Experimental infection of laboratory animals with two "FIXED" rabies virus strains by different routes

Experimental infection of laboratory animals with two "fixed" rabies virus strains by different routes. By feeding guimea pig brains infected with the Standard Challenge Virus (CVS) rabies strain, 2 albino rats and 1 white mouse became Infected. Transmission was not effected by feeding CVS infected guinea pig tissues to either rats or mice. Feeding of CVS infected mouse brains did not produce infection in rats and mice. The mean mouse LD50 dose by intramuscular injection was 10 2.25 while the corresponding mean mouse l/C LD50 ,dose qf theCVS mouse brain suspensions used was 10 8.07 . Transmission of the Pasteur Variant (PV) rabies virus by gastric intubation of concentrated infective sheep brain suspensions in rats and mice was successful. In addition, mice could also be infected by exposure to aerosols of the same infective materials. the mean mouse intramuscular LD 50 dose of the brain suspensions was 18.5per cent. The mean mouse intracerebral LD5o of the infected materials used was 10-5.1. Virus was not transmitted to untreated white mice kept in contact with infected ones. Confirmation of rabies infection was done by either the WHO Mouse inoculation test and or the fluorescent Antibody Test (F.A.T).

Active immunization against tetanus.I. Relative efficacies of the fluid and the adsorbed tetanus vaccines (Toxoids)

Non-immune workers of the Burma Pharmaceutical Industry (B.P.I.) were immunized with either the purified fluid or the purified adsorbed Purified Toxoid Aluminium Phosphate (PTAP) tentanus vaccines. The antigenic or immunizing potencies of these vaccines were measured by titrating the serum antitoxin of thesubjects at varying time intervals after the first, second and third doses of vaccine.Statistical analysis to determine the significance of difference in mean antitoxin titres was caarried out by the "t" test for small samples. The adsorbedvaccine was found to be superior to the fluid vaccine in respect of eaarlier initiation of active immunity after the first dose and ht production of a four to eight-fold higher mean antitoxin titre after the second and third doses of vaccine. This higher mean antitoxin titre also persisted at a therapeutically protective level for a longer period.

Preventive immunization against snake envenomation.I.Immunogenicity of formol detoxified snake venom

Dessicated viper venom in a concentration of 1 mg/ml dissolved in 1 percent phosphate buffered peptone solution at pH 7.2 was formolised by adding 0.5 percent formalin and incubating at 37C for 4 weeks. The toxicity of the detoxified venom in rabbits was reduced to 69 times over that of the initial venom. Rabbits inoculated intraperitoneally with 5 ml of detoxified viper venom at 3 days intervals for 4 times were found to be able to withstand 2-3 times the minimum lethal doseof venom when challenged 7 days after last immunizing dose. The immunodiffusion studies of the detoxified venoms however showed loss of some of the components of the original venom.

Freezedrying of anti-snake venom sera

Freezedrying of antisnake venom was carried out using Edwards Centrifugal Freezedrier. The process consisted of 36 hours of primary drying followed by 24 hours of secondary drying. No differences in the chemical and biological characteristics of antivenom were observed before and after drying. Stability studies indicated that when dried to moisture content of 0.5 per cent it was stable for 2 years at 37C, 5 years at room temperature and could withstand heating at 100C for at least 4 hours.