MARCH 1948] RAM NARAIN MOHAN AND SYED MAHMUD ALI 5
DIAGNOSIS
Since some years ago, it has been made the. routine practice for the district staff to submit for
microscopical examination blood-films from cases suspected of anthrax. Very often, however,
neither any affected animals nor any carcases are available at the time the Veterinary Assistant
Surgeon visits the affected village, so that, not all outbreaks reported as anthrax are microscopically
confirmed. Examination of some 200 outbreaks which occurred during the latter part of the period
after 1940 showed that only about 60 per cent of these were confirmed.
In most parts of Bengal, the cattle owners are not so familiar with anthrax as they have become
with diseases like rinderpest, foot-and-mouth disease, black-quarter and haemorrhagic septicaemia.
Most of them fail to recognize anthrax, especially at the beginning of an outbreak, when even compe-
tent technical officers, and especially those who have had no previous experience of the disease, may
often find it difficult to diagnose correctly from clinical signs alone. It seems probable that anthrax
is often mistaken for other diseases such as haemorrhagic septicaemia, poisoning, snake bite, etc.
Added to these difficulties is the fact that the disease usually occurs sporadically in well-separated
localities.
Many of these points are repeatedly stressed in the annual reports of the Department and, in view
of this, a hundred per cent reliance cannot be placed on the recorded figures.
Seasonal prevalence
In the war against any disease, knowledge of its natural behaviour is always helpful. An im-
portant aspect of this is the season to season variation in its incidence. Moreover, when dealing with
a vaccine, the immunity conferred by which is not expected to last for more than a few months, it
becomes essential to determine at what time of the year the prophylactic inoculations should be
undertaken so that revaccination may not become necessary until the following year.
For securing information about the seasonal prevalence of anthrax in Bengal, records giving
figures of outbreaks in different months in different districts of the Province during the ten year
period from 1937 to 1946 were examined. They were also analysed statistically.
These figures (Tables I and II) have shown that the outbreak incidence curve in Bengal is at a low
point in January. It shows a tendency to rise in February and March, followed by a somewhat
sudden jump to very near the peak in April. The peak is reached during May and June, but during
July and August the curve declines, reaching its almost lowest point of the year in September. Again,
in October and November, there is an upward tendency, before the final decline to the lowest point
of the year in December. Among the different districts, there seems to be no appreciable and signi-
ficant difference in the seasonal behaviour of these outbreaks, beyond some minor irregular varia-
tions.
TABLE I
Monthly incidence of anthrax outbreaks in Bengal during years 1937-1946
Year
Month
January .
February .
March . .
April . .
May . .
June . .
July
. .
August . .
September .
October .
November .
December .
TOTAL .
1937
6
5
6
35
40
29
38
12
10
3
7
3
194
1938
10
8
9
13
27
30
7
7
5
9
5
7
137
1939
3
5
7
31
32
43
22
8
6
1
1
6
105
1940
6
11
8
15
10
11
17
4
2
6
3
4
97
1941
. .
20
8
36
48
32
18
18
1
9
12
2
204
1942
6
5
9
14
12
17
11
5
2
8
5
1
95
1943
4
1
2
2
3
3
10
2
3
..
5
1
36
1944
2
..
5
6
1
5
8
3
..
..
5
1
31
1945
1
..
..
4
3
5
2
1
1
..
..
..
17
1946
2
2
3
3
7
3
..
..
1
..
1
..
22
Total
40
57
57
159
183
178
133
59
31
36
39
26
998