172
Diro-filaria repens Infestation of Dogs
about 5.78µ. The tail end of the microfilaria
tapers like a whip lash and its movements are of
graceful serpentine character. There is no sheath,
and no tongue like process is thrown out periodi-
cally as in microfilaria bancrofti. The micro-
photograph of the stained preparations brings out
very clearly the absence of a sheath, the character
of the granules, the arrangement of the vacuole,
nerve rings, etc. According to Fülleborne [Panda,
1932 ], it is practically impossible to distinguish
the microfilaria of immitis from the repens variety,
except by the dimensions of the larva. The
average length of the Dirofilaria immitis is 243.9µ,
while that of repens varies from 300 to 375µ.
It will be seen from this that the microfilaria
seen in the blood of the dogs caught in Bombay
belongs to the repens type. It might be men-
tioned here that one other type of microfilaria
was met with in the blood of one dog. It is
being further studied.
Periodicity of microfilaria. Since the object
of this investigation was to find out whether the
spleens of these animals contained nodules similar
to those found in the human beings, it was decided
to ascertain whether the microfilaria of the infest-
ing species showed any periodicity as in the case
of Wuchereria bancrofti. The blood of a positive
dog was examined five times during the course
of the day and the number of microfilaria con-
tained in 20 c.mm. of blood was determined.
From the ear vein of the dog, the above quantity
of blood was aspirated and then discharged on a
slide over which a broad rectangular coverslip
was placed. It was allowed to rest, so that the
movements of the microfilaria were slowed. The
wet-film was examined from one end to the other
and the microfilaria were counted. Tables II
and. III give the result of examinations on two
dogs carried out on three successive days.
TABLE II
Count of microfilaria per 20 c.mm. of blood
Day
16-3-42 . .
17-3-42 . .
18-3-42 . .
Total . . .
Average .
Time
6 A. M.
17
16
12
45
15
10 A.M.
7
11
2
20
6
2 P.M.
9
22
38
69
23
6 P.M.
55
50
42
147
49
10 P.M.
36
84
30
150
50
TABLE III
Day
16-6-42 .
17-6-42 .
18-6-42 .
19-6-42 .
Total .
Average .
Time
2 A.M.
. .
28
48
49
125
42
6 A.M.
. .
30
22
42
94
31
10 A.M.
41
35
21
. .
97
32
2 P.M.
29
32
54
. .
115
38
6 M.P.
90
68
105
. .
263
88
10 P.M.
45
87
93
. .
225
75
In the second case the blood was examined at
2 A.M. in addition to the times mentioned in
Table I.
From these tables it will be seen that the lowest
counts are obtained at about 10 A.M. and towards
the evening the count goes on increasing from 6 to
10 P.M.
It is remarkable to note that between 5 P.M. and
6 P.M. the count of microfilaria jumps up to double
its original value. The figures given in Table IV
are from counts made from a dog on three alter-
nate days.
TABLE IV
Count of microfilaria per 20 c.mm. of blood
Day
23-6-42 . . . . .
25-6-42 . . . . .
27-6-42 . . . . .
Total .
Average .
Time
5 P.M
68
49
77
198
65
6 P.M.
123
101
170
394
131
This indicates that there is a definite periodicity
of the microfilaria in the case of Dirofilaria repens.
Out of the nine dogs which showed the presence
of microfilaria in the peripheral blood, in the first
dog the subcutaneous tissue was not examined,
as at that time the possibility of repens being
the frequent type was not thought of. Of the
remaining eight positive dogs five showed the
presence of adult worms.
Autopsy. The positive dogs were killed and a
complete autopsy was held. A careful examina-
tion of the heart and the pleural cavities was made
in order to find out whether worms of immitis
type could be recovered. In none of the nine
positive dogs, it was possible to get that species.
The spleens of the animals were carefully ob-
served to see if any nodules resembling those
found in human beings were met with. In none
of the animals were such nodules to be noticed.