P. G.
PANDE
55
some previous date. It is also to be noted that the same young animals later
improved in condition, and remained in apparent normal health for a consi-
derable period, but on more than one occasion, during the subsequent intervals
when the Avian Tuberculin tests were applied, they had shown a positive res-
ponse. By the time these animals were two years old, they were definitely
diagnosed as cases of Johne's disease either on the result of autopsy or bowel-
washing examination. Clinical symptoms in calves below one year have not
been recognized in the course of our investigation, though the lack of symptoms
in such young animals did not necessarily mean that they were not infected.
Tables II to VI contain the results of the tests performed on a number
of calves ranging in age from six months to a year, from which it will be seen
that a fairly large number of them showed the reaction. Post-mortem evidence
of infection could not, however, be obtained in such young animals.
B. Epizootology
Although Johne's disease is now known to exist in several parts of India
the seriousness with which it has been viewed in Assam would seem to find
a justification in the extent to which the condition had involved valuable
animals of the Government farms and the jail dairies, and in the frequency
with which clinical cases amongst animals issued out and sold to the public
were brought to the notice of, and detected by, the Civil Veterinary Depart-
ment of the province. The possible explanation regarding its unusual
incidence in Assam would have to be sought in factors connected with the
climatic and soil conditions of the province on the one hand, and the farm
and the jail dairy conditions under which the animals were maintained, on the
other. For convenience of description, factors connected with the epizootology
of the disease could be grouped under the following headings :
1. Introduction of infected animals in a clean herd,
2. Overcrowding of available pastures,
3. General climatic factors,
4. Concomitant diseases, and
5. Nutrition.
1. Introduction of infected animals in a clean herd.—Since the detection
of the first case of this disease in India, [ Sheather, 1918 ] all possible attempts
by the Civil Veterinary Department, Assam, at detecting it on autopsy in
indigenous cattle had resulted in failure. The presence of this disease in Assam
was attributed to animals purchased from Sind as the first case was detected
on autopsy in a Sindhi bull of the Khanapara farm which for a long time
acted as the main source of infection to cattle of other Government farms,
jail dairies and private village herds to which animals from this farm were
either transferred, issued or sold.
2. Overcrowding of available pastures.—Overcrowding of the pasture
with animals, however, is a factor the significance of which could hardly be
overlooked in discussing the epizootology of a disease in which diarrhoea and
consequent contamination of the pasture with infective material is the accom-
panying feature. The effects of this factor on the incidence of the disease
have been investigated in the animals of the Government farms at Khanapara
and Sylhet. From the record of figures relating to the number of animals