290
Johne's Disease
hay or grass and a little concentrate mixture (crushed gram, wheat bran, oil
cake and salt). The roughage was fed on the floor of the sheds. Water
was supplied from an iron tank filled from a stream running down the hill-
side and during the early part of the experiment drainage water from the
sheds was also allowed to run into the tank. The cleaning of the sheds and
of the outside enclosure was purposely not thorough and the floor of the sheds
became slushy at the time of the rains and snow. All calvings took place
in the same sheds, along with other animals. It was thought that these
conditions in the sheds would give the infection every chance of spreading
to the healthy animals, but it will be observed that the animals in other res-
pects led a very natural life, were given a reasonably adequate maintenance
ration and were not subjected to any physical strain, except at the time of
calving. From time to time, the animals were tested by the double intra-
dermal method with ordinary tuberculin and with avian tuberculin. Both
tuberculins were prepared from glycerol broth cultures and were used in the
heat-concentrated form. Finally, in April 1940, a test was made with ordi-
nary tuberculin and Johnin, in both cases ammonium sulphate precipitated
products from synthetic media and prepared in the Medical Research Council
Laboratories, Mill Hill, England. From time to time also rectal smears and
bowel washings were examined in a further attempt to locate infected animals.
All animals which died or were destroyed were examined for Johne's disease
by making microscopical preparations from the bowel wall, particularly
from the terminal portion of the ileum and from the ileo-caecal valve. At
the conclusion of the experiment selected animals were slaughtered and
attempts made to cultivate Johne's bacilli on a liver extract-phlei-egg medium:
COMPOSITION OF THE HERD
The herd has been gradually built up of (a) naturally infected cattle
from outside, and (b) healthy cattle, and its numbers have been augmented
by the progeny of these two groups of animals. Breeds represented were :
Tharparkar, Hissar, Bihar, Assamese, Sindhi and cross-bred. The size of
the herd increased from 3 in August 1929 to 110 in April 1940, when the experi-
ment was closed. [Although the total number of animals passing through
the herd has been stated as 110, only 95 are mentioned in Appendices 1 and
2, the remainder having either died or been killed as calves by wild animals.]
In August 1929 there were purchased from Bihar three naturally infected
cows (Nos. 1, 2 and 3), all three being typical cases of Johne's disease in which
acid-fast organisms could be easily demonstrated in rectal smears and faeces.
The animals reacted to avian but not to ordinary tuberculin. Two of these
cows (Nos. 2 and 3) died a few months later in spite of treatment with formalin
and Johne's bacilli were isolated from both of them. The third cow (No. 1)
attained good condition and ceased to react to avian tuberculin, although
rectal smears were teeming with acid-fast organisms resembling Johne's
bacilli. She died in May 1931 of Johne's disease.
A second batch of 9 cows (Nos. 4-10, 61 and 62), 1 calf (No. 11) and 2
bullocks (Nos. 12 and 13) were received from Bihar in 1930. All these animals,
as well as cows 1, 2 and 3, were accommodated temporarily in a shed in the