Sensitivity of field isolates of Eimeria tenella to anticoccidial drugs in the chicken

Thirty isolates of Eimeria tenella obtained from broiler and breeder farms were examined for their sensitivity to anticoccidial drugs. All were sensitive to robenidine, 28 were sensitive to methyl benzoquate, 25 to clopidol and 21 to nicarbazin. Most isolates were resistant or partly resistant to amprolium and dinitolmide.     

A survey of sensitivity to anticoccidial drugs in 60 isolates of coccidia from broiler chickens in Brazil and Argentina

Coccidia were isolated from 90 broiler farms in 15 poultry-producing areas in Brazil and Argentina. Sixty isolates were tested for sensitivity to 7 anticoccidial drugs. The common species were: a) Eimeria tenella, 47 isolates; b) E. maxima, 49 isolates; c) E. acervulina, 44 isolates; d) E. mitis, 26 isolates; and e) E. brunetti, 12 isolates. Isolates were considered sensitive to drugs if intestinal lesion scores of medicated broilers were reduced by at least 50% compared with unmedicated infected broilers or if weight gain was at least 75% of that of uninfected birds in a 6-day laboratory test. According to lesion scores, there was evidence of resistance or seriously reduced sensitivity to monensin in 20 isolates, narasin in 29, salinomycin in 11, maduramicin in 1, clopidol in 36, amprolium in 40, and nicarbazin in 1. According to broiler weight gain, there was resistance to monensin in 36 isolates, narasin in 32, salinomycin in 28, maduramicin in 2, clopidol in 28, amprolium in 50, and nicarbazin in 4. These results suggested incomplete cross resistance of coccidia to polyether ionophorous drugs. The degree of resistance might be explained by previous patterns of use of these drugs.     

我国田间鸡球虫耐药性现状与控制对策

鸡球虫病是严重危害养鸡业发展的重要疾病之一,长期以来该病的防治主要依赖药物,由于抗球虫药的长期应用,使得鸡球虫耐药性的产生成为无法避免的问题。本文就近年来我国田间球虫耐药性的现状进行了分析与总结,对耐药性的检测方法与控制对策等的研究进展进行了综述,旨为减少球虫的耐药性,更好地防治鸡球虫病提供科学依据。     

三种鸡抗球虫药的效力比较试验

鸡球虫病是养禽业中常见的一种疾病,它对养鸡生产的危害十分严重,分布很广。在我国抗球虫药物的种类很多,但由于球虫耐药性的普遍存在,抗球虫应用效果不是很理想。试验通过挑选健康雏鸡随机分组,在人工感染鸡柔嫩艾美耳球虫条件下,评估3种抗球虫药物(磺胺氯吡嗪钠、马杜拉霉素、盐酸氯丙嗪)的抗球虫效果,并对3种抗球虫药物进行比较,以抗球虫指数(ACI)作为药物治疗效果的综合评定指标,为规模化养鸡场提供试验依据,以适应生产实际需要。     

Studies on the mode of action of anticoccidial drugs in the chicken and chicken embryo

Delayed treatment has been used to investigate the activity of anticoccidials against the Houghton strain and an embryo-adapted strain of E. tenella. The results show that in chicken embryos the effect of the quinolones and clopidol depends upon the concentration of drug employed. The earlier stages in the life cycle appear to be intrinsically more vulnerable to the action of these drugs. In the chicken, the activity of amprolium was restricted to early stages in the life cycle, but in the chicken embryo, where development is restricted to the thin chorioallantoic membrane, all stages present up to 72 h after inoculation were equally affected. Absorption and distribution may, therefore, limit the action of amprolium in the chicken. Robenidine and sulphaquinoxaline were equally active up to 72 h post inoculation in chickens and chicken embryos, suggesting that absorption and distribution do not limit the activity of these drugs.     

The effect of ionophore anticoccidial agents on coccidia isolated in field conditions 1984-1985

Out of six isolates of coccidia of the species Eimeria tenella, obtained in the years 1984 and 1985 on farms with a stationary occurrence of coccidiosis, five were found to have reduced sensitivity or resistance to monensin. Neither were these isolates sensitive to further monovalent ionophorous anticoccidials narasin and salinomycin. The bivalent ionophorous anticoccidial lasalocid controlled five isolates completely, but for one its effectiveness was reduced. An isolate obtained on a farm with long-term absence of coccidiosis was sensitive to all anticoccidial drugs.     

Efficacy of ionophorous anticoccidial drugs against coccidia in farm-reared pheasants (Phasianus colchicus) from Illinois

Litter samples obtained from a ring-necked pheasant propagation farm in Illinois contained coccidia: 57.5% of the oocysts were Eimeria duodenalis, 24.9% were E. tetartooimia, 8.8% were E. phasiani, and 8.8% were E. pacifica. Ionophorous anticoccidial drugs were tested for efficacy against the pheasant coccidia. All three drugs reduced oocyst production and prevented mortality in young pheasants; unmedicated infected controls had a 40% mortality rate. Monensin at 120 ppm in the feed was coccidiocidal against E. duodenalis and E. tetartooimia, partly coccidiocidal against E. pacifica, and only partly coccidiostatic against E. phasiani. Salinomycin at 60 ppm in the feed was highly efficacious and coccidiocidal against all four species, but the salinomycin-medicated pheasants gained the least of all medicated birds. Lasalocid at 120 ppm in the feed was the most effective, with nearly complete coccidiocidal activity against all four coccidial species.     

Efficacy of maduramicin against ionophore-tolerant field isolates of coccidia in broilers

Maduramicin ammonium was given at 2.5-8 ppm in the feed to broilers experimentally infected with coccidia recently isolated from broiler farms where ionophores had been used for several years. Infection pressure varied from mild to severe in five trials: mortality in unmedicated controls ranged from 0 to 59%, intestinal lesion scores were high, and weight gain was depressed by the infections. The cultures of Eimeria were partly resistant to ionophores: birds medicated with monensin at 100-121 ppm had only modest reductions in lesion scores and incomplete protection against weight loss or mortality. Control of infections by maduramicin was significant at 4 ppm but best at 5-7 ppm. Maduramicin was more effective than monensin or narasin, but about the same as salinomycin, in reducing lesions and mortality and in protecting performance. Maduramicin was well tolerated within the dose range of 5-7 ppm.     

柔嫩艾美耳球虫野外分离株对3种化学合成药物的抗药性

取近年分离的 6个广东柔嫩艾美耳球虫 ( Eim eria tenella)野外株 ,以病变记分减少率 ( RLS)和抗球虫指数 ( ACI)作为判断指标 ,检测了它们对地克珠利、球净和球痢灵的抗药性。结果发现 ,5个野外分离株对地克珠利抗药 ,1个敏感 ;1个野外分离株对球净抗药 ,4个部分抗药 ,1个敏感 ;6个野外分离株均对球痢灵抗药。参考株 ( GD株 )对地克珠利、球净这 2种药物仍很敏感 ,但对球痢灵部分抗药。     

球虫抗药性检测方法评述

抗药性是药物预防鸡球虫病的主要障碍,鸡球虫抗药性的检测方法主要包括笼饲试验法(鸡体测定法)、鸡胚试验法、细胞培养法、聚丙烯酰胺凝胶电泳法、同工酶测定法、PCR测定法等,本文对上述各种检测方法及其判定标准进行了综述.     

Fetotoxicity of some anticoccidial drugs in chickens

Fetotoxic effects induced by three anticoccidial drugs: robenidine, salinomycin and arprinocid were elucidated in the chicken. Different doses of these drugs were inoculated in groups of embryonated chicken eggs by the yolk sac route. After inoculation, candling of the eggs was performed daily and embryonic or fetal mortalities were recorded. At 19 days old, alive fetuses were collected, weighed, measured and examined morphologically for abnormalities. A group of eggs was kept non-inoculated as a control and another was inoculated with the solvent of the tested drugs. Inoculation of 0.09-9.75 mg robenidine/egg, 0.06-6.75 mg salinomycin/egg or 0.08-8.25 mg arprinocid/egg into the yolk sac of 7 days old embryos caused a dose-dependent fetal death. Arprinocid was the most lethal to chicken fetuses, followed by salinomycin while robenidine was the least. Dead fetuses were usually haemorrhagic, dwarfish and friable. Surviving fetuses showed a dose-dependent reduction in body weight and length, insignificant decrease in leg and wing lengths as well as some developmental abnormalities.     

鸡球虫体外细胞培养的研究进展

球虫的细胞培养是指在体外合适的细胞体系中培养球虫完成其发育过程的方法,该方法经过近50年的发展已逐步形成一种比较完备的体外培养技术,目前该技术已在球虫学研究中广泛应用。作者从鸡球虫体外培养的球虫种类及其发育阶段、细胞类型、影响因素及其应用等4个方面对这一技术研究作一简要综述。     

Sensitivity of field isolates of Eimeria species to monensin and lasalocid in the chicken

Isolates of Eimeria species obtained from broiler or from breeder farms were compared for their sensitivity to two ionophorous anticoccidial drugs, monensin and lasalocid. All of 25 isolates from broiler farms were resistant to 100 ppm monensin or 90 ppm lasalocid, while 14 of 16 isolates were resistant to monensin and seven of 16 to lasalocid from breeder farms (replacement layer and broiler breeder).     

Drug-sensitivity of 99 isolates of coccidia from broiler farms

Coccidia were isolated from 99 broiler farms in 12 broiler-producing states and tested for sensitivity to contemporary anticoccidial drugs. The isolates usually comprised two or more species, including 92 Eimeria acervulina, 47 E. maxima, 28 E. tenella, and 10 E. brunetti. Based on intestinal-lesion-score reduction of 30% or more, 38% of isolates were resistant to monensin (110 ppm), 29% to salinomycin (60 ppm), 20% to nicarbazin (125 ppm), and 46% to amprolium + ethopabate (125 + 4 ppm). Isolates with 50% or greater reduction of lesion scores were considered sensitive. Thirty-three percent were sensitive to monensin, 53% to salinomycin, 67% to nicarbazin, and 39% to amprolium + ethopabate. Other isolates had intermediate response to drugs and were considered to have "reduced sensitivity." There was some evidence for incomplete cross resistance to the polyether, ionophorous products.     

Isolates of Eimeria tenella: studies on resistance to ionophorous anticoccidial drugs

Four isolates of Eimeria tenella obtained from the field were partially resistant to monensin. This resistance was not lost after 10 passages in unmedicated chickens, indicating that it was stable. One of the four isolates was examined and found to be resistant also to narasin, salinomycin and lasalocid.     

柔嫩艾美耳球虫扬州分离株对8种抗球虫药的抗药性

将柔嫩艾美耳球虫(Eimeria tenella)扬州分离株感染14日龄苏禽黄羽肉鸡,设立8个用药组、1个感染不用药对照组和1个不感染不用药对照组,以相对卵囊产量、病变记分减少率、最适抗球虫百分数和抗球虫指数为指标对该虫株对盐霉素、马杜拉霉素、球痢灵、氯羟吡啶、氨丙啉、尼卡巴嗪、甲基三嗪酮、地克珠利等8种常用抗球虫药的抗药性进行了综合评定,分析了该地区球虫的抗药性及对策。结果表明,该虫株对甲基三嗪酮敏感,对氨丙啉具有中度抗药性,对盐霉素、马杜拉霉素、球痢灵、氯羟吡啶、尼卡巴嗪、地克珠利等其他6种药物具有完全抗药性。提示目前在扬州地区甲基三嗪酮抗球虫疗效最好,氨丙琳效果稍差,应合理使用,盐霉素等其他6种药物应慎用、减少或暂停使用。     

安徽3株柔嫩艾美耳球虫对5种抗球虫药的耐药性检测

采用鸡体试验法,以抗球虫指数、最适抗球虫活性百分率、病变记分减少率和相对卵囊产量4项指标综合判定,安徽庐江县、青阳县和肥西县3个地区鸡柔嫩艾美耳球虫对磺胺氯吡嗪钠、马杜拉霉素、氨丙啉、妥曲珠利、地克珠利的耐药性。结果显示,庐江株对氨丙啉和妥曲珠利敏感,对磺胺氯吡嗪钠和地克珠利完全耐药,对马杜拉霉素中度耐药;青阳株对地克珠利和妥曲珠利敏感,对磺胺氯吡嗪钠和马杜拉霉素完全耐药,对氨丙啉中度耐药;肥西株对磺胺氯吡嗪钠敏感,对妥曲珠利中度耐药,对地克珠利、马杜拉霉素和氨丙啉完全耐药。     

Anticoccidial efficacy of diclazuril against recent field isolates of Eimeria from commercial poultry farms

The anticoccidial efficacy of diclazuril, a novel anticoccidial agent, was titrated in laboratory experiments using recent field isolates of Eimeria. Fifty tests were conducted with six individual species isolates, and seven tests were done with a mixture of the six species. Results were based on intestinal lesion scores at necropsy, droppings scores, and weight gain. Diclazuril at 0.5 ppm was almost completely effective against E. tenella, E. acervulina, and E. mitis. Prevention of E. brunetti was better at 1.0 ppm than at 0.5 ppm. In birds infected with E. mitis. Prevention of E. brunetti was better at 1.0 ppm than at 0.5 ppm. In birds infected with E. maxima, diclazuril at 0.5-1.5 ppm significantly reduced lesion scores and droppings scores and improved weight gain, although lesions were higher than with other species. Oocyst shedding by E. maxima was almost completely prevented by 0.5-1.5 ppm. Lesion scores and droppings scores caused by E. necatrix or mixed infections were greatly reduced by 0.5 ppm of diclazuril, but 1.0 ppm was necessary to obtain full protection of weight gain. Results suggest that 1.0 ppm of diclazuril best prevents coccidiosis caused by six species of coccidia in chickens.