Epidemiology and Pathogenesis of the
Bovine herpesvirus 2 Infection
Clinical disease in response to initial formation of antibody
Published 2011 ISBN 978-87-994685-0-8
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Bovine herpesvirus 2 (BoHV2) is spread among cattle by the respiratory route. There are no indications whatsoever of a transmission by insects or milking machines.
If disease occurs, it appears clinically in two different forms as either pseudo-lumpy skin disease (PLSD) or bovine herpes mammillitis (BHM), but no differences in pathogenicity of virus strains from PLSD and BHM outbreaks have been found. Both manifestations were recorded in Africa, before the infection was diagnosed in Europe, where it has appeared almost exclusively as BHM. Here, the infection was probably first spread to herds in a region with semen from artificial insemination centres. Later, spread between herds with both acutely and latently infected animals occurred.
PLSD will be explained as the outcome of a generalized infection, where skin lesions appear as the result of an inflammation process at sites of virus propagation caused by complement activation, which again is triggered by the action of specific antibody to BoHV2 (complement activation by the classical pathway). This implies that lesions do not appear, until antibody has been produced.
Naturally occurring clinical cases of BHM have regularly been found antibody-positive in the very early stage of disease when examined by a test of acceptable sensitivity. BHM lesions are accordingly also explained as the outcome of a generalized infection, where inflammatory lesions appear late in the course of the infection at sites of virus propagation immediately after the initial formation of specific antibody. Complement activation by the classical pathwayl explains the sudden appearance of multiple lesions characteristic of PLSD - as well as of BHM, when several lesions develop.
Tissue damage caused by the inflammatory reactions appears to be aggravated by - or even dependent on - low skin temperature and the associated reduced blood circulation hampering removal of cell-toxic inflammatory substances (and additionally in some cases of BHM probably also by a traumatic influence of milking machines) during the first short period after complement activation. This may explain (1) why udder lesions have developed especially in animals with udder oedema, (2) why clinical outbreaks in Europe have been seen predominantly in the autumn, when the cows were still at pasture during the daytime, and (3) why no skin reactions are observed in most cases of natural infection.
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Principal Epidemiological Features of
Infection in Swine and Cattle
Genital infection in swine was common in Europe in the 20th century.
Published 2015 ISBN 978-87-994685-1-5
Aujeszky's disease – infection with Suid herpesvirus 1 (SuHV1) – is an infection of pigs, which under certain conditions can be spread to several other animal species, usually with a fatal outcome. It has been found world-wide, but has now been eradicated in a number of countries. Denmark is the country, where Aujeszky's disease has been studied most intensively, and the results from investigations of cattle have been of greatest importance for the understanding of the epidemiology of the infection in swine. Denmark was also the first country to initiate eradication and the first to complete eradication of the indigenous infection. In this review, important features are recapitulated at the end of each section or subsection.
The special manifestation of Aujeszky's disease in cattle showing pruritus on the hindquarters was regularly associated with use of a boar from a boar centre for natural service of a sow shortly before appearance of the clinical disease. In most cases examined, virus was found in the vagina of the affected bovine animals, although at low titres, and in three outbreaks – the only cases investigated early enough to be successful - virus was demonstrated in the vagina of a sow. It was found that animal sodomy most likely played a role in the transmission of the genital infection from swine to cattle, and this conclusion is further substantiated by comprehensive supplementary information given in this review article. From the fact that genital infection in cattle is closely correlated with contemporary genital infection in swine on the same premises and from the many reports over the years on infection in cattle showing pruritus on the hindquarters, it can additionally be concluded that the SuHV1 infection in a great part of the 20th century was maintained as a porcine genital infection in many countries.