Animal spongiform encephalopathies--an update. Part 1. Scrapie and lesser known animal spongiform encephalopathies.

The present article (part I) reviews recent developments in animal spongiform encephalopathies (SEs), with the exception of bovine spongiform encephalopathy (BSE), which is dealt with in part II. The article focuses on scrapie and describes epidemiological aspects and the prospects for a preclinical diagnosis. Up to now, confirmatory diagnosis of scrapie depended on histological examination of the brain, collected during post-mortem examination from sheep with clinical signs of the disease.

Antigen presenting cells and B-cells in the pig.

The central position of antigen presenting cells (APC) in the immune system and the heterogeneity of the APC family are discussed; both aspects are illustrated with data from species other than the pig. Thereafter the limited work on porcine APC is reviewed. The section on B-cells, the effector cells of the humoral immune system, exclusively focuses on 'porcine data'.

Interaction between chicken anaemia virus and live Newcastle disease vaccine.

Three groups of 150 SPF chickens were spray-vaccinated with live Newcastle disease La Sota-type vaccine (clone 30) at one day of age, and another three groups were NDV spray-vaccinated at 10 days of age. In each of the two series of NDV-vaccinated groups, one group also received at day-old 10(5) TCID50 of chicken anaemia virus (CAV) also and another group 10(5) TCID50 of CAV plus a low dose of virulent Marek's disease virus (MDV). After one week, chickens of the groups which had been NDV-vaccinated and CAV-infected at day-old, with or without MDV, showed severe respiratory distress, conjunctivitis, drooping wings and ruffled feathers.

Effects of feed additives and veterinary drugs on aldosterone production and release by porcine adrenal cells in vitro.

The preparation of suspensions of porcine adrenocortical cells is described. Within the conditions adopted, the cell suspension responded to various agents as expected. It was possible to screen drugs (standard range 0.

General aspects of transmissible spongiform encephalopathies and hypotheses about the agents.

This article reviews the shared characteristics of the group of transmissible spongiform encephalopathies (SEs), both human and animal, and the major theories regarding the nature of the agents involved. All transmissible SE diseases share two striking characteristics: the degenerative changes including vacuolation in the central nervous system, and the assumption that these disorders are caused by unconventional, transmissible agents. This article examines the major hypotheses that have been postulated about these agents: the virus theory, the virino theory, the prion theory, and the recently proposed 'unified theory'.

Serological detection of chicken flocks naturally infected with Salmonella enteritidis, using an enzyme-linked immunosorbent assay based on monoclonal antibodies against the flagellar antigen.

The Dutch Salmonella enteritidis monitoring and eradication programme for poultry prescribes a periodic examination of all breeding flocks for the presence of S. enteritidis. For the first years of the programme this was done by bacteriological examination of 50 faecal samples per visit per flock.

Structural analysis of the Actinobacillus pleuropneumoniae-RTX-toxin I (ApxI) operon.

Actinobacillus pleuropneumoniae-RTX-toxin I (ApxI), an important virulence factor, is secreted by serotypes 1, 5, 9, 10, and 11 of A. pleuropneumoniae. However, sequences homologous to the secretion genes apxIBD of the ApxI operon are present in all 12 serotypes except serotype 3.

Prevalence and incidence of scrapie in The Netherlands: a questionnaire survey.

Two independent nationwide surveys of randomly selected sheep farmers were conducted: in one a questionnaire was mailed to farmers and in the other the farmers were interviewed. The questionnaire was designed to obtain data on the occurrence of scrapie in the national sheep flock of the Netherlands. Farmers owning 30 or more ewes were selected from a database at the Ministry of Agriculture, Nature Management and Fisheries, resulting in 10,000 addresses.

Repeats in an extracellular protein of weakly pathogenic strains of Streptococcus suis type 2 are absent in pathogenic strains.

Streptococcus suis type 2 strains that are pathogenic for pigs produce a 110-kDa extracellular protein factor (EF). Nonpathogenic and weakly pathogenic strains do not produce EF or produce a protein (EF*) that is immunologically related to EF. To study the pathogenesis of S.

Cloning and characterization of the Actinobacillus pleuropneumoniae-RTX-toxin III (ApxIII) gene.

To study the role of Actinobacillus pleuropneumoniae-RTX-toxin III (ApxIII) in the pathogenesis of porcine pleuropneumonia, we cloned and characterized the gene encoding this toxin. For that purpose, we screened an expression library of genomic DNA of serotype 8 with an ApxIII-specific monoclonal antibody and isolated a 425-bp fragment of an immunoreactive clone. Using this fragment as a probe, we identified and cloned an overlapping chromosomal NsiI restriction fragment of 5.

Discrimination between virulent and nonvirulent Streptococcus suis type 2 strains by enzyme-linked immunosorbent assay.

Discrimination between virulent and nonvirulent strains of Streptococcus suis type 2 will allow proper diagnosis of diseased pigs and the identification of carrier pigs. To discriminate between virulent and nonvirulent strains, we developed two double antibody sandwich (DAS) enzyme-linked immunosorbent assays (ELISA) using specific monoclonal antibodies directed against two virulence markers of S. suis type 2.

Comparison of four different enzyme-linked immunosorbent assays for serological diagnosis of Salmonella enteritidis infections in experimentally infected chickens.

The program for the eradication of Salmonella enteritidis from chickens in The Netherlands is based on bacteriological examination of breeding flocks. There is a great need for a specific and sensitive serological screening test. For that purpose, we developed four different enzyme-linked immunosorbent assays (ELISAs), i.

Lead intoxication in cattle: a case report.

During the autumn of 1989 a feed contamination induced a widespread lead intoxication of cattle in the northern provinces of The Netherlands (Groningen and Friesland). Over 300 farms were involved, affecting about 15,500 animals (mostly dairy cattle). For a period of one to four weeks these animals took up a thousand kg of lead.

Cloning and nucleotide sequence of the gene encoding the 136-kilodalton surface protein (muramidase-released protein) of Streptococcus suis type 2.

We cloned and sequenced the gene encoding the muramidase-released protein (MRP) of a pathogenic Streptococcus suis type 2 strain to determine whether its amino acid sequence resembles that of proteins with known functions and to determine its function in virulence. The complete nucleotide sequence composing the gene and the regions flanking it was determined. The deduced amino acid sequence revealed the presence of a signal peptide at the N terminus and a cell envelope anchor at the C terminus, both of which resembled similar regions in several other surface proteins from gram-positive bacteria.

Virulence of Streptococcus suis type 2 strains in newborn germfree pigs depends on phenotype.

To determine whether the virulence of Streptococcus suis type 2 is associated with the phenotype of the strain, we infected newborn germfree pigs with 10 strains of S. suis type 2 categorized by three phenotypes. In an earlier study, the phenotypes were distinguished by the presence or absence of the muramidase-released protein (MRP) and an extracellular factor (EF) and were designated MRP+ EF+, MRP+ EF- and MRP- EF-.

Comparison of the cytolysin II genetic determinants of Actinobacillus pleuropneumoniae serotypes.

Cytolysins (Cly) I, II, and III are toxins secreted by Actinobacillus pleuropneumoniae. These toxins are thought to play an important role in the pathogenesis of porcine pleuropneumonia. ClyI and ClyII are RTX toxins and in general these toxins are encoded by operons consisting of four genes, C, A, B, and D.

Identification of two proteins associated with virulence of Streptococcus suis type 2.

The protein profiles of various cell fractions of 180 strains of Streptococcus suis type 2, which were isolated from diseased pigs, from healthy pigs when they were slaughtered, and from human patients, were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting. The isolates from diseased pigs contained two proteins that were absent in most of the isolates from healthy pigs. One of these proteins was a 136-kDa protein that was previously identified as the muramidase-released protein (MRP).