禽脑脊髓炎研究进展

禽脑脊髓炎(AvianEncephalomyelitis,AE)是由细小RNA病毒科(Picornaviridae)、肠病毒属(Enterovirus)的禽脑脊髓炎病毒(AEvirus,AEV)引起的,以主侵幼鸡中枢神经系统引起非化脓性脑炎为主要病理特征的一种病毒性传染病。本病呈世界性分布,对养鸡业特别是种鸡饲养业造成了极大危害。自1991年内蒙古农业大学分离并建立了AEV-NH937株,系统描述了自然病例和人工感染的成年鸡、雏鸡、鸡胚的病理变化,人工感染后AEV在鸡体内的动态分布,并制备出琼扩抗原和灭活油乳剂疫苗用于临床检测和预防,取得了重要研究成果。分子免疫学研究证明:在抗AEV-NH937株感染中体液免疫发挥重要作用,而在脑组织以CD8 T淋巴细胞(CTL,细胞毒性T细胞)对病毒感染细胞进行细胞毒作用;各淋巴组织的淋巴细胞表面粘附分子在围管性浸润形成期间表达显著或不显著;淋巴细胞和脑组织细胞在病情严重时均凋亡显著;IL-8和MIP-1β趋化因子的变化与围管性浸润的形成同步。     

鸽I型副粘病毒病的研究进展

本文就鸽Ⅰ型副粘病毒病的国内外发生历史、流行特点、病原特性、临床症状、病理变化以及免疫防治等方面的研究进展进行了综合整理，以期对该病的深入研究和防制工作起推动作用。     

Pathogenicity and genetic variation of Phytophthora cactorum from silver birch and strawberry

Phytophthora cactorum strains isolated from necrotic stem lesions on Betula pendula seedlings or from Fragaria ananassa plants suffering from crown rot were pathogenic to their host plants. Only isolates from birch caused clear lesions on non-wounded bark of birch. P. cactorum isolates from birch were not detrimental to strawberry. Random Amplified Polymorphic DNA (RAPD) analysis revealed variation within P. cactorum, isolates from silver birch having different banding patterns than those from strawberry. UPGMA analysis clustered isolates from silver birch and strawberry plants into separate groups. The data show that the recent outbreak in Finland of P. cactorum in birch could not be caused by the import of strawberry plants affected by crown rot.     

Prevalence of claw lesions in Norwegian dairy cattle housed in tie stalls and free stalls

Approximately 88% of Norwegian dairy cattle are housed in tie stalls. Free-stall housing will be implemented for all cattle within 20 years. This means that most existing barns have to be rebuilt in the near future. We designed our study to estimate the prevalence of claw lesions in Norway and to reveal possible differences between tie stalls and free stalls. Fifty-five tie-stall herds and 57 free-stall herds were sampled by computerized systematic selection and 2665 cows were trimmed by 13 claw trimmers, during the late winter and spring of 2002. The claw trimmers had been taught diagnosing and recording of claw lesions. Environmental factors, management and feeding routines also were recorded. Forty-eight percent of cows housed in tie stalls had one or more claw lesions versus 71.8% in free stalls. Prevalences recorded in the hind claws were: 4.2% of the animals had dermatitis in tie stalls versus 5.7% in free stalls; 7.9% versus 38.0% had heel–horn erosions; 7.3% versus 13.6% had haemorrhages of the white line; 11.7% versus 20.4% had haemorrhages of the sole; 2.8% versus 3.2% had sole ulcers and 5.5% versus 9.7% had white-line fissures. Most lesions were mild. A model was designed to estimate cluster effects within herd and within claw trimmer. The cluster effect within herd was significant for all lesions. The cluster effect within claw trimmer was only significant for heel–horn erosions in front and hind claws and for white-line fissures in front claws. Agreements between some of the claw lesions were revealed. The study confirms that in Norwegian dairy cattle, most claw lesions are more prevalent in free stalls than in tie stalls.     

Ability of veterinary pathologists to diagnose classical swine fever from clinical signs and gross pathological findings

Clinical signs recorded in a classical swine fever (CSF)-suspect situation and the results of the subsequent post-mortem examination (PME) from swine submitted to post-mortem during the 1997–1998 CSF epidemic in the Netherlands, were presented in an experiment as anonymous cases (without knowledge of the actual infection status of the submission) to five veterinary pathologists for their judgment: CSF-suspect or non-suspect. It was presented to them in two hypothetical situations: country was free of CSF for 5 years and CSF was detected in the country 2 weeks ago. Subsequently, their judgment was compared to the gold standard (infection status of the submission on the basis of an immunofluoresence assay on tissue samples) and the sensitivity (Se) and specificity (Sp) of clinical diagnosis was estimated. Furthermore, intra- and inter-pathologist agreement on pathological diagnosis was measured. Adding information on clinical signs to information on PME resulted in a significant increase in median Se and a significant decrease in median Sp for a clinical judgment by pathologists. Also, median Se was significantly higher—and Sp significantly lower—for a clinical judgment by pathologists in a situation in which CSF was detected 2 weeks ago in the country compared to the situation in which the country had been free of CSF for 5 years. Apparently, the internal threshold of pathologists is severely adjusted depending on the actual disease situation in a country. Intra-rater agreement ranged from fair to almost perfect for a clinical diagnosis on the basis of PME. There was considerable variation between pathologists, especially if clinical diagnosis was based on the combined information on PME and clinical signs observed in the herd. Inter-rater agreement was substantial for the diagnosis based on information on PME. Inter-rater agreement was considerably lower for the diagnosis based on the combined information on PME and clinical signs observed in the herd.     

Infectious pancreatic necrosis in Atlantic salmon, Salmo salar L

A clinical and histopathological review was carried out of 21 outbreaks of acute infectious pancreatic necrosis (IPN) in Scottish Atlantic salmon, Salmo salar L., farms (13 marine and eight fresh water) during 1991-2004. A distinctive syndrome was evident in both post-smolts in sea water and fry in fresh water, where liver lesions, which had not previously been associated with IPN, became a consistent finding in addition to the more typical pancreatic and intestinal changes. Initial cases were described in post-smolts in Shetland, but by the end of the period of investigation this type of pathology had extended down the West coast of Scotland and into Ireland. Limited viral strain analysis suggested that similar strains were involved in both fresh water and sea water and that these differed from earlier isolates from rainbow trout, Oncorhynchus mykiss (Walbaum). In fresh water, recovered fish frequently developed a greatly distended intestine associated with accumulation of undigested food. In sea water, after the initial, often significant (50% or more), losses, there were many fish which failed to grow and became chronically emaciated and prone to sea louse infection. Although use of transfer diets containing immune enhancers and the selection of IPN resistant broodstock has reduced losses the disease remains a serious cause of economic loss.     

Microscopical studies of the infection of gerbara flowers byBotrytis cinerea

The formation of lesions on ray florets of gerbera flowers caused by single conidia ofBotrytis cinerea was studied in two cultivars infected by two isolates of the pathogen. No differences in reaction after inoculation with conidia of either isolate were seen on either cultivar. The conidia produced usually one germ tube not longer than 10 m, but conidia with five germ tubes were also seen. Direct penetration of germ tubes through the upper cuticle of ray florets was observed. No appressoria or other specialised structures were observed before penetration, and degradation of the cuticle did not occur. Germination of conidia and subsequent flower infection was dependent on the availability of free water, but not on the addition of external nutrients.Between 18 to 25°C, fungal development usually stopped after cuticle penetration, two to four cells around the site of penetration becoming necrotic. This number did not increase when inoculated flowers were subsequently placed at 4°C, conditions conductive for the formation of spreading lesions. When flowers were incubated constantly at 4°C, lesions became visible 3 days after inoculation as a group of 10 to 14 cells. Initially from a vesicle-like structure, mycelium spread subcuticularly or in the lumen of epidermal cells resulting in the death of 40 to 50 cells at 18 days after inoculation. Ungerminated conidia and conidial germlings which has not yet penetrated the cuticle did not cause any visible symptoms in underlying epidermal cells.     

A cross-sectional study of the prevalence and associated risk factors for capped hock and the associations with bursitis in weaner, grower and finisher pigs from 93 commercial farms in England

The prevalence of capped hock in 5601 post-weaning pigs from 93 pig farms in England was 17.2%. The prevalence increased with age. Once adjusted for age, the lowest prevalence of capped hock was observed in pigs kept on soil floors (usually covered with deep straw bedding). There was no significant increase in the risk of capped hock in pigs kept on solid concrete floors with deep straw bedding. However, pigs kept on solid concrete with some, or the entire pen, sparsely bedded and pigs kept on partially or fully slatted floors had an approximately threefold increased risk of capped hock. This did not vary significantly between these four floor types. This was in contrast to the associated risks for bursitis in the same pigs, where as the floor went from highly resilient (straw and solid floors) to hard and perforated (fully slatted) the risk of bursitis increased in a similar way to a dose response. No other variables that were measured were associated with a change in risk for capped hock, while observation of pigs slipping or slip marks and wet, dirty and worn pens were also associated risks for bursitis. These results indicate that capped hock and bursitis are both affected by exposure to floors, but in different ways. The prevalence of capped hock was associated only with floor hardness, with deep straw protecting the pigs, while bursitis was associated with both changes in bedding depth (hardness), floor material (soil versus concrete) and floor construction (solid versus slatted floors) and in factors associated with locomotion (slipping and slip marks). These results indicate that the aetiology of capped hock and bursitis might differ.     

Neuropathological survey of fallen stock: active surveillance reveals high prevalence of encephalitic listeriosis in small ruminants

This paper describes the prevalence of brain lesions in the Swiss fallen stock population of small ruminants. 3075 whole brains (75% sheep, 25% goats) were collected as part of a year-long active survey of transmissible spongiform encephalopathies (TSEs) in small ruminants conducted by the Swiss authorities between July 2004 and July 2005. All fallen stock brains were systematically examined by histopathology to obtain reliable data on histologically identifiable brain lesions. Lesions were found in an unexpectedly high number of animals (8.1% of all examined brains). A wide spectrum of diseases was detected showing that this approach provides an excellent opportunity to screen for the prevalence of neurological diseases. Encephalitic listeriosis was by far the most frequent cause of CNS lesions in both species and its prevalence was unexpectedly high when compared to notified confirmed cases. In conclusion, the prevalence of listeriosis as estimated by passive surveillance based on the notification of clinical suspects has been underestimated in the past.     

Diagnosis and surgical management of a subchondral bone cyst within the intermediate tubercle of the humerus in a horse

The case of a horse with a subchondral bone cyst in the lateral slope of the intermediate humeral tubercle is presented. Diagnosis was complicated by the unusual location and subsequent challenge in imaging the cyst. Endoscopic debridement resulted in a good outcome.