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The amount prepared is in excess of that of the previous year; partly because of the greater number of calves vaccinated and partly because of the greater yield of lymph obtained per calf.
Experiments were carried out to determine a method of vaccination which would produce a greater yield of lymph than had been heretofore obtained. It was hoped that the method advocated by Stuart and Krikorian (Ann Trop. Med, & Parasit. 24: No. 4, 527, 1930) would be an improvement, but it was abandoned after careful trial; in our hands it offered no advant- ages. Ultimately we adopted the simple expedient of spacing the lines of insertion definitely closer together than had been our previous practice. The result was quite satisfactory, as the figures for the year show a 20% increase in the yield of lymph obtained. This should materially lower the cost of production.
The routine of bacteriological control of the finished lymph before issue has also been brought nearer to the ideal. In addition to previous procedures plate counts are now done and potency tests on rabbits performed with graded dilutions. Through the kindness and cordial co-operation of the Medical Director and staff of the Alice Memorial and Affiliated Hospitals we are now able to have potency tests performed on new-born babies on every batch of lymph before issue. At the present moment for this purpose we are using lymph of full strength as well as
a dilution 1 in 5 in each case. The possession of definite evidence of the potency of every batch of lymph issued is a valueable safeguard against possible loose criticism of our lymph as well as being a useful check on our own methods of production.
E. PREPARATION OF VACCINES AND SERA.
The work under this head has been very heavy for the year reported. This has been due chiefly to the epidemic of cerebro- spinal meningitis referred to in a previous paragraph which necessitated putting up and distributing large quantities of anti- serum. The stock of antiserum prepared and on hand in cold storage was adequate to meet the demands of the situation but we are left with the task of replenishing it to the previous figure with a view to the possibility of a similar demand at any time in the future. From the clinical data available it appears that the serum has been therapeutically efficacious.
The total amount issued was 29,360 c.c. Of this amount 6,240 c.c. was exported to Macao on the request of the health authorities there.
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Preparation of fresh serum had been in abeyance previous to the epidemic owing to the large stock on hand, so that only 7,350 c.c. was prepared during the year. This leaves us with approximately 30,455 c.c. in stock. Two ponies are being im- munized steadily at the present time for the production of serum, and a fairly large quantity should be accumulated in the coming year provided the disease remains in abeyance.
The opportunity has been taken to add new strains of virulent meningococci isolated during the progress of the epidemic to the strains maintained for the production of antiserum. This should do something to strengthen the antigenic value of our antiserum.
The preparation of gonococcus vaccine still shows a marked increase over previous years, as was predicted in last year's report; the amount being 4,370 c.c. This is nearly double the amount prepared in 1980. While the method of preparation has been slightly improved so as to give a higher yield this is still short of the ideal and further improvement is still being sought.
The epidemic of cholera was responsible for a large and sudden demand for anti cholera vaccine. We were able to fill all demands made in this connection and altogether 17,272 c.c. was supplied. Of this amount 1,476 c.c. was distributed outside the Colony.
The number of autogenous vaccines prepared shows a great increase over the previous year, namely 47 as against 26.
Anti-rabic vaccine was prepared for use in the Colony as usual. The method of preparation of the vaccine which had been in use for some years was revised and the method used in Ceylon, Malaya, India, etc. substituted in its place. The prepared vaccine consists of a 1% dilution of brain and cord substance in 0.5% carbolic saline. The dosage for the average adult case is 5 c.c. daily subcutaneously for 14 doses. The necessary fixed virus is maintained by regular passage through rabbits at fortnightly intervals.
One hundred and sixty one courses of treatment were in- stituted, but of this total only fifty-four completed the prescribed Actually one thousand five hundred and seventy doses were issued.
course.
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