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D Licois

Publications and source records attributed to D Licois.

At least 19 recordsLinked to original sources
PubMed2006

Fractionation of the reference inoculum of epizootic rabbit enteropathy in discontinuous sucrose gradient identifies aetiological agents in high density fractions.

Epizootic rabbit enteropathy (ERE) is a major cause of economic loss in intensive rabbit production. Since its first recognition in 1997, much work has been done to determine the pathogenic mechanisms of the disease and to identify the aetiological agent(s). Unfortunately, the quest for aetiology has only met with limited success despite the ability to reproduce the syndrome by inoculation of intestinal contents from field cases. These intestinal inocula contain a huge number of microorganisms which could all be involved in the aetiology of ERE. To decrease the number of putative agents, the French reference inoculum TEC3 was fractionated on a discontinuous sucrose gradient so that seven fractions (supernatant, 10%, 20%, 30%, 40%, 50% and pellet) were obtained. Specific-pathogen-free rabbits were inoculated with three out of these seven fractions (supernatant, 30%, and pellet). The objectives were: (1) to characterise the seven fractions by bacteriological examination; (2) to verify whether the aetiological agent was present in the fractions by inoculation of rabbits; (3) to assign the aetiological agent of ERE to a morphological group of pathogens; (4) to identify a fraction which could replace the reference inoculum TEC3 in applications such as cell cultures or egg inoculation. The results strongly suggest that ERE is a bacterial disease and does not have a viral or parasitic aetiology.

Animals↗
PubMed2005

Infectious agents associated with epizootic rabbit enteropathy: isolation and attempts to reproduce the syndrome.

Epizootic rabbit enteropathy (ERE), a highly lethal (30-80% mortality) disease of broiler rabbits aged 6-14 weeks, first appeared in 1997 in French intensive enclosed rabbitries and is of unknown aetiology. Bacteriological, virological and parasitical examination of the intestinal contents of rabbits that had died either in spontaneous field cases or after experimental reproduction of ERE, were undertaken in an attempt to identify infectious agents that may play a role in the disease. Two bacterial strains, Clostridium perfringens and non-enteropathogenic Escherichia coli were repeatedly isolated at high faecal counts from naturally infected animals. In field cases, a correlation between typical gross lesions of epizootic enteropathy and the presence of the alpha toxin of Cl. perfringens was observed (P<0.0001; Chi-squared test). Although attempts to reproduce the disease by inoculation with different pools of cultivable bacterial strains failed, the disease was successfully reproduced by inoculation with one French and two Belgian samples of caecal contents.

Animals↗
PubMed2001

Electron microscopic study on sporocysts and sporozoites of parental strains and precocious lines of rabbit coccidia Eimeria intestinalis, E. media and E. magna.

The fine structure of sporocysts and sporozoites of parent strains and precocious lines of rabbit coccidia Eimeria intestinalis, E. magna and E. media was studied. The parent strains and precocious lines differ only in the shape and size of refractile bodies (RB). In the sporocysts of precocious lines of E. magna and E. media, one extremely large RB was seen, either inside one of the sporozoites, or free in the sporocyst. In the oocysts of the precocious strain of E. intestinalis, two sporocysts resembled those of the precocious lines of E. magna and E. media, whereas the other two sporocysts did not harbour any RB. Sporozoites of all the precocious lines contained no, or very small, RB after in vitro excystation.

Animals↗
PubMed1997

Acquired protection of the rabbit (Oryctolagus cuniculus) against coccidiosis using a precocious line of Eimeria magna: effect of vaccine dose and age at vaccination.

Sucklings were vaccinated orally once at 25, 27 or 29 days of age with a precocious line of Eimeria magna. Each group received two doses varying from 3.5 x 10(2) to 3.5 x 10(4) oocysts. At 36 days of age, animals received a challenge inoculation with 10(4) oocysts of the wild strain of E.magna. Vaccination reduced oocyst output 10 to 1000 times after the challenge inoculation and prevented the decrease in the weight gain observed in non vaccinated challenged animals. When the vaccination was performed more than 9 days before challenge, full protection was obtained. An individual oral vaccination performed with 3500 oocysts gave total protection whatever the age at vaccination between 25 and 29 days of age.

Administration, Oral↗
PubMed1997

Vaccination against Eimeria magna coccidiosis using spray dispersion of precocious line oocysts in the nest box.

Coccidiosis mostly affects young rabbits just after weaning (5- to 6-week-old animals). Prevention of this disease must therefore be initiated before weaning. 'Precocious lines', derived from field species display good immunogenicity, though not pathogenic when administered at the right dose. In the present work, we tested the vaccination method of the whole litter at 25 days of age by spray dispersion of oocysts of a precocious line of Eimeria magna in the nest box. Three doses were tested, d1 = 4 x 10(2) oocysts, d2 = 4 x 10(3) oocysts, d3 = 4 x 10(4) oocysts. The animals were challenged individually with 10(4) oocysts of a wild strain of E. magna at 35 days of age, 5 days after weaning. The oocyst output and weight gain were recorded after vaccination and after challenge. The vaccinated animals did not display any vaccine reaction. The dose d3 was totally effective on oocyst output and on weight gain under our experimental conditions. As our challenge conditions were severe, we think that a lower vaccine dose could be used. This method proved to be efficient, and quick and easy to use because it did not require animal manipulation.

Animals↗
PubMed1996

Eimeria magna Pérard, 1925: study of the endogenous development of parental and precocious strains.

The endogenous development of a parental strain of E. magna and its deriving precocious line was studied after inoculation of coccidia-free rabbits with oocysts or sporocysts directly into the duodenum and using electron microscopy. Four meront generations could be observed mainly in the jejunum and ileum for the parent strain. The first merogony began 24 h post-inoculation (h p.i.). and meronts were matured about 48 h p.i. The second and the third generation were complete at 66 and 84 h p.i. respectively. Thus, each generation needs approximately 16-20 h for maturation. The fourth generation appeared 102 h p.i. and the young gamonts were present 120 h p.i. As in the other rabbit Eimeria, two types of meronts were described: A and B. The morphology of all endogenous stages of the precocious line was similar but refractile bodies were absent in the first generation merozoites and the fourth generation meront was lacking.

Animals↗
PubMed1996

A new approach for the identification and the diagnosis of Eimeria media parasite of the rabbit.

In this work, we described a new approach for the isolation of a species-specific probe for the Eimeria media parasite of the rabbit based on the use of the random amplified polymorphic DNA (RAPD) technique. A specific fragment of 800 bp of the studied species was isolated after RAPD and then cloned and DIG-radiolabeled. After dot-blotting, we observed that this probe was specific for E. media. Sequencing of the 3' and 5' ends of this probe enabled the determination of two primers that could be used in a PCR reaction. The amplified product of 750 bp was specific E. media. The use of these primers and of our probe allowed the detection of a very small number of oocysts. With a new protocol of DNA purification, 10 purified oocysts were detected by PCR. The efficiency of the amplification was not changed when two species were mixed. The threshold of detection of oocysts in fecal matter was equal to 30.

Animals↗
PubMed1996

Eimeria media Kessel 1929: comparative study of endogenous development between precocious and parental strains.

Endogenous development of a pure strain of Eimeria media and of a precocious line derived from this strain was studied in specific pathogen-free (SPF) rabbits. Endogenous development of the parental strain comprised three generations and the gamogony began 76 h post-inoculation (pi). Two types of meronts were observed in each generation. The type A meronts gave rise to large, polynucleated merozoites present in low numbers. Multiplication was carried out by endomerogony. Within type B meronts, merozoites arose from ectomerogony. These were slender and more numerous than those of type A. The sporozoite refractile body was divided and distributed into the first and second generation merozoites but not into the third. The endogenous development of the precocious line was similar to that of the parental strain except that no refractile body was observed and the last merogony was absent. Gamogony appeared 60 h pi.

Animals↗
PubMed1995

Study of the inter- and intraspecific variation of Eimeria spp. from the rabbit using random amplified polymorphic DNA.

A genetic polymorphism study was performed in coccidia from the rabbit. A comparative analysis of the RAPD (random amplified polymorphic DNA)-generated fingerprints, using 11 arbitrary primers, was carried out (1) in nine Eimeria species (E. intestinalis, E. magna, E. piriformis, E. flavescens, E. vejdovskyi, E. coecicola, E. perforans, E. exigua, and E. media) and (2) in two strains of E. intestinalis and four strains of E. media originating from different geographic areas. For each of these four strains of E. media, three lines deriving from the multiplication of a single oocyst were compared. All the primers tested yielded about ten amplified fragments. The profiles obtained differed considerably according to the species; thus, it was not possible to establish a phylogeny. On the other hand, species-specific fingerprints were observed, showing that RAPD assays might be useful for diagnosis. In E. media, analysis of the RAPD products showed weak differences between each of the four strains but nevertheless allowed differentiation of the lines deriving from the multiplication of one oocyst. Similar results were obtained with three methods of analysis: correspondence analysis, the hierarchical unweighted pair-group method with arithmetic averages (UP-GMA), and parsimony analysis. RAPD proved to be a useful technique for these intraspecific studies.

Animals↗
PubMed1995

Eimeria magna: pathogenicity, immunogenicity and selection of a precocious line.

A precocious line (PrEmag) of Eimeria magna in rabbits was obtained by selecting for early development of oocysts. The prepatent period was shortened by 46 h. The pathogenicity of PrEmag was substantially reduced and its reproductive potential was much lower (500 times) than that of the parent strain. Rabbits given 2500 oocysts of PrEmag were almost totally protected against a challenge with the parent strain. As in other precocious lines of coccidia from the rabbit, PrEmag showed morphological anomalies of the sporulated oocysts. Each sporocyst harboured one large refractile body instead of the two smaller ones in the parent strain.

Animals↗
PubMed1995

Relationships between microflora and caecal fermentation in rabbits before and after weaning.

Some microbiological and biochemical parameters of caecal content were studied in 15- to 49-d-old rabbits that were slaughtered sequentially. The ammonia level did not differ before weaning (11.5 mmol/L on average) (P = 0.41) or after weaning (7.4 mmol/L on average) (P = 0.19) but decreased by 40% (P < 0.001) between days 29 and 32. The level of pH decreased linearly (P < 0.001) throughout the period studied. The Escherichia coli counts decreased up to weaning (P < 0.001) and was then not significantly affected by age (P = 0.12). The total volatile fatty acid (VFA) concentration increased between days 15 (8.2 mmol/L) and 25 (33.9 mmol/L) (P < 0.05) and then levelled off below 40 mmol/L. Molar proportions in propionate and in branched-chain fatty acid (BCFA) and valeric acid were high at day 15 but decreased when the animals began to eat solid feed. The C3/C4 ratio reversed at weaning (3.8 on day 15 and 0.5 on day 49) whereas the acetic acid proportion was not affected by age (P = 0.19). High counts of anaerobic microflora were found between 15 and 22 d of age (10(11) bacteria/g of caecal content, on average) and did not change significantly according to the age (at about 10(10) bacteria/g), from day 29 until the end of the experiment (P = 0.29). Amylolytic flora had a similar evolution at a slightly lower level. In contrast, under our breeding conditions cellulolytic microflora slowly colonized the caecum and remained at a low level. The discriminant analysis revealed relationships between ages, intestinal microflora and fermentation parameter; the colibacilli flora was associated with mother-fed animals and amylolytic flora which was linked to BCFA and valeric acid, while the cellulolytic flora was associated with animals older than 4 weeks and linked to the production of C2, C3, C4 and ammonia.

Aging↗
PubMed1994

Eimeria media: selection and characterization of a precocious line.

A precocious line of Eimeria media was obtained by selection for early development of oocysts in rabbits. The prepatent period was reduced from 108 to 72 h. The precocious line was less pathogenic than the original strain, and its multiplication rate was lower. Rabbits given oocytes of the precocious line were totally immune to challenge with the original strain as assessed by change in weight gain but were partially protected as assessed by oocyst output. Selection for precocious development was accompanied by morphological changes in the sporulated oocytes; each sporocyst contained only one large refractile body instead of the two smaller bodies seen in the original strain.

Animals↗
PubMed1994

The invasion of the rabbit intestinal tract by Eimeria intestinalis sporozoites.

To follow the route of migration of Eimeria intestinalis sporozoites from the excystation stage to their development in the epithelial cells of the ileum, we inoculated sporocysts into the duodenum of coccidia-free rabbits and euthanized the animals at 10 min to 12 h post-inoculation. Excystation occurred at less than 10 min after the experimental infection. The sporozoites penetrated into the epithelium of the duodenum at as early as 10 min post-inoculation; 6 h later, the number of sporozoites had dramatically decreased in the duodenal mucosa, with a corresponding increase being noted in the ileal mucosa. These findings suggest that sporozoites invade the duodenal epithelium and migrate to the ileum by an as yet unknown nonlumenal tissue route.

Animals↗
PubMed1993

Eimeria sp. from the rabbit (Oryctolagus cuniculus): pathogenicity and immunogenicity of Eimeria intestinalis.

The pathogenicity and immunogenicity of Eimeria intestinalis was evaluated in SPF rabbits. The animals were given immunizing doses of 6, 6 x 10(2), 6 x 10(3), and 6 x 10(4) sporulated oocysts and were challenged with 3 x 10(3) oocysts. The criteria analysed were the daily weight gain and the oocyst output. This study showed that E. intestinalis had strong immunogenicity, as the inoculation of 6 oocysts was sufficient to minimize the clinical expression of the disease following the challenge and to reduce the oocyst output by about 60%. The immunity towards the excretion of oocysts and the illness was absolute in animals inoculated with 600 or more oocysts. Moreover, this protection seemed to be efficient at least 8 weeks after the challenge. The present results also confirm the pathogenicity of E. intestinalis, although the occurrence of diarrhoea may be irregular, and emphasize the fact that the capacity of this Eimeria for multiplication is not a criterion for clinical diagnosis of the disease.

Animals↗
PubMed1993

Migration of sporozoites and merogony of Eimeria coecicola in gut-associated lymphoid tissue.

The invasive phase of Eimeria coecicola was studied during the first 80 h postinoculation (p.i.). Using a method that synchronized the life cycle, sporozoites were observed in the duodenum and the jejunum until 32 h p.i. They were seen first in the villous epithelial cells or in host cells resembling intraepithelial lymphocytes (IEL). Later they were observed in IEL in the lamina propria. After 48 h p.i., no coccidian stage was identifiable in the mucosa of the small intestine but sporozoites appeared in the lymphoid cells of lymphatic follicles of the gut-associated lymphoid tissue (vermiform appendix, sacculus rotundus, and Peyer's patches). The first merogony was observed 64 h p.i. in these lymphoid cells and in membranous epithelial cells (M-cells) but was never seen in the epithelium itself. Morphologically there were two types of meronts, depending on the host cell type, but in both cases the merozoites contained a refractile body and resembled sporozoites. The first meronts of the second generation were observed 80 h p.i. in the villous epithelial cells of the domes of the follicles of the gut-associated lymphoid tissue, where the further development of this Eimeria takes place. This pattern of invasion strongly suggests that sporozoites take an exclusively extraintestinal route to reach the target cells. Moreover, to our knowledge this is the first description of an eimerian merogony that does not take place in epithelial cells.

Animals↗