88
236. But in regard to public measures of prevention directed against
malaria a great deal has still to be learned and it is often a difficult matter to
convince otherwise well informed people that an open well may be a danger not
only to themselves but to their neighbours. This fact explains in part the
persistence of malaria in Bombay, for the continued existence and spread of the
disease in the City would be impossible, but for the facilities afforded to the
breeding of the carrier, N. slephensi, in wells and other collections of water
which are under the control of the property-owning and educated classes of
the Community.
237. The Effect of Treatment upon the Prevalence of Malaria,—It has
sometimes been supposed that one of the main factors in causing the dis-
appearance of malaria from Great Britain was the gradual adoption of efficient
methods of treatment for the disease ; and there is considerable evidence to support
the view that in proportion as communities make use of quinine and skilled
treatment the disease tends to become less prevalent. Bombay is favourably
situated in possessing a number of medical institutions and also very many
trained physicians and chemists and druggists ; and a large number of cases
of malaria are treated by them every year. Every case of malaria.
adequately treated lessens the chance of the spread of the disease and though
it is not possible to estimate the exact effect which is produced upon the
malaria of the City by the treatment of many thousand cases of infection, there
is little question that it exerts a very strong ameliorating influence. But
there are still a large number of people who are not reached by treatment and
until they are induced to seek it of their own free will or to receive it when
offered, they will remain a danger to the remainder of the population so long as
malaria is uncontrolled by public measures directed against the anopheles
mosquito which carries it.
238. Migration and Malaria in Bombay.—It has been a favourite theory
in Bombay that malaria is an imported disease. No doubt a certain proportion
of those who come into the City every year from the Presidency districts and
other parts of India, carry malaria parasites with them ; but there is no reason
to suppose that a very great amount of infection is imported in this way, The
migration into the City from the more malarious districts of the Presidency is
very small ; there are few immigrants from Sind, Panch Maháls and Kánara
which are probably the most malarious districts ; and neither the Konkan nor
the Deccan as a whole are very malarious.
239. The examination of people newly arrived from their country has
rarely shown evidence of much malaria amongst them, except in the cases of
vagrants, among some of whom enlarged spleen is not uncommon ; whereas
among Bombay born people, such as the Pársis, malaria is common. As has
already been pointed out the spleen index indicates that imported malaria is not a
serious matter in Bombay. The spleen census, conducted in an area including
5/6ths of the island, which harbours 2/3rds of the total population, gave
an index of only 1.9 per cent. ; whereas in the remaining 1/6th of the island to
the south of this, an area which harbours l/3rd of the population, the spleen
index was nearly 15 per cent.
240. But although there is no reason to suppose that much malaria is
imported from without, internal migration from the south to the north of
the island is responsible for a certain amount of the infection present there.
Quite recently many thousand people have been displaced from some of the
malarious localities in the City and there is little question that a proportion of
the enlarged spleens which raise the spleen index of the north of the island to
1.9 per cent. belong in reality to the south of Bombay.
241. The fact that malarial infection cannot spread in the absence of the
carrier of the disease is often overlooked. If every person who entered
Bombay was infected with malaria there could be no spread of the disease if
the comparatively few breeding places of dangerous anopheles were efficiently
controlled.
242. In conclusion it may be pointed out that, there is evidence that the
amount of malaria contracted locally is many times in excess of that introduced
into the island from without ; and there is little question that from the point of
view of malaria prevention the importation of malaria infection into Bombay
may be ignored.