Sampling times in micronucleus testing.

A series of micronucleus inducers were evaluated in the mouse bone marrow micronucleus test to determine if a 72-h sampling time enhances the sensitivity for detecting genotoxic agents. Male and female Swiss albino mice were dosed once with 7,12- dimethylbenz[a]anthracene, 6-mercaptopurine, benzo[a]pyrene, benzene, cyclophosphamide, 2-acetylaminofluorene, tubulazole, or mitomycin C. According to the EEC and OECD guidelines, the mice were killed at 24, 48 and 72 h after dosing. All test compounds induced an increase in the number of micronucleated polychromatic erythrocytes at 24 and/or 48 h. From the results obtained, it was evident that the 72-h sampling time does not enhance the sensitivity of the micronucleus test. The present data show that for screening purposes two sampling times at 24 and 48 h are sufficient to detect clastogens as well as aneugens. Although quantitative differences were found in sensitivity to micronucleus inducers between male and female mice, no qualitative differences were observed between the two sexes.

Efficacy of diclazuril against Eimeria dispersa in turkeys.

Diclazuril, a new anticoccidial drug, was tested for its efficacy against Eimeria dispersa in turkeys. A dose-titration study indicated that diclazuril at dosages of 0.5, 1, and 2 ppm in the feed was highly effective in terms of weight gain and suppression of lesions, abnormal droppings, and oocyst shedding.

Effect of diclazuril (Clinacox) on the development of protective immunity against Eimeria tenella: laboratory trial in broiler chickens.

The effect of diclazuril, fed to chickens at 1 ppm in the feed, was studied to determine whether the drug interfered with the development of immunity to Eimeria tenella. Group A was not treated, Groups B and C received diclazuril from Day 1 until Day 15, after which time the medicated feed was replaced by blank feed for the remainder of the experiment from Day 16 until Day 42. Immunization was performed in Groups A and B by artificial trickle infections with 2,000 sporulated oocysts per bird on Days 4, 6, 8, 11, and 13. On Day 29, a challenge infection was given using 200,000 oocysts per bird. The unmedicated birds (Group A) developed subclinical coccidiosis after the trickle infections with excretion of oocysts and a slightly decreased growth performance. At challenge, a good protective unimmunity was present, reflected by a good growth performance and a low oocyst excretion. The unimmunized birds (Group C) developed a severe clinical disease after challenge with high oocyst output, increased mortality, and poor growth performance. The diclazuril-medicated, trickle-infected birds (Group B) were well protected, both against the immunizing trickle infections and the challenge infection. After challenge, no clinical disease developed, although some lesions and oocyst excretion were present. It is concluded that, under the conditions of the trial, diclazuril did not significantly interfere with protective immunity formation against E. tenella.

Safety aspects of oral antifungal agents.

Four main targets have to be considered when evaluating the safety of new systemically acting, oral antifungals: the liver, the endocrine system, serum cholesterol and the developing embryo. The major endocrine targets for high levels of the antifungal azoles are the adrenal cortex and the gonads. Endocrine studies demonstrate that itraconazole has little potential for interfering with steroid hormones in man. Available data also indicate that itraconazole has low predictable hepatotoxicity potential in man. In rats, serum cholesterol levels are raised during treatment with itraconazole, especially after chronic exposure. This is, however, a species-specific phenomenon which leads to secondary events at toxic doses, especially in long-term toxicity studies. In man, including patients with existing hypercholesterolaemia, serum cholesterol levels are not raised. Ketoconazole has been shown to be teratogenic at high, toxic doses in pregnant rats. The same observation has been made for itraconazole, and it may also be true for fluconazole. However, all three azoles show no teratogenicity in the rabbit. Studies with itraconazole in adrenalectomised rats and in rats given exogenous arachidonic acid indicate that adrenal effects occurring at toxic dose levels are important mediators of teratogenicity. Since itraconazole does not affect adrenal function at levels used to treat infections in man, the teratogenic risk is estimated to be low. Itraconazole is therefore a promising new drug, especially with regard to the assessment of its safety in the liver and endocrine system. Moreover, it is more potent and has a broader antifungal spectrum than other azole antifungals, and its development is considered to be an important step forward in chemotherapy.

Anticoccidial efficacy of diclazuril in pheasants.

Diclazuril, a new anticoccidial drug, was tested in young pheasants artificially infected with the three most common pathogenic species of Eimeria, E colchici, E duodenalis and E phasiani. In two replicate experiments each with 40 birds the mortalities in the infected controls were 50 and 25 per cent. Diclazuril was administered in the feed at dose levels of 1, 2 and 4 ppm from the day before the inoculation of coccidia until the end of the test on day 6 after infection. The 1 ppm dose failed to inhibit the development of the parasite completely, as was shown by a reduction of the weight gain of the birds and the output of a small number of oocysts. Diclazuril at 2 or 4 ppm adequately controlled the infection, with weight gains similar to those of the uninfected controls. At all dose levels, mortality, intestinal lesions and diarrhoea were prevented.

Diclazuril, a new broad-spectrum anticoccidial for chickens. 3. Floor-pen trials.

Diclazuril is a benzeneacetonitrile showing great promise as a broad-spectrum anticoccidial agent for chickens, turkeys, and rabbits. The high anticoccidial activity of diclazuril in chickens, as first reported in dose-titration studies and battery trials, was confirmed in three floor-pen trials. The efficacy was demonstrated against six major pathogenic species of Eimeria after artificial infection with one or more species. The experimental data indicated that diclazuril, at dose levels of .5, .75, 1, and 2 ppm, had a high anticoccidial activity in terms of preventing mortality, suppressing or reducing lesion scores, and allowing for normal weight gains as well as productivity. The performances obtained with diclazuril was generally comparable with that of salinomycin at 60 ppm and that of lasalocid at 90 ppm.

Efficacy of diclazuril in the control of intestinal coccidiosis in rabbits.

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.

Efficacy of diclazuril against turkey coccidiosis in dose-titration studies.

Diclazuril, a new anticoccidial drug, was tested for its efficacy in turkeys against single Eimeria infections. Dose-titration studies indicated that diclazuril at dosages of 0.1, 0.5, 1, and 2 ppm was highly effective against the major pathogenic species-E. adenoeides, E. gallopavonis, and E. meleagrimitis-in terms of weight gain and suppression of lesions, abnormal droppings, and oocyst shedding.

Efficacy of diclazuril against turkey coccidiosis in a floor-pen experiment.

Diclazuril, a new anticoccidial drug, was tested for its efficacy in turkeys against mixed Eimeria infections. A floor-pen trial indicated that diclazuril at dosages of 0.5 ppm and 1 ppm in the feed was highly effective against the major pathogenic species E. adenoeides, E. gallopavonis, and E. meleagrimitis in suppressing intestinal and cecal lesions and oocyst shedding. Weight gain and feed conversion improved, particularly at 1 ppm.

Efficacy of diclazuril in the prevention and cure of intestinal and hepatic coccidiosis in rabbits.

The efficacy of diclazuril against intestinal and hepatic coccidiosis was studied in artificially infected rabbits. Prophylaxis against intestinal coccidiosis was evaluated using a mixed infection of Eimeria intestinalis, Eimeria magna and Eimeria perforans. Continuous medication in the feed at 1 p.p.m. was 100% effective in reducing oocyst output and faecal scores, and weight gain and feed efficiency were normal. Hepatic coccidiosis induced by Eimeria stiedai was prevented at 0.5 and 1 p.p.m. as shown by negative oocyst counts, normal liver weight, absence of liver lesions, and normal body-weight gain and feed efficiency. Medication at 1 p.p.m. for 7 consecutive days during the prepatent phase of hepatic coccidiosis resulted in large reductions in oocyst counts and lesion scores with a normal liver weight and growth performance. Diclazuril at 1 p.p.m. in the feed prevented both intestinal and hepatic coccidiosis in rabbits and can be advocated for safe mass medication.

Diclazuril, a new broad spectrum anticoccidial drug in chickens. 1. Dose titration studies and pilot floor pen trials.

Diclazuril, a new anticoccidial drug, was tested in poultry against six Eimeria species either in single species infections in dose titration studies or in mixed species infections in floor pen trials. The dose titration studies in cockerels indicated that diclazuril at dosages of 10, 5, 1, and .5 ppm was highly active against all major pathogenic species: E. tenella, E. acervulina, E. necatrix, E. brunetti, E. maxima, and E. mitis and effective in terms of weight gain and suppression of mortality, dropping scores, and oocyst counts. In two floor pen trials diclazuril was fed for 6 wk to broiler chickens experimentally infected either with E. tenella and E. acervulina or with E. necatrix and E. brunetti. Dose levels of 10, 5, and 1 ppm suppressed mortality and lesion scores. Even at 1 ppm the mean terminal body weight, feed conversion, and productivity index of treated birds were comparable to results for the uninfected, unmediated controls. In these pilot studies, involving 1,020 Hisex and 1,000 Hubbard broiler chickens, it has been demonstrated that diclazuril at the dose level of 1 ppm in the diet is an excellent anticoccidial without any adverse effects.

Diclazuril, a new broad spectrum anticoccidial drug in chickens. 2. Battery trials.

Battery trials have confirmed the broad spectrum anticoccidial activity of diclazuril as previously reported in dose titration studies. The advocated dose level of 1 ppm in the diet demonstrated excellent activity against the economically most important Eimeria species. At this dose level, body weight gains were comparable to those of uninfected, unmedicated controls and the oocyst production was negative in most species. Lesion scores and dropping scores were nil or highly reduced. An E. maxima-147 strain, less sensitive to ionophores, also responded well to diclazuril. It was concluded that diclazuril is a promising anticoccidial for the control of all species of coccidia that cause losses to the poultry industry.

Toxicological profile and safety evaluation of antifungal azole derivatives.

For the development of new systemically acting, oral antifungal azoles, it is of key importance to compare them with ketoconazole, the first available drug in this therapeutic class. Ketoconazole is a major breakthrough although hepatic side-effects as well as interactions with mammalian steroids might rarely occur during prolonged treatment. The prediction of these side-effects is difficult but the potential to interact with mammalian cytochrome P-450 enzymes is considered to be important. Therefore, for the selection of itraconazole a multidisciplinary approach was applied to study this potential. The present paper deals with the toxicological profile of itraconazole and its safety evaluation. In addition, a further comparison with ketoconazole and also with fluconazole is provided, in so far sufficient information is available. For the liver as a potential target organ, the available data indicate that itraconazole is not a predictable hepatotoxic drug in man. The major endocrine targets for overdosing with antifungal azoles are the adrenal cortex and the gonads. Endocrine studies show that itraconazole is not bearing a potential to interfere with steroid hormones in patients, which is a major improvement when compared to ketoconazole. In rats, elevation of serum cholesterol is observed especially after chronic exposure to itraconazole. This species-specific phenomenon leads at toxic dose levels to secondary events, especially in the long-term toxicity studies. In man, including those with existing hypercholesterolemia, serum cholesterol is not adversely affected by itraconazole. In pregnant rats, ketoconazole was shown to be teratogenic at high, toxic doses. The same observation has been made for itraconazole and this also might be true for fluconazole.(ABSTRACT TRUNCATED AT 250 WORDS)

Ultrastructural evaluation of the effects of diclazuril on the endogenous stages of Eimeria maxima and E. brunetti in experimentally inoculated chickens.

The ultrastructural morphology of the different endogenous stages of Eimeria maxima and E. brunetti was evaluated after oral treatment of inoculated chickens with a single dose of 5 mg/kg diclazuril. The drug induced no ultrastructural change in the growth or differentiation of the various schizont stages of both Eimeria spp. In E. maxima, the micromorphological appearance of micro- and macrogamonts developing from the blast from to maturation also remained unaffected by drug treatment. However, in all fertilized macrogamonts the normal pattern of oocyst wall establishment was completely disturbed, resulting in the formation of an abnormally thickened, incomplete oocyst wall and the necrosis of the zygote. In E. brunetti, the growth and nuclear division during microgametogenesis were not affected but differentiation was clearly abnormal. In comparison with the controls, this abnormal differentiation was characterized by a less extensive enlargement of the parasite surface area, aberrant morphological configurations of condensed heterochromatin, intracytoplasmic flagella formation, and glycogen accumulation. Finally, the complete degeneration of all microgamonts ensued. The growth and differentiation leading to mature macrogamonts was not disturbed; however, subsequent oocyst wall formation was largely precluded and the macrogamonts proceeded to degenerate completely. We conclude that diclazuril treatment primarily affected particular stages in the sexual development of both Eimeria spp., resulting in the complete eradication of these coccidian species.

In vivo action of the anticoccidial diclazuril (Clinacox) on the developmental stages of Eimeria tenella: a histological study.

Diclazuril, a new benzeneacetonitrile anticoccidial, has potent activity against various stages of Eimeria tenella. A single treatment of experimentally infected chickens during the prepatent phase (up to day 5) results in a complete interruption of the life cycle and oocyst shedding. The first- and second-generation schizonts show extensive degenerative changes that finally result in a complete loss of the parasitic stage. The degeneration is characterized by loss of internal structure, the appearance of many intracytoplasmic vacuoles, and incomplete merogony. The merozoites themselves show similar degenerative changes, including the presence of numerous small vacuoles in the cytoplasm. Diclazuril is also effective against both the micro- and macrogametocytes that have a ballooned appearance and loose their internal structure completely. In the macrogametocytes, wall-forming bodies either do not develop or disappear rapidly. Development of typical caecal lesions is prevented when treatment with diclazuril is initiated before large numbers of second-generation schizonts appear, i.e., day 3. It is concluded that diclazuril is lethal against both the asexual and the sexual stages of E. tenella. At the proposed use level of 1 ppm in the feed, the life cycle is interrupted at a very early stage and lesion development and oocyst shedding are completely prevented.

In vivo action of the anticoccidial diclazuril (Clinacox) on the developmental stages of Eimeria tenella: an ultrastructural evaluation.

A single 5-mg/kg oral dose of diclazuril affected both the asexual and sexual development of Eimeria tenella in experimentally inoculated chickens. In second-generation schizonts, early growth and nuclear divisions progressed normally, but a marked inhibition of merozoite formation was observed. Exogenesis of merozoites was largely prevented, whereas production of micronemes, amylopectin granules, and dense bodies and the formation of rhoptries, conoid, and pellicle continued. All these subcellular organelles accumulated, together with differentiated nuclei, within the main cytoplasmic mass. In the end, complete necrosis of the schizonts occurred. In macrogamonts, dilation of the rough endoplasmic reticulum around type II wall-forming bodies, fusion of type II wall-forming body contents, disturbance of the normal parallel arrangement of rough endoplasmic reticulum, and disruption of row formation of amylopectin granules became evident. In the microgamonts, normal evagination of microgametes was prevented; the flagellar complex formed within the main cytoplasmic mass and the differentiated nuclei remained present within the parasite body. The macro- and microgamonts also ended up in a stage of complete necrosis. These data indicate that diclazuril treatment primarily affects the normal differentiation of the respective endogenous stages during parasite development. This leads to complete degeneration of schizonts and gamonts indicating the lethal effect of this new anticoccidial compound.

Efficacy of flubendazole against gastrointestinal and lung nematodes in pigs.

Three trials were carried out on landrace pigs of various ages to assess the anthelmintic efficacy of flubendazole. The pigs were either artificially infected with Metastrongylus apri or naturally or artificially infected with the gastrointestinal nematodes Ascaris suum, Oesophagostomum dentatum or Hyostrongylus rubidus. For mass medication of young pigs and fatteners a dose regimen of 30 ppm flubendazole in the feed for 10 consecutive days was 100 per cent effective against the four nematode species. For individual medication a single dose of 5 mg/kg bodyweight administered in a small amount of feed was also 100 per cent effective. No side effects were observed.

Action of the anticoccidial clazuril on the endogenous stages of Eimeria labbeana and E columbarum in experimentally infected pigeons.

Racing pigeons were artificially infected with a mixed inoculum of Eimeria labbeana (85 per cent) and E columbarum (15 per cent) and treated orally with 2.5 mg clazuril either on day 1, 2, 3, 4, 5, 6 or 7 after infection. The impact of the treatment on the different developmental stages was evaluated by oocyst output and by histological examination of the duodenum and jejunum. The life cycle always became completely interrupted, but maximal effects were noted when treatment was given on day 4, 5 or 6 after infection. Treatment during patency completely interrupted oocyst excretion within three days after dosing. Degenerative changes in schizonts and gametocytes were always observed. The histology revealed a reduced number and abnormal structure of developing merozoites; a ballooned aspect and presence of numerous small vacuoles in the microgametocytes; the absence of typical wall-forming bodies in macrogametocytes and a complete absence of oocysts. It is concluded that clazuril has a coccidiocidal effect on the asexual and sexual developmental stages of both Eimeria species, resulting in a complete interruption of the life cycle.

[Clazuril: a new anticoccidial agent for pigeons]. / Clazuril: een nieuw anti-coccidiosemiddel voor duiven.

The effectiveness of clazuril (Appertex), a new anticoccidial agent for the treatment of pigeons is described in the present study. Clazuril, a benzene-acetonitrile derivative, is administered in a single dose. In laboratory studies, 121 carrier pigeons infected with E. labbeana and E. columbarum were treated once with clazuril in gelatin capsules at dose levels of 10 mg, 5 mg, 2.5 mg, 1.25 mg, 0.63 mg or with a placebo. When a single dose of 2.5 mg and higher was administered, all faecal samples became negative for oocysts within seven days after treatment. In the field studies, 1531 young and full-grown carrier pigeons, from 116 infected dove-cotes, were treated with 1 tablet of 2.5 mg clazuril. Seven days after treatment, the faecal samples of 105 dove-cotes were negative for oocysts of E. Labbeana and E. columbarum; in six dove-cotes, infection was also virtually reduced to zero. Performance in racing was not affected by treatment and side-effects were not observed.