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Some Aspects of Anthrax in Bengal [VOL. XVIII, PART I,
affected and the heaviest individual district mortality figures were 1,000 in 24-Parganas, 414 in Jalpai-
guri, 100 in Khulna and 97 in Chittagong. In 1918-19, only five districts were affected and the bulk
of the mortality recorded was in 24-Parganas which returned a figure of 2,503 deaths. During these
two years, this district lost over 3,500 cattle from anthrax—the heaviest mortality ever experienced
in any district of Bengal. Moreover, in 1918-19 mortality due to anthrax constituted as much as
16.8 per cent of the total mortality in bovines due to contagious disease. For 12 years after this, the
mortality figures of the Province varied between 63 and 262. In 1931-32, 517 deaths were recorded
from 14 districts, the heaviest affected being Burdwan (111) and Chittagong (99). In 1932-33, there
were 309 deaths in eight districts (Dacca, 114; Bakarganj, 92) and in 1933-34, 329 deaths were recorded
from 11 districts (Mymensingh, 86; Rangpur, 60). Then followed a period of comparatively heavy
mortality extending over eight years from 1934 to 1942. The first year of this period, viz., 1934-35.
recorded. 1,437 deaths from 14 districts (Khulna, 1,167). In 1935-36, there were 677 deaths in 15
districts (Dacca, 297; Pabna, 104; Noakhali, 76). From 1936-37 to 1941-42, the figures varied
between 1,027 (1940-41) and 1,873 (1937-38), the heaviest losses occurring in Dacca (2,956 during
1935-1940), Mymensingh (606 during 1936-1940) and Tippera (497 during 1937-1940). In 1939-40,
as many as 22 districts were affected. Afterwards, the mortality figures gradually came down from
478 in 1942-43 to 320 in 1944 45.
Percentage of mortality
In individual outbreaks in cattle, the percentage of deaths reported, has occasionally been as
low as 40 to 50 seldom lower, and it has often been as high as 100 per cent in outbreaks of
different sizes. During 1898-1904, there was a total of 1,532 deaths out of 2,044 seizures, the percen-
tage mortality working to 75 and, in individual years, varying between 67 and 78. Balwant Singh
[1937] observed a mortality of 70 per cent during the East Bengal epizootic of 1936. During recent
years (1937-1945), about 85 per cent deaths have been recorded, with a variation in the annual figures
of 75 to 90 per cent.
Size of an outbreak
It is not always easy to decide what constitutes an outbreak. This is especially so in the case of
anthrax, because sometimes each and every case may be a separate outbreak. For purposes of re-
porting, it is customary with the district staff, to consider each affected village as a separate outbreak,
but when any contagious disease is reported to them as having broken out in more than one village on
the same date, they regard all these affected villages as falling under one outbreak. Wherever possible
in this paper, each affected village has been regarded as a separate outbreak. Very often, outbreaks
have been limited to one, two, or very few animals. Sometimes, up to fifty animals, or even more,
have been reported to be affected in one outbreak. Analysis of nearly one thousand outbreaks which
occurred during 1937-1946 gives an average of roughly eight deaths per outbreak. Considering the
system of reporting in vogue and also the probability of many single-death-outbreaks going
unrecorded, this figure would seem rather high. This, of course, does not cover the possibility of
clinically inapparent infections occurring to any extent.
Species affected
In Bengal, as in most other places, the bulk of the mortality due to anthrax occurs in cattle
which also constitute the bulk (over 70 per cent) of the total livestock population of the Province.
Buffaloes are not known to be affected to an extent proportionate to their number—over one
million and roughly 4.5 per cent of all bovines—and have often been noticed to escape infection.
During the seven years from 1936-37 to 1942-43, anthrax is reported to have killed only 186 buffaloes
against 8,659 cattle (i.e., a proportion of one buffalo to every 46 cattle and an average of roughly
27 buffaloes a year) and to have caused approximately 1.4 per cent of all deaths in buffaloes (13,335)
during this period.