Chicken Coccidiosis in Peri-Urban Family Farming in Two South American Countries: Prevalence and Circulating Eimeria spp

Family poultry production systems (FPPSs) in Chile and Argentina produce high-quality and nutritious food. However, little is known about chicken coccidiosis in these production systems. This work aimed to determine the Eimeria sp. positivity rate, circulating species, general farm management, and knowledge of the disease in FPPSs by gaining access to peri-urban markets in these two countries. The overall Eimeria sp. positivity rate, determined in 88 fecal samples, was 85.1%. Oocysts per gram in Argentinean meat-producing FPPSs were significantly higher than in Argentinean and Chilean egg-producing FPPSs. Multiplex-PCR based on seven Eimeria spp. Sequence-Characterized Amplified Region (SCAR) markers showed a great diversity of circulating species, with E. mitis (70.3%), E. acervulina (62.2%), and E. tenella (59.5%), followed by E. maxima (43.2%), E. praecox (32.4%), E. necatrix (18.9%), and E. brunetti (5.4%). Low awareness among family producers and low implementation of control measures were found. Importantly, pathogenic species were found even in asymptomatic chickens, which represents a potential chicken health threat. Furthermore, the administration of sulfonamides to broilers with clinical signs poses a risk of environmental contamination. This is the first comprehensive cross-sectional study showing that Eimeria sp. is a persistent parasite in peri-urban FPPSs in Argentina and Chile.

Evaluation of the Effectiveness of a Phytogenic Supplement (Alkaloids and Flavonoids) in the Control of Eimeria spp. in Experimentally Challenged Broiler Chickens

Avian coccidiosis remains a problematic challenge in poultry farms worldwide, with increasing concerns about resistance to conventional anticoccidial drugs, highlighting the need for alternative control strategies. A total of 256 male broilers (Ross 308), 1 day old, were randomly assigned to four experimental groups (eight replicates, each containing eight chickens) to evaluate the effectiveness of a phytogenic supplement against Eimeria spp. At 14 days, broilers were challenged via oral gavage with a mixture of six strains of live Eimeria spp. oocysts (4.0 × 104Eimeria spp. oocysts per bird). The groups included a negative control (no anticoccidials or challenge), a positive control (coccidial challenge, no anticoccidials), a phytogenic-supplemented diet based on alkaloids and flavonoids, and a diet with anticoccidials (narasin and nicarbazin). Fecal samples were collected for oocyst counts from day 14 to 23, and at 23 days (9 days post-infection), intestinal lesions and mucosa measurements were evaluated. The oocyst counts in the phytogenic and anticoccidial groups were significantly lower than in the positive control (with a reduction of 61.3% and 71.6%, respectively, compared to the positive control) (p < 0.05), with no significant differences between the phytogenic supplement and anticoccidials. The phytogenic supplement provided intermediate protection based on histopathological scores with a significantly lower histopathology score than the positive control but significantly higher than the negative control (p < 0.05). No differences in body weight, feed intake, feed conversion ratio, or mortality were observed across groups during the trial, likely due to the moderate challenge applied. In conclusion, the phytogenic supplement demonstrated anticoccidial activity comparable to narasin and nicarbazin without compromising productivity, warranting further research into its mechanisms, resistance impact, and commercial application.

Molecular phylogenetic analysis and seasonal dynamics of Eimeria species infecting broilers of Kashmir, India

Globally, the poultry industry is seriously threatened by coccidiosis caused by various species of Eimeria. This protozoan parasite inhabits the epithelial lining of the gastrointestinal tract of poultry globally and can cause serious clinical disease. The present study was carried out on poultry farms located in various regions of Kashmir, India, to investigate the prevalence and phylogenetic relationships of Eimeria species affecting broiler chickens. Over a period of one year, fecal samples were collected from 60 poultry farms in Kashmir and morphological and molecular techniques were employed for Eimeria species identification. Results revealed a high prevalence of coccidiosis, with 58.3% (35/60) of farms positive for Eimeria. The most prevalent species were E. tenella (31/35, 88.6%) followed by E. acervulina (25/35, 71.4%), E. maxima (19/35, 54.3%), E. mitis (18/35, 51.4%), and E. necatrix (9/35, 25.7%). Seasonal variation in prevalence was also observed, with the highest rates in autumn (86.7%) and summer (66.7%). Additionally, younger birds (3-4 weeks) exhibited higher infection rates (85.7%) compared to older birds (57.9%) (5-6 weeks). Mixed infection was found in 94.2% (33/35) of positive farms. Phylogenetic analysis using ITS1 sequences confirmed species clustering and revealed evolutionary relationships among Eimeria species. E. tenella and E. necatrix formed a distinct clade, while E. acervulina formed another. The study underscores the importance of molecular techniques in accurate species identification and provides valuable insights into the epidemiology of coccidiosis in poultry in Kashmir. Effective control strategies, including vaccination and improved management practices, are necessary to mitigate the economic losses associated with this widespread poultry disease.

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

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

Molecular Investigation of Eimeria Species in Broiler Farms in the Province of Vojvodina, Serbia

Coccidiosis is a significant poultry disease caused by the Eimeria species. This study aims to determine the prevalence of Eimeria spp. on broiler farms in Vojvodina, along with the identification of parasite species, and assess the implemented biosecurity measures. The study was conducted on 100 broiler chicken farms (28 small-sized; 34 medium-sized; 38 large-sized farms) from June 2018 to December 2021. One pooled sample of faeces was collected from three to six-week-old chickens from each farm, and assessment of biosecurity measures was carried out using a questionnaire. Using the PCR method, DNA of Eimeria was found in 59 samples (59%), while 41 samples (41%) were negative. Four species of Eimeria were identified, and their prevalence was the following: E. acervulina (37%), E. maxima (17%), E. mitis (25%) and E. tenella (48%). A significant difference (p < 0.05) was established in the number of oocysts in flocks from small-sized farms compared to medium-sized farms. It was found that regular implementation of disinfection, disinsection and deratisation measures, as well as all the biosecurity measures, can significantly reduce the occurrence of coccidiosis. These results will help to develop better strategies for the control and prevention of coccidiosis on farms.

Dietary organic zinc and probiotic alleviate induced Eimeria tenella infection in Japanese quails model of coccidiosis

The current study was conducted to evaluate the impact of organic zinc (OZn) and probiotic on growth performance, oocysts number, and histological features of cecum of quails following Eimeria tenella challenge. A total of 480 Japanese quails were distributed into six treatments as follows: untreated uninfected; untreated infected; E. tenella challenge + amprolium; E. tenella challenge + OZn; E. tenella challenge + probiotic; and E. tenella challenge + OZn + probiotic. Except untreated uninfected, all groups were orally gavaged at day 8 with 5 × 10⁴ E. tenella sporulated oocysts. Supplementation of OZn + probiotic improved (P = 0.001) growth performance compared to the untreated infected group. Lesion score of intestine and mortality was lower (P < 0.01) in quails supplemented with OZn + probiotic. Moreover, oocysts per gram (OPG) and histological dimensions of cecum in challenged birds were alleviated in OZn + probiotic. The histological findings of quails supplemented with OZn + probiotic showed normal intestinal villi with gentle sloughed epithelium. We concluded that OZn + probiotic may be safely included in the diet of Japanese quails to control coccidiosis.

Protective efficacy induced by Eimeria maxima rhomboid-like protein 1 against homologous infection

Introduction

Avian coccidiosis, caused by apicomplexan protozoa belonging to the Eimeria genus, is considered one of the most important diseases in the intensive poultry industry worldwide. Due to the shortcomings of live anticoccidial vaccines and drugs, the development of novel anticoccidial vaccines is increasingly urgent.

Methods

Eimeria maxima rhomboid-like protein 1 (EmROM1), an invasion-related molecule, was selected as a candidate antigen to evaluate its protective efficacy against E. maxima in chickens. Firstly, the prokaryotic recombinant plasmid pET-32a-EmROM1 was constructed to prepare EmROM1 recombinant protein (rEmROM1), which was used as a subunit vaccine. The eukaryotic recombinant plasmid pVAX1.0-EmROM1 (pEmROM1) was constructed as a DNA vaccine. Subsequently, 2-week-old chicks were separately vaccinated with the rEmROM1 and pEmROM1 twice every 7 days. One week post the booster vaccination, induced cellular immune responses were determined by evaluating the mRNA level of cytokines including IL-2, IFN-γ, IL-4, IL-10, TGF-β, IL-17, and TNFSF15, as well as the percentages of CD4⁺ and CD8⁺ T cells from spleens of vaccinated chickens. Specific serum antibody level in the vaccinated chickens was determined to assess induced humoral immune responses. Finally, the protective efficacy of EmROM1 was evaluated by a vaccination-challenge trial.

Results

EmROM1 vaccination significantly upregulated the cytokine transcription levels and CD4⁺/CD8⁺ T cell percentages in vaccinated chickens compared with control groups, and also significantly increased the levels of serum-specific antibodies in vaccinated chickens. The animal trial showed that EmROM1 vaccination significantly reduced oocyst shedding, enteric lesions, and weight loss of infected birds compared with the controls. The anticoccidial index (ACI) from the rEmROM-vaccination group and pEmROM1-vaccination group were 174.11 and 163.37, respectively, showing moderate protection against E. maxima infection.

Discussion

EmROM1 is an effective candidate antigen for developing DNA or subunit vaccines against avian coccidiosis.

Prevalence of Eimeria species, detected by ITS1-PCR, in broiler poultry farms located in seven provinces of northeastern Algeria

Coccidiosis is an important global chickens' disease which can cause serious economic losses in the poultry industry worldwide. Little is known about the extent of infection or diversity, of the causative agent Eimeria spp., in Algeria. A priority, therefore, is to determine the prevalence and species composition to inform strategies on treatments and control measures. Samples were collected from 187 broiler farms, located in 7 Northeastern Algerian provinces (Jijel, Constantine, Skikda, Mila, Setif, Batna, Bordj bou-Arreridj), and Internal Transcribed Spacer 1 PCR (ITS1-PCR) was used to determine the prevalence and composition of Eimeria species in chickens. The survey revealed the presence of all seven species of Eimeria at different prevalences (E. maxima (69%), E. acervulina (68.4%), E. necatrix (11.2%), E. tenella (8%), E. praecox (4.3%), E. mitis (2.1%), E. brunetti (2.1%). Multiple infections, with up to 4 different Eimeria species present on a single farm, were the most frequent situation in our samples (51.9% mixed infections versus 47.6% single infections). All farms revealed infected samples, and we conclude that this parasite is a significant problem in these provinces.

Influence of Brassica spp. rapeseed and canola meal, and supplementation of bioactive compound (AITC) on growth performance, intestinal-permeability, oocyst shedding, lesion score, histomorphology, and gene expression of broilers challenged with E. maxima

This study was performed to investigate the effect of feeding Brassica spp. including full-fat rapeseed, canola meal, and allyl isothiocyanate (AITC) to broiler chicken challenged with E. maxima. A total of 576 one-day old male broiler chicks were completely randomized to 8 treatments with 6 replicated cages and 12 birds per cage. The treatment diets consisted of nonchallenge control (NC, corn-SBM based diet), challenge control (CC), 10% rapeseed (10RS), 30% rapeseed (30RS), 20% canola (20CLM), 40% canola (40CLM), 500 ppm AITC (500AITC), and 1,000 ppm AITC (1000AITC). At d 14, all birds were challenged, except NC group, with a subclinical dose of E. maxima. Intestinal permeability was conducted on 5 d post-infection (dpi) and for oocyst shedding 5 to 6 dpi feces were pooled and collected. On 6 dpi, growth performance, lesion score, histomorphology, and gene expression were measured. The growth performance result showed that 10RS and 30RS groups had lower BW, BWG, FI, and higher FCR (P < 0.0001). During the challenge and overall periods, NC group had highest BW, BWG, and FI, and lowest FCR. The inclusion of canola meal showed lower performance during prechallenge period but was able to catch up BWG during challenge period. The AITC levels showed similar growth performance to CC group. Intestinal permeability for 20CLM, 40CLM, 500AITC and 1000AITC was similar to NC group, whereas CC, 10RS, and 30RS had higher permeability compared to NC (P < 0.0001). Oocyst shedding was significantly lower for 40CLM and NC, whereas all other treatments had higher oocyst shedding (P < 0.0001). All the challenged treatment groups had higher lesion score and microscore than NC (P < 0.0001). Histomorphology data showed that jejunum villus height (VH) for 1000AITC was similar to NC group, whereas CC group had the lowest VH (P = 0.01). The 30RS group had lower VH: crypt depth (CD) ratio in the jejunum and ileum. The gene expression at 6 dpi for claudin1, occludin, IL2, IL6, GLUT5, EAAT, BoAT, and LAT1 was significantly changed among the treatments. The results suggest that 30RS retards growth performance and deteriorate gut health during coccidiosis and should not be fed to chicken during the starter phase. Canola meal showed decline in growth prechallenge but maintained growth and intestinal health during the challenge period at 40% inclusion. AITC at 1,000 ppm showed similar growth as control group, but with improved gut health during the challenge period. Canola meal could be a good alternative to SBM especially during coccidiosis, whereas AITC needs to be tested vigorously in animal feeding regime.

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

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

Anticoccidial effectivity of a traditional medicinal plant, Cinnamomum verum, in broiler chickens infected with Eimeria tenella

The anticoccidial influences of various amounts of Cinnamomum verum powder were compared with that of salinomycin as standard synthetic anticoccidial drug on the anticoccidial indicators and production performance in broilers experimentally exposed to coccidiosis. Broiler chicks at 1 d of age (n = 150) were arbitrarily distributed into 6 groups. Birds from groups 1-3 were received the starter and finisher diets plus 2, 4, and 6 g of cinnamon/kg of the diet, respectively. Birds from group 4 were fed the starter and finisher diets plus 66 mg of salinomycin, group 5 constituted the positive control (PC), with the coccidial challenge, and group 6 constituted the negative control (NC), without the coccidial infection, which were both maintained on diets without any cinnamon. The results showed that BW gain, feed conversion ratio, and production efficiency factor declined considerably (P < 0.05) in the PC compared with the NC. At seventh day postinfection (DPI), the lesion score was significantly (P < 0.05) lower in the ceca of salinomycin-treated birds than the PC. The anticoccidial index was moderate in the chickens treated with salinomycin and 6 g cinnamon at 7 DPI compared with those in the PC group. In addition, cinnamon- or salinomycin-treated birds exhibited lower oocyst values and higher oocyst reduction rate than those in the PC. We concluded that C. verum at level 6 g cinnamon/kg diet moderately reduced coccidiosis and attempted to improved BW, feed conversion ratio, and production efficiency at 7 DPI compared with the infected groups.

Molecular detection of Eimeria species and Clostridium perfringens in poultry dust and pooled excreta of commercial broiler chicken flocks differing in productive performance

Necrotic enteritis and coccidiosis are the most economically detrimental enteric diseases of broiler chickens. This study aimed to investigate the association of DNA load of Clostridium perfringens, netB, and five Eimeria species (E. brunetti, E. maxima, E. necatrix, E. acervulina and E. tenella) in poultry house dust and pooled excreta with flock productive performance. The dust and pooled excreta from the floor were collected weekly at days 7, 14, 21, 28 and 35 of chicken age from 16 flocks of eight farms from two Australian integrator companies. The farms were ranked as high or low performers by each integrator according to the production performance of studied flocks. Eimeria tenella and necatrix were not detected in any farm while E. brunetti was detected in a low-performance farm and netB was detected in a high-performance farm. C. perfringens, E. acervulina and E. maxima DNA were detected on all farms with no significant differences in DNA load between high and low-performance farms or companies. The lack of association of pathogen DNA load and farm performance is possibly due to overall low to moderate pathogen DNA load detected in this study. Further studies on a larger number of farms are needed to determine whether these population level measurements of key pathogens based on PCR detection of nucleic acids are correlated with performance variables.

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 host genotype and Eimeria acervulina infection on the metabolome of meat-type chickens

Objective

A study was conducted to identify metabolic biochemical differences between two chicken genotypes infected with Eimeria acervulina and to ascertain the underlying mechanisms for these metabolic alterations and to further delineate genotype-specific effects during merozoite formation and oocyst shedding.

Methods

Fourteen day old chicks of an unimproved (ACRB) and improved (COBB) genotype were orally infected with 2.5 x 10⁵ sporulated E. acervulina oocysts. At 4 and 6 day-post infection, 5 birds from each treatment group and their controls were bled for serum. Global metabolomic profiles were assessed using ultra performance liquid chromatography/tandem mass spectrometry (metabolon, Inc.,). Statistical analyses were based on analysis of variance to identify which biochemicals differed significantly between experimental groups. Pathway enrichment analysis was conducted to identify significant pathways associated with response to E. acervulina infection.

Results

A total of 752 metabolites were identified across genotype, treatment and time post infection. Altered fatty acid (FA) metabolism and β-oxidation were identified as dominant metabolic signatures associated with E. acervulina infection. Key metabolite changes in FA metabolism included stearoylcarnitine, palmitoylcarnitine and linoleoylcarnitine. The infection induced changes in nucleotide metabolism and elicited inflammatory reaction as evidenced by changes in thromboxane B2, 12-HHTrE and itaconate.

Conclusions

Serum metabolome of two chicken genotypes infected with E. acervulina demonstrated significant changes that were treatment-, time post-infection- and genotype-dependent. Distinct metabolic signatures were identified in fatty acid, nucleotide, inflammation and oxidative stress biochemicals. Significant microbial associated product alterations are likely to be associated with malabsorption of nutrients during infection.

Cross-sectional study of Eimeria species of poultry in Kwara State, North-Central Nigeria

Coccidiosis is one of the biggest challenges faced by the global poultry industry as the protozoan is found anywhere poultry are reared. Before now, there have been no documents on the intensity and diversity of Eimeria species of poultry in Kwara State. This study aimed to determine the prevalence and intensity of Eimeria species and its species diversity among poultry in Kwara Central, North-Central Nigeria. Five hundred and two fecal samples (from four hundred and seventy two chickens and thirty turkeys) were collected from chickens and turkeys from 15 farms from December 2017 to May 2018. The samples were subjected to floatation technique. Positive samples were further subjected to the McMaster counting technique for determining the intensity of infection. Sporulation of unsporulated oocysts was carried out using 2.5% potassium dichromate (K₂Cr₂O₇), for the purpose of identifying the different Eimeria species. Ninety five (18.9%) of the sampled population, 10 (66.7%) of the 15 sampled farms were positive for Eimeria species. The total mean oocyst per gram was 6325.0. Eight Eimeria species were detected in the study: 7 in chickens and 1 in turkeys. Eimeria tenella was the most predominant among chickens, E. meleagrimitis was the only species detected in turkeys. Age, sex, bird type, physiological status, farm age, farm size (acres), management system, frequency of anthelmintic use, frequency of anticoccidial use, distance to dumping site (meters), level of biosecurity and frequency of cleaning the pen were significantly associated (P < 0.05) with the occurrence of Eimeria infection. It is envisaged that the information obtained in this study will contribute to a clearer understanding of the epidemiology of poultry coccidiosis, for better management protocol which will improve the productivity of the sector in Kwara State and Nigeria.

Prevalence of Eimeria species in domestic chickens in Anhui province, China

Prevalence studies can adequately assist in the design of prophylaxis strategies for disease control. Here, the prevalence of Eimeria species in chickens was investigated in Anhui province, China, from July to September 2016. A total of 171 samples were tested by microscopic examination and molecular methods. The prevalence of coccidiosis in Anhui province was found to be 87.75% (150/171). Eimeria tenella was the most prevalent species (80.67%, 121/150), and Eimeria necatrix, Eimeria mitis, Eimeria maxima, Eimeria brunetti and Eimeria acervulina were 68% (102/150), 55.33% (83/150), 54.67% (82/150), 44.67% (67/150) and 2.67% (4/150), respectively. Eimeria praecox was not detected at all. The most common combinations are E. tenella, E. maxima, E. necatrix, E. brunetti and E. mitis (26.67%, 40/150), followed by E. tenella, E. maxima and E. necatrix (19.33%, 29/150). Eimeria necatrix exhibited the highest participation in multiple infections. The results of the present study suggested that Eimeria infection is mixed, severe and widespread in chickens, Therefore, integrated strategies should be performed to prevent and control coccidial infection in chickens in Anhui province.

Investigations on the Occurrence and Associated Risk Factors of Avian Coccidiosis in Osun State, Southwestern Nigeria

Avian coccidiosis is one of the most important diseases of poultry and it is responsible for a large number of poultry mortalities worldwide. This study was carried out to investigate the occurrence and associated risk factors of avian coccidiosis in Osun State, Nigeria. Fecal samples were collected and examined from 5,544 avian species that were brought for treatment at the state veterinary hospitals over a 10-year period. Parameters such as age, sex, season, and species of birds were determined. Also, the months of the year were taken into consideration. Overall prevalence of 41.3% was recorded. The year specific rate for avian coccidiosis was highest in 2007 (97.9%) and lowest in 2006 (0.4%), while the month-specific rate was highest in November (85.7%) and lowest in July 2006 (13.3%). There was a significantly (P < 0.05) higher prevalence in young birds compared to adults, in males compared to females, and during the wet season compared to the dry season. Broilers (99.8%) and cockerels (81.0%) were the bird types with the highest prevalence rate. The high prevalence of avian coccidiosis in the study area shows that the disease is endemic and there is need to embark on a radical preventive measure to curtail the disease.

Prevalence of Coccidiosis in Free-Range Chicken in Sidi Thabet, Tunisia

Background. Enteric diseases are an important concern to the poultry industry and coccidiosis is imposing a significant economic burden worldwide. Objectives. The main goal of the present study was to investigate the prevalence of coccidiosis in free-range chicken in Sidi Thabet, northeast Tunisia. Methods. Six hundred and thirty free-range chickens along with fecal samples were collected from 15 flocks in this region and two hundred chickens were found positive for oocysts of Eimeria spp. Intestines were dissected and examined for macroscopic lesions. The mucosa of small intestine and the caeca were examined for the presence and identification of parasitic forms using parasitology methods. The mean lesion scores were usually low (<2+) in different intestinal portions of different types of chicken and high scores (>2+) were attributed mainly to the caeca. Results. The overall rate of coccidiosis was 31.8%: E. tenella (61.5%), E. maxima (12%), and E. acervulina (1.5%). Mixed Eimeria species infection was observed with overall prevalence 26.5%. There was a statistically significant difference (P < 0.05) among infection rates, age groups, season, diarrhea, and type of chicken. Conclusion. This is the first report of coccidiosis rate in free-range chicken in this region. Further additional studies are needed to develop better preventive measures against coccidiosis in the country.

Combination of cell culture and qPCR to assess the efficacy of different anticoccidials on Eimeria tenella sporozoites

Three in vitro studies were designed to develop an assay for anticoccidial efficacy by use of laboratory (Houghton) and field (T-376) Eimeria tenella strains. In study (1), minimum inhibitory concentrations (MICs) of monensin (Mon), maduramicin (Mad), salinomycin (Sal), and lasalocid (Las) were determined that are able to inhibit more than 50% of sporozoites in host cell (Madin-Darby bovine kidney (MDBK)) penetration and more than 95% of Houghton sporozoites development to mature merozoites (treatment time 24 h) using quantitative real-time PCR (qPCR). MICs were 0.5, 2.5, 1, and 0.5 μg/ml for Mon, Mad, Sal, and Las, respectively. Applying the previous MIC on T-376 strain revealed a different sensitivity profile. Mad reduced T-376 gene copies by only 89.3% after 96 h of infection. In study (2), Houghton strain sporozoites were incubated with MIC of the different tested ionophores for 2 and 4 h, respectively; afterwards, their ability to invade MDBK cells was determined using phase-contrast microscopy and qPCR. Treatment of sporozoites with ionophores for 4 h resulted in significant inhibition of invasion compared with non-treated parasites as assessed both by microscopy as well as qPCR. Inhibition rates for Mon, Mad, Sal, and Las were 90.2, 75.0, 88.3, and 82.6% using phase-contrast microscopy and 83.9, 81.4, 85.8, and 75.4% using qPCR, respectively. T-376 sporozoite invasion into MDBK cells was reduced to 48.9% by Mad. Study (3) was conducted to determine inhibition exerted by toltrazuril (Tol). Tol at 5 μg/ml reduced reproduction of Houghton strain by 95%, whereas T-376 was only reduced by 86.5%. The presented experiments indicate that infectivity inhibition of sporozoites incubated for 4 h with anticoccidials and development inhibition after 96 h of infection by qPCR are suitable means to assess sensitivity of E. tenella strains to anticoccidials.

Detection of four important Eimeria species by multiplex PCR in a single assay

The oocysts of some of the recognized species of chicken coccidiosis are difficult to distinguish morphologically. Diagnostic laboratories are increasingly utilizing DNA-based technologies for the specific identification of Eimeria species. This study reports a multiplex polymerase chain reaction (PCR) assay based on internal transcribed spacer-1 (ITS-1) for the simultaneous diagnosis of the Eimeria tenella, Eimeria acervulina, Eimeria maxima, and Eimeria necatrix species, which infect domestic fowl. Primer pairs specific to each species were designed in order to generate a ladder of amplification products ranging from 20 to 25 bp, and a common optimum annealing temperature for these species was determined to be 52.5 °C. Sensitivity tests were performed for each species, showing a detection threshold of 1-5 pg. All the species were amplified homogeneously, and a homogenous band ladder was observed, indicating that the assay permitted the simultaneous detection of all the species in a single-tube reaction. In the phylogenic study, there was a clear species clustering, which was irrespective of geographical location, for all the ITS-1 sequences used. This multiplex PCR assay represents a rapid and potential cost-effective diagnostic method for the detection of some key Eimeria species that infect domestic fowl.

The effects of combiningArtemisia annuaandCurcuma longaethanolic extracts in broilers challenged with infective oocysts ofEimeria acervulinaandE. maxima

Due to an increasing demand for natural products to control coccidiosis in broilers, we investigated the effects of supplementing a combination of ethanolic extracts ofArtemisia annuaandCurcuma longain drinking water. Three different dosages of this herbal mixture were compared with a negative control (uninfected), a positive control (infected and untreated), chemical coccidiostats (nicarbazin+narazin and, later, salinomycin), vaccination, and a product based on oregano. Differences in performance (weight gain, feed intake, and feed conversion rate), mortality, gross intestinal lesions and oocyst excretion were investigated. Broilers given chemical coccidiostats performed better than all other groups. Broilers given the two highest dosages of the herbal mixture had intermediate lesion scores caused byEimeria acervulina, which was higher than in broilers given coccidiostats, but less than in broilers given vaccination, oregano and in negative controls. There was a trend for lower mortality (P= 0·08) in the later stage of the growing period (23–43 days) in broilers given the highest dosage of herbal mixture compared with broilers given chemical coccidiostats. In conclusion, the delivery strategy of the herbal extracts is easy to implement at farm level, but further studies on dose levels and modes of action are needed.

Loop-mediated isothermal amplification (LAMP) assays for the species-specific detection of Eimeria that infect chickens

Background

Eimeria parasites can cause the disease coccidiosis in poultry and even subclinical infection can incur economic loss. Diagnosis of infection predominantly relies on traditional techniques including lesion scoring and faecal microscopy despite the availability of sensitive molecular assays, largely due to cost and the requirement for specialist equipment. Despite longstanding proven efficacy these traditional techniques demand time and expertise, can be highly subjective and may under-diagnose subclinical disease. Recognition of the tight economic margins prevailing in modern poultry production and the impact of avian coccidiosis on poverty in many parts of the world has highlighted a requirement for a panel of straightforward and sensitive, but cost-effective, Eimeria species-specific diagnostic assays.

Results

Loop-mediated isothermal amplification (LAMP) is an uncomplicated, quick and relatively inexpensive diagnostic tool. In this study we have developed a panel of species-specific LAMP assays targeting the seven Eimeria species that infect the chicken. Each assay has been shown to be genuinely species-specific with the capacity to detect between one and ten eimerian genomes, equivalent to less than a single mature schizont. Development of a simple protocol for template DNA preparation from tissue collected post mortem with no requirement for specialist laboratory equipment supports the use of these assays in routine diagnosis of eimerian infection. Preliminary field testing supports this hypothesis.

Conclusions

Development of a panel of sensitive species-specific LAMP assays introduces a valuable new cost-effective tool for use in poultry husbandry.

Prevalence and risk factors for subclinical coccidiosis in broiler chicken farms in Mazandaran province, Iran

Coccidiosis is a disease of almost universal importance in Poultry production. The subclinical form of coccidiosis has most significant economic impact due to impaired growth rate and feed conversion. Some factors such as: age, size of flock, season, etc., may effect on severity of this disease. In this study, the relationships between some major risk factors and prevalence of subclinical coccidiosis were investigated. This study was done in 120 broiler farms in five different cities of Mazandaran province, north of Iran. Five chicks (3-8 weeks of ages) were taken randomly from every 120 farms and post-mortem and parasitological examinations were performed. Five Eimeria spp. were recognized: Eimeria tenella, Eimeria maxima, Eimeria acervulina, Eimeria brunetti, and Eimeria necatrix. The prevalence rate of subclinical coccidiosis among them is 75% (90 farms out of 120). E. acervulina was the most prevalent species (65.5%) followed by E. maxima (17.7%), E. tenella (15.5%), E. brunetti (10%), and E. necatrix (5.5%). According to what the results approve, the occurrence of subclinical coccidiosis is significantly related to the age and size of flock, whereas the other factors such as the season of year, industrial strains, chicken's keeping system, and anticoccidial drugs do not affect this phenomenon remarkably.

Construction of PCR primers to detect and distinguish Eimeria spp. in northern bobwhites and a survey of Eimeria on gamebird farms in the United States

Coccidiosis is an important disease in captive gamebirds, including northern bobwhites (Colinusvirginianus). Three Eimeria species, Eimeria lettyae, Eimeria dispersa, and Eimeria colini, have been described in bobwhites. Distinguishing the various Eimeria spp. is often problematic because of similarity in oocyst morphology and site of infection and thus requires live bird infections to distinguish between the coccidian species. To aid in identification and diagnosis, PCR specific primers were generated against the internal transcribed spacer region 1 (ITS-1) of the ribosomal RNA gene using sequences obtained from coccidian-positive samples collected from diagnostic cases or litter from captive bobwhites. Three distinct Eimeria spp. were detected. Species-specific primers were constructed and used to survey the prevalence of the species in 31 samples collected from 13 states. The primers survey results identified E. lettyae, E. dispersa, and Eimeria sp. in 20 (64.5%), 22 (71%), and 29 (93.5%) of the samples, respectively. Mixed infections were common: 13 (41.9%) samples had 3 Eimeria spp., 14 (45.2%) had 2 spp., and 4 (12.9%) samples had only 1 species. The species were widely distributed over the area sampled and were not associated with the age of the flock.

Enhancement of resistance to coccidiosis and necrotic enteritis in broiler chickens by dietary muscadine pomace

Muscadine pomace (MP), a by-product of the production of wine and juice from Vitis rotundifolia, was dried and tested in chickens for effects on primary resistance to coccidiosis, development of protective immunity after vaccination with live coccidia, and resistance to necrotic enteritis (NE) caused by the joint action of Clostridium perfringens and coccidia. To test primary resistance to coccidiosis, 2-wk-old chicks were given 2% or 5% MP in the diet and inoculated with Eimeria acervulina and E. maxima. Birds given MP at either level had significantly (P < 0.05) lower lesion scores at 7 days postinoculation, in comparison with control birds, although weight gains were statistically similar. Broiler chickens were given 2% or 5% MP and grown to 42 days to test the palatability of MP. Birds given 2% MP in feed grew similarly to untreated controls, but birds given 5% had poorer average live weight. This suggested a negative effect on feed intake at the higher level. The effects of dietary 0.5% or 2.0% MP on immune protection were tested after live coccidiosis vaccination in the hatchery. Chicks were removed from each pen at 21 days of age and challenged with E acervulina, E. maxima, and E. tenella. Resistance to infection was improved by MP as suggested by significantly (P < 0.05) lower lesion scores 7 days postchallenge, and improved weight gains in comparison with immunized control birds that did not receive MP. At 42 days of age, birds given MP had higher average live weights than controls, although feed efficiency was not affected. An established model was used to study the effect of MP on NE in broiler chickens. Chicks were inoculated with live coccidia at 14 days of age and dosed orally with live cultures of C perfringens on day 19, day 20, and day 21. Enteritis caused 48% mortality in the first study and 67% mortality in the second study. Dietary MP at 0.5-2.0% significantly (P < 0.05) reduced mortality in both experiments; improved weight gain relative to the unmedicated, infected control; and reduced lesion scores at necropsy. Overall, the results of six experiments suggested that MP given in the diet at 0.5% or higher had a positive effect on primary resistance and development of acquired resistance to two severe intestinal diseases in chickens.

Factors affecting intestinal health in poultry

The gastrointestinal (GI) tract has the most extensive exposed surface in the body and is constantly exposed to a wide variety of potentially harmful substances. The GI tract acts as a selective barrier between the tissues of the bird and its luminal environment. This barrier is composed of physical, chemical, immunological, and microbiological components. A wide range of factors associated with diet and infectious disease agents can negatively affect the delicate balance among the components of the chicken gut and, as a result, affect health status and production performance of birds in commercial poultry operations. Phasing out of antibiotic growth promoters from poultry diets in Europe and recent moves toward reduction or removal of these compounds in other parts of the world including North America will likely change the microbial profile of the GI tract environment in commercial poultry. This paper reviews the GI tract from developmental, immunological, and microbial standpoints and then discusses factors that can affect health status of this system. Necrotic enteritis and coccidiosis and their interactions, and possible consequences of antibiotic growth promoter removal from poultry diets with respect to these diseases, are discussed in more detail.

A survey of the economic impact of subclinical Eimeria infections in broiler chickens in Norway

The objective of this work was to examine the impact of subclinical coccidial infection on commercial performance, expressed as a modified European Production Index, in broilers. Performance data, and litter and faecal samples, were collected from two independent observational surveys of Norwegian broilers receiving in-feed narasin during 2000 to 2004. Numbers of oocysts per gram (OPG) of litter collected during rearing (Study 1) or faecal samples collected at slaughter (both studies), and relative frequencies of Eimeria species categories (both studies) were calculated. Polymerase chain reaction-based identification of Eimeria species was performed in Study 2. A definition of flocks at risk of impaired performance associated with coccidia ("risk flock"), using the predominant species and OPG level as criteria, was tested. Coccidia had a significant effect on performance in the first, but not the second study. In Study 1 the following coccidia variables were found to be associated with impaired performance in multivariate models: OPG at slaughter (ordinal), mean OPG during rearing (ordinal) and "risk flock" (binomial). The European Production Index was approximately 9% lower in flocks with infection levels >50 000 OPG at slaughter in Study 1. The composition of coccidial populations shifted between Study 1 and Study 2, from a dominance of medium and large oocysts to a dominance of small oocysts. There was a substantial increase in prevalence of coccidial infection from Study 1 to Study 2, but mean infection levels were similar in the two surveys. The "risk flock" definition was useful as an indicator of coccidia-associated performance loss in Study 1, where subclinical coccidiosis was an important factor. The results suggest that the economic importance of subclinical coccidiosis may vary substantially with time, and they emphasize the need for population studies on the importance and dynamics of specific coccidial infections under different field conditions.

Prevalence of parasites of the local scavenging chickens in a selected semi-arid zone of Eastern Kenya

A study to identify and estimate the prevalence of parasites of local chickens in a semi arid area of Kenya was conducted between March 2005 and August 2006. Three hundred and sixty (360) local chickens purchased from Yathui division of Machakos were examined. Of those, 93.3% had helminths. Nematodes were recovered in 268 (74.4%) chickens whereas 245 (68.1%) had cestodes. Tetrameres americana (37.7%), Ascaridia galli (33.3%) and Heterakis gallinarum (22.8%) were the most important nematode species identified. Raillietina echinobothrida (33.3%) and Davainea proglottina (19.4%) were the two most important cestode species identified. Two coccidia species, namely Eimeria necatrix (6.7%) and E. tenella (16.7%) were isolated and identified as per location in the digestive system. Important ectoparasites identified included Echidnophaga gallinacea (76.7%), Menacanthus stramineus (79.4%) and Dermanyssus gallinae (60.0%). Endo-parasites (helminths and coccidia) occurred in significantly (p<0.05) higher frequencies during the wet season than during the dry season. On the contrary, ecto-parasites were significantly (p<0.05) more fequent during the dry season. Male chickens generally exhibited increased odds for the occurrence of parasites than female birds. Further investigations are required to establish a plausible explanation for this. Overall, parasitism was a big constraint to chicken productivity in the study area. Urgent integrated parasite control approaches should be initiated to address parasitism in chickens in the Yathui cluster.

Development and validation of real-time polymerase chain reaction assays specific to four species of Eimeria

The development of quantitative real-time polymerase chain reaction (PCR) assays specific to Eimeria acervulina, Eimeria maxima, Eimeria necatrix and Eimeria tenella is described and validated. The PCR templates adopted include a fragment of a gene encoding a microneme protein and previously characterized species-specific random amplified polymorphic DNA (RAPD) sequences. The sensitivity of each assay allowed the consistent detection of between one and 10 parasite genomes, equivalent to between one or two sporulated oocysts or a fraction of a single mature schizont, unaffected by the presence of chicken (host) or other Eimeria species DNA. Regression coefficients in excess of 0.99 over linear ranges of at least six orders of magnitude, together with comparable PCR efficiencies, demonstrated the robust reproducibility of each assay and suggest that two or more may be successfully multiplexed. The species-specific assays described here, combined with a previously published generic Eimeria species real-time PCR, provide valuable components in a "tool box" to accurately quantify the presence of specific Eimeria species in environmental or within-host phases of the lifecycle with little specialist knowledge. The application of these assays may benefit chicken husbandry, veterinary practice, quality control of live vaccine production and scientific research.

The application of a polymerase chain reaction (PCR)-based capillary electrophoretic technique provides detailed insights into Eimeria populations in intensive poultry establishments

Intestinal coccidiosis, caused by one or multiple species of Eimeria (Protozoa: Apicomplexa), is one of the most important infectious diseases affecting chickens. In this study, we used a polymerase chain reaction (PCR)-based capillary electrophoresis (CE) approach to conduct an epidemiological survey of Eimeria species in seven Australian broiler flocks, varying in age from 18 to 42 days. We confirmed that all seven recognized Eimeria species of poultry were present. Eimeria acervulina and E. maxima were the most common, followed by E. mitis (i.e., 89%, 87% and 64% of chickens, respectively). E. praecox was present in 44% of birds, whereas E. brunetti and E. tenella were uncommon, being found in 36% and 26%, respectively. E. necatrix was rarely detected (10%). Even the least common species were present in more than 70% of sheds. The prevalence of individual species was higher in older than in younger chickens. Most of the chickens sampled were simultaneously infected with multiple Eimeria species (mean=3.6). The number of Eimeria oocysts excreted per gram of faeces reached a peak at 36 days of age, before declining to a considerably lower level by 42 days. As anticoccidial drugs were permanently withdrawn at 36 days, the decreasing Eimeria oocyst excretion rates indicated the development of protective immunity in the chickens. The present study showed that even healthy chickens usually harbour numerous species of Eimeria. The CE technique proved to be a time and cost-effective means of investigating the epidemiology of Eimeria in commercial establishments.

Investigating a persistent coccidiosis problem on a commercial broiler–breeder farm utilising PCR-coupled capillary electrophoresis

In the present study, we utilised a polymerase-chain-reaction-coupled capillary electrophoresis (CE) approach to investigate the epidemiology of Eimeria species on a broiler-breeder farm in Victoria, Australia. The Eimeria populations of two flocks vaccinated against coccidiosis were followed over an 11-week period. All seven recognised Eimeria species of chickens were detected in both flocks. One flock suffered increased morbidity and mortality in its eighth week and had consistently higher Eimeria oocyst counts, species prevalences and rates of co-infections. Four Eimeria species included in the vaccine administered occurred at higher prevalences before the disease outbreak in the flock. Using the CE approach, two new, previously undescribed Eimeria genotypes were discovered in both chicken flocks, one of which dominated toward the end of the study period. The molecular approach proved versatile and capable of providing useful epidemiological data which could be used to investigate and interpret coccidiosis outbreaks.

Intercurrent coccidiosis and necrotic enteritis of chickens: rational, integrated disease management by maintenance of gut integrity

Coccidiosis and necrotic enteritis (NE) are globally common, sometimes intercurrent, diseases of poultry. The risk of NE, due to the Gram-positive bacterium Clostridium perfringens, has increased in recent years because of the voluntary or legally required withdrawal of the use of certain in-feed antibiotic growth promoters with anticlostridial activity. In-feed ionophorous anticoccidial drugs incidentally also possess anticlostridial activity. Such ionophores, although not banned, are usually precluded when live anticoccidial vaccines are used, potentially increasing yet further the risk of NE. This review provides information for the design of rational, integrated management strategies for the prevention and control of coccidiosis and NE in chickens by maintaining gut integrity. Because of differences in local availability of feed ingredients and national legislations regarding antibiotic growth promoters and anticoccidial vaccine licensing, no universal strategy is applicable. The diseases and their interactions are described under the headings of forms of disease, diagnosis, sources of infection, pathophysiological effects, predisposing factors, and control methods. Elements of gut integrity, which influences host predisposition and clinical responses to disease, include physical development, immune competence, gut enzyme activity, mucin production, gut flora and epithelial damage. Experimental studies of coccidiosis and NE are compared, and where possible reconciled, with field observations. Gaps in knowledge and necessary further experiments are identified. Insights are provided regarding interactions between coccidiosis, NE, and the use of live anticoccidial vaccines. Recent changes in NE prevalence in commercial flocks, and their possible causes, are discussed. The necessarily wide range of topics reviewed emphasizes the enormous complexity of this disease combination, and indicates the importance of a multidisciplinary approach in order to reduce its harmful impact on the world's poultry industry.

Integrating genetics and genomics to identify new leads for the control ofEimeriaspp

Eimerian parasites display a biologically interesting range of phenotypic variation. In addition to a wide spectrum of drug-resistance phenotypes that are expressed similarly by many other parasites, theEimeriaspp. present some unique phenotypes. For example, unique lines ofEimeriaspp. include those selected for growth in the chorioallantoic membrane of the embryonating hens egg or for faster growth (precocious development) in the mature host. The many laboratory-derived egg-adapted or precocious lines also share a phenotype of a marked attenuation of virulence, the basis of which is different as a consequence of thein ovoorin vivoselection procedures used. Of current interest is the fact that some wild-type populations ofEimeria maximaare characterized by an ability to induce protective immunity that is strain-specific. The molecular basis of phenotypes that defineEimeriaspp. is now increasingly amenable to investigation, both through technical improvements in genetic linkage studies and the availability of a comprehensive genome sequence for the caecal parasiteE. tenella. The most exciting phenotype in the context of vaccination and the development of new vaccines is the trait of strain-specific immunity associated withE. maxima. Recent work in this laboratory has shown that infection of two inbred lines of White Leghorn chickens with the W strain ofE. maximaleads to complete protection to challenge with the homologous parasite, but to complete escape of the heterologous H strain, i.e. the W strain induces an exquisitely strain-specific protective immune response with respect to the H strain. This dichotomy of survival in the face of immune-mediated killing has been examined further and, notably, mating between a drug-resistant W strain and a drug-sensitive H strain leads to recombination between the genetic loci responsible for the specificity of protective immunity and resistance to the anticoccidial drug robenidine. Such a finding opens the way forward for genetic mapping of the loci responsible for the induction of protective immunity and integration with the genome sequencing efforts.

The biology of avian Eimeria with an emphasis on their control by vaccination

Studies on the biology of the avian species of Eimeria are currently benefiting from the availability of a comprehensive sequence for the nuclear genome of Eimeria tenella. Allied to some recent advances in transgenic technologies and genetic approaches to identify protective antigens, some elements are now being assembled that should be helpful for the development of a new generation of vaccines. In the meantime, control of avian coccidiosis by vaccination represents a major success in the fight against infections caused by parasitic protozoa. Live vaccines that comprise defined populations of oocysts are used routinely and this form of vaccination is based upon the long-established fact that chickens infected with coccidial parasites rapidly develop protective immunity against challenge infections with the same species. Populations of wild-type Eimeria parasites were the basis of the first live vaccines introduced around 50 years ago and the more recent introduction of safer, live-attenuated, vaccines has had a significant impact on coccidiosis control in many areas of the world. In Europe the introduction of vaccination has coincided with declining drug efficacy (on account of drug resistance) and increasing concerns by consumers about the inclusion of in-feed medication and prospects for drug residues in meat. The use of attenuated vaccines throughout the world has also stimulated a greater interest in the vaccines that comprise wild-type parasites and, during the past 3 years worldwide, around 3x10(9) doses of each type of vaccine have been used. The need for only small numbers of live parasites to induce effective protective immunity and the recognition that Eimeria spp. are generally very potent immunogens has stimulated efforts to develop other types of vaccines. None has succeeded except for the licensing, within several countries in 2002, of a vaccine (CoxAbic vaccine; Abic, Israel) that protects via the maternal transfer of immunoglobulin to the young chick. Building on the success of viral vaccines that are delivered via the embryonating egg, an in ovo coccidiosis vaccine (Inovocox, Embrex Inc.) is currently in development. Following successful field trials in 2001, the product will be ready for Food and Drug Administration approval in 2005 and a manufacturing plant will begin production for sale in late 2005. Limited progress has been achieved towards the development of subunit or recombinant vaccines. No products are available and studies to identify potential antigens remain compromised by an absence of effective in vitro assays that correlate with the induction of protective immunity in the host. To date, only a relatively small portfolio of molecules has been evaluated for an ability to induce protection in vivo. Although Eimeria are effective immunogens, it is probable that to date none of the antigens that induce potent protective immune responses during the course of natural infection has been isolated.

Anticoccidial vaccines for broiler chickens: pathways to success

The use of live vaccines, either attenuated or non-attenuated, for the control of coccidiosis due to Eimeria infections in broiler breeder or layer chickens is well established. Use in broilers, however, has been slow to gain acceptance. This has been partly for economic reasons, but also because of perceived adverse effects on early chick growth, particularly with non-attenuated vaccines, and concerns about timely onset of protective immunity in such short-lived birds. This review describes advances in understanding of epidemiological factors and recent improvements of administration methods that have helped to allay these fears and to make the use of anticoccidial vaccines in broilers technically achievable. Topics discussed include: (1) types of commercially available vaccine, (2) vaccines in development, (3) vaccination methods and equipment, (4) basis of vaccine efficacy and immunogenic variation of parasites, (5) key factors in the survival, sporulation and dissemination of vaccinal oocysts, (6) descriptions and significance of patterns of litter oocyst accumulation and occurrence of intestinal lesions in vaccinated flocks, (7) rotation of anticoccidial vaccination and chemotherapy to restore drug sensitivity to resistant wild-type coccidia, (8) combinations of anticoccidial vaccination and chemotherapy, (9) interactions between coccidiosis and clostridiosis in broilers and compatibilities of potential control methods, (10) published performance data for live anticoccidial vaccines in broilers, (11) possible further developments of live vaccines.

Flock-level prevalence of Eimeria species among broiler chicks in northern Jordan

Six chicks (3-6 weeks of age) were taken randomly from each of 200 broiler farms in northern Jordan, these chicks were submitted for post-mortem and parasitological examinations. Seven Eimeria spp. were identified: E. acervulina, E. brunetti, E. maxima, E. necatrix, E. mivati, E. mitis, and E. tenella. Half (50%) of the farms surveyed had all six chicks infected, 23% of the farms were free of the infection. E. tenella was the most prevalent species (39%) followed by E. necatrix (12%), E. brunitti (12%), and E. maxima (10%). Prevalences did not vary by flock size. Also, neither the use of coccidiostat nor previous coccidiosis clinical outbreaks was associated with the prevalence of coccidiosis.

Salmonella contamination in commercial layer feed in Japan

A total of 4,418 samples of commercial layer feeds obtained in 1998 were investigated for the presence of salmonellae. A total of 146 strains of salmonellae which consisted of 32 serovars, including 20 strains of Salmonella Enteritidis, were isolated from 143 feed samples.

Epidemiological aspects of the use of live anticoccidial vaccines for chickens

This review address the epidemiology (epizootiology) of coccidiosis in commercial chickens with emphasis on the effects on the use of live vaccines. Surveys suggest that all seven valid species of chicken coccidia (Eimeria acervulina, Eimeria brunetti, Eimeria maxima, Eimeria mitis, Eimeria necatrix, Eimeria praecox and Eimeria tenella) are ubiquitous. All species are pathogenic to various extents. New results are presented on the pathogeneicities of E. acervulina, E. mitis and E. Praecox. Unless ingested by chickens, oocysts in poultry-house litter may die after about 3 weeks. Oocyst sporulation may be better in drier, rather than wetter, litter. Whether sporulated or not, up to 20% of ingested oocysts may pass undamaged through a chicken's intestine. The excreted, sporulated oocysts can be immediately reingested to initiate an infection; the unsporulated oocysts can still sporulate after passing through the intestine. The seven species differ in their times of appearance in commercial flock; hence particular vaccines may be designed for rearing standard broilers for up to about 6 weeks or for breeding stock. Attenuated, precocious lines of Eimeria in vaccines have low reproductive potentials, thus avoiding crowding, developing optimally, and stimulating immune response with minimal tissue damage. Cross-immunity between Eimeria species is probably minimal. There is reciprocity between the immune status of chicken and their excretion of oocysts for each species, ensuring continual stimulation of immune responses in birds on litter. Paracox vaccine, comprising all seven Eimeria species, is shown here to stimulate immunity to each of them independently. Total oocyst accumulation in litter following Paracox vaccination at 1 week comprises a small peak of vaccinal oocysts at 2-4 weeks, then a higher peak of the local virulent population at 4-7 weeks, which rapidly wanes. The attenuated drug-sensitive vaccinal oocysts probably interbreed with the corresponding wild species, reducing both virulence and drug-resistance in the local population. Anticoccidial vaccines may not induce complete immunity in chickens with lowered immunocompetence due to stressors, including certain viral disease. Future development of live vaccines for standard broilers may be expected in the relatively short term. The useful lives of anticoccidial drugs might be extended by rotating them with live vaccines.