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An Outbreak of Pasteurellosis in ducks
[XVI
Diagnosis. From the course and the nature of mortality, the contagious nature of the disease
was apparent from the beginning. Films of heart blood, liver and spleen from three dead birds at
the height of the disease and from two other that had died an hour earlier showed no bacteria. The
presence of a large number of living trichomonads from the coecal scrapings of two recently dead
birds suggested that these organisms were the cause, but this was not confirmed as no trichomonads
were noticed in other cases.
The liver in two other birds which died a little later were enlarged and congested, and showed
numerous, minute, discrete, whitish, ' necrotic ' foci from pin point to pin head size and sometimes
of an irregular shape. The heart fat in the coronary groves showed petechial haemorrhages. Films
of heart blood and liver of one of these showed a few Pasteurella-like organisms, but from the other
bird smears of heart-blood and liver showed in enormous numbers bipolar organism typical of
Pasteurella septica.
Pathogenicity. About 0.25 c.c. of blood was aspirated into a sterile syringe directly from the
heart of the two latterly autopsied ducks and injected subcutaneously into two fowls. Both the
fowls died within 23 hours ; from them, blood films stained by Leishman method showed large
numbers of typical Past. septica. Liver smears also showed fairly frequent typical Past. septica.
Control. At the time control measures were introduced, only 90 birds were available. These
were divided into three groups to be treated with serum, with vaccine and a control group. Un-
fortunately, the owners insisted that the control should also be treated, so these were given both
serum and vaccine. For these purposes, bovine pasteurella serum and vaccine were used, sub-
cutaneously at the rate of 10 c.c. serum and 1 c.c. vaccine for each bird.
Results. The result of vaccination is shown in Table I. It was hoped to keep the vaccinated
birds quite separate for careful study, but owing to lack of proper supervision on the part of the
owners this plan did not entirely succeed. Post-mortem examination was continued time to time in
birds dying after vaccination. Past. septica was seen in blood films of the dead birds, in small or
large numbers.
TABLE I
Attempted control of Pasteurella outbreak in ducks
No. of
ducks
treated
30
30
30
Product
Pasteurella . .
Pasteurella . .
Pasteurella . .
Serum . . .
Vaccine . . .
Serum and Vaccine .
Number of deaths during post-inoculation
Day
1
3
3
3
2
1
5
1
3
2
3
2
4
4
5
2
5
1
1
2
6
2
2
2
7
1
2
1
8
0
1
0
9-11
0
0
0
TOTAL
Total
14
23
11
48
From Table I it may be seen that the outbreak was under control seven days after inoculation.
Nevertheless, control was not successful since more birds died during the immediate post-inoculation
period. Most of deaths occurred in the vaccine group, next in the serum group, while the sero-
vaccine group showed the lowest mortality. The difference however between the serum group and
the sero-vaccine group was negligible.
SUMMARY
An outbreak mainly, subacute in type, of pasteurellosis in ducks is described. The disease
seemed to have been introduced into the flock by infected ducks. Diagnosis was by microscopical
examination of heart-blood but the organisms could only be selected in the blood of birds in which
the disease was subacute in type. Control measures adopted late in the outbreak had little success