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A differential response to mosquito nets by Anopheles and Culex mosquitoes from Papua New Guinea
958 Tlu~sacrro~s
OF THE ROYAI. SOCIETY OF
A differential
TROPKALMEDICINE
AND
HYGIENE(1986)
80, 958-960
response to mosquito nets by Anopheles mosquitoes from Papua New Guinea
and Culex
J. D. CHARLWOOD* Papua New Guinea Institute of Medical Research, P.O. Box 378, Madang, Papua New Guinea. local mosquito populations, primarily Anopheles kolimsis, An. farad and C&x quinquefasciatus.In the village of Budip, 11 km to the north of the town of Madang, a house was selected in which in one bedroom a young married couple slept under a mosquito net and in an adjoining bedroom of equal size (2.0 x 2.5 m) a couple of adolescent boys slept without nets or any other protection against mosquitoes. Throughout the night hourly searchesof the bedroom walls were undertaken (10 min per room) and all mosquitoes collected. In the ensuing 40 min a landing catch was performed using human bait either out of doors or in another house some 50 m away. After six nights’ collections spaced over a five-week period the two boys were given mosquito nets and collections were made for a further three nights. The results are given in Table 1. The room without nets had significantly more anophelines in it (An. koliensis and An. farautg than did the room in which nets were used. The P values of multiple linear regression analysis comparing the rooms are given in Table 2. The number of blood-fed culicines (mainly C&x quitupef~ciutus) was significantly higher in the room without a net although the total number of culicines in the rooms was not significantly affected by the presence of a mosquito net. There was no sign&ant difference in the numbers of mosquitoes collected from the two rooms once the two boys had
To sleep under a net is perhaps one of the better known ways of avoiding the ‘slings and arrows’ of mosquito bites. With the present breakdown in conventional antimalarial campaigns in many parts of the world there has been a resurgence of interest in so-called alternative control measures. Despite the long advocacy of their use (ROSS, 1910), nets are considered as one such measure. In particular the use of insecticide treated nets as a means of control is receiving a considerable amount of publicity (DARRIET et al., 1984; SCHRECK et al., 1977, 1980). Relatively little is known, however, about the response of mosquitoes to hosts protected by mosquito nets and what level of protection nets provide since mosquitoes can often be seen feeding on peoples’ legs and arms through a net when they inadvertantly lie against it while asleep. In particular it is worth knowing how long a time a female mosquito will spend on the outside of the net trying to get in, since this may determine whether or not a treated net will have any insecticidal effect. A series of experiments was, therefore, undertaken in a coastal village in northern Papua New Guinea in an attempt to determine the effect that the use of mosquito nets has on the successrate of feeding in the * Present address: Department of Medical Entomology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, England. Table l-Numbers Budip Viige
of Anophelesfarauti, An. koliensis and Culex quinquefasciatus collected from the walls of two bedrooms in
Trial 1 (6 nights)
Total Blood Fed Trial 2 (3 nights) Total Blood-fed
Table 2-Multiple without mosquito
Room 1 Without nets
Room 2 With nets
An. farad An. koliemis
C. quinquefasciatus
An. farad An. koliensis
797 597
318 229
157 116
105 50 With nets
With nets
123 53
194 84
linear regression P values of the comparison nets
between the room with mosquito nets in use and the room
Species
Total
Blood-fed
An. farauti An. koliensis C. quinquefasciah4s
0.0022 0.0112 0.0636
0.0108 0.0267 0.0196
J.D. CHARLWOOD
959
a
.
6
6am
6pm Time
Fig. 1. (a) Williams mean (Mw) of numbers of An. kolimis collected biting man indoors (dear) and outdoors (hatched) in nine collections of 40 min per hour in Budip Village. (b) Williams meao (Mw) of numbers of An. kdienrir collected from the walls of a room in Budip Village from 6 collections in which mosquito nets were not in use(clear) and from 9 collections in which nets were used (hatched), 10 mio collection per room per hour.
been given mosquito nets (Table 1). Thus mosquito nets are an effective means of reducing mosquito attacks. The number of An. kolimti collected from the walls of the room without nets showed a similar pattern to the numbers collected in both indoor and outdoor landing catch collections (Fig. 1). It is probable that the numbers entering the rooms were the same, irrespective of whether or not nets were in use, but that the anophelines departed within the hour in search of a blood meal to another house or host. A similar conclusion was reached by ODETOYINBO (1969) and PORT & BOREHAM (1982) concerning the behaviour of An. gambiae in Africa. This result
indicates a difference in behaviour between anophelines and culicines and suggests that insecticide treated nets will be more effective against culicine mosquitoes than against anophelines. They also suggest that, to be effective, the whole population of a village should sleep under nets otherwise those unfortunate enough to sleep unprotected will be bitten by mosquitos diverted from protected hosts. References Darriet, F., Robert, V., The Vien, N. & Camevale,P. (1984). Evaluationof the efficacyof pennethrin-impregnated intact and perforated mosquito nets against vectorsof malaria. W.H.O.MXI84. 899.
RESPONSE
960
TO
NETS
BY
Anopheles
Odetoyinbo, J. A. (1969). Preliminary investigations on the use of a light-trap for sampling malaria vectors in The Gambia. Bulletin of the World Health Organization, 40, 547-560. Port, G. R. & Boreham, P. F. L. (1982). The effectof bed nets on feeding by Anopheles gambiae Giles (Diptera: Culicidae). Bulletin of Entomological Research, 72, 483488. Ross, R. (1910). The prevention of malaria. London : John Murray, 669 pp.
ADVANCED
AND
Culex
IN
PAPUA
NEW
GUINEA
Schreck, C. E., Weidhaas, D. F., Smith, N. & Posey, K. H. (1977). Chemical treatment of wide-mesh net clothing for personal protection against blood-feeding arthropods. Mosquito News, 37, 455-462
Schreck, C. E., Carlson, D. A. Weidhaas, D. E., Posey, K. & Smith, D. (1980). Wear and aging tests with permethrin-treated cotton-polyester fabric. Juurnal of Economic Entomology, 73, 451-453 Accepted
MEDICINE
for publication
5th September, 1985.
CONFERENCE
Royal College of Physicians of London lOth-12th February, 1987 During this Conference one whole day will be devoted to tropical medicine. Those interested in attending should contact: Miss G. Andrew, Royal College of Phykans, I1 St. Andwws Place, London NWI.
OF THE ROYAI. SOCIETY OF
A differential
TROPKALMEDICINE
AND
HYGIENE(1986)
80, 958-960
response to mosquito nets by Anopheles mosquitoes from Papua New Guinea
and Culex
J. D. CHARLWOOD* Papua New Guinea Institute of Medical Research, P.O. Box 378, Madang, Papua New Guinea. local mosquito populations, primarily Anopheles kolimsis, An. farad and C&x quinquefasciatus.In the village of Budip, 11 km to the north of the town of Madang, a house was selected in which in one bedroom a young married couple slept under a mosquito net and in an adjoining bedroom of equal size (2.0 x 2.5 m) a couple of adolescent boys slept without nets or any other protection against mosquitoes. Throughout the night hourly searchesof the bedroom walls were undertaken (10 min per room) and all mosquitoes collected. In the ensuing 40 min a landing catch was performed using human bait either out of doors or in another house some 50 m away. After six nights’ collections spaced over a five-week period the two boys were given mosquito nets and collections were made for a further three nights. The results are given in Table 1. The room without nets had significantly more anophelines in it (An. koliensis and An. farautg than did the room in which nets were used. The P values of multiple linear regression analysis comparing the rooms are given in Table 2. The number of blood-fed culicines (mainly C&x quitupef~ciutus) was significantly higher in the room without a net although the total number of culicines in the rooms was not significantly affected by the presence of a mosquito net. There was no sign&ant difference in the numbers of mosquitoes collected from the two rooms once the two boys had
To sleep under a net is perhaps one of the better known ways of avoiding the ‘slings and arrows’ of mosquito bites. With the present breakdown in conventional antimalarial campaigns in many parts of the world there has been a resurgence of interest in so-called alternative control measures. Despite the long advocacy of their use (ROSS, 1910), nets are considered as one such measure. In particular the use of insecticide treated nets as a means of control is receiving a considerable amount of publicity (DARRIET et al., 1984; SCHRECK et al., 1977, 1980). Relatively little is known, however, about the response of mosquitoes to hosts protected by mosquito nets and what level of protection nets provide since mosquitoes can often be seen feeding on peoples’ legs and arms through a net when they inadvertantly lie against it while asleep. In particular it is worth knowing how long a time a female mosquito will spend on the outside of the net trying to get in, since this may determine whether or not a treated net will have any insecticidal effect. A series of experiments was, therefore, undertaken in a coastal village in northern Papua New Guinea in an attempt to determine the effect that the use of mosquito nets has on the successrate of feeding in the * Present address: Department of Medical Entomology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, England. Table l-Numbers Budip Viige
of Anophelesfarauti, An. koliensis and Culex quinquefasciatus collected from the walls of two bedrooms in
Trial 1 (6 nights)
Total Blood Fed Trial 2 (3 nights) Total Blood-fed
Table 2-Multiple without mosquito
Room 1 Without nets
Room 2 With nets
An. farad An. koliemis
C. quinquefasciatus
An. farad An. koliensis
797 597
318 229
157 116
105 50 With nets
With nets
123 53
194 84
linear regression P values of the comparison nets
between the room with mosquito nets in use and the room
Species
Total
Blood-fed
An. farauti An. koliensis C. quinquefasciah4s
0.0022 0.0112 0.0636
0.0108 0.0267 0.0196
J.D. CHARLWOOD
959
a
.
6
6am
6pm Time
Fig. 1. (a) Williams mean (Mw) of numbers of An. kolimis collected biting man indoors (dear) and outdoors (hatched) in nine collections of 40 min per hour in Budip Village. (b) Williams meao (Mw) of numbers of An. kdienrir collected from the walls of a room in Budip Village from 6 collections in which mosquito nets were not in use(clear) and from 9 collections in which nets were used (hatched), 10 mio collection per room per hour.
been given mosquito nets (Table 1). Thus mosquito nets are an effective means of reducing mosquito attacks. The number of An. kolimti collected from the walls of the room without nets showed a similar pattern to the numbers collected in both indoor and outdoor landing catch collections (Fig. 1). It is probable that the numbers entering the rooms were the same, irrespective of whether or not nets were in use, but that the anophelines departed within the hour in search of a blood meal to another house or host. A similar conclusion was reached by ODETOYINBO (1969) and PORT & BOREHAM (1982) concerning the behaviour of An. gambiae in Africa. This result
indicates a difference in behaviour between anophelines and culicines and suggests that insecticide treated nets will be more effective against culicine mosquitoes than against anophelines. They also suggest that, to be effective, the whole population of a village should sleep under nets otherwise those unfortunate enough to sleep unprotected will be bitten by mosquitos diverted from protected hosts. References Darriet, F., Robert, V., The Vien, N. & Camevale,P. (1984). Evaluationof the efficacyof pennethrin-impregnated intact and perforated mosquito nets against vectorsof malaria. W.H.O.MXI84. 899.
RESPONSE
960
TO
NETS
BY
Anopheles
Odetoyinbo, J. A. (1969). Preliminary investigations on the use of a light-trap for sampling malaria vectors in The Gambia. Bulletin of the World Health Organization, 40, 547-560. Port, G. R. & Boreham, P. F. L. (1982). The effectof bed nets on feeding by Anopheles gambiae Giles (Diptera: Culicidae). Bulletin of Entomological Research, 72, 483488. Ross, R. (1910). The prevention of malaria. London : John Murray, 669 pp.
ADVANCED
AND
Culex
IN
PAPUA
NEW
GUINEA
Schreck, C. E., Weidhaas, D. F., Smith, N. & Posey, K. H. (1977). Chemical treatment of wide-mesh net clothing for personal protection against blood-feeding arthropods. Mosquito News, 37, 455-462
Schreck, C. E., Carlson, D. A. Weidhaas, D. E., Posey, K. & Smith, D. (1980). Wear and aging tests with permethrin-treated cotton-polyester fabric. Juurnal of Economic Entomology, 73, 451-453 Accepted
MEDICINE
for publication
5th September, 1985.
CONFERENCE
Royal College of Physicians of London lOth-12th February, 1987 During this Conference one whole day will be devoted to tropical medicine. Those interested in attending should contact: Miss G. Andrew, Royal College of Phykans, I1 St. Andwws Place, London NWI.