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1.
The objective of this study was to evaluate oxidative stress in lambs experimentally infected with Haemonchus contortus and supplemented with selenium and vitamin E. Twenty male Corriedale lambs were divided into four experimental groups with five animals each: G1 consisted of animals infected and supplemented with 0.2 mg/kg of live weight (LW) sodium selenite by intramuscular injection (IM); G2 consisted of animals infected with larvae and supplemented with 0.2 mg/kg LW sodium selenite IM and 2000 IU per animal of Vitamin E IM; G3 consisted of animals infected with larvae and supplemented with 2000 IU per animal of Vitamin E IM; and G4 consisted of animals infected with larvae. The animals were infected orally with 500 H. contortus larvae (L3) every 48 hours for 20 days. For biochemical analyses and eggs per grams of feces (EPG) evaluation, blood and feces were both collected at zero (T0), 20 (T1), 40 (T2) and 60 (T3) days. The weight of the animals was also measured at these times. Lower TBARS values were observed in the supplemented animals compared to the control group. The groups supplemented with Selenium exhibited blood GSH-Px activity higher than that of non-supplemented animals. Supplementation with selenium provided greater antioxidant protection against oxidative stress generated from experimental infection of lambs with H. contortus.  相似文献   

2.
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3.
This experiment was carried out to compare the worm burden and cellular responses in the abomasal mucosa and blood of Florida Native and Rambouillet lambs and also in animals produced by crosses of these two breeds (generations F1 and F2). Animals were exposed to infection by gastrointestinal nematodes on three different occasions. The first infection was natural, occurring while they were suckling lambs. After weaning, they were kept indoors for 53 days and then were allowed to graze a contaminated pasture for 50 days for a second natural infection. The third infection was an artificial challenge with 6000 Haemonchus contortus infective larvae. The highest mean fecal egg counts (FEC) values were found in Rambouillet lambs followed in decreasing order by F1, F2 and Florida Native lambs. Throughout the trial, most of the high mean packed cell volumes and plasma protein levels were recorded in the F2 lambs; in contrast, most of the low values were found in the Rambouillet lambs. During the natural infection period, the highest percentages of larvae in the fecal cultures of the lambs were Haemonchus. However, high percentages of Trichostrongylus larvae were found particularly in Florida Native lambs. The mean number of blood eosinophils increased after the artificial challenge, reached a peak 21 days after infection and then declined. The highest and lowest blood eosinophil means were recorded in F2 and Florida Native lambs, respectively. The H. contortus burden was significantly higher in Rambouillet and in F1 lambs than in Florida Native and F2 lambs (p < 0.05), while no significant differences were recorded among eosinophil, mast cell and globule leucocyte counts in the abomasal mucosa (p > 0.05). The highest correlation coefficient recorded at the end of this study was between FEC and worm burden (r = 0.7). These two parameters showed a moderate negative correlation with PCV, plasma protein and mast cell counts in the abomasal mucosa. The results obtained in this study indicate that crossbreeding Florida Native and Rambouillet sheep can be a rapid way to combine and improve the characteristics of these two breeds. The parasitological results were promising, however, more studies will be necessary to verify the impact of crossbreeding in other traits.  相似文献   

4.
The histological changes in the abomasal mucosa of pairs of worm-free ewes and lambs were compared at various stages after infection and reinfection with 350 Haemonchus contortus L3 per kg bodyweight. In terms of worm burdens the ewes were relatively resistant to reinfection compared with the lambs and the histological changes in the abomasum at most stages after infection were more marked in the adult animals. These included increases in the numbers of mast cells, globule leucocytes, eosinophils and IgA plasma cells in the mucosa.  相似文献   

5.
The effect of experimental haemonchosis on the number of tissue eosinophils, plasma cells and lymphocyte subpopulations was evaluated in the fundic abomasal region, the pyloric abomasal region and the abomasal lymph node of Blackbelly lambs, which are resistant to infection, and Columbia lambs, which are susceptible to infection. An increase in the number of tissue eosinophils and CD4+ and WC1(+)γδ T-cells was observed in the pyloric abomasal region of Blackbelly lambs and correlated with lower worm burden and greater resistance to infection. Increases in IgA+ plasma cells from the pyloric abomasal region were observed in both infected groups, but there was no difference between the groups. Therefore, increases in IgA+ plasma cells did not explain the resistance observed. Infection caused a significant increase in tissue eosinophils in the abomasal lymph node of Blackbelly lambs and a decrease in the number of CD4+ T-cells in lambs of both breeds. CD8+ T-cells and IgG+ and IgM+ plasma cells were not associated with either infection or resistance. In this work, clear differences were observed in the numbers of CD4+ and WC1(+)γδ T-cells, tissue eosinophils and IgA+ plasma cells between the abomasal regions studied. These differences indicate that the immunological response is not homogenous in all abomasal mucosa and that evaluating the response from a single abomasal region may not be representative of the cellular response across the abomasum.  相似文献   

6.
The physiological processes leading to the expression of the resilient phenotype, which allow animals to maintain a relatively higher production level during infection, have been investigated in lambs from a closed flock selected for 40 generations for high fleece weight (HFW), but with higher FEC and worm burdens than their unselected control (C) flock run in parallel. After recovery from surgery to implant abomasal cannulae, eight parasite-naïve lambs from each flock were infected intraruminally at 4.5 months-of-age with 50,000 Teladorsagia circumcincta L3. Blood, abomasal fluid and faecal samples were collected daily for measurement of serum gastrin and pepsinogen concentrations, blood eosinophils, abomasal pH and FEC. Four lambs from each flock were euthanased on Day 8 post-infection and the other four on Day 28 post-infection. At necropsy, abomasal contents and tissues were collected for worm counts, abomasal lymph nodes and fundic tissue for cytokine gene expression and fundic tissue for histopathology. Expression of resilience appeared to be age-dependent as there were no significant differences in either FEC or worm burden between lambs from the two flocks, unlike older HFW lambs in a previous study. Abomasal secretion did not differ between flocks. Histopathological changes were typical of parasitism: inflammatory cells, mainly eosinophils and lymphocytes, were numerous in nodular areas and there were fewer TGF-α positive parietal cells, many of which were vacuolated. By Day 28 p.i., globule leucocytes were present. Mucosal thickness was significantly greater on Day 8 than Day 28 p.i. (p = 0.000) and in C than HFW lambs. There were fewer parietal cells on Day 28 than on Day 8 p.i. (p = 0.003) for pooled data. Circulating eosinophil counts increased moderately in both groups, significantly less in the HFW lambs. Fewer tissue and blood eosinophils in the HFW than C group on Day 8 p.i. were consistent with cytokine gene expression patterns, particularly lower IL-5 levels. Worm count decreased by 90% by Day 28 p.i., along with declining tissue eosinophil counts and IL-13 gene expression and increasing IL-10 and IL-4 gene expression. Food intake was depressed less in the HFW lambs, suggesting that maintenance of appetite could be an important aspect of the physiological basis for resilience. Although the resilient phenotype was not apparent at the younger age, lesser effects on food intake, differences in ALN cytokine profiles and lower blood and tissue eosinophil numbers in the HFW lambs may lead to the expression of resilience when older.  相似文献   

7.
Cellular changes in the abomasal tissue and draining abomasal lymph nodes were examined after primary infection of lambs with Haemonchus contortus for 3, 5 or 27-36 days.Infection with H. contortus larvae resulted in a rapid and selective increase in the percentage of CD4(+) T-cells in the abomasal lymph node at 3 days post-infection (PI). By 5 days PI, the lymph node weight had increased two-fold; however, the percentage of lymphocyte populations in the abomasal lymph node resembled that seen in uninfected sheep. Lymph node weights remained at increased levels in the adult nematode infected sheep and down-regulation of B-cell surface markers (sIg and MHC Class II) was apparent in this group. Significant increases in the percentage of CD4(+) T-cells co-expressing MHC Class II, but not CD25, were observed in the larval infected groups except in adult nematode infected sheep. Increased numbers of eosinophils, CD4(+), gamma delta(+) T-cells and B-cells were found in the abomasal tissue by 5 days PI, but no further increases in these cell populations were observed in the adult nematode infected group. In contrast, the level of both lamina propria and intraepithelial mast cells observed in the abomasal mucosa was highest in the sheep carrying an adult nematode burden. These findings indicate that sheep are able to generate an early immune response to infection with H. contortus larvae, characterised by the activation of CD4 T-cells and B-cells in the draining lymph nodes and recruitment of eosinophils, CD4(+) and gamma delta-TCR,WC1(+) T-cells and B-cells in larval infected tissues. However, these changes do not seem to be maintained during infection with the adult parasite where increases in mast cell numbers dominate the local response, indicating that different parasite stages may induce distinct and possibly counteractive immune responses.  相似文献   

8.
The effects of host age and immune suppression on abomasal parasitic infection in sheep were investigated following single experimental oral infections with MHco3 (ISE), MHco4 (WRS) and MHco10 (CAVR) strains of Haemonchus contortus in naïve 5-month-old crossbred lambs (n = 1 per group) and 15-month-old Greyface sheep treated with methyl prednisolone acetate (n = 2 per group) or without corticosteroid treatment (n = 2 per group). Adult female H. contortus in 5-month-old lambs (n = 1 per group) shed on average 6.5, 3.1 and 8.0 times more eggs than in 15-month-old sheep (n = 4 per group) following infection with MHco3 (ISE), MHco4 (WRS) and MHco10 (CAVR) strains of H. contortus, respectively, over a period of 28 days following the commencement of patency. There was no obvious effect of age of sheep or corticosteroid treatment on the abomasal establishment of H. contortus or on in vitro assays for egg hatching or larval feeding at different concentrations of anthelmintics, although statistical analysis could not be performed due to the small group sizes.  相似文献   

9.
The effect of Haemonchus contortus infection in sheep fed with a moderate and high protein content diet was evaluated in two breeds of sheep. Forty-eight Ile de France and Santa Ines lambs were maintained indoors since birth, in worm-free conditions. The lambs were allocated after weaning in four groups of six animals per breed, which were either infected or remain uninfected and given access to either a moderately or highly metabolizable protein diet. The moderately and highly metabolizable protein diets were calculated to supply 75 and 129 g metabolizable protein per kg of dry matter (MP/kg DM), respectively. The infection consisted of a trickle infection with 300 infective larvae, three times a week, for 12 weeks. Significant differences were observed for mast cell, globule leukocyte and eosinophil counts in the abomasal mucosa of the infected groups compared to the control of both breeds (P<0.05), regardless of the diet supplied. Significantly higher IgA anti-L5 antibody was detected in the infected Santa Ines groups than in the infected Ile de France groups (P<0.05). Increased metabolizable protein supply resulted in larger body weight gain and higher packed cell volumes for both breeds (P<0.05). Both breeds showed an increased ability to withstand the pathophysiological effects of H. contortus infection when given access to the highly metabolizable protein diet. However, increased metabolizable protein supply resulted in reduced worm burdens in Santa Ines lambs but not in the Ile de France lambs (P<0.05). The present results show that the increase in protein content in growing lamb diets may benefit resistance and resilience to gastrointestinal parasites but that these benefits may vary among breeds.  相似文献   

10.
Two experiments were conducted to examine the influence of dietary protein on the pathophysiology of Haemonchus contortus in lambs of two breeds, namely Finn Dorset and Scottish Blackface. Erythrokinetic and metabolic studies using 51Cr-red cells, 59Fe-transferrin and 125I-albumin, and digestive efficiency and nitrogen balance measurements were conducted between four and six weeks after infection. Identical radioisotopic and nutritional studies were also conducted on pair-fed control lambs of both breeds. The results demonstrated that in normal control animals, there were no significant effects of diet or breed on any of the erythrokinetic, metabolic or nutritional parameters, with the possible exception of red cell survival which was considerably longer in the Finn Dorset lambs. However, in the infected animals diet and breed did influence those parameters. The severest effects were seen in the infected Finn Dorset lambs given the low protein diet. These animals had the highest level of abomasal blood loss and this was associated with low red cell volumes and high levels of both albumin catabolism and plasma iron turnover. These animals were also in negative nitrogen balance which was partly accounted for by a significantly greater urinary nitrogen loss compared with their pair-fed controls and partly due to the poorer digestibility of the crude protein fraction of the diet. In contrast, although the infected Scottish Blackface lambs had high levels of blood loss and associated pathophysiological changes, these did not differ between dietary treatments and were similar to the changes in the infected Finn Dorset lambs given the high protein diet.  相似文献   

11.
Abstract

AIMS: To compare the pharmacokinetics, distribution and efficacy (pharmacodynamic response) of intraruminal ivermectin (IVM) and moxidectin (MXD) administered at 0.2 and 0.4?mg/kg to naturally nematode-infected lambs, and to determine the ex vivo accumulation of these anthelmintics by Haemonchus contortus.

METHODS: Romney Marsh lambs, naturally infected with IVM-resistant H. contortus, were allocated to treatment groups based on faecal nematode egg counts. They received 0.2 or 0.4?mg/kg IVM or MXD (n=10 per group), or no treatment (Control; n=6), on Day 0. Samples from four animals from each treatment group, including abomasal parasites, were obtained on Day 1. Plasma samples were also collected from Day 0 to 14, and a faecal egg count reduction test (FECRT) and a controlled efficacy trial were carried out on Day 14. Concentrations of IVM and MXD in plasma, in abomasal and intestinal tissues and in H. contortus were evaluated by high-performance liquid chromatography. Additionally, the ex vivo drug accumulation of IVM and MXD by H. contortus was determined.

RESULTS: Peak plasma concentrations and the area under the concentration vs. time curve for both IVM and MXD were higher for 0.4 than 0.2?mg/kg treatments (p<0.05), but there were no differences for other parameters. Concentrations of IVM and MXD in the gastrointestinal target tissues and in H. contortus were higher compared to those measured in plasma. Concentrations of both drugs in H. contortus were correlated with those observed in the abomasal content (r=0.86; p<0.0001). The exposure of H. contortus to IVM and MXD was related to the administered dose. Mean FECRT and efficacy for removal of adult H. contortus was 0% for IVM at 0.2 and 0.4?mg/kg. For MXD, FECRT were >95% for both treatments, and efficacy against H. contortus was 85.1% and 98.1% for 0.2 and 0.4?mg/kg, respectively. The ex vivo accumulation of IVM and MXD in H. contortus was directly related to the drug concentration present in the environment and was influenced by the duration of exposure.

CONCLUSION: Administration of IVM and MXD at 0.4 compared with 0.2?mg/kg accounted for enhanced drug exposure in the target tissues, as well as higher drug concentrations within resistant nematodes. The current work is a further contribution to the evaluation of the relationship between drug efficacy and basic pharmacological issues in the presence of resistant parasite populations.  相似文献   

12.
Several parameters of immune competence were measured in lambs with genetic resistance to Haemonchus contortus and in lambs with average susceptibility to H contortus (random-bred). Increase in skinfold thickness following intradermal injection was greater in resistant lambs for concanavalin A and to a lesser extent for phytohaemagglutinin. Both mitogens induced infiltration of superficial and deep dermis by eosinophils, CD4+, CD8+ and T19+ lymphocytes, though the responses did not differ between groups. Primary but not secondary antibody responses to the T cell-dependent antigen, ovalbumin was greater in resistant lambs. In contrast, antibody responses to the T cell-independent antigen, Brucella abortus lipopolysaccharide, did not differ between groups. Taken together the data suggest that enhanced T lymphocyte function may contribute to the greater resistance to H contortus of genetically resistant lambs.  相似文献   

13.
Selection of resistant animals and host immunization have been proposed as alternative methods for the control of gastrointestinal nematode parasites. However, a better knowledge of the mechanisms involved in protective immunity against these parasites is required for the development of optimal strategies. In this study, 3 month old INRA 401 lambs (n = 81) were allocated into three groups: uninfected control, challenged either once (primary-infected animals) or twice (previously-infected animals) with 10,000 Haemonchus contortus L3. Uninfected control and challenged animals were sequentially sacrificed at 3, 7, 15 and 28 days post challenge. In both challenged groups, a clear Th2-oriented immune response was observed in the abomasal lymph node and mucosa. IL-4 and IL-13 mRNA over-expression, recruitment of eosinophils, mast cells and globule leukocytes and production of specific systemic IgG and mucosal IgA were observed earlier in previously-infected animals than in primary-infected ones. At 28 days post infection, no differences between intensities of these responses were observed between the challenged groups. Worm establishment rates were similar in previously-infected and primary-infected lambs. However, reductions of worm development, female fecundity and fecal egg output were observed in previously-infected sheep. We conclude that H. contortus infection in young INRA 401 lambs induced an unequivocal Th2 immune response resulting in the regulation of worm egg production without affecting their establishment.  相似文献   

14.
The addition of molybdenum (0.05 mmol kg-1 dry-matter) to the diet of lambs given a trickle infection of Haemonchus contortus larvae (500 third stage larvae d-1 over six weeks) reduced mean faecal egg counts (epg) from 3952 to 2312 +/- 402 by 32 days (P less than 0.02) and greatly reduced the mean number of worms recovered from the abomasum 14 days after infection ceased (907 compared with 4167: P less than 0.01). Infection reduced haemoglobin concentrations less in lambs given molybdenum although the difference was small relative to the reduction in worm burden. Lambs not given molybdenum had low intraepithelial mast cell counts in the abomasal mucosa and less abomasal hypertrophy than expected from abomasal parasitism. Molybdenum did not consistently reduce the copper status of the host or the parasite. Previous exposure to molybdenum greatly reduced protein but not proteinase activity in, or secreted by, adult worms cultured for eight hours. It is suggested that molybdenum either increased the inflammatory response which preceded worm rejection or that it indirectly enhanced that reaction by reducing the effectiveness of copper-dependent, anti-inflammatory enzymes in the gastrointestinal mucosa.  相似文献   

15.
The daily live weight gain (DLWG), faecal nematode egg counts (FEC), and packed cell volume (PCV) of Suffolk, Ile de France and Santa Inês ewe lambs were evaluated fortnightly for 56 days in the dry season (winter) and 64 days in the rainy season (summer) of 2001-2002. The animals were distributed in two similar groups, one located on Aruana and the other on Tanzania grass (Panicum maximum), in rotational grazing system at the Instituto de Zootecnia, in Nova Odessa city (SP), Brazil. In the dry season, 24 one-year-old ewe lambs were used, eight of each breed, and there was no difference (p > 0.05) between grasses for DLWG (100 g/day), although the Suffolk had higher values (p < 0.05) than the other breeds. In the rainy season, with 33 six-month-old ewe lambs, nine Suffolk, eight Ile de France and 16 Santa Inês, the DLWG was not affected by breed, but it was twice as great (71 g/day, p < 0.05) on Aruana as on Tanzania grass (30 g/day). The Santa Inês ewe lambs had the lowest FEC (p < 0.05) and the highest PCV (p < 0.05), confirming their higher resistance to Haemonchus contortus, the prevalent nematode in the rainy season. It was concluded that the best performance of ewe lambs on Aruana pastures in the rainy season is probably explained by their lower nematode infection owing to the better protein content of this grass (mean contents 11.2% crude protein in Aruana grass and 8.7% in Tanzania grass, p < 0.05) which may have improved the immunological system with the consequence that the highest PCV (p < 0.05) observed in those animals.  相似文献   

16.
This trial was carried out in Piracicaba, São Paulo State, Brazil, to comparatively evaluate the degree of resistance to naturally acquired gastrointestinal nematode infections in sheep of the following genetic groups: purebred Santa Ines (SI), SI crossbred with Dorper (DO × SI), Ile de France (IF × SI), Suffolk (SU × SI), and Texel (TE × SI). Fifteen ewes from each group were raised indoors until 12 months of age. At this age, they were moved to pasture that was naturally contaminated by nematode infective larvae and were evaluated from December to May, 2007. Rainfall ranged from 267 mm in January to 37 mm in April. Maximum and minimum mean temperatures ranged from 32.5 °C to 19.0 °C in March and from 25.9 °C to 12.8 °C in May. There was an increase in the mean number of eggs per gram of feces (EPG) after animals were placed on pasture with significant difference between the SI (80 EPG) and IF × SI (347 EPG) groups in January; and the DO × SI (386 EPG) and TE × SI (258 EPG) groups in May. The highest mean fecal egg count (FEC), 2073 EPG, was recorded for the TE × SI group in February. All groups showed a progressive reduction in body weight throughout the experiment of 12.0% (TE × SI) to 15.9% (SU × SI). In general, the animals with the highest FEC presented the lowest packed cell volumes (PCV); the highest correlation coefficient between FEC × PCV occurred in the SU × SI sheep in January (r = −0.70; P < 0.01). Similarly, there was an inverse relationship between FEC and blood eosinophil values, with the highest correlation coefficient in the TE × SI sheep in February (r = −0.64; P < 0.05). Immunoglobulin G (IgG) levels against Haemonchus contortus antigens increased in all groups as a result of the exposure to parasites and remained relatively constant until the end of the study, with the exceptions of SU × SI and TE × SI, which showed a rise in IgG levels during the last sampling that coincided with a reduction in mean FEC. In conclusion, crossbreeding Santa Ines sheep with any of the breeds evaluated can result in a production increase and the maintenance of a satisfactory degree of infection resistance, especially against H. contortus and Trichostrongylus colubriformis, the major nematodes detected in this flock.  相似文献   

17.
This study reports a functional characterization of a limited segment (QTL) of sheep chromosome 12 associated with resistance to the abomasal nematode Haemonchus contortus. The first objective was to validate the identified QTL through the comparison of genetically susceptible (N) and resistant (R) sheep produced from Martinik × Romane back-cross sheep. The R and N genotype groups were then experimentally infected with 10 000 H. contortus larvae and measured for FEC (every three days from 18 to 30 days post-challenge), haematocrit, worm burden and fertility. Significant differences in FEC and haematocrit drop were found between R and N sheep. In addition, the female worms recovered from R sheep were less fecund. The second step of the characterization was to investigate functional mechanisms associated with the QTL, thanks to a gene expression analysis performed on the abomasal mucosa and the abomasal lymph node. The gene expression level of a candidate gene lying within the QTL region (PAPP-A2) was measured. In addition, putative interactions between the chromosome segment under study and the top ten differentially expressed genes between resistant MBB and susceptible RMN sheep highlighted in a previous microarray experiment were investigated. We found an induction of Th-2 related cytokine genes expression in the abomasal mucosa of R sheep. Down-regulation of the PAPP-A2 gene expression was observed between naïve and challenged sheep although no differential expression was recorded between challenged R and N sheep. The genotyping of this limited region should contribute to the ability to predict the intrinsic resistance level of sheep.  相似文献   

18.
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19.
The efficacy of strategic anthelmintic control of liver flukes (Fasciola) and gastrointestinal (GI) nematodes on the performance of ewes and lambs on pasture was assessed on a farm in the highlands of Kenya. In May 1999, 45 Corriedale ewes, aged between 2 and 3 years, were ear-tagged, weighed and allocated randomly to three equal treatment groups based on body weight. Faecal samples taken at this time revealed low levels of strongyle-type eggs per gram of faeces (EPG) and the presence of liver fluke eggs in only a few of the animals. All the animals were then set stocked for 12 months on separate paddocks in an area endemic for both Fasciola and GI nematodes. The ewes in group 1 were given a combined anthelmintic treatment against Fasciola and GI nematodes during the periods recommended for the control of Fasciola in the area (February, June and October). The ewes in group 2 were given the combined treatments 3 weeks after the onset of both the short and long rainy seasons (November and April, respectively). Those in group 3 were given separate treatments for Fasciola (February, June and October) and nematodes (3 weeks after the onset of the rainy seasons). The anthelmintic treatment against Fasciola consisted of triclabendazole at 10 mg per kg body weight, and that against nematodes was levamisole at 10 mg per kg body weight.The nematode EPG for the ewes in group 1 were higher than in groups 2 and 3 during both rainy seasons. The nematode EPG did not differ significantly between groups 2 and 3. The prevalence of Fasciola eggs (number of ewes shedding eggs in a group) in the ewes in groups 1 and 3 remained very low throughout the study period compared to those in group 2. The highest birth weights and the weight gains of lambs were recorded for the group of ewes given separate anthelmintic treatments for Fasciola and nematodes (group 3). The results of this trial indicated that, in an area like Nyandarua District, where liver flukes and GI nematodes are important constraints to sheep production, the best practice is to give separate treatments for the two groups of parasites at the recommended times.  相似文献   

20.
Cellular and humoral local responses were investigated following repetitive artificial Oestrus ovis infections in lambs. The presence of larvae induced a huge local recruitment of either leucocytes (T and B lymphocytes, macrophages) or granulocytes (eosinophils, mast cells and globule leucocytes). This cellular response was more pronounced in the ethmoid and sinus (development sites of second and third instar larvae) than in the septum or turbinates where first instar larvae migrate. Infected lambs produced Oestrus ovis specific IgG and IgA antibodies in their mucus. This local humoral response was mainly directed against larval salivary gland antigens and not against larval digestive tract antigens. Compared to the control animals, the sinusal mucosa of infected animals was extremely thickened and the epithelium exhibited hyperplasia, metaplasia and eosinophilic exocytosis. The possible roles of these local immune responses in the regulation of O. ovis larvae populations in sheep are discussed.  相似文献   

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