March, 1950]
K.
RANGANATHA
RAO
19
Rabbits and guineapigs
They were injected intraperitoneally with a paraffin oil emulsion of Johne's
bacillus according to the method described by Mohler [1933]. The infective material
consisted of an emulsion of culture of Johne's bacilli in paraffin oil. As indicated by
Mohler, the proportion of the infective material to paraffin oil was 1:2. The dose
employed was 2 c.c. injected intraperitoneally. It was observed that both with
regard to the mortality and the type of lesions produced, the results obtained were
similar to those described by Mohler. Eighty per cent of the infected animals died
at the end of periods varying from seven days to one month. Whereas, the controls
that received either plain paraffin oil or a saline or a saline emulsion of Johne's
bacillus, all remained healthy. It would, however, be difficult to conclude from
these findings that Johne's disease, as we generally understand it, has been reproduced
in these animals especially because it is pointed out by some workers, firstly, that
such infected rabbits and guineapigs do not usually succumb unless the dose of
bacilli is a large one and secondly, that nearly the same type of lesions are obtained
by the intraperitoneal injection with even saprophytic acid-fast bacilli or killed
tubercule bacilli suspended in paraffin oil. So much so, it is suggested that the
lesions are more reaction products than the result of bacterial activity.
DIAGNOSIS
The diagnosis of fairly advanced cases was comparatively simple. The persistant
characteristic diarrhoea which may be intermittant and the progressive wasting of
musculature, particularly of the hind quarters, were prominent symptoms.
Out of 29 cases which were confirmed as positive, post-mortem smears from rectal
mucosa had revealed the bacilli only in nine cases, whereas, the smears of dung were
positive in 28 cases. The dung smears for examination were prepared by emulsify-
ing dung in normal saline and allowing it to stand for ten minutes when it would
separate into three layers, the top layer of lighter pieces of straw, etc. the middle
fluid layer and the bottom layer of sediment. A drop from the intermediate fluid
layer was spread on the slide, dried, fixed and stained in the usual manner for
Johne's bacillus.
The results of allergic test were studied on a lot of 34 animals which were all
examined post-mortem. Correlating the post-mortem result with the allergic tests
it was seen that out of 22 reactors to avain tuberculin, eight, i.e. 36 per cent were
found positive post-mortem whereas, out of 17 reactors to Johnin 11, i.e. 65 per cent
were found positive post-mortem. Again out of 12 non-reactors to avain tuberculin
only eight, i.e. 67 per cent were found negative post-mortem whereas out of 17 non-
reactors to Johnin 16, i.e. 94 per cent were negative post-mortem. Further out
of 12 animals which were confirmed positive for Johne's disease post-mortem, eight
had reacted positively to both Johnin and avian tuberculin and three had reacted
to Johnin only and one was a non-reactor to both. Thus, it is observed that Johnin
was more specific and reliable than avian tuberculin in spotting both positive and
negative cases of Johne's disease in these experiments vide Appendix I.
About five weeks old cultures of M. paratiberculosis grown on the synthetic
medium were employed for the preparation of Johnin. The Lister Institute strain
D 2