F.A.Q. about BVD

 

Q. What is BvDv?
A. Bovine Viral Diarrhoea Virus (BvDv) is a small enveloped RNA virus belonging to the genus Pestivirus. It was first discovered in New York in 1946 and today still continues to cause severe economic losses to the dairy and beef industries world wide. The main effects of this infectious agent are scouring, infertility, abortions, reduced growth and illness associated with immune-suppression. It is primarily an animal spread infection with the main source of the virus being a persistently infected (PI) animal. There are two types of BvDv infection; persistently infected (PI) and transiently infected (TI) A PI animal is created when their dam is infected with the virus during gestation, especially in the first trimester of pregnancy. PI animals continually shed the highly contagious virus from all secretions throughout its entire life. This is the main way BvDv is spread and perpetuated in a herd. A TI animal is usually infected by a PI animal. It sheds the virus for two to three weeks before developing immunity and recovering.

 

Q. What clinical signs would I expect if I had BVDV present on my farm?
A. The principal loss from BvDv relates to pregnancy loss. This results from infection in early pregnancy resulting in either early embryonic death (miscarriage and a cow returning to service) or the birth of a persistently infected animal, which infects other animals in the herd. Other pregnancy related losses include sporadic abortions, birth deformities, stillbirths and the birth of weak calves. Other signs which are often evident on
BvDv infected farms include a suppression of herd immunity. When herd immunity is weakened animals don’t thrive and routine illnesses, such as pneumonia, scour or mastitis, are now more severe and end in higher than expected mortality.

 

Q. What types of Infection are there?
A. BvDv virus spreads by two methods (i) direct transmission between animals through physical contact and, (ii) virus invading the foetus in a pregnant cow. If a cow is infected from 1 to 4 months of pregnancy and the calf survives there is a strong chance that the calf will be born persistently infected (PI) with the virus (a carrier animal). These PI animals are essentially a virus factory and will be shedding large amounts of virus in all body fluids. PI animals are much more efficient at spreading the virus than cattle that are transiently infected (TI). PI animals represent about 1% of the cattle population. A lot will be poorly grown and stunted; others will be perfectly normal. Many die before they are born. Luckily, the virus only survives for a short time in the environment no more than 3-4 days

 

Q. How does BVDV enter a herd?
A. The principal source of BvDv is a persistently infected animal. This animal was caused by infection of the foetus before the fifth month of pregnancy, which results in the virus becoming ”part of” the foetus and often the birth of a normal animal. Infected animals may spread the virus in nasal discharge, saliva, faeces, urine, semen and saliva. These PI animals shed BVD virus from body secretions throughout their life. Other possible sources include the purchase of a pregnant animal containing a persistently infected foetus inside, while less commonly contaminated needles & equipment are potential sources. Saliva from a persistently infected or recently infected animal contains the highest quantity of the virus.

 

Q. What is mucosal Disease?
A. Mucosal disease is one of the diseases that may be triggered by BvDv. PI animals inevitable develop mucosal disease. The clinical signs of muscosal disease are similar to but even more severe than those associated with the chronic form of BVDV. Animals infected often have bloody diarrhea, a high temperature and mucosal lesions in the mouth as well as ulcerations at the muzzle, the nose, the rim of the hoof and in the interdigital clef and secondary bacterial infections such as pneumonia, mastitis, and metritis. There is little chance of survival for these animals.

 

Q. Do PI animals remain in herds for a long time?
A. Most PI animals life expectancy is reduced and therefore do not survive beyond two years of age. However, new PI animals are constantly developing as a result of fetal exposure to BVDV.

 

Q. How can BVDV be controlled?
A. There is a considerable interest in strategies for BvDv monitoring, and indeed several EU countries have already started control & eradication programs. Good diagnostic tests exist to detect carrier PIs, and also to determine the immune status of your herd.
Persistently infected (PI) cattle represent the principle reservoir of infection. Identification and removal of PI cattle are critical to the control of BvDv. Identifying all (PI) carriers in a herd by blood testing and culling them to get a clean herd is straightforward.
The big concern is keeping the herd a clean afterwards. Bio-security is the big issue and a well thought out bio-security plan needs to be implemented to minimise the risk of reintroducing the virus. Control options include Eradication and Biosecurity, Vaccination, Eradication and vaccination. It is important to remove aborted fetuses and placentas as they may serve as a source of virus when licked or eaten by other cattle. BvDv is a very complex disease and it is essential that you contact your veterinarian for more information and the development of a suitable control programme for your farm.

 

Q. What are the human health implications?
A. There are no human health implications from BvDv. The virus is not a zoonosis and does not present a risk to humans.
For more information please go to http://www.animalhealthireland.ie/page.php?id=115

 

Disclaimer:
The test methods used will, in the great majority of cases, accurately detect the presence or absence of virus or antibody (as per test design) in tissue and blood samples when submitted and tested correctly. However, results relate only to the sample as received by the laboratory and Enfer accepts no liability for the traceability or quality of samples prior to receipt by the laboratory, either of which may compromise the quality of test results generated and whilst Enfer warrant that our tests will meet  the applicable declared specifications, Enfer makes no other warranty, expressed or implied and accept no responsibility or liability in respect of false results which are within the limits of the declared specifications of the tests offered or for the consequences of any actions taken on the basis of the information provided. No representation or warranty is given by Enfer Labs, or any member or employee or other person connected with Enfer as to the accuracy of any test method or test results.
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