Early Diagnosis of Rabies by Mouse Inoculation. Measurement of Humoral Immunity to Rabies by Mouse Protection Test

A method for early and reliable diagnosis of rabies by animal inoculation and a protection test for measuring humoral immunity to the virus may become feasible by the use of highly susceptible strains of mice. Ordinarily the injection of brain tissue from rabid animals into rabbits or guinea pigs incites the disease irregularly and after incubation periods of 2 to 8 weeks. Mice as test animals have proved in the past even less satisfactory. 1 Mice especially bred for high susceptibility to neurotropic viruses, however, are more sensitive and uniform in their response to the rabies street virus.

The diagnostic test for rabies by mouse inoculation is carried out in the following manner: Fresh dog brain containing Negri bodies∗ is seared and dissected aseptically to expose Amnion's horn. This area is removed and portions emulsified, diluted approximately 10 times, centrifuged, and injected into mice intracerebrally in 0.03 cc. quantities and intraperitoneally in 1/2 cc. quantities. Some of the mice are sacrificed from the 5th to 8th days, their brains removed, and impression transfers made from Amnion's horn and stained to determine the presence of Negri bodies. The remainder are observed for the appearance of characteristic weakness and paralysis of hind legs, prostration, and death. Final tests for Negri bodies are made on sick and prostrate mice.

To date, 40 dog brains received by the New York City Department of Health Laboratories have been tested. In 32 specimens, no Negri bodies were found and the test mice remained well for 30 days. In 7 specimens, Negri bodies were demonstrable. Of these, 2 specimens, Nos. 1 and 3, were injected intracerebrally into 6 and 19 mice respectively. The 6 mice receiving specimen No. 1 remained well 10 days, were weak or paralyzed on the 11th day, and prostrate or dead on the 12th day.