A lack of imagination is at once one of the
strengths and weaknesses of the British peoples.
Disaster has often to be upon them before they can
be aroused to take measures for defence, when by
vision and forethought it could have been averted.
Only by such vision and action now, can the
disaster be avoided which would follow the
dis-organization of Sanitary Cordons inevitable in
a World War.
I had an opportunity of seeing this on a small
scale during one of the revolutions in Brazil when
non-immune troops were sent to the endemic areas
of the North, in 1926.
Yellow Fever broke out among those troops,
and panic ensued, although Brazil has been
accustomed to that disease for hundreds of years.
During 1925, when I was Director of the
Yellow Fever Campaign in Parahyba do Notre in
Brazil, Small -pox devastated the city, but that was
taken calmly, as it was a regular occurrence, but,
when a few cases of Yellow Fever were introduced
from the outside into a city free of the vector,
Aedes agypti, and therefore safe from spread, the
panic was spectacular.
That was because everyone knew that the
Authorities had, in vaccination, the means to check
and prevent Small -pox, and that it was due to
contact with humans, and willingly submitted to those
Means. Yellow Fever, on the other hand, was a
!MYSTERY" to superstitious people - and most people
are - and considered as a Visitation.
The difference between the comparatively
sparsely populated and immune Brazilian endemic
area and the congested and absolutely non-immune
tropical East, where the Aedes agypti is the
common domestic mosquito and proved vector, is only
one of degree, but of alarming magnitude.
Again, while the control of Aedes agypti is
simple, and the method thoroughly understood and
worked out over years, with complete success in the
West, the East has much more complicated problems.
The ease of .cedes agypti control is due to its
entirely domestic breeding habits, and control of
the habits of the people as regards their water
supply also controls the mosquito, but in the East
there are other mosquitoes not domestic in their
breeding habits but feeding avidly on humans, such
as Aedes Albopictus, which can convey Yellow Fever,
These mosquitoes breed in the jungle and plantation.
It is admitted that, as in the case of
Malarial control, finance is paramount; this is
the case also in Yellow Fever. The financial
requirements of Yellow Fever control in an
entirely Aedes agypti area, s in Brazil, being
concomitant with the modern requirements of a pure
water supply the expense is, in terms of control,
within the sanitary budget.
On the other hand, the expense of controlling
mosquitoes which breed outside houses on waste
land as well as cultivated land would be
It is essential, therefore, that Yellow Fever
never reaches the East.
Carter, in his masterly work ''The Early History
of Yellow Fever" (1931) , has shown how the disease
came with the slave trade from the :'.rest Coast of
Africa to the East Coast and Islands of the Central
and South Americas. The wooden sailing ship of
those days was ideal for the mosquito vector, and
this manner of spread only ceased xith the change
to metal ships.
During the days of slot' sail the mosquito was
the factor that mattered because, once infected,
it could remain alive long enough to infect humans
on arrival at the other side, without the
necessity of transference through man. This will
be explained in detail in another section. Now we
have both fast water, and still faster air transport.
I well remember my thoughts when, at Pernambuco in
February 1926, I saw Major Franco, the Spanish
Aviator, land from Dakar in the first flight across
the Southern Atlantic. Before, the insect alone
,could come, or, as was more usual, man and insect
came together, for man alone would have been dead
or recovered in the time necessary to make the
crossing; now, as a result of air travel, either
or both could come alone or together.
Four years later, although only eight transSouth Atlantic flights had been made, my forebodings'
were unhappily proved right, by the discovery of
A.gambiae in the town of Natal after a severe
outbreak of Malaria. This mosquito, the common
vector in Africa, had never before been in
America and the town of Natal had never before had
an epidemic of Malaria.
Malaria had been present only in the outskirts
and further country, never in the town itself, -due
to the unsuitability of the breeding places for the
native mosquito but A.gambiae found in the town
ideal and preferential breeding pools.
If the Anopheline mosquito, a much less hardy
insect than the medes agypti, could survive
crossing, what was to prevent the spread of Yellow
Fever to the East by the same means?
As will be shown, this has, up until now, been
prevented by rigid sanitary control both of ships
and aeroplanes under international arrangement.
What hope have we that this agreement would be
continued under the disruptive factors in war?
We know from past experience that it would not.
What then can be done? The British Empire,
at least, can do a great deal which at present it
is not doing, and the burden of this Thesis is how
and what to do. During the three years in which
I helped to control Yellow Fever (1923 -1926) in
Brazil my ideal Was to take all Entomological
phenomena seen in the laboratory to the field and
conversely to attempt to elucidate all field
phenomena in the Laboratory.
Many experiments were made and many reports
sent to the International Health Board of the
Rockefeller Foundation, under whose auspices I
was working. Not only was the Entomology of
Aedes agypti studied, but also the Epidemiology
of the disease in relation to the history and
economy of the country.
The International importance of the question
naturally came to be realized, but the opportunity
to see for myself meant years of waiting and many
thousands of miles of travel.
Since that time - 1926 - I have made 5
complete voyages round the world, touched at all
of the large centres of tropical population and
many of the smaller, taken the Diploma of the
London School of Tropical Ledicine, studied the
political and financial situation bearing on the
subject, and finally remained long enough in the
East (Malaya) to find oút by experiment the
relation of my Brazilian findings, as regards the
Aedes agypti, to the conditions there.
From this, I am of the opinion that there is
only one means of controlling Yellow Fever or
preventing it gaining a foothold, and that is by
the time - honoured and proved method of dealing
with the vector in its larval state.
One admits that great advances have been
made in the immunology and serology of the disease
and that protection can be given to a proportion
of those exposed, but in view of the immense
populations which would have to be dealt with in
the East, it would be a mere gesture. There
would seem to have been a tendency to develop the
purely scientific laboratory side of the study
of Yellow Fever to the neglect of control and
field work, which is an art.
The great and original demonstrations of this
art, in Havana and Panama, followed a very scanty
knowledge of the Entomology and Epidemiology of
the disease, but were entirely and finally
successful, and when Noguchi was making his
tragic proto-zoological errors, the disease was
being conquered in the very countries where he
was making them.
The main object of all scientific work is to
understand, to predict, and lastly to control,
but the greatest of these is to CONTROL.