Bovine Viral Diarrhoea/Mucosal Disease is one of the most economically important infectious diseases of cattle worldwide. Many countries have opted for active control and surveillance programmes of BVD/MD. The disease is caused by a pestivirus, family Flaviviridae, and is distributed worldwide. Host animals are cattle, sheep, goats and wild ruminants.
The route of transmission of BVD is mainly through persistently (permanently) infected animals (PI animals). They are the main source of virus spread. A PI animal develops by infection of the unborn calf via the dam between the 40th and 120th day of gestation. At this time, the immune system of the fetus is not fully developed, immune tolerance to the virus develops, and the animals remain infected throughout their lives and excrete the virus. Excretion takes place via all bodily excretions and secretions.
The majority of infections with BVD virus (BVDV) are asymptomatic. Possible symptoms are diarrhoea, fever, respiratory diseases, erosions of the mucous membranes, feeding instability, reduced milk yield, fertility problems. Pregnant animals can give birth to malformed or weak calves.
Mucosal disease (MD) occurs as a special disease variant. It occurs when a PI animal is additionally infected with another strain of the virus. MD is characterized by a severe course of the disease and is fatal. Symptoms of MD are bloody diarrhoea, high fever, erosions of the mucous membranes and ulcerations (on the muzzle, nose, interclaws).
To control BVD, virus excretors (PI animals) present in the herd are eliminated to protect the herd from reinfection.Phylogenetic analyses of the virus strains can provide valuable information on infection routes for epidemiological questions. Pathogen analyses are extremely useful in tracing sources of infection. In order to obtain data on circulating BVDV and BDV (Border Disease Virus) strains in Western Austria in 2005 and 2006, a comprehensive study was carried out by AGES (Hornberg, A.; Revilla-Fernández, S.; Vogl, C.; Vilcek, St.; Matt, M.; Fink, M.; Köfer, J.; Schöpf, K. (2008): Genetic diversity of pestivirus isolates in cattle from Western Austria. Vet Microbiol. 2009 Mar 30;135(3-4):205-13). The study carried out in the veterinary institutes of Mödling and Innsbruck was based on the genetic heterogeneity of BVDV strains. This was determined by molecular biological sequence analysis. The typing of the samples showed a very high genetic variability of the BVDV strains circulating in Tyrol and Vorarlberg. A total of 8 different BVDV-1 subtypes were found, 3 of which were isolated for the first time in Austria. The BVDV-1h subtype occurred most frequently (143 isolates), but subtype 1f (79 isolates) was also widespread. In addition, two BVDV-2 strains and, for the first time, a BDV isolate in cattle could be classified. On farm level, only a low geographical correlation in the occurrence of the different strains could be found.
BVD in red deer
Cattle and red deer(Cervus elaphus) can come into direct or indirect contact with each other on pastures or mountain pastures, so that pathogen transmission between these two animal species becomes possible. In several European countries, as well as in the USA, evidence of pestivirus transmission between cattle and wild ruminants has been found.In the course of a study at the Institute for Veterinary Investigations of the AGES in Innsbruck, the occurrence of BVDV in the Austrian red deer population was determined by means of virus detection from ear tissue samples. Between 2007 and 2009, as part of an officially ordered monitoring programme for chronic wasting disease in Austrian red deer, a total of 567 animals from the wild and 133 from cages were examined not only for brain samples but also for one ear tissue sample per animal from the ears sent in. In the laboratory, the ear tissue samples were tested for BVDV using HerdCheck BVDV antigen ELISA and commercial real-time RT-PCR. No BVDV was detected in all 700 tissue samples tested by ELISA and real-time RT-PCR.Recent literature from AustriaSchöpf, Karl; Revilla-Fernández, Sandra; Steinrigl, Adolf; Fuchs, Reinhard; Sailer, Andreas; Weikel, Joachim; Schmoll, Friedrich (2016): Retrospective epidemiological evaluation of molecular and animal husbandry data within the Bovine Viral Diarrhoea (BVDV) control programme in Western Austria during 2009-2014. Berl Münch Tierärztl Wochenschr 129:196-201. doi 10.2376/0005-9366-129-15102, http://vetline.de/open-access/158/3216/)