56
Paratuberculosis of Cattle in Assam
maintained on these farms and the areas of land available for grazing (as
shown in Table IX), it would be seen that every year in which investigation
of this disease was undertaken, the areas of land allotted for grazing was found
very limited in proportion to the number of animals maintained. This factor
also seemed to exercise a powerful influence on the course of intestinal
helminthiasis to which several adult and young stock had succumbed during
these few years.
3. General climatic factors.—Keeping in mind the general climatic condi-
tions of the province already dealt with in a previous section of this paper,
one would be able to judge the extent to which this factor alone would account
for the continuance of the disease amongst the stock of the Government
farms, or even that of the villages where the sources of infection were present.
The significance of the observation [Mukteswar, 1934] that Johne's bacilli
like tuberculosis organism are prone to destruction on prolonged exposure
to sunlight, has been studied under field conditions in connexion with the
epizootology of this disease in Assam. Heavy rainfall and the resultant
humidity in Assam during the whole monsoon period tend to keep alive the
infective organism in the soil for a sufficiently long time. The winter period
in Assam, in spite of its bright sunshine, could hardly be considered as having
any inhibitory effects on the organism of Johne's disease, since the heavy
dewfall which is characteristic of wintry nights in Assam helps to keep the
moisture of the soil for a greater part of the day.
The types of the pasture throughout a greater part of Assam are charac-
terized by the superabundance of herbage all the year round except in winter ;
but even during this period the perennial grasses, although remaining dry,
do not usually lose the superabundance of growth. Thus the factors associat-
ed with the type of climate and the nature of the pastures contaminated with
the excreta of infected animals have the effects of providing necessary mois-
ture and shade to the causative agents of the disease which remained infec-
tive for a greater part of the year, causing several cases of the disease to appear
from time to time.
4. Concomitant diseases.—The infected animals on the Government
farms observed in the course of our investigation could be placed into two
important clinical groups, viz.
(1) those observed in the early part of investigation in which diarrhoea
and debility developed rapidly leading to death after a short
period of illness, and
(2) the confirmed cases of the disease observed during the latter part
of investigation which continued to live for three or four years
without showing any marked deterioration in their general
health.
The probable explanation to this difference in manifestation of the disease
in the two groups of cases lies in the fact that the farm stock during the earlier
period of investigation had a severe infestation with the helminth parasites
to which, as would be seen from Table IX, several animals had already suc-
cumbed.
With the finding of gross helminthic infestation in animals dying of
Johne's disease in which the condition had assumed a comparatively short