Annales de recherches veterinaires. Annals of veterinary research最新文献

This article reviews published data (October 1st, 1990) on 4 types of cytotoxins produced by animal and human pathogenic strains of E coli, ie, verotoxins, also named Shiga-like toxins, cytotoxic necrotizing factors, haemolysin, and cytolethal distending toxin. The biological and molecular properties are described for each type of cytotoxin, the association of producing strains with animal pathology, and the role of domestic animals as reservoirs of strains pathogenic for man.

Red fox behavioural ecology was studied in a rabies-enzootic area in order to determine how population size is balanced despite rabies-induced mortality. The results suggest that the red fox rabies virus equilibrium evolves, and is due to the solitary behaviour pattern of the fox which reduces the risk of virus transmission from on territory to another; and to the subsequent autumn dispersal, which allows the local fox population to recover in the space of under a year. The hypothesis is put forward that rabies does not seem to regulate fox population size. There would therefore be no reason to fear a population explosion after oral immunisation of foxes against rabies.

Free native horseradish peroxidase (PO) or PO coupled to either syngeneic mouse serum albumin (PO-MSA) or to xenogeneic bovine serum albumin (PO-BSA) in sterile phosphate buffered saline (PBS), were injected repeatedly into newborn BALB/c mice. Serum antibody titres were evaluated by enzyme immunoassay on 30 and 60 of age and on d 75 and 88 after 1 or 2 booster injections respectively. The response to PO was found in all sera from neonatal immunized mice with all forms of PO, but only in control adult mice immunized by PO-BSA. Immunization with either PO-MSA or PO-BSA induced mainly IgG anti-PO antibodies of high avidity while immunization with free PO resulted in the induction of both IgM and IgG anti-PO antibodies of low avidity. A large number of hybridomas with anti-PO specificity were obtained from the spleen of mice injected with PO-MSA. The results indicate that neonatal immunization of mice with PO is an effective procedure, which is probably applicable to other proteins.

In 1975, the French law on veterinary drug products was adopted. In 1976, the Ceyrac law prohibited the use of oestrogens. After various scandals, Parliament voted unanimously in favour of the "Rocard" law in 1984. This law defined the use of anabolics very strictly. In 1985, the EEC decided to ban anabolics. This ban has resulted in the illegal use of many kinds of substances, a situation which is difficult to control. This has exposed public health to risk, and has perturbed commercial rules and regulations within the EEC countries.

Milk is the most important route of lentivirus spread in sheep and goat. Blood and milk cell populations were characterised with specific monoclonal antibody at lambing time in 4 primiparous seropositive ewes. Two of the ewes (3/4 half udders) produced milk with infected cells. The cell number/ml was always higher in milk and blood from virus-producing animals. In ewes which spread infected macrophages CD8 lymphocyte number was increased in blood and milk. Serological tests are able to detect infected animals but virus production is reflected immediately by an increase of CD8 lymphocytes in milk.

The aim of this study was to assess the possible modifications in the conventional intestine when deprived of its symbiotic microflora. The experiment was designed to study the effect of a heavy antibiotic dose on fecal microflora during the 33-d treatment period as well as its effects upon the intestinal wall. Conventional adult mice received either a casein-starch diet (conventional controls) or an antibiotic-supplemented (0.66% dry matter, DM) diet (treated conventionals); Furthermore, germ-free (axenic) mice taken from isolators to the open animal room received the same antibiotic-supplemented diet (treated axenics) Fecal microbial population remained around 10(8)/g in the conventional mice while it decreased to 10(3)/g in the treated conventional mice. Fecal microbial population of the treated axenic mice dropped to 10(2)/g. At the end of the 33-d treatment period, no significant difference in ileal villus height between the treated or control groups no difference either was seen in the aspects of the villus and cell surface as shown by scanning electron microscopy. In the control group, however, development of bacterial colonies exhibiting various shapes were observed on the intestinal mucus. Although it was found that antibiotic treatment was followed by significant changes in microbial population and biochemical composition of digestive contents, this study concluded that the structure of the distal ileal epithelium was not impaired.

African swine fever virus was detected in various samples using a molecular hybridization technique. A fragment located in a constant area of the viral genome was biotin-labelled. This probe, when present at a concentration of 100 ng/ml of the hybridization solution, could detect 10 pg of target DNA immobilized on nitrocellulose with cellular DNA and RNA. The virus was evidenced after being passaged on monkey kidney cells, either 8 h post-inoculation (pi) if the multiplicity of infection (MOI) was at least 1 hemadsorbing unit (HAd) per cell, or 24 h later if the inoculum was diluted up to 10(-3) HAd per cell. When passaged on pig leukocytes with a MOI of 0.1 HAd per cell, the virus was evidenced 12 h pi, or 24 h pi with a MOI of 10(-2) HAd per cell. The probe did not hybridize with another DNA virus passaged on cells, neither did it react with non-infected blood or ham, but did so if African swine fever virus was resuspended with the samples. The spleen from uninfected pig and the lymph nodes from a pig which had died from hog cholera were found to be negative, whereas the spleen from a pig which had died of African swine fever was positive. These samples were also tested with a 32P-labelled probe whose sensitivity was 10-fold higher. A non-radioactive probe could be used both for the sensitive and specific diagnosis of African swine fever and the detection of the virus in an epidemiological survey.

Pasteurella multocida can often be isolated from pneumonic lungs in pigs. There is little information about the pathogenesis of this infection. Attachment of microorganisms to eucaryotic cells is considered to be a prerequisite for colonization of the host in the pathogenesis of bacterial infections. Forty-seven P multocida strains isolated from pigs in France, and belonging to capsular type A or D were tested for their ability to agglutinate human erythrocytes, and to adhere to tracheal and lung cells. Each isolate was tested for dermonecrotic toxin production. Adherent strains were further observed by electron microscopy to look for attachment structure. Only type A strains agglutinated human O erythrocytes, but no relationship was observed between hemagglutination and dermonecrotic toxin production. The results of the adherence tests showed a greater affinity (P less than 0.05) of type A strains for lung cells (50% were adherent, whereas only 20% of type D strains were adherent) but did not reveal any correlation between adherence and the presence of dermonecrotic toxin. Microscope observations showed that these P multocida strains did not possess any pili-like structures. In conclusion, by means of the adherence test we were able to demonstrate a stronger adherence of type A strains and this adherence did not seem to be related to pili-like structures.

The mutagenicity of trenbolone, a synthetic androgen, was studied in a number of genotoxicity tests using in vitro and in vivo systems for gene mutations, chromosomal mutations and primary DNA damage demonstration. Only 2 tests were found to be positive or dubious: the in vitro micronucleus test in SHE cells (however, this test was negative in 2 other cell lines: C3H and CHO cells) and the Ames test for 1 of the 5 studies which found a positive result in TA 100 strain without metabolic activation. Repetition of this study with pure trenbolone showed no genotoxic activity; trenbolone was therefore considered to be devoid of genotoxic activity.

The chronicle of misuse of anabolics in veal calf production started with diethylstilbestrol, which was used until 1980. During the following years until 1988, illicit preparations contained various steroidal sex hormones, predominantly estradiol, 19-nortestosterone, testosterone and their esters. Since autumn 1988, the sex hormones have been replaced by anabolic beta-agonists such as clenbuterol and salbutamol. The real extent of misuse has not been determined. If sex hormones have been applied, most residue levels in the periphery apart from the injection site will remain less than 10(-9) ng/g. At the injection sites total residues may be in the mg range, and biological effects on the consumer cannot be excluded. The orally active beta-agonist clenbuterol is accumulated in most organs and a 0 d withdrawal period is not feasible. Immunoassays are approved methods for screening purposes, whereas confirmation is mostly carried out by gas chromatography coupled to mass spectrometry.