Bovine virus diarrhea

Bovine viral diarrhea / mucosal disease, short BVD / MD ( caused by the bovine viral diarrhea virus, BVDV ) is a fairly common viral disease complex of cattle, which due to its epidemiology ( both " hit and run " and " infect and persist " ) plays a special role. The infection is often cyclically within a portfolio. The viral diarrhea virus was first described in 1946, the Mucosal disease found in 1953 in the literature mention. The common cause was demonstrated in 1959. The disease complex is spread worldwide.

Molding

The virus can cause several symptoms which vary greatly in morbidity and mortality from each other. In the particularly vulnerable group of persistently infected ( or PI ) animals are both 100 percent.

Bovine viral diarrhea

Bovine viral diarrhea, short BVD is a viral infection of cattle caused by a pestivirus of the family Flaviviridae. The BVD occurs worldwide and is one of the most economically important diseases of cattle. The disease is extremely diverse.

Mucosal Disease

The mucosal disease, short MD, is an always fatal disease of mostly young cattle ( 3-24 months), which is characterized by erosions on all mucous membranes ( see picture). Noteworthy is the absence of an immune response despite the presence of viral cytopathic form.

Fertility problems

If the infection in an animal in the first or last trimester of pregnancy, it can cause severe birth defects or abortion of the fruit. Infections with cytopathic form in the second trimester of pregnancy usually leads to abortion or mummification.

Epizootiology

Infection occurs either horizontally (ie, from another animal ) or vertically (ie, in utero, even during pregnancy from mother to the unborn calf ).

At a horizontal infection, the animal develops after infection with cytopathic or non- cytopathic BVDV symptoms of AAD eliminated the virus in a normal immune reaction to the formation of antibodies and maintains a permanent immunity ( "hit -and-run " strategy ).

The vertical infection can occur if the mother is infected in the second trimester of pregnancy with the non- cytopathic BVDV. The virus is transferred to the fetus in this case. Since this is in the phase of immune tolerance, does not recognize his immune system the virus as a foreign antigen. It therefore does not form antibodies and the young animal remains infected with the virus for life and separates this from permanent, but without showing any symptoms themselves. Such PI animals (PI infected = persistent ) form a reservoir of virus ( " infect -and -persist Strategy" ) within the population.

The introduction into a cattle herd can be done in different ways. They often done by setting of persistently infected animals. Also infections in grazing ( transhumance common erstträchtiger cattle! ), At exhibitions and animal markets come into question. A further risk poor hygienic precautions dar. Here come as disease vectors contaminated transport vehicles, equipment, clothing and animal feed in question. The risk of transmission by biting insects or pests such as rats and mice and transmission through the air, however, seems to be low.

From the PI animal to MD victims

The BVDV comes as already mentioned before in a cytopathic and noncytopathic form, which are caused by mutation of a virus gene. Mutated in a PI animal now a virus from noncytopathic to cytopathic form, it multiplies in the mucous membranes and damages them, which leads to the typical erosions of the MD. Since the immune system does not recognize the virus as foreign, an immune response remains, so that the disease is always fatal.

Tests

After the PI animals are the source of infection, they must be identified and eliminated. For clear identification of the status of an animal but both virus detection and antibody detection is necessary. The following results are possible:

• Antibodies and virus negative: Healthy animals; never had contact with the virus. Can not be a mother of a PI animal.

• Antibody positive, virus negative: Healthy animals; BVD has been through. Calves can be PI animals!

• Antibody positive, virus negative: in calves: can a PI animal in the gap colostral ( maternal antibodies of the mother mask the virus, so the blood test, the virus is detectable only in older animals! ) To be!

• Antibodies and virus positive: At BVD infected animal, which is going through the acute infection. Will be healthy; if pregnant, there is a danger of a PI calf.

• Antibody negative, positive virus: PI animal. Source of infection for other animals; is likely to eventually suffer from MD or already sick of it. All descendants are also PI animals.

For the detection of BVDV in a herd in addition to the blood test, a serological examination of milk is possible.

Particular importance in the Federal Republic of Germany of virological investigation of ear punch samples taken in the framework of the official identification of newborn calves, too. This is generally done by PCR.

Combat

The combat is based on two pillars:

• Identification and elimination of PI animals
• Prevention of re-infection of pregnant animals

There is a vaccination against the virus, but of course has no effect on PI animals. Moreover, in the application, the vaccination no longer be safely distinguish between infected and non- infected herds.

In Switzerland, currently runs a nationally coordinated eradication program that should be completed according to plan in October 2009

In North Rhine -Westphalia there since October 1, 2009, a voluntary control methods. The aim is to give as many stocks the status of " BVD unsuspecting inventory ". Since January 1, 2011 in the Federal Republic of Germany applies a restoration obligation. The legal basis for this is the BVDV - regulation.

Economic Importance

BVD -MD is an important economic factor that can significantly reduce the productivity of a herd of cattle. Particularly problematic is the common position of the trächigen cattle on the pasture (mountain pasture ), the resulting high probability of coming into contact with the virus become infected and give birth in the sequence PI animals.