PhD student, Universiti Kebangsaan Malaysia (UKM)
To elucidate the molecular mechanisms of drug resistance and precocious development in E. tenella
The previous study of this parasite investigated the genetic basis and precocious development which resulted in the construction of a genetic linkage map from a cross between an arprinocid resistant line of the Eimeria tenella Weybridge strain and an attenuated E. tenella Wisconsin strain line. Additionally, various other genomic resources for E. tenella are currently available including the chromosome 1 and the whole genome sequences. These genome sequence data are publicly available and thus, it is currently feasible to employ the large-scale sequencing to identify the genetic factors (genes, promoters, etc.) that are associated with drug resistance and precocious development.
The mapping of the clones of E. tenella sequence reads to the available genome sequences will enable the identification of parent-specific SNPs in the genome of each clone. Sections of the genomes that demonstrate uni-parental genotypes can then be determined, and further analysis of these SNPs data will enable the identification of the genetic factors associated with drug resistance of precocious development.
The further characterisation of genetic factors will provide information regarding their potential functions and roles, and the molecular basis of drug resistance and precocious development to develop more effective controls for avian coccidiosis and other parasitic diseases.
Abstract: In this study, coccidia were isolated and identified from 5 main poultry farms located in Zhejiang province, eastern China. The overall prevalence of Eimeria spp. was 30.7% (95 of 310). Five common species were observed: E. tenella, E. acervulina, E. maxima, E. necatrix, and E. mitis. Two isolates (HZ and QZ) were tested for sensitivity to 8 anticoccidial drugs using 4 indexes including anticoccidial index (ACI), percent of optimum anticoccidial activity (POAA), reduction of lesion scores (RLS), and relative oocyst production (ROP): sulfachloropyrazine, toltrazuril, diclazuril, sulfamonomethoxine/trimethoprim, and amprolium; sulfaquinoxaline/sulfadimethoxine, nicarbazin, and halofuginone. The results showed that the 2 isolates have developed various degrees of resistance to most of the tested drugs. The multi-resistance coccidia are a potential threat to local poultry farming. Rotation of anticoccidial drugs and shuttle programs are recommended to prevent further economic losses caused by coccidiosis.
Pub.: 25 Mar '17, Pinned: 30 Jul '17
Abstract: Polyether ionophores are widely used to treat and control coccidiosis in chickens. Widespread use of anticoccidials resulted in worldwide resistance. Mechanisms of resistance development and expansion are complex and poorly understood. Relative proteomic quantification using LC-MS/MS was used to compare sensitive reference strains (Ref-1, Ref-2) with putatively resistant and moderately sensitive field strains (FS-R, FS-mS) of Eimeria tenella after isotopic labelling with tandem mass tags (TMT). Ninety-seven proteins were identified, and 25 of them were regulated. Actin was significantly upregulated in resistant strains in comparison with their sensitive counterparts. On the other hand, microneme protein (MIC4) was downregulated in resistant strains. Optimization of labelling E. tenella sporozoites by TMT might identify further proteins that play a role in the obvious complex mechanism leading to resistance against Monensin.
Pub.: 30 Mar '17, Pinned: 30 Jul '17
Abstract: Avian coccidiosis is caused by the intracellular protozoan Eimeria, which produces intestinal lesions leading to weight gain depression. Current control methods include vaccination and anticoccidial drugs. An alternative approach involves modulating the immune system. The objective of this study was to profile the expression of host defense peptides such as avian beta-defensins (AvBDs) and liver expressed antimicrobial peptide 2 (LEAP2), which are part of the innate immune system. The mRNA expression of AvBD family members 1, 6, 8, 10, 11, 12, and 13 and LEAP2 was examined in chickens challenged with either E. acervulina, E. maxima, or E. tenella. The duodenum, jejunum, ileum, and ceca were collected 7 d post challenge. In study 1, E. acervulina challenge resulted in down-regulation of AvBD1, AvBD6, AvBD10, AvBD11, AvBD12, and AvBD13 in the duodenum. E. maxima challenge caused down-regulation of AvBD6, AvBD10, and AvBD11 in the duodenum, down-regulation of AvBD10 in the jejunum, but up-regulation of AvBD8 and AvBD13 in the ceca. E. tenella challenge showed no change in AvBD expression in any tissue. In study 2, which involved challenge with only E. maxima, there was down-regulation of AvBD1 in the ileum, AvBD11 in the jejunum and ileum, and LEAP2 in all 3 segments of the small intestine. The expression of LEAP2 was further examined by in situ hybridization in the jejunum of chickens from study 2. LEAP2 mRNA was expressed similarly in the enterocytes lining the villi, but not in the crypts of control and Eimeria challenged chickens. The lengths of the villi in the Eimeria challenged chickens were less than those in the control chickens, which may in part account for the observed down-regulation of LEAP2 mRNA quantified by PCR. Overall, the AvBD response to Eimeria challenge was not consistent; whereas LEAP2 was consistently down-regulated, which suggests that LEAP2 plays an important role in modulating an Eimeria infection.
Pub.: 19 May '17, Pinned: 30 Jul '17
Abstract: Background: Halofuginone hydrobromide (1) is recognized as an effective drug against several species of Eimeria (E.) in poultry. In this paper, we describe a convenient and low cost preparation method for the compound, as well as primary validation of its activity. Methods: First, 7-bromo-6-chloroquinazolin-4(3H)-one (2) was prepared from m-chlorotoluene by a conventional process, and then chloroacetone was creatively introduced in two steps. Finally, halofuginone hydrobromide (1) was obtained from 7-bromo-6-chloro-3-(3-cholroacetonyl) quinazolin-4(3H)-one (4) by a four-step reaction sequence including condensation, cyclization, deprotection and isomerization. The structures of the relative intermediates and target compound were characterized by melting point, IR, MS and ¹H-NMR. Besides, the protective effect of compound 1-supplemented chicken diet at doses of 6, 3 and 1.5 mg per 1 kg were evaluated on chickens infected with E. tenella, by reduction in mortality, weight loss, fecal oocyst excretion and gut pathology, respectively. Results: Halofuginone hydrobromide (1) was prepared successfully by and improved and innovative method based on traditional research. Moreover, the synthesized halofuginone hydrobromide significantly exhibited an anti-coccidial property. Conclusions: The fruitful work described in this Communication has resulted in halofuginone hydrobromide, which has a good pharmaceutical development prospects, becoming more available for large-scale production.
Pub.: 01 Jul '17, Pinned: 30 Jul '17
Abstract: Eimeria spp. are intracellular parasites that have a major impact on poultry. Effective live vaccines are available and the development of reverse genetic technologies has raised the prospect of using Eimeria spp. as recombinant vectors to express additional immunoprotective antigens. To study the ability of Eimeria to secrete foreign antigens or display them on the surface of the sporozoite, transiently transfected populations of E. tenella expressing the fluorescent protein mCherry, linked to endogenous signal peptide (SP) and glycophosphatidylinositol-anchor (GPI) sequences, were examined. The SP from microneme protein EtMIC2 (SP2) allowed efficient trafficking of mCherry to cytoplasmic vesicles and following the C-terminal addition of a GPI-anchor (from surface antigen EtSAG1) mCherry was expressed on the sporozoite surface. In stable transgenic populations, mCherry fused to SP2 was secreted into the sporocyst cavity of the oocysts and after excystation, secretion was detected in culture supernatants but not into the parasitophorous vacuole after invasion. When the GPI was incorporated, mCherry was observed on the sporozites surface and in the supernatant of invading sporozoites. The proven secretion and surface exposure of mCherry suggests that antigen fusions with SP2 and GPI of EtSAG1 may be promising candidates to examine induction of protective immunity against heterologous pathogens.
Pub.: 06 Jul '17, Pinned: 30 Jul '17
Abstract: Surgical ligation of chick ceca was used to study the role of absorption and extraintestinal transport in the action of anticoccidial drugs. The administration of drugs in the feed was started after ligation of one of the paired ceca. Birds were inoculated orally with oocysts ofEimeria tenella before cecal ligation or were given bilateral cecal injections of sporozoites after ligation. Cecal lesions caused by the coccidia were evaluated and compared on day 6 postinoculation.Lesions in ligated and unligated ceca were reduced by feeding robenidine (33 ppm), arprinocid (70 ppm), zoalene (125 ppm), aklomide (250 ppm), clopidol (125 ppm), nicarbazin (125 ppm), monensin (120 ppm), salinomycin (60 ppm), and lasalocid (75 ppm). The lesions were more severe in the ligated cecum than in the intact cecum, whether in nonmedicated or medicated birds, but the differences were statistically significant only upon treatment with amprolium, aklomide, robenidine, and clopidol. Generally, however, all drugs except amprolium, significantly reduced the lesions in the ligated cecum in comparison with the control, nonmedicated ligated cecum. Therefore, we concluded that the systemic absorption of most anticoccidial drugs contributes significantly to their efficacy against coccidia in the intestinal mucosa.
Pub.: 01 Jun '79, Pinned: 30 Jul '17
Abstract: A precocious line (HP) selected from the virulent Houghton (H) strain of Eimeria tenella was found to be attenuated and to have a shorter prepatent time than the parent strain. The second generation schizonts of the HP line were smaller than those of the H strain and contained fewer merozoites. A sub-line of HP, derived from a single oocyst, showed no sign of reversion to virulence after 19 passages without selection for precocity. Similarly, clones (the progeny of single sporozoites) of an attenuated embryo- adapted line (TA) remained avirulent after up to 26 passages in the chicken. In contrast, an uncloned TA line reverted to virulence after 20 passages in chickens. The reproduction in chickens of the HP line was greater than that of the TA line. Chickens kept in wire-floored cages and given small numbers of oocysts of HP or TA were not substantially immune to challenge with the virulent H strain. However, when chickens kept in litter pens were given the HP line they developed a strong immunity to a large challenge with either the H, Weybridge or each of four field strains. In the same conditions, prior inoculation with TA led to only partial resistance against challenge.
Pub.: 01 Jan '86, Pinned: 30 Jul '17
Abstract: Live vaccines containing attenuated parasite strains are increasingly used to control chicken coccidiosis. In this paper antibody responses elicited by infections with wild-type and attenuated strains of Eimeria tenella and Eimeria necatrix were characterized by immunoblotting and ELISA with homologous and heterologous antisera. Few differences between antisera from birds infected with wild and attenuated strains of E. tenella were evident in immunoblots conducted with merozoite antigen preparations from both E. tenella strains, however the reactivity of sera raised in birds infected with the wild-type strain was noticeably more intense. In ELISAs conducted with merozoite antigen preparations, antisera from birds infected with the wild-type strains of E. tenella and E. necatrix consistently produced a significantly higher (P<0.05) antibody response than antisera from birds infected with the attenuated strains. Likewise, avidity ELISAs conducted with the E. tenella strains demonstrated that antibodies in birds infected with the wild-type strain were of significantly higher avidity (P<0.05) than antibodies in birds infected with the attenuated strain. The differences in the antibody responses are probably due to changes in the attenuated strain as a result of selection for precocious development and the less severe tissue damage and inflammation of the intestine resulting from infection with the attenuated strain.
Pub.: 03 Nov '10, Pinned: 30 Jul '17