Listeria monocytogenes contamination of finishing pigs: an exploratory epidemiological survey in France

Listeria monocytogenes is a foodborne pathogen of major concern for public health in industrialised countries. Since L. monocytogenes carriage by pigs at the herd level could be a primary source for carcass contamination, control measures should be designed to reduce the L. monocytogenes load at the pre-harvest stage. For this purpose, an exploratory analytical survey was carried out in 2000-2001 in 93 French farrow-to-finish pig farms concerning L. monocytogenes contamination in pigs before they left for the slaughterhouse. On each farm, the L. monocytogenes status of a batch of contemporary fattening pigs housed in the same room was assessed on faecal material samples taken by means of gauze swabs wiped on the perianal region of the pigs. Fourteen percent of the batches studied had at least one contaminated sample and were therefore classified as L. monocytogenes contaminated batches. Two logistic regression models were used to assess the association between managerial and hygiene practices and the risk of L. monocytogenes contamination of the batch at the end of the finishing period on the whole data set (n = 93) and in the wet feeding farms only (n = 57). Wet feeding during the fattening period was identified as a risk factor for L. monocytogenes contamination. Risk factors related to the introduction of L. monocytogenes in pig facilities were identified for both the general and wet feeding farm data sets. Poor care paid to hygiene on the farms was found to increase the risk of being infected (boots cleaning, change room presence). When the duration of the empty period prior to the introduction of growing pigs was less than one day in the fattening section, the risk of L. monocytogenes contamination was significantly increased. For wet feeding farms, a distribution pipeline cleaning procedure including disinfection was found to be associated with a higher risk of contamination than no cleaning or a procedure consisting of rinsing with water only.     

Osmotic adaptation of Oncorhynchus kisutch Walbaum

Coho salmon yearlings, reared in France in a freshwater hatchery, were directly transferred to sea water at three different periods of the year: 14 January, 3 March and 14 April 1976. The last two experiments were realized at three different salinities: 25, 30 and 35‰.The results show important seasonal differences in the osmoregulatory responses. The direct transfer to 35‰ reveals some osmoregulatory problems which are not discernable at lower salinities. Yearlings transferred to a 35‰ sea water present a much higher and faster rise of plasma electrolytes and of branchial Na⁺K⁺ ATPase activity than fish transferred to a 25 or 30‰ sea water.It was found that a physiologically pre-adapted fish, characterized by a high level of branchial Na⁺K⁺ ATPase activity in fresh water (April) will present in sea water a slower and more regular increase in gill Na⁺K⁺ ATPase activity than fish with a low level of enzyme activity in fresh water (January–March). These smolts transferred to 25 and 30‰ sea water in April do not exhibit important variations, whereas a well-marked osmotic disequilibrium appears at 35‰. However, this osmotic stress is much more rapidly controlled than in the previous transfers.Our results suggest that the highest tolerance to sea water is reached only at time of smolting and that the time of transfer may have a direct influence on the intensity of the osmotic stress. These facts might be of considerable importance for the development of marine rearing of coho salmon in coastal areas where the salinities stay usually above 30‰ which constitutes an unusual environment for the species under consideration.     

GABA-ergic control of prolactin release in rainbow trout (Oncorhynchus mykiss) pituitaries in vitro

The involvement of γ-aminobutyric acid (GABA) in the control of prolactin (PRL) release was investigated in rainbow trout using both perifused pituitary fragments and pituitary cells in primary culture. In our perifusion system, infusion of GABA (10⁻⁶ to 10⁻⁴ M) caused an inhibition of PRL release (between 20 and 40%). Administration on perifused pituitary fragments of 3APS, a GABAa agonist, mimicked this inhibitory effect. Moreover, bicuculline, a specific antagonist of GABAa receptors, totally abolished GABA effect. When tested on cultured pituitary cells during 40h exposure, GABA (10⁻⁵ M) caused a significant decrease in PRL release (24.5%). Baclofen, a specific agonist for GABAb receptor tested at 10⁻⁶ and 10⁻⁵ M, also inhibited PRL released from cultured pituitary cells. These results demonstrate that GABA inhibits PRL release by acting directly on pituitary cells and that probably both types of GABA receptor (a and b) are involved in this regulation.

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Résumé Nous avons étudié l'implication de l'acide γ-aminobutirique (GABA) dans le controle de la sécrétion de prolactine (PRL) chez la truite arc-en-ciel en utilisant à la fois des fragments d'hypophyse perifusés et des cellules hypophysaires en culture. Dans notre système de périfusion, le GABA (10⁻⁶ à 10⁻⁴ M) inhibe la libération de PRL (entre 20 et 40%). L'administration sur les fragments d'hypophyse périfusés de 3APS, un agoniste des récepteurs GABAa, reproduit ces effets inhibiteurs. De plus, la bicuculline, un antagoniste spécifique des récepteurs de type GABAa, abolie complètement les effets du GABA. Lorsqu'il est testé pendant 40h sur des cellules en culture, le GABA (10⁻⁵ M) réduit de manière significative la libération de PRL (24.5%). Le Baclofen, un agoniste spécifique des récepteurs GABAb testé à 10⁻⁶ et 10⁻⁵ M, inhibe aussi la libération de PRL par les cellules en culture. Ces résultats démontrent que le GABA inhibe la libération de PRL en agissant directement sur les cellules hypophysaires et que les 2 types de récepteurs GABA (a et b) sont impliqués dans cette régulation.

     

Growth, fatness and gross biochemical composition of the Japanese oyster, Crassostrea gigas, in Stanway cylinders in the Bay of Arcachon, France

A new method of oyster cultivation, the Stanway oyster cylinder, has been investigated in the Bay of Arcachon since 1989. A comparative study was carried out between the growth of spat and 18-month-old Crassostrea gigas oysters, in cylinders and in traditional bags. The growth in height and in whole weight was lower in cylinders. In contrast, the tests showed a better quality of the meat, with higher condition index and higher carbohydrate content, and a better quality of the shell, with higher density and better shape. Therefore, because of the improvement in oyster quality, the use of the cylinder seems to be advantageous for the Arcachon oyster industry.     

The influence of different food sources on cercarial production in Lymnaea truncatula experimentally infected with Digenea

Experimental infections of Lymnaea truncatula with a digenean species (Fasciola gigantica, F. hepatica, or Paramphistomum daubneyi) were performed under laboratory conditions to study the effect of four sources of food (microalgae, romaine lettuce, wheat germs, or modified Boray diet) on cercarial production. The mean number of F. hepatica, F. gigantica, or P. daubneyi cercariae was significantly greater when snail food was microalgae or Boray diet. The lowest cost prices for 100 metacercariae of F. hepatica (9.7-10.1 euros) were noted when algae of Boray diet were used as food for snails. In contrast, the highest prices (18.0-18.5 euros) were found in lettuce-reared snails. The choice of a source of food for breeding the intermediate hosts of F. hepatica and collecting metacercariae must take into account the importance of the commercial demand for metacercariae and will depend on the strategy the producer wishes to develop.     

Ultrasonographic fetal well-being assessment, neonatal and postpartum findings of cloned pregnancies in cattle: A preliminary study on 10 fetuses and calves

Cloned pregnancies in cattle are considered to be at risk due to a variety of fetal or adnexal abnormalities. Data is lacking concerning the possibility of transabdominal ultrasonography in the assessment of these high risk pregnancies. Transabdominal ultrasonography has rarely been reported in the assessment of bovine cloned pregnancies. Ten Holstein heifers carrying 8-month-old cloned fetuses were assessed by transabdominal ultrasonographic examination during the 3rd trimester of pregnancy. Fetal heart rates (FHR), movements, adnexal appearance, and placentome size were recorded. The outcome of the pregnancies was also noted and potential indicators of fetal demise recorded. Survival rate 1 week after birth was 30%. Mean FHR was 113 beats per minute (range: 92 to 128 bpm) during the fetal ultrasonography. No correlation between FHR and fetal activity was found. Fetal hyperactivity and imaging of hyperechoic particles in both allantoic and amniotic fluids were possible signs of fetal distress. Despite the size of the fetus and the deep bovine abdomen, fetal transabdominal ultrasonography can be performed in cattle. This preliminary study points to the necessity of further larger studies for defining normal and abnormal findings in bovine late pregnancy.