PROTECTIVE INOCULATION WITH DRY PIGEON-POX AND SHEEP AND
GOAT-POX VACCINE
By D. A. MUNRO, Imperial Veterinary Research Institute, Izatnagar
(Received for publication on 6 December 1946)
I N view of the well established efficacy of dry pigeon-pox vaccine for protecting fowls against
fowl-pox, it was considered desirable to test the effectiveness of this method against similar
infections of sheep and goats. The observations which follow throw light on the method of producing
immunity with the use of a dry vaccine on both sheep and goats, as well as on fowls and pigeons.
Amongst the most prominent methods of protective inoculation against variola infections, the one
which has been found most suitable, and is now almost universally practised for the control of goat
and sheep-pox, is the use of a sensitised vaccine as recommended by Bridré and Boquet [1913]. The
conception of this method of prophylactic treatment owed its origin to Besredka's classical findings
in the field of sensitised vaccines. These authors [1933] have since published statistical returns to
show that nearly 25 million doses of the vaccine have been issued from the Pasteur Institute, Algeria,
for use in various countries during the twenty years following its introduction and the results have
been consistently satisfactory not only in so far as judged by the protection conferred on vaccinated
sheep, but also by the degree of safety with which the latter could be allowed to come in contact with
untreated animals.
In India. Viswanathan [1939] in Madras, reports his success in controlling an outbreak of sheep-
pox by inoculating 2.388 sheep with the sensitised vaccine. The results obtained by him in goats,
however, do not appear to have been satisfactory, for he writes: 'Out of .510 goats ovinated two
died with symptoms of goat-pox, 20 developed severe generalized reaction and recovered and in the
rest severe local reaction was present'.
Chadha [1939], in the North-West Frontier Province, tested the value of this method of vaccina-
tion on 77 sheep and found inflammatory reaction on the fifth day, with an elevation of body tempera-
ture 105º-107ºF. In many cases the swellings reached the size of walnuts. The animals, however,
eventually returned to normal health. While the introduction of the sensitised vaccine must be
regarded as having registered a definite advance over the old method of 'ovination', a number of
workers have referred to certain disadvantages of this method. Thus, Kolyali and Mavridis [1934]
in Turkey, refered to the high cost of preparation of this vaccine and to the insufficiency of measures
for its despatch, without loss of potency, to various parts of the country. Angeloff [1934] points
out that the sensitised vaccine cannot be conserved and that, in spite of painstaking aseptic precau-
tions in its preparation, there is a possibility of contaminating organisms developing during prolonged
transit. Moreover it is not the case that animals treated by this method do not exhibit any symptoms.
Thus, Suhaci [1939] states that, out of a total of 16.237 sheep vaccinated by the Bridré and Boquet
method, nearly 73.75 per cent showed symptoms, though the latter were not generalized; 2.4-3.6
per cent of the animals showed nodules and many developed a transient lameness, while some showed
depression and inappetence. Finally, as Bridré and Boquet [1933] themselves have pointed out,
strains of sheep-pox virus vary in potency and this necessitates the use of varying quantities of
serum for neutralizing a given quantity of virus. Kolyali and Mavridis [1934] later used sheep-pox
virus treated with serum in the actual centre of the outbreak—a method which would appear to
bear analogy with the serum-simultaneous method of inoculation against rinderpest. The virus
was diluted in the proportion of 1:10 and four drops of the diluted virus were mixed with 5 c.c. of a
strong anti-serum, these being left in contact for 1½-2½ hours; each animal was inoculated intrader-
mally with 0.25 c.c. of this mixture. Angeloff [1934], who has obtained excellent results with the
simultaneous inoculation, mixed 0.1 gm. of fresh lymph with 10 c.c. of serum and injected 3 to 5 c c.
accordingly to the size of the sheep; the serum and lymph being mixed immediately before the injec-
tion. The drawback of this method, as Angeloff remarks, is that a large quantity of serum has to be
arranged for.
The disadvantages, as indicated above, of using serumised vaccine led the writer to examine the
desirability of reversion, in a suitably modified form, to the prophylactic treatment of sheep and
goats by the use of vaccine alone. Ovination, which at one time was the exclusive method in most
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