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).     

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.     

Eimeria tenella: sensitivity of recent field isolants to monensin

Coccidia were propagated from litter samples obtained from broiler production flocks being medicated with monensin. Eimeria tenella was isolated from 48.9% of the litter samples from which coccidia were propagated. Tests of the monensin sensitivity of the 73 E. tenella isolants obtained revealed no monensin-resistant isolants.     

Anticoccidial efficacy of diclazuril against recent field isolates of Eimeria from turkey farms in the United States.

In a series of laboratory tests, diclazuril was evaluated for efficacy against Eimeria adenoeides, E. meleagrimitis, E. gallopavonis, and a mixture of the three species. Four isolates of each of the species were tested. When given at 0.5, 1.0, and 1.5 ppm in the feed, diclazuril was highly efficacious against all three species and against mixtures of the three, as judged by protection against mortality from coccidiosis, reduction in droppings scores, and improvement of weight gains compared with unmedicated controls. When diclazuril was given at 1.0 ppm, the improvement in droppings scores and weight gains was better than when 0.5 ppm of diclazuril was given. Increasing the dosage to 1.5 ppm did not appear to offer any consistent or significant improvement over 1.0 ppm.     

Higher incidence of Eimeria spp. field isolates sensitive for diclazuril and monensin associated with the use of live coccidiosis vaccination with paracox-5 in broiler farms

Twenty European Eimeria spp. field isolates were subjected to an anticoccidial sensitivity test (AST). The anticoccidial drugs tested were diclazuril (Clinacox) and monensin (Elancoban). The assay was performed in a battery cage trial. Infected medicated birds were compared with an unmedicated control group. Coccidial lesion scores and oocyst shedding were used as parameters. The results of the AST show that resistance is common amongst coccidiosis field isolates, especially Eimeria acervulina (68% and 53% resistance for diclazuril and monensin, respectively). Resistance is less frequent amongst Eimeria maxima (38% and 50% resistance for diclazuril and monensin, respectively) and Eimeria tenella isolates (23% and 38% resistance for diclazuril and monensin, respectively). A highly significant influence of the coccidiosis prevention program (live coccidiosis vaccination with Paracox-5 vs. anticoccidial drugs in feed) on the sensitivity patterns of Eimeria spp. field isolates for both diclazuril (P= 0.000) and monensin (P= 0.001) was found. Further, when looking at the single species and each anticoccidial drug level, significantly more sensitivity of E. acervulina for monensin (P= 0.018), E. maxima for diclazuril (P = 0.009), and E. tenella for diclazuril (P = 0.007) was found in isolates originating from vaccinated flocks. Moreover, for E. acervulina and diclazuril, E. maxima and monensin, and E. tenella and monensin a trend toward higher sensitivity of isolates for these products was found when live coccidiosis vaccination was applied. The present study shows that sensitivity for the anticoccidial drugs diclazuril and monensin is more frequent in Eimeria spp. field isolates originating from broiler farms where a coccidiosis vaccination policy is followed.     

Enzyme variation and pathogenicity of recent field isolates of Eimeria tenella

Seventy isolates of Eimeria tenella, obtained from commercial poultry farms worldwide and four reference laboratory strains were characterised by studies on the electrophoretic mobility of up to three enzymes. All populations possessed the same electrophoretic form of lactate dehydrogenase and malate dehydrogenase and one of two forms of glucose phosphate isomerase. One isolate was characterised by both forms of glucose phosphate isomerase. Studies on several isolates indicated that there was no correlation between the form of glucose phosphate isomerase found and the pathogenicity of an isolate.     

Study of resistance against some ionophores in Eimeria tenella field isolates.

Three Eimeria tenella field isolates from Gurgaon district of Haryana (north India) were studied in a battery test for evaluating drug resistance against two currently used ionophores; maduramicin (5ppm) and salinomycin (60ppm). Broiler birds (Ross strain) were infected with 10(5) sporulated oocysts each at the age of 2 weeks and prophylactic medication commenced 2 days prior to infection. Drug resistance was assessed by calculating the global index for individual ionophore compounds based on weight gain, feed conversion ratio, oocyst index, lesion score and mortality. Present studies revealed no resistance of the ionophores in any of the field isolates. Both the drugs showed varying degree of efficacy, e.g. maduramicin exhibited limited efficacy against all the three field isolates, whereas salinomycin showed limited efficacy against Gurgaon isolate (GrI)-I, good efficacy against GrI-II and partial resistance against GrI-III.     

Field isolates of Eimeria resistant to arprinocid

Twenty-four field isolates of Eimeria spp. which included Eimeria acervulina, E. praecox and E. mivati were tested for sensitivity to arprinocid included in the diet at 60 ppm. Twelve isolates from sites where arprinocid had been use for 5-7 successive flocks were resistant to the drug, whereas 12 isolates from sites where arprinocid had never been used were sensitive. These results indicate that resistance had been acquired as a result of the use of arprinocid in the field.     

Characterization of a strain of Eimeria meleagridis from the turkey

An isolate of Eimeria meleagridis Tyzzer, 1927 was obtained by harvesting oocysts from the ceca of a turkey from northwest Arkansas and a pure line was established by infecting birds with a single oocyst. Oocysts were first produced in the ceca of infected birds from 102 to 108 hr after inoculation and were of similar size (mean length X width, 24.9 X 17.0 microm) to those of Eimeria adenoeides Moore and Brown, 1951 and Eimeria gallopavonis Hawkins, 1952. The line was identified as E. meleagridis based upon the development of large schizonts in the midintestine, and small schizonts in the ceca. Two generations of large schizonts were found 48 and 72 hr after infection, and at least two generations of small schizonts were found from 60 to 108 hr after infection. An inoculum of 2 X 10(5) oocysts was found to cause a significant reduction in weight gain from days 0-3 and 0-6 after infection, suggesting that the significance of this species of Eimeria as a pathogen of turkeys should be reassessed.     

尼卡巴嗪对鸡柔嫩艾美耳球虫田间株的敏感性试验

以最适抗球虫活性百分率(POAA)、病变记分减少率(RLS)、相对卵囊产量(ROP)和抗球虫指数(ACI)为指标,检测了尼卡巴嗪对秦皇岛株和唐山株柔嫩艾美耳球虫的敏感性.结果表明,唐山株柔嫩艾美耳球虫对尼卡巴嗪无耐药性,秦皇岛株对其呈轻度耐药性.提示尼卡巴嗪在唐山和秦皇岛地区可以继续合理使用,但应控制用量和使用时间,以...     

Antigenicity of two turkey astrovirus isolates

Astroviruses are positive-sense single-stranded RNA viruses. These viruses cause gastroenteritis in humans and in a variety of animal species, including turkey poults. Only human astroviruses are well characterized antigenically. In the current study, two turkey astrovirus isolates, TAstV1987 and TAstV2001, were antigenically compared using cross-neutralization tests in turkey embryos, as well as cross-reactivity of the two isolates by an enzyme-linked immunosorbent assay (ELISA). The antigenic relatedness values (R) were calculated using the Archetti and Horsfall formula. The R value based on the cross-neutralization tests was 0.56%, which indicates that TAstV1987 and TAstV2001 belong to different serotypes; the R value of the two viruses based on ELISA was 70.7%, which suggests these two viruses share common antigen(s).     

Effect of monensin on experimental infections of Eimeria ninakohlyakimovae in lambs.

Two nearly identical experiments were conducted to determine the effects of the coccidiostatic compound monensin on Polled Dorset lambs experimentally infected with oocysts of Eimeria ninakohlyakimovae. Prophylactic medication at a dose level of 1 mg/kg of body weight was started 2 days before inoculation and prevented diarrhea and reduced oocyst production. Therapeutic medication at a dose level of 2 mg/kg, started with the appearance of signs of infection, reduced oocyst production below that of nonmedicated controls but did not eliminate diarrhea. Weight gains of medicated lambs were less than those of noninoculated, nonmedicated controls in both experiments. Apparently monensin, at the dose levels used, reduced oocyst production but also prevented weight gains as high as those in inoculated nonmedicated controls.     

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.     

Efficacy of decoquinate against drug sensitive laboratory strains of Eimeria tenella and field isolates of Eimeria spp. in broiler chickens in China

The efficacy of decoquinate against Eimeria infections in broiler chickens was evaluated using two drug sensitive laboratory strains of Eimeria tenella and 20 field isolates of Eimeria spp. collected from farms in China where various anticoccidials (including maduramicin) had been used. Decoquinate (20-40 ppm in feed) and maduramicin (5 ppm) were efficacious against E. tenella laboratory strains, but decoquinate more so than maduramicin. Body weight gains of E. tenella infected chickens were significantly improved, and caecal lesions were prevented, by feeding either decoquinate or maduramicin. Decoquinate also prevented oocyst production, but maduramicin did not. Most (18/20) Eimeria field isolates were resistant to maduramicin, judged by oocyst production; decoquinate at > or =20 ppm completely controlled all 20 field isolates. Decoquinate has potential value as a broiler anticoccidial in China and other countries where it has not been previously used.     

Selection for early (precocious) development of Eimeria meleagridis in the turkey

A precocious line of Eimeria meleagridis was developed by repeated propagation of the parasite in young turkeys and collection of the very first oocysts produced following infection. After 20 generations of selection, the prepatent period was reduced by 4-8 hr. Weight gain of poults given this line, from days 0-3 after infection, was significantly greater than that of poults given the parental strain, indicating that selection resulted in a loss of pathogenicity. Poults immunized with the precocious line produced no oocysts following challenge with the parental strain, indicating that immunogenicity was retained following selection. This is the first published report of the selection of a precocious line of Eimeria in the turkey.     

堆型艾美耳球虫早熟株对常用抗球虫药的敏感性测定

The study was aimed to explore the sensitivity of Eimeria acervulina （E.acervulina） precocious strain to some common anticoccidials (diclazuril, toltrazuril, sulfamonomethoxine, dinitolmide, decoquinate, nicarbazin, maduramicin, salinomycin and oxytetracycline). The sensitivity of E.acervulina precocious strain to 9 kinds anticoccidials was assessed by using 4 indices: anticoccidial activity percentage (POAA), reduction of lesion scores (RLS), relative oocyst production (ROP) and anticoccidial index (ACI). The results of these sensitivity trials indicated that the four indices POAA, RLS, ROP and ACI of groups toltrazuril, sulfamonomethoxine, dinitolmide, decoquinate, nicarbazin, salinomycin and oxytetracycline were all negative; the ROP index of diclazuril group was positive, the other three indices were negative. The ROP and ACI indices of maduramicin group were positive, the other two indices were negative. The results showed that the Eimeria acervulina precocious strain was sensitive to diclazuril, toltrazuril, sulfamonomethoxine, dinitolmide, decoquinate, nicarbazin, salinomycin and oxytetracycline, it was partly sensitive to maduramicin.     

鸡艾美耳球虫哈尔滨株的分离与鉴定

为研究鸡艾美耳球虫哈尔滨株单一虫种的生物学特性,本研究利用单卵囊分离技术分离了6种鸡艾美耳球虫哈尔滨株,用分离的单卵囊接种雏鸡,同时应用PCR方法对收集的单卵囊分离株进行球虫种类鉴定并进行同源性和系统进化分析.结果显示,分离得到的6株鸡艾美耳球虫分别为柔嫩艾美耳球虫、毒害艾美耳球虫、堆型艾美耳球虫、早熟艾美耳球虫、和缓艾美耳球虫和布氏艾美耳球虫,PCR结果表明单卵囊分离株确为该6种纯株.本研究表明毛细吸管单卵囊分离法简便易行,使接种难度降低,提高了接种成功率,为球虫的分子生物学研究奠定了基础.     

Interaction of aflatoxin with Eimeria tenella infection and monensin in young broiler chickens.

Young broiler chicks inoculated with Eimeria tenella and given a diet containing 2.5 mug aflatoxin/g had significantly higher mortality than birds with aflatoxicosis or coccidiosis alone or uninoculated controls. This effect was seen even when a light coccidial infection alone did not increase mortality or cause weight depression. In addition this higher mortality with the combination began earleir and occurred at a higher rate than did mortality from aflatoxin or cecal coccidiosis alone. Dietary monensin sodium (99 umg/g) did not completely prevent mortality and weight depression when aflatoxin and E. tenella were in combination. Aflatoxin and E. tenella singly significantly depressed three-week body weights; however, the depression was most severe when the two were in combination. Both dietary aflatoxin and E. tenella significantly reduced hemoglobin, packed cell volume, and plasma pigmentation, and in combination resulted in more severely reduced hemoglobin, packed cell volume, and plasma pigmentation. Coccidial lesion scores were significantly less for the combination of E. tenella and aflatoxicosis than for coccidiosis alone. This atypical response of the ceca to E. tenella in the presence of dietary aflatoxin was characterized by less distended ceca, very little coagulated blood in the ceca, and apparently more profuse cecal hemorrhage.     

柔嫩艾美耳球虫田间分离株药物耐药性调查

作者采集了5个不同地区发生球虫病鸡场的粪便,分离柔嫩艾美耳球虫不同地理株,为了检测它们对药物敏感性,选择常用的预防球虫病药物马杜拉霉素、莫能菌素、地克珠利,以ACI作为指标,进行了的药物敏感试验。结果表明,北京-1、潍坊和上海株对饲料中添加5 mg/kg马杜拉霉素产生了部分耐药性,而北京-2和北京-3两个虫株对其则敏感;北京-1、北京-2和潍坊株对100 mg/kg莫能菌素部分耐药,上海株完全耐药,而北京-3株对其敏感;北京-1、北京-2、潍坊株和上海株对1.0 mg/L地克珠利产生了部分耐药性,而北京-3株对它敏感。     

Efficacy of toltrazuril in broilers and development of a laboratory model for sensitivity testing of Eimeria field isolates

(1) The efficacy of toltrazuril (Baycox) against coccidiosis was established on a broiler farm in an intermittent application during five consecutive growing periods. Treated birds were fed a broiler ration without anticoccidials. The efficacy of Baycox was compared with the nicarbazin-salinomycin shuttle. It was concluded that Baycox retarded the onset of Eimeria infection for several weeks. During the fifth rearing period coccidiosis problems emerged on the farm in all birds during medication, suggesting development of resistance. (2) During a laboratory experiment the efficacy of Baycox was studied in birds after inoculation with different numbers of oocysts at 7, 10 or 15 days of age. Baycox was applied at 10 and 11 days of age. In all cases medication with Baycox protected birds from coccidiosis during a period of at least 7 days. This effect of Baycox could be due to the long-existing tissue levels of the product and its metabolites as well as its specific effect on the second generation of schizonts. (3) In another laboratory experiment coccidia obtained from field trials were tested for sensitivity to Baycox in conjunction with two strains obtained from farms were coccidiosis emerged during application. The inoculation model developed in this study was used for sensitivity testing. One of the Eimeria strains tested was resistant to the product, one strain was tolerant and the remaining two strains, including the control strain, were fully sensitive to Baycox.