Biomedical subjects

A Chauvin

Publications and source records attributed to A Chauvin.

At least 19 recordsLinked to original sources

PubMed2006

Transstadial and transovarial persistence of Babesia divergens DNA in Ixodes ricinus ticks fed on infected blood in a new skin-feeding technique.

Although Babesia divergens is the the principal confirmed zoonotic Babesia sp. in Europe, there are gaps in our knowledge of its biology and transmission by the tick Ixodes ricinus. In order to reproduce the part of the parasite cycle that occurs in the vector, an in vitro animal skin feeding technique on blood containing in vitro cultivated B. divergens was developed. Parasite DNA was detected in all samples of salivary glands of nymphs and adults that had fed on parasitized blood as larvae and nymphs, respectively, indicating acquisition as well as a transtadial persistence of B. divergens. PCR performed on eggs and larvae produced by females that had fed on parasitized blood demonstrated the existence of a transovarial transmission of the parasite. Gorging B. divergens infected larvae on non-infected gerbils showed persistance of the parasite over moulting into the resulting nymphs. These results indicate that the parasitic stages infective for the vector (i.e. the sexual stages) can be produced in vitro. To our knowledge, this is the first report of artificial feeding of I. ricinus via membrane as well as in vitro transmission of B. divergens to its vector. The opportunities offered by the use of such a transmission model of a pathogen by I. ricinus are discussed.

Animals↗

PubMed2005

Humoral and cellular immune responses to Fasciola gigantica experimental infection in buffaloes.

Humoral and cellular immune responses to Fasciola gigantica experimental infection in buffaloes were studied. The results showed that 33.4+/-9.1% of the infection dose was recovered as adult flukes from infected animals at necropsy. Significant differences of weight gain between infected and non-infected buffaloes was observed at 4 MPI (months post-infection). Anti F. gigantica excretory-secretory products (FgESP)-IgG levels increased significantly from 3 WPI (weeks post-infection) and displayed a peak at 13 WPI. Western blot indicated that in FgESP six major bands of 11.5, 19.0, 23.4, 29.8, 47.5 and 53.2kDa were recognized by F. gigantica-infected buffaloes sera after 0 WPI. Eosinophil numbers increased significantly from 3 WPI in F. gigantica-infected buffaloes and displayed a peak at 8 WPI. Peripheral blood mononuclear cells (PBMC) proliferation induced by FgESP increased from 2 WPI with a peak at 5 WPI. IFNgamma secretion by FgESP-stimulated PBMC appeared early from 1 WPI with three peaks at 2, 5 and 8 WPI, respectively. IL-10 production was observed from 2 WPI with two peaks at 4 and 9 WPI, respectively. Our results suggested that buffaloes were highly susceptible to F. gigantica infection, and this susceptibility could be associated with the late and weak cellular immune response in the early phase of infection and the Th0-like response throughout the infection.

Animals↗

PubMed2005

Fasciola hepatica and Fasciola gigantica: comparison of cellular response to experimental infection in sheep.

Cellular responses to Fasciola gigantica and to Fasciola hepatica infection in sheep were compared. Eosinophil numbers increased more quickly and strongly in F. gigantica-infected sheep than in F. hepatica-infected sheep. In both groups, peripheral blood mononuclear cell (PBMC) proliferation in response to the parasitic excretory-secretory products (ESP) showed similar kinetics. Interferon-gamma (IFN-gamma) production by ESP-stimulated PBMC was early and showed similar kinetics in both groups. Interleukin-10 (IL-10) production by FhESP-stimulated PBMC was very high throughout infection even at 0 weeks post-infection (WPI) in F. hepatica-infected sheep, while in F. gigantica-infected sheep, IL-10 production by FgESP-stimulated PBMC increased between 1 and 4 WPI. IL-10 production in F. gigantica-infected sheep was significantly lower than in F. hepatica-infected sheep during infection. The lower susceptibility to F. gigantica infection in sheep could be explained by the more intense cellular response induced by the parasite and the weaker capacity of F. gigantica to evade the immune response.

Animals↗

PubMed2005

Comparison of modulation of sheep, mouse and buffalo lymphocyte responses by Fasciola hepatica and Fasciola gigantica excretory-secretory products.

In order to explain the difference in susceptibility to Fasciola hepatica and F. gigantica between animal species, the activity of their excretory-secretory products (FhESP and FgESP, respectively) on concanavalin A (ConA)-induced proliferation of different animal species (sheep, mouse and buffalo) lymphocytes was compared. At high doses, FhESP inhibited proliferation of lymphocytes of all the animal species tested, and at low doses they inhibited the proliferation of sheep lymphocytes and increased the proliferation of buffalo and mouse lymphocytes. The effects of FgESP were similar but the intensity of FgESP inhibition was less than FhESP. The immunomodulatory effects of FhESP or FgESP could not alone explain the susceptibility level of hosts to Fasciola spp. The immunomodulatory molecules of FhESP and FgESP and their role in the course of Fasciola spp. infection should be further investigated.

Animals↗

PubMed2005

Reduced mechanosensitivity of duodenal vagal afferent neurons after an acute switch from milk-based to plant-based diets in anaesthetized pigs.

Acute changes in diet composition and/or origin alter gastric emptying and gastrointestinal motility. One of the hypotheses explaining these alterations involves changes in the sensitivity of duodenal vagal sensory neurons. The aim of this study was to evaluate the characteristics of multimodal duodenal vagal sensory neurons in 20 pigs feed either with milk-based or plant-based diets of identical caloric content. Twenty duodenal vagal afferents were recorded in anesthetized animal from the cervical vagus using the single fiber method. 10 pigs were fed with a milk-based diet (MD) for one month while the diet of the 10 other pigs was changed for plant-based diet (PD) the day preceding the recording session. The behavior of the receptors was tested in basal resting conditions and after challenges with duodenal intralipid and close intra-arterial injection of CCK, 5-HT or capsaicin with and without isovolumetric duodenal distensions at 20, 40 and 60 mmHg. All receptors were slowly adapting C type fiber with a receptor field located 6-7 cm distal to the pylorus. The rate of discharge during distension (20, 40 and 60 mmHg) combined with duodenal intralipid was significantly larger for MD compared with PD. Similarly, the rate of discharge observed during distensions performed with CCK and with 5-HT were greater for MD compared with PD while CCK and 5-HT without distension were equally stimulating for MD and PD. No significant difference was found between groups during capsaicin infusion irrespective of the stimulating pressure. In conclusion, a switch to plant-based diet, when compared to a milk-based diet, results in an overall decrease in mechanical sensitivity of duodenal neurons during lipid, 5HT and CCK challenges, but not in basal conditions or after capsaicin. This reduced sensitivity to distension may explain the diet-induced alteration of gastric emptying that is controlled primarily through a vago-vagal reflex.

Action Potentials↗

PubMed2004

Comparison of humoral response in sheep to Fasciola hepatica and Fasciola gigantica experimental infection.

Humoral response of sheep to F. gigantica was compared with the well known humoral response to F. hepatica, in order to explain the difference of susceptibility of sheep to these two parasites. In this work, a lesser susceptibility of sheep to F. gigantica than to F. hepatica infection was confirmed. Humoral response to F. hepatica infection is similar to that previously described by several authors. IgG level of F. gigantica infected sheep increased from week 2 post-infection (2WPI) and displayed a peak at 13WPI. F. gigantica excretory-secretory products (FgESP) analyzed by SDS-PAGE showed at least 31 bands from 12.0 to 127.6 kDa in FgESP. Western blot indicated that F. gigantica infected sheep sera recognized, in FgESP, at least 30 antigens from 7.8 to 119.2 kDa of which 12 major bands recognized after OWPI. In FhESP and FgESP, F. hepatica infected sheep serum reacted only with the lower molecular mass antigens, while F. gigantica infected sheep serum reacted with the lower and the higher molecular mass antigens. These differences of antigenic recognition might be associated with the difference of susceptibility of sheep. Further investigation must be done to study the mechanism of resistance between the sheep infected with F. hepatica or F. gigantica.

Animals↗

PubMed2002

Early hepatic cytokine mRNA expression in experimental rat fasciolosis.

We studied the development of the cellular response, particularly with respect to Th1 and Th2 cytokine mRNA levels, in rat liver during the first 14 days of experimental infection with Fasciola hepatica. We analysed the panel of cytokines involved in initiation of the inflammatory and immune response. The levels of various mRNAs, particularly those primarily associated with the acute inflammatory response, and those commonly associated with T-cell proliferation and differentiation, were assessed by reverse transcription-polymerase chain reaction (RT-PCR) in liver samples. We also investigated the immune and inflammatory mediators balance in the liver, draining lymph node and spleen, by RT-competitive PCR quantification of mRNA levels for IL-4, IL-10 and IFN-gamma. Our data provide the first evidence that, in the early phase of infection, the inflammatory response in the liver of infected animals is transiently depressed or delayed. A Th0 profile was initially observed in the liver and hepatic lymph node, which developed into a Th2 profile 2 weeks after infection in the liver only. In the spleen, cytokine down-regulation was initiated and maintained during this period, suggesting that the parasite acts differently locally and in the periphery.

Animals↗

PubMed2001

Fasciola hepatica: the characteristics of experimental infections in Lymnaea truncatula subjected to miracidia differing in their mammalian origin.

Experimental infections of Lymaea truncatula, using two susceptible snail populations (Berneuil, or Migné, central France) and four isolates of Fasciola hepatica miracidia differing in their mammalian host of origin (cattle, nutrias, rabbits, or sheep), were performed under laboratory conditions to determine whether the host of origin had an effect on the daily production of cercariae. Snails were each subjected to bimiracidial exposures and were then reared under semi-natural conditions (a constant temperature of 20 degrees C and natural photoperiod). Significantly lower values were noted in the rabbit groups for survival rates at day 30 post-exposure, as well as for prevalences of infection, snail growth. duration of shedding period, and the total numbers of cercariae these snails shed. The total number of cercariae shed by both nutria groups was significantly higher than those recorded in the six other infected groups. In the cattle, rabbit, and sheep (Berneuil only) groups, the peaks in the daily distribution of cercariae occurred between day 2 and day 4 after the first shedding, and the number of cercaria-shedding snails decreased with increasing number of shedding waves. In contrast, in the three other groups, the peaks were only observed between days 20 and 45. Snails shedding their cercariae during nine or more waves were numerous in these last groups. No infradian-type rhythm in the daily distribution of cercarial numbers over the shedding period was noted for any snail group. The highest production of F. hepatica cercariae in both nutria groups would be a consequence of a higher success rate of miracidia when they infected an allopatric population of snails. The absence of an infradian-type rhythm in the distribution of daily cercarial numbers in the eight groups suggests that this rhythm, if it occurs, would only be influenced by temperature and thus be limited to periods with optimal conditions for cercarial shedding.

Animals↗

PubMed2001

Role of vagal innervation on intragastric distribution and emptying of liquid and semisolid meals in conscious pigs.

The role of vagal innervation on emptying patterns and intragastric distributions of liquid and semisolid meals is still controversial. We aimed to record these features after dorsal, ventral and truncal vagotomies, using external gamma scintigraphy in conscious pigs in which the dorsal vagus specifically innervates the proximal stomach. Imaging of the stomach was performed for all experimental situations and before surgery using 99mTc-labelled glucose and porridge meals. Emptying of liquids was faster after dorsal vagotomy, whereas it was unchanged after ventral and truncal vagotomies (T1/2 = 57 +/- 8.5, 31 +/- 14.4, 54 +/- 9.1 and 42 +/- 14.9 min for intact, dorsal, ventral and truncal vagotomies, respectively). On the other hand, truncal vagotomy significantly reduced the emptying rate of semisolids whereas dorsal and ventral vagotomies had no significant effect (T1/2 = 96 +/- 7.2, 113 +/- 8.1, 75 +/- 9.9 and 260 +/- 56.6 min for intact, dorsal, ventral and truncal vagotomies). Morphological analysis of the gastric shape confirmed an overdistended proximal stomach after truncal vagotomy only. For semisolids, proximal stomach emptying followed the same emptying pattern as the entire stomach, irrespective of the surgical procedure. We concluded that the proximal stomach is the main control for the emptying of liquids and semisolids. The vagal control of overall gastric emptying for semisolids is probably identical to that modulating the intragastric distribution of the meal.

Animals↗

PubMed2000

Local hepatic immune response in rats during primary infection with Fasciola hepatica.

The distribution of lymphocyte subpopulations (TCD4+, TCD8+, TCD43+ and Ig+ cells), macrophages and eosinophils were analysed in the inflammatory infiltrates associated with hepatic lesions and in hepatic lymph nodes (HLN) from rats experimentally infected with F. hepatica and necropsied 1, 2, 3, 4, 6 and 8 week post infection (WPI). We also investigated the fixation of immunoglobulin isotypes on migrating flukes in the liver. As early as 1WPI, portal tract areas surrounding migratory tunnels were infiltrated with immune and inflammatory cells. The dominant cells were eosinophils and to lesser extent, macrophages and lymphocytes (TCD4+, TCD8+ and B). Most of the inflammatory and immune cells reached the posterior part of flukes, whereas in front of the parasites these cells were fewer in number. Except for eosinophils, no immune cells penetrated through granuloma consisting of hepatic necrotic cells. As early as 1WPI, IgM could be detected in the liver, and to a lesser extent IgA, IgG2a and IgG2b. At 2WPI, IgE and IgG1 began being detected. IgG2c was detectable at 3WPI. In HLN, we observed numerous microscopic follicles in the cortical zone with proliferation of germinal centres and medullary cords. The protective role of infiltrating cell populations and immunoglobulin isotypes and possible mechanisms of immune evasion by the parasite are discussed.

Animals↗

PubMed2000

Inventory of wild rodents and lagomorphs as natural hosts of Fasciola hepatica on a farm located in a humid area in Loire Atlantique (France).

With the objective of studying the role of wild fauna in the epidemiology of fasciolosis disease, a definitive wild-host inventory was carried out in a french farm where infected domestic hosts (cows) cohabit with wild potential ones. Liver flukes, faecal eggs and antibodies were looked for in lagomorphs (Oryctolagus cuniculus) and rodents (Myocastor coypus, Ondatra zybethicus, Rattus norvegicus, Arvicola sapidus and micromammal species) trapped in the study area. Presence of Fasciola hepatica was detected in two species: O. cuniculus and M. coypus. Infection rates were respectively 34% (42/124) and 55% (106/193). Liver flukes were found in 78 M. coypus (n = 192) and 11 O. cuniculus (n = 35). No other species was infected by F. hepatica. The number of animals shedding fluke eggs was higher in M. coypus (49 out of 127 sampled; 38.6%) than in O. cuniculus (two out of 17 sampled; 11.7%). The results indicate that M. coypus may play a role in the maintenance and the dissemination of F. hepatica in various environments and open a discussion on the role of other natural wild hosts.

Agriculture↗

PubMed1999

Babesia divergens in France: descriptive and analytical epidemiology.

Babesia divergens cause of bovine babesiosis transmitted by Ixodes ricinus, is widely spread especially in West, Central and South-West parts of France. It occurs with two annual peaks, in spring and autumn. The study was carried out during a period of two years (1991-1993) in four farms in the Sarthe area, in order to know the distribution and the ecology of I. ricinus, and to show the presence of B. divergens. Cattle are parasitised as early as March essentially by adult ticks, according to a seasonal distribution (spring, autumn). The flag method allows to catch essentially the larvae and the nymphs on the pastures; nymphs appear as early as March, and larvae one to two months later. Ectoparasite collection on trapped micromammals (Apodemus sylvaticus, Clethrionomys glareolus, etc.) in pastures hedges, is used to detect small I. ricinus populations, mostly larvae. A new ELISA method has been used for the study of the kinetics of anti-B. divergens antibodies in 236 cattle during two years. Most of the animals (60%) show a high antibody level, essentially at the end of the pasture season; the percentage of positive animals decreases during winter and increases again during the pasture season. Calves become seropositive since their first months on pastures. Adults show asymptomatic infections several times along the year, mostly during spring and autumn; only three clinical babesiosis cases have been observed during the whole study, in animals exhibiting nevertheless a high specific antibody level.

Animals↗

PubMed1998

Morphological variability in Fasciola hepatica eggs in ruminants, rodents and lagomorphs.

The length and width of 1297 Fasciola hepatica eggs shed in cattle hosts, 337 in sheep and 199 in nutria, were measured from several parts of France. The data were compared with those obtained from other studies in Spain, France (where rats were also investigated), Germany and the Netherlands. One way analysis of variance and discriminant analysis were used to assess differences between host origins. The distribution of length and width of eggs were analysed using skewness and kurtosis Fisher coefficients. The eggs recovered from sheep, cattle, rodents and lagomorphs were different in size: the eggs found in rodents (length L x width W in microm: 8592) and lagomorphs (L x W in microm: 9100) were smaller than those found in sheep and cattle (L x W in microm: 10,000). These morphological differences in F. hepatica eggs were host-induced in rats (L x W in microM: 9709 in cattle to 8949 in rats) and rabbits (L x W in microm: 9709 in cattle to 8432 in rabbits). These differences in size of eggs might correspond to their being less able to develop into miracidia in less frequent hosts such as rodents and rabbits.

Analysis of Variance↗

PubMed1998

IFN gamma and IL-10 production by hepatic lymph node and peripheral blood lymphocytes in Fasciola hepatica infected sheep.

The present study was designed to determine whether IFN gamma and IL-10 were secreted by peripheral blood mononuclear cells (PBMC) and hepatic lymph node mononuclear cells (HLNMC) from 17 Fasciola hepatica infected sheep after in vitro stimulation by Fasciola hepatica excretory-secretory products (FhESP) during the first six weeks of two different infections. The IFN gamma concentration in mononuclear cells (MC) culture supernatants was determined by sandwich ELISA. The presence of IL-10 in MC culture supernatants was determined by the capacity of these to inhibit, with or without monoclonal antibodies to IL-10, the NO production of recombinant bovine IFN gamma (rBoIFN gamma) activated monocytes. FhESP-stimulated PBMC and HLNMC produced IFN gamma in culture supernatants from DPI 7 (day post-infestation 7) to DPI 14. Culture supernatants of PBMC stimulated with FhESP first induced an increase in the NO production of rBoIFN gamma activated monocytes. After 2 or 3 weeks of infection, MC culture supernatant reduced the NO production of rBoIFN gamma activated monocytes. From DPI 35, anti-IL-10 antibodies addition restored or enhanced NO production. During sheep fasciolosis, IFN gamma production increased only until the first two weeks post infection. IL-10 could be secreted throughout the first six weeks of infection and could inhibit monocytes from DPI 35.

Animals↗

PubMed1997

[Diagnosis of bovine fascioliasis using serology of pools of sera. Interpretation in field conditions].

The efficacy of a serological test (ELISA with excretory-secretory products of Fasciola hepatica as an antigen) for the diagnosis of bovine fascioliasis was assessed under field conditions using pools of sera from 170 herds. Blood samples were collected from six to ten heifers and from five to ten adults in each herd. In 92 of the herds (Group 1) the animals had not been treated for fascioliasis; in 78 herds (Group 2), a fasciolicide had been used 3 to 6 months earlier. In each herd, three serum pools were examined: aliquots from all the animals sampled in a herd (GM); aliquots from heifers only (PM); and aliquots from the cows only (PM). Individual sera and the pools (GM and PM) were analyzed similarly and the specific antibody titer was calculated by comparison with laboratory standards. The antibody titer for pooled sera were correlated with the proportion of positive sera in the pool (P < 0.0001); but these could not be used to estimate the prevalence of seropositivity in a herd. Diagnosis based on pooled sera was less effective for the detection of low prevalences of seropositivity in Group 2 than in Group 1 because the antibody titer decreases after fasciolicide treatment. Infection was always detected using pooled sera in herds with a prevalence of seropositivity of more than 60% (GM) in Group 1, or with a prevalence of seropositivity of more than 70% in Group 2. The best method for herd diagnosis of fascioliasis was based on the presence of a positive test in either of the two PM groups. Using this method, all infected herds with a prevalence of seropositivity of more than 30% in Group 1, or 50% in Group 2, were accurately detected.

Animals↗

PubMed1996

Local immune response to experimental Fasciola hepatica infection in sheep.

Macrophages, eosinophils, neutrophils and lymphocyte subpopulations (OvCD5+, OvCD4+, OvCD8+, OvWC1+ and lg+) were identified in sections of hepatic tissue and hepatic lymph nodes from sheep experimentally infected with F. hepatica and necropsied 14, 28, 42 or 56 days post infection. The migratory tunnels produced by juvenile flukes appeared as local areas of necrosis surrounded by infiltrating inflammatory cells, particularly numerous macrophages, eosinophils and OvCD4+ lymphocytes n addition, B lymphocyte proliferation was observed in hepatic lymph nodes and in hepatic portal tracts. Only three juvenile flukes were identified in the sections. They where partially in contact with healthy tissue and partially with neutrophils, macrophages and eosinophils; they were covered by IgM Host-parasite interactions resulting from immune response regulation by helper T lymphocytes and from immune evasion by the parasite are discussed.

Animals↗

PubMed1996

Expansion and methylation status at FRAXE can be detected on EcoRI blots used for FRAXA diagnosis: analysis of four FRAXE families with mild mental retardation in males.

The original test for the analysis of the CCG expansion at the FRAXE locus involves Southern blot analysis of HindIII digests. We show that, by using a different probe, the FRAXE mutation can be detected easily on the same EcoRI or EagI+EcoRI blots as are used for detection of FRAXA. Unexpectedly, we found that both the expansion and methylation status can be determined on a single EcoRI digest, because of the presence of a methylation-sensitive EcoRI site very close to the CCG repeat. We thus detected in a series of mentally retarded individuals previously tested for FRAXA expansion a FRAXE proband who led to the identification of a large sibship (7 of 10 children carrying a mutation). We also show that two fragile X families without FRAXA mutation that previously have been described by Oberlé et al. have the FRAXE expansion. In another family also ascertained initially by cytogenetic finding of a fragile X site, we performed the combined cytogenetic and molecular prenatal diagnosis of a mutated male fetus. All nine males (>3 years old) in whom we found a methylated mutation had mild mental retardation. Our results suggest that the threshold of repeat length for abnormal methylation and fragile-site expression may be smaller at FRAXE than at FRAXA.

Adolescent↗

PubMed1995

Large scale survey of bovine babesiosis due to Babesia divergens in France.

Data on the epidemiology of bovine babesiosis in France were collected from two sources: a questionnaire sent to large animal veterinary surgeons and blood samples collected from cattle treated for clinical babesiosis. Babesia divergens was common and widespread. B major was found in only one sample. The disease was particularly widespread in north west, south west and central France. The mean clinical incidence was 0.4 per cent. The bimodal seasonality of the clinical cases was correlated with that of the tick vector (Ixodes ricinus). Of the affected animals 72.6 per cent were more than three years old.

Age Distribution↗