MORPHOLOGICAL STUDIES OF THE BLOOD OF HILL BULLS IN HEALTH
AND DURING ACUTE THEILERIASIS*
By B. M. PRASAD, G. B. V. C., Imperial Veterinary Research Institute,
Mukteswar
(Received for publication on 7 July 1944)
THE purpose of the present study was to obtain precise data on the total red-cell and
white-cell counts, the differential white-cell counts and the haemoglobin content of the
blood of Indian cattle in health and during acute theileriasis and thereby, if possible, to
discover any factor involved in the biological behaviour of the causative agent that might
be utilized for evolving a method of effective treatment.
Literature on the haematology of bovine blood is rather scanty and reference may
be made to articles by Delaune [1940], Manresa and Reyes [1934], Sankarnarayan [1937]
and Sen and Srinivasan [1937].
The only publication available specifically on a similar problem is that of Steck [1928]
who studied the blood of cattle in South Africa in some detail during health and during
theileriasis (East Coast fever). Summarizing the results of his studies on 13 animals, he
states that with the onset of fever the leucocytes decrease in number progressively until
death and that all the cells take part in this decrease. From the tables and charts
illustrating Steck's paper it appears that from an average of about 13,000—15,000 leucocytes
per c. mm. prior to infection, the count dropped in almost every case to an average of 500
per c. mm. In the differential white-cell counts, a marked variation was noticed between the
normal and clinical periods. The mean percentage of various types of cell, as recorded
during the preinfected state, is given as follows:—neutrophiles 23 per cent, eosin-
ophiles 4 per cent, lymphocytes 58 per cent, mononuclears 5 per cent. Occasionally, mast
cells at 0.5 to 1 per cent were seen. Cases were studied during the incubation and
clinical periods and although total leucocytes were markedly reduced, there was extensive
lymphocytosis. From the onset of clinical symptoms, the increase in lymphocytes was
noticed and this continued till death. The number of all other white cells was reduced
almost to nil, indicating that throughout the course of the disease the lymphocytes play a
prominent part in the blood pathology of the condition. The changes described above were
observed in almost all animals showing the typical clinical picture of East Coast fever,
experimentally produced through infected ticks. The haemoglobin content was not estimat-
ed and although from the tables it appears that there was also a drop in the red-cellcount
the author does not mention this in his article.
METHODS AND METHODS
Seven hill bulls, three to seven years old, were used in the present investigation. These
were housed together and given uniform ration. Six of them were inoculated in two lots
with infected blood from artificially infected cases of theileriasis and one served as a
control. To obtain the normal blood picture, counts were made from these animals for two
days to a fortnight prior to infection, viz. eleven counts on four animals and three counts
on two of them. Only four of the six bulls reacted but in none was the disease
fatal.
For the red and white-cell counts, blood was collected from the jugular vein into
tubes containing sodium citrate. To ascertain the accuracy of this method, blood was
frequently drawn directly from the ear in the usual way into red and white potain
pipettes.
For the red-cell count the blood was diluted 200 times in potain pipettes, using
Toisson's fluid, and transferred to a Thoma (Hawksley) haemocytometer. In each case 100
squares were examined. The white blood corpuscles were counted in potain pipettes at
dilution of 1 : 10, with 3 per cent acetic acid tinged with gentian violet.
For differential leucocyte counts, blood smears were prepared in the ordinary way
from the ear vein and stained with Giemsa. Two methods were employed, viz. the
Meander method, and counting many fields in one straight line from the beginning to the
tail end of the smear. Immature cells of lymphoblastic and myeloblastic origin were
differentiated by oxidase reaction in freshly prepared blood smears. For this purpose the
* The causal agent of acute theileriasis in India is provisionally determined as Theileria annulata.
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