鸡马立克病毒流行强毒株的致弱研究

针对马立克病毒(MDV)毒力逐渐上升的现状,本研究对国内MDV流行强毒株进行了致弱研究。本实验采用近年来从东北、四川2地区免疫发病鸡场中分离的4株MDV流行强毒株(L-SY、L-MS、L-CZ、L-ZY),经噬斑纯化后,采用鸡胚成纤维细胞(CEF)传代培养至75代～85代,获得了4株高代次细胞毒株(L-SYp85C、L-MSp75C、L-CZp75C、L-ZYp75C)。并分析了L-SYp85C和L-MSp75C毒株的体外、体内生长特性和对SPF鸡的致病力。结果表明,L-SYp85C和L-MSp75C株在CEF适应性显著提高;以10倍感染剂量感染的SPF鸡,在12周内均未发生MD肿瘤,体重平均值与对照组体重平均值差异不显著;检测7d～45d羽髓中病毒载量,均低于106copies/106cell,显著低于亲本毒株。同时,4株传代毒株132bpr基因拷贝数显著增加。上述结果为MDV强毒株的致弱研究以及进一步筛选MDV弱毒疫苗株提供了实验依据。     

鸡马立克氏病的流行与免疫

鸡马立克氏病（MD）是由鸡马立克氏病病毒引起的鸡淋巴细胞增生性肿瘤疾病。其特点是在鸡外周神经、性腺、虹膜、各种脏器、肌肉和皮肤出现淋巴样细胞、单核细胞的浸润和增生及肿瘤的形成。鸡马立克氏病病毒（MDV）归属于疱疹病毒科。MDV在流行过程中经常出现变异毒株，其共同特点是毒力比一般毒株强，有极强的肿瘤性，用HVT免疫的鸡不能阻止其致瘤性。MDV分3个型，Ⅰ型为致病性强毒株及其致弱毒株，Ⅱ型为无致病性的自然弱毒株，Ⅲ型为火鸡疱疹病毒（HVT），此型病毒本非MDV，但因与鸡马立克氏病关系密切，故将其划分在马立克氏病毒型内。     

马立克氏病病毒“814”疫苗株基因组重复区序列测定及分析

为了解马立克氏病病毒(MDV)强、弱毒株主要致肿瘤相关基因变异情况,本研究根据MDV GA株基因组序列,设计合成扩增基因组重复区的引物,得到MDV814疫苗株病毒基因组中约26kb的序列片段。与GenBank登录的强、弱毒株进行比较分析表明,扩增的MDV1型814疫苗株的长重复区为12774bp,预测的开放阅读框(ORF)有48个;短重复区为11426bp,预测的ORF有38个。发现了4个MDV814株特有的ORF。814株在编码Meq、RLORF6和23ku的重叠基因内具有类似于疫苗株CVI988的177bp的插入;在RLORF12基因编码区内存在69bp的缺失,该缺失位于病毒复制起始位点内。同时,发现7个814疫苗株特有的氨基酸突变,分布在6个ORF内。单核苷酸多态性(SNP)的鉴定发现,多个基因具有单核苷酸的突变,主要分布于Meq基因,其中氨基酸A115V(丙氨酸-缬氨酸),N142D(天冬酰胺-天门冬氨酸)的变异是814疫苗株所特有的。MDV814疫苗株重复区的基因序列的比较分析将有助于MDV致肿瘤机制的研究。     

缺失部分miRNA的重组马立克氏病病毒致病性研究

马立克氏病(MD)是由马立克氏病病毒(MDV)引起的T淋巴细胞增生性疾病.为了研究MDV编码的miRNA与致瘤性的关系,通过对缺失部分miRNA的MDV-MS毒株进行动物感染试验,并将其结果与MDV-MS强毒株的致病性的试验结果进行比较.结果表明:缺失miRNA的重组MDV对无特定病原体(SPF)鸡无致病性,而接种MDV-MS毒株的SPF鸡却显示出很强的MD典型症状.此结果证实MD V编码的miRNA对MDV的致瘤性起到重要的作用.另外,通过对重组MDV感染鸡的羽髓病毒载量的动态检测,发现此处编码MDV-miRNA的基因为复制非必须区,但重组病毒rMS△miR9-12比亲本病毒MDV-MS的体内复制能力有所下降.     

企业

正大华农取得一项疫苗发明专利证书广东大华农动物保健品股份有限公司8月21日发布公告称,公司近日收到国家知识产权局颁发的一项发明专利证书,发明名称为"一株马立克氏病病毒疫苗株及其分离鉴定和应用"。大华农称,该发明在健康鸡场中分离到一株鸡马立克氏病病毒(MDV),命名为CVTR株。MDV CVTR株不会诱发鸡的肿瘤,对鸡群也没有免疫抑制作用。CVTR株病毒在鸡胚成纤维细胞(CEF)上或鸡体内比目前广泛使用的CVI988/Rispens疫苗株增殖更迅速。将CVTR株用作马立克氏病活疫苗的生产毒株所制备的疫苗,预防超强毒MDV诱发的鸡马立克氏病,其保护力优于目前国内外市场上应用     

鸡马立克氏病毒超强毒及其防制措施

马立克氏病（Marek’sDisea。，MD）是一种由B群疤疹病毒引起鸡的最常见的淋巴组织增生性疾病，以外周神经和其它组织的单核性细胞浸润为特征。本病传染性强，造成的经济损失十分巨大。所以，一直是国内外最受重视的禽病之一。马立克氏病病原为马上克氏病毒（MDV），根据MDV毒株抗原差异及其生物学特性，将MDV及其抗原相关病毒分成三个血清型、血清1型包括所有强毒及其致弱毒，血清11型为天然不致瘤病毒，血清巨型为火鸡技疹病毒。其中血清I型MDV，根据其致病性又可分成四个亚型（Schat，1982），即超强毒株d强毒株，毒力温和株及强…     

鸡马立克氏病血清型

正所有的马立克氏病毒分离株可根据生物特性分为三个不同的血清型:1)血清1型:包括所有的致病性或致瘤性MDV及相应的致弱株。根据血清I型MDV诱发免疫鸡群MD病变的能力可将血清1型之MDV进一步分为:温和马立克氏病病毒(m MDV),强毒马立克氏病病毒(VMDV),超强马立克氏病病毒(VVMDV),超超强马立克氏病病毒     

一株鸡马立克氏病毒的分离鉴定及其主要致病基因分析

吉林省某地区鸡马立克氏病（MD）疫苗免疫鸡群暴发MD,从发病鸡羽髓中分离到一株适应鸡胚成纤维细胞生长的马立克氏病毒（MDV）。该毒株感染无特定病原体（SPF）鸡可引起典型的MD临床症状：对非免疫鸡和火鸡疱疹病毒（HVT）疫苗免疫鸡的致病率分别为76％和72％,二者无显著差异,表明HVT疫苗对该毒株不能提供有效保护。通过对该毒株病毒基因组中132bp重复序列、meq基因的核苷酸及推导的氨基酸序列分析,发现该毒株的132bp重复序列的拷贝数、meq基因的变异符合高毒力MDV毒株的特点。     

马立克氏病病毒肿瘤Meq基因缺失株的保护性免疫作用

马立克氏病病毒（MDV）的致病性一直在不断增强中,甚至已出现了能抵抗CV1988/Rispens疫苗的特超强株。本实验室用BAC克隆技术构建了MDV中国野毒株的Meq基因缺失株,显示出在抗马立克氏病方面具有与美国Meq基因缺失株同样有效的保护性免疫效果,而且其自身没有明显的免疫抑制作用。对美国和中国的两个MDV的Meg基因缺失株的优缺点做了比较。     

马立克氏病病毒Meq基因缺失株的保护性免疫作用

马立克氏病病毒(MDV)的致病性一直在不断增强中,甚至已出现了能抵抗CV1988/Rispens疫苗的特超强株。本实验室用BAC克隆技术构建了MDV中国野毒株的Meq基因缺失株,显示出在抗马立克氏病方面具有与美国Meq基因缺失株同样有效的保护性免疫效果,而且其自身没有明显的免疫抑制作用。对美国和中国的两个MDV的Meg基因缺失株的优缺点做了比较。     

Phase I evaluation of CCNU (lomustine) in tumor-bearing cats

1-(2-Chloroethyl)3-cyclohexyl-1-nitrosourea (CCNU) is an alkylating agent in the nitrosourea subclass. A prospective evaluation of CCNU was done to determine the maximally tolerated dosage of CCNU in tumor-bearing cats. Response data were obtained when available. Twenty-five cats were treated with CCNU at a dosage of 50-60 mg/m3 body surface area. Complete hematologic data were available for 13 cats. Neutropenia was the acute dose-limiting toxicity. The median neutrophil count at the nadir was 1,000 cells/microL (mean, 2,433 cells/microL; range, 0-9,694 cells/microL). The time of neutrophil nadir was variable, occurring 7-28 days after treatment, and counts sometimes did not return to normal for up to 14 days after the nadir. Based on these findings, a 6-week dosing interval and weekly hematologic monitoring after the 1st treatment with CCNU are recommended. The nadir of the platelet count may occur 14-21 days after treatment. The median platelet count at the nadir was 43,500 cells/microL. No gastrointestinal, renal, or hepatic toxicities were observed after a single CCNU treatment, and additional studies to evaluate the potential for cumulative toxicity should be performed. Five cats with lymphoma and 1 cat with mast cell tumor had measurable responses to CCNU. Phase II studies to evaluate antitumor activity should be completed with a dosing regimen of 50-60 mg/m3 every 6 weeks.     

Furosemide continuous rate infusion in the horse: evaluation of enhanced efficacy and reduced side effects

Continuous rate infusion (CRI) of furosemide in humans is considered superior to intermittent administration (IA). This study examined whether furosemide CRI, compared with IA, would increase diuretic efficacy with decreased fluid and electrolyte fluctuations and activation of the renin-angiotensin-aldosterone system (RAAS) in the horse. Five mares were used in a crossover-design study. During a 24-hour period, each horse received a total of 3 mg/kg furosemide by either CRI (0.12 mg/kg/h preceded by a loading dose of 0.12 mg/kg IV) or IA (1 mg/kg IV q8h). There was not a statistically significant difference in urine volume over 24 hours between methods; however, urine volume was significantly greater after CRI compared with IA during the first 8 hours ([median 25th percentile, 75th percentile]: 9.6 L [8.9, 14.4] for CRI versus 5.9 L [5.3, 6.0] for IA). CRI produced a more uniform urine flow, decreased fluctuations in plasma volume, and suppressed renal concentrating ability throughout the infusion period. Potassium, Ca, and Cl excretion was greater during CRI than IA (1,133 mmol [1.110, 1,229] versus 764 mmol [709, 904], 102.7 mmol [96.0, 117.2] versus 73.3 mmol [65.0, 73.5], and 1,776 mmol [1,657, 2.378] versus 1,596 mmol [1,457, 1,767], respectively). Elimination half-lives of furosemide were 1.35 and 0.47 hours for CRI and IA, respectively. The area under the excretion rate curve was 1,285.7 and 184.2 mL x mg/mL for CRI and IA, respectively. Furosemide CRI (0.12 mg/kg/h) for 8 hours, preceded by a loading dose (0.12 mg/kg), is recommended when profound diuresis is needed acutely in horses.     

Prevalence of gastric lesions in racing Alaskan sled dogs

Human and equine athletes are reported to have a high prevalence of gastric disease, and anecdotal evidence suggests a similar phenomenon applies to racing sled dogs. To investigate the prevalence of gastric disease in racing sled dogs, we conducted 2 gastroscopy studies on dogs competing in the annual Iditarod Sled Dog Race. A pilot study of dogs that were either dropped from the 2000 Iditarod Sled Dog Race because of illness or that finished the race indicated that, approximately 5 days after competing, 10 of 28 dogs (35%) had endoscopic evidence of gastric ulceration, erosion, or hemorrhage. The next year, an endoscopic study of 73 dogs participating in the 2001 Iditarod race was performed in order to evaluate a larger population of dogs. Data from 70 of these dogs could be used; 34 (48.5%) had ulceration, erosion, gastric hemorrhage, or some combination of these findings. When this group of 70 dogs was compared retrospectively to a control group of 87 dogs presented to the Texas A&M University (TAMU) Veterinary Medical Teaching Hospital, the Iditarod sled dogs had a significantly higher prevalence (P = .049) of gastric lesions. These findings suggest that, similar to athletes of other species, elite canine athletes have an increased prevalence of gastric disease compared to the canine population at large.     

Internal Parasites and Haematological Values in Cattle Slaughtered in Buea Subdivision of Cameroon

Tropical Animal Health and Production -     

The Epidemiology of Gastrointestinal Nematodes of Dairy Cattle in Central Kenya

The epidemiology of H. placei and of other gastrointestinal nematodes in yearling dairy cattle was examined on two farms in Kiambu District, central Kenya during each of 13 one-month periods from April 1993 to April 1994. On each farm, 32 newly weaned dairy calves were given a single dose of albendazole and then placed on experimental pastures. Twelve of the animals were designated for bi-monthly slaughter (n = 2) and analysis of worm population characteristics and 20 were designated for blood and faecal collection and for weighing. Two parasite-free tracer calves were grazed alongside the weaner calves each month throughout the study period and were also slaughtered for analysis of worm populations. Faecal egg counts, haematological and serum pepsinogen determinations, herbage larval counts, and animal live weight changes were recorded monthly. The study revealed that Haemonchus placei, Trichostrongylus axei, Cooperia spp. and Oesophagostomum radiatum were responsible for parasitic gastroenteritis and that H. placei was the predominant nematode present in the young cattle on both farms. Faecal egg counts from resident cattle and necropsy worm counts revealed that pasture larval levels were directly related to the amount of rainfall. The total worm burdens in the animals were highest during the rainy season (March–June and October–December) and lowest during the dry seasons (July–September and January–February). The very low recovery of immature larvae of H. placei from the tracer calves indicated that arrested development is not a feature of the life cycle of this parasite in central Kenya. The maintenance of the parasite population depended on continuous cycling of infection between the host and the pasture. The agroclimatic conditions of the study area were such that, in general, favourable weather conditions for the development and survival of the free-living stages of gastrointestinal nematodes existed all year round.     

Diversity of Ectoparasites in Sheep Flocks in Sa~o Paulo,Brazil

The occurrence of ectoparasites in sheep flocks is frequently reported but seldom quantified. Sheep production used to be a predominantly family activity in the state of Sa~o Paulo (Brazil), but it began to become a commercial activity in the past decade. Thus, information about the ectoparasites existing in sheep flocks has become necessary. The present data were obtained by means of questionnaires sent to all sheep breeders belonging to the `Associaça~o Paulista de Criadores de Ovinos' (ASPACO; Sa~o Paulo State Association of Sheep Breeders). Response reliability was tested by means of random visits paid to 10.6% of the respondents. Most of the properties (89.5%) reported the presence of one or more ectoparasites. Screw-worm (Cochliomyia hominivorax) was the most frequent ectoparasite (72.5%), followed by bot fly larvae (Dermatobia hominis, 45.0%), ticks (Amblyomma cajennense) and Boophilus microplus, 31.3%) and finally lice (Damalinia ovis, 13.8%). Combined infestations also occurred, the most common one being screw-worm with bot fly larvae (36.0%) followed by bot fly larvae with ticks (13.9%), screw-worm with ticks (9.3%), bot fly larvae with lice (6.9%), and ticks with lice (5.0%). The most common triple combination was screw-worm, bot fly larvae and ticks (12.8%). Breeds raised for meat or wool were attacked by bot fly larvae and ticks more often than other breeds. Lice were only absent from animals of indigenous breeds. The relationships among these ectoparasites are discussed in terms of sheep breeds, flock size, seasonality and the ectoparasitic combinations on the host.     

Chemotaxis of macrophage in inflammation

Our particular attention in this article was given to natural mediators for macrophages isolated from the sites of tissue injury. A number of chemotactic factors, which may satisfy many criteria making them acceptable as inflammatory leucocyte chemotactic factors, has been separated. Among them, our laboratory has isolated three macrophage (monocyte) chemotactic factors (MCF-a, -b and -c). Their purification, characterization and functional specificity are discussed.     

Evaluation of biohydrogenation rate of canola vs. soya bean seeds as unsaturated fatty acids sources for ruminants in situ

An experiment was conducted to study disappearance of C14 to C18 fatty acids, lag times and biohydrogenation (BH) rates of C18 fatty acids of ground soya bean and canola seeds in situ. Three ruminally fistulated Dallagh sheep were used to determine ruminal BH of unsaturated fatty acids (UFAs). Differences in the disappearance of fatty acids through the bags and lag times were observed between the oilseeds. We saw that the longer the incubation time of the oilseeds in the rumen, the lower the content of C18:2 and C18:3. Significantly higher lag times for both C18:2 and C18:3 were observed in ground canola compared to ground soya bean. BH rates of C18:2 and C18:3 fatty acids in soya bean were three times higher than those of canola. These results suggest that the fatty acid profile of fat source can affect the BH of UFAs by rumen micro‐organisms. So that UFAs of canola had higher ability to escape from ruminal BH. It seems that fatty acid profile of ruminant products is more affected by canola seed compared to soya bean seed.     

Serum biochemical values and mineral element contents of tissues in yaks

Serum biochemical values and the wet weight to dry weight ratios of tissues were determined in yaks in Shandan county of Gansu province. The liver, kidney, heart and muscle contents of seven elements in yaks were also analysed. Most serum biochemical values were similar to those of cattle, camels and sheep, but the calcium concentration was considerably above the normal range for other ruminants. The liver contained the highest concentrations of copper, manganese and cobalt and the kidney of selenium, iron and calcium.Abbreviations Alb albumin - ALT alanine aminotransferase - AST aspartate aminotransferase - BUN blood urea nitrogen - Chol cholesterol - Glob globulin - -GT -glutamyl transpeptidase - IP inorganic phosphorus - TP total protein