Intra vitam diagnosis
In addition to the brain and spinal cord, rabies virus antigen can be detected by FA in the peripheral nerves, salivary glands, saliva, and also in the cornea and skin during the final stages of the disease. Intra vitam diagnosis of rabies by FA in corneal impressions was first described by Schneider in animals and by Cifuentes et al in humans. However, a study of the reliability of corneal impressions for rabies diagnosis showed that, especially when sampling is done under field conditions, a negative result could not rule out the diagnosis of rabies. Examination of skin biopsy material was shown to be a valuable technique for intra vitam diagnosis of rabies in animals and humans. Anderson et al showed that rabies antigen may be detected in skin biopsies from humans at the onset of clinical signs. In contrast, Blenden et al found that only some patients (25-50%) showed positive results during the early phase of clinical illness and that the proportion of positive results increased as the disease progressed.
Specimens for intra vitam diagnosis should be of a good quality. They should be refrigerated immediately after collection and until the test is carried out. This is important, since partially autolysed specimens will reduce the percentage of positive results and contamination of the material may lead to false-positive results. Examination of skin biopsies may also be used for post-mortem diagnosis in countries where opening of the skull of the dead person is not accepted by relatives on cultural or religious grounds.