392 
PACIFIC SCIENCE, Vol. XIV, October I960 
TABLE 1 
Laboratory Infection of Aedes vigilax with the Fijian Strain of Wuchereria hancroftii 
AND WITH Dirofilaria immitis 
EXPT. 
NO. 
MICROFILARIAE 
PER 20 CMM. 
(MEAN OF 2) 
DISSECTED MOSQUITOS 
Days 
after 
feed 
Total 
No. with live 
larvae (all stages) 
MICROFILARIAE 
1ST STAGE 
2nd STAGE 
EARLY THIRD 
STAGE 
MATURE 
No. 
mosquitos 
Total no. 
microfilariae 
No. 
mosquitos 
Total no. 
larvae 
No. 
mosquitos 
Total no. 
larvae 
No. 
mosquitos 
Total no. 
larvae 
No. 
mosquitos 
Total no. 
larvae 
123 
W . hancroftii 5 
0 
3 
0 
0 
7-8 
4 
0 
0 
9-13 
103 
2 
3 
3 (2d* ) 
2 
2 ( Id) 
124 
17 
2-6 
9 
0 
0 
9-11 
49 
5 
8 
16(d) 
1 
1 
1 
2 
125 
42 
13 
20 
1 
10 
I4(13d) 
126 
241 
13-14 
35 
3 
16 
102 (65d) 
3 
- 7 (3d) 
1 
1 
1 
1 
2 
2 
128 
7 
2-12 
35 
2 
4 
9 ( 6d ) 
1 
2 
13-18 
73 
0 
4 
5(d) 
1 
1(d) 
Dog 
D. immitis 
8-10 
19 
1 
5 
83(d) 
5 
19( I6d) 
11 
uncountable 
15 
10 
1 
1 
6 
17 
5 
4 
4 
11 
Simultaneous feedings with A. pseud os cut ellaris 
125 
W . hancroftii 42 
13 
3 
3 
3 
30 
126 
241 
13 
22 
18 
1 
4 
1 
5 
3 
11 
16 
106 
128 
7 
1-10 
17 
10 
1 
1 
6 
14 
3 
3 
11-13 
- 19 
13 
7 
11 
8 
29 
* d = dead, frequently disintegrating. 
but all mosquitos dissected before the 9th day 
in experiments 123 and 124, and before the 
13 th day in the other experiments, died naturally 
and were dissected the same day. In experiment 
128 both species suffered the effects of humid- 
ities unusually high even for Suva, with con- 
sequent high mortality. 
The results (Table 1) contrast strongly with 
those obtained with a New Caledonian donor 
by Iyengar and Menon (1956) and by Back- 
house and Woodhill (1956). This man showed 
microfilarial counts ranging from 57 to 154 per 
20 cmm. of blood, and infected 94 per cent 
(Iyengar and Menon, 1956) and 95 per cent 
(Backhouse and Woodhill, 1956) of all A. 
vigilax fed on him. Backhouse and Woodhill 
also quote a mature infection rate of 98 per cent 
in those mosquitos dissected from the 12 th day 
onwards. We obtained only 2 mature larvae, in 
different insects, among 35 mosquitos that fed 
on a Fijian with a microfilarial count of 241 per 
cmm. (mature infection rate, 5.7 per cent). Only 
3 (8.6 per cent) of this batch showed live 
filarial larvae, although 82 per cent of A. pseu- 
do scut ellaris fed at the same time carried live 
larvae. Batches of A. vigilax fed on other donors 
with microfilarial counts of 5, 17, 42, and 
seven showed total live infection rates (no 
stage later than the second) of 1.8 per cent, 
8.6 per cent, 5 per cent, and 1.8 per cent, 
respectively. A, pseudo scut ellaris fed on the last 
two showed live infections in 100 per cent and 
64 per cent. It appears that A. vigilax is a poor 
vector of the Fijian strain of W . hancroftii. 
One feed has been done on a dog which was 
anaesthetised with nembutal ( expt. 11). There 
was heavy mortality of the fed mosquitos, only 
five surviving 17 days. Of these, four became 
infective. This high laboratory mortality of 
A, vigilax is most unusual and contrasts with 
a complete survival in experiment 126 made 
about the same time. It is almost certainly due 
to heavy Invasion of the mosquitos 8 excretory 
systems as a result of feeding on this very heavy 
