Campylobacter colonization in poultry: sources of infection and modes of transmission

Since its recognition as a human pathogen in the early 1970s, Campylobacter jejuni has now emerged as the leading bacterial cause of food-borne gastroenteritis in developed countries. Poultry, particularly chickens, account for the majority of human infections caused by Campylobacter. Reduction or elimination of this pathogen in the poultry reservoir is an essential step in minimizing the public health problem; however, farm-based intervention measures are still not available because of the lack of understanding of the ecological aspects of C. jejuni on poultry farms. Although Campylobacter is highly prevalent in poultry production systems, how poultry flocks become infected with this organism is still unknown. Many investigations indicate that horizontal transmission from environmental sources is the primary route of flock infections by Campylobacter. However, some recent studies also suggest the possibility of vertical transmission from breeder to progeny flocks. The transmission of the organism is not well understood, but it is likely to be through both vertical and horizontal transmission and may be affected by the immune status of the poultry host and the environmental conditions in the production system. Intervention strategies for Campylobacter infection in poultry should consider the complex nature of its transmission and may require the use of multiple approaches that target different segments of the poultry production system.     

Enterohaemorrhagic Escherichia coli: emerging issues on virulence and modes of transmission

Enterohaemorrhagic Escherichia coli (EHEC) constitute a subset of serotypes (E. coli O157 and some other serogroups) of Shiga toxin (Stx)-producing E. coli (STEC) firmly associated with severe human illnesses like bloody diarrhoea and haemolytic uraemic syndrome. Stx production is essential but not sufficient for EHEC virulence. Most strains are capable of colonising the intestinal mucosa of the host with the "attaching and effacing" mechanism, genetically governed by a large pathogenicity island (PAI) defined as the Locus of Enterocyte Effacement. Other virulence factors carried by mobile genetic elements like PAI and plasmids have been recently described, and their role in the pathogenic process has not been fully elucidated. EHEC are zoonotic pathogens. They rarely cause disease in animals, and ruminants are recognised as their main natural reservoir. Cattle are considered to be the most important source of human infections with EHEC O157, and the ecology of the organism in cattle farming has been extensively studied. The organism has also been reported in sheep, goats, water buffalos, and deer. Pigs and poultry are not considered to be a source of EHEC and the sporadic reports may derive from accidental exposure to ruminant dejections. The epidemiology of EHEC infections has remarkably changed during the past ten years and an increasing number of unusual food vehicles have been associated with human infections. New routes of transmission have emerged, like contact with animals during farm visits and a wide variety of environment-related exposures. As for other zoonotic agents, having animals and raw products that are free from EHEC is not possible in practice. However, their occurrence can be minimised by applying high standards of hygiene in all the steps of the food production chain.     

Epidemiology and transmission of Theileria sp of cattle in Australia

Theileria sp occurs in cattle in Australia where Boophilus microplus is not present. Two species of ixodid ticks namely Haemaphysalis longicornis and H. bancrofti have been implicated as natural vectors. Experimental transmission was obtained with these two species but attempts to transmit the infection with B. microplus, Ixodes holocyclus and Amblyomma triguttatum were not successful. Although calves born in the enzootic area may become infected before one-month-old most show evidence of infection by 5 months of age. Calves born in the winter also become infected earlier than those born at other times of the year.     

Epidemiology of sheep nematodes in sub-arctic Greenland: sources of infection on rangeland grazing

Sources of nematode infection on the rangelands of a southern Greenlandic sheep farm were investigated as a part of a study of the epidemiology of Ostertagia and Nematodirus infections in a sub-arctic climate. Herbage larval counts were performed on samples collected from selected localities on the rangeland and post mortem worm-counts made on tracer lambs that had grazed these areas for the latter part of the summer season. Relatively high concentrations of larvae were found in good quality native grasses at sea-level and in grasses growing beneath canopies of willow-shrub at higher altitudes. In general, however, the infectivity of the vegetation was very low and the pick-up of infection by the tracer lambs was correspondingly small.     

Environmental sources and transmission of Escherichia coli O157 in feedlot cattle

A study was conducted in 2 feedlots in southern Alberta to identify environmental sources and management factors associated with the prevalence and transmission of Escherichia coli O157:H7. Escherichia coli O157:H7 was isolated in preslaughter pens of cattle from feces (0.8%), feedbunks (1.7%), water troughs (12%), and incoming water supplies (4.5%), but not from fresh total mixed rations. Fresh total mixed rations did not support the growth of E. coli O157:H7 and E. coli from bovine feces following experimental inoculation. Within a feedlot, the feces, water troughs, and feedbunks shared a few indistinguishable subtypes of E. coli O157:H7. A few subtypes were repeatedly isolated in the same feedlot, and the 2 feedlots shared a few indistinguishable subtypes. The prevalence of E. coli O157:H7 in water troughs of preslaughter cattle in 1 feedlot was associated with season, maximum climatic temperatures the week before sampling; total precipitation the week before sampling, and coliform and E. coli counts in the water trough.     

Epidemiology and horizontal transmission of porcine circovirus type 2 (PCV2)

Porcine circovirus type 2 (PCV2) is a small, non-enveloped, circular, single-stranded DNA virus of economic importance in the swine industry worldwide. Based on the sequence analyses of PCV2 strains, isolates can be divided into five subtypes (PCV2a-e). PCV2 is an ubiquitous virus based on serological and viremia data from countries worldwide. In addition, PCV2 DNA was discovered in archived samples prior to the first recognition of clinical disease. Recently, a worldwide shift in PCV2 subtype from PCV2a to PCV2b occurred. PCV2 DNA can be detected in fecal, nasal, oral and tonsillar swabs as well as in urine and feces from both naturally and experimentally infected pigs. PCV2 DNA can be detected early in the infectious process and persists for extended periods of time. The effectiveness of disinfectants for reducing PCV2 in vitro is variable and PCV2 is very stable in the pig environment. Limited data exist on the horizontal transmission of PCV2. Direct transmission of PCV2 between experimentally or naturally infected animals and na?ve animals has been documented and the incorporation of clinical or subclinically infected animals into a population represents a risk to the herd. Indirect transmission through the oral, aerosol or vaccine routes is likely a lesser risk for the transmission of PCV2 in most swine populations but may be worth evaluating in high heath herds. The objective of this review was to discuss data on the epidemiology and horizontal transmission of PCV2.     

Observations on the pathology of canine microsporidiosis.

The available literature on canine microsporidiosis indicates that this disease, primarily of young dogs, is a distinct clinicopathological entity. It has been confused with canine distemper and rabies, and must be differentiated from toxoplasmosis. Information available on the spectrum of pathological change associated with this disease is incomplete but a distinct pattern emerges from a study of the reports. The aetiological agent appears to have a predilection for the central nervous system and kidneys, but other tissues and organs, and especially the liver, may also be infected. Vasculitis and perivasculitis, which may include fibrinoid necrosis, seem to be a basic lesion. Cellular inflammation ranges from polymorphonuclear leukocyte infiltration in areas of necrosis to focal granulomas. There may be no cellular reaction to compact groups of organisms. Histopathological and ultrastructural studies of this case augment our knowledge of the pathological changes seen with canine microsporidiosis.     

Outbreak of microsporidiosis caused by Enterocytozoon bieneusi in falcons

Four falcons from a private collection of 137 falcons in Abu Dhabi (UAE) died suddenly in summer 2005. In order to screen for a possible disease among the remaining falcons in the aviary, all other birds were caught, examined and treated if necessary. Most of the falcons suffered from massive lice infestation and 74 falcons additionally from a heavy Caryospora sp. burden. Endoscopy revealed yellowish plaques on intestines, livers or kidneys in 70 birds (51.1% morbidity). Proliferative serositis was seen in 17 out of 24 necropsied birds with plaques on intestines, livers or kidneys, which did not resemble any known disease in falcons. However, apart from 20 falcons, which died within a 6-week period after the initial examinations due to advanced disease stages, all other falcons responded well to the treatment with dimetridazole (Emtryl), indicating protozoal disease. Immunohistochemistry confirmed the presence of microsporidial antigen. The final diagnosis of Enterocytozoon (E.) bieneusi genotype D was confirmed with materials from 6 birds by PCR and sequencing. To our knowledge this is the first report of microsporidiosis caused by E. bieneusi in raptors in general and in falcons in particular. However, it is still unclear for how long E. bieneusi was present in the falcon flock, and which role it played in the development of the disease. Predisposing factors such as high temperature and overcrowding in the aviary induced immune suppression causing massive lice infestation as well as coccidiosis, thus paving the way for invasion with microsporidial spores.     

综述蜜蜂孢子虫病的防治方法

蜜蜂微孢子虫可感染蜜蜂,引起蜜蜂孢子虫病,严重影响蜜蜂的生长繁殖,对养蜂业造成巨大损失,是感染蜜蜂的主要病原微生物之一。结合实验室经验,主要从感染前预防和感染后治疗两方面出发,介绍了蜜蜂孢子虫病的防治方法,为防治蜜蜂孢子虫病提供一个系统而全面的参考。     

副猪嗜血杆菌的流行病学和分型

副猪嗜血杆菌的唯一自然宿主是猪,而且该菌在自然环境中无法生存,这表明该菌往往是通过易感动物接触被副猪嗜血杆菌定居或感染的动物而传播的。通过这种方式,仔猪因与哺     

Equine babesiasis: Epidemiology, control and chemotherapy

Equine piroplasmosis (EP) is a hemoprotozoan disease cased by Babesia caballi and B.equi. It is a tick-borne disease principally characterized by fever, anemia, and icterus. Clinically inapparent babesia carrier horses are important in the dissemination of the disease. Clinical episodes occur under two conditions:

1. When susceptible horse stock is moved into endemic EP areas; and

2. When inapparent babesia carriers are moved into non-endemic areas, then in the presence of certain ticks, babesiasis is spread to the susceptible horse population.

Ticks are the principal vectors of equine piroplasmosis, additionally contaminated hypodermic needles have shown to spread B. equi among horses. In endemic EP areas, it has been shown that babesiasis can cause unthriftyness in foals.Control of babesiasis is principally directed at tick control. Various tickacidal sprays or dips can be used to break the life cycle of ticks.Chemotherapy, using certain aromatic diamidines, is an adjunct to tick control and also facilitates the international relocation of horses and other equidae. Objectives of chemotherapy are divided as follows: 1. In EP endemic areas, the therapeutic aim is to subdue the babesia parasites and leave the host horse in a state of premunition; and 2. In non-endemic areas, complete clearance of babesia organisms from the animal is the objective. Several aromatic diamadine pharmaceuticals are available to veterinarians.During recent years, horses and other equidae have become important in international commerce. Such commerce has focused attention on the international spread of certain infectious and communicable animal disease; among these is equine piroplasmosis (EP).Piroplasmosis is an infectious hemoprotozoan disease characterized by fever, anemia, icterus, and other signs arising from hemolysis caused by Babesia caballi or Babesia equi. The disease has been reported in horses, mules, donkeys, and zebras.⁸     

不同蛋氨酸源:DLM和HMTBA生物学等效性的再探讨

前言 在饲料中产生蛋氨酸活性作用的两种原始来源在科学和技术上的辩论，现在，已经进入第四个10年了，但争议依然颇多。理由之一是随着世界范围家禽生产的持续增长．其带来的贸易利益不断上升，而蛋氨酸在绝大多数家禽日粮中是第一限制性氨基酸。现在．全球范围唯一同时提供两种来源蛋氨酸的供应商的研究者概述了不同蛋氨酸源生物学当量的最近工作。从而，终结了这场辩论。本文许多有效的信息来自安迪苏营养研究部门主任Geraert博士和Mercier博士以及其公司的信息服务渠道。     

Epidemiology and quality assurance: applications at farm level

Animal production is relevant with respect to farm income and the position of the sector in the market, but also with respect to the quality and safety of products of animal origin, related to public health. Animal production is part of a chain of food production. Therefore, producers have to take consumer expectations and demands in the domains of animal health, welfare and environment into account. A different attitude for production has to be adopted; this attitude can be visualized in good farming practice, GFP, codes. Farmers who focused on quality in its broadest sense need a system supporting them in their management and control of quality risks. Generally speaking, there are three systems for that purpose: GFP, ISO and HACCP. When the hypothesis followed relates to animal health being a feature of quality, or else welfare and environmental issues, then animal health care can be executed following quality control principles. The HACCP concept is well suited for quality control at farm level, involving risk identification and risk management. The on-farm monitoring and surveillance system of critical control points in the animal production process is the most important tool in this procedure. Principles for HACCP application as well as certification fitness of HACCP are elaborated upon. They are illustrated by using salmonellosis in meat-pig farms as objective for an HACCP approach. It is further discussed that, in addition to animal health and quality, animal welfare and environmental issues could also be covered by an HACCP-like system in an integrated manner. Ultimately, the HACCP modules could end up in an overall ISO certification.