can significantly inhibit tumor migration and invasion. Finally, Nigericin inhibits tumor growth in a mouse osteosarcoma model. The nigericin targeting the SRC/STAT3/BCL-2 signaling pathway may provide new insights into the molecular mechanism of nigericin on cancer cells and suggest its possible clinical application in osteosarcoma.

Quantifying the effect of coccidiosis on broiler performance and infection outcomes in the presence and absence of control methods

A systematic review and meta-analysis was conducted to investigate the role of Eimeria species, dose and inoculation time, on performance and infection outcomes of different broiler strains infected for different study durations. The meta-analysis addressed E. acervulina, E. maxima, E. tenella, and mixed species infections, and involved data from 72 peer-reviewed articles, corresponding to 521 treatments performed on 20,756 broilers. A secondary objective was to investigate the effects of synthetic anticoccidials, ionophores, and vaccination against Eimeria on the above outcomes. Performance during infection was scaled (%) to that of the uninfected birds. Infection reduced scaled ADFI and ADG (P < 0.001) and increased feed conversion ratio (FCR; P < 0.05); there was a significant interaction between dose and species on scaled ADFI and ADG, suggesting that different species affected these variables to different extents (P < 0.001). There was a tendency for an interaction between dose and broiler strain on scaled ADFI (P = 0.079), and a significant interaction between these variables on scaled ADG (P < 0.01). A tendency for an interaction between oocyst dose and Eimeria species (P = 0.067) on maximum number of oocysts excreted was observed. Lesion scores were significantly affected by dose, species, and their interaction (P < 0.05), the latter caused by an increase in the lesion scores during E. maxima and E. tenella infections. Control methods significantly affected scaled ADG and FCR (P < 0.05) and there was an interaction between dose and control methods on ADFI (P < 0.001). Synthetic anticoccidial use improved scaled ADG (P < 0.01), whereas ionophores improved FCR compared with untreated birds (P < 0.01). An interaction between dose and control method on scaled ADFI was caused by the higher ADFI of vaccinated compared to untreated birds, as dose increased. There was a significant effect of control methods on lesion scores (P < 0.01). All findings advance our understanding of the factors that influence the impact of coccidiosis and its controls in broilers.

Chicken Coccidiosis: From the Parasite Lifecycle to Control of the Disease

The poultry industry is one of the main providers of protein for the world's population, but it faces great challenges including coccidiosis, one of the diseases with the most impact on productive performance. Coccidiosis is caused by protozoan parasites of the genus Eimeria, which are a group of monoxenous obligate intracellular parasites. Seven species of this genus can affect chickens (Gallus gallus), each with different pathogenic characteristics and targeting a specific intestinal location. Eimeria alters the function of the intestinal tract, generating deficiencies in the absorption of nutrients and lowering productive performance, leading to economic losses. The objective of this manuscript is to review basic concepts of coccidiosis, the different Eimeria species that infect chickens, their life cycle, and the most sustainable and holistic methods available to control the disease.

Transcriptional dynamics in the protozoan parasite Sarcocystis neurona and mammalian host cells after treatment with a specific inhibitor of apicomplexan mRNA polyadenylation

In recent years, a class of chemical compounds (benzoxaboroles) that are active against a range of parasites has been shown to target mRNA polyadenylation by inhibiting the activity of CPSF73, the endonucleolytic core of the eukaryotic polyadenylation complex. One particular compound, termed AN3661, is active against several apicomplexan parasites that cause disease in humans. In this study, we report that AN3661 is active against an apicomplexan that causes disease in horses and marine mammals (Sarcocystis neurona), with an approximate IC50 value of 14.99 nM. Consistent with the reported mode of action of AN3661 against other apicomplexans, S. neurona mutants resistant to AN3661 had an alteration in CPSF73 that was identical to a mutation previously documented in AN3661-resistant Toxoplasma gondii and Plasmodium falciparum. AN3661 had a wide-ranging effect on poly(A) site choice in S. neurona, with more than half of all expressed genes showing some alteration in mRNA 3' ends. This was accompanied by changes in the relative expression of more than 25% of S. neurona genes and an overall 5-fold reduction of S. neurona transcripts in infected cells. In contrast, AN3661 had no discernible effect on poly(A) site choice or gene expression in the host cells. These transcriptomic studies indicate that AN3661 is exceedingly specific for the parasite CPSF73 protein, and has the potential to augment other therapies for the control of apicomplexan parasites in domestic animals.

Coccidia-Microbiota Interactions and Their Effects on the Host

As a common parasitic disease in animals, coccidiosis substantially affects the health of the host, even in the absence of clinical symptoms and intestinal tract colonization. Gut microbiota is an important part of organisms and is closely related to the parasite and host. Parasitic infections often have adverse effects on the host, and their pathogenic effects are related to the parasite species, parasitic site and host-parasite interactions. Coccidia-microbiota-host interactions represent a complex network in which changes in one link may affect the other two factors. Furthermore, coccidia-microbiota interactions are not well understood and require further research. Here, we discuss the mechanisms by which coccidia interact directly or indirectly with the gut microbiota and the effects on the host. Understanding the mechanisms underlying coccidia-microbiota-host interactions is important to identify new probiotic strategies for the prevention and control of coccidiosis.

Controlling the causative agents of coccidiosis in domestic chickens; an eye on the past and considerations for the future

Coccidiosis is a potentially severe enteritis caused by species of obligate intracellular parasites of the genus Eimeria. These parasites cause significant economic losses to the poultry industry, predominantly due to compromised efficiency of production as well as the cost of control. These losses were recently estimated to cost chicken producers approximately £10.4 billion worldwide annually. High levels of Eimeria infection cause clinical coccidiosis which is a significant threat to poultry welfare, and a pre-disposing contributory factor for necrotic enteritis. Control of Eimeria parasites and coccidiosis is therefore an important endeavour; multiple approaches have been developed and these are often deployed together. This review summarises current trends in strategies for control of Eimeria, focusing on three main areas: good husbandry, chemoprophylaxis and vaccination. There is currently no "perfect solution" and there are advantages and limitations to all existing methods. Therefore, the aim of this review is to present current control strategies and suggest how these may develop in the future.

Protective and immunostimulatory effects of in-feed preparations of an anticoccidial, a probiotic, a vitamin-selenium complex, and Ferulago angulata extract in broiler chickens infected with Eimeria species

Background

Two experiments were conducted to compare the growth-promoting (experiment 1), protective, and immunostimulatory effects (experiment 2) of salinomycin, probiotic, a vitamin-selenium complex, and Ferulago angulata hydroalcoholic extract (FAE) against coccidiosis in broilers. In each experiment, 350 1-day-old broiler chickens were equally divided in 7 groups: uninfected negative control (NC); infected positive control (PC); or PC supplemented with salinomycin (Sal); probiotic (Pro); a combination of vitamin E, vitamin C, and selenium (ECSe); 200 mg/kg of FAE (FAE200); or 400 mg/kg of FAE (FAE400). All these groups (except NC) were challenged via oral gavage with oocysts of mixed Eimeria spp. on d 10 (experiment 1) or d 14 (experiment 2).

Results

In the first trial, all treatments improved growth and feed conversion compared with the PC group, where the best values were noticed in the NC and FAE400 groups throughout the entire experimental period (d 1 to 42). Further, a lower mortality rate (P < 0.05) was observed in the NC, Sal, and FAE400 groups as compared to that in the PC group. In the second trial, intestinal lesion scores and total oocyst numbers were reduced in the Sal, Pro, and FAE400 groups compared to the PC group, albeit all coccidiosis-challenged groups had higher oocyst shedding (P < 0.05) compared to NC group. Immune responses revealed that among challenged birds, those fed diets Pro, ECSE, and FAE400 had significantly higher primary total and secondary total and IgG antibody titers against sheep red blood cells, serum and cecum specific IgG levels, and serum IFN-γ concentration than the PC group.

Conclusions

Considering the results, dietary FAE, especially at high levels of inclusion in broiler diet (400 mg/kg), could beneficially influence growth performance and immune status under coccidiosis challenge, which was comparable to that of probiotic supplement.