Jembrana disease in Bali cattle and it prevention by vaccination

Jembrana disease is an acute infectious disease which is clinically found only in Balinese cattle. The disease is caused by lentiviruses of the Lentivirinae subfamily, and Retroviridae family. Generally, lentivirus caused slow-progress infections in both animals and humans and disease generally occurs many years after infections.  Such slow-progress infection can be observed in human immunodeficiency virus (HIV) infections in humans in which clinical disease ussully appears around 7-9 years after infection. In addition, some people with HIV infection remain clinically normal without showing any symptom of the disease. A similar situation can also be observed in other lentivirus infections in animals such as bovine immunodeficiency virus infection in cow and sheep, simmian immunodeficiency virus (SIV) in monkeys and feline immunodeficiency virus (FIV) in cats. However, in contrast to aforementioned lentivirus infections, Jembrana disease in Bali cattle is an acute  I and sometimes fatal disease with short incubation period (4-12 days). In Jembrana disease-free areas, the mortality rate of the disease in Bali cattle is around  17% and recovered animals usually carry the virus for a long time.

Jembrana disease are usually characterized by high fever (42 ° C), oral mucosal erosion, enlarged precapular dan prefemoral lymphonodes. Enlargement of those lymphmodes can be observed clearly in Balinese cattle during febrile state and is a very important clinical symptom in the initial diagnosis of Jembrana disease in Bali cattle. Hematologically, Jembrana disease virus infection in Bali cattle is characterized by a leucopenia (especially lymphocytes) and the decrease in platelets count which are very in the diagnosis of Jembrana disease in Bali cattle. Such leucopenia lead to immunosuppression in Bali cattle with Jembrana disease especially during acute stage of the disease. The immunosuppresive conditions is characterized by the disappearance of B cells in the acute stage and its reappear during the recovery stage of the disease. In animals recovering from Jembrana disease, antibody against the virus usually only appear about 2 months after infection. Humoral (antibody) immune response is therefore suggested to be not play important role in the recovery of animal from Jembrana disease. This is in accord with the finding that in the acute phase of the disease, an increase in CD8 + T cell population and IFN-g levels, indicating that cellular immune response play important role in the recovery of Bali cattle from Jembrana disease.

               Vaccines to prevent Jembrana disease are available and are usually prepared using a virus from the spleen of infected-Bali cattle. The virus is activated by Triton-X-100 and emulsified in an adjuvant mineral oil (MOA) and given twice at 1 month intervals. This vaccine induces an immune response capable of preventing death and reducing the amount of virus in blood and shortening the clinical symptoms of the disease. Efforts to develop recombinant vaccines using Capsid and tat proteins have also been made, but trials in Bali cattle have shown that the vaccine has not been able to prevent Jembrana disease virus infection in Bali cattle. Further efforts is needed to develop an effective vaccines against Jembrana disease in Bali cattle which eventually lead to eradication of  Jembrana Disease from Indonesia.