Serological evidence of rickettsial infections in Delhi.

Background & objectives: Rickettsial infections remain under-diagnosed due to lack of diagnostic facilities in developing world. Here we present our experience at National Centre for Disease Control, Delhi, about a serosurvey done in Delhi for rickettsial disease with easy to perform low cost, low expertise Weil Felix test. Methods: On the basis of cut-off titre obtained in healthy population, Weil Felix test results were interpreted along with clinical data. Entomological investigation was also carried out in select areas of Delhi. Rodents were trapped from houses and gardens and vector mites were collected. Results: When serum samples were collected during initial 5 yr period from patients with fever of unknown origin, seropositivity was 8.2 per cent whereas when rickettsial infection was kept as one of the differential diagnosis by clinicians seropositivity increased to 33.3 per cent. Rickettsial infections detected were scrub typhus (48.2%) followed by spotted fever group (27.5%) and typhus group (6.8%) during 2005-2009. In preliminary entomological survey vector mite Leptotombidium deliense was found on rodents. Interpretation & conclusions: Our findings showed that results of Weil Felix test should not be disregarded, rather clinically compatible cases should be treated to save lives.

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.