Quantification of Eimeria acervulina in faeces of broilers: Comparison of McMaster oocyst counts from 24h faecal collections and single droppings to real-time PCR from cloacal swabs

The global prevalence and associated risk factors of Eimeria infection in domestic chickens: A systematic review and meta-analysis

BACKGROUND

Eimeria is a protozoan parasite that affects poultry, particularly chickens, causing a disease known as coccidiosis. This disease imposes substantial significant economic challenges to the poultry sector.

OBJECTIVES

The current study aimed to estimate the global prevalence and associated risk factors of Eimeria in domestic chickens.

METHODS

Multiple databases (Scopus, PubMed, ProQuest, Web of Science and Google Scholar) were searched for articles published until June 2023. The pooled prevalence was estimated using a random-effects model with a 95% confidence interval. The statistical analysis was conducted using meta packages in R version (3.6.1).

RESULTS

In total, 41 articles fulfilled the eligibility criteria. The global pooled prevalence was 44.3% (36.9%-51.8%) with Eimeria tenella (38.7%, 30.1%-47.7%) as the most prevalent species. The highest pooled prevalence was related to the Western Pacific Region (80.5%, 72.6%-87.3%) and urban areas (44.4%, 36.5%-52.6%). Moreover, areas with humid subtropical climates represent the highest overall prevalence (75.8%, 46.6%-95.9%).

CONCLUSION

The necessity for robust and innovative strategies for preventing and managing this disease cannot be overstated. Addressing Eimeria impact is crucial not only for safeguarding poultry health but also for sustaining the economic viability of the poultry industry.

Effect of dietary treatments on performance, oocysts shedding and lesion scores in broiler chickens experimentally challenged with Eimeria infection

Although anticoccidials effectively control coccidiosis, a needed reduction in the reliance on antimicrobials in animal production leads to the exploration of alternative compounds. The present study aimed to test five different dietary treatments to counteract the negative impact of coccidiosis on broiler chickens' health and performance. 1-day-old male Ross 308 broilers (n = 960) were randomly assigned to one of eight treatments, with six cages per treatment (20 birds/cage). To the diet of the broiler chickens of treatments (Trt) 1-5, a synbiotic was added from d0-10. From d10-28, birds of Trt1 and Trt2 were fed synbiotics, whereas birds of Trt3 were fed diets with glutamine, and birds of Trt4 and Trt5 were fed diets with a combination of β-glucans and betaine. From d28-35 onwards, birds of Trt1 were fed a diet with a synbiotic, whereas birds of Trt2-4 received diets with glutamine, and birds of Trt5 were fed a non-supplemented diet. Birds of the positive control group (PC; Trt6) were fed a standard diet supplemented with an anticoccidial (Decoquinate). The challenged negative control (NCchall; Trt7) and non-challenged negative control (NC) Trt8 were fed a standard diet without anticoccidial or other dietary treatment. At 7 days (d) of age, all birds were inoculated with 1 023, 115, and 512 sporulated oocysts of E. acervulina, E. maxima, and E. tenella, respectively, except for Trt8. Body weight gain (BWG), feed intake, and feed conversion ratio were assessed for each feeding phase (d0-10, d10-28 and d28-35) and overall experimental period (d0-35). Oocyst shedding, Eimeria lesion scores, cecal length, and relative weight were assessed at d13, d22, d28 and d35. Additionally, oocyst shedding was determined at d9 and d17. Litter quality was evaluated at d27 and d34, and footpad lesions at d34. During the starter (d0-10) and finisher (d28-35) periods, performance did not differ between the treatments. During the grower period (d10-28), Trt6 (PC) and Trt8 (NC) chickens had the highest BWG of all treatments (P < 0.001). Dietary treatment had no effect on litter quality and severity of footpad lesions. In the PC group (Trt6), low oocyst excretion and lesion scores were found. When comparing Trt1-5 with NCchall (Trt7), none of the treatments significantly reduced oocyst output or lesion scores. In conclusion, in this experiment, none of the dietary treatments performed similar or better compared to the PC group (Trt6) regarding performance or reducing Eimeria oocyst shedding or lesion scores.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Quality control procedure for Coccidial vaccines versus different routes of immunization

Background and Aim:

Coccidiosis is an enteric infection caused by a protozoon (Eimeriatenella). Coccidiosis is known to have a negative impact on the economy. Coccidiosis is controlled using anticoccidial drugs, antibiotics, and vaccines. Various coccidial vaccines differ in application technique, attenuation method, and the species used. Coccidial vaccines can be spray or gel-based (Form). This study aimed to compare the effect of application and approaches between spray and gel vaccines for coccidiosis.

Materials and Methods:

Specific pathogen-free chicks were vaccinated with different vaccines. Fecal samples were taken on 21 days post-vaccination for vaccine take, and then a challenge test was done on day 21.

Results:

Post-vaccination oocyst counts in gel vaccinated groups were more than the spray vaccinated ones as it recorded (1400 and 2200) oocyst/g, but the gel vaccines resulted in lower post vaccinal titer which was (10000 and 12500) oocyst/g. Results of quantitative real-time polymerase chain reaction test post-vaccination were (23.72, 20.29) cycle threshold (CT) for spray vaccines and (18.75, 17.62) CT for gel vaccinated group. By challenging all the experimental groups, the microscopic and macroscopic lesion of gel vaccines resulted in score 1, while spray vaccines groups recorded score 2 and the control non-vaccinated challenged chickens showed score 4. The non-vaccinated/non-challenged group recorded a score of zero.

Conclusion:

These results can help poultry producers to decide which delivery system will provide the best results for their production system. The gel vaccines showed a better protection rate and lower shedding, which means more protection of birds and public health.

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.

Nutritional interventions to support broiler chickens during Eimeria infection

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

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

Background

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

Methods

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

Results

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

Conclusions

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

Graphical Abstract

Supplementary Information

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

Efficacy of a Dietary Polyherbal Formula on the Performance and Gut Health in Broiler Chicks after Experimental Infection with Eimeria spp

One-hundred and fifty, one-day-old Ross-308 female chicks were randomly allocated to five equal treatments: NCONTR negative control—not challenged; PCONTR positive control—challenged; PHERB1 and PHERB2 diets were supplemented with phytogenic formula (1 and 2 g/kg feed, respectively)—challenged; PSALIN diet was supplemented with salinomycin (60 mg/kg feed)—challenged. Challenge was made by oral inoculation with 3.5 × 10⁴E. acervulina, 7.0 × 10³E. maxima and 5.0 × 10³E. tenella oocysts, at 14 days of age. One week post inoculation, bloody diarrhea, oocysts numbers, and intestinal lesions were evaluated, along with intestinal microbiota, viscosity, and pH of digesta, and histopathology. PHERB2 had a comparable (p ≤ 0.001) growth performance and feed conversion ratio to PSALIN. PHERB1 and PHERB2 had similar (p ≤ 0.001) oocyst counts to PSALIN and lower than PCONTROL. PHERB2 and PSALIN had lower (p ≤ 0.001) jejunal, ileal, and cecal lesion scores compared to PCONTR. PHERB1 and PHERB2 had higher (p ≤ 0.001) jejunal and cecal lactobacilli and lower (p ≤ 0.001) coliform counts compared to other treatments. PCONTR had lower (p ≤ 0.001) jejunum villus height, height to crypt ratio, and villus goblet cells. Breast and thigh meat resistance to oxidation was improved (p ≤ 0.001) in PHERB1 and PHERB2 compared to the PCONTR. The polyherbal formula exerted a substantial improvement on growth performance and intestinal health of the Eimeria-challenged birds.

Associations between phenotypic characteristics and clinical parameters of broilers and intestinal microbial development throughout a production cycle: A field study

Disturbances in intestinal health are a common problem affecting commercial broiler chickens worldwide. Several studies have revealed associations between health, production performance, and intestinal microbiota. This study aimed to describe the development of the intestinal microbiota of broilers within a production cycle to evaluate to what extent clinical parameters and phenotypic characteristics can explain the intestinal microbiota variation. Of four well-performing flocks within two farms, the cecal content was collected of nine broilers at 0, 2, 4, or 5, 7, 11, or 12, 14, 21, 28, 35, and 40 days of the production cycle. In total, 342 samples were analyzed using 16S ribosomal RNA gene amplicon sequencing. Variables as macroscopic gut abnormalities, gut lesions, age, individual body weight, sex, footpad integrity, the color of ceca, and foam in cecal content were determined. Ileum tissue was collected for histological quantification of villus length and crypt depth. Flock infection levels of the intestinal disease coccidiosis were measured in pooled feces from the poultry house. Increases in phylogenetic diversity were observed from hatch until day 21 of age. Constrained multivariate analysis indicated that age, farm, body weight, ileum crypt depth, cecal color, and the coccidiosis lesion score were important variables to describe the variation in cecal microbiota. These results contribute to determining relevant variables in flocks that may be indicative of the intestinal microbiota composition. Moreover, this knowledge increases the awareness of interactions between the intestinal microbiota and broiler health as well as their relative importance.

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

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

Pharmacokinetics and tissue residue of enrofloxacin in healthy, Eimeria-infected broiler chickens and those pre-treated with amprolium and toltrazuril

The pharmacokinetics of enrofloxacin was compared in healthy chickens, Eimeria infected chickens and in Eimeria infected chickens pre-treated with amprolium or toltrazuril following a single IV and oral administration at dose 10 mg/kg. The blood samples were taken after administration at different time intervals (5 min to 24 hours) to determine the pharmacokinetic parameters of enrofloxacin. The different concentrations of enrofloxacin were determined by using HPLC assay method. Serum concentrations versus time were analysed by a non-compartmental method. The results explored a significant decrease in serum concentrations of enrofloxacin at different time intervals and a significant change in pharmacokinetic profiles in Eimeria infected chickens compared with those values in healthy chickens whereas, amprolium improves these values. Toltrazuril leads to a significant decrease in enrofloxacin concentrations compared with infected non-treated chickens. Multiple-dose study revealed a longer withdrawal period of enrofloxacin in infected non-treated and infected chickens pre-treated with amprolium compared with the healthy group.

Cloacal Swabs Are Unreliable Sources for Estimating Lower Gastro-Intestinal Tract Microbiota Membership and Structure in Broiler Chickens

The gastrointestinal microbiota of chickens plays a central role in health and performance. Cloacal swabs, due to their proximity to the ceca (a vital site of functional activity), are an alternative, non-invasive method used for assaying microbial communities and might be a viable option for longitudinal studies. In this study, the microbiota of twenty paired cecal content and cloacal swab samples representing two dietary treatments was assessed using 16S rRNA V4 hypervariable region sequencing and was analyzed using the MOTHUR pipeline, Phyloseq, and Vegan packages. Paired t-test and Wilcoxon signed-rank tests showed significant differences in the Chao1 index (p-value <0.0001 and p-value <0.0001, respectively) but not in the Inverse Simpson species diversity estimator (p-value = 0.06763 and p-value = 0.06021, respectively) between the cecal content and cloacal swabs. β-diversity between the cloacal swabs and cecal microbiota also showed significant differences using PERMANOVA, HOMOVA, and weighted UniFrac testing (p-values < 0.001). Based on a paired sample analysis, this study provided evidence of the high inter-individual variation and randomness of cloacal microbiota, in contrast to cecal microbiota. Our findings indicated that cloacal swabs do not approximate the α or β diversity of cecal samples and are not suitable for longitudinal studies of gut microbiota.

Survey of coccidial infection of rabbits in Sichuan Province, Southwest China

Coccidiosis is a challenging disease of wild and domestic rabbits both, caused by Eimeria and thereby leads enormous economic losses at rabbit farms. The present study carried out to survey the prevalence and intensity of coccidial infection among the rabbits in Sichuan Province, southwest China. A total of 110 faecal samples were collected from 11 farms situated in eight main rabbits rearing administrative regions. Oocysts in faecal samples were purified, sporulated and identified according to morphological features. The overall prevalence of infection was 56.4 % (62/110), with prevalence of 64 % (47/75) for local meat breeds of rabbit and 51.4 % (18/35) for Rex Rabbits (local fur rabbits). Weanling rabbits had the highest prevalence (74 %, 37/50), followed by young rabbits (45 %, 13/29) and the adult rabbits showed the lowest prevalence (42 %, 13/31). Concurrent infection with two to seven Eimeria species was found. In total, 9 species of Eimeria were identified from oocyst-positive samples. E. perforans was the most prevalent specie (42.73 %), followed in order by Eimiera media, E. irresidua, E. magna, and E. intestinalis with prevalences of 35.45, 34.55, 31.82, and 23.64 %, respectively. Results of the present investigation indicated that the prevalence of coccidial infection is high among the rabbit population in southwest China. This study also elucidate about the coccidial infection and emphasis to adopt control strategies in commercial rabbitories.

Quantitative real-time PCR (qPCR) for Eimeria tenella replication--Implications for experimental refinement and animal welfare

The Eimeria species are highly pathogenic parasites of chickens. Research aimed at reducing their impact is hindered by a lack of non-subjective, quantitative, tools to measure parasite replication in the host. The time-consuming, and often time-sensitive, nature of existing approaches precludes their use in large-scale genetic, epidemiological, and evolutionary analyses. We have used quantitative real-time PCR (qPCR) to accurately quantify Eimeria tenella in chicken tissue and shown this to be more efficient and sensitive than traditional methodologies. We tested four chicken-specific reference qPCR assays and found beta-actin (actb) to be optimal for sample normalisation. In an experimental setting, chickens were inoculated with 500, 1500, or 4500 E. tenella oocysts and parasite replication and the impact of infection measured by i) qPCR analysis of DNA extracted from caecal tissues collected at five and eight days post-infection (dpi), ii) faecal oocyst counts (FOCs) on samples taken from six to eight dpi, and iii) lesion scoring on caeca collected post-mortem at five and eight dpi. Quantitative real-time PCR test results indicated a significant dose-dependent increase in parasite numbers among study groups for samples collected five dpi (i.e., prior to gametogony) (R² = 0.994) (p < 0.002) but not in those from day eight (after most oocyst shedding) (R² = 0.006) (p > 0.379). A strong dose-dependent increase in parasite replication and severity of infection was also revealed by FOC (R² = 0.997) and lesion scoring. Importantly, qPCR offers substantial improvements for animal welfare via improved statistical power and reduced group sizes in experimental studies. The described qPCR method overcomes subjective limitations of coproscopic quantification, allows reproducible medium- to high-throughput examination of tissues, faeces, and oocysts, and is a valuable tool for determining the impact of Eimeria infections in both experimental and field settings.

•

Quantitative PCR indicates significant dose-dependent increases in parasites.

•

More sensitive measure of parasite replication than faecal oocyst count/lesion score

•

Significant implications for animal welfare and experiment refinement (3R's)

•

Support studies focusing on the genetic basis of resistance/susceptibility

•

Major implications for investigations of key aspects of Eimeria biology and control

A selective review of advances in coccidiosis research

Coccidiosis is a widespread and economically significant disease of livestock caused by protozoan parasites of the genus Eimeria. This disease is worldwide in occurrence and costs the animal agricultural industry many millions of dollars to control. In recent years, the modern tools of molecular biology, biochemistry, cell biology and immunology have been used to expand greatly our knowledge of these parasites and the disease they cause. Such studies are essential if we are to develop new means for the control of coccidiosis. In this chapter, selective aspects of the biology of these organisms, with emphasis on recent research in poultry, are reviewed. Topics considered include taxonomy, systematics, genetics, genomics, transcriptomics, proteomics, transfection, oocyst biogenesis, host cell invasion, immunobiology, diagnostics and control.

Effects of glass bead size, vortexing speed and duration on Eimeria acervulina oocyst excystation

Improved methods for efficient excystation of Eimeria should be developed and standardized for future Eimeria-related studies. Here, the effects of different glass bead sizes (0.5, 1, 2, and 2.5 mm), and various vortex speeds (1000, 2000, and 3000 rpm) and durations (30 s, 1, 3, and 5 min) have been examined for Eimeria (E.) acervulina oocyst excystation. At 3000 rpm, all glass beads, regardless of size, efficiently ruptured E. acervulina oocysts at 5 min. At 2000 and 3000 rpm, all four glass bead sizes increasingly ruptured oocysts in a time-dependent manner. In contrast, at 1000 rpm the excystation efficiency was not related with the glass bead size or with vortexing duration. It appeared that the 1mm glass beads are most efficient for E. acervulina DNA extraction at a 3000 rpm vortexing speed for 3 and 5 min. The 2 mm glass beads delicately released the highest number of intact sporocysts at 2000 rpm for 3 min. Therefore, our data can provide valuable information for the efficient mechanical excystation of E. acervulina.

Large-scale survey of the prevalence of Eimeria infections in domestic rabbits in China

The current study examined the prevalence of Eimeria infections in domestic rabbits in China. A total of 480 faecal samples were collected from 48 farms in 14 provinces of China. Each faecal sample was subjected to oocyst counting and oocyst isolation. The Eimeria species from samples containing isolated and sporulated oocysts were morphologically identified under microscope. The overall prevalence of infections was 41.9% (201/480). Northwest China had the highest prevalence (70%), followed closely by Northeast China (65%) and Southwest China (62.5%). The prevalences in North China (34%) and South China (25.8%) were significantly lower. The large and medium farms had lower prevalences (34.2% and 37.2%, respectively) than the small farms (61.4%). Coccidian oocysts were found in 42.2% (76/180) of faecal samples from meat rabbits, 40% (28/70) from angora rabbits and 44.7% (85/190) from Rex rabbit. In total, ten species of Eimeria were identified from oocyst-positive samples. Concurrent infection with two to eight Eimeria species was found. E. perforans was the most prevalent species (35.2%), followed in order by E. media, E. magna, E. irresidua and E. intestinalis with prevalences of 31.3%, 28.8%, 19.4%, and 14.8%, respectively. Taken together, These results reveal the characteristics of the prevelance of rabbit coccidia infection in China, including the distribution, the scale of farming and the species, which are indispensable to the control of rabbits coccidiosis in China.

Effect of Eimeria acervulina infection history on the immune response and transmission in broilers

Heterogeneity in exposure to Eimeria spp. of chickens in a flock will result in differences between individual birds in oocyst output and acquired immunity, which subsequently affects transmission of the parasite in the population. The aim of this study was to quantify effects of previous infection of broilers with Eimeria acervulina on immune responses, oocyst output and transmission. A transmission experiment was carried out with pair-wise housed broilers, that differed in infection history. This "infection history" was achieved by establishment of a primary infection by inoculation of birds with 50,000 sporulated E. acervulina oocysts at day 6 of age ("primed"); the other birds did not receive a primary infection ("naïve"). The actual transmission experiment started at day 24 of age: one bird (I) was inoculated with 50,000 sporulated oocysts and was housed together with a non-inoculated contact bird (C). Oocyst excretion and parameters describing transmission, i.e. the number of infected C birds and time passed before start of excretion of C birds, were determined from day 28 to day 50 for six pairs of four different combinations of I and C birds (I-C): naïve-naïve, naïve-primed, primed-naïve and primed-primed. Immune parameters, CD4(+), CD8(+), αβTCR(+) and γδTCR(+) T cells and macrophages in duodenum, were determined in an additional 25 non-primed, non-inoculated control birds, and in the naïve-naïve and naïve-primed groups, each group consisting of 25 pairs. Although the numbers of CD4(+) T cells and γδTCR(+) T cells increased after primary infection, none of the immunological cell types provided an indication of differences in infectivity, susceptibility or transmission between birds. Oocyst output was significantly reduced in primed I and C birds. Transmission was reduced most in the primed-primed group, but nonetheless transmission occurred in all groups. This study also showed that acquired immunity significantly reduced oocyst output after inoculation and contact-infection, but not sufficiently to prevent transmission to contact-exposed birds.