258
Streptococcus Mastitis in Buffaloes
The total weekly yield in lb. for each of the
animals is shown in Table V. It may be seen that
the total yield of the ten animals for the week pre-
ceding vaccination was 699 lb., for the week follow-
ing the first inoculation 680 lb., and for the week
after the second inoculation 732 lb. From these
results it was concluded that vaccination would
have no appreciable effect on milk yield.
TABLE V
Effect of two subcutaneous inoculations of streptococcus
vaccine on the milk yield of buffaloes
Buffalo No.
1
2
3
4
5
6
7
8
9
10
Total yield .
First
week
81
54
90
43
63
71
73
50
91
83
699
Milk yield (in lb.)
Fi rst dose of vaccine inoculated
Second
week
71
53
87
43
72
63
86
32
98
75
680
Second dose of vaccine inoculated
Third
week
98
42
113
36
72
56
90
39
112
74
732
Vaccination of non-infected animals
One hundred and fifteen non-infected animals
kept on Farm 1 were available for experiment;
52 of these, selected purely at random, were vacci-
nated and 63 were left as controls. The vaccinated
animals received two doses of vaccine subcutaneously
at an interval of seven days. The first dose con-
sisted of 5.0 c.c. suspension standardized to No. 1
of the Wellcome Opacity Tubes and the second of
5.0 c.c. suspension ten times as dense, i.e. the doses
were half those used in the initial test of the vaccine.
A day or two prior to vaccination milk samples
from all animals were examined for streptococci.
Approximately four months after vaccination milk
samples were again examined. The results are
recorded in Table VI from which it may be seen
that nine (17.3 per cent) of the vaccinated animals
and eight (12.7 per cent) of the controls had become
infected. The difference of 4.6 per cent in favour
of the controls is not statistically significant since
it is only 0.7 times its standard deviation.
It may safely be concluded therefore that vaccina-
tion had been without effect as a means of preventing
streptococcal mastitis.
TABLE VI
Efficacy of vaccination as a means of preventing
streptococcus mastitis in buffaloes
—
Vaccinated
Control
TOTALS
Positive
9 (17.3 per cent)
8 (12.7 per cent)
17
Negative
43
55
98
Total
52
63
115
Difference=4.6 per cent
S.E.=6.6
Vaccination of infected animals
In addition to the 115 non-infected animals,
there were also available 38 infected animals; of
these, 17 were vaccinated and 21 were left as controls.
From Table VII it can be seen that 10 (58.8 per cent)
of the vaccinated and 10 (47.6 per cent) of the control
animals were negative four months later. The
difference of 11.2 per cent in favour of the vaccinated
is not statistically significant. It may be noted
incidentally that the finding that about 50.0 per
cent of animals positive at one test are negative at a
subsequent test is in accordance with results obtained
previously.
TABLEVII
Efficacy of vaccination as a means of curing
streptococcus mastitis
—
Vaccinated
Control
TOTALS .
Positive
7
11
18
Negative
10 (58.8 per cent)
10 (47.6 per cent)
20
Total
17
21
38
Difference= 11.2 per cent
S.E.=16.3
It was concluded from this experiment that
vaccination had not led to any cure.
Eradication
Anticipating that vaccination would be useless,
experiments on eradication were carried out on
farms 1 and 3 concurrently. The experiments were
designed to test the efficacy of partial eradication
and also that of a more thorough eradication.
Partial eradication
On Farm 1 there were six sheds of animals. Three
of these were already in the vaccination experiment.