BVD MDC

• Bovine viral diarrhea and mucosal disease complex (BVD/MD) is caused by the bovine viral diarrhea virus (BVDV), which belongs to the genus Pestivirus in the family Flaviviridae.
• BVDV is a single-stranded RNA virus with two major genotypes, BVDV-1 and BVDV-2, and several subtypes within each genotype.
• Both genotypes of BVDV can cause BVD/MD, but BVDV-1 is generally associated with more severe clinical signs.
• There are two main types of BVDV: Cytopathic (cp) and Non-cytopathic (ncp).
• Cytopathic BVDVs are directly destructive to cells, causing acute clinical signs like fever, diarrhea, and respiratory illness.
• Non-cytopathic BVDVs persist in the animal without causing immediate clinical signs, but they can still cause reproductive problems and immunosuppression.
• BVDV is highly contagious and can spread through various routes, including: Direct contact, Indirect contact, and Vertically.
• Inactivated and modified-live virus vaccines are available, containing a variety of strains of BVDV representing both viral biotypes and viral genotypes 1 and 2.
• Because BVDV is fetotropic and immunosuppressive, use of modified-live virus vaccines is not recommended in cattle that are pregnant or showing signs of disease.
• Artificial insemination should be done only with semen obtained from bulls free of persistent infection.
• Replacement cattle should be tested for persistent infection, quarantined or physically separated for 2-4 weeks, and vaccinated for BVD before entry into the herd.
• Proper and safe immunization of cattle with either inactivated or modified-live virus vaccines requires adherence to the manufacturer’s instructions.
• Embryo donors and recipients should also be tested for persistent infection.
• Because BVDV is shed into semen, breeding bulls should be tested for persistent infection before use.
• Inactivated viral vaccines may be used in pregnant cattle, but protection conferred by inactivated vaccines may be of short duration, and frequent vaccination may be necessary to prevent disease or reproductive failure.
• BVDV enters cells through receptor-mediated endocytosis and replicates its RNA and produces new viral particles.
• BVDV suppresses the animal's immune system, making them more susceptible to other infections.
• Clinical signs of BVD/MD vary depending on the type of BVDV and the individual animal.
• Common signs of BVD/MD include fever, diarrhea, respiratory illness, weight loss, reproductive problems, and congenital abnormalities in calves born to infected dams.
• PI calves are often weak, stunted, and susceptible to other diseases.
• BVD/MD is a significant economic burden for the cattle industry, causing losses due to decreased milk production, reduced weight gain, increased calf mortality, and reproductive problems.
• Vaccination is one of the most effective ways to control BVD/MD.
• Biosecurity measures, such as isolating infected animals and implementing proper hygiene and sanitation practices, are also important for preventing the spread of the disease.
• Disease induced by bovine viral diarrhea virus varies in severity, duration, and organ systems involved.
• Clinical signs of acute MD include fever, leukopenia, dysenteric diarrhea, inappetence, dehydration, erosive lesions of the nares and mouth, and death within a few days of onset.
• Laboratory support also is required in some outbreaks of MD or clinically severe acute BVD, because either disease may appear similar to rinderpest or malignant catarrhal fever.
• Some isolates of BVDV (BVD type 2) have been associated with severe clinical disease that manifests as oral ulcerations, eruptive lesions of the coronary band and interdigital cleft, dehydration, leukopenia, thrombocytopenia, petechial hemorrhages (seen in thrombocytopenic cattle), and prolonged bleeding from injection sites.
• Bovine viral diarrhea is diagnosed tentatively from disease history of the herd, clinical signs, and gross and microscopic lesions.
• Acute clinical disease may range from mild disease of high morbidity and low mortality to severe enteric disease with considerable mortality.
• Clinical signs of chronic MD may last several weeks to months and are less severe than those of acute MD.
• Intermittent diarrhea and gradual wasting are common in chronic MD.
• Diagnostic laboratory support is required when clinical signs and gross lesions are minimal.
• Laboratory tests for BVDV include isolation of virus or viral antigen in clinical specimens and tissues, and assays that detect anti-BVDV antibodies in serum or milk.
• Treatment for BVD/MD is primarily supportive, with no specific antiviral therapy available.
• Clinical signs of disease usually are seen 6–12 days after infection and last 1–3 days.
• Coronitis (inflammation of the coronary band) and eruptive lesions on the skin of the interdigital cleft cause lameness in some cattle in chronic MD.
• Inapparent or subclinical infection without any clinical signs that is followed by seroconversion is the most common form of infection in the field.
• Control of BVD/MD is based on sound management practices that include use of biosecurity measures, elimination of persistently infected cattle, and vaccination.
• Alternatives to viral isolation include antigen-capture ELISA to detect virus in blood, serum, or tissue biopsies; immunohistochemistry to detect viral protein in frozen or fixed tissues; PCR to detect viral RNA in clinical specimens; and PCR or in situ hybridization to detect viral RNA in fresh or fixed tissues.
• Early detection and diagnosis of BVD/MD are crucial for preventing economic losses and protecting animal health.