220 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [VI, III
Prior to the infective inoculation, each animal was kept under observation
for about two weeks, and during this period its blood was sub-inoculated once into
rabbits and was also daily examined in wet smears for the presence of surra trypa-
nosomes, and it was brought under experimentation only after it had definitely
proved to be free from surra.
The drug used in these trials was Naganol and the dosage employed was
at the rate of 5 grms. per 1,000 lb. bodyweight in a 10 per cent aqueous solution
administered intravenously, this dosage having been based upon the results pre-
viously obtained in the laboratory in the treatment of equines, artificially infected
with surra. In view of the lower susceptibility of cattle to surra, Baermann [ 1923 ]
would appear to regard it as probable that a small dose of Naganol is sufficient for
bringing about a cure in bovine surra, and Iyer and Sarwar [ 1935 ] have actually
used what would appear to be smaller doses of the drug, with apparent success,
in the treatment of this disease. In the present trials, however, it seemed desir-
able to use the maximum therapeutic dose of the drug, in conformity with
Ehrlich's well-known dictum therapia sterilisans magna, so as to prevent any possi-
bility of the development of Naganol-resistant strains of T. evansi. As will
be seen from Tables I and II, seven animals received a single injection of Naganol,
whilst two received three injections at intervals of three months, the remaining
six animals—two bulls and four buffaloes—were kept as " controls ".
At the outset, it was realized that the criterion to be laid down for assessing
the value of a therapeutic remedy for bovine surra was the actual extent of the steri-
lization of the circulating blood brought about by the treatment, quite irrespective
of any apparent amelioration of the febrile symptoms which, as has already been
indicated earlier in this paper, has not always been found to bear any definite rela-
tionship to the actual progress towards recovery.
For the detection of the parasites in the circulating blood, three methods were
employed : (1) Daily examination of blood smears for a period of about six months
from the date of commencement of the experiments, and later, weekly and also on
the appearance of any suspicious clinical symptoms, it having been considered im-
probable that the parasites, if present, would escape detection on blood smear
examination when this was continued over as long a period as one year and a half;
(2) periodical—generally at three-monthly intervals—sub-inoculation of about
2 to 5 c.c. of blood into rabbits; and (3) sub-inoculation of about
200 c.c. of blood from each animal into susceptible equine subjects at the termina-
tion of the experiments. The observation period in the case of the sub-inoculated
rabbits ranged from four weeks to one month and that in the case of the sub-in-
oculated ponies was about three weeks. In addition, a steady and consistent gain
in body weight shown by a treated animal, as contrasted with the loss in weight
sometimes observed in the case of untreated animals, was regarded as additional
evidence of the efficacy of the remedy.