J. P. POLDING
155
TABLE XII
Comparison of environments in farms 2 and 3
Environment
Climate . . . . . . . .
Disposal of animals
.
.
.
.
.
.
Source of infection . . . . . .
Result . . . . . . . . .
Farm 2
Sunny and dry . . .
Congested . . . .
Great
.
.
.
.
.
No epizootic .
.
.
.
Farm 3
Overcast and humid
Congested
Ample
Panzootic
This comparison surely suggests that in buffaloes at least rainfall plays a considerable part in
the dissemination of brucellosis.
This and many other similar records lead to the same conclusion and it is tempting to accept
the simple explanation that at least among buffaloes a fluid vehicle is more satisfactory for dissemina-
tion than a dry one. In this respect the buffalo's habit of wallowing requires consideration. Observa-
tions on this habit have been recorded by Minett [1947]. In north India at least buffaloes wallow
voluntarily from April to October and there is a natural desire to do so when the air and water tem-
peratures are above 85° and 77°F. respectively. The desire to wallow is intense during hot damp
months, August and September in north India. During the hot dry period of April to June, water
is short and the few available shrunken tanks and ponds are grossly congested, while during the
rains, the animals are dispersed over a far wider expense of water.
If therefore it can be accepted that the sterilizing effect of sunlight, which is admittedly great
for Brucella, can suppress the contagion during the sunny months, then increased infection of buffaloes
during the rains, despite wider dispersion, might be partially accounted for by wallowing, especially
when this is done in tanks.
Many epidemiologists have associated moisture with the spread of diseases. Rogers [1926],
for example, found that cholera spreads as the absolute humidity reaches 0.4 in. and it may be noted
in passing that, in lower Bengal and on the Coramandal and Malabar coasts (i.e., in the Brucella-
endemic areas of India) the absolute humidity is never below 0.4 in. About Brucella little has been
proffered, but Cameron [1932], who has tested fairly thoroughly the viability of Brucella, shows on
the whole that drying is harmful to the organism.
SUMMARY
The results of a survey of brucellosis in India have been analysed in an effort to trace some of
the factors which control the spread of the disease in that country.
The scatter of the disease amongst farms was uniform and thus uninformative. On the other
hand, an indigenous enzootic among village cattle occurred throughout the bi- and tri-seasonal rain-
fall areas only.
The incidence of infection in farms was often high where total rainfall was high, and vice versâ.
The rate of village infection was negligible in semi-desert areas but considerable in humid coastal
belts.
It is concluded that the sterilizing effect of continuous sunlight is paramount in checking dissemina-
tion of the disease, while humidity, rainfall and sunlessness are favourable to its spread. Neverthe-
less, unhygienic conditions and congestion of animals play an important part in transmission.
Abortion statistics are given for European zebu crossbreds, for pure zebus, and for buffaloes.
The susceptibility of these animals and of sheep and goats is assessed.
REFERENCES
Cameron, H.S. (1932). Cornell Veterinarian. 14, 16
Minett, F.C. (1947). J. Animal Sci. 6, 35
Rogers, L. (1926). Proc. Roy. Soc. Med. 19, 59
B