Atsfrnct: Leptospirosis i~ man and animals has been studied in Denmark since 1934. Strains of the following ten serotypes have been isolated: ic~erolrrrettrorrI~(~~iae, poi, catricolu, ~c / / N I ? I , brarisla~~a, pottrotlo, ~ripporyplrosa, sejrue, sn.rkoehitlg, and hara\,iae. Twenty-eight of the 44 species of wild land manimals living in Denmark have been examined culturally. Leptospires of eight serotypes were isolated from 14 species. Leptospires were demonstrated microscopically in the urine and/or kidneys of 31 bats belonging to fcur species. Ttese leptospires could not be cultured it1 vitro or transmitted to animals other than bats. Serological evidence of present or past leptospirosis was found in four species of I.ct~ortrorplra. Cart~i\*ora and U t~g~r l a t a not examined culturally.Our findings indicate that the following species are maintaining hosts for leptospires of identified serotypes in Denmark: Sorex aratreus ( p o i ) , Erinaceus etrropaeus (bratislava ), Microrus arvalis (grippotyphosa), Rarrus t~o r~* e~i c t r s (icterohaemorrhagiae), Mlrs t~~uscctlus (sejroe), Apodettrlts u~r a r i u s (pomona), and Apodetrius f1at.icollis (saxkoebing). M u s tt~rtsc.rrlus is probably also a maintenance host for leptospires of the ballutl~ serotype. Three bat species, Myoris datch~trrotrii, Pipisrrellus pipistrellus, and Npcralus t~ocrrrla, with a high carrier rate ( 15-20% ), may be maintenance hosts for unknown serotypes of a unique group of leptospires. Batu~.icre and catlicola leptospires have not yet been isolated from wild animals in Denmark.The significance of leptospirosis in wild mammals for the epidemiology of leptospirosis in man and domestic animals is discussed.
A pathogenetic study of pleural effusion disease (PED) in rabbits was made, using the virulent PED agent or virus (PEDV) and an avirulent derivate of this isolate. Independent of infective dose within the range examined, the virulent isolate caused fatal clinical disease, whereas the avirulent isolate caused subclinical infection. The two isolates differed in rapidity of initial spread of infection and in the maximum virus titres in serum, but they both resulted in a similar low level persisting viraemia. Circulating virulent virus gradually became avirulent during the viraemia. Avirulent infection induced protective immunity to virulent challenge during the first week after primary infection, but full clinical protection was not established until after the fourth week. The findings, corrobated with other closely comparable observations, suggest that the emergence of PED as an intercurrent mortality problem during rabbit passage of pathogenic Treponema pallidum is the result of a specific selective pressure on a benign passenger virus. The expression of virulence of PEDV appears to be dependent on length of interval between passages.
The size and heat sensitivity of Pleural effusion disease (PED) agent or virus (PEDV) propagated in rabbits were examined. The infectious particles were estimated to be between 25 and 50 nm by filtration. Residual infectivity of infectious serum was 0.1 per cent after heating at 56 degrees C for 4 hours. PEDV and the Stockholm agent appeared identical concerning pathogenic and immunogenic properties by infection experiments and protection tests in rabbits. Two of the three PEDV isolates were less pathogenic but appeared immunogenically identical to PEDV. The third isolate, obtained from the laboratory, which several years previously had supplied material for demonstration of the Stockholm agent, differed from PEDV in pathogenic and immunogenic properties. Serological examinations of paired rabbit sera did not indicate any antigenic relationship between PEDV and representative members of the two mammalian coronavirus antigenic groups. It is concluded that the aetiological agent of PED is a virus not belonging to the coronaviridae.
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