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SUMMARYThe effect of artificial air-ionization on air-borne transmission of Newcastle disease virus (NDV) infection in chickens was studied in an isolated system consisting of two side-by-side cages with solid walls and a wire-gauze roof. During a 3-week observation period more than 90 % ofthe uninoculated indicator chickens, housed in one of the cages, contracted the virus shed to the air by the NDVinoculated, diseased birds in the neighbouring cage. This air-borne transmission of NDV was completely prevented by increasing the ion concentration in the test room by a constant negative corona discharge above the wire-gauze roof. On the other hand, spreading of the infection within a group of chickens housed in a single cage was not affected by air ionization.These and other results suggest that artificial air-ionization may protect animals from certain air-borne infections by interfering with microbial aerosol formation and/or by facilitating their decay.

The occurrence of hemagglutination-inhibiting antibodies to human coronavirus OC43 was investigated in a material of random sera in Finland from 283subjects including children and adults. Antibodies were found in 172 (60.8%). The highest incidence of positive sera was obtained from the age groups between 21 and 50 years-about 85% of the investigated sera were positive in these age groups. It can be concluded that infections with OC43 or related coronaviruses are rather common in Finland.

Summary Isolations of M. hyorhinis from the lungs and nasal mucosa were compared with the histopathologic lesions established in these organs in lung and nasal mucosal samples from 525 piglets of different ages. M. hyorhinis was isolated considerably more often from pneumonic than from negative lungs, and the same applied to rhinitic and negative nasal mucosal samples. The differences in the frequency of M. hyorhinis in positive and negative cases were statistically significant. The results for the lungs distributed according to the age of the pigs showed that M. hyorhinis was considerably more infrequent in the pneumonic lungs of pigs aged under two weeks than in those of older animals in which no distinct difference could be demonstrated. The mycoplasma was not isolated at all from samples taken from pigs under one week of age. Zusammenfassung Über das Vorkommen von Mycoplasma hyorhinis in Respirationsorganen von Schweinen unter besonderer Berücksichtigung der enzootischen Pneumonie Lungen und Nasenschleimhaut von 525 Ferkeln wurden auf das Vorkommen von M. hyorhinis kulturell untersucht und die Ergebnisse mit den histopathologischen Befunden verglichen. M. hyorhinis wurde aus pneumonisch veränderten Lungen wesentlich häufiger isoliert als aus Lungen, die keine histopathologischen Veränderungen aufwiesen. Ebenso waren Isolierungen des Agens aus Nasenschleimhaut bei Vorliegen von Rhinitis‐Veränderungen zahlreicher als aus Schleimhaut von Tieren, bei denen keine solchen histopathologischen Veränderungen nachzuweisen waren. Der zahlenmäβige Unterschied war statistisch signifikant. Bei Ferkeln im Alter von weniger als 1 Woche konnte M. hyorhinis nicht isoliert werden. Bei Tieren, die 1–2 Wochen alt waren, wurde das Agens weniger oft isoliert als bei älteren Schweinen. Résumé Sur la présence de Mycoplasma hyorhinis dans les organes repiratoires de porcs, en considérant plus particulièrement la pneumonie enzootique On examine des cultures des poumons et des muqueuses nasales de 525 porcelets, quant à la présence de M. hyorhinis, et l'on compare les résultats avec les observations pathohistologiques. On isole beaucoup plus souvent M. hyorhinis dans des poumons à lésions pneumoniques que dans des poumons sans modifications pathohistologiques. De même, on isole plus souvent l'agent dans des muqueuses nasales présentant les modifications de la rhinite que dans des muqueuses d'animaux dépourvus de telles modifications. La différence numérique est statistiquement significative. Chez des porcelets âgés de moins d'une semaine, on n'a pas isolé de M. hyorhinis. Enfin, chez des animaux âgés de 1–2 semaines, on a isolé l'agent moins souvent que chez des porcs plus âgés. Resumen Sobre la presencia de Mycoplasma hyorhinis en los órganos respiratorios de cerdos bajo la consideración especial de la neumonía enzoótica Se examinaron en cultivos los pulmones y la mucosa nasal de 525 lechones en cuanto a la presencia de M. hyorhinis, comparándose los resultados con los hallazgos histopatológicos. M. hyorhinis se aisló con bastante mayo...

Using a radioimmunoassay ( R I A ) we detected antibodies against one of the major group specific (gs) antigens of avian R N A tumor viruses in chickens with a naturally acquired leukosis virus infection or bearing Rous sarcoma virus ( R S V ) -