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A summary is presented of the present situation in coccidiosis control in poultry, regarding the use of anticoccidial drugs and of therapeutics. Also attention is payed to the development of vaccines, which usage is limited up till now. Monitoring the incidence of coccidiosis will be necessary in future to enable efficient use of anticoccidial drugs and therapeutics.
In an effort to develop an attenuated coccidiosis vaccine against coccidiosis, we exposed Eimeria maxima oocysts to an optimum dose of gamma irradiation (17 kRad) that does not affect sporozoite invasion of the intestinal mucosa but does prevent asexual parasite development. Irradiated E. maxima oocysts were suspended in gelatin slabs and placed in battery cages for ingestion by 1-day-old chickens. Separate groups of chickens were given gelatin slabs containing nonirradiated E. maxima oocysts or were inoculated per os with either irradiated or nonirradiated E. maxima oocysts. Chickens infected with irradiated or nonirradiated oocysts by either oral inoculation or gel delivery showed a dose-dependent protection against weight loss associated with E. maxima challenge compared with unimmunized controls. In general, nonirradiated oocysts elicited protective immunity at lower immunization doses compared with irradiated oocysts. These experiments were extended to a floor pen study wherein 1-day-old male and female broiler chickens were given irradiated or nonirradiated E. maxima oocysts in gelatin slabs in hatching boxes and challenged at 4 wk of age. A significant reduction (P < 0.05) in lesion scores was observed for chickens immunized with either irradiated or nonirradiated oocysts compared with unimmunized controls. Although no significant difference (P > 0.05) was observed in weight gain between these groups, both male and female chickens inoculated with irradiated E. maxima oocysts showed about a 10% greater weight gain than unimmunized controls. For both male and female chickens, average weights at challenge were greater in groups that were immunized with 17-kRad-irradiated E. maxima oocysts compared with those animals immunized with nonirradiated oocysts.
Coccidiosis is caused by infection with Eimeria spp. The disease is responsible for major economic loss to the poultry industry unless infections are controlled by anticoccidial drugs. John Ellis and Fiona Tomley discuss recent research on the characterization and cloning of antigens from Eimeria spp and advances towards the development of genetically engineered vaccines against poultry coccidiosis.
Avian coccidiosis, caused by parasites of the genus Eimeria, is a major disease of intensively reared poultry. Anticoccidial drugs, and vaccines based on live wild-type (virulent) parasites, have aided the management of coccidiosis, but the development of vaccines based on live attenuated parasites has been a significant advance. Here, Martin Shirley and Petr Bedrník explain the basis of these recent vaccines and discuss their use.
This report describes a case of granulomatous endometritis caused by coccidiosis in an immunologically uncompromised 63 year old patient. The glandular epithelium of the endometrium contained numerous intracytoplasmic cysts, corresponding to periodic acid Schiff positive and methenamine silver negative sporoblasts. The endometrial glands revealed reactive phenomena, such as eosinophilic and squamous glandular metaplasia and intraluminal desquamation. Non-necrotising epithelioid granulomata, lacking the presence of parasites, were present in the stroma. Although not detected in the stool examination, the organisms were probably Isospora belli. There was no evidence of other foci of the disease. Coccidiosis should be differentiated from the more commonly occurring coccidiomycosis.
Coccidia were found in a patient suffering from malabsorption syndrome. In addition, immunologic investigation showed combined humoral and cellular immunodeficiency. Treatment with metronidazole induced the disappearance of coccidia from the stool and clinical remission. Six months later, the patient was seen with acute lymphoproliferative disease and died thereafter. The possible relationship between malabsorption, immunodeficiency, coccidiosis, metronidazole, and malignancy is reviewed.
We have established a fluorescence-based electrophoretic approach for the specific identification of all seven currently recognised species of Eimeria infecting chickens. The second internal transcribed spacer (ITS-2) of ribosomal DNA is amplified by polymerase chain reaction (PCR) from any of the seven species using a single set of oligonucleotide primers (of which the reverse one is fluorescently labelled). The amplicons are heat-denatured, subjected to denaturing polyacrylamide gel electrophoresis in a 377 DNA sequencer (ABI). The chromatograms produced are stored electronically and then analysed using GeneScan 3.1 software. Using control DNA samples representing monospecific lines of Eimeria, regions in the chromatograms have been defined for the specific identification of each of the seven species, although some variation in the chromatograms (reflecting population variation) was detectable within two species. Electrophoretic reading and analysis is carried out automatically using a computer imaging system, thus making it a time- and cost-effective approach. It is well suited for high-throughput diagnostic screening of oocyst samples and should find applicability as a tool for prevalence studies, monitoring of coccidiosis outbreaks and the quality control of vaccines.
An investigation was made of the relationship between the water and food consumption of healthy and sick chickens Using coccidiosis as a disease model, and uninfected chickens as healthy controls, male birds of an egg-production breed and males and females of a meat-production breed were found to have simultaneously reduced water and food intakes 4 days after infection with Eimeria acervulina or E. maxima, and from 4 to 6 days after infection with E. tenella. This phenomenon was associated with reduction of weight gains and poor food conversion ratios. Whether birds were healthy or sick, and regardless of the degree reduction of dietary intake, there was a more or less constant relationship between their food and water consumption. The ratio of the weights of water and food consumed had a value of about 1.9, with a range of 1.1-2.4. It is concluded that neither water nor food has an advantage over the other as a vehicle for chemotherapy. However, other factors, such as case and speed of administration, and avoidance of adsorption onto food particles, favour the drinking-water route.
Data published since 1940 on the use of drugs to prevent or treat ovine coccidiosis are presented in the form of tables. These highlight the differences in conditions of husbandry and mode of administration. Such differences partly account for the variability of response to medication. Drugs that have proved useful under certain conditions include amprolium, monensin and lasalocid for prevention, and sulphonamides for treatment.
The activities of the drug metabolizing enzymes aminopyrine-N-demethylase, aniline hydroxylase and UDP-glucuronyl transferase, together with protein concentration, were measured in liver microsomes and duodenal mucosa from healthy chickens and chickens experimentally infected with Escherichia coli endotoxin, or naturally infected with Eimeria necatrix and Eimeria tenella (clinically classified as slight, moderate or severe infections). E. coli (2 mg/kg, 3 days) and severe coccidiosis significantly decreased the activities of the three enzymes in the liver and duodenum. However, infection by the E. coli endotoxin at lower doses (0.5 and 1 mg/kg, 3 days) and moderate or slight coccidial infections had no significant effect on the activities of these enzymes. Neither E. coli nor coccidial infections significantly affected the liver/body weight ratio. However, infection with the E. coli endotoxin (2 mg/kg, 3 days) and the moderate or severe coccidial infections significantly reduced microsomal protein concentration in the liver.
For several reasons, we are convinced that the parasitologist community must look again at porcine neonatal coccidiosis. We find it surprising that this disease is seldom addressed, and that assumptions are not always supported by clinico-epidemiological analysis. For example, the relationship between diarrhoea and the excretion of oocysts during experimental infection versus field infection is not questioned. Lindsay et al. review parasitological knowledge of this disease in the latest (1999) edition of Diseases of swine. Although this paper is divided into two parts, we have three distinct objectives: (1) to bring to the debate our experience in the medical control of this disease; (2) to propose a diagnostic methodology; (3) to raise some questions on various clinical, epidemiological and parasitological unknowns.
The therapeutic efficacy of sulphachlorpyrazine and toltrazuril against experimentally induced Eimeria tenella infection was compared in battery and floor pen raised broiler chickens. In the battery studies, both drugs prevented coccidiosis-related mortality and decrease of weight gain to a similar degree, but toltrazuril was more effective in reducing intestinal lesions and faecal scores, when treatments were initiated 24 h postinfection. When medication was delayed until 72 h after inoculation, the sulphonamide proved to be more effective in preventing reduction of weight gain and intestinal lesions caused by the parasites. Under simulated use conditions both drugs showed an appropriate anticoccidial efficacy without major differences between them.
Development of cell-mediated immunity (CMI) and comparative effectiveness of different stage-specific coccidia antigens in T cell activation during avian coccidiosis were evaluated in two inbred strains of chickens using a specific in vitro T cell proliferation assay. Lymphocytes from chickens infected with different Eimeria spp. showed proliferative response to sporozoites, merozoites or Eimeria soluble antigen (Esa) excreted by cultured parasites. Detectable CMI response was observed at 21 day P.I. in chickens infected with E. tenella and E. maxima. Generally lower T cell response was observed in chickens infected with E. acervulina. Merozoites were highly immunogenic compared to sporozoites. Esa prepared from cultured parasites was as effective as whole parasites in evoking a T cell response. Although strain variation in T cell response to parasites or Esa was observed during a primary infection, substantially enhanced T cell response was observed 3 days after a secondary infection in both strains of chickens. The results of the present investigation suggest that Esa may be a major parasite antigen released to the immune system during early stages of infection and relevant to the development of protective immunity.
Floor-pen studies were conducted to ascertain whether coccidiosis could be prevented by using a drug added to the litter to preclude coprophagia and ingestion of infective oocysts. An experimental drug (1-pyrrolidinebutyramide, 2-methyl-alpha,alpha-diphenyl) was added to litter contaminated with sporulated Eimeria tenella oocysts. Thereafter 7-day-old broiler chicks were reared on the litter for a nine-day period. Mortality, lesion scores and dropping scores were the criteria selected to determine efficacy. Treatment of the litter at the lowest level (2.3 g kg-1) did not reduce the incidence or severity of the disease, whereas treatment at two higher levels (11.5 and 23.0 g kg-1) significantly reduced both (incidence and severity). The highest level was the most efficacious; however, drug toxicity was also encountered at this level.
The epizootiology of ovine coccidiosis caused by Eimeria ahsata was studied in four flocks in the province of León (Spain), between January 1978 and December 1979. The intensity of infection was found to be 25.5 +/- 1.7% and was similar in winter and spring. Eimeria ahsata was the most common species in 83.1% of the 1620 samples examined. It was also found in 86.2% of the animals examined. Only 0.3% of the positive samples contained oocysts of a single species, and samples containing four species were the most frequent (19%). Twenty-three percent of samples contained five species and 31.3% contained six species.
The anticoccidial efficacy of diclazuril was studied in rabbits artificially infected with Eimeria flavescens, Eimeria intestinalis, Eimeria magna and Eimeria perforans. Continuous administration at 1 and 2 ppm in pelleted feed proved to be highly efficacious in controlling oocyst output and faecal scores. The weight gain was comparable and the feed efficiency slightly improved compared with the non-infected, non-medicated controls, and clinical signs were fully prevented. Medication of rabbits at 0.5 ppm also provided a significant improvement in all parameters compared with the infected, non-medicated controls. In order to obtain 100% effectiveness in the control of intestinal coccidiosis in rabbits, continuous medication at 1 ppm is recommended.
Nine thousand commercial breeder chicks (Chankee) reared in a floor pen were exposed to restricted numbers of Eimeria tenella and E. necatrix oocysts to confer immunity. Antibody induction in these chicks was examined by the enzyme-linked immunosorbent assay (ELISA) with antigen prepared from E. tenella oocysts. The oocyst excretion pattern demonstrated recycled infections which continued in these chicks for greater than or equal to 22 days after exposure. Antibody levels in their sera, as determined by the mean absorbence values in ELISA, increased gradually up to 38 days post-inoculation. Mean absorbence values of sera from control chicks remained at a low level. When infected and control chicks were challenged with the two species of coccidia, the test chicks were protected against both species. The antibody level did not change for 8 days in the challenge groups, while in the control chicks, absorbence in ELISA rose significantly and the mean absorbence value was higher than that in immunized chicks. Some factors which influence the results of ELISA are considered and the applicability of this method to measuring immunity against coccidiosis in chickens is discussed.
Coccidiosis is a protozoan disease of wild and domestic ruminant animals in every country of the world. This article provides basic information regarding the terminology, biology, epidemiology, pathology, diagnosis and control methods applicable to the causative agents and their interaction with host animals.