Bovine Viral Diarrhea (BVD)
BVD or Bovine Virus Diarrhea is an infection that can cause numerous problems in cattle, including damage to the digestive and immune systems and birth defects. BVD can cause high mortality in calves and yearling cattle. The outbreak of this disease has devastating economic consequences to cattle producers. One survey showed that BVD causes estimated losses of up to $150 million annually.
In 1946 Olafson and associates discovered gastroenteritis with severe diarrhea in dairy herds in the state of New York. These were the first reported cases of Bovine Virus Diarrhea. The animals were also said to be infected with ulcers in the nasal and oral soft tissue layers. There is no common name for BVD.
BVD virus or BVDV is the causative organism of the disease. During the 1970s, it was learned that bovine viral diarrhea virus (BVDV) was closely related to the hog cholera virus. Today the BVDV has been successful in infecting cattle of all ages. This has made a major financial blow due to productive and reproductive losses.
- Calves born with BVD show fever
- They have a continuous nasal discharge
- The calves often have a fever and become dehydrated as well
- Diarrhea is also a definite symptom
- The affected calves as well as adults lose the ability to move about normally
- Animals often die of pneumonia due to a weakened immune system
- There are ulcers on the hoofs of the affected cattle
How it Affects Cattle
Following acute infection of BVD, suffering is mild. The risks are actually from secondary and opportunistic infections. As the disease weakens the system, many secondary infections attack the cattle. BVDV acts as an immunosuppressant (makes the body immune system non-functional) and allows bacterial infections to occur. Acute infections with BVDV are dangerous in pregnant cattle because the virus can cross the placenta and cause infections of the fetus. Fetal infections can result in early embryonic death, abortion, defects from the birth, or the birth of calves chronically infected with BVDV. The BVD virus is not capable of long-term survival in the environment.
The BVD virus is widespread in western Canada and throughout the world. A study in Alberta confirmed that 41% of beef cattle contain antibodies to BVD virus.
Risks & Dangers
Infected animals can shed the virus from discharges of the mouth, nose, eyes or in the milk. The highest virus concentrations are found in the manure of infected animals with diarrhea. Many infected bulls also carry the virus in their semen. Infection in a pregnant cow may spread to the fetus, which can cause a number of different conditions depending on the age of the fetus.
Unfortunately there are no specific treatments available for any of the forms of BVD infection. All prenatally infected cattle will slowly die from the mucosal disease, but animals that are infected after birth may survive. Antibiotics may help prevent secondary infections.
Vaccines & Prevention
Natural exposure or vaccination can be useful. BVD vaccines are obtainable either as modified live vaccines or as killed vaccines. Please note that critical reactions commonly follow the use of modified live virus BVD vaccines. Your local veterinarian must be consulted before undertaking any vaccination or control program.
References and Resources
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