The plague mortality in cases which had previously been inoculated was 40% while that among the noninoculated was 78%.
From the above it will be seen that incidence is reduced to about one-fourth and mortality about one-half as the result of the use of Haffkine’s prophylactic.
Besides this killed culture other material has been used. Lustig and Galleotti used the nucleo-proteid from plague bacilli for subcutaneous injection. Kolle and Strong have recommended a vaccine of living but nonvirulent plague bacilli. A higher degree of immunity seems to be conferred by this living vaccine but there are certain dangers in the use of living organisms which outweigh the advantage noted above.
Yersin’s antiplague serum, which is prepared by injecting horses at first with killed cultures and later with living plague bacilli, may be used as a prophylactic as well as in treatment. One point to consider is that such serum, if used immediately after taking from the horse, might contain living plague bacilli. The phenol preservative prevents this. It must be remembered that this is a passive immunization as against the active one with Haffkine’s prophylactic, hence the protection is very short, only ten days or two weeks as against the more enduring immunity of a year or so following Haffkine’s prophylactic. It must be remembered that anaphylactic manifestations may follow the repeating of the dose of Yersin’s serum. It is probably advisable for one who is to be exposed to plague for a short time only to receive an injection of the serum. As regards pneumonic plague there seemed to be little protection attaching to either active or passive immunization.
Treatment.—It may be stated that the only treatment which has any curative value is that with antiplague serum. This would appear to be of considerable value in bubonic plague provided it is administered in the first day or two of the disease. It must be given in large amounts, from 50 to 100 cc. or even to the extent of 250 cc. Then too such enormous doses apparently require to be repeated. Intravenous administration gives a better chance for success in desperate cases. In septicaemic and pneumonic plague the use of serum has been without result.
Salvarsan, as might be expected, has been tried but did not prove of any value.
Connor has reported success with the intravenous injection of one dram of a dilution of 1 part of tincture of iodine in 10 parts of sterile water. He gave 6 such injections to a severe case with good result.
In the way of symptomatic treatment one should use ice-bags to head and cold sponging to the body.
Morphine seems to be the best drug to calm the patient. Cardiac stimulants, especially strychnine, are indicated for the heart weakness so much a feature of plague. Some consider incision or enucleation of the bubo of value in treatment but it has always seemed to me that the going into the periglandular exudate might serve to set up a septicaemic condition when otherwise it might not supervene.