Larvicidal effect of disinfectant soap on Anopheles gambiae s.s (Diptera: Culicidae) in laboratory and semifield environs
© Mdoe et al.; licensee BioMed Central Ltd. 2014
Received: 17 January 2014
Accepted: 30 April 2014
Published: 3 May 2014
Mosquito larval control using chemicals and biological agents is of paramount importance in vector population and disease incidence reduction. A commercial synthetic disinfectant soap was evaluated against larvae of Anopheles gambiae s.s. in both laboratory and semi field conditions.
Five concentrations of commercial synthetic disinfectant soap (0.0001, 0.001, 0.01, 0.1 and 1%) were prepared and evaluated against third instar larvae in laboratory and semi field environments. Mortality was scored at 12, 24, 48, and 72 hrs. Each dosage had 6 replicates, having twenty 3rd instar larvae of An.gambiae s.s.
In the laboratory phase, all dosages had significantly higher larval mortalities than in controls, while in semi field conditions, the dosages of 0.0001, 0.001 and 0.01% had lower mortalities than laboratory trials. In the comparison between semi field and laboratory trials, only 0.1 and 1% dosage had significant difference with more mortality in semifield conditions. Proportions of larvae that died during mortality monitoring intervals in laboratory and semi field had significant differences only at 12 hrs and 72 hrs.
The findings of this study have demonstrated that the mortality of larvae caused by commercial synthetic disinfectant soap is worth further studies in open water bodies. More studies are necessary to find out the effect of sunlight on the chemistry of the synthetic disinfectant and other variables in small scale full field trials.
The anthropophilic malaria vector, Anopheles gambiae s.s is the most efficient vector in sub-Saharan Africa . Control measures such as long lasting insecticide treated bed net (LLINs) and indoor residual spray (IRS) have been successful in reducing malaria disease burden [2, 3]. Currently the spread and rise of insecticide resistance have jeopardized the efficacy of these tools [4–8]. Increasing vector control efforts targeting larval sources is of high priority as larvae are relatively immobile compared to adult mosquitoes [9–12]. Controlling mosquitoes using larviciding has shown a great impact in larval mortality in field situations . Environmentally friendly compounds with high larval mortality effect are currently needed. Due to environmental concerns about the safety of pesticides, the interest of revisiting the use of insecticidal soap has been raised. Fleas, ticks and cockroaches are among arthropods significantly controlled by the use of disinfectant soap . Some of these soaps formulations have proved to be effective on cockroach mortality . Abbasi and others demonstrated the efficiency of commercially available disinfectant soaps against crickets and cockroaches . The use of soap in insect control is among the “old days methods” , though the utilization of antibacterial soaps have not been screened against insect pests, mostly An. gambiae s.s. Further efforts are needed for the investigation of soaps and detergents for control of mosquito larvae of different species in human dwellings structures including in swimming pools and septic tanks.
The objective of this study was to determine mosquito larvicidal activity of commercially available synthetic disinfectant soap against An. gambiae s.s in both laboratory and semi field environments.
Mosquitoes originated from a colony of An. gambiae s.s established from Kisumu Kenya in 1992 and were reared at the tropical pesticides Research Institute (TPRI). Laboratory rearing of larvae was as described in other protocols [17, 18]. In the insectary larvae were fed with tetramin fish food at rate of 0.003gm/larvae. Third instar larvae were used for trials as recommended in WHO protocol . The photo phase in the insectary was 12Light: 12Darkness (12 L: 12D) with a temperature of 27 ± 2 °C and Relative humidity of 78 ± 2%.
Larval bioassays in insectary
Five concentrations of commercial synthetic disinfectant soap were prepared; 1, 0.1, 0.01, 0.001, and 0.0001%. The stock solution was made using distilled water. Experimental solutions were obtained through serial dilutions. Serial dilutions were made as described in the WHO larval bioassay protocol . Small bowls with diameter of 14 cm, depth 10 cm, and a capacity of 250mls were used as microcosms during experiments. Each replicate had a total of twenty larvae. All five concentrations above had an effect on mortality and were considered for laboratory bioassays. Mortality data were recorded at 12, 24, 48 and 72 hours after experimental set up for both control and treatments. The moribund larvae were considered dead.
Semi field larval bioassays
The disinfectant soap used was liquid soap often used for domestic cleaning. It includes triclosan (Irgasan), 97% granular, as the active ingredient purchased from Sigma- Aldrich (St. Louis, MO, AC abstract 3380-34-5). It was once evaluated against larvae of Cx. quinquefasciatus mosquitoes and proved to have a lethal effect .
Percentage mortality was corrected by abbot’s formula . Analysis of variables (ANOVA) was used to calculate the mean percentage mortality and standard error in different concentration and hours. Chi-square test was used to calculate the statistical significant difference between the proportions of larvae that died in control and treatment groups and also the proportion that died in the hours between control and treatment. Data analyses were performed with Statistical programme for social scientist (SPSS) version 18.0 for windows (SPSS Inc, Chicago, IL).
Larvicidal effect of different disinfectant soap dosages on Anopheles gambiae s.s in laboratory and semi field conditions for treatment and control
% Mortality (Mean ± SE)
% Mortality (Mean ± SE)
3.1 ± 3.1
3.8 ± 2.4
10.6 ± 7.9
2.5 ± 2.5
13.8 ± 9.4
5.0 ± 2.9
57.7 ± 2.4
2.5 ± 1.4
93.3 ± 6.7
7.5 ± 2.5
0.00 ± 0.00
6.3 ± 1.3
0.00 ± 0.00
0.00 ± 0.00
0.6 ± 0.4
2.5 ± 1.4
83.3 ± 11.8
7.5 ± 2.5
97.3 ± 2.7
11.3 ± 3.8
Larval mortality in treatment (water treated with disinfectant soap) and control on Anopheles gambiae s.s in laboratory and semi field conditions within different monitoring hours
% Mortality (Mean ± SE)
% Mortality (Mean ± SE)
14.67 ± 14.67
0.00 ± 0.00
27.83 ± 19.60
2.00 ± 2.00
43.17 ± 21.67
6.00 ± 1.87
57.17 ± 18.07
9.00 ± 1.00
27.8 ± 18.1
2.0 ± 1.2
36.7 ± 22.6
7.0 ± 2.5
40.2 ± 24.4
8.0 ± 2.0
40.3 ± 24.4
9.0 ± 1.9
Semi field bioassays
In semi field bioassays there was no mortality in low dosages of 0.0001 and 0.001, while in 0.01% mortality was 0.6% which was low and had no results when a chi-square test was used to compare treatment and control results. The mean mortalities were statistically higher in treatment than in control (Table 1). The proportion of larvae that died in each time interval was significantly higher in treatment than in control (Table 2).
Comparison of laboratory and semi field bioassays of disinfectant soap
The findings of this study have shown that at low dosages of 0.1% and 1% mortalities of 93.3 and 97.3% in the laboratory and semi field respectively were observed. Most of these disinfectant soaps contain alkyls, chlorides and alcohols which do not show significant larvicidal activity against mosquito larvae but only when application is made in higher dosages .
Our results have shown that, larval mortality was dosage dependant for disinfectant soap against An. gambiae s.s, which was similar to what was found in Cx. quinquefasciatus by Subra and others . In the laboratory all dosages had significant larvicidal impact relative to control. The same dosages in a semi field environment had induced mortality only in the two highest dosages of 0.1 and 1%. The low dosages of 0.0001 up to 0.01% had no appreciable larvicidal effect in a semi field environment. This might have been attributed by the exposure of disinfectant soap under sunlight which might have broken it down into secondary metabolite products which had low toxicant effect, but higher dosages such as 1% could still show higher mortality. A similar scenario was observed when low dosages of Schinus terebinthifolia (radii) could not show larvicidal effect on An. gambiae s.s in semi field conditions . However, in monitoring mortality, the semi field results showed higher mortality at an earlier monitoring time of 12 and 24 hrs while in the insectary it was in 48 and 72 hrs. The semi field results might be attributed to degradation of the chemical structure of compounds hence causing no larvicidal effect with further degradations of compounds into secondary metabolites. In the laboratory the rate of degradation is low for active ingredients hence higher mortality effects are noticed throughout monitoring time. This trend was similar to the findings in other screened larvicides [11, 24]. An. gambiae are surface biofilm feeders, which might have been attributed to the observed reduced mortality while Ae. Aegypti and Cx. quinquefasciastus are bottom feeders, which causes them to feed on high amounts of synthetic disinfectant . Based on this feeding behaviour, the previous findings had higher mortality in bottom feeders than observed An.gambiae s.s mortalities. This might be attributed with the sedimentation of the particles at the bottom that could increase mortality in bottom feeding species than it could for surface biofilm feeders where concentrations of the disinfectant soap is decreasing with time.
The main active ingredient of the disinfectant soap evaluated for larvicidal activity on An. gambiae s.s was triclosan. This product has shown a significant insecticidal activity against cockroaches [14, 15] and scape insects  and ticks . Currently, there are two reported findings which have shown insecticidal activity of soap products against mosquitoes .
The results of the current study on disinfectant soap containing triclosan had 3.1 to 93.3% mortality in the laboratory and 0.0 to 97.3% in semi field evaluation. These results are by margin lower than previous trials with Cx. quinquefasciastus using the same disinfectant. Understanding of disinfectants for effective larvicidal outcome on An. gambiae s.s is of priority for larval control.
The domestic disinfectant soaps have proved to have low eco-toxicological impact and have been shown to be safe for domestic insect control . The study conducted by Xue and Qualls has shown that, the domestic soap with triclosan had increased mortality effects on mosquitoes compared to previous studies which did not include triclosan as active ingredient . The most important part of the research is to understand the effect of triclosan to non-targeted organisms in larval habitats.
The need of new and innovative methods for mosquito control is currently increasing due to high insecticide resistance in disease vector mosquitoes [4–8] and behavoural changes due to control tool implementation . To increase the process of shrinking malaria and vector populations, the targeted sources reduction is of priority. Development of larvicides and screening of their bioefficacy is important for effective control. Screening for better larvicides is ongoing in different parts of malaria and non-malaria endemic regions [11, 24].
The findings of this study have demonstrated that the mortality of larvae shown by disinfectant soap is worth for further studies in open water bodies. More studies have to find out the effect of sunlight and other variables in semi field before small scale field trials. Other mosquito species should be included in further trials.
Authors would like to thank Adrian Massawe and Ester Lyatuu for mosquito rearing and trial monitoring. We thank The Tropical Pesticides Research Institute (TPRI) for provision of infrastructure to support this study. Magreth F. Shayo is acknowledged for her critical comments and improvement of this manuscript. This manuscript is published with the permission of TPRI Director General.
- Coetzee M, Craig M, le Sueur D: Distribution of African malaria mosquitoes belonging to the Anopheles gambiae complex. Parasitol Today. 2000, 16: 74-77. 10.1016/S0169-4758(99)01563-X.View ArticlePubMedGoogle Scholar
- Sovi A, Azondekon R, Aikpon R, Govoetchan R, Tokponnon F, Agossa F, Salako A, Oke-Agbo F, Aholoukpe B, Oke M, Gbenou D, Massougbodji A, Akogbeto M: Impact of operational effectiveness of long-lasting insecticidal nets (LLINs) on malaria transmission in pyrethroid-resistant areas. Parasit Vectors. 2013, 6: 319-10.1186/1756-3305-6-319.PubMed CentralView ArticlePubMedGoogle Scholar
- Tokponnon F, Aholoukpe B, Denon E, Gnanguenon V, Bokossa A, N'guessan R, Oke M, Gazard D, Akogbeto M: Evaluation of the coverage and effective use rate of long-lasting insecticidal nets after nation-wide scale up of their distribution in Benin. Parasit Vectors. 2013, 6: 265-10.1186/1756-3305-6-265.PubMed CentralView ArticlePubMedGoogle Scholar
- Chareonviriyaphap T, Bangs M, Suwonkerd W, Kongmee M, Corbel V, Ngoen-Klan R: Review of insecticide resistance and behavioral avoidance of vectors of human diseases in Thailand. Parasit Vectors. 2013, 6: 280-10.1186/1756-3305-6-280.PubMed CentralView ArticlePubMedGoogle Scholar
- Cornet S, Gandon S, Rivero A: Patterns of phenoloxidase activity in insecticide resistant and susceptible mosquitoes differ between laboratory-selected and wild-caught individuals. Parasit Vectors. 2013, 6: 315-10.1186/1756-3305-6-315.PubMed CentralView ArticlePubMedGoogle Scholar
- Nardini L, Christian R, Coetzer N, Koekemoer L: DDT and pyrethroid resistance in Anopheles arabiensis from South Africa. Parasit Vectors. 2013, 6: 229-10.1186/1756-3305-6-229.PubMed CentralView ArticlePubMedGoogle Scholar
- Aizoun N, Aikpon R, Gnanguenon V, Oussou O, Agossa F, Padonou G, Akogbeto M: Status of organophosphate and carbamate resistance in Anopheles gambiae sensu lato from the south and north Benin, West Africa. Parasit Vectors. 2013, 6: 274-10.1186/1756-3305-6-274.PubMed CentralView ArticlePubMedGoogle Scholar
- Lol J, Castellanos M, Liebman K, Lenhart A, Pennington P, Padilla N: Molecular evidence for historical presence of knock-down resistance in Anopheles albimanus, a key malaria vector in Latin America. Parasit Vectors. 2013, 6: 268-10.1186/1756-3305-6-268.PubMed CentralView ArticlePubMedGoogle Scholar
- Mereta S, Yewhalaw D, Boets P, Ahmed A, Duchateau L, Speybroeck N, Vanwambeke S, Legesse W, De Meester L, Goethals P: Physico-chemical and biological characterization of anopheline mosquito larval habitats (Diptera: Culicidae): implications for malaria control. Parasit Vectors. 2013, 6: 320-10.1186/1756-3305-6-320.PubMed CentralView ArticlePubMedGoogle Scholar
- Walker M, Winskill P, Basanez M-G, Mwangangi J, Mbogo C, Beier J, Midega J: Temporal and micro-spatial heterogeneity in the distribution of Anopheles vectors of malaria along the Kenyan coast. Parasit Vectors. 2013, 6: 311-10.1186/1756-3305-6-311.PubMed CentralView ArticlePubMedGoogle Scholar
- Kweka E, Senthilkumar A, Venkatesalu V: Toxicity of essential oil from Indian borage on the larvae of the African malaria vector mosquito, Anopheles gambiae. Parasit Vectors. 2012, 5: 277-10.1186/1756-3305-5-277.PubMed CentralView ArticlePubMedGoogle Scholar
- Munga S, Vulule J, Kweka E: Response of Anopheles gambiae s.l. (Diptera: Culicidae) to larval habitat age in western Kenya highlands. Parasit Vectors. 2013, 6: 13-10.1186/1756-3305-6-13.PubMed CentralView ArticlePubMedGoogle Scholar
- Nartey R, Owusu-Dabo E, Kruppa T, Baffour-Awuah S, Annan A, Oppong S, Becker N, Obiri-Danso K: Use of Bacillus thuringiensis var israelensis as a viable option in an Integrated Malaria Vector Control Programme in the Kumasi Metropolis, Ghana. Parasit Vectors. 2013, 6: 116-10.1186/1756-3305-6-116.PubMed CentralView ArticlePubMedGoogle Scholar
- Abbasi SA, Nipaney PC, Soni R: Soap solution as an environmentally safe pesticide: For household insects–A preliminary investigation. Comp Physiol Ecol. 1984, 9: 46-48.Google Scholar
- Szumlas DE: Behavioral responses and mortality in German cockroaches (Blattodea: Blattellidae) after exposure to dishwashing liquid. J Econ Entomol. 2002, 95: 390-398. 10.1603/0022-0493-95.2.390.View ArticlePubMedGoogle Scholar
- Moore WS, Profita JC, Koehler CS: Soaps for home landscape insect control. Calif Agric. 1979, 33: 13-14.Google Scholar
- Balestrino F, Benedict MQ, Gilles JR: A new larval tray and rack system for improved mosquito mass rearing. J Med Entomol. 2012, 49: 595-605. 10.1603/ME11188.View ArticlePubMedGoogle Scholar
- Tchuinkam T, Mpoame M, Make-Mveinhya B, Simard F, Lélé-Defo E, Zébazé-Togouet S, Tateng-Ngouateu A, Awono-Ambéné H-P, Antonio-Nkondjio C, Njiné T, Fontenille D: Optimization of breeding output for larval stage of Anopheles gambiae (Diptera: Culicidae): prospects for the creation and maintenance of laboratory colony from wild isolates. Bull Entomol Res. 2011, 101: 259-269. 10.1017/S0007485310000349.View ArticlePubMedGoogle Scholar
- WHO: WHO/CDS/WHOPES/GCPP/2005. Guidelines for laboratory and field testing of mosquito larvicides. 2005, Geneva: World Health OrganisationGoogle Scholar
- Kitau J, Pates H, Rwegoshora TR, Rwegoshora D, Matowo J, Kweka EJ, Mosha FW, McKenzie K, Magesa SM: The effect of Mosquito Magnet Liberty Plus trap on the human mosquito biting rate under semi-field conditions. J Am Mosq Control Assoc. 2010, 26: 287-294. 10.2987/09-5979.1.View ArticlePubMedGoogle Scholar
- Xue RD, Qualls WA: Larvicidal activity of synthetic disinfectants and antibacterial soaps against mosquito, Culex quinquefasciatus (Diptera: Culicidae). J Med Entomol. 2013, 50: 137-139. 10.1603/ME12092.View ArticlePubMedGoogle Scholar
- Abbott WS: A method of computing the effectiveness of an insecticide. J Med Entomol. 1925, 18: 265-266.Google Scholar
- Subra R, Service MW, Mosha FW: The effect of domestic detergents on the population dynamics of the immature stages of two competitor mosquitoes, Culex cinereus Theobald and Culex quinquefasciatus Say (Diptera, Culicidae) in Kenya. Acta Trop. 1984, 41: 69-75.PubMedGoogle Scholar
- Kweka E, Nyindo M, Mosha F, Silva A: Insecticidal activity of the essential oil from fruits and seeds of Schinus terebinthifolia Raddi against African malaria vectors. Parasit Vectors. 2011, 4: 129-10.1186/1756-3305-4-129.PubMed CentralView ArticlePubMedGoogle Scholar
- Kweka E, Zhou G, Beilhe L, Dixit A, Afrane Y, Gilbreath T, Munga S, Nyindo M, Githeko A, Yan G: Effects of co-habitation between Anopheles gambiae s.s. and Culex quinquefasciatus aquatic stages on life history traits. Parasit Vectors. 2012, 5: 33-10.1186/1756-3305-5-33.PubMed CentralView ArticlePubMedGoogle Scholar
- Patrican LA, Allan SA: Application of desiccant and insecticidal soap treatments to control Ixodes scapularis (Acari: Ixodidae) nymphs and adults in a hyperendemic woodland site. J Med Entomol. 1995, 32: 859-863.View ArticlePubMedGoogle Scholar
- Gomes B, Sousa C, Vicente J, Pinho L, Calderon I, Arez E, Almeida A, Donnelly M, Pinto J: Feeding patterns of molestus and pipiens forms of Culex pipiens (Diptera: Culicidae) in a region of high hybridization. Parasit Vectors. 2013, 6: 93-10.1186/1756-3305-6-93.PubMed CentralView ArticlePubMedGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.