NR AVRJ
AU Ducrot,C.; Calavas,D.
TI Hypothesis on scrapie transmission from the epidemiological analysis of 15 infected sheep farms
QU Revue de médecine vétérinaire 1998; 149(8-9): 831-40
IA http://revmedvet.envt.fr/RevMedVet/1990_99/1998_US.html
PT journal article
AB An epidemiological investigation was carried out on 15 French sheep flocks infected with scrapie. The case study was based on the data already collected in the course of the technical follow-up of the farm, on the interview of the farmer and the veterinary practitioner who investigated the scrapie outbreak, and on the observation of farming condition. It consisted in describing the chronicle of scrapie within the farm, and trying to establish the source of the flock contamination and the circumstances of the spread of the disease among the sheep. Farms were located in 7 counties (French departments) ; 9 flocks produced milk, the others lambs. The source of the flock contamination does not seem to be the introduction of females in 12 of the 15 farms; but all of these farms have introduced rams, and some of the flocks have been in contact with other flocks during the transhumance (4 flocks), and/or have an infected flock in their neighborhood (2 flocks). Consequently, we have to consider the eventuality of a spreading of scrapie through rams or through infected contact with animals. For 9 of the 15 farms, the chronological pattern of the scrapie cases cannot be explained without an hypothesis on an asymptomatic carriage of the disease (healthy carriers or incubatory carriers). Moreover, even in the absence of clinically affected animals, the contamination can be massive, can take place outside the lambing period, and can affect not only young animals but also adults. Sometimes, the horizontal transmission seems te be important, for young as well as for adult animals. In some cases, the disease apparently disappeared from the farm since 4 or 5 years, due to different fighting measures depending on the farms (stamping out ; reconstitution of a safe flock from female lambs removed from their mother at lambing; replacement of the rams together with a quick removing of sick animals and placentas). The study was not designed for statistical inference and results generalization. However, it shows the necessity to reconsider the current knowledge on scrapie transmission, in terms of sources of contagion and ways of transmission ; these hypotheses have to be taken into account in later research projects.
SP französisch
PO Frankreich