S.
GANAPATHY
IYER
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which produced death but the standardization of such vaccine, for safe use in
the field, had not, so far, been possible. Tests with vaccines to set up immunity,
prepared in a manner similar to those prepared by Daubney and Kelser
for rinderpest, were also carried out but the results were irregular. Oral
administration of the virulent material failed to induce immunity. As a
result of continued work with Ranikhet disease, in 1936 it was reported that
of the various kinds of vaccines experimented with, formalized vaccines were
considered most hopeful, but, owing to the irregular reaction following vaccina-
tion, the product could not be released for field use. Considerable success
attended an attempt to immunize fowls by the inoculation of mixtures of viru-
lent tissue emulsion and a solution of saponin. There was, however, consi-
derable variation in the local inflammatory reaction of individual birds in res-
ponse to the saponin injection and a practical standard was not achieved.
Shirlaw [1937] stated that the work on vaccination by virus and serum
mixture gave somewhat doubtful results. A specific antiserum was prepared
by the hyper-immunization of birds which proved resistant to the usual dose
of virus administered under the skin or reacted and recovered from the effects of
the disease. At least 2 c.c. of this serum was required to neutralize 10 M. L. D.
of the dried virus. With the serum-virus mixtures, made from desiccated
virus, only an uncertain degree of immunity could be produced. Certain of the
experimental birds withstood a subsequent test dose of 50 M. L. D. virus.
It appeared, however, that the immunity resulting by this method was only
partial rather than absolute and there was little prospect of success in this
direction.
The action of the influence of light upon the virus was studied, particu-
larly with a view to attenuating the virus and rendering it suitable for use as a
vaccine [Shirlaw, 1937]. Attenuation was attempted by suspending the
virus in graded dilutions of methylene blue and subjecting it to photo-dynamic
inactivation. The method was almost similar to that of Perdrau and Todd
[1933], and yielded no conclusive results with Ranikhet disease virus as the
attenuation of the virus was beset with difficulties peculiar to it, and, under
experimental conditions,' an end-point was reached where the virus was either
fully virulent or inert '.
Several species of birds and animals were injected with the virus with the
hope of attenuating it but the results were unsatisfactory. While pigeons
are susceptible to experimental infection, there is no hope of their being used
in providing a vaccine as in fowl pox, [Doyle and Minett 1927]. The serum of
sheep, healthy or treated with the virus, was shown to have a virucidal effect
but its application under experimental conditions to develop active or passive
immunity was unsuccessful. Farinas [1930] obtained similar results. The
possibility of a modified attenuated virus changing back into its virulent form
should always be considered.
Haddow and Idnani [1941] working with the Indian strain of the virus on
its immunological aspect have had encouraging results in the preparation of a
vaccine by employing the method of adsorption of the virus on alumina gel
and by allowing the mixture to mature at a previously determined temper-
ature. It is encouraging to note that this vaccine is free from any unmodified
virus capable of setting up the disease in contact fowls.