牛腹腔丝虫对3种伊蚊的感染试验

用牛腹腔指状丝虫和唇乳突丝虫的微丝蚴感染埃及伊蚊、白纹伊蚊和东乡伊蚊,观察了蚊虫的感染情况及牛腹腔丝虫Ⅲ期蚴的形态。结果,这两种丝虫的微丝蚴在3种伊蚊体内都能发育成熟,各蚊种的感染率不同,埃及伊蚊和白纹伊蚊分别为40%和30%以上,东乡伊蚊近70%;Ⅲ期蚴的表面结构不因蚊种而异。以不同蚊体内发育而成的Ⅲ期蚴感染小鼠,均可致小鼠出现与马、羊脑脊髓丝虫病相似的瘫痪或转圈运动等神经症状。由此认为,埃及伊蚊和白纹伊蚊也可能为脑脊髓丝虫病的传播媒介。     

小白鼠腹腔接种微丝蚴建立牛腹腔丝虫动物模型

建立了可代替病源牛的小鼠动物模型。给昆明小鼠腹腔接种分离自成牛腹腔丝虫子宫内的微丝蚴混悬液,所有试验鼠均出现了高密度的微丝蚴血症并持续一个月以上。叮咬模型小鼠的东乡伊蚊对牛腹腔丝虫易感。感染蚴经10—14天发育成熟。应用此新技术可为脑脊髓丝虫病研究提供大量感染蚴并有助于其它种动物丝虫的生活史的调查研究。     

江口县山羊脑脊髓丝虫病流行病学调查与防治措施

脑脊髓丝虫病是由寄生于牛腹腔的指形丝状线虫和唇乳突丝状线虫的晚期幼虫(童虫)引起的寄生虫病,羊、马多发[1],蚊是其中间宿主。指形丝状线虫或唇乳突丝状线虫所产生的幼虫(微丝蚴)随血液循环到达末梢血管,当蚊虫叮咬牛只后,微丝蚴即进入蚊体内,经两次平均14 d蜕化发育为感染期幼虫[2],再于蚊叮咬羊时传给羊,侵入羊脑脊髓腔内发育,破坏中枢神经组织。临床症状主要表现为腰髓所支配的后躯运动神经障碍,痿弱和共济失调,故通常称作“腰痿”或“腰麻痹”[3]。笔者对近年来山羊脑脊髓丝虫病在江口县的流行情况和防治措施做一总结,为今后山羊生产提供技术指导。     

牛腹腔丝虫感染蚴接种犊牛试验

牛腹腔丝虫感染蚴皮下接种非固有宿主马和羊,均发生脑脊髓丝虫病;接种沙鼠、小白鼠、大白鼠、豚鼠等实验小动物,亦均发生类似于马、羊脑脊髓丝虫病的临床症状及病理学变化。日本学者河野猪二郎曾报道在自然界中牛有脑脊髓丝虫病的病例。在马脑脊髓丝虫病发病机理研究中,我们以牛腹腔丝虫感染蚴接种固有宿主犊牛试验,企图通过人工造病,建立牛腹腔丝虫虫源模型。报告如下。     

牛腹腔丝虫微丝蚴人工感染蚊体研究

脑脊髓丝虫病在亚洲是危害马及山羊最严重的寄生虫病之一。已查明该病由牛腹腔丝虫的童虫所引起,中间宿主是按蚊;因而给按蚊人工接种病原体微丝蚴是研究本病的必要环节。以往国内外做此接种试验必须先检查牛血中含牛腹腔丝虫微丝蚴的密度,选择达到30条/60mm~3以上的牛供按蚊直接叮咬。但要找到血中微丝蚴含此高密度牛只往往要检查数十头甚至数百头;必须捆绑每一头受检牛,费时费力,经研究现可直接从牛腹腔丝虫子宫内取出微丝蚴感染蚊体。这样既不需捆牛,也不要特殊设备,蚊体吸吮血     

牛腹腔丝虫的调查

有关吉林、黑龙江、内蒙古三省的牛腹腔丝虫的种类及分布状况所知甚少。牛腹腔指状丝虫可经蚊虫传播引起羊、马脑脊髓丝虫病,唇乳突丝虫也可经人工感染使动物发生脑脊髓丝虫病。因此了解牛腹腔丝虫的     

山羊脑脊髓丝虫病的防治

青田县自1979年从陕西、山东、临海等地引进1000余头奶山羊。于80年7月至9月发生脑脊髓丝虫病,虽用海群生等药物治疗,但仍未免偏瘫而淘汰,死亡奶羊20多头。为此应重视本病的予防和治疗。马、羊脑脊髓丝虫病,是由牛腹腔指状丝虫或唇乳突丝虫的童虫经传播媒介,主要是中华按蚊、雷氏按蚊传播,侵入马、羊的脑脊髓而引起的一种丝虫病。脑脊髓丝虫引起的疾病,最早于本世纪初先发现于马的“腰痿病”,此后在不少国家相     

秦皇岛和唐山两地区黄牛腹腔丝虫的调查

前言关于中国牛腹腔丝虫，吴淑卿、夏逊等曾诈过调查，但河北省黄牛腹腔丝虫寄生情况目前尚未见报道。了解牛腹腔丝虫的分布规律，对进一步研究马、羊脑脊髓丝虫病的发生规律是非常重要的。本文报道了在对自然感染脑脊髓丝虫病的山羊进行免疫学诊断时，为了进一步证实其抗原性，在秦皇岛市昌黎县采集了黄牛腹腔内的丝虫并进行了鉴定。材料与方法从1992年至1995年在秦皇岛市昌黎县采集黄牛腹腔丝虫18O条（雌虫116条，推虫64条）．经用光学显微镜鉴定进行了分类和鉴定。调查结果经对所采集的180茶虫体经光镜下鉴定其结果为：唇乳突丝状线虫（…     

指状腹腔丝虫微丝蚴在中华按蚊体内发育过程中的形态学观察

<正> 指状腹腔丝虫的幼虫是马、羊脑脊髓丝虫病的主要病原,中华按蚊是其主要传播媒介。我们在对福建省马脑脊髓丝虫病病原终宿主及其传播媒介调查研究的基础上,1978年对指状腹腔丝虫微丝蚴及其在中华按蚊体内发育过程中的形态进行了观察,以期通过观察获得指状腹腔丝虫微丝蚴及其在中华按蚊体内发     

牛腹腔丝虫感染蚴接种犊牛试验

牛腹腔丝虫感染蚴皮下接种非固有宿主马和羊,均发生脑脊髓丝虫病,接种沙鼠、小白鼠、大白鼠、豚鼠等实验小动物,亦均发生类似于马、羊脑脊髓丝虫病的临床症状及病理学变化。     

Transmissible congenital demyelinating encephalopathy of lambs

Twenty-two fetal lambs were inoculated in utero with tissue suspension prepared from lambs born with weakness, incoordination and clonic tremor. Clinically, affected newborn lambs had clonic tremor, were generally weak and had abnormally pigmented hairy fleece. The inoculation resulted in a disseminated encephalomyelitis with secondary teratologic changes in a significant number of fetuses. The mononuclear inflammatory changes were most obvious 14 days after inoculation, after which there was rapid resolution. Changes seen at birth were chronic astrocytosis with neuron loss in the spinal cord and cerebellar dysplasia. Single radioimmunodiffusion studies showed consistently low IgG in infected fetuses and high IgG in lambs at birth.     

Comparative disposition kinetics and plasma protein binding of gentamicin sulphate in three juvenile animal species

The pharmacokinetics of gentamicin was studied in lambs, calves and foals, respectively after single intravenous (i.v.) injections of 5 mg kg(-1) body weight. The plasma concentration-time curves of gentamicin sulphate were best fitted to follow a two-compartment open model in calves and foals and a three-compartment open model in lambs. Gentamicin showed high plasma level at 5 min post-injection. Then its concentration decreased gradually until its minimum detectable level at 10 and 12 h post-injection in foals and calves, respectively, was reached. In contrast, the plasma concentrations were much higher in lambs and persisted up to 48 h from the onset of injection. Values of pharmacokinetic parameters for gentamicin sulphate in different animals after i.v. injections were calculated. Pharmacokinetic data in lambs demonstrated a triphasic decline in plasma gentamicin concentration with slow terminal elimination phase (washout phase) with (t(1/2y)) of 7.7 h. Gentamicin showed a small volume of distribution Vd(ss) (80.3 ml kg(-1)) in lambs indicating that the drug is slightly distributed in extra-vascular tissues. The overall rate of total body clearance ClB in lambs was (0.46 ml kg(-1)) slower than in calves (1.5 ml kg(-1)) and foals (2.7 ml kg(-1)). In vitro protein binding per cent of gentamicin sulphate in plasma were 16.80, 11.03 and 7.98% in lambs, calves and foals. The results of this study emphasize the importance of determining the pharmacokinetics of gentamicin in each species of young animals separately.     

Encephalomalacia with Enterococcus durans infection in the brain stem and cerebral hemisphere in chicks in Japan

Fourteen chicks, 7-12 days old, that died or had neurological signs (depression, paralysis, torticollis, incoordination, and rolling) were investigated pathologically and microbiologically. Variably sized foci of malacia were present within the parenchyma of the brain stem (cerebral peduncle, optic lobe, and medulla oblongata) and the cerebral hemisphere. Capillary thrombosis with congestion and hemorrhage was frequently observed within the malacia lesions. Gram-positive cocci were recognized in the blood capillary of malacia lesions. Bacteriologically, Enterococcus durans was isolated from the brain, liver, kidney, lung, and spleen. Detection of gram-positive cocci within the blood vessels in the malacia lesions observed in these cases may more strongly suggest the pathogenic role of E. durans on the malacia lesions in the brain stem and cerebral hemisphere.     

Effects of repeated Strongylus vulgaris inoculations and concurrent ivermectin treatments on mesenteric arterial lesions in pony foals

Eight of 10 pony foals reared under helminth-free conditions were inoculated PO with 50 Strongylus vulgaris infective larvae/week for 4 weeks, at which time 1 foal died of acute verminous arteritis. Inoculation of 7 remaining foals continued at 2-week intervals for 20 weeks. Of the 7 foals, 3 were treated with ivermectin (0.2 mg/kg of body weight) in an oral paste formulation at experiment weeks 8, 16, 24; 4 foals were not treated. Two foals were not inoculated or treated and served as controls. After the first ivermectin treatment, ivermectin-treated foals had fewer days (12 +/- 2.9) with rectal temperatures greater than 38.6 C than did nontreated foals (23.3 +/- 3.8). Mean baseline rectal temperatures were 38 +/- 0.2 C. Adverse clinical reactions to ivermectin treatment were not observed in foals. Foals were euthanatized and necropsied 3 weeks after the last ivermectin treatment (week 24). Ivermectin was effective in reducing S vulgaris arterial larval and intestinal adult parasite numbers by 100% in 3 treated foals. Strongylus vulgaris arterial larvae and/or adults were recovered from all 4 nontreated inoculated foals. One nontreated inoculated foal lacked arterial larvae or active arterial lesions, indicating that protective resistance had developed in this individual. Marked gross and histopathologic lesions typical of chronic S vulgaris infection were observed in the 3 nontreated inoculated foals with arterial larvae. Repeated killing of intra-arterial S vulgaris fourth-stage larvae in ivermectin-treated foals did not exacerbate lesions associated with verminous arteritis or induce unique lesions associated with repeated destruction of arterial larvae.(ABSTRACT TRUNCATED AT 250 WORDS)     

Observations on transplacental infection with bluetongue virus in sheep

Twenty-four ewes were inoculated with 1 of 2 strains of bluetongue virus type 4 at 40, 60, or 80 days of gestation. Two ewes aborted, 2 ewes died, and 1 was killed during the experiment, but their fetuses were recovered. At term, 2 mummified fetuses, 4 dead lambs, and 17 clinically healthy lambs were produced by 12 sheep, and the remaining 7 sheep were barren. Porencephaly and cerebellar dysgenesis were found in term lambs born to sheep inoculated at 40 and 60 days of gestation. Radiographic examination of 12 fetuses showed developmental ages far less than their chronologic age; 8 fetuses had skeletal growth-retardation lines, which were also observed in the dead lambs. A systemic lymphoreticular hyperplasia was observed in the dead lambs and in all lambs at 12 weeks of age; in 4 of the latter, granulomatous reactions were present in the liver and kidney. Lungs of the full-term lambs were reduced in weight and showed poor alveolar development and mononuclear cell infiltration, which persisted in the 12-week-old lambs. It was concluded that bluetongue virus is capable of causing not only gross abnormalities of the CNS, but also generalized growth retardation and fetal lymphoreticular hyperplasia.     

Experimental infection of sheep with bovine herpesvirus type-5 (BHV-5): acute and latent infection

We demonstrated that sheep are susceptible to acute and latent infection by bovine herpesvirus type-5 (BHV-5). Lambs inoculated intranasally with two South American BHV-5 isolates replicated the virus with titers up to 10(7.1) TCID50/ml for up to 15 days and showed mild signs of rhinitis. Four lambs in contact with the inoculated animals acquired the infection and excreted virus for up to seven days. One lamb developed progressive signs of neurological disease and was euthanized in extremis. Clinical signs consisted of tremors of the face, bruxism, ptyalism, incoordination, lateral flexion of the neck and head, circling, walking backwards, recumbency and paddling. The virus was detected in the anterior and posterior cerebrum, dorso- and ventro-lateral cortex, cerebellum, pons, midbrain and olfactory bulb. Viral nucleic acids were demonstrated in neurons and astrocytes of the anterior and ventro-lateral cortex by in situ hybridization. Histological changes consisting of non-suppurative meningitis, perivascular mononuclear cuffing, focal gliosis, neuronal necrosis and intranuclear inclusions were observed in the anterior cerebrum, ventro-lateral cortex and midbrain. Dexamethasone treatment at Day 50 pi resulted in reactivation of the latent infection and virus shedding in 13/16 (81%) of the lambs. Together with previous reports of BHV-5 antibodies in sheep, these findings show that sheep are fully susceptible to BHV-5 suggesting that infection by BHV-5 in sheep may occur naturally.     

ENTERITIS IN FOALS INDUCED BY ROTAVIRUS AND ENTEROTOXIGENIC ESCHERICHIA COLI

Colostrum-deprived, colostrum-fed or suckling foals were orally inoculated with foal rotavirus and enterotoxigenic Escherichia coli derived from a calf. Neither agent given alone caused diarrhoea in foals aged 1 or 2 days, although with rotavirus, 2 of the 3 inoculated foals became depressed 3 days after inoculation and all 3 were excreting rotavirus in the faeces. Inoculation of both agents induced diarrhoea in colostrum-deprived, colostrum-fed or suckling foals aged up to 16 days. There was an apparent age-related resistance to diarrhoea which developed between 2 and 3 weeks of age. It was related to failure of rotavirus to establish apparent infection in older foals and was independent of preinoculation maternal antibody.     

Development of a live, attenuated, potential vaccine strain of R. equi expressing vapA and the virR operon, and virulence assessment in the mouse

Pneumonia caused by Rhodococcus equi remains a significant problem in foals. The objective of this study was to develop a safe and efficacious attenuated strain of R. equi for eventual use in oral immunization of foals. The approach involved expression of vapA in a live, virulence plasmid-negative, strain of R. equi (strain 103-). PCR-amplified fragments of the vapA gene, with and without the upstream genes virR, orf5, vapH, orf7 and orf8 (orf4-8), were cloned into a shuttle vector pNBV1. These plasmids, named pAW48A and pAWVapA respectively, were electroporated into strain 103-. The presence of the recombinant vectors in the attenuated strain (103-) and the integrity of the inserted genes were confirmed, and both constructs expressed VapA. The virulence of the two strains was compared to that of wild type R. equi 103+ and negative controls by their intravenous inoculation into mice, followed by examination of liver clearance 4 days later. Mice inoculated with R. equi 103-, 103-/pAWVapA and 103-/pNBV1 completely cleared infection, whereas strain 103-/pAW48A persisted in 47% of mice.     

Pathogenesis of bovine respiratory syncytial virus in experimentally infected lambs

Twenty-four 6-8-week-old conventionally reared lambs were inoculated intranasally and intratracheally with bovine respiratory syncytial virus. Infected lambs showed mild clinical signs characterized by slight serous nasal discharge, coughing, lachrymation and bronchovascular sounds on the middle part of the lung 5-9 days post-inoculation (PI). Virus was isolated in nasal swabs from 9 of 24 lambs between 3 and 7 days PI. However, virus was recovered from tracheal and lung tissue of all lambs killed between 3 and 11 days PI. Virus-specific antibodies appeared as early 6 days PI but high titres were attained 14-21 days PI. Lungs of lambs killed on different days PI had multifocal areas of consolidation. There was an increase of lymphocytes with a T-suppressor cell marker and a decrease in those with a T-helper marker in lung lavages obtained 5 days PI.