Abstract
Bovine viral diarrhea (BVD) is one of the most important infectious diseases in cattle, causing major economic losses worldwide. Therefore, control programs have been implemented in several countries. In Germany, an obligatory nationwide eradication program has been in force since 2011. Its centerpiece is the detection of animals persistently infected (PI) with BVD virus, primarily based on the testing of ear tissue samples of all newborn calves for viral genome or antigen, and their removal from the cattle population. More than 48,000 PI animals have so far been detected and removed. Between the onset of the program and the end of 2016, the prevalence of these animals among all newborn calves decreased considerably, from 0.5% to less than 0.03%. The number of cattle holdings with PI animals likewise decreased from 3.44% in 2011 to only 0.16% in 2016. Since a large number of naïve, fully susceptible animals are now confronted with BVD virus, which is still present in the German cattle population, the challenge of the coming years will be the identification of remaining PI animals as quickly and efficiently as possible, and the efficient protection of BVD-free farms from reinfection.
Highlights
Bovine viral diarrhea (BVD) is endemic in cattle populations worldwide, and causes major economic losses and significant impact on animal welfare [1,2,3]
Severe acute forms of BVD occur, which are characterized by hemorrhagic syndromes and mucosal disease-like lesions, and are mainly associated with virulent BVDV-2 strains [6]
The inevitably fatal mucosal disease (MD), which develops only in persistently infected (PI) cattle, is associated with the superinfection of the PI animal with a cp-strain that is antigenically homologous to the persisting ncp-strain. Another possibility is the appearance of a cp-biotype arising from mutations of the ncp-BVDV already circulating in the animal [10]
Summary
Bovine viral diarrhea (BVD) is endemic in cattle populations worldwide, and causes major economic losses and significant impact on animal welfare [1,2,3]. Another possibility is the appearance of a cp-biotype arising from mutations of the ncp-BVDV already circulating in the animal [10] Clinical signs of this late-onset form of BVD include severe and bloody diarrhea, mucosal lesions, and rapid wasting [10,11]. Due to their major importance in intra- and inter-herd virus spread, PI animals are the main target of all efforts to reduce clinical diseases and BVD-induced economic losses. An alternative approach to BVD control, which proved beneficial especially for countries with a high initial BVDV prevalence and a high level of cattle trading and transport combined with ongoing vaccination campaigns, was based on the direct antigen or viral genome testing of all animals without serological pre-screening. In 2012, the country implemented an eradication program on a voluntary basis, followed in 2013 by an obligatory program focusing on the testing of ear notch samples of all newborn calves [18,19]
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