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Summary The cellular population lining the bronchiolar and alveolar epithelium of the lower respiratory tract of three clinically healthy, purebred Suffolk lambs of both sexes and 3–4 months old was studied using a transmission‐electron microscope. The epithelium of primary and secondary bronchioles consisted of four cell types: basal cells, intermediate cells, ciliated cells, and non‐ciliated (Clara) cells, whereas the epithelium of terminal and respiratory bronchioles consisted of only two kind of cells: ciliated and Clara cells. The alveolar wall, including alveolar ducts and saccules, was covered by type I and type II pneumocytes. In addition, the presence of pulmonary intravascular macrophages was a constant in most of the alveolar capillaries. The morphologic characteristics of all these cells are described in detail and discussed.

Summary In an attempt to estimate the importance of maedi/visna virus infection in Moroccan sheep and to assess the relationship, if any, between seroreactivity and pulmonary lesions, an abattoirbased serologic survey was undertaken over a period of 2 years. A total of 1000 blood samples and related lungs were collected from sheep of different breeds and ages slaughtered at three major municipal abattoirs in Morocco (Casablanca, Kénitra and Rabat). The agar gel immunodiffusion test showed that the seropositivity for all samples was 24.8%. At post‐mortem examination, 107 out of the 248 (43.1%) sheep scored seropositive had gross lesions of maedi; typical microscopic lesions were observed in 125 (50.4%) seropositive sheep, including the 107 with gross lesions. Of the 752 seronegative animals, only 13 (1.7%) sheep had macroscopic maedi‐like lesions. Seventeen (2.2%) of these seronegative cases, including those with gross lesions, had histologic pulmonary changes consistent with maedi. No other maedi/visna‐associated lesions were found during this study; however, coexisting secondary bacterial bronchopneumonia was frequently encountered. The association between serologic and pathologic findings is reported and discussed. Résumé Infection au Lentivirus Ovin (Visna‐maedi) au Maroc: Une Enquête Sérologique completée par Etude Anatomo‐pathologique Afin d'apprecier l'importance de l'infection Visna‐maedi du mouton au Maroc et d'étudier d'éventuels rapports existant entre les résultats sérologiques et les lésions pulmonaires, une enquête séro‐pathologique basée sur des visites aux abattoirs a été menée durant une période de deux ans. Les prélèvements de sang déstinés au sondage sérologiques ainsi que les poumons respectifs ont été effectués sur 1000 ovins, d'âge et de race différents, abattus au niveau de trois principaux abattoirs municipaux du Maroc (Casablanca, Kénitra, Rabat). La méthode sérologique d'immunodiffusion sur gélose (I.D.G) a révélé un pourcentage de positivité de 24,8% sur l'ensemble des échantillons testés. Quant à l'étude anatomo‐pathologique, elle a montré que 107 sur 248 (43, 1 %) animaux réagissants présentaient des lésions macroscopiques alors que 125 cas (50, 4 %) positifs, parmi lesquels figuraient les 107 ayant les lésions macroscopiques, avaient des lésions microscopiques typiques du maedi. Sur les 752 animaux séronegatifs, 13 (1, 7%) ovins seulement présentaient des lésions macroscopiques comparables à celles du maedi. Histologiquement, 17 cas séronégatifs, y compris ceux avec des lésions macroscopiques, avaient des lésions caractéristiques du maedi. Aucune autre lésion associée au complexe Visna‐maedi n'a été décelée, parcontre, des lésions de bronchopneumonie dûes à des surinfections bactériennes ont été communément rencontrées. Il convient donc de retenir une corrélation supposant une relation étiologique entre les constatations sérologiques et anatomo‐pathologiques.

The purpose of this study is to attempt the induction of early immunopotentiation of antibodies specific to fimbriae of Salmonella enterica serovar Enteritidis (SE), by administering thymulin and zinc to SE-vaccinated chicken breeders, and the improvement of protection against a controlled-live challenge by SE. The first two groups of breeders were administered subcutaneously at 15 and 19 weeks of age a killed SE vaccine. Breeders of the third and fourth groups were left unvaccinated. Breeders of the first group, immunopotentiated by thymulin and zinc, were able to induce the earliest antibodies in their pooled sera at 2 weeks post the first SE-vaccination, specific to fimbriae (approximately 21 KDa) of SE. However, the second group that was only vaccinated with the same SE-vaccine produced specific antibodies to fimbriae at 3 weeks following the second vaccination (22 weeks of age). Breeders of the third group, that were neither SE-vaccinated nor immunopotentiated by thymulin and zinc, but were challenged by live SE at 22 weeks of age, were able to show specific antibodies to fimbriae at 3 weeks post challenge (25 weeks of age). The fourth group that was deprived of SE-vaccination, immunopotentiators, and challenge didn't show any background antibodies specific to SE-fimbriae. The presence of the earliest antibody-immunopotentiation to fimbriae of SE in breeders of the first group, administered thymulin and zinc, was associated with the lowest frequency of SE-infected ceca (10%) among the challenged groups. In addition, breeders of the first group were the only challenged birds resulting in absence of SE infection in their cecal tonsils. The first group-vaccinated, immunopotentiated, and challenged, and the second group-vaccinated and challenged only resulted in breeders with absence of SE infection in their oviducts and spleens. In conclusion, immunopotentiation of chicken breeders by thymulin and zinc induces the earliest specific antibodies to fimbriae of SE associated with the lowest frequency of SE-infected ceca, and absence of SE infection from cecal tonsils, oviducts and spleens.