Henri Vindevogel

An Efficient Sampling Technique Used To Detect Four Foodborne Pathogens on Pork and Beef Carcasses in Nine Belgian Abattoirs

The method presented in this paper should prove useful in assessing the effectiveness of HACCP plans developed in slaughterhouses. Samples were collected by swabbing well-defined areas of pork and beef carcasses with sterile gauze. Between 160 and 420 half-carcasses were swabbed in each of nine pork or beef slaughterhouses. Swabs from five carcasses were placed in the same sterile Stomacher bag, constituting a single composite sample. Standard or validated analytical methods were used to isolate and characterize four foodborne pathogens. Salmonella spp., Listeria monocytogenes, Campylobacter spp., and verocytotoxin-producing E. coli were detected, respectively, in 27, 2, 2, and 14% of the pork samples and 0, 22, 10, and 5% of the beef samples. Of the 10 samples positive for E. coli O157, only one yielded an isolate confirmed to be enterohemorrhagic. Since Salmonella spp. appear as the main contaminant port (27%) and L. monocytogenes as the main containment of beef (22%), any slaughterhouse sampling plan should include testing for the former in the case of pork carcasses and for the latter in the case of beef carcasses. One should also test regularly for the presence of E. coli O157 and Campylobacter spp. in pork and beef abattoirs. The method presented here is an easy way to assess the contamination rate of carcasses at the end of the slaughtering process.

Infectious agents associated with epizootic rabbit enteropathy: Isolation and attempts to reproduce the syndrome

Abstract Epizootic rabbit enteropathy (ERE), a highly lethal (30–80% mortality) disease of broiler rabbits aged 6–14 weeks, first appeared in 1997 in French intensive enclosed rabbitries and is of unknown aetiology. Bacteriological, virological and parasitical examination of the intestinal contents of rabbits that had died either in spontaneous field cases or after experimental reproduction of ERE, were undertaken in an attempt to identify infectious agents that may play a role in the disease. Two bacterial strains, Clostridium perfringens and non-enteropathogenic Escherichia coli were repeatedly isolated at high faecal counts from naturally infected animals. In field cases, a correlation between typical gross lesions of epizootic enteropathy and the presence of the alpha toxin of Cl. perfringens was observed (P <0.0001; Chi-squared test). Although attempts to reproduce the disease by inoculation with different pools of cultivable bacterial strains failed, the disease was successfully reproduced by inoculation with one French and two Belgian samples of caecal contents.

The Role of Latency in the Epizootiology of Infectious Bovine Rhinotracheitis

Latency is one of the major problems associated with the infection of cattle by the virus of Infectious Bovine Rhinotracheitis/Infectious Pustular Vulvovaginitis, or Bovineherpesvirus 1 (BHV 1). Both wild virulent strains and the attenuated vaccine strains can remain latent in cattle and may be reactivated by several stimuli including the use of glucocorticoids, such as dexamethasone.

New data on the transmission of pigeon circovirus.

Nineteen racing pigeons aged from one to five years were examined postmortem. pcr tests showed that the spleens of 16 of them were positive for pigeon circovirus, the livers of six were positive, and blood from one of them was positive for the virus. Five of 44 embryos in embryonated eggs collected from three lofts were positive by pcr, but swabs taken from the crops of 64 adult birds which were feeding one- to 10-day-old squabs in these three lofts were negative for the viral dna.

Pathogenesis of pigeon herpesvirus infection

Abstract Experiments were designed to investigate the pathogenesis of pigeon herpesvirus (Pigeon herpesvirus 1, PHV) infection. Experimental pharyngeal infection of susceptible pigeons may be followed by viral localization and development of lesions outside the upper digestive and respiratory tracts. Viraemia was detected during the primary infection in some pigeons previously treated with cyclophosphamide (Cy). After primary infection, viral re-excretion was twice provoked by Cy-treatment in all pigeons except one, and was as heavy as that following the initial infection. During the first episode of re-excretion one pigeon presented viraemia, died a few days later with signs of encephalitis, and PHV was isolated from the brain. No viraemia could be detected during the second episode of re-excretion and virus was only isolated from the pharynx and trachea, probably by contamination via the larynx. Virus was never isolated from genital organs taken from either dead or killed animals, but sublethal infection of pigeon embryos could be produced experimentally. It was also shown that, after cell infection, PHV can be transmitted in vitro from cell to cell in the presence of high titres of specific antibodies. PHV can thus be spread either by tissue contiguity, even in the presence of specific antibodies, or by viraemia especially when the pigeons are immuno-suppressed.

Pigeon herpes infection: Excretion and re-excretion of virus after experimental infection

Abstract The excretion of pigeon herpesvirus and the development of neutralizing antibodies were studied after experimental infection of two groups of pigeons, one of which had previously been treated with cyclophosphamide (Cy). Natural excretion of the virus occurred in both groups during a 90-day period without influencing the titre of antibodies, the pigeons becoming asymptomatic carriers of the virus after the initial infection. Birds previously treated with Cy developed lower titres of neutralizing antibodies. The Cy-treatment of all the animals 90 days after the experimental infection provoked re-excretion of the virus.

Comparison of the effect of trisodium phosphonoformate on the mean plaque size of pseudorabies virus, infectious bovine rhinotracheitis virus and pigeon herpesvirus.

Abstract The effect of various concentrations of trisodium phosphonoformate on the titre and the mean plaque size of pseudorabies virus (SHV), infectious bovine rhinotracheitis (IBR) virus and pigeon herpesvirus (PHV) was studied. Phosphonoformate significantly reduced the mean plaque size of all three viruses whatever the concentration used. However, an increase of the concentration of phosphonoformate over 100 μ m per ml in the overlay medium did not further reduce the mean plaque size of PHV. Phosphonoformate also produced a decrease in the titre of the three viruses at the highest concentration. SHV was the most susceptible to the effect of trisodium phosphonoformate and PHV was the least susceptible. This finding might be of significance for a possible clinical application in the treatment of local lesions produced by PHV infection.

Pigeon herpes infection: Natural transmission of the disease

Abstract Studies on the persistence and transmission of pigeon herpesvirus ( Pigeon Herpesvirus 1 , PHV) in a dovecot containing pigeons which were naturally infected more than a year previously are reported. Three out of 10 mature pigeons were still shedding virus. They transmitted it to their offspring during the first days of life. Egg transmission of the disease seems unlikely since PHV could not be unmasked in cell cultures of embryos of contaminated pigeons. All mature pigeons possessed neutralizing antibodies. Parental passive immunity seems to be conferred on the squabs through the egg yolk and protects from the worst effects of infection. Seven of 10 squabs were asymptomatic carriers of the infectious agent after weani g although they were all devoid of detectable antibodies.

Cross-sectional study of the association between pathological conditions and myxoma-virus seroprevalence in intensive rabbit farms in Europe

Myxomatosis is a major viral disease of the European rabbit (Oryctolagus cuniculus). Two forms of the disease (nodular and amyxomatous) exist. The clinical diagnosis of the nodular form is easily performed on the basis of typical skin lesions whereas that of amyxomatous forms must be based on virus isolation or detection of specific antibodies to myxoma virus (MV). The seroprevalence of MV was studied between March 1998 and February 1999 in 16 farms from three European countries considered free of myxomatosis on the basis of the absence of typical clinical signs. MV antibodies were detected by enzyme-linked immunosorbent assay (ELISA) (sensitivity 100%, specificity 90%) in all 16 farms; the seroprevalences corrected for test inaccuracy (95% confidence interval) were 55+/-7.7% and 37+/-6.1% for does and broilers, respectively. The association between herd sizes, types of rabbitries, and presence of recurrent respiratory or digestive troubles and seroprevalence of MV antibodies was tested in logistic multiple regressions. In all models, the seroprevalence of MV antibodies was significantly higher in herds (does and broilers) with recurrent respiratory or digestive troubles than in herds without these problems. The seroprevalence was also higher in herds (does and broilers) where animals were housed totally or partially in outdoors rabbitries than in totally enclosed rabbitries. The effect of herd sizes on the presence of MV antibodies was the same in does and broilers; intermediate sizes were at lower risk than the smaller and larger ones.

Cellular changes in the bursa of fabricius and thymus of cyclophosphamide-treated pigeons.

Abstract The histological changes occurring in the bursa of Fabricius and in the thymus of 4-week-old pigeons after cyclophosphamide (Cy)-treatment are described. The bursa underwent atrophy and lymphoid cells virtually disappeared from the follicles in which only the reticulo-epithelial cells persisted. The thymus also showed marked degeneration accompanied by lymphocyte depletion. The development of lesions ceased 4 days after the beginning of treatment in the thymus and 6 days later than this in the bursa. After 2 weeks, the two organs showed regeneration. The histological appearance of the thymus returned to normal after 3 weeks and that of the bursa after 7 weeks. Cy-treatment of pigeons produced a profound B and T-cell deficiency which is more transient for T-cells.