Bovine leukemia virus

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Bovine leukemia virus particles under electron microscopy

The Bovine Leukemia Virus (BLV) is a retrovirus that infects cattle, leading to a condition known as enzootic bovine leukosis. This virus is a member of the Deltaretrovirus genus, which also includes the Human T-lymphotropic virus. BLV primarily affects the immune system of cattle, leading to the proliferation of B lymphocytes.

Transmission

BLV is primarily transmitted through the transfer of infected blood and other bodily fluids. Common routes of transmission include:

• Vertical transmission from dam to calf, either in utero or through colostrum and milk.
• Horizontal transmission via blood-contaminated equipment, such as needles, dehorning tools, and ear tagging devices.
• Insect vectors such as biting flies may also play a role in transmission.

Pathogenesis

Once inside the host, BLV targets B lymphocytes, integrating its genome into the host cell's DNA. This integration can lead to the transformation of infected cells, resulting in lymphocytosis and, in some cases, the development of lymphosarcoma. The majority of infected cattle remain asymptomatic, but a small percentage develop clinical signs of disease.

Clinical Signs

Most BLV-infected cattle do not show any clinical signs. However, in cases where the disease progresses, symptoms may include:

• Lymphadenopathy
• Weight loss
• Decreased milk production
• Fever
• Anorexia

Diagnosis

Diagnosis of BLV infection can be achieved through several methods:

• Serological testing to detect antibodies against BLV.
• Polymerase chain reaction (PCR) to detect viral nucleic acids.
• Histopathological examination of affected tissues.

Control and Prevention

Control of BLV infection involves management practices aimed at reducing transmission:

• Implementing biosecurity measures to prevent the spread of infection.
• Regular testing and culling of infected animals.
• Use of single-use needles and equipment.
• Pasteurization of milk to prevent vertical transmission.

Related Pages

• Retrovirus
• Lymphosarcoma
• Bovine diseases
• Enzootic bovine leukosis

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