[Rabies Tissue Culture Infection Test as an Alternative for the Mouse Inoculation Test]

Rabies has disappeared from large parts of Switzerland. Due to systematic oral fox-vaccination campaings that started in 1987, cases of rabies in wild and domestic animals have been confined to the western frontier with France in the last three years. Nevertheless, some cases of severe exposition of man by rabid or rabies-suspect animals still occur. Rabies can be diagnosed in brain smears of infected animals with high specificity and sensitivity by a direct immunofluorescence method. According to WHO recommendations, negative results are to be confirmed in cases of a human exposition by intracerebral inoculation of brain suspensions in three-weeks-old mice. This method has an excellent sensitivity and is able to detect false-negative results in immunofluorescence, which occur in a very small percentage (0.043%). The disadvantage of this confirmatory assay is the sacrification of relatively high numbers of mice (in the Swiss rabies center about 1,300 animals each year), and the long time required for a final diagnosis: 7-20 days in positive, 21 days in negative cases. The cultivation of virus from brain suspensions on a mouse neuroblastoma cell line is a tempting alternative to the mouse inoculation test. This method usually provides a conclusive diagnosis within a few days. However, in our hands it showed in preliminary experiments an unsatisfactory sensitivity (80.7%). The necessity to carry out strict reproducibility controls in this assay has to be emphasized. Further work must be invested in the improvement of the rabies tissue culture infection test and a careful long-term comparison with the mouse inoculation test will be necessary before the mouse inoculation test can be replaced.