128
Contagious Abortion of Cattle, Sheep and Goats [ VOL. XVIII, PART III
random animals. They are obtained by multiplying the mean expectation of loss of calves per
aborting animal [Table X column 7] by the mean expectation of unrepeated abortion during the
lifetime of 100 random animals [Table IX]. If the smallest figure is taken as unity, the relative
susceptibility of zebu, co-habiting zebu, and crosses is found to be as 1 : 2.5 : 7. In future, figures
so obtained will be alluded to as the susceptibility index the figure for the zebu being, in all cases,
regarded as unity.
Some findings suggest, either that the susceptibility of Indian cows to Brucellosis is decreasing,
or that a better knowledge of the disease in relation to animal management is limiting its spread.
For example, the reports of the military farms (northern circle) from 1932 to 1939 show a progres-
sive annual decrease in the abortion rate ; a decrease which runs parallel with improvements in hous-
ing and management. On the other hand, since 1939 there have been indications that, in the busier
farms at least, the rate has again increased and this has coincided with the unavoidable lessened
attention and over-crowding due to the wartime emergency and expansion. It seems probable,
therefore, that good management, rather than reduced susceptibility, was the cause of the earlier
decrease ; nevertheless—although this seems the less likely explanation—the whole episode may
be the result of phasic variations in susceptibility. Another illustration of decreasing incidence of
Brucellosis is to be found in the Punjab Grantee farms. In the year 1923 the mean abortion rate,
calculated from a single random observation of five of these farms, was 3 per cent of 1264 animals,
whilst at later visits, in 1939, the figure had fallen to 1 per cent of 835 animals.
It must be noted that all the animals considered in the foregoing two paragraphs are kept under
somewhat similar circumstances and that their standards of life are good, many of the pure-bred
zebu herds in particular, being kept under semi-ranch conditions, in a favourable climate.
Exceptionally severe epidemics of abortion occasionally occur, even in non-cohabiting zebu and
Tables XV and XVI give data about one such outbreak. The farm in question lies in a favourable
climate and was formerly a typical Pinjrapole. Lately, however, it has been developed commercial-
ly and better stock was purchased, unfortunately from Bombay city dealers. Bombay city is a
reservoir of Brucellosis and, as in other cases, this epidemic appears to have been introduced by the
abortion of these purchases. Unhappily no records are kept in such institutions and the reliability
of this data is dependent on the memory of the stockman, whose statements, nevertheless, were
sufficiently supported by test and cross-enquiry to be credible. If in these circumstances the annual
abortion rate during the period of this epidemic may be assessed at a conservative 25 per cent, the
susceptibility index of this herd works out at 11.1, or nearly double the average for cross-breds. That
the abortion was due to Brucellosis, seems to be proved by the fact that 95 per cent of the aborted
animals were strongly Brucella positive.
TABLE XV
The abortion rate during exceptional Brucella epidemic among indigenous cows
Year
1941 . . . . . . . . . . . .
1942
.
.
.
.
.
.
.
.
.
.
.
.
Not known, believed 1942 . . . . . . . .
Total breeding
stock
(approximate)
50
50
50
Number of
aborters
16
9
16
Abortions
Per cent
32
18
32
Breeding herd total at the time of observation 1943
.
.
.
.
.
.
.
.
Total aborters at the time of observation . . . . . . . . . . .
Total aborters per cent at the time of observation . . . . . . . . . .
52
40
77