EimeriaOocyst Concentrations and Species Composition in Litter from Commercial Broiler Farms During Anticoccidial Drug or LiveEimeriaOocyst Vaccine Control Programs

Epidemiological investigation of coccidiosis and associated risk factors in broiler chickens immunized with live anticoccidial vaccines in China

Coccidiosis is a costly intestinal disease of chickens caused by Eimeria species. This infection is associated with high mortality, reduced feed efficiency, and slowed body weight gain. The diagnosis and control of coccidiosis becomes challenging due to the fact that chickens can be infected by seven different Eimeria species and often occur mixed-species co-infections. Grasping the epidemiology of Eimeria species is crucial to estimate the efficiency of poultry management. This study aimed to explore the distribution of Eimeria species in broiler chickens in China after administering live anticoccidial vaccines. A total of 634 samples were obtained, and the survey results showed that the prevalence of Eimeria was 86.12% (546/634), and the most common species were E. acervulina (65.62%), E. necatrix (50.95%), E. mitis (50.79%), E. tenella (48.42%), and E. praecox (41.80%). Most samples indicated mixed-species infections (an average of 3.29 species per positive sample). Notably, 63.98% of samples contain 3 to 5 Eimeria species within a single fecal sample. The most prevalent combinations were E. acervulina-E. tenella (38.96%) and E. acervulina-E. necatrix (37.22%). Statistical analysis showed that flocks vaccinated with trivalent vaccines were significantly positive for E. necatrix in grower chickens (OR = 3.30, p < 0.05) compared with starter chickens, and tetravalent vaccinated flocks showed that starter chickens demonstrated a higher susceptibility to E. tenella-E. brunetti (OR = 2.03, p < 0.05) and E. acervulina-E. maxima (OR = 2.05, p < 0.05) compared with adult chickens. Geographically, in the case of tetravalent vaccine-immunized flocks, a substantial positive association was observed between E. necatrix infection rates and flocks from eastern (OR = 3.88, p < 0.001), central (OR = 2.65, p = 0.001), and southern China (OR = 3.17, p < 0.001) compared with southwestern China. This study also found a positive association between E. necatrix (OR = 1.64, p < 0.05), E. acervulina (OR = 1.59, p < 0.05), and E. praecox (OR = 1.81, p < 0.05) infection and coccidiosis occurrence compared with non-infected flocks in tetravalent vaccinated flocks. This molecular epidemiological investigation showed a high prevalence of Eimeria species in the field. The emergent species, E. brunetti and E. praecox, might be incorporated into the widely-used live vaccines in the future. These insights could be useful in refining coccidiosis control strategies in the poultry industry.

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.

The Immunoprotective Effect of ROP27 Protein of Eimeria tenella

Eimeria tenella rhoptry protein has the properties of a protective antigen. EtROP27 is a pathogenic gene that is detected via a transcriptome, but its expression pattern, immunogenicity, and potency are unknown. Therefore, a gene segment of EtROP27 was amplified and transplanted into the pET28a prokaryotic vector for the expression of the recombinant protein, and it subsequently purified for the generation of a polyclonal antibody. Then, RT-PCR and Western blotting were performed to understand the expression pattern of EtROP27. Subsequently, animal experiments were conducted to evaluate the immunoprotective effect of the recombinant protein with different immunizing doses (50, 100, and 150 μg). The results showed that the expression of EtROP27 gradually increased with the prolongation of infection time, reaching the highest level at 96 h and then decreasing. Additionally, EtROP27 is a natural antigen of coccidia that can stimulate the body to produce high levels of IgY. As with recombinant protein vaccines, the results of immune protection evaluation tests showed that the average weight gain rates of the immune challenge groups were significantly higher than that of the challenged control group, and their average lesion scores were significantly lower than that of the challenged control group. Furthermore, the oocyst excretion decreased by 81.25%, 86.21%, and 80.01%, and the anticoccidial index was 159.45, 171.47, and 166.75, respectively, for these groups. EtROP27 is a promising antigen gene candidate for the development of a coccidiosis vaccine.

Multilocus Sequence Typing of Eimeria maxima in Commercial Broiler Flocks

About 35% of all broiler flocks in the United States receive an anticoccidial vaccine, but it is not possible to easily differentiate Eimeria vaccine strains from Eimeria field isolates. Being able to do that would allow using vaccines in a more targeted way. The objective of this study was to collect Eimeria maxima isolates from broiler flocks that received anticoccidial feed additives and flocks that had been vaccinated against coccidia and then test them with a multilocus sequencing typing (MLST) scheme developed for this study. Fecal samples were obtained from commercial broiler flocks in Alabama and Tennessee. Oocyst counts in samples tended to be lower in flocks receiving anticoccidial feed additives and higher in vaccinated flocks. Selected samples were screened for presence of E. maxima by quantitative PCR, and Eimeria spp. composition was investigated by next-generation amplicon sequencing (NGAS) in 37 E. maxima positive samples. Other detected Eimeria spp. besides E. maxima were Eimeria acervulina in 35 samples, Eimeria praecox in 23 samples, Eimeria mitis or Eimeria mivati in 17 samples, and Eimeria necatrix or Eimeria tenella in 10 samples. Six partial E. maxima genes (dnaJ domain containing protein, 70-kDa heat shock protein, prolyl endopeptidase, regulator of chromosome condensation domain containing protein, serine carboxypeptidase, and vacuolar proton-translocating ATPase subunit) of 46 samples were sequenced. The MLST scheme was able to differentiate two vaccines from each other. Three of 17 samples from vaccinated flocks differed from the vaccine used in the flock, while 16 of 29 samples from unvaccinated flocks differed from the vaccine. However, there was also a large number of low-quality, ambiguous chromatograms and negative PCRs for the selected genes. If and when more advanced, possibly next-generation sequencing-based methods will be developed, the genes should be considered as targets.

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.

Polymerase Chain Reaction Directed to Eimeria ITS1 rDNA or a Single-Copy Orthologue Corroborates Standard Micro-oocyst Analysis of Intestinal Tissue from Chickens Infected with E. acervulina, E. maxima, or E. tenella

The purpose of this study was to compare micro-oocyst counts of Eimeria to PCR analysis of intestinal DNA from smears of duodenum, jejunum/ileum, and cecum of chickens infected with Eimeria acervulina, Eimeria maxima, or Eimeria tenella oocysts. Broiler chicks were infected in triplicate with various doses of E. acervulina, E. maxima, or E. tenella oocysts and were necropsied 5-6 days later to recover duodenal, jejunal, or cecal tissue for micro-oocyst count and for DNA recovery. Micro-oocyst counts were done independently by three individuals. Micro-oocyst counts and PCR directed to ITS1 rDNA or to a single-copy orthologue (SCO 5995) displayed a linear relationship with oocyst dose for each Eimeria species. A strong correlation was found between mean micro-oocyst counts and both PCR assays for E. acervulina (r = 0.78-0.94), E. maxima (r = 0.79-0.91), and E. tenella (r = 0.85-0.96). There was good agreement between ITS1 and SCO 5995 PCR assays: E. acervulina (r = 0.92), E. maxima (r = 0.79), and E. tenella (r = 0.93). However, only ITS1 PCR analysis corroborated micro-oocyst counts of Eimeria oocyst DNA recovered from Eimeria-infected broiler chickens submitted to a poultry diagnostic laboratory. These findings suggest that ITS1 PCR or SCO PCR can validate traditional micro-oocyst counts used in quantifying Eimeria infection in chickens. Additional studies may provide a method for estimating the relative abundance of each Eimeria species in a natural infection.

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.

Phylogenetic analysis of Eimeria tenella isolated from the litter of different chicken farms in Mymensingh, Bangladesh

Background

Eimeria tenella is the most pathogenic intracellular protozoan parasite of seven Eimeria species causing chicken coccidiosis around the world. This species is particularly responsible for caecal coccidiosis leading to serious morbidity–mortality and financial loss in poultry production.

Methods

The present study explored the genetic diversity of E. tenella. Litter slurry was collected from 18 broiler farms located in Mymensingh district, Bangladesh. Litter samples were processed for oocyst isolation–identification using parasitological techniques followed by genomic DNA extraction from sporulated oocysts. For molecular analysis, the internaltranscribedspacer1 gene of E. tenella was amplified using species‐specific primers and sequenced. After editing and alignment, 263 bp sequences were used for analysis.

Results

Genetic analysis showed seven distinct genotypes and detected six single nucleotide polymorphisms among the 18 E. tenella isolates. The nucleotide and genotype diversity were 0.00507 and 0.8235, respectively. A phylogenetic tree was constructed with 66 sequences (seven studied genotypes and 59 reference sequences from GenBank database). The neighbour‐joining tree represented that the studied E. tenella isolates were grouped with reference E. tenella isolates with strong nodal support (100%) and the nucleotide sequences of E. tenella, E. necatrix, E. acervulina, E. brunetti, E. maxima, E. mitis and E. praecox formed separate clusters without any geographical boundaries.

Conclusions

This is the first study on the genetic analysis of E. tenella from Mymensingh district, Bangladesh. These findings will provide baseline data on the species conformation and genetic variations of E. tenella. Further extensive investigation will be needed to reveal the population genetic structure of this parasite and thus will facilitate the planning of effective control strategies.

Nutritional interventions to support broiler chickens during Eimeria infection

Different combinations of gut health-promoting dietary interventions were tested to support broilers during different stages of Eimeria infection. One-day-old male Ross 308 broilers (n = 720) were randomly assigned to one of 6 dietary treatments, with 6 pens per treatment and 20 birds per pen, for 35 d. At 7 d of age (d7), all birds were inoculated with 1000, 100, and 500 sporulated oocysts of E. acervulina, E. maxima, and E. tenella, respectively. A 4-phase feeding schedule was provided. The dietary treatments (TRT) 1 to 4 included the basal diet supplemented with multispecies probiotics from d0 to 9 and coated butyrate and threonine from d28 to 35 but received four different combinations of prebiotics and phytochemicals from d9 to 18 and d18 to 28. The basal diet for the positive control (PC, TRT5) included diclazuril as a anticoccidial. The negative control (NC, TRT6) contained no anticoccidial. Performance was assessed for each feeding phase, and oocyst output, Eimeria lesion scores, cecal weight, litter quality, and footpad lesions were assessed at d14, d22, d28, and d35. Body weight gain (BWG) and feed intake (FI) were not affected by dietary treatment. PC broilers had the best feed conversion ratio (FCR) of all treatments from d0 to 35 (P < 0.001). None of the dietary treatments resulted in better litter quality or reduced footpad lesions compared to the PC. Moreover, the PC was most effective in reducing oocyst output and lesion scores compared to all other treatments. However, broilers that received the multispecies probiotics (d0 to 9), saponins (d9 to 18), saponins, artemisin, and curcumin (d18 to 28), and coated butyrate and threonine (d28 to 35) had the best FCR (P < 0.001) and lowest oocyst output and lesion scores compared to other dietary treatments. This study suggests that although the tested compounds did not perform as well as the anticoccidial, when applied in the proper feeding period, they may support bird resilience during coccidiosis infection.

DETECTION OF COCCIDIA OOCYSTS IN LITTER AND FECES OF BROILERS IN A FLOOR PEN TRIAL

Counting oocysts in feces or litter is 1 method to monitor infection levels with Eimeria spp. in chickens after experimental infection or in commercial flocks. Counts of oocysts shed in the feces are thought to follow a typical pattern, with clear peaks representing infection cycles while oocyst counts in litter are representative for at least 2 wk before they begin to deteriorate. The objective of the study was to compare oocyst counts in fresh feces and litter of broilers kept in floor pens with fresh pine shavings as litter material for 42 days. The birds were spray-vaccinated against coccidia in the hatchery. Every 2 to 3 days, 7 pens were sampled by collecting fresh feces and litter from at least 3 locations per pen. Oocysts were counted using a McMaster chamber (Vetslides, Park City, Utah). There were significant differences between pens in oocyst counts in feces as well as in litter, and there were no obvious shedding patterns. Overall, the geometric mean of oocyst counts on day 8 and later was 1,300 oocysts per gram (opg) in feces and 2,700 opg in litter. The variability was lower in litter samples, and the number of pens required to find significant differences between groups in a hypothetical experiment was unrealistically high on most days. Investigating individual fecal samples showed large differences within the pens in addition to the differences between the pens.

Prevalence of Eimeria sp. in Broiler Poultry Houses with Positive and Negative Pressure Ventilation Systems in Southern Brazil

Coccidiosis is an enteric disease caused by protozoa of the Eimeria genus and is of great economic relevance in industrial aviculture. The objective of this work was to determine the prevalence of Eimeria sp. in broiler poultry houses with positive (System 1) and negative (System 2) pressure ventilation and assess the associated factors. A transversal study was conducted using 8 random broiler chickens from 64 houses (n = 512) and macroscopic and histologic evaluation of the intestines, as well as PCR for Eimeria sp. The prevalence of Eimeria sp. was 90.6% (95% confidence interval [CI]: 97.8-83.5), with 93.8% (95% CI: 100-85.4) in System 1 and 87.5% (95% CI: 99.0-76.0) in System 2. The most prevalent species was Eimeria acervulina, and the most common combination was Eimeria acervulina, Eimeria maxima, and Eimeria tenella. System 2 and the negative Eimeria subgroup showed the best results for feed conversion and daily weight gain. By evaluating litter treatment, we found that quicklime reduced the risk of presence of Eimeria maxima and Eimeria tenella. In conclusion, Eimeria sp. had a high prevalence in both systems, with a predominance of mixed infections. System 2 and negative flocks showed the best zootechnical results.

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

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

Correlation Between Clostridium perfringens Alpha- and NetB-Toxin and Chick Mortality in Commercial Broiler Farms During Different Anticoccidial Control Programs

The purpose of the present study was to determine whether a correlation existed between chick mortality and the presence of Clostridium perfringens alpha-toxin and NetB-toxin genes (cpa and netB) in C. perfringens recovered from litter in commercial broiler houses. Because coccidiosis predisposes chickens to necrotic enteritis, the concentration of Eimeria oocysts in these samples was measured, and the numbers were used in similar correlation analyses. Litter samples were collected at 0, 2, and 4 wk growout from six broiler farms (18 houses total) during an anticoccidial drug (ACD) control program and from nine broiler farms (23 houses total) during an Eimeria vaccine (VAC) control program. Of these, litter samples were collected from five farms during both ACD and VAC programs. The litter samples were processed for Eimeria oocyst and C. perfringens spore enumerations by standard parasitologic and microbiologic techniques. DNA was also extracted for C. perfringens DNA for PCR detection of genes coding for alpha- and NetB-toxin. A general trend during the ACD programs was a transient decrease in both Eimeria maxima and non-E. maxima (Eamipt) numbers at 2 wk growout. The pattern was slightly different during VAC with E. maxima and Eamipt levels increasing over time. Average concentrations of C. perfringens in litter were highest at 2 wk (∼105-106 spores/g) during ACD and at placement during VAC (∼105-106 spores/g). During the ACD program, a strong correlation was observed between 0 and 3-wk chick mortality and the presence at placement (0 wk) of netB (r = 0.42-0.48) or cpa (r = 0.55-0.67). A very strong correlation was observed in 0-5-wk chick mortality and the presence of netB at 4 wk growout (0.73-0.95). During a VAC program, a strong correlation was only observed between the presence of netB at placement and 0-1-wk chick mortality (r = 0.67).

Restoration of the sensitivity of Eimeria acervulina to anticoccidial drugs in the chicken following use of a live coccidiosis vaccine

The efficacy of the anticoccidial drugs amprolium, clopidol, diclazuril, monensin, monensin + nicarbazin, narasin, narasin + nicarbazin, and salinomycin against field isolates of Eimeria acervulina obtained from a commercial broiler enterprise before and after immunization with a coccidiosis vaccine was investigated. Evaluated by weight gain, feed conversion, and lesion score following challenge, the isolate obtained before vaccination was resistant to all the drugs tested. By contrast, after vaccination the isolate was sensitive to all drugs evaluated by weight gain, and to most drugs judged by feed conversion and lesion score. It is concluded that vaccination had resulted in the restoration of sensitivity to these drugs.

A survey of coccidia and nematodes in pastured poultry in the state of Georgia

The aim of this study was to evaluate and quantify the parasitological challenge in pastured poultry production in the state of Georgia. Over the course of one year, fecal samples from six turkey flocks, ten broiler flocks and 13 layer flocks were collected on a pastured farm in two-week intervals to determine counts of Eimeria oocysts and nematode eggs. Average coccidia counts were 10,198 oocysts per gram of feces (OPG) in broiler flocks, 1,470 OPG in layer flocks and 695 OPG in turkey flocks. The means in broiler and turkey flocks were higher at their first week on pasture. Counts in broilers and layers were significantly higher in spring than in winter and summer. Coccidia counts in broilers were lower than published numbers in conventionally reared poultry, indicating the rotation system of the pastures might effectively reduce the infection pressure. Next-generation sequencing of PCR products showed the presence of most described Eimeria spp. in broilers, layers, and turkeys. In addition, Operational Taxonomic Units (OTUs) x, y and z were found. The frequency of species was similar for broilers and layers, with the exception that Eimeria praecox and OTU z were more common in layers. In layer flocks, the average count of roundworm eggs per gram of feces (EPG) was 509 EPG with 80% of the samples being positive. The mean counts had no clear pattern related to age. There was an increase of EPG with the increase of temperatures during spring and summer with the peak at mid-fall. Worm eggs from laying hens were identified as A. galli. The seasonal differences suggest that higher temperatures might result in an increase of egg survival and sporulation in the environment.

Effects of administration of an in ovo coccidiosis vaccine at different embryonic ages on vaccine cycling and performance of broiler chickens,. Poult Sci 2020;100:100914. [PMID: 33518328 PMCID: PMC7936202 DOI: 10.1016/j.psj.2020.11.078]

Use of a live coccidiosis vaccine has become an increasingly common method to control coccidiosis, especially in antibiotic-free broiler production. The Inovocox EM1 vaccine (EM1) is recommended for the vaccination of embryonated broiler hatching eggs between 18.0 and 19.0 d of incubation (doi). This allows for earlier acquisition of immunity to wild-type coccidia. However, it is unclear whether the difference in embryo age at the time of in ovo injection can influence the effect of the vaccine during grow-out as well as if the growth performance of broiler chickens is affected. Therefore, the objective of the study was to evaluate the effects of 2 injection ages (18.5 and 19.0 doi) and 3 injection types (noninjected, diluent, and vaccine) in a 3 × 2 factorial design, consisting of 10 replicates per treatment (60 treatment-replicate groups). There was a significant effect of injection age on BW at 0, 14, and 35 d after hatch, with a difference in the BW of birds belonging to the 18.5 and 19.0 doi groups up to day 35 after hatch. There was a significant effect of injection type on BW gain, feed intake, and FCR between 0 and 28 d after hatch. Between 0 and 35 d, FCR was lower in the vaccine-injected group in comparison with the noninjected and diluent control groups. Furthermore, total intestine coccidia and lesion indices were higher in the vaccine-18.5 treatment group in comparison with the diluent-18.5 treatment group at 28 d. In conclusion, hatchling weight was affected by injection age, and this subsequently affected growth performance. Furthermore, intestinal coccidia cycling peaked at 28 d, resulting in a reduction in growth performance through 28 d and subsequent compensatory growth by 35 d. There was no significant difference in coccidiosis cycling between the vaccine-18.5 and vaccine-19.0 doi treatment combination groups.

Concurrent use of saponins and live coccidiosis vaccines: the influence of a quillaja and yucca combination on anticoccidial effects and performance results of coccidia-vaccinated broilers

A series of studies was conducted to determine the effects of a quillaja and yucca (saponin) combination (QY) product on postvaccination oocyst production, development of coccidial immunity, and final bird performance of broilers administered live coccidiosis vaccines. In all, 3 groups of tests were carried out. Study 1 evaluated the effects of QY (0 and 250 ppm) on oocyst per gram of feces (OPG) following vaccination at day-of-age; OPG were measured from 5 to 12 d postvaccination. Study 2 determined the effects of QY (250 ppm) in the presence of 3 commercial coccidiosis vaccines in floor pens. OPG were measured weekly for birds receiving each vaccine and for each corresponding vaccine group fed QY. To determine whether QY influenced the development of coccidial immunity induced by the 3 vaccines, 5 birds were removed from each pen at 28 d and challenged with pathogenic levels of Eimeria spp. At 6 d post challenge, lesion scores were used to evaluate the effects of QY on immune protection provided by each vaccine. In addition, comparisons of final bird performance were made between birds given each vaccine and their corresponding vaccinates fed QY. Study 3 comprised a meta-analysis of 15 floor pen trials in which 21- and 42-d body weight, feed conversions, and total mortality were compared between coccidiosis-vaccinated broilers and similarly vaccinated broilers fed QY (250 ppm). Results of these experiments indicated that feeding QY to vaccinated broilers did not significantly affect OPG from days 5 through 12 postvaccination (P > 0.05). For each vaccine tested in study 2, OPG values were the highest at 14 and 21 d postvaccination. QY significantly reduced OPG at 14 d postvaccination for 2 of the vaccines tested, and produced a similar effect in 1 vaccine at 21 d postvaccination. The remaining vaccine was not affected by QY in the postvaccination OPG results. Despite these changes in OPG, significant differences in lesion scores following the Eimeria challenge were not observed for any vaccinated groups receiving QY. Irrespective of the vaccine, both interim and final feed conversion values were significantly improved when QY was fed (P < 0.01). Similarly, results of a 15-trial meta-analysis indicated that QY-fed vaccinated broilers had higher body weights, improved feed conversions, and lower mortality than their vaccinated controls. Results show that while QY may induce changes in OPG following vaccination, coccidia-vaccinated broilers fed QY develop immunity equivalent to that of controls and show significant improvements in performance and mortality.

Monitoring coccidia in commercial broiler chicken flocks in Ontario: comparing oocyst cycling patterns in flocks using anticoccidial medications or live vaccination

Coccidiosis, the parasitic disease caused by Eimeria spp., is controlled during broiler chicken production through the inclusion of in-feed anticoccidial medications. Live-coccidiosis vaccination has become an increasingly common alternative to these medications. Monitoring infections with Eimeria spp. in flocks can be accomplished through determining the concentration of oocysts excreted in the fecal material (i.e., oocysts per gram; OPG). The purpose of our study was to sample commercial Ontario broiler chicken flocks at various times of the year to determine weekly OPG counts for flocks that use either an in-feed anticoccidial medication or a live-coccidiosis vaccine. Weekly sampling of 95 flocks from placement to market permitted documentation of oocyst cycling patterns typical of conventional and antibiotic-free flocks, and variation of these patterns in summer and winter. Medicated flocks had higher and later peak oocyst shedding compared with vaccinated flocks. Flocks reared in the summer peaked in oocyst shedding earlier than flocks reared in the winter. Despite what appears to be poorer coccidiosis control in the medicated flocks, the performance data were similar for these flocks compared with vaccinated flocks. This is the first study describing typical patterns of parasite shedding in Ontarian commercial broiler chicken flocks; these data will provide a baseline of expected Eimeria spp. infections in Canadian broiler chicken flocks to ensure optimal coccidiosis prevention.

Impacts of antibiotic reduction strategies on zootechnical performances, health control, and Eimeria spp. excretion compared with conventional antibiotic programs in commercial broiler chicken flocks

Increasing efforts have been made in recent years to reduce antimicrobial use in animal production. The objective of this prospective study was to evaluate, in commercial broiler chicken farms, 2 antibiotic reduction strategies that eliminated the use of antibiotics important for human medicine, in comparison with the conventional use of antibiotics. On 7 broiler chicken farms, a house was allocated to the antibiotic reduction treatments for 6 consecutive flocks, whereas a similar house on the same premises was assigned to the conventional use of antibiotics (CONV) for 6 consecutive flocks. The antibiotic reduction strategies consisted of continuous in-feed use of ionophores (TX1) and continuous in-feed use of ionophores with butyric acid (TX2). In the 84 flocks, zootechnical performance was recorded, lesion scoring at 21 and 28 D of age was performed, and fecal samples were recovered during grow out for Eimeria spp. oocysts counts. There was no statistical difference between TX1, TX2, and CONV for weights at slaughter, feed conversion ratios, average daily gains, age at slaughter, total mortalities, and condemnations. The probability of identifying oocysts in the fecal samples significantly increased with the age of the flock, but there was no significant treatment effect between 7 and 16 D of age. At 19 D of age, the probability of a sample containing oocysts was higher in TX1 than in CONV, but TX2 was not statistically different from TX1 and CONV. Predicted oocysts per gram in CONV flocks were significantly lower between 22 and 34 D of age than in TX1 and TX2 flocks, whereas there were no significant differences between TX1 and TX2 for all ages. Lesion scoring of the gastrointestinal system showed no differences for coccidiosis scores between TX1, TX2, and CONV. No lesions of necrotic enteritis were observed. In conclusion, it was possible to adequately control intestinal diseases and maintain zootechnical performances by relying exclusively on ionophores, when compared with broiler chicken flocks using standard shuttle programs with antibiotic growth promoters.

Effect of different floatation solutions on E. tenella oocyst purification and optimization of centrifugation conditions for improved recovery of oocysts and sporocysts

Saturated salt floatation method is widely used for coccidian oocyst purification. However, the repeated procedures and inefficient oocysts recovery rate are a continuous challenge. This study aimed to investigate the best suitable floatation solution, along with optimal centrifugation speed and time for Eimeria tenella (E. tenella) oocyst and sporocyst purification. Different floatation solutions i-e, saturated salt, Sheather's sugar and sodium hypochlorite (NaClO) at 20-60% concentrations were used to purify oocyst. It was found that about 96.99% oocysts (8609×g for 10 min) were recovered under these conditions without any effect on the viability of sporocysts. The recovery rate of oocysts using 50% NaClO (V/V) was significantly higher than 35% saturated salt flotation solution (P < 0.05). The optimal method for purification of oocysts based our experimentation was centrifugation at 8609×g for 3 min using 50% NaClO floatation solution, and the optimized centrifugation conditions for improved recovery of sporocysts (about 99.3%) were at 2152×g for 5 min. The present study provided a better method for the coccidian oocyst purification, which could be successfully adopted as a better alternative to existing techniques commonly used for investigations/research pertaining to coccidia.

Efficacy of recombinant N- and C-terminal derivative of EmIMP1 against E. maxima infection in chickens

1. Immune mapped protein-1 (IMP1) of E. maxima has been identified as a vaccine antigen candidate for E. maxima infection. 2. In the current study, the N- and C-terminal derivative of EmIMP1 were expressed in E. coli and administered to chickens. The antibody response, cell-mediated immune (CMI) response and the protective efficacy of the protein vaccines against E. maxima challenge were evaluated. 3. The results showed that C-terminal derivative of EmIMP1 vaccination could increase weight gain, reduce enteric lesions, and decrease faecal oocysts shedding. Moreover, the C-terminal derivative of EmIMP1 caused reasonable improvement in serum antibodies and the numbers of IFN-γ producing peripheral blood mononuclear cells (PBMC), as compared to the control group. 4. This study demonstrated that the C-terminal derivative of EmIMP1 could be used as a potent immunogenic candidate in the development of subunit vaccines against E. maxima infection.

Transgenic Eimeria parasite: A potential control strategy for chicken coccidiosis

Poultry industry has been very instrumental in curtailing malnutrition and poverty and as such contributing to economic growth. However, production loss in poultry industry due to parasitic disease such as coccidiosis has become a global challenge. Chicken coccidiosis is an enteric disease that is associated with morbidity and mortality. The control of this parasite through anticoccidial live vaccines and drugs has been very successful though with some limitations such as the cost of production of live vaccines, and drugs resistance which is a public health concern. The discovery of Eimeria vaccine antigens such as Apical membrane antigens (AMA)-1 and Immune mapped protein (IMP)-1 have introduced the use of recombinant vaccines as alternative control measures against chicken coccidiosis. Although some protections have been reported among recombinant vaccines, improving their protective efficacy has triggered the search for a novel and efficient delivery vehicle. Transgenic Eimeria, which is constructed either through stable or transient transfection is currently being explored as novel delivery vehicle of Eimeria vaccine antigens. Due to partial protections reported in chickens vaccinated with transgenic Eimeria lines expressing different Eimeria antigens, improving protective efficacy becomes imperative. Recent trends in the design of transgenic Eimeria for potential application in the control of chicken coccidiosis are summarized in this review. We conclude that, with improved protective efficacy using multiple vaccine antigens, transgenic Eimeria parasite could fill the gap in the control of chicken coccidiosis as an efficient anticoccidial vaccine.

Viable Eimeria oocysts in poultry house litter at the time of chick placement

The purpose of this study was to determine if Eimeria oocysts recovered from litter at the time of chick placement in commercial broiler houses contained oocysts that were infectious for chickens. Over 100 litter samples were collected from 30 poultry farms representing a total of 60 different broiler houses with 9 houses sampled more than once over 1.5 yr. The samples were collected just before the placement of newly hatched chicks and after an anticoccidial drug (ACD) or Eimeria vaccine (VAC) program, and processed for counting oocysts followed by Eimeria species determination using ITS1 PCR. Broiler chicks were inoculated with recovered Eimeria oocysts to determine if the litter oocysts were viable and capable of causing patent infection. At placement, E. maxima (Emax) oocysts were detected in 70 of 75 houses after ACD program and 46 of 47 houses after VAC program. Eimeria acervulina, E. praecox, and/or E. tenella (Eapt) were detected in 75 of 75 houses after ACD program and 47 of 47 houses after VAC program. Viability testing revealed that 33.0% of broiler houses contained viable Emax oocysts, while 46.9% contained viable Eapt oocysts. During VAC programs, the concentration of Emax oocysts at placement and the total number of Emax oocysts shed by chickens in viability studies showed a very strong correlation (r = 0.83). Likewise, during ACD programs, the concentration of Eapt oocysts at placement and the total number of Eapt oocysts shed by chickens in the viability study showed a strong correlation (r = 0.62). In general, Eimeria oocyst levels at placement and number of viable oocysts shed by chickens in the viability study were similar among houses on the same farm. However, the number of Eimeria oocysts shed in the viability studies was considerably less than expected based on the number of oocysts given. These data suggest that nearly 100% of all poultry houses contain Emax and Eapt oocysts at placement with 30 to 50% of the houses containing viable Eimeria oocysts, thus possibly representing a source of the protozoa to newly hatched chicks.

A review of Eimeria antigen identification for the development of novel anticoccidial vaccines

Coccidiosis is a major poultry disease which compromises animal welfare and costs the global chicken industry a huge economic loss. As a result, research entailing coccidial control measures is crucial. Coccidiosis is caused by Eimeria parasites that are highly immunogenic. Consequently, a low dosage of the Eimeria parasite supplied by a vaccine will enable the host organism to develop an innate immune response towards the pathogen. The production of traditional live anticoccidial vaccines is limited by their low reproductive index and high production costs, among other factors. Recombinant vaccines overcome these limitations by eliciting undesired contaminants and prevent the reversal of toxoids back to their original toxigenic form. Recombinant vaccines are produced using defined Eimeria antigens and harmless adjuvants. Thus, studies regarding the identification of potent novel Eimeria antigens which stimulate both cell-mediated and humoral immune responses in chickens are essential. Although the prevalence and risk posed by Eimeria have been well established, there is a dearth of information on genetic and antigenic diversity within the field. Therefore, this paper discusses the potential and efficiency of recombinant vaccines as an anticoccidial control measure. Novel protective Eimeria antigens and their antigenic diversity for the production of cheap, easily accessible recombinant vaccines are also reviewed.

Laboratory Growth and Genetic Manipulation of Eimeria tenella

Eimeria is a genus of apicomplexan parasites that contains a large number of species, most of which are absolutely host-specific. Seven species have been recognized to infect chickens. Infection of susceptible chickens results in an intestinal disease called coccidiosis, characterized by mucoid or hemorrhagic enteritis, which is associated with impaired feed conversion or mortality in severe cases. Intensive farming practices have increased the significance of coccidiosis since parasite transmission is favored by high-density housing of large numbers of susceptible chickens. Routine chemoprophylaxis and/or vaccination with live parasite vaccines provides effective control of Eimeria, although the emergence of drug resistance and the relative cost and production capacity of current vaccine lines can prove limiting. As pressure to reduce drug use in livestock production intensifies, novel vaccination strategies are needed. Development of effective protocols supporting genetic complementation of Eimeria species has until recently been hampered by their inability to replicate efficiently in vitro. Now, the availability of such protocols has raised the prospect of generating transgenic parasite lines that function as vaccine vectors to express and deliver heterologous antigens. For example, this technology has the potential to streamline the production of live anticoccidial vaccines through the generation of parasite lines that co-express immunoprotective antigens derived from multiple Eimeria species. In this paper we describe detailed protocols for genetic manipulation, laboratory growth, and in vivo propagation of Eimeria tenella parasites, which will encourage future work from other researchers to expand biological understanding of Eimeria through reverse genetics. © 2019 by John Wiley & Sons, Inc.

Protective immunity against Eimeria maxima induced by vaccines of Em14-3-3 antigen

Eimeria maxima 14-3-3 (Em14-3-3) open reading frame (ORF) which consisted of 861 bp encoding a protein of 286 amino acids was successfully amplified and sequenced. Subsequently, the Em14-3-3 ORF was subcloned into pET-32a (+) and pVAX1, respectively. RT-PCR and immunoblot analyses confirmed that the target gene was successfully transcribed and expressed in vivo. Immunofluorescence analysis showed that Em14-3-3 was expressed in both the sporozoites and merozoites. The animal experiments demonstrated that both rEm14-3-3 and pVAX1-14-3-3 could clearly alleviate jejunum lesions and body weight loss. The Em14-3-3 vaccines could increase oocyst decrease ratio, as well as produce an anticoccidial index of more than 165. The percentages of CD4⁺ in both the Em14-3-3 immunized groups were much higher, when compared with those of PBS, pET32a (+), and pVAX1 controls (P < 0.05). Similarly, the anti-Em14-3-3 antibody titers of both rEm14-3-3 and pVAX1-14-3-3 immunized groups showed higher levels compared with those of PBS, pET32a (+), and pVAX1 controls (P < 0.05). The IFN-γ and tumor growth factor-β (TGF-β) levels showed significant increments in the rEm14-3-3 and pVAX1-14-3-3 immunized groups, when compared with those in the negative controls (P < 0.05). These results demonstrated that Em14-3-3 could be used as a promising antigen candidate for developing vaccines against E. maxima.