SEPTEMBER, 1948]
JOHN
B.
POLDING
131
As with cows, so with buffaloes there are exceptional rates of abortion. These occur in two
forms, viz., (1) severe epidemics, of which Brucellosis is fairly plainly the cause and (2) exceptional
epidemics appearing mostly in villages, about which little is known. The former are not very
common, but data of two such epidemics are given in Tables XXI and XXII. The latter are
discussed more fully on page 188.
Sheep and Goats
In the five years of the scheme not a single abortion in sheep has on investigation been attribut-
able to Brucellosis, nor can the writer recall a significant incidence of reactors in these animals, either
where abortions were epidemic, or where sheep were in contact with infected cattle. It must be
supposed, therefore, that the susceptibility of Indian sheep to Brucellosis is indeed slight.
The goat, on the other hand, seems to be rather more susceptible, for, although Brucellosis has
not hitherto been diagnosed in cases of clinical abortion amongst village goats, in two old-established
goat farms, this disease has undeniably co-existed with abortions. The specificity of these abortions
has, however, been disputed and their description has consequently been relegated to the section on
non-specific abortion.
Whilst testing in slaughter houses, occasional isolated reactors have been encountered amongst
sheep and goats alike and it is remarkable that these have been occurred only in south India, where
Brucellosis is common in village cattle, viz., of 405 sheep and goats bled in 15 towns of south India,
11 (2.5 per cent) were positive ; of 250 tested in 11 towns of north India, none was positive.
Inextricably entangled as it is with many improperly understood features of disease transmis-
sion susceptibility per se is a most imponderable characteristic and its mensuration on a basis of
rates of abortion and loss of calves is consequently bound to be fraught with inaccuracies. Never-
theless, it is felt, that the foregoing are tolerable estimates of the ordinary liability of Indian cattle
to contract Brucellosis. In an exceptiona environment, any class of stock may behave in an un-
predictable manner and the response of animals to infection by Brucellosis is not likely to be exempt
from such irregularities.
One more point requires mention ; it has been stated in the past that many Punjab goats are
infected with Brucellosis and the infection rate has been variably estimated at from 8 to 60 per cent.
These rates are greatly at variance with themselves and the present findings, but it must be recalled,
that the antigenic instability of rough Brucella strains was not understood until the middle-thirties
of the present century and that the Br. melitensis strains, usually used for testing goats, were almost
always rough. Numerous old records are still in existence, wherein 9/10 of the positive results of
Brucella tests are clearly the outcome of unstable antigens and this supposedly would account for
many former misconceptions. Infection in the goat will be referred to at greater length when the
question of human infection is being considered (page 153).
SECTION III (EPIDEMIOLOGY). THE DISSEMINATION OF BRUCELLOSIS IN INDIA
The roles of climate and hygiene
The channels by which Brucella leave their host are too familiar to deserve discussion in so
prescribed a space as this paper. The point to be noted is that, although, Brucella organisms are
considered obligatory parasites, in favourable circumstances, they will survive and disseminate
outside the host.
In this country, the effects on their survival of sunshine, of high temperatures and of dryness,
on the one hand, and, of humidity, of moderate temperatures, and of reduced sunlight on the other,
can be vividly contrasted in north and south India. In the whole of the north-west, scorching sun-
shine is diurnal from April to October, natural shade is rare, while the annual rainfall is but one inch,
or less. In the south, conditions are reversed, temperatures vary little about the blood heat of cattle,
the atmosphere and the land surface and soil are moist while, not only is natural shade everywhere
C