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Summary Clinical signs, local changes, excretion of virus, interferon (IF) production and production of serum and secretory antibodies were followed in calves vaccinated intranasally by a strain of IBR virus attenuated by us (IBR‐BNZ/150), in comparison with two vaccination strains from other sources (IBR‐C and IBR‐R), after infection and reinfection by virulent IBR virus. The IF content in nasal secretions was proportional to the intensity of replication of attenuated viruses on the mucous membranes of the upper respiratory tract and the virus excretion lasted longer than the period of IF detection. Secretory antibodies were found irregularly and at low titres after 28 days, whereas humoral antibodies were detected in all calves within 14 days after vaccination. After challenge, the vaccinated calves were protected against clinical disease but not against infection. The virus titres were, however, lower in vaccinated calves and the period of virus excretion was shorter than in infected control calves, which agrees with the lower IF content in nasal secretions. All infected calves produced secretory antibodies and the serum antibodies increased rapidly. The second intranasal infection gave no or very little virus on the nasal mucous membranes and did not stimulate the production of a detectable amount of IF or an increase in secretory antibodies, but a slight increase in serum antibodies. The role of different immune mechanisms in the resistance of mucous membranes against infection by the IBR virus is discussed. Zusammenfassung Immunisierung von Kälbern gegen experimentelle Infektionen durch intranasale Vakzinierung mit drei attenuierten IBR‐Virusstämmen Klinische Veränderungen, lokale Läsionen, Virusausscheidung, Interfe‐ronproduktion sowie die Bildung humoraler und sekretorischer Antikörper wurden bei Kälbern nach intranasaler Vakzination mit einem von uns attenuierten IBR‐Virusstamm (IBR‐BNZ/150) im Vergleich mit zwei ausländischen Impfstämmen (IBR‐C; IBR‐R) und nach Infektion bzw. Reinfektion mit vurlentem IBR‐Virus verfolgt. Der Interferongehalt im Nasensekret war der Vermehrungsintensität der attenuierten Virusstämme in der Schleimhaut des oberen Respirationstraktes direkt proportional. Die Virusausscheidung dauerte jedoch länger als Interferon nachgewiesen werden konnte. Sekretorische Antikörper wurden zu unterschiedlichen Zeiten bis zum 28. Tag nachgewiesen. Die Titer waren niedrig. Humorale Antikörper traten bei allen Kälbern 14 Tage nach der Vakzination auf. Nach der Testinfektion waren alle vakzinierten Kälber gegen klinische Erkrankung geschützt, jedoch nicht gegen eine Infektion. Die Virusausscheidung war bei geimpften Kälbern geringer und kürzer im Vergleich zu infizierten Kontrolltieren. Diese Befunde stehen im Einklang mit der niedrigen Interferonproduktion. Alle infizierten Kälber produzierten sekretorische Antikörper und Serumantikörpertiter stiegen rasch an. Erneute intranasale Infektionen, bei denen sich wenig oder kein Virus in der Nasenschleimhaut vermehrte, stimulierten die Interferonprodu...

Methods used in Aujeszky's disease (AD) control depend on the stage of its extension, the economic losses caused and the methods of management. Serological control and corresponding elimination measures are sufficient in the case of sporadic infection, but where infection is enzootic in an area and endemic infection exists on pig farms with large scale production one must apply methods of specific prophylaxis. For this purpose live vaccines have been used in the countries of middle and east Europe for two decades (2, 3, 4, 8, 11, 22,37). Attempts to eliminate the shortcomings resulting from the use of live vaccines and inactivated vaccines against AD have made it possible to provide the vaccinated pigs with a good protection against natural as well as experimental infections (5, 7, 14,29). Immunity stimulated by vaccination with live and inactivated vaccines does not preventin the case of contact with infectioncolonization of mucous membranes of the respiratory tract and virus excretion (6, 9, 10, 12, 18,30).In our laboratory, besides the derivation of several lines from the Bucarest strain, known to have differing residual virulence and used for preparation of live vaccines for various species of animals (31, 36), an inactivated vaccine with an oil adjuvant has been prepared and found to possess a good immunizing effect (38). The aim of the experiments discussed in this paper was to find whether there are differences in the clinical and biological protection of pigs vaccinated by live and inactivated vaccines and thus in the efficiency of the immunity stimulated by the two types of preparations to eliminate the virulent virus from the population of vaccinated pigs. Material and MethodsVaccines. Live lyophilized SUIVAK vaccine from the Buk-TK/650 strain was used (33). After rehydration in an equivalent volume of a solvent, 2 ml. were applied s. c., which re-U.S.

Kate Cernik explores the new opportunities that are opening up to nurses to set up as alternative providers of primary care services, using their experience and expanding their skills

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