Anticoccidial vaccines for broiler chickens: pathways to success

The effect of sodium bisulfate and coccidiostat on intestinal lesions and growth performance of Eimeria spp.-challenged broilers

Coccidiosis is a high-prevalence disease that annually entails huge costs for the poultry industry. Control of coccidiosis in poultry production is based on the use of coccidiostats and vaccines. However, along with the problem of drug resistance, there is a concern about food safety and drug residues in poultry products. The objective of this study was to evaluate the effect of sodium bisulfate (SBS) in comparison with monensin (M) and their combination (SBSM) effects on controlling coccidiosis in broilers. In a randomized design, 300 chickens (Ross 308) were divided into 5 treatments and 4 replications (15 birds per replicate). All birds, except the negative control (NC), were orally inoculated with 4 Eimeria species on 14 D of age. Treatments included were as follows: NC, an unsupplemented basal diet, nonchallenged; positive control, a basal diet unsupplemented, challenged with Eimeria spp; a basal diet supplemented with 5 g/kg of SBS; a basal diet supplemented with 1 g/kg of M; and a basal diet supplemented with 5 g/kg SBS and 1 g/kg M (SBSM). Oocyst shedding per gram (OPG) of the faecal sample from each experimental unit was counted on 5 to 14 D after inoculation. Two chicks from each experimental unit were euthanized to investigate intestinal lesions on day 5 after inoculation. The NC birds showed the highest BW gain and the lowest feed conversion ratio. The birds in the SBSM group had improved feed consumption compared with the M group in the prechallenge period (P < 0.05). All supplemented treatments resulted in a significant decrease in OPG. The M and SBSM treatments showed more efficacy than the SBS group (P < 0.05) in reducing OPG. There was a significant reduction in cecal lesions owing to supplementation with SBS, but the effect of SBS in the upper part of the intestine was lower than the M and SBSM groups (P < 0.05). Based on the results of this study, SBS has protective effects against coccidiosis in ceca, and the combination of M and SBS (SBSM) did not show any further improvement effect compared with M alone on the control of coccidiosis.

Efficacy of dietary supplemental insoluble fibrous materials in ameliorating adverse effects of coccidial challenge in broiler chickens

The current experiment was designed to examine effects of dietary supplemental sunflower hulls (SH) and rice hulls (RH) on growth performance, carcass traits, intestinal morphology, lesion score and oocyst shedding in broiler chickens exposed to coccidial challenge. A total of 540 broiler chickens (Ross 308) were assigned to six dietary treatments based on a factorial arrangement (2 × 3) across 1-14, 14-28 and 28-42-d periods. Experimental treatments consisted of broiler chickens without or with coccidial challenge each offered with three different diets: a basal diet or basal diet supplemented with either RH or SH at 40 g/kg diet, respectively. Infection with Eimeria impaired daily weight gain (DWG) and feed conversion ratio (FCR) of broiler chickens during growing period (p < 0.05) while supplementation of SH or RH reduced the adverse effect of coccidiosis so that birds had similar DWG to those fed the basal diet without infection. However, only dietary SH improved the FCR of broilers challenged with coccidiosis. Regardless of coccidial challenge, dietary access to insoluble fibre improved performance of broilers across the growing period (p < 0.05); however, this effect was not observed during the entire rearing period. Relative weights of liver and pancreas were increased in birds subjected to coccidial challenge on d 21 of age (p < 0.05). Moreover, relative weights of the intestinal segments were enhanced (p < 0.05). Furthermore, gizzard weights were higher in birds receiving diets added with fibre (p < 0.05). Infection with coccidiosis decreased villus height and villus height to crypt depth ratio in duodenum of broilers which received the basal diet compared with those fed the same feed without coccidial challenge (p < 0.05). However, supplemental SH could decrease the negative effect of infection on the noted intestinal morphometric attributes. Similarly, a marked reduction was observed for lesion score and faecal oocyst excretion of challenged broilers fed on dietary supplemental fibre (p < 0.05). In conclusion, supplementation of insoluble fibre could ameliorate negative effects of coccidial challenge on DWG of broiler chickens and inclusion of SH in diet of birds exposed to Eimeria infection could be recommended.

Efficacy of probiotic Enterococcus faecium in combination with diclazuril against coccidiosis in experimentally infected broilers

AIMS

The study was conducted to investigate the combination of a probiotic strain of Enterococcus faecium and diclazuril to control coccidiosis in broilers.

METHODS AND RESULTS

A total of 240 one-day-old female broiler chicks were divided into eight groups (30 chicks per group): prophylactic groups (G1, G2 and G3) and therapeutic groups (G4, G5 and G6) and two control groups (untreated infected, G7 and untreated uninfected, G8 controls). In the prophylactic approach, diclazuril alone (G1), probiotic alone (G2) or a mixture of both probiotic and diclazuril (G3) was orally administered to the chicks via drinking water 10 days prior to the infection. However, in the therapeutic approach, G4, G5 and G6 birds were administered diclazuril alone, probiotic alone and diclazuril+probiotic mix, respectively, in drinking water for five consecutive days after the appearance of clinical signs of coccidiosis. Birds of both approaches and G7 were experimentally infected with 25 × 10³ Eimeria-sporulated oocysts. Chicks in G3 showed the highest weight gain, the lowest lesion score, a low oocyst count and mortality rate among the challenged groups. Moderate lesion scores and oocyst counts were observed in chickens administered probiotics prophylactically. In the therapeutic approach, broilers in G6 but not G5 displayed a decreased mortality rate and lesion score in comparison to those in G7 and G8. However, the result of the probiotic-treated group was not significantly different from that in the untreated infected control group.

CONCLUSION

The probiotic supplementation as a prophylactic approach can decrease the adverse effects of eimerian infection. In addition, the probiotic and diclazuril mix achieved a considerable improvement in the growth performance. Therefore, probiotic plus diclazuril combination achieved a synergistic effect.

SIGNIFICANCE AND IMPACT OF THE STUDY

Investigation into the synergism/antagonism between a probiotic and diclazuril as anticoccidial agent and the difference in the timing of administration.

Genome-wide analysis of differentially expressed profiles of mRNAs, lncRNAs and circRNAs in chickens during Eimeria necatrix infection

BACKGROUND

Eimeria necatrix, the most highly pathogenic coccidian in chicken small intestines, can cause high morbidity and mortality in susceptible birds and devastating economic losses in poultry production, but the underlying molecular mechanisms in interaction between chicken and E. necatrix are not entirely revealed. Accumulating evidence shows that the long-non-coding RNAs (lncRNAs) and circular RNAs (circRNAs) are key regulators in various infectious diseases. However, the expression profiles and roles of these two non-coding RNAs (ncRNAs) during E. necatrix infection are still unclear.

METHODS

The expression profiles of mRNAs, lncRNAs and circRNAs in mid-segments of chicken small intestines at 108 h post-infection (pi) with E. necatrix were analyzed by using the RNA-seq technique.

RESULTS

After strict filtering of raw data, we putatively identified 49,183 mRNAs, 818 lncRNAs and 4153 circRNAs. The obtained lncRNAs were classified into four types, including 228 (27.87%) intergenic, 67 (8.19%) intronic, 166 (20.29%) anti-sense and 357 (43.64%) sense-overlapping lncRNAs; of these, 571 were found to be novel. Five types were also predicted for putative circRNAs, including 180 exonic, 54 intronic, 113 antisense, 109 intergenic and 3697 sense-overlapping circRNAs. Eimeria necatrix infection significantly altered the expression of 1543 mRNAs (707 upregulated and 836 downregulated), 95 lncRNAs (49 upregulated and 46 downregulated) and 13 circRNAs (9 upregulated and 4 downregulated). Target predictions revealed that 38 aberrantly expressed lncRNAs would cis-regulate 73 mRNAs, and 1453 mRNAs could be trans-regulated by 87 differentially regulated lncRNAs. Additionally, 109 potential sponging miRNAs were also identified for 9 circRNAs. GO and KEGG enrichment analysis of target mRNAs for lncRNAs, and sponging miRNA targets and source genes for circRNAs identified associations of both lncRNAs and circRNAs with host immune defense and pathogenesis during E. necatrix infection.

CONCLUSIONS

To the best of our knowledge, the present study provides the first genome-wide analysis of mRNAs, lncRNAs and circRNAs in chicken small intestines infected with E. necatrix. The obtained data will offer novel clues for exploring the interaction mechanisms between chickens and Eimeria spp.

Dissection of the cecal microbial community in chickens after Eimeria tenella infection

Background

Eimeria spp. are responsible for chicken coccidiosis which is the most important enteric protozoan disease resulting in tremendous economic losses in the poultry industry. Understanding the interaction between the avian cecal microbiota and coccidia is of interest in the development of alternative treatments that do not rely on chemotherapeutics and do not lead to drug resistance.

Methods

We utilized 16S rRNA gene sequencing to detect the dynamics of the cecal microbial community in AA broilers challenged with Eimeria tenella. Histopathological analysis of the cecum was also conducted.

Results

We found that microbial shifts occur during the infection. Lactobacillus, Faecalibacterium, Ruminococcaceae UCG-013, Romboutsia and Shuttleworthia decreased in abundance. However, the opportunistic pathogens Enterococcus and Streptococcus increased in abundance over time in response to the infection.

Conclusions

Eimeria tenella disrupts the integrity of the cecal microbiota and could promote the establishment and growth of potentially pathogenic bacteria. Defining bacterial populations affected by coccidial infection might help identify bacterial markers for intestinal disease as well as populations or species that could be beneficial in maintaining and restoring gut homeostasis during and after infection with E. tenella.

Effects of stage of broiler embryo development on coccidiosis vaccine injection accuracy, and subsequent oocyst localization and hatchling quality

Control of coccidiosis in broiler chickens continues to pose challenges to commercial poultry producers, especially in an era of increased consumer demand for antibiotic-free broiler production. As a result, coccidiosis vaccines are now commonly used in rotation programs to achieve effective coccidiosis control. Inovocox EM1 vaccine (EM1) is a coccidiosis vaccine that allows for earlier immune acquisition through oocyst cycling, which reduces the effects of wild-type coccidia. The EM1 vaccine is administered to embryonated broiler hatching eggs between 18 and 19 D of incubation (doi). In the U.S., commercial broiler hatcheries vaccinate embryonated eggs at either 18.5 or 19 doi. However, it is unclear whether a difference in embryo age at the time of in ovo injection can impact the actual site of vaccine delivery. In addition, it is unclear where oocysts eventually become localized within the embryo following the in ovo injection of EM1. Therefore, the objective of this study was to determine the effects of stage of embryonic development on the actual deposition site of the EM1 vaccine oocysts when they are in ovo injected and to subsequently investigate the movement and eventual location of EM1 oocysts after in ovo injection. Because all eggs were injected at the same time, a 12-h difference in set time was a means to derive 18.5 and 19.0 incubation age of injection (IAN) treatments. The experimental design was a 3 injection treatment (noninjected, diluent-injected, and vaccine-injected) × 2 IAN factorial. There was a significant main effect of IAN on site of vaccine oocysts delivery, and subsequent hatching chick quality. Qualitative histological evaluation revealed the oral uptake of vaccine oocysts through the amnion, with their subsequent presence in the gizzard and intestinal lumen by 24 to 36 h postinjection. In conclusion, physiological development influenced the site of injection, and oocysts imbibed along with the amniotic fluid in late stage broiler embryos are subsequently transported to the gastrointestinal tract.

The influence of indigestible protein on the performance and meat quality of broilers vaccinated for coccidiosis

High dietary protein and the use of poorly digested protein sources have been suggested to negatively impact broiler health, possibly because of protein fermentation in the distal intestinal tract. The effect of dietary protein levels with low or high indigestible protein fractions (LIP or HIP) on male and female broiler performance were evaluated. The trial was completely randomized with a 2 × 3 × 2 factorial arrangement, where gender, dietary protein levels (24, 26, and 28%), and dietary protein digestible fractions were the main factors. Ross 308 male (1944) and female (2232) were allocated to 72 pens with 54 males or 62 females per pen. Six grower diets 24-LIP, 24-HIP, 26-LIP, 26-HIP, 28-LIP, and 28-HIP were fed from 0 to 32 D of age. Birds were vaccinated with Coccivac-B52 on day 5, and feed intake and BW were recorded on 0, 12, 22, and 32 D. On day 32, 24 birds per treatment were processed for meat yield. Males were heavier than females at all post-hatch ages and the LIP birds were heavier than their HIP counterparts on 32 D. On day 22, birds fed 24 and 26% CP were heavier than those fed 28% CP. Birds fed the 28-LIP diet consumed less total feed than their 24 and 26-LIP equivalents. Birds fed 24% CP had the highest total feed to gain ratio, whereas LIP fed birds had a lower total feed to gain than those fed HIP diets. LIP diets resulted in higher total mortality than the HIP diets. Carcass yield was higher for females than males, increased with CP level, and was lower in HIP than LIP birds. An interaction between CP level and protein digestibility resulted in the 26 and 28-LIP having higher breast yield than all other diets. In conclusion, broiler growth performance and meat yield were affected by dietary indigestible protein alone or in combination with gender and dietary CP level.

Effects of pre-starter and starter diets varying in amino acid density given to broiler chickens that received coccidiosis vaccination at hatch1

An experiment was conducted to evaluate broilers vaccinated against coccidiosis fed combinations of pre-starter and starter diets varying in digestible amino acid (dAA) density from 1 to 19 d of age on subsequent growth performance and meat yield. A total of 1,800 Yield Plus Ross × Ross 708 male broilers were allocated to 60 floor pens and assigned to 1 of the 6 treatments. Four pre-starter diets varying in dAA density [1.15% dLys, 1.25% dLys, 1.35% dLys, and Positive Control (1.15% dLys + Diclazuril)] were fed until 9 d of age. Then, 3 starter diets varying in dAA density [1.15% dLys, 1.25% dLys, and PC (1.15% dLys + Diclazuril)] were given from 10 to 19 d of age. All diets were formulated to similar dAA ratios to dLys; hence, resulting in increasing amino acid (AA) density among the dietary treatments. Birds were given common grower and finisher diets for the remainder of the experiment. At 19, 27, and 40 d of age, broilers that received the 1.35% and 1.25% dLys density pre-starter and 1.25% dLys density starter diets had increased BW gain (P ≤ 0.006) compared with broilers fed the 1.15% dLys density diets. Broilers that received the 1.15% dLys density pre-starter diet had a lower cumulative BW gain (P = 0.007) than those fed the 1.35% and 1.25% dLys density pre-starter diets. Broilers that received the 1.35% and 1.25% dLys density pre-starter and 1.25% dLys density starter diets had the heaviest (P ≤ 0.008) total breast weights. Increasing the pre-starter dAA density enhanced (P ≤ 0.03) total breast weight by 28 g (1.25% dLys density) and 51 g (1.35% dLys density). Results from this study indicated that increasing dAA density from 1 to 19 d of age enabled a 1 to 19 d dAA intake increase of 4.8 g, which enhanced cumulative growth and meat yield of broilers vaccinated against coccidiosis.

A blend of fatty acids, organic acids, and phytochemicals induced changes in intestinal morphology and inflammatory gene expression in coccidiosis-vaccinated broiler chickens

Feed additives that promote gastrointestinal health may complement coccidiosis vaccination programs in antibiotic-free broiler production systems. This study examined the effects of a commercial feed additive blend (FA) on intestinal histomorphology and inflammatory biomarkers in vaccinated Ross 708 cockerels (N = 2,160). The study was a randomized complete block design (12 blocks) with 3 dietary treatments: CON (negative control), AGP (positive control: 55 ppm of bacitracin methylene disalicylate), and FA (1.5 kg/MT in starter; 1.0 kg/MT in grower; and 0.5 kg/MT in finisher). Birds were reared on re-used litter and fed a 3-phase feeding program (starter, 0 to 14 D; grower, 15 to 28 D; finisher, 29 to 36 D). One master batch of basal feed for each feeding phase was prepared and final experimental diets were manufactured by mixing the basal feed with the respective test ingredient prior to pelleting. Growth measurements, including pen body weight and feed intakes, and fresh fecal samples were taken throughout the study. On day 20, samples of intestinal tissue were collected from a subset of birds (n = 72, 1 block) for histomorphology and mRNA expression of tight junction and inflammatory genes. In the duodenum, the ratio of villi length to crypt depth was significantly lower in FA (and AGP) fed birds than those consuming the CON diet. Relative mRNA expressions of iNOS, IFN_Ɣ, and claudin-1 were upregulated in the jejunum of FA and AGP treatment groups compared to those in the CON group; the response in the FA was of lesser magnitude than AGP. Together, these results demonstrated that the FA treatment altered the microstructure of the duodenum and affected the expression of inflammatory genes in the jejunum. The timing of these changes coincided with peak oocyte shedding in feces and an observed reduction in feed efficiency in all dietary treatment groups.

Utility of Feed Enzymes and Yeast Derivatives in Ameliorating Deleterious Effects of Coccidiosis on Intestinal Health and Function in Broiler Chickens

Coccidiosis induced necrotic lesions impair digestive capacity and barrier function in concurrence with increased risks for secondary bacterial infections. The industry has been successful in controlling coccidiosis with anticoccidials and vaccination. However, concerns over Eimeria species resistant to anticoccidials, gaps in vaccination and restriction on antibiotics is stimulating research and application of alternative and/or complimentary strategies for coccidiosis control. The aim of this paper is to appraise literature on the utility of feed enzymes and yeast derivatives in modulating coccidiosis. Feed enzymes can complement endogenous enzymes (protease, amylase, and lipase) that may become insufficient in coccidiosis afflicted birds. Coccidiosis in the upper small intestine creates conditions that enhances efficacy of phytase and there are reports indicating supplemental phytase can mitigate the negative impact of coccidiosis on bone quality. Increase in intestinal short chain fatty acids due supplemental fiber degrading enzymes has been linked with reduced survivability of Eimeria. There is evidence whole yeast (live or dead) and derivatives can modulate coccidiosis. Immunomudulation properties of the yeast derivatives have been shown to enhance cellular and humoral immunity in Eimeria challenge models which is critical for effectiveness of coccidial vaccination. Moreover, yeast nucleotides have been shown to be beneficial in stimulating healing of intestinal mucosal surface. Other novel work has shown that certain yeast cells can produce derivatives with anticoccidial compounds effective in attenuating oocysts shedding. Yeast cell surface has also been shown to be an effective oral Eimeria vaccine delivery vehicle. Overall, while further refinement research is warranted to address inconsistencies in responses and commercial application, there is evidence feed enzymes and yeast derivatives could complement strategies for maintaining intestinal function to bolster growth performance in broilers compromised with coccidiosis. However, broilers receive diets containing several feed additives with distinct mode of actions and yet there is dearth of empirical data on the expected responses.Future evaluations should consider combinations of additives to document animal responses and potential synergies.

Effects of dietary amino acid density and feed allocation during the starter period on 41 days of age growth performance and processing characteristics of broiler chickens given coccidiosis vaccination at hatch1

A study was conducted to determine if increasing digestible (dig) amino acid (AA) density or feed allocation of starter diets fed to broilers receiving coccidiosis vaccination can ameliorate poor cumulative growth performance and reduce meat yield. A total of 1,600 Yield Plus Ross × Ross 708 male broilers were assigned to a 2 × 3 factorial arrangement of dig AA density [moderate (1.15% dig Lys) and high (1.25% dig Lys)] and feed allotment (0.45, 0.73, and 1.00 kg/bird) with 2 positive control treatments during the starter period. Diets were formulated to essential AA ratios relative to dig Lys. Vaccinated birds received a 1x dosage of Coccivac- B52 prior to placement, whereas non-vaccinated birds in the positive control groups were fed diets containing diclazuril. Following consumption of the starter diets, birds were provided common grower and finisher diets. Broilers fed the high AA density diet during the starter period had higher cumulative BW gain and lower cumulative feed conversion ratios (P < 0.05) than those fed the moderate AA density diet. Broilers fed the high AA density diet had heavier (P ≤ 0.005) carcass and total breast weights than birds fed the moderate AA density diet. Broilers fed a starter allotment of 1.00 kg/bird produced heavier carcass weights (P ≤ 0.006) than did birds provided lower allotments. Additionally, broilers fed the high AA density diet had a greater percentage of 0 scores (P = 0.005) for the upper intestinal region during scoring. Results from this study indicated that feeding the high AA density diet at higher feed allotments during the starter period resulted in increased AA intake, which supported the bird through the vaccine challenge and enhanced the cumulative growth and meat yield.

The influence of indigestible protein on broiler digestive tract morphology and caecal protein fermentation metabolites

Indigestible dietary protein fermentation products have been suggested to negatively influence broiler performance due to their impact on health and digestive tract morphology. This study evaluated the digestive tract morphology and caecal protein fermentation metabolites of broiler fed 3 dietary protein levels (24%, 26% and 28%) with low or high indigestible protein (LIP, HIP). Two completely randomized 3 × 2 factorial trials were conducted with protein level (PL) and indigestible protein (IDP) as the main factors. In both trials, birds received six diets (24-LIP, 24-HIP, 26-LIP, 26-HIP, 28-LIP and 28 HIP) formulated with no medication. On day 5, trial 1 birds were vaccinated with Coccivac-B52, while trial 2 received no vaccine. Tissue and caecal samples were collected and caecal contents analysed for fermentation metabolites. Differences were considered significant when p ≤ .05. The LIP treatment caecal content in trial 1 at 14 days had greater histamine, agmatine and cadaverine levels, while HIP diets resulted in increased serotonin, tryptamine and spermidine. Histamine, serotonin and tryptamine at day 28 were not affected by IDP, and ammonia was not affected by treatments at day 14 or day 28. At day 14, HIP birds had lower total short-chain fatty acids, higher caecal pH and heavier pancreas, proventriculus, gizzard, jejunum and ileum weights. The same effects of IDP found in trial 1 were observed for histamine, agmatine, cadaverine, serotonin, tryptamine and spermidine at day 21 in trial 2. Trial 2 had a PL-by-IDP interaction influencing tyramine, spermidine (28-LIP > 24-LIP) and spermine with values increasing with PL for LIP diets and remaining constant for HIP diets. An interaction between PL and IDP was found for ammonia level and was similar to interactions for biogenic amines. In conclusion, dietary PL and IDP influence broiler caecal protein fermentation metabolites and those effects varied with coccidiosis vaccination and rearing environment.

Effects of encapsulated cinnamaldehyde and citral on the performance and cecal microbiota of broilers vaccinated or not vaccinated against coccidiosis

This study investigated the effects of encapsulated cinnamaldehyde (CIN) and citral (CIT) alone or in combination (CIN + CIT) on the growth performance and cecal microbiota of nonvaccinated broilers and broilers vaccinated against coccidiosis. Vaccinated (1,600) and nonvaccinated (1,600) 0-day-old male Cobb500 broilers were randomly allocated to 5 treatments: basal diet (control) and basal diet supplemented with bacitracin (BAC, 55 ppm), CIN (100 ppm), CIT (100 ppm), and CIN (100 ppm) + CIT (100 ppm). In general, body weight (BW) and feed conversion ratio were significantly improved in birds treated with BAC, CIN, CIT, and CIN + CIT (P < 0.05) but were all decreased in vaccinated birds compared with nonvaccinated birds (P < 0.05). Significant interactions (P < 0.05) between vaccination and treatments for average daily gain during the periods of starter (day 0–9) and BW on day 10 were noted. Broilers receiving vaccines (P < 0.01) or feed supplemented with BAC, CIN, CIT, or CIN + CIT (P < 0.01) showed reductions in mortality rate from day 0 to 28. The incidences of minor coccidiosis were higher (P < 0.05) in vaccinated birds than in nonvaccinated birds. Diet supplementation with BAC or tested encapsulated essential oils showed comparable effects on the coccidiosis incidences. Similar to BAC, CIN and its combination with CIT reduced both incidence and severity of necrotic enteritis (P < 0.05). No treatment effects were observed on the cecal microbiota at the phyla level. At the genus level, significant differences between vaccination and treatment groups were observed for 5 (Lactobacillus, Ruminococcus, Faecalibacterium, Enterococcus, and Clostridium) of 40 detected genera (P < 0.05). The genus Lactobacillus was more abundant in broilers fed with CIT, while Clostridium and Enterococcus were less abundant in broilers fed with CIN, CIT, or CIN + CIT in both the vaccinated and nonvaccinated groups. Results from this study suggested that CIN alone or in combination with CIT in feed could improve chicken growth performance to the level comparable with BAC and alter cecal microbiota composition.

Molecular characterization of surface antigen 10 of Eimeria tenella

Chicken coccidiosis is caused by the apicomplexan parasite Eimeria spp. At present, drug resistance of Eimeria is common because of the indiscriminate use of anticoccidial drugs. The gene encoding surface antigen 10 of Eimeria tenella (EtSAG10) is differentially expressed between drug-resistant and drug-sensitive strains. RNA-seq analysis indicated that this gene was downregulated in strains resistant to maduramicin and diclazuril compared to susceptible strains. EtSAG10 DNA sequence alignment revealed that they contained one and ten mutations in MRR and DZR, compared with DS, respectively. A full-length EtSAG10 cDNA was successfully cloned and expressed, and the polyclonal antibody was prepared. The transcription and translation levels of EtSAG10 were analyzed by quantitative real-time PCR (qPCR) and Western blotting. The localization of EtSAG10 in Spz, Mrz, and parasites in the first asexual stage was determined by indirect immunofluorescence. The potential association of EtSAG10 with sporozoite invasion of host cells was assessed by invasion inhibition assays. The results showed that EtSAG10 had a predicted transmembrane domain at the C-terminal end and a predicted signal peptide at the N-terminal end. EtSAG10 was downregulated in drug-resistant strains, which is consistent with the RNA-seq results. The EtSAG10 protein was localized to the parasite surface and parasitophorous vacuole membrane. This protein was shown to play a role in the infection of chicken intestine by sporozoites.

Stable transfection of Eimeria necatrix through nucleofection of second generation merozoites

Eimeria spp., the causative agents of coccidiosis, are the most common protozoan pathogens of chickens. Infection with these parasites can result in poor development or death of animals leading to a devastating economic impact on poultry production. The establishment of transfection protocols for genetic manipulation of Eimeria species and stable expression of genes would help advance the biology of these parasites as well as establish these organisms as novel vaccine delivery vehicles. Here, we report the selection of the first stable transgenic E. necatrix population, EnHA1, consitutively expressing the EYFP reporter following transfection of the 2^nd generation merozoites with a linear DNA fragment harboring the EYFP reporter gene, the HA1 gene from the avian influenza virus H9N2 and the TgDHFR-TS selectable marker, which confers resistance to pyrimethamine. Transfected merozoites were inoculated into chickens via the cloacal route, and feces from 18 h to 72 h post inoculation were collected and subjected to subsequent serial passages, FACS sorting and pyrimethamine selection. A gradual increase in the number of EYFP-expressing sporulated oocysts was noticed with more than 90% EYFP + oocysts obtained after five passages. Immunofluorescence assay confirmed successful expression of the HA1 antigen in the EnHA1 population. The ability to genetically manipulate E. necatrix merozoites and express heterologous genes in this parasite will pave the way for possible use of this organism as a vaccine-delivery vehicle.

Eimeria tenella oocysts attenuated by low energy electron irradiation (LEEI) induce protection against challenge infection in chickens

In vitro and in vivo studies were performed to assess whether Eimeria tenella (E. tenella) oocysts, exposed to low energy electron irradiation (LEEI), might be considered potential vaccine candidates against cecal coccidiosis. Sporulated oocysts were exposed to LEEI of 0.1 kGy to 10.0 kGy. Reproduction inhibition assays (RIA) were performed in MDBK cells to assess infectivity of sporozoites excysted from irradiated and non-irradiated oocysts. LEEI of 0.1 kGy or 0.5 kGy resulted in 73.2% and 86.5% inhibition of in vitro reproduction (%I_RIA), respectively. Groups of 12 one day old (D1) chicken were orally inoculated with Paracox®-8 (G1), 2.0 × 10³ non-irradiated oocysts (G2) or 1.0 × 10⁴ irradiated oocysts exposed to LEEI of 0.1 kGy (G3, G4) or 0.5 kGy (G5). Chicken of groups G1, G2, G4 and G5 were challenged 3 weeks later (D21) by a single inoculation of 7.5 × 10⁴ non-attenuated oocysts of the same strain while G3 remained unchallenged. All chickens were subject to necropsy 7 days after challenge (D28) to estimate lesion scores (LS) and oocyst index (OI). A positive control (PC, non-vaccinated, challenged) and a negative control (NC, non-vaccinated, non-challenged) were kept in parallel. Chicken of group G5 had similar weight gain as the Paracox®-8 group (G1) after challenge and higher weight gains as compared to the other vaccinated groups. Feed conversion ratio (FCR) did not differ between chickens inoculated with oocysts irradiated with 0.5 kGy (G5) and negative control (NC) before challenge (1.25-1.52). After challenge FCR was 1.99 (G5) to 2.23 (G4) in the vaccinated chicken compared to 1.76 in group NC. LS and OI were significantly lower in all vaccinated groups as compared to group PC. Progeny oocysts collected from the feces of chickens following vaccination with irradiated oocysts exhibited lower in vitro infectivity/reproduction in MDBK cells with %I_RIA of 89.7% and 82.4% for progeny of oocysts irradiated with 0.5 kGy and 0.1 kGy, respectively, suggesting hereditary attenuation by LEEI treatment. Seroconversion was demonstrated by ELISA before challenge (D21) in all vaccinated groups, however, chicken inoculated with irradiated oocysts displayed higher antibody levels than those inoculated with precocious oocysts (G1). In Western blot analysis chicken vaccinated with virulent (G2) or 0.1 kGy-irradiated E. tenella oocysts (G3, G4) showed more protein bands compared to G5 (0.5 kGy). We conclude that LEEI could be a promising technology for production of attenuated oocyst vaccines.

A review of the financial impact of production diseases in poultry production systems

While the academic literature widely asserts that production diseases have a significant financial impact on poultry production, these claims are rarely supported by empirical evidence. There is a risk, therefore, that the information needs of poultry producers regarding the costs associated with particular diseases are not being adequately met. A systematic literature review of poultry production diseases was undertaken, first, to scope the availability of studies that estimate the financial impacts of production diseases on poultry systems and, second, on the basis of these studies, estimates were generated of the magnitude of these impacts. Nine production diseases, selected by a panel of stakeholders as being economically important in the EU, were examined. The review found that the poultry disease literature has primarily an epidemiological focus, with very few publications providing estimates of the financial impacts of diseases. However, some publications have quantified the physical impacts of production diseases and control interventions, for example, using measures such as output volumes, mortality rates and bacterial counts. Using these data in standard financial models, partial financial analyses were possible for some poultry production diseases. Coccidiosis and clostridiosis were found to be the most common production diseases in broiler flocks, with salpingoperitonitis being the most common in layers. While the financial impact of untreated diseases varied, most uncontrolled diseases were estimated to make flocks loss-making. However, in all cases, interventions were available that signficantly reduced these losses. The review reinforces the concern that the available academic literature is not providing sufficient information for poultry producers to decide on financially optimal disease-prevention and treatment measures.

Protective immunity induced by Eimeria common antigen 14-3-3 against Eimeria tenella, Eimeria acervulina and Eimeria maxima

Background

Avian coccidiosis is often caused by co-infection with several species of Eimeria worldwide. Developing a multivalent vaccine with an antigen common to multiple Eimeria species is a promising strategy for controlling clinical common co-infection of Eimeria. In the previous study, 14–3-3 was identified as one of the immunogenic common antigen in E. tenella, E. acervulina and E. maxima. The aim of the present study was to evaluate the immunogenicity and protective efficacy of Ea14–3-3 in the form of DNA vaccine against infection with three species of Eimeria both individually and simultaneously.

Results

After vaccination with pVAX-Ea14–3-3, the Ea14–3-3 gene was transcribed and expressed in the injected muscles. Vaccination with pVAX-Ea14–3-3 significantly increased the proportion of CD4⁺ and CD8⁺ T lymphocytes and produced a strong IgY response in immunized chickens. Similarly, pVAX-Ea14–3-3 stimulated the chicken’s splenocytes to produce high levels of Th1-type (IFN-γ, IL-2) and Th2-type (IL-4) cytokines. The vaccine-induced immune response was responsible to increase weight gain, decreased the oocyst output, and alleviated enteric lesions significantly in immunized chickens as compared to control group, in addition to induce moderate anti-coccidial index (ACI).

Conclusion

These results indicate that Ea14–3-3 is highly immunogenic and capable to induce significant immune responses. Furthermore, Ea14–3-3 antigen can provide effective protection against infection with Eimeria tenella, Eimeria acervulina, Eimeria maxima both individually and in combination with three Eimeria species. Significant outcomes of our study provide an effective candidate antigen for developing a multivalent Eimeria vaccine against mixed infection with various Eimeria species under natural conditions.

Electronic supplementary material

The online version of this article (10.1186/s12917-018-1665-z) contains supplementary material, which is available to authorized users.

Effects of tannic acid extract on performance and intestinal health of broiler chickens following coccidiosis vaccination and/or a mixed-species Eimeria challenge

Two experiments were conducted to investigate the effects of tannic acid extract (TAE) formulations on the performance and intestinal health of male Cobb × Cobb 500 broilers exposed to coccidiosis. In the first experiment, 320 broiler chicks were randomly assigned to 5 treatments with 8 replicates. Treatments included non-medicated, uninfected (NC); non-medicated, infected (PC); salinomycin (SAL, 66 mg/kg); tannic acid (TA, 0.5 g/kg) and TAE (TAE, 0.5 g/kg). On d 14, all groups (except NC) were orally inoculated with Eimeria acervulina, E. maxima and E. tenella oocysts. Intestinal lesion scores, fecal oocyst counts (OPG) and performance were evaluated on d 20. The PC had greater lesions and higher FCR than infected, supplemented groups. Only TAE reduced OPG compared to PC (P < 0.05). In the second experiment, 3,000 broiler chicks were vaccinated on day of hatch with live coccidial oocysts, then randomly assigned to 5 treatments with 15 replicates. Treatments included non-medicated (CNT); salinomycin (SAL, 66 mg/kg); robenidine (ROB, 33 mg/kg); TAE (0.5 g/kg) and TAE with Bacillus coagulans (TAE+BC, 0.5 g/kg). On d 29, a subset of pens (n = 20) were challenged with a mixed Eimeria spp. oral inoculum; performance, lesions and OPG were evaluated on d 35. An immune challenge was created in half the pens by issuing broilers feed without supplementation materials during the challenge. For the non-challenged pens (n = 55), performance was measured up to d 49. Performance of non-challenged, vaccinated-CNT birds was improved with all treatments at d 21 and d 49. Among the challenged birds, withdrawal of SAL or ROB resulted in FCR similar to the challenged CNT group (P > 0.05), whereas withdrawal of TAE or TAE+BC maintained improved FCR compared to challenged-CNT birds (P < 0.05). These findings indicate supplementation of TAE and TAE+BC with coccidiosis vaccination can be considered as a potential alternative strategy to address coccidiosis in broiler chickens.

Evaluation of autofluorescent Eimeria maxima oocysts as a potential indicator of non-viability when enumerating oocysts

Aging, poor oxygenation, or improper storage temperature can lead to variable Eimeria oocyst viability, which is not readily assessed microscopically. Under fluorescent microscopy, some aged Eimeria maxima (EM) oocysts were strongly autofluorescent (AF) within the oocystoplasm and sporocysts, whereas others were distinctly non-fluorescent, leading to the hypothesis that non-viable oocysts may be detectible using this simple approach. Using accelerated aging conditions at 45°C, two experiments were conducted to evaluate variable percentages of autofluorescent EM oocysts on body weight gain (BWG), lesion scores (LS), and total oocyst shedding (OS) per bird. Through oral gavage, EM oocysts were administered on d10, whereas LS and BWG were determined d5 post-inoculation. Experiment 1 groups consisted of non-challenged controls (n = 15), or 25,000 EM exhibiting 12.8% (n = 14), 61.1% (n = 10), or 93.3% (n = 10) autofluorescence. BWG in 12.8% AF group was lower (P = 0.054) than non-challenged control. LS were higher (P < 0.05) in 61.1% and 12.8% AF groups as compared to non-challenged control and 93.3% AF groups. Experiment 2 groups consisted of non-challenged controls (LS n = 20/BWG n = 40), or 22,500 EM exhibiting 7% AF (LS n = 20/BWG n = 40), 80.6% AF (LS n = 19/BWG n = 39), or 99% AF (LS n = 19/BWG n = 39). BWG in 7% AF group was lower (P < 0.05) than non-challenged control and 99% AF groups. LS were higher (P < 0.05) in 80.6% and 7% AF groups as compared to non-challenged control and 99% AF groups. OS from d5-8 post-inoculation was determined for each of five replicates per group (n = 20/group; n = 4/replicate), with higher (P < 0.05) OS in 80.6% and 7% AF groups than in non-challenged control or 99% AF groups. Taken together, data indicate lower LS, higher BWG, and reduced OS with higher %AF oocysts, consistent with the hypothesis of lowered viable challenge with this EM isolate.

Evaluation of a coccidia vaccine using spray and gel applications

Coccidiosis is an economically significant disease of poultry caused by species of Eimeria, a parasitic protozoan. Disease can result in poor feed conversion, reduced weight gain, and can lead to the development of necrotic enteritis. For prevention of coccidiosis, poultry are commonly vaccinated with a live, sporulated oocysts mass applied with a vaccination cabinet in the hatchery. Traditionally, coccidia vaccines have been applied by coarse spray in a water based diluent, however, new technology using gel diluents has entered the US market. Gel diluents can have variable viscosities and are “dropped” onto chicks with an applicator bar. It is thought that gel droplets remain intact on the birds for longer than water based droplets, allowing more time for preening and ingestion of oocysts. In this experiment, the efficacy of a commercial coccidia vaccine applied with a water based diluent, a more viscous gel diluent, and a less viscous gel diluent was compared. Fecal samples were collected at multiple time points post-vaccination to quantify vaccine oocyst shedding. Shedding in the first cycle (days 5 to 8 post-vaccination) was related to the number of oocysts received from each application method, where the groups receiving higher doses shed more oocysts. However, a decrease in shedding was seen for the more viscous gel group in the second cycle (days 12 to 15 post-vaccination). Chickens were challenged with Eimeria maxima oocysts and 7 days post-challenge body weight gains and gross and microscopic lesions were recorded to evaluate protection levels for the different vaccine applications. All vaccinated groups appeared to be protected based on body weight gain and lesion scoring. The results of this project indicate that all vaccine applications are effective at protecting against Eimeria maxima challenge when using a proper dose of vaccine that allows for repeated oocyst cycling in the litter post-vaccination.

Transgenic Eimeria tenella Expressing Profilin of Eimeria maxima Elicits Enhanced Protective Immunity and Alters Gut Microbiome of Chickens

Coccidiosis is one of the most serious diseases of livestock and birds in the world. Vaccination with live-parasite anticoccidial vaccines with genetic manipulation improving the immunogenicity of vaccine strains would be the best means for controlling coccidiosis in breeder and layer stocks, even in fast-growing broilers. Profilin from apicomplexan parasites is the first molecularly defined ligand for Toll-like receptor 11 (TLR11) and TLR12 in mice and is a potential molecular adjuvant. Here, we constructed a transgenic Eimeria tenella line (Et-EmPro) expressing the profilin of Eimeria maxima, the most immunogenic species of chicken coccidia, and evaluated the adjuvant effects of EmPro on the immunogenicity of E. tenella We found that immunization with the transgenic Eimeria parasites, compared with the wild type, elicited greater parasite antigen-specific cell-mediated immunity, characterized by increased numbers of interferon gamma (IFN-γ)-secreting lymphocytes. The transgenic parasite also induced better protective immunity against E. tenella challenge than the wild type. In addition, the diversity of the fecal microbiome of the birds immunized with the transgenic parasite differed from that of the microbiome of the wild-type-immunized birds, indicating interactions of Eimeria with the gut microbiome of chickens. Our results showing enhanced immunogenicity of E. tenella by use of EmPro as a molecular adjuvant derived from the most immunogenic affinis species represent a large step forward in the development of the next generation of coccidiosis vaccines using Eimeria as a vaccine platform expressing molecular adjuvants and potentially other pathogen antigens against not only coccidiosis but also other infectious diseases.

Comparative analysis of egg adapted vaccines and salinomycin against coccidiosis in chicks

Avian coccidiosis is an intestinal protozoan parasitic disease of genus Eimeria. Wide use of anticoccidial drugs has resulted in development of drug resistant strains. Current study is based upon the development of egg adapted vaccines; gametocytes, formalin inactivated and formalin inactivated sonicated gametocytes against coccidiosis. Day old chicks (n = 90) were divided into six groups (A-F) with triplicate. On 5th day of age, three groups were orally given developed vaccines (0.2 ml) while on 21st day groups (A-E) were challenged orally with mixed Eimeria spp (60-70,000 oocysts/chick). The comparative effect of vaccines and drug salinomycin was evaluated on basis of different parameters. Blood, liver and caecal tissues were collected on 5th, 7th and 15th day post infection for indirect hemagglutination test, biochemical analysis and histopathology. Significantly higher body weight gain, feed consumption, mild bloody diarrhea with lowest oocyst count and survival rate of 100% was recorded for gametocytes vaccinated group (P < 0.05). Indirect hemagglutination test showed maximum antibodies titer (IgG) in gametocytes vaccinated group. Present investigation revealed that gametocyte vaccines was significantly effective in control of coccidiosis by inducing strong protection in immune chicks contained high level of antibodies that resisted heavy dose of challenge as compared to anticoccidial drug salinomycin.

Vaccines as alternatives to antibiotics for food producing animals. Part 1: challenges and needs

Vaccines and other alternative products can help minimize the need for antibiotics by preventing and controlling infectious diseases in animal populations, and are central to the future success of animal agriculture. To assess scientific advancements related to alternatives to antibiotics and provide actionable strategies to support their development, the United States Department of Agriculture, with support from the World Organisation for Animal Health, organized the second International Symposium on Alternatives to Antibiotics. It focused on six key areas: vaccines; microbial-derived products; non-nutritive phytochemicals; immune-related products; chemicals, enzymes, and innovative drugs; and regulatory pathways to enable the development and licensure of alternatives to antibiotics. This article, part of a two-part series, synthesizes and expands on the expert panel discussions regarding opportunities, challenges and needs for the development of vaccines that may reduce the need for use of antibiotics in animals; new approaches and potential solutions will be discussed in part 2 of this series. Vaccines are widely used to prevent infections in food animals. Various studies have demonstrated that their animal agricultural use can lead to significant reductions in antibiotic consumption, making them promising alternatives to antibiotics. To be widely used in food producing animals, vaccines have to be safe, effective, easy to use, and cost-effective. Many current vaccines fall short in one or more of these respects. Scientific advancements may allow many of these limitations to be overcome, but progress is funding-dependent. Research will have to be prioritized to ensure scarce public resources are dedicated to areas of potentially greatest impact first, and private investments into vaccine development constantly compete with other investment opportunities. Although vaccines have the potential to improve animal health, safeguard agricultural productivity, and reduce antibiotic consumption and resulting resistance risks, targeted research and development investments and concerted efforts by all affected are needed to realize that potential.

Effects of feeding Original XPC™ to broilers with a live coccidiosis-vaccine under industry conditions: Part 1. Growth performance and Salmonella inhibition

Supplementation of poultry diets with Diamond V Original XPC™ (XPC) has been proposed as a means to ameliorate the commonly observed loss of appetite and depression of growth in birds given a live coccidiosis vaccine. A study was conducted to compare the effects on bird performance of a live coccidiosis vaccine in broilers, with and without the dietary inclusion of XPC (1.25 g/kg). Ross 708 male broilers (n = 1,280) were allocated to one of 4 feed treatments: cocci-vaccine (T1), cocci-vaccine + XPC (T2), cocci-vaccine + salinomycin in the grower diet only, (T3), and cocci-vaccine + salinomycin in the grower diet + XPC (T4). Birds consuming diets containing XPC (T2 and T4) and salinomycin (T3) exhibited increased (P < 0.05) feed intake and significantly heavier body weights at 28 d (1.70, 1.74, and 1.67 kg, respectively) and 42 d (3.29, 3.31, and 3.26 kg, respectively). Feed conversion ratio at 28 d was improved (P < 0.05) by adding XPC to diets (T2: 1.47 and T4: 1.44) compared to control diets (T1: 1.50 and T3: 1.47). Salmonella prevalence determined via selective media indicated the inclusion of XPC in the diet resulted in a significant reduction of Salmonella when compared to treatments lacking XPC. Molecular confirmation of Salmonella species indicated S. Kentucky to be present in 38 of the 39 positive samples. Results revealed the ability of XPC in reducing the prevalence of Salmonella. Results from this study also suggest that XPC could be used in conjunction with a live coccidiosis-vaccine to increase growth rate and improve feed conversion of broilers. However, further work is needed to delineate more specific effects directly attributable to XPC.

Chicken Coccidiosis in Central Java, Indonesia: A Recent Update

Avian coccidiosis is a huge problem worldwide. Heavily infected animals that show severe clinical signs and coccidiostat resistance are causing important economic losses. The present study aimed to update the recent cases of coccidiosis in Central Java, Indonesia, and to show the importance of the disease in the region. A total of 699 samples were obtained from different chicken breed. Different Eimeria species were detected in 175 individuals (25.04%). Three different groups of chicken breed were considered: local chicken (autochthonous chickens of Sentul and Jawa), commercial broiler, and layer. Broiler chickens showed the highest prevalence of infection (34%), followed by layer (26.26%) and local chickens (10.45%). Mild to severe clinical signs of avian coccidiosis were observed in 42% of the infected animals, while 58% of the infected animals showed no clinical signs other than low feed conversion rates. Seven different Eimeria species were identified: E. tenella was the most prevalent (43.3%), followed by E. maxima (26.3%), E. necatrix (15.7%), E. acervulina (8%), E. praecox (3.1%), E. mitis (2.2%), and E. brunetti (1.3%). Coinfections with several Eimeria species were diagnosed. With this study we found massive usage of coccidiostat in the region even though its usage cannot guarantee coccidiosis-free chicken production.

Molecular characterization and protective efficacy of silent information regulator 2A from Eimeria tenella

Background

Silent information regulator 2 (SIR2) proteins are a family of NAD + -dependent protein deacetylases that are considered potential targets for anti-parasitic agents. In this study, we cloned and characterized SIR2A of the protozoan parasite Eimeria tenella (EtSIR2A) and investigated its protective efficacy as a DNA vaccine.

Methods

The EtSIR2A gene encoding 33.37 kDa protein from E. tenella second-generation merozoites was cloned, and recombinant EtSIR2A protein (rEtSIR2A) was produced in an Escherichia coli expression system. The rEtSIR2A was used to immunize rabbits. Anti-rEtSIR2A antibodies were used to determine the immunolocolization of EtSIR2A in the parasite by immunofluorescence assay (IFA). Transcript and protein expression of EtSIR2A in different development stages of E. tenella were observed by quantitative real-time PCR (qPCR) and western blot (WB) analysis, respectively. The recombinant plasmid pCAGGS-EtSIR2A was constructed and its efficacy against E. tenella infection in chickens was evaluated.

Results

qPCR and WB analysis revealed EtSIR2A expression was developmentally regulated at both the mRNA and protein levels. EtSIR2A mRNA levels were higher in unsporulated oocysts than at other developmental stages, including sporulated oocysts, sporozoites and second-generation merozoites. In contrast, EtSIR2A protein expression levels were highest in second-generation merozoites, moderate in unsporulated oocysts and sporulated oocysts and lowest in sporozoites. Immunostaining with anti-rEtSIR2A antibody indicated that EtSIR2A was mainly located in the cytoplasm of sporozoites and second-generation merozoites, and was strongly expressed during first stage schizogony. Animal-challenge experiments demonstrated that immunization with pCAGGS-EtSIR2A significantly increased average body-weight gain, and decreased mean lesion score and oocyst output in chickens.

Conclusions

These results suggest that EtSIR2A may play an important role in parasite cell survival and may be an effective candidate for the development of new vaccines against E. tenella infection in chickens.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-016-1871-0) contains supplementary material, which is available to authorized users.

Immune protection duration and efficacy stability of DNA vaccine encoding Eimeria tenella TA4 and chicken IL-2 against coccidiosis

In our previous study, an effective DNA vaccine encoding Eimeria tenella TA4 and chicken IL-2 was constructed. In the present study, the immunization dose of the DNA vaccine pVAX1.0-TA4-IL-2 was further optimized. With the optimized dose, the dynamics of antibodies induced by the DNA vaccine was determined using indirect ELISA. To evaluate the immune protection duration of the DNA vaccine, two-week-old chickens were intramuscularly immunized twice and the induced efficacy was evaluated by challenging with E. tenella at 5, 9, 13, 17 and 21weeks post the last immunization (PLI) separately. To evaluate the efficacy stability of the DNA vaccine, two-week-old chickens were immunized with 3 batches of the DNA vaccine, and the induced efficacy was evaluated by challenging with E. tenella. The results showed that the optimal dose was 25μg. The induced antibody level persisted until 10weeks PPI. For the challenge time of 5 and 9weeks PLI, the immunization resulted in ACIs of 182.28 and 162.23 beyond 160, showing effective protection. However, for the challenge time of 13, 17 and 21weeks PLI, the immunization resulted in ACIs below 160 which means poor protection. Therefore, the immune protection duration of the DNA vaccination was at least 9weeks PLI. DNA immunization with three batches DNA vaccine resulted in ACIs of 187.52, 191.57 and 185.22, which demonstrated that efficacies of the three batches DNA vaccine were effective and stable. Overall, our results indicate that DNA vaccine pVAX1.0-TA4-IL-2 has the potential to be developed as effective vaccine against coccidiosis.

Combination of probiotics and coccidiosis vaccine enhances protection against an Eimeria challenge

Coccidiosis is endemic in the commercial broiler industry capable of inflicting devastating economic losses to poultry operations. Vaccines are relatively effective in controlling the disease; their efficacy could potentially be improved with concurrent use of probiotics as evaluated in this study using an Eimeria challenge. Day of hatch 400 Cobb-500 male broilers were assigned to one of four treatment groups including control (CON), vaccine-only gel application (VNC), probiotic-only gel application (NPC), and vaccine-plus-probiotic gel application (VPC). Birds were placed in floor pens (6 replicate pens/treatment, 16-17 birds/pen). NPC and VPC birds received the probiotics in the water on days 2-4, 8, 14-20, 22, 29, and 34-36. On day 15, birds were mildly challenged with 0.5 mL of a mixed oral inoculum of Eimeria sp. prepared with the coccidiosis vaccine at 10× the vaccination dose. Performance measurements were recorded on first day and weekly afterwards, and lesion scores were evaluated 6 days post-challenge. Overall, the probiotics and coccidiosis vaccine resulted in an enhanced protective effect against the challenge, with VPC birds exhibiting lower lesion scores in the duodenum than VNC or NPC birds. Birds in the VPC treatment also demonstrated higher weight gains during days 1-15, days 7-15, and days 21-28 when compared to the VNC birds. These results suggest that the combination of probiotics and coccidiosis vaccines could enhance performance and provide an additional protective effect against a mixed Eimeria challenge.

Herbal Remedies for Coccidiosis Control: A Review of Plants, Compounds, and Anticoccidial Actions

Coccidiosis is the bane of the poultry industry causing considerable economic loss. Eimeria species are known as protozoan parasites to cause morbidity and death in poultry. In addition to anticoccidial chemicals and vaccines, natural products are emerging as an alternative and complementary way to control avian coccidiosis. In this review, we update recent advances in the use of anticoccidial phytoextracts and phytocompounds, which cover 32 plants and 40 phytocompounds, following a database search in PubMed, Web of Science, and Google Scholar. Four plant products commercially available for coccidiosis are included and discussed. We also highlight the chemical and biological properties of the plants and compounds as related to coccidiosis control. Emphasis is placed on the modes of action of the anticoccidial plants and compounds such as interference with the life cycle of Eimeria, regulation of host immunity to Eimeria, growth regulation of gut bacteria, and/or multiple mechanisms. Biological actions, mechanisms, and prophylactic/therapeutic potential of the compounds and extracts of plant origin in coccidiosis are summarized and discussed.

Field trial of medicinal plant, Bidens pilosa, against eimeriosis in broilers

Eimeriosis is a severe protozoan disease in poultry. Because of increasing concern about drug residue and drug resistance with the use of anticoccidial drugs, natural products are emerging as an alternative and complementary approach to control avian eimeriosis. Our previous publication showed that feed supplemented with B. pilosa (BP) was effective at combating chicken eimeriosis in experimental settings. However, its efficacy against chicken eimeriosis under field conditions is not known. Here, we investigated the efficacy of BP against eimeriosis on an organic chicken farm. We found that feed supplemented with BP, at the dose of 0.025% of feed or more, significantly reduced Eimeria infection. This treatment increased body weight gain and reduced feed conversion ratio, leading to superior growth performance. It lowered morbidity/mortality rate, decreased oocysts per gram of feces and gut pathology and augmented the anticoccidial index. Collectively, these data demonstrated the potential of BP to control chicken eimeriosis on chicken farms. BP can, therefore, be used as an effective means to control eimeriosis.

The epizootiology of Eimeria infections in commercial broiler chickens where anticoccidial drug programs were employed in six successive flocks to control coccidiosis

The course of natural Eimeria infections in 6 successive broiler flocks at a commercial farm comprising 4 houses, where different anticoccidial drug programs were employed, was studied by counting the number of oocysts in the litter at weekly intervals. The course of infection in all flocks followed a bell shaped curve in which oocyst numbers, initially low, increased to a peak ranging from 36 × 10(3) to 74 × 10(3) oocysts/g (OPG) of litter around 3 to 4 wk of age. Numbers subsequently declined to 3 × 10(3) to 15 × 10(3) OPG. Oocysts could be detected between flocks when birds were not present. Species of Eimeria identified included E. acervulina, E. maxima, and E. tenella Despite the presence of large numbers of oocysts in the litter, coccidial lesions were not observed in the intestines of the birds. The performance of broilers at the study site was comparable to that of other farms in the area where birds from the same settlement were reared to a similar age using the same drug programs. The results indicate the ubiquitous nature of Eimeria spp. infections in commercial broilers despite prophylactic medication.

Investigation of the effect of coccidial vaccine challenge on apparent and standardized ileal amino acid digestibility in grower and finisher broilers and its evaluation in 21-day-old broilers

The effect of coccidial vaccine challenge (CVC, Coccivac(®)B; challenged, CHA; or unchallenged, NCH) on ileal endogenous amino acid (IEAA) losses and standardized ileal AA digestibility (SIAAD) in 21- and 42-day-old broilers fed a corn-soybean meal-dried distillers' grains with solubles-poultry by-product meal-based diet (Expt. 1) and the effect of supplemental AA in ameliorating the effect of CVC (Expt. 2) were evaluated. Expt. 1 was designed as a 2 (d 21 or 42) x 2 (NCH or CHA) factorial arrangement of treatments with 8 replicates in a complete randomized design. The CVC birds were gavaged with 12 x coccidial vaccine on d 15 and 36 and were sampled on 6 d post challenge. SIAAD was determined by correcting apparent ileal AA digestibility for IEAA losses. Feed intake (FI) and BW gain were higher (P ≤ 0.05) in 21-day-old NCH birds compared to the 21-day-old CHA birds while 42-day-old birds had higher FI and BW gain than 21-day-old NCH and CHA birds. Ileal endogenous nitrogen loss was higher (P ≤ 0.05) in 42-day-old CHA birds compared to 42-day-old NCH birds. Apparent ileal AA digestibility in 21-day-old CHA birds was lower (P ≤ 0.05) than for 21-day-old NCH and 42-day-old NCH and CHA birds. SIAAD in 21-day-old CHA birds was lower (indispensable AA = 15.2 and dispensable AA = 17.8%-unit; P ≤ 0.05) than for 21-day-old NCH and 42-day-old NCH and CHA birds. Apparent ileal digestibility and total tract utilization of DM, N, and energy were not different between d 21 NCH and d 42 NCH and CHA birds but higher (P ≤ 0.05) than for d 21 CHA birds. Supplemental AA restored feed efficiency, but not BW gain, to that of the positive control (0.715 vs. 0.737). Results from Expt.1 showed that CVC significantly influenced ileal AA digestibility in 21- but not in 42-day-old birds. Expt. 2 showed that consideration of SIAAD in feed formulation may benefit feed efficiency.

Protection of Broiler Chicks Housed with Immunized Cohorts Against Infection with Eimeria maxima and E. acervulina

The use of live oocyst vaccines is becoming increasingly important in the control of avian coccidiosis in broilers. Knowledge of the mechanisms employed when chicks uptake oocysts and become immune is important for optimizing delivery of live vaccines. The current study tests the hypothesis that chicks not initially immunized may ingest oocysts by contact with litter containing oocysts shed by immunized cohorts. In Experiment 1, day-old broiler chicks were housed in pens containing clean litter. In Trial 1, 100% of chicks in some pens were immunized with 2.5 X 10(3) Eimeria acervulina oocysts while in other pens only 75% of chicks were immunized and remaining cohorts within the pens were not immunized. Other pens contained chicks that served as nonimmunized nonchallenged controls or nonimmunized challenged controls (NIC). On day 21, birds were given a homologous challenge of 6 X 10(5) oocysts. A second identical trial was conducted, except birds were immunized with 500 Eimeria maxima oocysts and were challenged with 3 X 10(3) E. maxima oocysts. In Experiment 2, 100% of chicks in some pens were immunized with 500 E. acervulina oocysts while in other pens either 75% or 50% of the birds were immunized. On day 14, birds were challenged with 1 X 10(6) oocysts. Trial 2 was identical to Trial 1 except that birds were immunized with 100 E. maxima oocysts and challenged with 1 X 10(6) oocysts. For all experiments weight gain, feed conversion ratio (FCR), plasma carotenoids, and litter oocyst counts were measured. In Experiment 1, the level of protection in groups containing 25% nonimmunized cohorts, as measured by weight gain, carotenoid level, FCR, and oocyst litter counts, was identical to groups containing 100% immunized chicks. In Experiment 2, pens where 50% or 75% of birds were immunized with either E. maxima or E. acervulina were not well protected from decreases in weight gain and plasma carotenoids nor from increases in litter oocyst counts following a challenge infection administered on day 14 relative to NIC. In addition, pens of birds where 100% of chicks were immunized were not well protected compared to NIC, and resistance to coccidiosis infection in immunized chicks was less than resistance in chicks challenged at 21 days. These results in total suggest that, when birds are challenged after 21 days, cohorts are protected from detrimental effects of challenge infection. However, when challenge infection is given at 14 days, cohorts are not well protected. The results support a conclusion that protection to coccidiosis is conveyed to cohorts by contact with oocysts shed into the litter by immunized chicks, but this resistance may take 14 days to develop.

Impact of a drug-free program on broiler chicken growth performances, gut health, Clostridium perfringens and Campylobacter jejuni occurrences at the farm level

The use of antimicrobial agents as feed additives in poultry production is a public health concern due to the overall increase in antimicrobial resistance. Although some alternative products are commercially available, little is known on their potential impact on flock health and productivity. A prospective study involving 1.55 million birds was conducted on eight commercial broiler farms in Québec, Canada, to evaluate the impact of replacing antibiotic growth promoters and anticoccidial drugs by a drug-free program including improved brooding conditions, anticoccidial vaccination, essential oil-based feed additives, and water acidification. Various productivity and health parameters were compared between barns allocated to the conventional and the drug-free program. Zootechnical performances were monitored as productivity criteria. Clinical necrotic enteritis and subclinical enteritis occurrences, litter and fecal moistures content were measured, and microscopic gut health was evaluated. Clostridium perfringens and Campylobacter spp. strains were recovered from fecal samples collected during farm visits. Clostridium perfringens counts were used as poultry health indicators and Campylobacter prevalence was noted as well. The drug-free program was associated with a significant increase in feed conversion ratio and a decrease in mean live weight at slaughter and in daily weight gain. An increased incidence of necrotic enteritis outbreaks and subclinical enteritis cases, as well as an increase in litter moisture content at the end of the rearing period were also observed for this program. Mean microscopic intestinal lesion scores and prevalence of Campylobacter colonization were not statistically different between the two groups but the drug-free program was associated with higher Clostridium perfringens isolation rates. According to the current study design, the results suggest that substitution of antibiotic growth promoters and anticoccidial drugs by a drug-free program impacts various broiler chicken production parameters and Clostridium perfringens carriage levels.

Efficacy of chimeric DNA vaccines encoding Eimeria tenella 5401 and chicken IFN-γ or IL-2 against coccidiosis in chickens

Chimeric DNA vaccines encoding Eimeria tenella (E. tenella) surface antigen 5401 were constructed and their efficacies against E. tenella challenge were studied. The open reading frame (ORF) of 5401 was cloned into the prokaryotic expression vector pGEX-4T2 to express the recombinant protein and the expressed recombinant protein was identified by Western blot. The ORF of 5401 and chicken cytokine gene IFN-γ or IL-2 were cloned into the eukaryotic expression vector pVAX1 consecutively to construct DNA vaccines pVAX-5401-IFN-γ, pVAX-5401-IL-2 and pVAX-5401. The expression of aim genes in vivo was detected by reverse transcription-polymerase chain reaction and Western blot. Fourteen-day-old chickens were inoculated twice at an interval of 7 days with 100 µg of plasmids pVAX-5401, pVAX-5401-IFN-γ and pVAX-5401-IL-2 or 200 µg of recombinant 5401 protein by leg intramuscular injection, respectively. Seven days after the second inoculation, all chickens except the unchallenged control group were challenged orally with 5 × 10(4) sporulated oocysts of E. tenella. Seven days after challenge, all chickens were weighted and slaughtered to determine the effects of immunization. The results showed the recombinant protein was about 90 kDa and reacted with antiserum against soluble sporozoites. The animal experiment showed that all the DNA vaccines pVAX-5401, pVAX-5401-IFN-γ or pVAX-5401-IL-2 and the recombinant 5401 protein could obviously alleviate body weight loss and cecal lesions as compared with non-vaccinated challenged control and empty vector pVAX1control. Furthermore, pVAX-5401-IFN-γ or pVAX-5401-IL-2 induced anti-coccidial index (ACI) of 180.01 or 177.24 which were significantly higher than that of pVAX-5401. The results suggested that 5401 was an effective candidate antigen for vaccine. This finding also suggested that chicken IFN-γ or IL-2 could effectively improve the efficacies of DNA vaccines against avian coccidiosis.