Bovine lentiviruses
Two species of lentivirus that infect bovine species have been described: Bovine Immunodeficiency Virus (BIV) and Jembrana Virus (JV).
- Discovery: BIV was first identified in dairy cattle in the United States in the late 1960s.
- Virus Characteristics: BIV is a lentivirus, characterized by slow disease progression. It shares similarities with other immunodeficiency viruses such as HIV, particularly in terms of genetic structure and replication mechanisms.
- Symptoms: While BIV infections are generally subclinical, meaning they do not always result in obvious symptoms, some cattle may show signs of immunosuppression, weight loss, lymphadenopathy, and a reduction in milk production. However, the exact impact of BIV on cattle health remains unclear, as many infected animals remain asymptomatic.
- Transmission: BIV is believed to be transmitted through blood and body fluids, similar to other lentiviruses. Natural transmission likely occurs via biting insects or through close contact among cattle, such as during milking or veterinary procedures.
- Impact on Livestock: BIV's role in disease is still debated, with limited evidence suggesting that it might contribute to decreased productivity in infected cattle. Research into its pathogenesis and economic impact continues, but it is not considered a major cause of disease in cattle.
- Discovery: Jembrana Virus was first described in the 1960s during an outbreak on the Indonesian island of Bali.
- Virus Characteristics: JV is a lentivirus, like BIV, but it causes acute disease in cattle, specifically in Bali cattle (Bos javanicus), which are more susceptible than other breeds.
- Symptoms: JV causes a severe acute disease known as Jembrana disease. Symptoms include high fever, enlarged lymph nodes, hemorrhages, and a high mortality rate, particularly among Bali cattle. The disease often results in severe losses during outbreaks, with up to 20% mortality in affected herds.
- Transmission: The virus is primarily spread through blood-to-blood contact, often facilitated by biting insects like mosquitoes or through medical procedures like vaccination or dehorning that involve shared equipment.
- Economic Impact: JV has significant economic implications in regions where Bali cattle are farmed. Outbreaks of Jembrana disease can result in severe herd losses and increased costs associated with containment and control.
- Genetic Relatedness: BIV and JV are genetically similar and both belong to the lentivirus group, but they have vastly different impacts on cattle health. BIV infections tend to be chronic and subclinical, while JV causes acute and often fatal disease.
- Research: Comparative studies of BIV and JV can provide insights into lentivirus evolution and pathogenesis, as they illustrate how different strains within the same viral genus can cause varying degrees of disease severity.
These viruses highlight the diversity of lentivirus infections in animals and underscore the importance of understanding viral evolution, host-pathogen interactions, and the potential for cross-species transmission.