Timing IssuesPathologyEpidemiologyClinical ManifestationsInfectiousnessProtection
The incubation period is about four weeks (observed in horses and sheep). During this period, infected animals show nonspecific signs including hyperthermia, anorexia, and colic. Clinical illness typically last one to three weeks.
It is believed that transmission between animals occurs through saliva, nasal, or conjunctival secretions by direct contact or by exposure to contaminated food or water. Borna is predominately, but not exclusively, neurotropic. It appears to enter the CNS by intraaxonal migration through the olfactory nerve or nerve endings in the oropharyngeal and intestinal regions. From there, it spreads to the peripheral nerves. In addition to the CNS, T-cells play in important role in the pathology of BDV. In studies conducted on animals, immunocompromisedd and immunosuppressed rats did not become ill with borna disease despite viral replication in the CNS.
Evidence suggests an association with BDV and psychiatric disorders including depression and schizophrenia. Epidemiological studies showed an increased incidence of seropositive by 600% in young (ages 17-30) psychiatric patient compared to young surgical patients (controls). These finding correspond with the fact that psychiatric disorders frequently initially manifest in young people. This strongly suggests that BDV plays a role in the pathogenesis of psychiatric disorders.
In animals, BDV clinical manifestations range from inapparent infections, behavioral abnormalities (including depression, circular movement, standing in awkward positions, collapsing, and running into obstacles) obesity, fertility problems, and neurological diseases such as paralysis. Studies have indicated that cases of inapparent BDV infection may be common in humans as well. Although serological studies indicate an association between BDV and psychiatric disease, as of yet, an unequivocal role of BDC infection in such conditions has not been established.
BDV is not highly contagious. Studies that support this showed that an individual horse can be infected in a stable without other horses displaying clinical manifestations. Furthermore, in human studies conducted with BDV-seropositive patients and family members very few cases of horizontal transmission occurred.
Although BDV T-cells induce illness, they also offer protection. Studies have demonstrated that rats injected with BDV-specific T cells before infection were protected against borna disease when infected. Furthermore, when viable BDV-specific T-cells were injected after infection, clinical manifestations appeared faster in BDV-uninfected animals faster than BDV-infected animals.
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