BRIEF COMMUNICATIONS
Bulletin of the World Health Organization, 55 (6): 765-766 (1977)
Laboratory infection of Anopheles pharoensis with Wuchereria bancrofti F. W. MOSHA 1 & S. A. MAGAYUKA 2
Results As shown in Table 1, 81.6% of the mosquitos A. pharoensis was infected from a donor with a ingested microfilariae. The mean number of microhigh count of W. bancrofti microfilariae. Of the freshly dissected mosquitos, 81.6 % were found to have filariae per mosquito was 12 ± 2.2 (range 1-81). ingested microfilariae, with an average of 12 ± 2.2 The infectivity rate of the mosquitos dissected bemicrofilariae per mosquito. An infectivity rate of tween day 11 and day 15 was 41.9%. The overall 41.9 % was observed in mosquitos dissected between infectivity rate was 15.1 %. The mean number of the eleventh and fifteenth days after feeding. A mean infective larvae per mosquito was 7.6 + 1.2 (range of 7.6 ± 1.2 third-stage larvae was found in infective 1-38). Some 39.6% of the mosquitos survived until mosquitos. Although A. pharoensis has not yet been the tenth day, when infective larvae first appeared in found naturally infected with third-stage larvae of the mouthparts. The cumulative mortality was W. bancrofti, these studies suggest that it is a poten- 60.4% by day 10 and 78.8% by day 13. In noninfected mosquitos (control), the cumulative mortality tial vector of Bancroftian filariasis. rates were 31.9% and 45.6% on days 10 and 13, respectively. Anopheles pharoensis is not known to be a natural vector of Bancroftian filariasis. However, since this Discussion The infectivity rate (41.9%) in A. pharoensis was species readily feeds on man as well as on animals and will frequently come indoors to feed, it can be similar to that observed for Culex pipiens fatigans considered a potential vector of this disease. The (58.6%) that had fed simultaneously on the same present study was designed to see whether an East donor and had been maintained in the same insecAfrican strain of A. pharoensis could support the full tary. However, the cumulative mortality rate was development of Wuchereria bancrofti under labora- only 33.4% in C. p. fatigans on day 10, much lower than the 78.8 % observed in A. pharoensis. The high tory conditions. mortality in A. pharoensis may partly account for its poor vectorial capacity. Smith (1) also noted that Materials and methods wild A. pharoensis in East Africa did not live long Some 575 wild A. pharoensis, collected from the for worms to attain full development. Lake Jipe area of Kenya, were allowed to feed enough Natural infections of developing larvae have been between 21 h 30 and 22 h 00 on a human donor with reported in A. pharoensis (1-5). Infective-stage larvae an average density of 850 microfilariae per 0.1 ml of of Brugia sp. (Bushrod, F., personal communicablood. Seventeen percent of the mosquitos were tion, 1977) and Dirofilaria spp. (6) have been disdissected immediately; the remainder were placed in sected from wild-caught A. pharoensis along the East paper cups, in groups of ten, and held in an insectary African coast. Brengues (7), in West Africa, found maintained at 26°C and 85 % RH. Some cotton wool that experimentally infected A. pharoensis supported soaked in a weak sugar solution was placed in each full development of W. bancrofti. cup. Dead mosquitos were removed from the cups Although A. pharoensis has not yet been found each morning and dissected for filarial worms. Those naturally infected with third-stage larvae of W. banthat remained alive were dissected between the crofti, these studies suggest that it is a potential thirteenth and fifteenth days after feeding. vector of Bancroftian filariasis.
Abstract
1
Research Officer, East African Institute of Malaria and
Vector-Borne Diseases, P.O. Box 4, Amani, United Repub-
lic of Tanzania. 2Senior Technician, WHO/MRC Helminthiasis Research Unit, P.O. Box 950, Tanga, United Republic of Tanzania.
3663
ACKNOWLEDGEMENTS
The authors wish to thank Ms C. Wakoli, Ms J. Elineema, Ms H. Kombo, and Ms A. Mtango for their
-765-
766
BRIEF COMMUNICATIONS
Table 1. W. bancrofti larvae dissected from A. pharoensis each day following an infective blood meal a Days after feeding
Total mosquitos dissected
Mosquitos with
microfilariae No. %
Mosquitos with
sausage larvae No. %
Mosquitos with
infective larvae No. %
0
98
80
81.6
0
0
0
0
1
23
16
69.6
0
0
0
0
2
18
14
77.8
0
0
0
0
3
23
12
52.1
4
17.4
0
0
4
15
2
13.2
9
60.0
0
0
5
45
1
2.2
28
62.2
0
0
6
42
2
4.8
13
31.0
0
40.4 45.7 51.4 59.1 13.2 28.6 7.5 2.7 8.3
0 0
7
52
0
0
21
8 9 10 11 12
35
0
0
16
0
0
18
0
0
0
0
13 14
35 22 38 28 40 37
15
24
0 0 0 0
13 5 8 3 1 2
Total
575
127
0 0 0 0
141
0 0
0
1
2.9
1
13.6
9
23.7 39.3
11
15
37.5
25
67.6
10
41.7
72
a Only those worms at the latest stage of development were counted in mosquitos that had different filarial stages.
technical assistance; and Mr P. Wegesa, Dr J. McMahon, Dr J. Hitchcock, Ms F. Bushrod, and Mr N. Kolstrup for their useful suggestions. REFERENCES
1. SMITH, A. Bulletin of entomological research, 46: 505515 (1955). 2. TAYLOR, A. W. Annals of tropical medicine and parasitology, 24: 425-435 (1930).
3. NEREV-LAMAIRE, M. Annales de parasitologie humaine et comparee, 11: 370-402 (1933). 4. SENEVET, G. Encyclopedie entomologique, 19: 361 (1935). 5. GRJEBINE, A. & BRYGOO, E. R. Memoires de l'Institut scientifique de Madagascar, s&rie E, 9: 291-306 (1958). 6. NELSON, G. S. Journal of helminthology, 33: 233-256
(1959).
7. BRENGUES, J. Memoires O.R.S. T.O.M., No. 79, pp. 264-267 (1975).
Bulletin of the World Health Organization, 55 (6): 765-766 (1977)
Laboratory infection of Anopheles pharoensis with Wuchereria bancrofti F. W. MOSHA 1 & S. A. MAGAYUKA 2
Results As shown in Table 1, 81.6% of the mosquitos A. pharoensis was infected from a donor with a ingested microfilariae. The mean number of microhigh count of W. bancrofti microfilariae. Of the freshly dissected mosquitos, 81.6 % were found to have filariae per mosquito was 12 ± 2.2 (range 1-81). ingested microfilariae, with an average of 12 ± 2.2 The infectivity rate of the mosquitos dissected bemicrofilariae per mosquito. An infectivity rate of tween day 11 and day 15 was 41.9%. The overall 41.9 % was observed in mosquitos dissected between infectivity rate was 15.1 %. The mean number of the eleventh and fifteenth days after feeding. A mean infective larvae per mosquito was 7.6 + 1.2 (range of 7.6 ± 1.2 third-stage larvae was found in infective 1-38). Some 39.6% of the mosquitos survived until mosquitos. Although A. pharoensis has not yet been the tenth day, when infective larvae first appeared in found naturally infected with third-stage larvae of the mouthparts. The cumulative mortality was W. bancrofti, these studies suggest that it is a poten- 60.4% by day 10 and 78.8% by day 13. In noninfected mosquitos (control), the cumulative mortality tial vector of Bancroftian filariasis. rates were 31.9% and 45.6% on days 10 and 13, respectively. Anopheles pharoensis is not known to be a natural vector of Bancroftian filariasis. However, since this Discussion The infectivity rate (41.9%) in A. pharoensis was species readily feeds on man as well as on animals and will frequently come indoors to feed, it can be similar to that observed for Culex pipiens fatigans considered a potential vector of this disease. The (58.6%) that had fed simultaneously on the same present study was designed to see whether an East donor and had been maintained in the same insecAfrican strain of A. pharoensis could support the full tary. However, the cumulative mortality rate was development of Wuchereria bancrofti under labora- only 33.4% in C. p. fatigans on day 10, much lower than the 78.8 % observed in A. pharoensis. The high tory conditions. mortality in A. pharoensis may partly account for its poor vectorial capacity. Smith (1) also noted that Materials and methods wild A. pharoensis in East Africa did not live long Some 575 wild A. pharoensis, collected from the for worms to attain full development. Lake Jipe area of Kenya, were allowed to feed enough Natural infections of developing larvae have been between 21 h 30 and 22 h 00 on a human donor with reported in A. pharoensis (1-5). Infective-stage larvae an average density of 850 microfilariae per 0.1 ml of of Brugia sp. (Bushrod, F., personal communicablood. Seventeen percent of the mosquitos were tion, 1977) and Dirofilaria spp. (6) have been disdissected immediately; the remainder were placed in sected from wild-caught A. pharoensis along the East paper cups, in groups of ten, and held in an insectary African coast. Brengues (7), in West Africa, found maintained at 26°C and 85 % RH. Some cotton wool that experimentally infected A. pharoensis supported soaked in a weak sugar solution was placed in each full development of W. bancrofti. cup. Dead mosquitos were removed from the cups Although A. pharoensis has not yet been found each morning and dissected for filarial worms. Those naturally infected with third-stage larvae of W. banthat remained alive were dissected between the crofti, these studies suggest that it is a potential thirteenth and fifteenth days after feeding. vector of Bancroftian filariasis.
Abstract
1
Research Officer, East African Institute of Malaria and
Vector-Borne Diseases, P.O. Box 4, Amani, United Repub-
lic of Tanzania. 2Senior Technician, WHO/MRC Helminthiasis Research Unit, P.O. Box 950, Tanga, United Republic of Tanzania.
3663
ACKNOWLEDGEMENTS
The authors wish to thank Ms C. Wakoli, Ms J. Elineema, Ms H. Kombo, and Ms A. Mtango for their
-765-
766
BRIEF COMMUNICATIONS
Table 1. W. bancrofti larvae dissected from A. pharoensis each day following an infective blood meal a Days after feeding
Total mosquitos dissected
Mosquitos with
microfilariae No. %
Mosquitos with
sausage larvae No. %
Mosquitos with
infective larvae No. %
0
98
80
81.6
0
0
0
0
1
23
16
69.6
0
0
0
0
2
18
14
77.8
0
0
0
0
3
23
12
52.1
4
17.4
0
0
4
15
2
13.2
9
60.0
0
0
5
45
1
2.2
28
62.2
0
0
6
42
2
4.8
13
31.0
0
40.4 45.7 51.4 59.1 13.2 28.6 7.5 2.7 8.3
0 0
7
52
0
0
21
8 9 10 11 12
35
0
0
16
0
0
18
0
0
0
0
13 14
35 22 38 28 40 37
15
24
0 0 0 0
13 5 8 3 1 2
Total
575
127
0 0 0 0
141
0 0
0
1
2.9
1
13.6
9
23.7 39.3
11
15
37.5
25
67.6
10
41.7
72
a Only those worms at the latest stage of development were counted in mosquitos that had different filarial stages.
technical assistance; and Mr P. Wegesa, Dr J. McMahon, Dr J. Hitchcock, Ms F. Bushrod, and Mr N. Kolstrup for their useful suggestions. REFERENCES
1. SMITH, A. Bulletin of entomological research, 46: 505515 (1955). 2. TAYLOR, A. W. Annals of tropical medicine and parasitology, 24: 425-435 (1930).
3. NEREV-LAMAIRE, M. Annales de parasitologie humaine et comparee, 11: 370-402 (1933). 4. SENEVET, G. Encyclopedie entomologique, 19: 361 (1935). 5. GRJEBINE, A. & BRYGOO, E. R. Memoires de l'Institut scientifique de Madagascar, s&rie E, 9: 291-306 (1958). 6. NELSON, G. S. Journal of helminthology, 33: 233-256
(1959).
7. BRENGUES, J. Memoires O.R.S. T.O.M., No. 79, pp. 264-267 (1975).
