CO885-(20-21) — Page 56

PUBLIC RECORD OFFICE

Reference :-

C.O. 885

20 PUBLIC RECORD OFFICE, LONDON

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the 5th September the dog had fallen off in condition, an erythematous eruption with papules appeared on the skin, the hair fell out over the areas of skin eruption, rapid wasting followed, and death supervened on the 30th September.

On Post Mortem great emaciation, skin eruption present, mucous membranes very pale, internal organs very pale, tape worm in the intestine, liver jaundiced.

Remarks. In this case it is evident that the blood of Horse C, which was used as a protective inoculation, had the effect of preventing the development of trypano- somes in the dog, when he was inoculated with virulent blood from Calf J which was suffering from trypanosomes, had trypanosomes in its blood, and had not been subjected to any treatment by mercury. This dog lived for seven months after his first inoculation with blood from Horse C.

Calf J (see Charts 24a and 24b).-This calf was infected by inoculation of 10 c.c. blood on the 19th April from Horse G suffering from trypanosomiasis. On the 26th April his blood was found to contain trypanosomes, and on that day 8 c.c. of blood was inoculated into Dog J to see if Dog J had been rendered immune by the inoculations of blood made from Horse C (already described under the case of Dog J). After this inoculation the calf was treated for three days by injections of mercury, which did not remove the trypanosomes from the blood, although the temperature came down. On the 10th May 9 c.c. of blood was inoculated into each of Dog H and Dog M (see pages 63 and 64) which did not subsequently show trypanosomes in their blood, and on the 14th May 8 c.c. of blood was inocu- lated into Calf L (see page 65) to continue the strain of the trypanosome and it developed the disease with trypanosomes in its blood, but no trypanosomes deve- loped in Dog M, showing that the virulence of the organisms had been lowered by the mercury treatment towards Dog M but not towards Calf L. Later, on the 22nd May, when the blood of Calf J was still full of trypanosomes, 8 c.c. were inoculated into Dog T and 2 c.c. into Dog U. The calf grew weaker, lost flesh rapidly, could not rise on the 27th, and died on the 2nd June.

Dog T (see Charts 25a and 25b) was, on the 22nd May, inoculated with 8 c.c. of blood from Calf J, which still continued to show trypanosomes in its blood after having been treated for three days by mercury. The charts will show that the dog never showed a rise of temperature nor did trypanosomes develop in its blood. On the 30th June the temperature observations ceased but the animal was kept * under general observation. The dog steadily fell off in condition and became reduced

to a skeleton. He finally died on the 24th August.

Dog U (see Charts 26a and 26b) was, on the 26th May, inoculated with 2 c.c. of blood from Calf J, which had trypanosomes in its blood after having been treated for three days by mercury. The subsequent history as shown by the charts is the same as of Dog T; there was no rise of temperature and no trypanosomes appeared in the blood. Observations of temperature ceased on 30th June, but the dog was still kept under general observation; he became reduced in condition and died on the 25th August.

Remarks The results in these two cases of Dogs T and U are identical, although the dose of blood in the case of former was 8 c.c. and of the latter 2 c.c. It is evident that the treatment of Calf J for three days by mercury had an effect on the virulence of the organisms whereby they did not develop in these two dogs (as in the case of Dog M), whereas the blood of this Calf J'after the course of mercurial treatment for three days did infect Calf L, showing that the virulence of the organisms had not been lowered for the calf. Both dogs, however, wasted away and died, and the remarks made on Dog L in Section II., on page 57 of this report apply to these cases, viz., that the inoculation of blood from a calf which had been treated by mercury which had not removed the trypanosomes from the blood did not reproduce a definite attack of the disease in the dog, as shown by a rise of temperature and an invasion of the blood by trypanosomes; but the dogs wasted and eventually died after some months, showing that (1) trypanosomes on inoculation either altered their phase, or (2) died out and gave rise to some form of chronic intoxication together with the toxic material probably already formed in the blood animal treated, and that in either case it proved fatal to the dog after a prolonged period as compared to the duration of life of a dog after natural infection, or after inoculation of virulent trypanosomes from an animal that had not been treated by mercury. A point however to be considered is that the effect of keeping up a strain of trypanosome for a prolonged period by sub- inoculations of animals may have in itself lowered the virulence of the organisms, for the trypanosomes failed to develop in the dog (see the remarks on the case of Dog J, above, and the remarks on the case of Dog II, page 63).

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The following two cases were experimented on as follows:-

Dog W (see Charts 28a to 28c) was inoculated subcutaneously on one side of the chest with 10 c.c. of blood from Horse F, which had been treated and was free from trypanosomes, and on the other side was inoculated with 1 c.c. of virulent blood from Calf L, which contained a great many trypanosomes, and, moreover, the calf had received no treatment-the object of this was to see if the blood of Horse F would exert a protective action when inoculated simultaneously with the infection. As a control to this,

Dog (see Charts 29a and 29b) was on the same day inoculated with 1 c.c. of blood from Calf L also. The result in both cases was the same, namely, that both dogs had hardly any rise of temperature, neither ever showed any trypanosomes in the blood, both wasted away and eventually succumbed-Dog W on the 5th August, and Dog V on the 30th July.

Remarks. Now we see that in the former case of Dog W, the simultaneous inoculation of blood from Horse F, which had been treated by mercury and whose blood was free from trypanosomes, with the inoculation of virulent blood from Calf L appears to have proved protective, but the control inoculation of Dog V on the same date from Calf L alters this conclusion considerably, for not only did Dog W not develop trypanosomes in his blood, but Dog V also failed to do so, and the two subsequently ran a similar clinical course, so that the non-development of the trypanosomes in the dogs and the lowering of the virulence of the organisms so far as the dog is concerned may be due mainly to the effect of treatment by mercury, and to attenuation of the strain owing to prolonged transmission of the virus by inoculation through a series of animals. These conclusions will be borne out by the results of experiments on Dogs W and V, which will be described later.

Dog N. (See Charts 27a to 27d.) On the 23rd March Dog N was inoculated with 2 c.c. of blood from the heart of Calf H, which had been treated by mercury, on post-mortem one hour after death of the calf from trypanosomiasis. This was done with the object of keeping up the strain, but three days later, fearing that the inoculation may have failed because the blood had been taken post-mortem, the dog was again inoculated with 6 c.c. of blood from Horse G, which had just developed the disease, and had trypanosomes in his blood, but had received no treatment. Subsequently this dog had rises of temperature but never showed any trypanosomes in its blood; he ultimately wasted, and died on the 16th August, after a period of 4 months and 20 days.

Remarks. It is evident that the inoculation of 2 c.c. blood on post mortem from Calf H, which had been treated by mercury, had the effect of inhibiting the develop- ment of the virulent trypanosomes from Horse G when inoculated into Dog N.

Dog W (see Charts 28a and 23b.)-Owing to the results obtained in other cases, e.g., in Dog J, page 65, where the inoculation of blood from horses which had been treated by mercury, and was free from trypanosomes, seemed to have the power of protecting them when inoculated with blood containing trypanosomes, which failed to develop in the dog, proving that the virulence of the organism must have been lowered so far as the dog is concerned, and it is most likely, as seen from the observations made on Dogs W and V (above), that the constant direct passage of the trypanosome from one animal to the other by inoculation, together with the effect of treatment, must have had this effect of lowering the virulence of the strain towards dogs.

FURTHER IMPORTANT EXPERIMENTS.

Owing to results attained in previous experiments a definite series of subcu- taneous inoculations of several animals was made with a view to trying to confer immunity by means of injecting (A) blood and (B) serum from animals that had been treated by injections of perchloride of mercury or by methylene blue followed by a course of perchloride of mercury.

A. Blood taken from horses that had been treated by the perchloride of mercury was injected into the following animals:-

(a) Horse H received 81 c.c. blood from Horse C. (b) Calf K

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(c) Dog Q

88 c.c. 28 c.c.

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(d) Dog R

8 c.o.

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(e) Monkey E

16 c.c.

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F.

J

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