Oocyst-Shedding Patterns of Three Eimeria Species in Chickens and Shedding Pattern Variation Depending on the Storage Period of Eimeria tenella Oocysts

Effects of methionine supplementation in a reduced protein diet on growth performance, oxidative status, intestinal health, oocyst shedding, and methionine and folate metabolism in broilers under Eimeria challenge

BACKGROUND

This study investigated effects of different methionine (Met) supplementation levels in a reduced protein diet on growth performance, intestinal health, and different physiological parameters in broilers under Eimeria challenge. A total of 600 fourteen-day-old Cobb500 male broilers were challenged with E. maxima, E. tenella, and E. acervulina, and randomly allocated in a 2 × 5 factorial arrangement. Birds received normal protein diets (20% crude protein, NCP) or reduced protein diets (17% crude protein, LCP), containing 2.8, 4.4, 6.0, 7.6, and 9.2 g/kg of Met.

RESULTS

On 6 and 9 days post inoculation (DPI), increasing Met level linearly improved the growth performance (P < 0.05). Total oocyst shedding linearly increased as Met level increased (P < 0.05). Duodenal villus height (VH):crypt depth (CD) in the LCP groups were higher on 6 DPI (P < 0.01) while lower on 9 DPI (P < 0.05) compared to the NCP groups. Jejunal CD and duodenal VH:CD changed quadratically as Met level increased (P < 0.05). On 6 DPI, liver glutathione (GSH) and glutathione disulfide (GSSG) linearly increased as Met level increased (P < 0.05). On 9 DPI, GSSG quadratically increased, whereas GSH:GSSG quadratically decreased as Met levels increased (P < 0.05). The expression of amino acid transporters linearly decreased as Met level increased (P < 0.05). The expression of zonula occludens 2 and claudin-1 linearly increased on 6 DPI whereas decreased on 9 DPI as Met level increased (P < 0.05). The expressions of cytokines were lower in the LCP groups than the NCP groups (P < 0.05). Interaction effects were found for the expression of IL-10 and TNFα on 6 DPI (P < 0.05), where it only changed quadratically in the NCP group as Met level increased. The expression of Met and folate metabolism genes were lower in the LCP groups than the NCP groups on 9 DPI (P < 0.05). The expression of these genes linearly or quadratically decreased as Met level increased (P < 0.05).

CONCLUSION

These results revealed the regulatory roles of Met in different physiological parameters including oxidative status, intestinal health, and nutrient metabolism in birds fed reduced protein diet and challenged with Eimeria.

Defining optimal dietary starch, oil, and amino acid inclusion levels for broilers experiencing a coccidiosis challenge

Alternative methods to alleviate coccidiosis in broilers are of interest to producers, including dietary strategies to minimize disruptions in growth rate and efficiency when faced with health challenges. Our objective was to determine optimal combinations of dietary starch, amino acids (AA), and oil to benefit productivity of broilers experiencing Eimeria-induced immune activation. Two trials were conducted using 1,536 male Ross 308 broiler chicks in floor pens randomly assigned to 1 of 17 experimental treatments. All birds received common starter (d 0-10) and finisher (d 24-35) diets, and only differed based on their assigned experimental grower diet (d 10-24). Trial 1 experimental grower diets ranged from 2,700 to 3,300 kcal/kg AME. Trial 2 included 10 experimental grower diets following a simplex lattice design consisting of 3 basal lots formulated to have the highest starch (45.4%), oil (10.2%), or AA density (120, 1.33% digestible Lys) and mixed in 4 equally spaced levels for each component (0, 0.33, 0.67, 1). These mixtures enabled varying densities of AA (80-120% of recommendation), starch:oil (4:1-20:1), and AME (2,940-3,450 kcal/kg). Bird and feeder weights were collected on d 0, 10, 24, and 35, and birds were exposed to an Eimeria challenge on d 11 or 12. In trial 2, excreta samples were collected for AME determination and carcasses were processed on d 36. Data were analyzed using ANOVA, t test, or regression. In Trial 1, BW gain and feed conversion were improved (P < 0.05) by increasing dietary AME. In Trial 2, birds receiving diets containing AA at 93 to 107% of recommendations and higher oil exhibited improved (P < 0.05) performance, but increased starch at the expense of oil reduced performance (P < 0.05). Relative breast and fat pad weights were not influenced by diet in Trial 2. We determined that broilers mildly challenged with Eimeria would exhibit highest BW gain when receiving diets containing 35.8% starch, 8.9% oil, and 101.3% of AA recommendations, which can be utilized by producers to maintain productivity under health-challenged conditions.

Relationship between Eimeria oocyst infectivity for chickens and in vitro excystation of E. acervulina, E. maxima, and E. tenella oocyst during long-term storage

Vaccination of chickens against avian coccidiosis in chickens often involves storing Eimeria oocysts for months after oocyst propagation and sporulation. The purpose of this study was to determine how long E. acervulina, E. maxima, and E. tenella oocysts remained viable when stored at refrigeration (4°C) or egg room (20°C) temperatures. Separate tubes containing E. acervulina, E. maxima, or E. tenella oocysts were stored at these temperatures and a sample removed every 3 mo for inoculating chickens for evidence of a patent infection. Also, an aliquot of each Eimeria species at each time-temperature combination was subjected to in vitro excystation to quantify the relative number of released sporozoites to intact (nonexcysted) sporocysts. Eimeria tenella appeared to be most susceptible to storage in that no oocyst production was observed at 9 mo at either temperature. Although E. maxima oocysts were viable at 9 mo, no oocyst production was observed at 12 mo storage at these 2 temperatures. Quite unexpected was that E. acervulina was much more stable than E. tenella and E. maxima remaining viable up to and including 27 mo at 4°C and up to and including 12 mo at 20°C. No consistent correlation was observed between in vivo oocyst production and in vitro excystation arising from these 2 respective temperatures (E. acervulina r = 0.58, r = 0.54; E. maxima r = 0.90, r = 0.54; E. tenella r = 0.38, r = 0.90). These data indicate that attention must be paid to time and temperature of Eimeria oocyst storage, and that sporozoite excystation may not be a good indicator of oocyst viability, particularly at later timepoints in incubation.

Development of a new immunodiagnostic tool for poultry coccidiosis using an antigen-capture sandwich assay based on monoclonal antibodies detecting an immunodominant antigen of Eimeria

This study was conducted to develop an antigen-capture ELISA that detects an immunodominant antigen of Eimeria, 3-1E which is present in all Eimeria species, using a set of 3-1E-specific mouse monoclonal antibodies (mAbs). Highly sensitive 3-1E-specific antigen-capture ELISA was established using compatible mAb pairs (#318 and #320) selected from 6 mAbs (#312, #317, #318, #319, #320, and #323) with high binding activity against recombinant 3-1E protein. These anti-3-1E mAbs specifically recognized E. tenella sporozoites and a higher level of 3-1E was detected in the lysate of sporozoites than in sporocysts. Immunofluorescence assay (IFA) using 2 mAbs (#318 and #320) showed specific staining around the membrane of E. tenella sporozoites. In order to measure the changes in the 3-1E level during in coccidiosis, serum, feces, jejunal, and cecal contents were individually collected daily for 7-days postinfection (dpi) with E. maxima and E. tenella. The new ELISA was sensitive and specific for 3-1E detection in all samples collected daily from E. maxima- and E. tenella-infected chickens for a week, and the detection sensitivity ranges were 2 to 5 ng/mL and 1 to 5 ng/mL in serum, 4 to 25 ng/mL and 4 to 30 ng/mL in feces, 1 to 3 ng/mL and 1 to 10 ng/mL in cecal contents, and 3 to 65 ng/mL and 4 to 22 ng/mL in jejunal contents. Following coccidiosis, the overall 3-1E levels started to increase from 4 dpi, and the highest production was shown on 5 dpi. Among the samples collected from Eimeria-infected chickens, the highest detection level was found in the jejunal contents of E. maxima-infected chickens. Furthermore, the level of IFN-γ in serum was significantly (P < 0.05) increased from 3 dpi and peaked on 5 dpi post E. maxima infection. Post E. tenella infection, the level of IFN-γ in serum gradually (P < 0.05) increased from 2 to 5 dpi and plateaued at 7 dpi. The level of TNF-α in serum was rapidly (P < 0.05) increased from 4 dpi and those levels were kept until 7 dpi post both Eimeria infections (E. maxima and E. tenella). More importantly, the daily changes in the 3-1E levels in different samples from E. maxima- and E. tenella-infected chickens were effectively monitored with this new antigen-capture ELISA. Therefore, this new immunoassay is a sensitive diagnostic tool to monitor coccidiosis in a large field population in the commercial poultry farms before clinical symptoms develop using serum, feces, and gut samples during the entire period of infection cycle starting from 1 d after infection.

Effects of Different Eimeria Inoculation Doses on Growth Performance, Daily Feed Intake, Gut Health, Gut Microbiota, Foot Pad Dermatitis, and Eimeria Gene Expression in Broilers Raised in Floor Pens for 35 Days

The study was conducted to investigate the effects of different Eimeria inoculation doses on the growth performance, gut ecosystem, and body composition of broilers in floor pens for 35 days. A total of 750 15-day-old broilers were allocated to five experimental groups with six replicate pens. The five experimental groups included unchallenged control (CON); Eimeria dose 1 (ED1): E. acervulina: 31,250/E. maxima: 6250/E. tenella: 6250; Eimeria dose 2 (ED2): E. acervulina: 62,500/E. maxima: 12,500/E. tenella: 12,500; Eimeria dose 3 (ED3): E. acervulina: 125,000/E. maxima: 25,000/E. tenella: 25,000; and Eimeria dose 4 (ED4): E. acervulina: 250,000/E. maxima: 50,000/E. tenella: 50,000. On D 21, BW were linearly reduced by increased Eimeria inoculation doses (p < 0.01). On D 35, the Eimeria challenge groups had significantly lower BW compared to the CON group. Increased Eimeria inoculation doses linearly decreased crude fat (CF) (p < 0.01) on D 21. Increased Eimeria inoculation doses tended to increase the relative abundance of the phylum Proteobacteria (p = 0.098) on D 21. On D 35, lean:fat was linearly reduced by increased Eimeria inoculation doses (p < 0.05). Eimeria infection negatively influenced growth performance and gut health in broilers in the acute phase, and the negative effects were prolonged to D 35 in floor pen conditions.

Hastening Progress in Cyclospora Requires Studying Eimeria Surrogates

Cyclospora cayetanensis is an enigmatic human parasite that sickens thousands of people worldwide. The scarcity of research material and lack of any animal model or cell culture system slows research, denying the produce industry, epidemiologists, and regulatory agencies of tools that might aid diagnosis, risk assessment, and risk abatement. Fortunately, related species offer a strong foundation when used as surrogates to study parasites of this type. Species of Eimeria lend themselves especially well as surrogates for C. cayetanensis. Those Eimeria that infect poultry can be produced in abundance, share many biological features with Cyclospora, pose no risk to the health of researchers, and can be studied in their natural hosts. Here, we overview the actual and potential uses of such surrogates to advance understanding of C. cayetanensis biology, diagnostics, control, and genomics, focusing on opportunities to improve prevention, surveillance, risk assessment, and risk reduction. Studying Eimeria surrogates accelerates progress, closing important research gaps and refining promising tools for producers and food safety regulators to monitor and ameliorate the food safety risks imposed by this emerging, enigmatic parasite.

The Effect of Necrotic Enteritis Challenge on Production Performance, Cecal Microbiome, and Cecal Tonsil Transcriptome in Broilers

The objective of this study was to identify the effects of experimental necrotic enteritis (NE) infection on the production performance, gut microbiome, and cecal tonsil transcriptome in broiler birds. A total of 192 chicks were not-induced (control) or induced with NE. NE was induced by inoculating Eimeria maxima at 14 d of age and Clostridium perfringens at 19, 20, and 21 d of age. NE challenge increased (p < 0.01) NE lesion score at 7 days post-E.maxima infection (dpi), decreased (p < 0.01) average weight gain and increased (p < 0.01) mortality at 7 and 14 dpi. NE challenge increased (p < 0.05) gut permeability at 5, 6, and 7 dpi and increased ileal C. perfringens load at 5 dpi. NE challenge increased (p < 0.01) Eimeria oocyst shedding at 5, 6, 7, 8 and 14 dpi. NE challenge decreased (p < 0.05) the relative abundance of Lactobacillaceae and increased (p < 0.05) the relative abundance of Campylobacteriaceae, Comamonadaceae, and Ruminococcaceae at 6 dpi. NE challenge upregulated (p < 0.05) genes related to immune response and downregulated (p < 0.05) genes related to lipid metabolism at 6 dpi. It can be concluded that NE infection decreased beneficial bacteria and increased gut permeability.

Effects of Tannic Acid Supplementation on Growth Performance, Oocyst Shedding, and Gut Health of in Broilers Infected with Eimeria Maxima

The purpose of this study was to evaluate effects of tannic acid (TA) on growth performance, fecal moisture content, oocyst shedding, gut permeability, lesion score, intestinal morphology, apparent ileal digestibility, and the antioxidant and immune system of broilers infected with Eimeria maxima. A total of 420 one-day-old broilers were distributed to five treatments with seven replicates of 12 birds. The five treatments were the (1) sham-challenged control (SCC; birds fed a control diet and administrated with PBS); (2) challenged control (CC; birds fed a control diet and inoculated with E. maxima); (3) tannic acid 0.5 (TA0.5; CC + 500 mg/kg TA); (4) tannic acid 2.75 (TA2.75; CC + 2750 mg/kg TA); and (5) tannic acid 5 (TA5; CC + 5000 mg/kg TA). The TA2.75 group had significantly lower gut permeability compared to the CC group at 5 days post-infection (dpi). Supplementation of TA linearly reduced oocyst shedding of E. maxima at 7 to 9 dpi (p < 0.05). At 13 dpi, the TA2.75 group had significantly greater apparent ileal digestibility (AID) of dry matter (DM) and organic matter (OM) compared to the CC group. At 13 dpi, supplementation of TA linearly increased jejunal villus height (VH). Thus, this study showed that supplementation of TA at levels of 500 to 2750 mg/kg has the potential to be an anti-coccidial agent against E. maxima in broilers.

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

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

Protective Effect of Lactobacillus plantarum P8 on Growth Performance, Intestinal Health, and Microbiota in Eimeria-Infected Broilers

Coccidiosis is one of the major parasitic diseases in the commercial broiler industry. Probiotics can protect poultry against Eimeria infection. However, the mechanisms are not fully known. Therefore, Lactobacillus plantarum P8 (P8) was used to investigate its anti-coccidial property and mechanism. Five hundred broilers were allocated to five treatments: control diet (NC), control diet + Eimeria infection (IC), control diet containing 1 × 10⁷ cfu/g P8 + Eimeria infection (P8L), control diet containing 1 × 10⁸ cfu/g P8 + Eimeria infection (P8H), and control diet + Eimeria infection + Diclazuril (DIC). At day 14, all treatments except NC were inoculated with sporulated oocysts. Results indicated that Eimeria infection increased the mortality and oocysts shedding, and declined the growth performance as well as the intestinal barrier in Eimeria-treated broilers. On the contrary, dietary supplementation of low level P8, high level P8 and DIC decreased the mortality and oocysts shedding, but improved the growth performance and intestinal barrier. The impaired intestinal morphology in the IC group was also improved by P8H and DIC treatments. Besides, the elevated oxidative stress and pro-inflammation in Eimeria-infected broilers were reduced by P8L, P8H, and DIC treatments. Metagenomic analysis indicated P8 altered the structure of the gut microbiota, and the alteration was more obvious at day 21 than day 42. Notably, IC also increased the abundances of Eimeriidae, Eimeria and Eimeria tenella at day 21, while P8L and DIC decreased the abundances. Correlation analysis revealed that bacteria in Eimeria-treated broilers positively correlated with the intestinal permeability, oxidative stress and inflammation, while bacteria in broilers receiving P8L and DIC negatively correlated with the aforementioned pathological indices. Functional prediction demonstrated that the metagenomes of Eimeria-infected broilers were involved in several diseases. But the metagenomes of P8L-treated broilers were involved in energy metabolism and replication repair. In conclusion, dietary P8 supplementation inhibited oocyst shedding and improved the growth performance as well as the intestinal health of broilers infected with Eimeria, which was closely related to the regulation of gut microbiota. Moreover, the effects of P8 may be more effective in the early infection of coccidia.

The impact of maturity on the ability of Eimeria acervulina and Eimeria meleagrimitis oocysts to sporulate

The sporulation of oocysts of Eimeria that infect poultry is known to be under the influence of environmental conditions, including temperature, oxygen supply, and moisture. However, even when these conditions are optimal, the level of sporulation can remain low. The effect of oocyst maturity on their ability to sporulate was investigated for two species of Eimeria: E. acervulina of chickens, and E. meleagrimitis of turkeys. After oral infection of birds, oocysts were collected at their production site in the intestine at different times around the prepatent period. The percentage of sporulation was determined by observation of 100 oocysts for each sample. With E. acervulina, it was observed that sporulation depended on the time of collection of the oocysts in the intestine, and that it increased with aging oocysts (from 5% to 40% globally in 8 h). With E. meleagrimitis, sporulation remained low with oocysts collected in the duodenum (below 20%), but oocysts collected in the midgut and in the lower intestine sporulated more efficiently (around 80%) than oocysts collected in the duodenum at the same time. One explanation for these results is the assumption that oocysts may be produced before fertilization, and that microgametes have not yet fertilized the newly produced oocysts. As time goes on, more oocysts would be fertilized, locally in the duodenum for E. acervulina, and descending along the gut for E. meleagrimitis. This hypothesis needs to be investigated further, but it could lead to new approaches to control these parasites by targeting the microgametes.

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.

Effect of Feed Additives as Alternatives to In-feed Antimicrobials on Production Performance and Intestinal Clostridium perfringens Counts in Broiler Chickens

Numerous non-antibiotic feed additives (alternatives to antibiotics, ATAs) have been marketed, but few have been evaluated under uniform testing conditions modelling commercial flocks. We compared 24 ATA treatments and the ionophorous coccidiostat narasin against a diet without any feed additives. Feed conversion ratio and body weight gain were registered from day 0 to 28 in Ross 308 chickens housed on litter floor. The chickens were challenged with Eimeria spp., and cecal Clostridium perfringens (CP) counts were investigated. Active components from all ATA classes had a positive impact on intestinal health or production performance. Whereas narasin had a strong CP-reducing effect in combination with performance-promoting impact, only two ATA treatments achieved significantly beneficial effects on CP counts as well as feed conversion during the time span following Eimeria challenge. Active components present in these two treatments include a Bacillus subtilis probiotic strain, short- and medium-chain fatty acids and Saccharomyces cerevisiae components. Different ATA classes had beneficial impact during distinct rearing phases and on specific performance targets, suggesting that optimizing combinations and use of active components can make ATAs even more useful tools in broiler rearing without the use of in-feed antimicrobials. Further studies of promising ATAs and ATA combinations are required.