Comparative testing of anticoccidials in broiler chickens: the role of coccidial lesion scores

Characterization of coccidiosis and evaluation of suggestive cases of subclinical necrotic enteritis in broilers

ABSTRACT: This study performed the characterization of coccidiosis in broilers and evaluated the occurrence of suggestive cases of necrotic enteritis (NE), seeking if there is an association between the diseases in Brazilian flocks. Two hundred and fifty-six birds from 32 flocks were evaluated. Macroscopic and histopathological lesions were graduated for coccidiosis and NE. Intestinal content was investigated by polymerase chain reaction (PCR) for seven species of Eimeria and by selective anaerobic culture for Clostridium perfringens and identification of the NetB gene. Flocks positive for coccidiosis represented 93.8%. Macroscopic lesions of coccidiosis were Grade 1 for E. acervulina (27%); E. tenella (9.7%) and E. maxima (8.9%). Histopathological evaluation showed Grade 1 in duodenum (38.2%); jejunum (21.4%); cecum (9.3%) and ileum (5%). PCR demonstrated positivity for E. tenella (21.9%), E. maxima (18.8%), and E. acervulina (3.1%). Suggestive macroscopic lesions of necrotic enteritis ranged from Grade 1 (16%), 2 (23%) and 3 (10,9%). Histopathology indicated the absence of necrosis, showing only hemorrhage in the mucosa and submucosa, with the presence of Eimeria spp. Clostridium perfringens type A netB+ was not isolated, demonstrating that macroscopic lesions found mostly in the jejunum did not characterize NE, based on histopathology and negativity of the NetB gene. The study suggests that, due to the high occurrence of coccidiosis, many macroscopic findings suggestive of NE are, in fact, attributed to atypical lesions caused by the reproduction of Eimeria spp.

Anticoccidial activity of natural plants extracts mixture against Eimeria tenella: An in vitro and in vivo study

Coccidiosis, an acute epidemic intestinal disease of poultry, is caused by the parasitic protozoan genus Eimeria, with Eimeria tenella being the most pathogenic spp. Novel approaches are required to address the limitations of current treatments for this disease. We investigated the effects of eight plant extracts and essential oils and their mixture on Eimeria tenella as potential treatments for coccidial infection. The anticoccidial effects of non-toxic concentrations of Punica granatum L. (0.005 mg/mL), Plantago asiatica L. (0.780 mg/mL), Bidens pilosa L. (0.390 mg/mL), Acalypha australis L. (0.390 mg/mL), Pteris multifida Poir (0.050 mg/mL), and Portulaca oleracea L. sp. Pl. (0.050 mg/mL) extracts; Artemisia argyi Levl. et Vant. (0.010 μL/mL) and Camellia sinensis (L.) O. Ktze (0.050 μL/mL) essential oils; and their mixture (0.500 mL/mL) on Eimeria tenella were determined using cell viability assays, flow cytometry, and in vivo studies. The eight plant extracts and essential oils and their mixture inhibited Eimeria tenella sporozoites from invading chicken embryo fibroblast cells in vitro. The extract and essential oil mixture improved the feed conversion ratio and body weight gain, reduced fecal oocyst excretion, substantially reduced the mortality of Eimeria tenella-infected chickens, and reduced Eimeria tenella-induced cecal damage in vivo. The results suggest that the extract and essential oil mixtures inhibit Eimeria tenella invasion both in vitro and in vivo, demonstrating their potential as anticoccidial agents.

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

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

Starving for nutrients: anorexia during infection with parasites in broilers is affected by diet composition

In 2 experiments, we investigated whether diet composition plays a role in pathogen-induced anorexia, the voluntary reduction in ADFI during infection in broilers. We hypothesized that either energy or CP dietary content could influence the extent of anorexia in Ross 308 broilers and infection outcomes with Eimeria maxima. From d 13 of age, half of the birds were infected, and half were uninfected. ADFI was measured daily, and BW every 3 d until d 29. Oocyst excretion was measured daily from d 17 to 23. The impact of parasitism on the small intestine was assessed on d 19 and 25. In Experiment 1, 336 birds were offered diets progressively diluted with lignocellulose, starting from a diet with 3,105 (kcal ME/kg) and 20% CP. There was a significant interaction between infection and diet on ADFI during the acute stage of infection (d 17 to 21): for control birds diet dilution decreased ADFI and consequently reduced energy and CP intake. For infected birds, diet dilution increased ADFI, leading to the same energy and CP intake across diets. Oocyst excretion and villi length to crypt depth ratio (VCR) were constant across infected treatments. In Experiment 2, 432 birds were offered diets with constant ME (3,105 kcal/kg), but different CP contents (24, 20, 26, and 12%). Infection significantly reduced ADFI. Although there was no interaction between infection and diet on ADFI, there was an interaction on CP intake during the acute stage of infection. Infected birds on the 20% CP diet achieved the same CP intake as uninfected birds. There were no differences in the VCR and ADG of the infected birds on 24, 20 and 16% CP treatments, but birds on 12% had the lowest ADG and excreted more oocysts. We suggest that during infection, birds target a nutrient resource intake, which appears to be beneficial for infection outcomes, while at the same time they avoid excess protein intake. We conclude that different mechanisms regulate ADFI in infected and uninfected birds.

Effect of Pistacia lentiscus L. Vegetable Oil on Growth Performance and Coccidiosis in Broiler Chickens: In vitro and In vivo Assessment

This study aims to assess the ability of vegetable oil of Pistacia lentiscus L. (lentiscus oil) in stimulating growth performance of broiler chickens and protecting them against coccidiosis. For this purpose, an in vitro test was first carried out to evaluate the destructive effect of this oil on Eimeria spp oocysts. On the other hand, an in vivo study was carried out to evaluate, once again, the capacity of the vegetable oil of Pistacia lentiscus L. in stimulating broilers growth performance and reducing the coccidiosis clinical signs. Thus, day old chicks were randomly divided into four equal groups: (1) uninfected and not-supplemented control (NI NS); (2) uninfected and supplemented (NI S); (3) infected and not supplemented (I NS); (4) infected and supplemented (IS). Each group was divided into three replicates containing each of them two subjects. The experimental groups (2 and 4) are supplemented with lentiscus oil by force-feeding at the rate of 1 mL per day from the 18th day until the end of the experiment. The chicks of the third and the fourth group are inoculated orally with sporulated oocysts (6.5 × 105 oocysts of Eimeria spp) on the day 20 of age. The results showed that lentiscus oil has an anticoccidial dose-dependent effect as shown by oocysts counting and released substances measurement at 273 nm. The growth performance of the (NI S) group was found better with an improvement percentage of 9.14% compared to the control (p < 0.05). Likewise, the weight gain of the (I S) group seems slightly higher than that of the control one (1316 g and 1235 g, respectively) (p < 0.05). In conclusion, the vegetable oil of Pistacia lentiscus L. has shown, not only, a promising growth effect in broiler chickens, but also, it seems to have a protective effect against coccidiosis sequels caused by Eimeria acervulina infection.

Research Note: Evaluating fecal shedding of oocysts in relation to body weight gain and lesion scores during Eimeria infection

Coccidiosis has been a pervasive disease within the poultry industry, with test parameters used to measure effectiveness of treatment strategies often being subjective or influenced by non-disease-related activity. Four experiments were completed, which examined several test parameters of coccidiosis, including body weight gain (BWG), lesion scores, and oocysts per gram of feces (OPG). Each experiment included at least 2 parameters for measuring coccidial infection in chickens and turkeys. In experiment 1, an inoculated control was measured against 3 anticoccidial groups, whereas in experiments 2 to 4, noninoculated and inoculated controls were compared via BWG and OPG. Lesion scores were also included in experiments 1, 3, and 4. Experiment 4 resulted in high correlation, via Pearson correlation coefficient, between BWG and OPG (r = -0.69), very high correlation between OPG and lesion score (r = 0.86), and moderate correlation between BWG and lesion score (r = -0.49). Lesion scores proved to be effective in confirming Eimeria infection, although they did not correlate well with BWG or OPG. Each parameter tended to provide more useful information when lined up with the Eimeria life cycle. Incorporation of OPG, with BWG and lesion scores, as test parameters to measure coccidiosis intervention strategies, provides a global description of disease that may not otherwise be observed with the 2 latter measurements alone.

The effect of microbial challenge on the intestinal proteome of broiler chickens

Background

In poultry production intestinal health and function is paramount to achieving efficient feed utilisation and growth. Uncovering the localised molecular mechanisms that occur during the early and important periods of growth that allow birds to grow optimally is important for this species. The exposure of young chicks to used litter from older flocks, containing mixed microbial populations, is a widely utilised model in poultry research. It rarely causes mortality but effects an immunogenic stimulation sufficient enough to cause reduced and uneven growth that is reflective of a challenging growing environment.

Methods

A mixed microbial challenge was delivered as used litter containing Campylobacter jejuni and coccidial oocysts to 120 male Ross 308 broiler chicks, randomly divided into two groups: control and challenged. On day 12, 15, 18 and 22 (pre- and 3, 6 and 10 days post-addition of the used litter) the proximal jejunum was recovered from 6 replicates per group and differentially abundant proteins identified between groups and over time using 2D DiGE.

Results

The abundance of cytoskeletal proteins of the chicken small intestinal proteome, particularly actin and actin associated proteins, increased over time in both challenged and control birds. Villin-1, an actin associated anti-apoptotic protein, was reduced in abundance in the challenged birds indicating that many of the changes in cytoskeletal protein abundance in the challenged birds were as a result of an increased rate of apoptosis. A number of heat shock proteins decreased in abundance over time in the intestine and this was more pronounced in the challenged birds.

Conclusions

The small intestinal proteome sampled from 12 to 22 days of age showed considerable developmental change, comparable to other species indicating that many of the changes in protein abundance in the small intestine are conserved among vertebrates. Identifying and distinguishing the changes in proteins abundance and molecular pathways that occur as a result of normal growth from those that occur as a result of a challenging microbial environment is important in this major food producing animal.

Antibody expressing pea seeds as fodder for prevention of gastrointestinal parasitic infections in chickens

BACKGROUND

Coccidiosis caused by protozoans of genus Eimeria is a chicken parasitic disease of great economical importance. Conventional disease control strategies depend on vaccination and prophylactic use of anticoccidial drugs. Alternative solution to prevent and treat coccidiosis could be provided by passive immunization using orally delivered neutralizing antibodies. We investigated the possibility to mitigate the parasitic infection by feeding poultry with antibody expressing transgenic crop seeds.

RESULTS

Using the phage display antibody library, we generated a panel of anti-Eimeria scFv antibody fragments with high sporozoite-neutralizing activity. These antibodies were expressed either transiently in agrobacteria-infiltrated tobacco leaves or stably in seeds of transgenic pea plants. Comparison of the scFv antibodies purified either from tobacco leaves or from the pea seeds demonstrated no difference in their antigen-binding activity and molecular form compositions. Force-feeding experiments demonstrated that oral delivery of flour prepared from the transgenic pea seeds had higher parasite neutralizing activity in vivo than the purified antibody fragments isolated from tobacco. The pea seed content was found to protect antibodies against degradation by gastrointestinal proteases (>100-fold gain in stability). Ad libitum feeding of chickens demonstrated that the transgenic seeds were well consumed and not shunned. Furthermore, feeding poultry with shred prepared from the antibody expressing pea seeds led to significant mitigation of infection caused both by high and low challenge doses of Eimeria oocysts.

CONCLUSION

The results suggest that our strategy offers a general approach to control parasitic infections in production animals using cost-effective antibody expression in crop seeds affordable for the animal health market.

High hydrostatic pressure and UV light treatment of produce contaminated with Eimeria acervulina as a Cyclospora cayetanensis surrogate

The prevalence, size, genome, and life cycle of Eimeria acervulina make this organism a good surrogate for Cyclospora cayetanensis, a protozoan that causes gastroenteritis in humans, including recent outbreaks in the United States and Canada associated with contaminated raspberries and basil. Laboratory studies of C. cayetanensis are difficult because of the lack of readily available oocysts and of infection models and assays. UV radiation and high-hydrostatic-pressure processing (HPP) are both safe technologies with potential for use on fresh produce. Raspberries and basil were inoculated with sporulated E. acervulina oocysts at high (10(6) oocysts) and low (10(4) oocysts) levels, and inoculated and control produce were treated with UV (up to 261 mW/cm2) or HPP (550 MPa at 40 degrees C for 2 min). Oocysts recovered from produce were fed to 3-week-old broiler chickens, which were scored for weight gain, oocyst shedding, and lesions at 6 days postinoculation. Oocysts exhibited enhanced excystation on raspberries but not on basil. Birds fed oocysts from UV-treated raspberries had reduced infection rates, which varied with oocyst inoculum level and UV intensity. Birds fed oocysts from UV-treated raspberries (10(4) oocysts) were asymptomatic but shed oocysts, and birds fed oocysts from UV-treated basil (10(4) oocysts) were asymptomatic and did not shed oocysts. Birds fed oocysts from HPP-treated raspberries and basil were asymptomatic and did not shed oocysts. These results suggest that UV radiation and HPP may be used to reduce the risk for cyclosporiasis infection associated with produce. Both treatments yielded healthy animals; however, HPP was more effective, as indicated by results for produce with higher contamination levels.

World Association for the Advancement of Veterinary Parasitology (WAAVP) guidelines for evaluating the efficacy of anticoccidial drugs in chickens and turkeys

These guidelines have been written to aid in the design, implementation and interpretation of studies for the assessment of drug efficacy against Eimeria species in chickens and turkeys. The information provided deals with many aspects of how to conduct controlled studies in battery cages (dose determination), floor pens (dose confirmation), and commercial facilities (field effectiveness studies), the selection of birds, housing, feeding, preparation of medicated rations, record keeping, diagnostic techniques, and methods for the preparation, maintenance and use of parasites. These guidelines are also intended to assist investigators in conducting specific studies, provide specific information for registration authorities involved in the decision-making process, assist in the approval and registration of new anticoccidial drugs, and facilitate the world-wide adoption of standard procedures.

Resistance to anticoccidial drugs of Dutch avianEimeriaspp. field isolates originating from 1996, 1999 and 2001

Fifteen Eimeria spp. field isolates sampled on Dutch broiler farms were subjected to an Anticoccidial Sensitivity Test (AST) in a battery cage study. Four isolates dated from 1996, another four from 1999 and the last seven isolates from 2001. The selected anticoccidial drugs were monensin, narasin, salinomycin, lasalocid, nicarbazin, diclazuril, halofuginone, maduramicin and meticlorpindol/methylbenzoquate. Maduramicin and halofuginone were not included in the ASTs of 1999 and 2001, while meticlorpindol/methylbenzoquate was not tested in 1996 and 1999. Eimeria acervulina present in each of the four 1996 field isolates showed resistance for almost all products tested except maduramicin (1/4) and salinomycin (114), which appeared to be reduced sensitive. In 1999 the same species presented a similar resistance pattern for most products, although reduced sensitivity occurred for salinomycin (1/4), and sensitivity was found for diclazuril (2/4), monensin (1/4) and narasin (1/4). In the year 2001 increased sensitivity to various products was found. Higher sensitivity was found for meticlorpindol/ methylbenzoquate (7/7) and salinomycin and narasin (both 4/7), followed by nicarbazin (3/7) and monensin (2/7). Reduced sensitivity was found for monensin (3/7), lasalocid (2/7), salinomycin and narasin (1/7). E. maxima was only found in one field isolate per year. The E. maxima from 1996 was resistant to all products except narasin (sensitive) and halofuginone (reduced sensitive). In 1999 this species was reduced sensitive to narasin and lasalocid, showing resistance for the other products. The strain originating from the 2001 isolate was reduced sensitive to most products except monensin and narasin (resistant). Full sensitivity was found for meticlorpindol/ methylbenzoquate. E. tenella was present in one isolate of 1996, two of 1999 and four isolates of 2001. The AST of 1996 showed reduced sensitivity for nicarbazin, and sensitive to narasin, maduramicin and halofuginone. All other products showed resistance. In 1999 both strains showed resistance to all products tested. For the year 2001 full sensitivity was found to meticlorpindol/methylbenzoquate. Sensitivity was also found for salinomycin (1/4), nicarbazin (2/4), diclazuril (2/4) and lasalocid (2/4), monensin (1/4) and narasin (1/4). Reduced sensitivity was found for nicarbazin (1/4), lasalocid (1/4) and narasin (1/4). The different resistance patterns of Dutch coccidiosis isolates and resistance of coccidia in general is discussed.