F.
C.
MINETT
91
Since the position in respect of Coleyana (Figs. 9
to 12) is not so clear, it may be helpful to examine
the figs. in the light of the following remarks.
Fig. 9. Prior to the sharp outbreak begin-
ning on January 31 with 18 cases in five days
the minimum temperature had ranged from
34 to 48°F. During the following monsoon
there were only five cases. (This and other
figures show clearly the sharp fall in air
temperature associated with rain.)
Fig. 10. There were 15 cases between October
and February. On March 6 to 8 there was a
rainfall totalling 1 inch, accompanied by a
sharp fall in temperature , between March 8
to 14, sixteen cases of strangles were admitted.
On June 7 there was 0.3 inch rain, and three
days later 10 cases of strangles were admitted.
During the following monsoon, only one case
appeared.
Fig. 11. Cases first appeared on December
9, there being 14 cases in that month. In
January and February there were 61 cases,
of which 29 were admitted in one day,
February 16. During December to February
minimum temperatures were very low
actually below freezing point from January
14 to 18, followed during the next fortnight
by heavy rainfall. Between the following
May 25 and June 24 there were 21 cases, and
during this period the minimum temperature
fell on several occasions by 14 to 16° F.
within a space of two or three days. A few
cases only occurred during the following
monsoon.
Fig. 12. Five cases appeared in December
and 18 cases within 11 days in January,
after which only three cases developed
during the rest of the year 1936. The
January cases were apparently associated
with minimum temperatures around freezing
point.
DISCUSSION
It will be useful to refer to the position in respect
of diseases of other animals and of man which are
acquired by the respiratory tract. In Britain and
the United States, diphtheria is reported to reach
its greatest intensity in the late autumn and winter,
scarlet fever in the late autumn, winter and spring.
Acute rheumatism, which is probably streptococcal
in origin, has its maximum in winter or spring and
is lowest in summer in temperate countries. Green-
wood and Thompson [1907] found evidence of a
connection between prevalence and dry weather,
but no significant correlation with mean air tempe-
rature in any month. In Britain and the United
States, influenza is highest but declining during the
first half of the year, while measles is at its maxi-
mum in March or April. Small-pox in India has
received much attention from the meteorological
point of view by Rogers [1926] and Russell and
Sundararajan [1928-9]. In most areas this dis-
ease has a tendency to greater prevalence during
the first half of the year, ordinarily reaching its
maximum before the rains and beginning to dimi-
nish after their commencement, and the correla-
tion coefficients are in fact negative and significant
both with rainfall and relative humidity. Some
of the largest small-pox epidemics occur in the low
rainfall areas of North-West and Central India
and of the Deccan plateau and are least severe in
Bengal with its consistently high rainfall. In the
dry areas mentioned, epidemics nearly always
follow a greater or less failure of the south-west
monsoon, accompanied by a comparatively low
humidity. The explanation presumably is that
the survival of the virus is favoured by dry air
[Loosli et al, 1943]. It is well-known that the
common cold and pneumonia are most frequent
during the winter months, the meteorological factor
directly or indirectly responsible for this in adults
being the prevailing low temperature. In the
case of pneumococcus pneumonia of man in India,
Rogers [1925] has shown that its incidence is greater
in the north-western part of the country, which has
as its main climatic characteristics a great diurnal
range of temperature (about 30°F.), a low minimum
(35°F. or less) in the cold season and a low humidi-
ty. From the seasonal point of view, pneumonia is
most prevalent during the dry cold season (No-
vember to February) and next during the dry-hot
season (March to June). One cannot fail to note
the similarity in this respect between pneumonia
in man and strangles in horses. The case is said
to be different with pulmonary tuberculosis in man,
which Rogers [1925, 1] has shown is associated in
Indian jails with high rainfall and high humidity
and also with the direction, steadiness and strength
of the rain-bearing winds. The disease is, there-
fore, especially prevalent in Bengal and the coastal
areas of Orissa, Madras and Bombay.
In the case of animals, it may be noted that
' snuffles '—a respiratory affection of rabbits due to
a Pasteurella—shows a seasonal periodicity, being
most prevalent (in New York State ) in spring,
with a secondary rise in the autumn and a falling
off in the summer [Webster, 1927]. Wide diurnal
fluctuations in temperature raised the incidence
[Webster & Burn, 1927]. The seasonal occurrence
of diseases of domesticated animals in India will
be taken up separately, but there is some evidence
that pneumonia, e.g. of goats and calves, mainly
occurs in winter. As to strangles itself, it has
been possible to obtain the following information.
Major H. Allen, R.A.V.C., in a report dated the
14th June 1923 States ' strangles in 1922-23 season
was raging in Mona during November; December