Bovine Viral Diarrhea Mucosal Disease
Die Krankheit ist weltweit verbreitet
The majority of infections with BVD viruses are asymptomatic. Possible symptoms are diarrhea, fever, respiratory diseases, mucosal erosions, feeding instability, reduced milk yield, and fertility problems. Pregnant animals may reject, give birth to malformed or weak calves. Mucosal disease, which is fatal, occurs as a special disease variant.
Situation in Austria
The successful and continuously positive development of BVD control (in 2006 - thus two years after the start of nationwide control - for example, 2,600 PI animals were still detected in approx. 1,700 farms) can be seen in the past years: Austria's farms subject to the BVD Ordinance were almost completely officially recognized as BVD-free, and no new outbreaks occurred in recent years.
Bovine Viral Diarrhea/Mucosal Disease is one of the most economically important infectious diseases of cattle worldwide. Many countries have adopted active control and surveillance programs for BVD/MD. The disease is caused by a pestivirus, family Flaviviridae, and has a worldwide distribution. 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. The emergence of a PI animal occurs through 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 occurs through all body secretions and excretions.
The majority of BVD virus (BVDV) infections are asymptomatic. Possible symptoms include diarrhea, fever, respiratory disease, mucosal erosions, feeding instability, reduced milk yield, and fertility problems. Pregnant animals may reject, 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 disease and is fatal. Symptoms of MD include bloody diarrhea, high fever, mucosal erosions, and ulceration (at the potty mouth, nose, interclaw cleft).
To control BVD, virus excretors (PI animals) present in the herd are eliminated to protect the herd from reinfection.
Antibody detection: Infection with BVDV leads to the formation of antibodies (detectable in serum, individual and tank milk).
Antigen detection: direct pathogen detection (serological and molecular biological methods from blood, tissue, secretion and organ samples)
Detectionin ear tissue samples: In spring 2005, an innovative and efficient control program for the detection of PI animals was introduced in Tyrol. For the first time, testing of ear tissue samples for antigen detection was performed in all newborn calves nationwide. In 2008, the system was improved with the aim of already taking an ear tissue sample during the legally required animal identification with the same work step (confusion-proof sampling procedure!).
One of the most important goals in BVD diagnostics is the timely detection of a PI animal. Maternal antibodies (antibodies passed from the mother to young animals via colostrum) can mask BVDV in the blood, making early detection impossible. This so-called "diagnostic gap" does not play a role in the examination of tissue samples, and detection and eradication of PI animals is possible as early as the first week of life. Equally problematic is the delayed rise of antibodies after BVD infection. BVD antibodies are not detectable until approximately day 7 after infection. This time delay is even greater when tank milk is tested.
Institut für veterinärmedizinische Untersuchungen Mödling
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Robert Koch-Gasse 17
Last updated: 15.09.2022