Comparative evaluation of commonly used laboratory tests for post-mortem diagnosis of rabies.

Animal brain samples received at WHO Collaborating Centre laboratory at National Institute of Communicable Diseases (NICD) during the years 1991-2002 were tested by Seller's stain, Fluorescent Antibody Test (FAT) and Mouse Innoculation Test (MIT) as methods of rabies diagnosis. Negri bodies on Seller's staining could be detected in 52.5% of MIT positive brains, the concordance of this test with MIT was found to be 77.8%. FAT was positive in 91.5% of MIT positive brains, though it showed concordance of 95.7% with MIT results in the total samples. 12.2% of the samples were found positive by FAT of which 1/3rd also showed the presence of Negri bodies when MIT was negative i.e. showing that the virus is present in inactivated form. Thus emphasizing the need for timely and proper collection and transportation of specimens for testing. Seller's stain and FAT give reliable diagnosis of rabies in the brain samples in majority of the cases. MIT being time-intensive test, is of academic value only in decision making as regards initiation of Post Exposure Treatment (PET), it is recommended that in cases where Seller's stain and FAT have yielded negative results the decision to initiate PET should give due consideration to the nature and circumstances of the animal bite and other epidemiological features.

Immunogenicity of purified chick embryo cell anti-rabies vaccine in post-exposure treatment of animal bite cases.

The observations on immunogenicity of Purified Chick Embryo Cell (PCEC) anti rabies vaccination in post-exposure prophylaxis is reported. In total 207 serum samples collected from patients receiving 3 to 6 doses of PCEC were analysed for the presence of anti-rabies antibodies. The samples were collected from 10 days to 11 months after the last dose of vaccine. All the vaccinees (n=33) tested after 3 doses of PCEC showed protective titres (> or = 0.5 IU/ml) and those receiving 5-6 doses (n=161) showed 4-5 times higher than protective titres. The analysis pertains to specimens collected at one point of time only after the vaccination. However, in all 17 vaccinees where samples were collected 7-11 months after 3-6 doses of vaccine, the protective titres were sustained, these being 3-4 times higher than the protective titres in those receiving 5-6 vaccine doses. The results indicated that there was no need of routine anti-rabies antibody monitoring in healthy individuals receiving post-exposure prophylaxis in recommended doses of vaccine.