RABIES I. Infective Agent.—Unknown, a filterable virus.
2. Source of Infection.—Typical and atypical cases and incu batory carriers in dogs, and other carnivorous animals.
3. Portal of Exit.—In the saliva of infected animals.
4. Route of Transmission.—Inoculation with the saliva of infected animals, through wounds or abrasions of the skin and mucosa, almost always by bites or scratches.
5. Portal of Entrance.—Through the subcutaneous tissue to the terminal nerve fibers.
6. Incubation Period.--Variable, seldom less than four weeks and occassionally six months or longer.
7. Period of Communicability.—For perhaps two weeks prior to the manifestation of symptoms and throughout the clinical course of the disease.
8. Methods of Diagnosis (in animals).—Clini cal manifestations of animals, confirmed by the finding of Negri bodies in the brain, or by successful animal inoculations with such a brain.
(b) Isolation (of Patient).—None, if patient is under adequate medical supervision and the immediate attendants are warned of the possibility of inoculation by human virus.
Animals which are suspected of being rabid and which have bitten or exposed a person to infection, should not be killed, inasmuch as the laboratory confirmation of the suspected diag nosis may be rendered difficult or time consuming. Such ani mals should be confined in rigid isolation and closely observed. If actually rabid, death will occur within ten days and the diagnosis can be confirmed by the clinical course and labora tory examination. If the animal is alive at the end of this period the question of rabies is eliminated. This precaution does not endanger the patient through too great delay in be ginning the Pasteur treatment.
(c) Immunization.—The administration of active immuniza tion (Pasteur treatment) after exposure to infection by inoculation. The Pasteur treatment should be administered under the following circumstances: A. From a diagnosis of rabies in the biting animal based on one or more of the iollowing data: (1) Clinical manifestations, (2) Negri bodies, (3) Inoculation, or, B. On suspicion, where the biting animal is at large but manifested suspicious symptoms.
Various methods have been devised for the attenuation of the rabies virus, but those is most general use closely follow the technique developed by Pasteur. The rabic virus derived from
carnivorx is attenuated for man by successive passages through rabbits, until its incubation period becomes constant. It is then known as fixed virus, and has an incubation period of six to seven days when inoculated intracerebrally into rabbits. The spinal cord of a rabbit dying of fixed virus infection is asepti cally removed intact and dessicated in a jar over sticks of caustic soda, producing a further attenuation. From day to day, up to the 8th day of dessication, pieces of dried cord repre senting about i cm. of the fresh cord are removed to glycerine and designated as one, two or three day cord, etc., according to the extent of the dessication to which they have been sub jected. Under refrigeration, these remain potent about one month.
For administration the dried cord is further prepared as follows: A piece of the dried cord is washed in saline to remove the glycerine, and ground in a small mortar until homogenous. Then drop by drop two and five tenths c.c. of saline are added and thoroughly mixed with the cord until a homogenous sus pension is secured. This is the material for injection. The site of election is the subcutaneous tissue of the abdominal wall, which is prepared by painting the skin with iodine.
With the vaccine distributed bythe U. S. P. H. S., the course of treatment covers twenty five injections given over a period of twenty one days. The schedule followed in the intensive treatment of adults is as given in the prqeding table.
(d) Quarantine.—Of dogs transported from infected to unin fected areas for six months.
(e) Concurrent Disinfection.—Of patient's saliva and objects contaminated therewith.
(1) Terminal Disinfection.—Thorough cleaning.
General Measures.—(a) Muzzling of dogs when on public streets or in places to which the public has access (Fig. 92).
(b) Detention and examination of dogs suspected of having rabies. Detention should be maintained ten days. If death occurs search should be made for Negri bodies.
(c) Provision for the immediate anti-rabic treatment (active immunization) of persons bitten by dogs or other animals suspected or known to have rabies. The wounds should be cauterized with fuming nitric acid as soon after their infliction as possible.