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Antibody responses to Fermi antirabies vaccine in 21 patients bitten by a rabid jackal
B A Botros1, T G Ksiazek, R M Scott
1U.S. Naval Medical Research Unit No. 3, Cairo, Egypt.
Abstract:
In a village in Upper Egypt, 21 persons were bitten by a rabid jackal. All received antirabies vaccine of the Fermi type within a few hours after the exposure. Antirabies hyperimmune serum was not administered. Three of the 21 victims died on days 16, 17 and 27 after exposure. Blood samples were obtained from 19 of the 21 bitten persons 5 days after completion of a series of 20 vaccine doses. Sera were tested for rabies antibodies by the indirect fluorescent antibody test (IFAT) and enzyme-linked immunosorbent assay (ELISA) test. All 19 persons developed rabies antibodies detectable by these techniques. IFAT titres ranged from 128 to greater than or equal to 1024. ELISA antiglycoprotein titres were generally low, ranging from 0.7 to 18 iu/ml of serum.
Insights
Rabid jackal bites in Egypt led to 3 deaths despite Fermi-type antirabies vaccine. However, all survivors developed rabies antibodies, indicating vaccine effectiveness in antibody production.
Area of Science:
- Virology
- Immunology
- Public Health
Background:
- Rabies is a fatal zoonotic viral disease transmitted through bites from infected animals.
- Jackal bites pose a significant rabies transmission risk in endemic regions like Upper Egypt.
- Prompt post-exposure prophylaxis (PEP) is crucial for preventing rabies.
Purpose of the Study:
- To evaluate the immunogenicity of Fermi-type antirabies vaccine in humans exposed to a rabid jackal.
- To assess rabies antibody development following a standard vaccination series in a real-world exposure scenario.
Main Methods:
- Twenty-one individuals bitten by a rabid jackal received Fermi-type antirabies vaccine.
- Blood samples from 19 individuals were tested for rabies antibodies using indirect fluorescent antibody test (IFAT) and enzyme-linked immunosorbent assay (ELISA).
- Antibody titers were measured after completion of 20 vaccine doses.
Main Results:
- Despite vaccination, three out of 21 individuals succumbed to rabies.
- All 19 tested individuals seroconverted, developing detectable rabies antibodies.
- IFAT revealed high antibody titers (128 to ≥1024), while ELISA showed generally low antiglycoprotein antibody levels (0.7–18 IU/ml).
Conclusions:
- Fermi-type antirabies vaccine induced detectable antibody responses in all exposed individuals.
- The occurrence of rabies deaths suggests potential limitations in vaccine efficacy or factors influencing disease outcome.
- Further investigation is warranted to understand the discrepancy between antibody levels and clinical outcomes in rabies post-exposure prophylaxis.