Artificial induction of red gut in sheep

Eight out of 10 lambs died within six to 11 hours after occlusion of the cranial mesenteric blood vessels by a snare placed around both the artery and vein. Death resulted from shock and was accompanied by post mortem findings identical to those seen in red gut. It is suggested that the cause of death in the naturally occurring disease is from arrested mesenteric blood flow following intestinal torsion.     

Dual oxidase 2 and glutathione peroxidase gene expression are elevated in hyperimmunized sheep challenged with Haemonchus contortus

A sequential biopsy sampling method was used to investigate oxidant and antioxidant gene responses in resistant sheep challenged with Haemonchus contortus larvae or a sham saline challenge. The expression of key sheep oxidant and antioxidant producing genes were measured in sequential samples removed from the abomasums at days 0, 1, 2, 3, 5, 7 and 28 post challenge. Gene expression levels at each time point were compared to expression at day 0, and levels of the various genes were also correlated to other markers of infection including immune cell counts and cytokine gene expression. The early response to larval challenge infection in resistant animals was marked by a divergence of two groups of host oxidant producing genes: the dual oxidase group (DUOX2/DUOXA2) showing increases in expression to day 7, while members of the phagocytic NADPH oxidase (PHOX) group showed significant decreases in expression. The change in DUOX2 expression between days zero and seven, when host resistance to infection is mediated, was negatively correlated to final worm burden suggesting NADPH oxidase expression may play a role in parasite expulsion. Expression of the DUOX group oxidants was positively correlated to expression of the Th2 cytokine IL4. Changes in host antioxidant pathways between different members of the glutathione peroxidase family (intestinal and plasma GPX) and genes involved in glutathione metabolism were also observed. This first study of the putative roles of oxidant production by the dual oxidase group, antioxidant glutathione pathways, immune cell populations, and cytokine profiles, in the development of resistance to infection by hyperimmune sheep are discussed.     

屠宰羊肺脏内寄生虫感染情况调查

羊肺脏是可供人们食用的副产品，所以羊肺脏内寄生虫的存在，不但影响羊的生长发育，而且还会对肉品卫生质量造成一定的影响，因此加强羊肺脏寄生虫病的检疫工作，在寄生虫病防治和食品卫生安全方面都具有重要的意义。为了给兽医防治和动物检疫部门提供依据，笔者于2004年对铁岭地区羊肺脏内寄生虫感染情况进行了抽样调查。     

Benzimidazole resistance in Trichostrongylus axei in sheep: long-term monitoring of affected sheep and genotypic evaluation of the parasite

This is the first report of benzimidazole (BZ) resistance in the nematode Trichostrongylus axei in sheep. Trichostrongylus axei infects several species of herbivores including sheep, cattle and horses, and the emergence of anthelmintic resistance could lead to significant problems in its control. Benzimidazole resistance in two sheep flocks in central France was detected by post-treatment worm counts. The sequencing of a central region of the isotype 1 beta-tubulin gene from adult T. axei recovered post-mortem revealed only one, non-synonymous single nucleotide polymorphism at position 200 (Phe200Tyr), which had already been reported for other nematodes. Seven years after BZ treatment ceased, T. axei helminths present were still resistant to BZ suggesting these parasites do not revert to susceptibility to this anthelmintic, even when the selection pressure had been removed for many years. The findings also highlight major changes in the make-up of the nematode burden in sheep flocks that accompanies the emergence of BZ resistance.     

A method for the interpretation of parasite egg counts in faeces of sheep

A new method for the interpretation of strongyloid egg counts in faeces in sheep flocks is proposed. The "Flock Parasitism Index" (FPI) is based on three epizootiological concepts: extent of parasitism, distribution of its intensity, and risk of pasture contamination by eggs. In the estimation of FPI from a number of faecal samples from different animals in a flock, the percentage of parasitized sheep and the distribution of parasitized animals of the sample into the classical categories of "low", "moderate" and "high" from the number of eggs per gram of faeces (EPG) and the arithmetic mean of EPG of the sample are considered. The pathogenic and epizootiological importance of each one of the "low", "moderate" and "high" categories are considered to be 0.1, 0.5 and 1, respectively. From the relationship between EPG and worm burdens, probabilities for "low", "moderate" and "high" distributions are calculated, and from the percentages of worm burdens estimated and their levels of confidence at 95% it is suggested that values of FPI equal to 2.0 must be considered as the limit of parasitism where economic losses are tolerable.     

Antibody development and cellular immune responses in sheep immunized and challenged with Sarcocystis tenella sporocysts

Four specific-pathogen-free (SPF) sheep were experimentally infected with 10(3) or 10(4) Sarcocystis tenella (syn. S. ovicanis) sporocysts and another two sheep served as uninfected controls. All sheep were challenged 49 days later by infection with 2.5 X 10(5) sporocysts and their humoral and cellular responses to infection and challenge were assessed weekly by enzyme immunoassays and lymphocyte transformation assays. The control sheep died from acute sarcocystosis 29-30 days after challenge, whereas the immunized sheep survived and were protected against acute disease. Specific IgM and IgG antibodies were detected in the immunized sheep from 28 days after infection onwards. Lymphocytes collected before and after challenge did not exhibit any significant differences in their responses to stimulation with S. tenella cystozoite or sporozoite antigens. Furthermore, lymphocytes collected before challenge did not differ from the controls in their responses to stimulation with the mitogens lipopolysaccharide or phytohaemagglutinin. However, lymphocytes collected after challenge did exhibit increased blastogenic responses to stimulation with both mitogens from 21-28 days after challenge onwards. The infected sheep were necropsied 46 days after challenge, and histological and ultrastructural studies revealed numerous infiltrates of lymphocytes, histiocytes and plasma cells in the skeletal muscles, sometimes in association with degenerating parasitic cysts and macrophage myophagia. Parasites were not completely eliminated nor prevented from further establishment, therefore the protective immunity was not sterile but rather a state of premunition.     

丙硫苯咪唑驱除绵羊体内寄生虫的增重试验

目的观察丙硫苯咪唑对绵羊体内寄生虫的驱除效果,以及驱除体内寄生虫对绵羊的增重作用。方法选择自然放牧的青年绵羊80只,分为对照组和试验组,给药后分期检查虫卵和称重,最后进行统计分析。结果按20 mg/kg.BW剂量投服药物残效期大约能维持30 d左右。试验结束后试验组比对照组每只绵羊平均多增重4.1 kg。结论丙硫苯咪唑的驱虫作用广谱、安全,对绵羊体内多种寄生虫的驱除效果确实。体内驱虫对绵羊增重作用明显,经济效益可观。     

Survey of anthelmintic resistance in Western Australian sheep flocks 2. Relationship with sheep management and parasite control practices

Owners of 116 farms, whose flocks had been tested for anthelmintic resistance, were interviewed to determine their use of various sheep management and parasite control practices and their knowledge and adoption of recommended procedures for the prevention and control of resistance. Farmers knowledge of current recommendations related mainly to changing drenches and drench groups. Other aspects of the recommended program including reduction of drenching frequency and the use of alternative management strategies were not considered as important by farmers. For most questions a high proportion of farmers (greater than 20%) had no opinion. Associations between various strategies for nematode control and resistance of Trichostrongylus and Teladorsagia to thiabendazole and levamisole were examined. These relationships differed between anthelmintics and nematode genera. A number of factors were related to resistance of one or both nematode genera to one or both anthelmintic groups. These factors included flock size, percentage of ewes in the flock, cattle number, main sheep production activity, grazing strategy, frequency of drenching, changes in the frequency of drenching, number of summer drenches and the method of estimating dose rates. It was concluded that the methods employed to control anthelmintic resistance may vary with the nematode, its resistance status and the anthelmintic to which it is exposed. Modifications to the previously recommended program have been proposed which incorporate selection of the anthelmintic to be used following a test for anthelmintic resistance.     

杂交猪IL-2和IL-6全基因克隆及序列分析

为研究杂交猪白细胞介素2(IL-2)和白细胞介素6(IL-6)在机体免疫应答中的作用,将杂交猪外周血淋巴细胞在伴刀豆球蛋白A(Con A)的刺激下进行体外培养后,提取淋巴细胞总RNA,应用RT-PCR技术扩增出杂交猪淋巴细胞IL-2和IL-6的cDNA,克隆到pMD18-T载体上并测序.测序结果表明:杂交猪IL-2基因核苷酸序列与参考序列的同源性为100%;IL-6基因核苷酸序列与GenBank登录的参考序列的核苷酸同源性在99.8%～100%之间,推导氨基酸同源性在99.1%～100%之间.     

白细胞介素-6对猪脂肪细胞脂肪分解的影响

为了研究白细胞介素(Interleukin,IL)-6对猪脂肪细胞脂肪分解的影响及其分子机制,分化的猪脂肪细胞用不同浓度的IL-6(0、25、50、75、100 ng·mL-1)处理24或48 h.通过测定培养液中的甘油浓度检测脂肪细胞的脂解率;采用形态学观察检测脂肪细胞中甘油三酯积聚量的变化;分别用RT-PCR和Western blot检测脂肪细胞中perilipin A、PPAR γ2(Peroxisome proliferato-activated receptor-gamma2)、HSL(Hormone-sensitive lipase)和AT-GL(Adipose triglyceride lipase)的mRNA及蛋白表达.结果显示,IL-6以剂量和时间依赖性的方式刺激猪脂肪细胞的脂肪分解,同时PPAR γ2和perilipin A的mRNA及蛋白表达被显著下调;HSL的mRNA表达达著上调,但其蛋白表达水平并未发生显著改变;ATGL的mRNA和蛋白表达均未发生显著改变.上述研究结果表明,IL-6通过抑制PPAR γ2及其靶基因perilipin A的表达直接刺激猪脂肪细胞的脂肪分解.     

The MHC class II region and resistance to an intestinal parasite in sheep

SUMMARY: RFLP analysis was used to investigate the effect of genetic variation in the Major Histocompatibility Complex (MHC) class II region on resistance of sheep to the intestinal parasite Trichostrongylus colubriformis, using faecal egg count (fec) as the measure of resistance. RFLP analysis of DNA from 335 sheep with the restriction enzymes TaqI, PvuII and HindIII, and DRB, DQA and DQB human class II MHC cDNA clones, revealed 238 bands, of which 233 were polymorphic. Sixteen bands were associated with a significant effect on fec, when analysed using a mixed model, best linear unbiased prediction statistical methods. However, when p values were corrected for the number of bands tested the associations were no longer significant. While no individual band had a significant effect on fec, Fisher's X(2) test of the distribution of p-values showed that RFLP bands, when considered together, do account for a significant proportion of variation in fec. One hundred and thirteen offspring from 11 halb-sib families were classified according to which MHC haplotype they had inherited from their sire. While there was overall no convincing statistical evidence of an effect of MHC haplotype on resistance, results in one family showed evidence for a repeatable MHC effect. ZUSAMMENFASSUNG: Die MHC-Klasse II Region und Resistenz gegenüber Darmparasiten beim Schaf RFLP Analyse betrifft die Auswirkung genetischer Unterschiede im Haupthistokompatibilit?ts-Komplex (MHC) Klasse II Region auf Resistenz von Schafen gegen den Darmparasiten Trichostrongylus colubriformis, wobei die f?kale Eizahl (fec) als Ma? der Resistenz verwendet worden ist. Die RFLP-Analyse der DNA von 335 Schafen mit Restriktionsenzymen TaqI, PvuII und HndIII und DRB, DQA und DQB menschlicher Klasse II MHC cDNA Klone ergab 238 Bande, wovon 233 polymorph waren. 16 Bande waren mit einer signifikanten Wirkung auf fec verbunden, wobei zur Analyse das gemischte Modell der BLUP verwendet worden ist. Allerdings, nach Korrektur der p-Werte für die Zahl der geprüften Bande zeigt sich die Assoziation nicht l?nger als signifikant. W?hrend kein individuelles Band eine signifikante Wirkung auf FEC zeigte, ergab Fisher's test hinsichtlich Verteilung der p-Werte Signifikanz bei Gesamtbetrachtung. 113 Nachkommen von 11 Halbgeschwister-Familien wurden nach dem MHC Haplotyp des Vatertieres klassifiziert. Es ergab sich kein insgesamt überzeugender statistischer Hinweis auf Wirkung der MHC Haplotypen, doch in einer Familie Hinweis auf wiederholbare MHC Effekte.     

Growth performance and gut health of Escherichia coli–challenged weaned pigs fed canola meal-containing diet

An experiment was conducted to evaluate the effects of including canola meal (CM) in diets for weaning pigs challenged with a F18 strain of Escherichia coli on growth performance and gut health. A total of 36 individually housed weaned pigs (initial body weight [BW] = 6.22 kg) were randomly allotted to one of the three diets (12 pigs/diet). The three diets were corn–soybean meal (SBM)-based basal diet (control diet) and the basal diet with 0.3% zinc oxide, 0.2% chlortetracycline, and 0.2% tiamulin (antibiotic diet) or with 20% CM diet. The diets were fed in two phases: Phase 1: days 0 to 7 and Phase 2: days 7 to 20. All pigs were given an oral dose of 2 × 10⁹ CFU of F18 strain of E. coli on day 7. Fecal score was assessed daily throughout the trial. Dietary antibiotics increased (P < 0.05) overall average daily gain (ADG) and average daily feed intake (ADFI) compared by 48% and 47%, respectively. Dietary CM increased (P < 0.05) overall ADG and ADFI by 22% and 23%, respectively; but the ADG and ADFI values for CM-containing diet did not reach those for the antibiotics-containing diet. Dietary antibiotics reduced (P < 0.05) fecal score; however, dietary CM unaffected fecal score. Dietary antibiotics decreased (P < 0.05) liver weight per unit live BW by 16% at day 20, whereas dietary CM did not affect liver weight per unit live BW (29.2 vs. 28.6). Also, dietary antibiotics increased (P < 0.05) serum triiodothyronine and tetraiodothyronine levels for day 14, whereas dietary CM did not affect the serum level of these hormones. Dietary antibiotics reduced (P < 0.05) the number white blood cells and neutrophils by 38% and 43% at day 20, respectively, whereas dietary CM tended to reduce (P = 0.09) the number white blood cells by 19% at day 20. The number white blood cells for CM diet tended to be greater (P < 0.10) than that for antibiotics diet. The dietary antibiotics decreased (P < 0.05) the concentration of individual volatile fatty acids and hence of total volatile fatty acid in cecum by 61% at day 20, whereas dietary CM decreased (P < 0.05) cecal butyric acid concentration by 61% and tended to reduce (P < 0.10) total volatile fatty acid concentration by 30% at day 20. In conclusion, the dietary inclusion of 20% CM improved ADG and tended to reduce white blood cell counts. Thus, inclusion of CM in antibiotics-free corn-SBM-based diets for weaned pigs that are challenged with F18 strain of E. coli can result in their improved performance partly through a reduction of the inflammatory response.     

Control of anthelmintic resistant endoparasites in a commercial sheep flock through parasite community replacement

An effort was undertaken to replace a community of sheep endoparasites that had been classified as resistant to levamisole and albendazole with a community of more susceptible parasites using a dilution approach that could be integrated into the management of a commercial flock. For this study, pastures on this sheep farm were divided into two areas: north and south. Strategically timed anthelmintic treatments combined with pasture management reduced to nondetectable levels the endemic community of anthelmintic resistant parasites in this flock and on these pastures by early summer. A group of 102 ewes, lambs, and rams were experimentally infected with third stage larvae from the more susceptible community of parasites. These sheep then seeded the south pastures with the new parasite community, while sheep on the north pastures maintained the endemic resistant community. Despite its insensitivity as a technique for detecting anthelmintic resistance, fecal egg count reduction tests at the end of the grazing season indicated that the more susceptible parasites were present on the south pastures while resistant parasites were present on the north.The following grazing season, similar protocols were used to introduce the more susceptible parasites onto the north pastures. At the end of the grazing season, fecal egg count reduction tests indicated that the new community of parasites had become established on both groups of pastures of the farm.     

Attempts to control haemonchosis in grazing ewes by vaccination with gut membrane proteins of the parasite

A vaccination trial was conducted to evaluate the potential benefit of Haemonchus contortus gut membrane proteins as vaccine antigens under field conditions in Louisiana. The trial was conducted in the summer of 1996 in a flock of ewes grazing pasture naturally infected with H. contortus. Ewes were randomly assigned to three treatment groups (vaccine, adjuvant only, and saline) and fecal egg counts (FEC, measured as eggs per gram of feces), packed cell volumes (PCV), and antibody levels were monitored fortnightly for 12 weeks. It was shown by FEC that there were large individual variations in susceptibility to H. contortus in both vaccinated and non-vaccinated sheep, a finding which could have masked differences between treatments when analyzed by conventional statistical methods. Based on their egg counts before the period when the vaccination could have had an effect, all ewes were categorized as 'susceptible' or 'relatively resistant'. The significance of differences between FEC, PCV and antibody responses of vaccinated and control sheep were tested separately for the 'susceptible' and 'relatively resistant' category. The 'susceptible' vaccinates shed 65% fewer worm eggs during the period when the vaccine could have had an effect, but the difference was only significant on Week 6 post-vaccination. In these experiments, it was difficult to completely exclude the confounding effect of having 'relatively resistant' sheep in the control group. More studies are needed to further evaluate H11 and H-gal-GP antigens under field conditions.