878 research outputs found
Effects of the repeated distribution of sainfoin hay on the resistance and the resilience of goats naturally infected with gastrointestinal nematodes
Due to the high prevalence of anthelmintic resistance in goats, the need to explore novel approaches to control nematodes and
to reduce the exclusive reliance on chemotherapy is strongly demanded in this host species. In sheep, several studies have shown
that the consumption of tannin-rich legume forages was associated with positive effects on host resilience and resistance to
parasite infection. In goats, studies on such interactions between tanniferous plants and nematode infections remain few. The
objectives of the current study were to examine under natural conditions the effects of consumption of sainfoin hay by goats on
the parasite populations and on host resilience.
Eighteen adult cull goats naturally infected with Haemonchus contortus, Teladorsagia circumcincta and Trichostrongylus
colubriformis were used in the study. At the start of the assay, the goats were allocated into two groups, balanced according to
weight and the levels of egg excretion. The two groups grazed separate pastures for 3 months with similar stocking rates. Goats
from group S received each month indoors, for 7 days, sainfoin hay and control goats (group C) received hay of ryegrass. The
diets in both groups were made isoenergetic and isoproteic and the refusals measured. Individual parasitological and
pathophysiological measurements were performed fortnightly in order to compare host resistance and resilience. At the
end of the study, five goats per group were necropsied. The distribution of sainfoin was associated with: (1) a higher consumption
of hay; (2) significant, lower levels of nematode egg excretion which was associated with a decrease in worm fertility but no
change in worm population; however, the number of intestinal worms was reduced by 50% in group S; (3) a better host
resilience. In particular, after 2 months of grazing, two control goats died and half of the remaining animals needed to be treated
whereas this was not the case in group S. These differences were related to significant changes in pepsinogen and phosphate
values (PCV) but not in pepsinogen and phosphate concentrations. These results demonstrate that a repeated distribution of
sainfoin hay to grazing goats might be beneficial in regard of pasture contamination and host resilience. They suggest that
administration of sainfoin hay might represent a valuable alternative and adjunct to reduce nematode infections in dairy goat flock.
# 2004 Elsevier B.V. All rights reserved
Effects of condensed tannins on goats experimentally infected with Haemonchus contortus.
Although the use of tanniferous plants or condensed tannins as an alternative to anthelmintics to
control gastrointestinal nematodes has been largely documented in sheep, studies remain scarce in
goats. The objective of this study was therefore to assess the possible impact of condensed tannins
in goats infected with adult Haemonchus contortus. Two groups of cull goats were experimentally
infected with 10.000 L3 of H. contortus. After 4 weeks, quebracho extracts, representing 5%
of the diet DM, were administered for 8 days to one of the two groups. Goats of the second
group remained as controls. One week after the end of quebracho administration, the goats were
euthanised. Individual egg excretion and pathophysiological parameters were measured weekly
during the study. At the end of the study, worm counts were assessed and histological samples
from the abomasa were taken to count the numbers of mucosal mast cells, globule leukocytes
and eosinophils. The administration of tannins was associated with a significant decrease in egg
excretion, which persisted until the end of experiment. This reduction was not associated with
any difference in worm number but with a significant decrease in female fecundity. No significant
changes in the mucosal density of the three inflammatory cell types were detected between the
two groups. These results indicate that the major consequence of tannin consumption in goats is a
reduction in worm fecundity and egg output, which does not seem related to significant changes in
the local mucosal response
Differences in receptivity to gastrointestinal infections with nematodes in dairy ewes: Influence of age and of the level of milk production
Resistance to anthelmintics in populations of gastrointestinal nematodes is a major concern in small ruminants. One solution
to limit the spread of anthelmintic resistance is to apply treatments selectively by targeting the most susceptible animals within
a flock. In dairy goats, previous studies have shown that, within a flock, goats in first lactation and those with high level of milk
production were highly receptive to nematode infections. These results provided the rationale for targeted treatments. In dairy
ewes, such epidemiological information on possible factors modulating the susceptibility to parasitism were still lacking. The
objective of the current study was therefore to examine differences in the level of parasite infection and in the pathophysiological
consequences in dairy ewes, depending on the age or on the level of milk production. In three farms, parasite egg excretion, and the
serum concentrations of pepsinogen and inorganic phosphate were compared on one hand between primiparous and multiparous
ewes; on the other hand, between ewes with the highest and the lowest level of milk production, within a cohort of 3â5-year
old animals. Overall, the results did not indicate significant differences for both either the parasitological or pathophysiological
measurements depending on the level of milk production. In contrast, significant differences were found according to age,
indicating higher levels of infections in the primiparous ewes than in the multiparous ones and suggesting that this category of
animals represents a particular parasitic risk within a flock
Effects of distribution of quebracho extracts on experimental Haemonchus contortus infections in goats
The effects of tannins on adult populations of Haemonchus contortus, Trichostrongylus colubriformis and Teladorsagia circumcincta
in goats are characterised mainly by a decrease in egg excretion without any significant changes in worm number. In contrast,
the impact of tannins on T. colubriformis or T. circumcincta third-stage larvae (L3) is associated with a significant reduction in worm
establishment. The objective of the present study was to examine the effects of quebracho extract tannins on H. contortus L3. The
consequences of consumption of sainfoin hay were also examined.
Twenty-one naıšve kids were divided into three experimental groups. Group Q received quebracho extract and group S received
sainfoin hay from days D3 to D5. Group C remained as an infected control group. All kids received 1500 L3 H. contortus on D0, D1
and D2. On D18, post-infection, the kids were slaughtered and the worm populations compared in the different groups. Compared
to the control values, the worm counts decreased, respectively, by 33% and 38% in groups Q and S but the differences were not significant.
No differences were found in pathophysiological measurements between the three groups. The results confirm differences in
tannin effect according to nematode species but not parasitic stage
Effects of various meteorological conditions and spatial emissionresolutions on the ozone concentration and ROG/NO<sub>x</sub> limitationin the Milan area (I)
The three-dimensional photochemical model UAM-V is used to investigate the effects of various meteorological conditions and of the coarseness of emission inventories on the ozone concentration and ROG/NO<sub>x</sub> limitation of the ozone production in the Po Basin in the northern part of Italy. As a base case, the high ozone episode with up to 200ppb on 13 May 1998 was modelled and previously thoroughly evaluated with measurements gained during a large field experiment. Systematic variations in meteorology are applied to mixing height, air temperature, specific humidity and wind speed. Three coarser emission inventories are obtained by resampling from 3x3km<sup>2</sup> up to 54x54km<sup>2</sup> emission grids. The model results show that changes in meteorological input files strongly influence ozone in this area. For instance, temperature changes peak ozone by 10.1ppb/°C and the ozone concentrations in Milan by 2.8ppb/°C. The net ozone formation in northern Italy is more strongly temperature than humidity dependent, while the humidity is very important for the ROG/NO<sub>x</sub> limitation of the ozone production. For all meteorological changes (e.g. doubling the mixing height), the modelled peak ozone remains ROG limited. A strong change towards NO<sub>x</sub> sensitivity in the ROG limited areas is only found if much coarser emission inventories were applied. Increasing ROG limited areas with increasing wind speed are found, because the ROG limited ozone chemistry induced by point sources is spread over a larger area. Simulations without point sources tend to increase the NO<sub>x</sub> limited areas
The UV Continuum of Quasars: Models and SDSS Spectral Slopes
We measure long (2200-4000 ang) and short (1450-2200 ang) wavelength spectral
slopes \alpha (F_\nu proportional to \nu^\alpha) for quasar spectra from the
Sloan Digital Sky Survey. The long and short wavelength slopes are computed
from 3646 and 2706 quasars with redshifts in the z=0.76-1.26 and z=1.67-2.07
ranges, respectively. We calculate mean slopes after binning the data by
monochromatic luminosity at 2200 ang and virial mass estimates based on
measurements of the MgII line width and 3000 ang continuum luminosity. We find
little evidence for mass dependent variations in the mean slopes, but a
significant luminosity dependent trend in the near UV spectral slopes is
observed with larger (bluer) slopes at higher luminosities. The far UV slopes
show no clear variation with luminosity and are generally lower (redder) than
the near UV slopes at comparable luminosities, suggesting a slightly concave
quasar continuum shape. We compare these results with Monte Carlo distributions
of slopes computed from models of thin accretion disks, accounting for
uncertainties in the mass estimates. The model slopes produce mass dependent
trends which are larger than observed, though this conclusion is sensitive to
the assumed uncertainties in the mass estimates. The model slopes are also
generally bluer than observed, and we argue that reddening by dust intrinsic to
the source or host galaxy may account for much of the discrepancy.Comment: To be published in ApJ, 18 pages, 10 figure
Role of ammonia in European air quality with changing land and ship emissions between 1990 and 2030
The focus of this modeling study is on the role of ammonia in European air quality in the past as well as in the future. Ammonia emissions have not decreased as much as the other secondary inorganic aerosol (SIA) precursors â nitrogen oxides (NOx) and sulfur dioxide (SO2) â since the 1990s and are still posing problems for air quality and the environment. In this study, air quality simulations were performed with a regional chemical transport model at decadal intervals between 1990 and 2030 to understand the changes in the chemical species associated with SIA under varying land and ship emissions. We analyzed the changes in air concentrations of ammonia, nitric acid, ammonium, particulate nitrate and sulfate as well as changes in the dry and wet deposition of ammonia and ammonium. The results show that the approximately 40â% decrease in SIA concentrations between 1990 and 2010 was mainly due to reductions in NOx and SO2 emissions. The ammonia concentrations on the other hand decreased only near the high-emission areas such as the Netherlands and northern Italy by about 30â%, while there was a slight increase in other parts of Europe. Larger changes in concentrations occurred mostly during the first period (1990â2000). The model results indicate a transition period after 2000 for the composition of secondary inorganic aerosols due to a larger decrease in sulfate concentrations than nitrate. Changes between 2010 and 2030 â assuming the current legislation (CLE) scenario â are predicted to be smaller than those achieved earlier for all species analyzed in this study. The scenario simulations suggest that if ship emissions will be regulated more strictly in the future, SIA formation will decrease especially around the Benelux area, North Sea, Baltic Sea, English Channel and the Mediterranean region, leaving more ammonia in the gas phase, which would lead to an increase in dry deposition. In the north of the domain, the decrease in SIA would be mainly due to reduced formation of particulate nitrate, while the change around the Mediterranean would be caused mainly by decreased sulfate aerosol concentrations. One should also keep in mind that potentially higher temperatures in the future might increase the evaporation of ammonium nitrate to form its gaseous components NH3 and HNO3. Sensitivity tests with reduced NOx and NH3 emissions indicate a shift in the sensitivity of aerosol formation from NH3 towards NOx emissions between 1990 and 2030 in most of Europe except the eastern part of the model domain.The focus of this modeling study is on the role of ammonia in European air quality in the past as well as in the future Ammonia emissions have not decreased as much as the other secondary inorganic aerosol (SIA) precursors - nitrogen oxides (NOx) and sulfur dioxide (SO2) - since the 1990s and are still posing problems for air quality and the environment. In this study, air quality simulations were performed with a regional chemical transport model at decadal intervals between 1990 and 2030 to understand the changes in the chemical species associated with SIA under varying land and ship emissions. We analyzed the changes in air concentrations of ammonia, nitric acid, ammonium, particulate nitrate and sulfate as well as changes in the dry and wet deposition of ammonia and ammonium. The results show that the approximately 40 % decrease in SIA concentrations between 1990 and 2010 was mainly due to reductions in NOx and SO2 emissions. The ammonia concentrations on the other hand decreased only near the high-emission areas such as the Netherlands and northern Italy by about 30 %, while there was a slight increase in other parts of Europe. Larger changes in concentrations occurred mostly during the first period (1990-2000). The model results indicate a transition period after 2000 for the composition of secondary inorganic aerosols due to a larger decrease in sulfate concentrations than nitrate. Changes between 2010 and 2030 - assuming the current legislation (CLE) scenario - are predicted to be smaller than those achieved earlier for all species analyzed in this study. The scenario simulations suggest that if ship emissions will be regulated more strictly in the future, SIA formation will decrease especially around the Benelux area, North Sea, Baltic Sea, English Channel and the Mediterranean region, leaving more ammonia in the gas phase, which would lead to an increase in dry deposition. In the north of the domain, the decrease in SIA would be mainly due to reduced formation of particulate nitrate, while the change around the Mediterranean would be caused mainly by decreased sulfate aerosol concentrations. One should also keep in mind that potentially higher temperatures in the future might increase the evaporation of ammonium nitrate to form its gaseous components NH3 and HNO3. Sensitivity tests with reduced NOx and NH3 emissions indicate a shift in the sensitivity of aerosol formation from NH3 towards NOx emissions between 1990 and 2030 in most of Europe except the eastern part of the model domain.Peer reviewe
Recrudescence des infections animales Ă Welchia perfringens A
I. â 51 foyers dâinfections animales Ă W. perfringens A ont Ă©tĂ© analysĂ©s depuis 1949 Ă lâInstitut Pasteur. II. â La moyenne annuelle de la pĂ©riode 1949-1959 a brusquement augmentĂ© en 1960-1961, annĂ©es humides. III. â Toutes les espĂšces domestiques sont susceptibles dâĂȘtre touchĂ©es et prĂ©sentent aprĂšs un tableau rapide de symptĂŽmes trĂšs variĂ©s, une mortalitĂ© trĂšs Ă©levĂ©e. IV. â La prophylaxie et la thĂ©rapeutique, trĂšs dĂ©cevantes, sont discutĂ©es ; il semble quâil faille revenir Ă la vaccination monovalente anti-A dans les aires infectĂ©es et traiter trĂšs prĂ©cocement les animaux par la sĂ©rothĂ©rapie monovalente associĂ©e avec les sulfa mides et les antibiotiques dâaffinitĂ© intestinale
Self-Lensing Models of the LMC
All of the proposed explanations for the microlensing events observed towards
the LMC have difficulties. One of these proposed explanations, LMC
self-lensing, which invokes ordinary LMC stars as the long sought-after lenses,
has recently gained considerable popularity as a possible solution to the
microlensing conundrum. In this paper, we carefully examine the set of LMC
self-lensing models. In particular, we review the pertinent observations made
of the LMC, and show how these observations place limits on such self-lensing
models. We find that, given current observational constraints, no purely LMC
disk models are capable of producing optical depths as large as that reported
in the MACHO collaboration 2-year analysis. Besides pure disk, we also consider
alternate geometries, and present a framework which encompasses the previous
studies of LMC self-lensing. We discuss which model parameters need to be
pushed in order for such models to succeed. For example, like previous workers,
we find that an LMC halo geometry may be able to explain the observed events.
However, since all known LMC tracer stellar populations exhibit disk-like
kinematics, such models will have difficulty being reconciled with
observations. For SMC self-lensing, we find predicted optical depths differing
from previous results, but more than sufficient to explain all observed SMC
microlensing. In contrast, for the LMC we find a self-lensing optical depth
contribution between 0.47e-8 and 7.84e-8, with 2.44e-8 being the value for the
set of LMC parameters most consistent with current observations.Comment: 20 pages, Latex, 14 figures, submitted to Ap
A Quantitative Comparison of SMC, LMC, and Milky Way UV to NIR Extinction Curves
We present an exhaustive, quantitative comparison of all of the known
extinction curves in the Small and Large Magellanic Clouds (SMC and LMC) with
our understanding of the general behavior of Milky Way extinction curves. The
R_V dependent CCM relationship and the sample of extinction curves used to
derive this relationship is used to describe the general behavior of Milky Way
extinction curves. The ultraviolet portion of the SMC and LMC extinction curves
are derived from archival IUE data, except for one new SMC extinction curve
which was measured using HST/STIS observations. The optical extinction curves
are derived from new (for the SMC) and literature UBVRI photometry (for the
LMC). The near-infrared extinction curves are calculated mainly from 2MASS
photometry supplemented with DENIS and new JHK photometry. For each extinction
curve, we give R_V = A(V)/E(B-V) and N(HI) values which probe the same dust
column as the extinction curve. We compare the properties of the SMC and LMC
extinction curves with the CCM relationship three different ways: each curve by
itself, the behavior of extinction at different wavelengths with R_V, and
behavior of the extinction curve FM fit parameters with R_V. As has been found
previously, we find that a small number of LMC extinction curves are consistent
with the CCM relationship, but majority of the LMC and all of the SMC curves do
not follow the CCM relationship. For the first time, we find that the CCM
relationship seems to form a bound on the properties of all of the LMC and SMC
extinction curves. This result strengthens the picture of dust extinction
curves exhibit a continuum of properties between those found in the Milky Way
and the SMC Bar. (abridged)Comment: 18 pages, 10 figures, ApJ in pres
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