An outbreak of rabbit viral hemorrhagic disease (RVHD) and of myxomatosis occurred in a free-living population of rabbits (Oryctolagus cuniculus) near Paris (France) in 1995. Annual mortality rates were 88% in adults and 99% in juveniles. There was no difference in mortality rates between males and females. Since most adults were protected with myxoma antibodies after May, they probably died of RVHD. Mortality lasted throughout the year despite high proportions of rabbits having developed myxomatosis and RVHD antibodies, which suggests that the combination of the two diseases and the immunosuppressive characteristics of myxoma virus could be responsible for the mortality caused by RVHD. The proportion of juveniles with RVHD antibodies increased with their weight. Seroconversion against RVHD occurred in spring and autumn.

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A study carried out on 15 free-living populations of wild rabbits showed that VHD (Viral Haemorrhagic Disease) antibodies were present in all these populations. The nonspecificity of these antibodies does not enable to conclude that VHD was present in all these populations. However, our results suggest that most wild populations are partially protected against VHD either directly by VHD virus, or by VHD-like and non-pathogenic viruses. Moreover, the presence of antibodies on uninhabited islands allows to formulate certain hypotheses about the spread of these viruses.Resume. -Une etude menee au sein de 15 populations sauvages de lapin de garenne a mis en evidence la presence d'anticorps VHD (Viral Haemorrhagic Disease) dans toutes ces populations. Le manque de specificite de ces anticorps ne permet pas de certifier la presence de VHD dans toutes ces populations. Toutefois, ces resultats suggerent que la majorite des populations sauvages sont partiellement protegees centre la VHD, soit directement par le virus de la VHD, soit par des virus apparentes et non pathogenes. En outre, la presence d'anticorps en milieu insulaire inliabite permet d'evoquer certaines hypotheses relatives au mode de transmission de ces virus.

Abstract. An enzyme-linked immunosorbent assay (ELISA) was developed and compared with 2 reference diagnostic tests (indirect immunofluorescence [IF] and complement fixation) to detect myxoma virus-specific antibodies in sera from 50 rabbits experimentally vaccinated with an attenuated strain of myxoma virus or with a Shope fibroma virus. The ELISA was highly specific (100% specificity) and sensitive (100%, 21 days after homologous vaccination). In a comparison of the ELISA with the IF test in 128 wild rabbits from France, discrepant results were obtained in only 11 (8.6%) animals, which were positive with the ELISA and negative with the IF test. The higher sensitivity and the good specificity of the ELISA was confirmed in a serologic survey of 118 rabbits from 2 Kerguelen (Indian Ocean) islands, where the prevalence of myxomatosis varied considerably. The ELISA is an alternative serologic test for diagnosis, vaccine evaluation, and seroepidemiologic surveys of myxomatosis.Myxomatosis is a specific viral disease of the European rabbit (Oryctolagus cuniculus), causing severe or attenuated clinical manifestations in domestic and wild rabbit populations. 4,6,7,13 The etiologic agent of myxomatosis is a large double-stranded DNA virus in the Leporipoxvirus genus of the Poxviridae family. It was released in Australia and Europe in 1950 and 1952, respectively, as a biological control for wild rabbits. Myxomatosis is now endemic in European and Australian rabbit populations. Diagnosis is generally based on clinical signs alone, but the occurrence of atypical cases 11 with an absence of myxoma lesions has revealed the need for specific and sensitive diagnostic tests.The immune response in infected rabbits is characterized by the early appearance and persistence for several months of specific antibodies that may be detected by complement fixation (CF) 2,5,7 virus neutralization, 5 immunodiffusion, 17,18 or immunofluorescence 3,10 tests. These tests are adequate for most purposes but are time consuming and not really suitable for the estimation of disease prevalence in wild animals. Furthermore, they do not allow precise quantification of the antibody levels in animal serum. Previously, an enzyme-linked immunosorbent assay (ELISA) was developed using virus extracted from the skin tissue of infected rabbits as antigen. 20 The interFrom the Laboratoire associé de Microbiologie Moléculaire, Ecole Nationale Vétérinaire, Toulouse and Institut National de la Recherche Agronomique, 23, chemin des Capelles, F-31076 Toulouse cedex-3, France.Received for publication April 30, 1997. assay reproducibility of the test was unsatisfactory, probably because of the poor quality of the antigen. 20 The ELISA described here was based on purified myxoma virus antigen and is compared with other serologic methods. It proved to be sensitive and specific for the detection of myxoma antibodies both in fresh serum and in dried blood on a blotter. The method was evaluated for diagnosis with sera from vaccinated and wild rabbit. Material and meth...

Une enquête réalisée sur les bovins conduits aux abattoirs de Dakar de novembre 1974 à juin 1975 en utilisant simultanément la S. A. W., la réaction de COOMBS et la F. C'. permet aux auteurs de préciser les résultats obtenus au cours d'un sondage préliminaire (mai à août 1974). L'analyse des résultats recueillis dans ces deux études portant sur un ensemble de 1 134 sérums, autorise à avancer un pourcentage d'infection de 8,7 p. 100, pour un seuil d'interprétation de 60 UI/ml en agglutination, qui passe à 17,2 p. 100, pour 30 UI/ml. L'infection apparaît plus fréquente chez les femelles que chez les mâles et présente une incidence maximale chez les sujets de 7 à 9 ans suivant en cela l'âge moyen des sujets abattus.