116
Contagious Abortion of Cattle, Sheep and Goats
[VOL. XVIII, PART III
per annum. In special circumstances, however, major endemics are encountered and here the annual
loss of calves may amount to 20 per cent of breeding stock during a period of several years; happily,
such occurrences are again comparatively rare. Superimposed, or secondary, epidemics are not
uncommon and in these, the loss of calves may amount to 5 to 15 per cent of breeding stock in the
course of a few months.
Continental survey, a general conspectus
Fig. 12 gives an approximate representation of the geographical distribution of Brucellosis in
India.
Most of the organized farms of the country have been visited while from most of the remainder
specimens have been sent to Mukteswar for examination and it has been found that, with very few
exceptions, Indian farms are to a greater or lesser extent infected with Brucellosis. Further, as
the majority of strains isolated from farms have proved to be the pure European type (Br. abortus)
the source of a good part of the infection is attributable to the earlier stock, much of which originated
in Europe. The actual appearance of Brucellosis in these farms, therefore, is of small epidemiological
significance, for, its occurrence is largely fortuitous depending on where the farms happen to be and
the character of their foundation stock.
In the villages, on the other hand, the position is entirely different. Obviously, it has only
been possible to visit a representative few rural areas in each province, but, nonetheless, discoveries
in villages have been of far greater epidemiological interest than those in farms. If it is to be believed,
for instance, that villages have become infected from farms, it would be reasonable to assume that
most village infection would be found adjacent to farms. A glance at Fig. 12 shows that such is
not the case, and indeed, village infection is commonest where farms are fewest and vice versa. More-
over, as is shown on page 47 all Brucella strains, so far isolated from villages, differ in their typing
characteristics from the Br. abortus strains isolated from farms. It would appear, therefore, that
village infection, as seen almost exclusively on the Indian peninsula, has not been imported from
Europe via the farms, but is an indigenous Indian infection, the distribution of which is of the highest
epidemiological significance. Be that as it may, the distribution and persistence of a bacterial
disease is chiefly concerned with microbial dissemination and, not until the section dealing with this
subject is reached, can a hypothesis covering the peculiarities of epidemiology of the disease in village
be preferred.
In the meantime, a few remarks are necessary on some possible inaccuracies of village survey
work. In a country of the utmost conservatism, where there are no laws giving power over live-
stock, and where religion frequently forbids the drawing of bovine blood, to make a serological dia
gnosis on privately owned animals is often impossible. It follows that village blood samples can
only be obtained when the local veterinary staff are able to over-persuade the prejudices of the
people. Furthermore, persuasion usually results in sick, rather than healthy, animals being produced
and consequently cattle with some history of disease (in this case usually genital) are the ones most
frequently bled. When, therefore, it is stated in the succeeding pages that say 45 per cent of animals
tested were Brucella positive, this is not ordinarily a true percentage of all the stock of the village,
but only of those more likely to be infected. Nevertheless, inaccurate though they may be, such
records are the best obtainable and have been found by experience to reflect fairly exactly the
apparent abortion rate in the villages concerned. As to the real abortion rate, in the absence of
records, it is possible only to guess but where Brucella reactors are say upwards of 30 per cent, it
is believed that abortion may occur at the rate of about 10 per cent per annum. The obtaining of
blood samples from slaughter-houses is also often opposed, the chief trouble here being the dis-
inclination of butchers to be put to the slightest inconvenience. However, the returns from tests
of such samples are possibly only a very rough index of the prevalence of abortion in the surround-
ing villages and so the loss of samples of this sort is annoying but hardly calamitous.
Now it must be admitted at once that by far the largest number of village blood tests have been
made in Madras, Orissa and the Central Provinces and Berar, or in other words in the very situa-
tions where village Brucellosis has been most diagnozed (Fig. 12), whilst in the United Provinces,