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Laboratory observations on the toxicity of Swartzia madagascariensis (Leguminosae) extract to mosquito larvae
460 TRANSACTIONS OF THE
Laboratory
ROYALSOCIETY or TROPICAL MEDICINE ANDHYGIENE
observations on the toxicity of Swartzia madagascariensis (Leguminosae) extract to mosquito larvae J. N. MINJAS AND R. K. SARDA Faculty of Medicine, Muhimbili Medical
Dept. of ParasitologylEntomology,
Dar es Salaam,
The development of insecticide resistancein arthropod vectors of tropical diseases coupled with the increased costs of synthetic insecticides and increased public concern over environmental pollution necessitate a continued searchfor alternative, cheaper, vector control methods which require little or no sophisticated technology, but give excellent results. It is against this background that we report observations on the mosquito larvicidal properties of a crude water extract of the fruit pods of Swartzia madagascariensis, a common tree in many parts of tropical Africa (BRENAN, 1967). Table I-Susceptibility Swarti
(1986), 80, 460-461
Centre, P.O.
BOX 65011,
Tanzania Ae. aegvpti was less susceptible than An. gambiae. No mortality was observed with C quinquefasciatus at the concentrations tested. Water from a small pond treated with the powder at about 5 g/l lost its larvicidal activity against An. gambiae by about 30 hours after treatment. S. madagascariensis is widely used in Africa for its medicinal value. The pods are used to stupefy fish and the leaf has been shown to have molluscicidal properties (WATT & BREYER-BRANDWIJK,1962). The fruit is known to contain saponins but human
of three mosquito larval species to diierent
concentrations of crude extracts of
madagascariensis after 24 hours continuous exposure
2.00
MosquitoesKonc. g/l
1.00
0.50
0.25
0.10
0.0
Exft.
$$
o
2
75
0
x
0
0
-
0
Aedes aegypti
:
3:
100
iit
~~
5;
1
8
Anopheles gambiae (s.1.)
:
75 75
100 100
El
100
2 1
0 0
75
100
100
t:
:
Culex quinquefasciatus
i
Mean portalit% (Oh) _
100 1;
95 93
o
’ numbers of larvae tested in 3 replicates Dry fruit pods were obtained from Ifakara, Tanzania, Specimens of the plant material are deposited at the Traditional Medicine Research Unit Herbarium, Muhimbili Medical Centre, Tanzania. Whole pods were crushed into a powder, weighed amounts of this were shaken vigorously in known volumes of distilled water to produce suspensions with different concentrations. These suspensions were kept at room temperature for at least one hour before they were used. Third and early fourth instar larvae of Anopheles gambiae (sensulate) and C&x quinquefasciatus,freshly collected from the field, were used for the tests. Aedes aegypti from a colony that has been maintained in our laboratory for several years were also used. The three mosquito species were tested simultaneously in the first two experiments but subsequently only Anopheles gambiae were tested. 25 larvae of each species were put in 250 ml of the test suspensions in glass beakers at 23 + 2°C. Mortality readings were taken after 24 hours exposure to treatment. Results are shown in Table I. An. gambiae was highly susceptible to the extract with over 90% mortality rates at a concentration of 0.25 g of the powder per litre.
toxicity is considered to be low (SANDBERG,1958). Our observations indicate that aqueous extracts of the pods are highly toxic at reasonably low concentrations to larvae of An. gambiae, an important vector of malaria and rural Bancroftian filariasis in Africa. There seemsto be a potential? after further studies, for its use against this mosqmto species. It is cheap and effective but not-persistent, and the pods keep well and can easily be used at the village level with a minimum instruction and do not require the expenditure of foreign exchange. Our preliminary observations also show that the extract is active against the snail Bulinus nasutus. This molluscicidal action would clearly be an additional advantage in areaswhere schistosomiasisis endemic. Studies are under way to isolate and characterize the active ingredients and the differential susceptibilities exhibited by the mosquito species clearly merit further investigations. We are grateful to Dr. M. Tanner, formerly of the Swiss Tropical Institute Field Laboratory, Ifakara, Tanzania, for supplying us with the pods.
J.
N.
MINJAS
AND
References Brenan, J. I’. M. (1967). Leguminosae, Subfamily Caesalpinioideae. In: Flora of Tropical East Africa. MilneRedhead, E. & Polhill, R. M. (Editors). London: Crown Agents for Overseas Governments, pp. 218-220. Sandberg, F. (1958). The saponins of Swumia madagascari&s. Phamaceutische Weekblad, 93, 5-7.
R.
K.
SARDA
Watt, J. M. & Breyer-Brandwijk, M. G. (1962). The Medicinal and Poisomus Plants of Sot&m and Eastern Afica. London: E. & S. Livingstone Press, pp. 649-651.
Accepted
for publication 22nd August, 1985.
New Fellows Elected-20th February, 1986 Agarwal, A. K., India Agrawala,
M., India
Alluri, R. K. R., India Alqasaf, F. K., Kuwait Anis, M. H., Egypt Assiri, F. A., Kuwait Banda, J. S., Zambia Banerlee, J. D., India Baptista, J. L., Portugal Behrens, R., Britain Bhattacharyya, A. C., India Blaxter, M. L., Britain Browne, E. N. L., Nigeria Bruns, Sheila, M., Britain Climie, A. J., New Zealand Cooper, E. S., Britain Costa, J. M., Portugal Cranston, P. S., Britain Crompton, D. W. T., Britain Das, A. C., India Das, G. C., India Das, H., India Das, M. N., India Ekwueme, K. O., Nigeria Ellis, J. T., Britain Gale, K. R., Britain Gantait, A. K., India Ghatak, B., India Garuai, M. W., Papua New G Gillespie, S. H., Britain Goyot, P., France Gupta, R. K., India Habteyesus, B. K., Ethiopia Haddad, I., Syria Ibrahim, M. M., Kuwait Ishaq, Md., Pakistan Iqbal., A., Pakistan Kammjolo, J. S., Malawi Kassim, 0. P., USA
461
Kennedy, M. W., Britain Knell, A. J., Britain Kuijlen, K., Tanzania Lindsay, S. W., The Gambia Llanos-Cuentas, E. A., Peru Macfarlane, Sarah B. J., Britain Mandal, S. K., India Masterton, R., Britain Medley, G. F., Britain Mukhopadhyay, P. K., India Mzige, A. A., Tanzania Nair, S., Tanzania Ndanusa, Y. A., Tanzania Njie, A., Tanzania Nunn, P., Britain Odugbesan, O., Nigeria Okelo, G. B. A., Kenya Pa$o;l,CCa Thailand Piehhe,“S., Italy Ram, s. i., Pakistan Recuts. S. F. K.. Colombia Roy, P., India ’ Roychowdhuri, S., India Sakiman, B. S., Indonesia Saracco, A., Italy Sen, T. B., India Simlai, A. K., India Singh, H. B., India Syed, S. I., Saudi Arabia Tandon, P. K.. India Todwel& M. A:, USA Trees, A. J., Britain
Vernberg, W. B., USA Waggy, N. S., USA Whitworth. 1. A. G.. Britain Williams, P.-Anne, USA Woo, Jean, Hong Kong
Laboratory
ROYALSOCIETY or TROPICAL MEDICINE ANDHYGIENE
observations on the toxicity of Swartzia madagascariensis (Leguminosae) extract to mosquito larvae J. N. MINJAS AND R. K. SARDA Faculty of Medicine, Muhimbili Medical
Dept. of ParasitologylEntomology,
Dar es Salaam,
The development of insecticide resistancein arthropod vectors of tropical diseases coupled with the increased costs of synthetic insecticides and increased public concern over environmental pollution necessitate a continued searchfor alternative, cheaper, vector control methods which require little or no sophisticated technology, but give excellent results. It is against this background that we report observations on the mosquito larvicidal properties of a crude water extract of the fruit pods of Swartzia madagascariensis, a common tree in many parts of tropical Africa (BRENAN, 1967). Table I-Susceptibility Swarti
(1986), 80, 460-461
Centre, P.O.
BOX 65011,
Tanzania Ae. aegvpti was less susceptible than An. gambiae. No mortality was observed with C quinquefasciatus at the concentrations tested. Water from a small pond treated with the powder at about 5 g/l lost its larvicidal activity against An. gambiae by about 30 hours after treatment. S. madagascariensis is widely used in Africa for its medicinal value. The pods are used to stupefy fish and the leaf has been shown to have molluscicidal properties (WATT & BREYER-BRANDWIJK,1962). The fruit is known to contain saponins but human
of three mosquito larval species to diierent
concentrations of crude extracts of
madagascariensis after 24 hours continuous exposure
2.00
MosquitoesKonc. g/l
1.00
0.50
0.25
0.10
0.0
Exft.
$$
o
2
75
0
x
0
0
-
0
Aedes aegypti
:
3:
100
iit
~~
5;
1
8
Anopheles gambiae (s.1.)
:
75 75
100 100
El
100
2 1
0 0
75
100
100
t:
:
Culex quinquefasciatus
i
Mean portalit% (Oh) _
100 1;
95 93
o
’ numbers of larvae tested in 3 replicates Dry fruit pods were obtained from Ifakara, Tanzania, Specimens of the plant material are deposited at the Traditional Medicine Research Unit Herbarium, Muhimbili Medical Centre, Tanzania. Whole pods were crushed into a powder, weighed amounts of this were shaken vigorously in known volumes of distilled water to produce suspensions with different concentrations. These suspensions were kept at room temperature for at least one hour before they were used. Third and early fourth instar larvae of Anopheles gambiae (sensulate) and C&x quinquefasciatus,freshly collected from the field, were used for the tests. Aedes aegypti from a colony that has been maintained in our laboratory for several years were also used. The three mosquito species were tested simultaneously in the first two experiments but subsequently only Anopheles gambiae were tested. 25 larvae of each species were put in 250 ml of the test suspensions in glass beakers at 23 + 2°C. Mortality readings were taken after 24 hours exposure to treatment. Results are shown in Table I. An. gambiae was highly susceptible to the extract with over 90% mortality rates at a concentration of 0.25 g of the powder per litre.
toxicity is considered to be low (SANDBERG,1958). Our observations indicate that aqueous extracts of the pods are highly toxic at reasonably low concentrations to larvae of An. gambiae, an important vector of malaria and rural Bancroftian filariasis in Africa. There seemsto be a potential? after further studies, for its use against this mosqmto species. It is cheap and effective but not-persistent, and the pods keep well and can easily be used at the village level with a minimum instruction and do not require the expenditure of foreign exchange. Our preliminary observations also show that the extract is active against the snail Bulinus nasutus. This molluscicidal action would clearly be an additional advantage in areaswhere schistosomiasisis endemic. Studies are under way to isolate and characterize the active ingredients and the differential susceptibilities exhibited by the mosquito species clearly merit further investigations. We are grateful to Dr. M. Tanner, formerly of the Swiss Tropical Institute Field Laboratory, Ifakara, Tanzania, for supplying us with the pods.
J.
N.
MINJAS
AND
References Brenan, J. I’. M. (1967). Leguminosae, Subfamily Caesalpinioideae. In: Flora of Tropical East Africa. MilneRedhead, E. & Polhill, R. M. (Editors). London: Crown Agents for Overseas Governments, pp. 218-220. Sandberg, F. (1958). The saponins of Swumia madagascari&s. Phamaceutische Weekblad, 93, 5-7.
R.
K.
SARDA
Watt, J. M. & Breyer-Brandwijk, M. G. (1962). The Medicinal and Poisomus Plants of Sot&m and Eastern Afica. London: E. & S. Livingstone Press, pp. 649-651.
Accepted
for publication 22nd August, 1985.
New Fellows Elected-20th February, 1986 Agarwal, A. K., India Agrawala,
M., India
Alluri, R. K. R., India Alqasaf, F. K., Kuwait Anis, M. H., Egypt Assiri, F. A., Kuwait Banda, J. S., Zambia Banerlee, J. D., India Baptista, J. L., Portugal Behrens, R., Britain Bhattacharyya, A. C., India Blaxter, M. L., Britain Browne, E. N. L., Nigeria Bruns, Sheila, M., Britain Climie, A. J., New Zealand Cooper, E. S., Britain Costa, J. M., Portugal Cranston, P. S., Britain Crompton, D. W. T., Britain Das, A. C., India Das, G. C., India Das, H., India Das, M. N., India Ekwueme, K. O., Nigeria Ellis, J. T., Britain Gale, K. R., Britain Gantait, A. K., India Ghatak, B., India Garuai, M. W., Papua New G Gillespie, S. H., Britain Goyot, P., France Gupta, R. K., India Habteyesus, B. K., Ethiopia Haddad, I., Syria Ibrahim, M. M., Kuwait Ishaq, Md., Pakistan Iqbal., A., Pakistan Kammjolo, J. S., Malawi Kassim, 0. P., USA
461
Kennedy, M. W., Britain Knell, A. J., Britain Kuijlen, K., Tanzania Lindsay, S. W., The Gambia Llanos-Cuentas, E. A., Peru Macfarlane, Sarah B. J., Britain Mandal, S. K., India Masterton, R., Britain Medley, G. F., Britain Mukhopadhyay, P. K., India Mzige, A. A., Tanzania Nair, S., Tanzania Ndanusa, Y. A., Tanzania Njie, A., Tanzania Nunn, P., Britain Odugbesan, O., Nigeria Okelo, G. B. A., Kenya Pa$o;l,CCa Thailand Piehhe,“S., Italy Ram, s. i., Pakistan Recuts. S. F. K.. Colombia Roy, P., India ’ Roychowdhuri, S., India Sakiman, B. S., Indonesia Saracco, A., Italy Sen, T. B., India Simlai, A. K., India Singh, H. B., India Syed, S. I., Saudi Arabia Tandon, P. K.. India Todwel& M. A:, USA Trees, A. J., Britain
Vernberg, W. B., USA Waggy, N. S., USA Whitworth. 1. A. G.. Britain Williams, P.-Anne, USA Woo, Jean, Hong Kong