家禽肠道螺旋体病

家禽肠道螺旋体病Avain Intestinal spirochaetosis，AIS）被普遍认为是家禽生产中一个越来越严重的疾病。本病由多种螺旋体引起。螺旋体为一类外形呈螺旋状的细菌，它们主要定殖在大多数哺乳动物和家禽（包括猪、人类和家禽）的大肠中。     

Observations on avian intestinal spirochaetosis

Three SPF-laying hens were inoculated into the crop with avian intestinal spirochaetes which previously had been passaged in broiler chicks by oral inoculation (isolate 1380). Mild persisting gastrointestinal disorder developed; at nine months post inoculation spirochaetes were readily demonstrated in caecal faeces. Histologic examination of the caecal mucosa revealed many spirochaetes covering the mucosal surface and filling up the crypts lumina. Spirochaetes were found in intra- and subepithelial locations and in gaps running through the epithelium. These gaps often opened into subepithelial cavities crowded with spirochaetes ('gaplike lesions'). These lesions were seen mostly on the tips of the villi and in the deeper parts of the crypts. Massive erosion or desquamation of epithelium heavily infested by spirochaetes occurred. These findings indicate colonisation of the mucosal surface and of the crypts, penetration of the mucosa and colonisation of subepithelial compartments with spirochasetes in poultry suffering from intestinal spirochaetosis.     

Enteritis and green diarrhoea in experimental avian spirochaetosis

Chickens infected with a virulent strain of Borrelia anserina showed acute enteritis, haemosiderosis in intestinal villi and green diarrhoea. Although spirochaetes in the intestine had begun to disintegrate 96 hours after infection, enteritis and green diarrhoea continued. It is suggested that the greenish discoloration may be a consequence of enteritis and haemosiderosis.     

Observations on the pathology of experimental avian spirochaetosis

In experimental infection of chickens with a virulent strain of Borrelia anserina, peak spirochaetaemia was recorded from 72 to 96 hours. Progressive enlargement of the spleen with mottling was the predominant gross finding. Spleen, liver and small intestine showed extensive erythrophagocytosis, which continued even after the disappearance of spirochaetes from blood and tissues. While haemosiderosis was mild in the lungs, it was absent from the heart, kidney and brain. Spirochaetes were demonstrable in the spleen, liver, intestine, kidney and to a lesser extent in the lungs, but absent from the heart and brain. Widespread erythrophagocytosis and extravascular haemolysis suggest involvement of an immune mechanism in the pathogenesis of splenomegaly.     

"Intestinal spirochaetosis" of the vervet monkey

Electron microscopy revealed that 80% of captured vervet monkeys, held in quarantine for experimental use, showed extensive proliferation of spiral-shaped bacteria on the mucosal epithelium of the large bowel. A consortium, consisting of a predominant spirillum together with a spirochaete, was usually seen as a lawn covering the colonic epithelium. Sparsely populated areas showed preferential colonization of the tubular glands. Pathological changes were minimal, being confined to the microvillus border, and affected animals showed no evidence of distress. These findings are compared with those of a similar condition known as "intestinal spirochaetosis" reported in other primates, including man.     

Brachyspira and its role in avian intestinal spirochaetosis

The fastidious, anaerobic spirochaete Brachyspira is capable of causing enteric disease in avian, porcine and human hosts, amongst others, with a potential for zoonotic transmission. Avian intestinal spirochaetosis (AIS), the resulting disease from colonisation of the caeca and colon of poultry by Brachyspira leads to production losses, with an estimated annual cost of circa £18 million to the commercial layer industry in the United Kingdom. Of seven known and several proposed species of Brachyspira, three are currently considered pathogenic to poultry; B. alvinipulli, B. intermedia and B. pilosicoli. Currently, AIS is primarily prevented by strict biosecurity controls and is treated using antimicrobials, including tiamulin. Other treatment strategies have been explored, including vaccination and probiotics, but such developments have been hindered by a limited understanding of the pathobiology of Brachyspira. A lack of knowledge of the metabolic capabilities and little genomic information for Brachyspira has resulted in a limited understanding of the pathobiology. In addition to an emergence of antibiotic resistance amongst Brachyspira, bans on the prophylactic use of antimicrobials in livestock are driving an urgent requirement for alternative treatment strategies for Brachyspira-related diseases, such as AIS. Advances in the molecular biology and genomics of Brachyspira heralds the potential for the development of tools for genetic manipulation to gain an improved understanding of the pathogenesis of Brachyspira.     

禽肠道螺旋体病再度流行

螺旋体可在蛋鸡引起产蛋减少并对蛋鸡健康产生其它危害,而该病的发生率看来正在上升,尤其是在自由放牧的鸡群。该病的病变主要在盲肠和后段肠道,只要在发病后迅速开始抗生素治疗就可成功治愈。     

Experimental study on the role of Brachyspira alvinipulli in intestinal spirochaetosis of geese

Ten one-day-old goslings were inoculated orally with a Brachyspira alvinipulli strain isolated from the large intestine of geese that had died of intestinal spirochaetosis (Group A), 10 day-old goslings were inoculated orally with a B. hyodysenteriae strain (Group B), and a third group of 10 goslings (Group C) served as uninfected control. The goslings were observed daily for clinical signs. They were sacrificed on days 7, 14, 21 and 35 days postinfection (PI), and necropsied. Segments of the large intestine were subjected to histopathological, immunohistochemical, electron microscopic (TEM, SEM) and microbiological examinations. Mortality did not occur during the experimental period. However, in both groups the caecum of the goslings killed by bleeding was slightly dilated, in its lumen there was a watery, yellowish and frothy content, and the mucous membrane was slightly swollen. By histopathological, immunohistochemical and electron microscopic examination, B. alvinipulli and B. hyodysenteriae could be detected in the caecum or colon, in the lumen of the glands and sometimes among the glandular epithelial cells in goslings of the respective groups, and could be reisolated from these organs by culturing. A mild inflammation of the intestinal mucosa was also noted. In transverse section of the brachyspirae, numerous (16-22) periplasmic flagella could be detected inside the outer sheath, also depending on the plane of section.     

Porcine Circovirus Type 2 and Porcine Circovirus-Associated Disease

Porcine circovirus type 2 (PCV2) belongs to the viral family Circoviridae and to the genus Circovirus . Circoviruses are small, single-stranded nonenveloped DNA viruses that have an unsegmented circular genome. PCV2 is the primary causative agent of several syndromes collectively known as porcine circovirus-associated disease (PCVAD). Many of the syndromes associated with PCVAD are a result of coinfection with PCV2 virus and other agents such as Mycoplasma and porcine reproductive and respiratory syndrome virus. PCV2 infection is present in every major swine-producing country in the world, and the number of identified cases of PCVAD is rapidly increasing. In the United States, the disease has cost producers an average of 3–4 dollars per pig with peak losses ranging up to 20 dollars per pig. The importance of this disease has stimulated investigations aimed at identifying risk factors associated with infection and minimizing these risks through modified management practices and development of vaccination strategies. This paper provides an overview of current knowledge relating to PCV2 and PCVAD with an emphasis on information relevant to the swine veterinarian.     

猪圆环病毒病

现已确认猪圆环病毒病(PCVD)发生于全世界,对养猪业带来了严重的经济损失。尽管最近全世界许多实验室对此病进行的研究使我们获得了大量的有关知识,但我们对其病程的了解仍有重要缺陷,因而仍然无法对其进行有效防制。