An oculo-cerebellar syndrome caused by congenital bovine viral diarrhoea virus-infection

An epizootic characterized by birth of calves severly ataxic and blind were encountered in 3 herds 7–8 months after outbreaks of bovine virus diarrhoea. Serological and virological investigations indicated introduction of bovine viral diarrhoea virus (BVDV) into previously virus-free herds, followed by transplacental virus infection of the fetuses of cows in the first trimester. Clinical, pathological, serological, and microbiological examinations were performed on 10 calves. Pathological findings included microcephaly and cerebellar hypoplasia, ocular malformations, and thymic hypoplasia. BVDV was isolated from tissue and blood of 7 calves, and 4 calves, 1 of which had not received colostrum, had virus-specific neutralizing antibodies.This is the first report on natural occurrence of congenital bovine infection with BVDV among Danish cattle herds resulting in abortion and birth of calves with severe debilitating congenital anomalies. It draws attention to the importance of this virus for bovines of all age groups.     

松树枯梢病潜伏侵染的研究

研究表明在火炬松、湿地松、短叶松和马尾松健康梢上整年都能分离到松枯梢病菌,其中在火炬松上的得菌率为15％—37．7％,且大多数月份高于20％;湿地松上的得菌率稍低于火炬松,为7．5％～29．1％;短叶松梢上的得菌率是13．8％—57．1％,月份之间的差异较大;马尾松得菌率最低,为9．7％—22．4％,多数分离得菌率低于20％。健康梢的不同部位得菌率有一定差异,枝和新梢较高,芽稍低,叶最低。在1年中,健康梢上得菌率有3个高峰期,即4—5月、7—8月和10—11月,是潜伏侵染的的主要时期。将健康芽和梢进行诱发培养,lOd后组织块上及周围产生松枯梢病菌的分生孢子器,得菌情况与常规分离相似。在当年孢子散发之前,对健康梢套袋隔离试验,发现套袋梢仍会发病,说明在发病的春梢中,有一部分是由于潜伏侵染的松枯梢病菌造成的。从而证明松枯梢病菌在火炬松、湿地松、短叶松和马尾松上普遍存在潜伏侵染。     

Resistance to early blight of tomato with respect to various parameters of disease epidemics

Resistance to early blight in the tomato was assessed by examining various parameters of the progress of the disease. Artificial inoculation and the scoring technique were standardized. Test plants were inoculated with 125cfu/ml of a 12-day-old culture of a pathogenic isolate of Alternaria solani. Screening under artificial conditions was more informative than that under natural epidemic conditions. Tomato cultivars CLN-2071-C, CLN-2070-A, BSS-174, and DTH-7 with resistance expressed as slow blighting against four pathogenic isolates of A. solani, were selected for cultivation in disease-prone areas. Disease intensity increased with the age of plants under the same inoculum load. The area under the disease progress curve (AUDPC) was positively correlated with the percentage disease index and negatively with resistance. Calculation of the apparent infection rate (r) was more informative for natural epidemics than for artificial conditions. The sequential apparent infection rate between observation periods was better correlated with disease progress than was the total apparent infection rate between the first and last observations. A double sigmoidal disease progress curve during the same cropping season was characteristic of some varieties when fungal infection took place during the vegetative phase of crop growth.     

Detection of Brucella species in the milk of infected cattle,sheep, goats and camels by PCR

One hundred and three milk samples were collected from 52 cows, 21 ewes, 18 goats and 12 camels. The animals tested positive to at least one of the following: (1) standard tube agglutination test (SAT); (2) Rose Bengal plate test (RBPT); (3) milk ring test (MRT). All milk samples were examined by culture and single-step polymerase chain reaction (PCR) techniques for detection of Brucella species. The PCR assay amplified Brucella-DNA from 29 bovine milk samples, 10 from sheep, 13 from goats and one from a camel. The direct culture method detected Brucella organisms from 24 samples of cows' milk, 12 from sheep, 10 from goats and failed to detect any Brucella organisms from camels' milk. PCR detected up to 100 colony forming units (CFU) of B. abortus per millilitre of milk in 100% of diluted milk samples, and 1000 CFU of B. melitensis from 70% of milk samples. Although the overall sensitivity of the PCR was higher than the culture method, it should be possible to increase the sensitivity to detect lower numbers of Brucella organisms in field samples. The speed and sensitivity of the PCR assay suggest that this technique could be useful for detection of Brucella organisms in bovine milk, as well as in sheep, goat, and camels milk.     

Life cycle of Eimeria procera in experimentally infected grey partridges (Perdix perdix)

We examined exogenous and endogenous development of Eimeria procera in experimentally infected grey partridges (Perdix perdix). Our examination included data on morphology, localization, duration of schizogony and gametogony and morphology of sporulated oocysts. The endogenous stages of E. procera developed in large numbers within the epithelial cells of caecal crypts. The asexual development comprised three generations of schizonts. The first fully developed macrogametes and microgamonts were observed on Day 5 post-infection (p.i.) in histologic section. The patent period began on Day 6 p.i. and ended on Day 11 p.i. with peak production of oocysts on Days 7 and 8. Long oval oocysts of E. procera measured 25.78–28.13 μm in length and 14.06–15.24 μm in width, sporulation time ranged from 18 to 24 h at 25°C and from 36 to 48 h at 20°C.     

Forecasting Infections of the Leaf Curl Disease on Peaches Caused by Taphrina deformans

An Israeli model forecasting leaf curl disease on peaches caused by Taphrina deformans was validated in the Emilia-Romagna region of northern Italy, during a three-year period (1996–1998), in 13 cases (year × location × cultivar). When the peach trees are susceptible to infection, the model uses mathematical functions to calculate the risk of infection on the basis of weather conditions (daily rainfall greater than 10mm, and maximum air temperature greater than 5°C), and it forecasts periods of possible symptom appearance based on the length of incubation. Peach trees became susceptible to infection between the end of January and mid March, when the first leaf buds attained phenological stage C, i.e. appearance of leaf apex. The trees remained susceptible for at least 9 weeks: the last infection occurred in mid-May.Since most of the leaf curl onsets observed in the orchards fell within the range of model forecasts, the model proved to be accurate in signalling both the first seasonal infection and repeated infections during the primary inoculum season. Few errors occurred, caused either by conditions of rainfall and temperature lower than the thresholds fixed in the model, or by discrepancies between forecast and actual length of incubation. Infection occurred also at 3.1–3.5°C, and with 9.6mm rainfall. Thus, thresholds should not be accepted too rigorously, and perhaps temperature should not be considered as a limiting factor for infection under the conditions of the present work. The length of incubation showed high variability: it was 23 days long on average, with a 95% confidence interval ranging from 20 to 27 days, and extreme values of 9 and 33 days.     

蛋白粒子的全新传染机制

蛋白粒子主要引起人和动物的中枢神经系统退行性疾病,称之为蛋白粒子病。许多研究表明蛋白粒子病的致病因子缺乏棱酸,而是由特异的传染性蛋白质组成。该蛋白粒子是一种膜糖蛋白,至少有两种基本形式,即PrP~c和PrP~(ac)。PrP~(ac)是发病的直接原因,而PrP~c向PrP~(ac)转变则是发病的必要条件。文章就蛋白粒子概念、分子生物学以及全新的传染机制作了综合论述。     

口蹄疫病毒整联蛋白受体的研究进展

从组织分布、各毒株利用率、配体结合区介导感染的能力及β亚基胞质区作用等方面论述了4种整联蛋白αvβ1、αvβ3、αvβ6和αvβ8的研究进展，旨在阐明各整联蛋白决定口蹄疫病毒宿主组织嗜性的作用，并为口蹄疫病毒致病机制的研究提供理论依据。     

禽呼肠孤病毒鸡源分离株的鉴定与人工感染试验

从临床患病鸡关节病料中分离到一株病毒，在电镜下观察到病毒粒子无囊膜，有双层衣壳，外衣壳直径约75nm，内核约50nm；分离病毒株对酸、热有较强的抵抗力，对乙醚不敏感；病毒感染鸡胚成纤维细胞上能产生以融合细胞为特征的CPE；爪垫接种1日龄雏鸡表现出明显的病毒性关节炎临床症状，并伴有吸收障碍型和坏死型的病理变化；血清中和交叉试验表明，该病毒分离株与国内的2株番鸭源呼肠孤病毒（YH和YB）分离株和国外S1133呈不同程度的交叉反应。通过对分离病毒株进行电镜观察、理化特性试验、病毒感染力测定、致病性试验、血清学试验，可以确定该分离病毒为禽呼肠孤病毒。     

产单核细胞李氏杆菌突变株的感染动力学研究

以BALB/c小鼠为实验动物模型,对actA基因和plcB基因双缺失的产单核细胞李氏杆菌（LM）yzuLM1-2菌株进行感染动力学研究。分别用减毒突变株yzuLM1-2和野生型菌株yzuLM4给BALB/c小鼠静脉注射或灌服,并对脏器中LM的分布动态进行测定。结果显示,在显著高于野生型菌株感染剂量的条件下注射或灌服接种后,减毒突变株组小鼠肝和脾中的LM数量迅速下降,被清除的速度显著快于野生型菌株组。溶血素（LLO）抗体的测定结果显示,减毒突变株菌能和野生型菌同样激发较高水平的抗体。小鼠免疫保护试验结果显示,减毒突变株免疫组对同种血清型LM的攻击具有较好的免疫保护力,可达100%。结果表明,yzuLM1-2突变株侵袭力下降,致病力降低,能激发较高水平的抗体产生,可以作为预防动物李氏杆菌病的候选疫苗菌株,并为用作运送外源保护性抗原的载体提供了材料。