Modern bed bugs are resistant to multiple insecticide classes, particularly the pyrethroids. The efficacy of pyrethroid-impregnated mattress liners marketed for bed bug management has been variable. This study evaluated the efficacy of a permethrin-impregnated mattress liner, ActiveGuard, against 24 bed bug strains, consisting of both Cimex hemipterus (F.) and Cimex lectularius L. A 'mat assay', employing an allethrin-impregnated mat, was used to establish the pyrethroid resistance profile of all strains. Three experiments were conducted to evaluate the effect of ActiveGuard exposure on bed bug knockdown: 1) exposing the bed bugs continuously on the liner for up to 24 d, 2) holding the bed bugs on the liner for either 4 or 6 h, and 3) placing a noninsecticide treated fabric above the liner with the bed bugs held continuously on top. Our results indicated that all modern strains (collected within the last 15 years during the current resurgence) were pyrethroid-resistant, although the magnitude of resistance was highly variable between strains. In the continuous exposure study, an incomplete knockdown was recorded for most modern bed bug strains, with some having no knockdown even up to 7 d of constant exposure. In the 4 or 6 h exposure study, the level of knockdown was reduced even further, and very few bed bugs were knocked down in the double fabric study. The results of this study indicate that pyrethroid-impregnated mattress liners are not likely to be effective in the management of most modern bed bug infestations involving either C. hemipterus or C. lectularius.
Field trials were conducted in two residential areas of Petaling Jaya Municipality to test the adulticidal and larvicidal effects of malathion 96% TG and Resigen on Aedes aegypti. Malathion is the currently used insecticide in Malaysia for the control of dengue. The Leco HD ULV machine was used throught the trials. For malathion the flow rate was 90 ml/minute at a vehicle speed of 8kph and for Resigen the flow rate was 200 ml/minute at the same vechicle speed. Malathion was more effective giving higher mortality rates when compared with Resigen. The mortality rate of adult Ae. aegypti outdoor was higher than in the living room and kitchen. Both insecticides did not show promising larvicidal effects.
Comparative field efficacy studies of four mosquito coil formulations containing active ingredient of d-allethrin (0.19 or 0.28 w/w) and d-transallethrin (0.12 or 0.16% w/w) and blank coils without active ingredient were carried out in living rooms (mean size 54.1 m3) of residential houses in a squatter area in Butterworth, Malaysia. The major indoor biting mosquitos collected in the test site were that of Culex quinquefasciatus Say (84.7%). Mean percentage reduction of blank coils, coils with 0.19 and 0.28% d-allethrin and coils with 0.12 and 0.16% d-transallethrin were 29.0, 71.7, 70.9, 75.0 and 72.6%, respectively. The use of coils as a mean of personal protection against mosquitos is discussed.
Use of mosquito coils for personal protection against malaria and mosquito nuisance is advocated under mosquito and malaria control programmes. We performed field studies of mosquito coils containing either metofluthrin or esbiothrin in experimental huts situated in Kamhororo village, Gokwe district, Zimbabwe. All tests were performed on 3-5 day old reared female Anopheles gambiae sensu lato mosquitoes. The burning times were 9hr 20min for mosquito coils containing metofluthrin and 8 hr for those containing esbiothrin and the results were significantly different (p = <0.001). The mean knock down rate for mosquito coils containing metofluthrin was 90% and that for esbiothrin was 73.3% and the results were significantly different (p = 0.00). Mosquito coils containing metofluthrin had a mean repellence of 92.7% as compared to 85.4% for esbiothrin and the results were not significantly different (p=0.27). The protection time as required by EPA (1999) was 6 hr for mosquito coils containing metofluthrin and 5 hr for those containing esbiothrin. The mean insecticidal effect of mosquito coils containing metofluthrin was 84% as compared to 83% for those containing esbiothrin and the results were not significantly different (p = 0.56). Both mosquito formulations could not be classified as having insecticidal effect since none of them met the 95% mortality rate criteria.
Although evidence of mosquito coils' impact on disease epidemiology is limited, they are popularized as mosquito-borne disease prevention devices. Their usage affects the environment, human and mosquito health. This study investigated the perception, usage pattern and efficacy of coils in a predominantly poor malaria-endemic Ghanaian peri-urban area. Information on protection methods, perception and usage pattern was garnered using questionnaires. The efficacy of commonly used coils in the area was then assessed on the malaria vector, Anopheles gambiae, in a glass chamber. Sole or co-application of mosquito control methods and risky usage practices were reported. Coils were deemed harmful to humans and mosquitoes, and their perceived effectiveness varied, with several factors influencing their purchase. High d-allethrin concentration coils induced quicker mosquito knockdown; however, mortality was less than 85%. The coil usage pattern compromises users' health and can enhance mosquito tolerance to d-allethrin. The coils were ineffective against the vector, outlining a dichotomy between the users' perception of efficacy and the observed efficacy. Hence, the usage of other safer and more effective vector control methods should be encouraged to protect households.
Mosquito coils are insecticides commonly used for protection against mosquitoes due to their toxic effects on mosquito populations. These effects on mosquitoes could induce the expression of metabolic enzymes in exposed populations as a counteractive measure. Cytochrome P450 family 4 (CYP4) are metabolic enzymes associated with a wide range of biological activities including insecticide resistance. In this study, the efficacies of three commercial mosquito coils with different pyrethroid active ingredients were assessed and their potential to induce the expression of CYP4 genes in Aedes albopictus analyzed by real-time quantitative PCR. Coils containing 0.3 % D-allethrin and 0.005 % metofluthrin exacted profound toxic effects on Ae. albopictus, inducing high mortalities (≥90 %) compared to the 0.2 % D-allethrin reference coil. CYP4H42 and CYP4H43 expressions were significantly higher in 0.3 % D-allethrin treated mosquitoes compared to the other treated populations. Short-term (KT50) exposure to mosquito coils induced significantly higher expression of both genes in 0.005 % metofluthrin exposed mosquitoes. These results suggest the evaluated products provided better protection than the reference coil; however, they also induced the expression of metabolic genes which could impact negatively on personal protection against mosquito.
Bed bugs [both Cimex hemipterus (F.) and Cimex lectularius L.] are highly resistant to pyrethroids worldwide. An important resistance mechanism known as 'knockdown resistance' (kdr) is caused by genetic point mutations on the voltage-gated sodium channel (VGSC) gene. Previous studies have identified two point mutations (V419L and L925I) on the VGSC gene in C. lectularius that are responsible for kdr-type resistance. However, the kdr mutations in C. hemipterus have not been investigated.
Residents in irrigated urban agricultural sites face numerous mosquito problems such as increased mosquito populations and reduced insecticides susceptibility due to the creation of mosquito breeding sites and agricultural use of insecticides and hence require effective protective products against them. In this study, the protection effectiveness of three pyrethroid formulated mosquito coils of Malaysian origin against Anopheles gambiae sensu lato from an irrigated urban agricultural site in Ghana were evaluated for their potential use. Sucrose fed An. gambiae s.l. were exposed to insecticide-containing coils in a 70 cm x 70 cm x 70 cm glass chamber to assess the insecticidal effect of the coils. The 0.005% metofluthrin coil caused the most rapid knockdown of 50% of the test mosquitoes. The mean lethal effect of the coils on An. gambiae s.l. were as follows; 0.005% metofluthrin (86%), 0.3% d-allethrin (74.33%), 0.15% d-trans allethrin (72%) and the 0.25% d-allethrin reference coil (69%). The 0.005% metofluthrin coil achieved the highest insecticidal effect on An. gambiae s.l. compared to the other coils and hence performed better than the others as an anti-mosquito product. All the three test coils were effective against An. gambaie s.l. from the irrigated agricultural site compared to the reference coil.
Deltacide (S-bioallethrin 0.71% w/v, deltamethrin 0.5% w/v, piperonyl butoxide 8.9% w/v excipients to 100% w/v) and Solfac UL 015 (cyfluthrin 1.5% w/v) were evaluated against the sentinel sugar-fed adults and 4th-instar larvae of Aedes aegypti at 17 storey high-rise apartments in Malaysia using ULV applications. The impact of both insecticides on field populations of Ae. aegypti and Ae. albopictus larvae was monitored weekly using bottle containers. Both Deltacide and Solfac UL 015 showed adulticidal and larvicidal effects. This was the first field trial using Deltacide against dengue vectors in Malaysia and showed its potential for use in dengue vector control programs.
The bioefficacy of commercial mosquito coils containing four different active ingredients, namely metofluthrin, d-allethrin, d-trans allethrin, and prallethrin against Aedes albopictus (Skuse) (Diptera: Culicidae) from 10 states in Malaysia, was evaluated using the glass chamber method. In this study, Ae. albopictus exhibited various knockdown rates (50% knockdown time, KT50), ranging from 2.50 to 5.00 min, 2.50 to 7.00 min, 3.00 to 8.00 min, and 5.00 to 17.00 min for metofluthrin, d-trans allethrin, d-allethrin, and prallethrin, respectively. Overall, all strains of Ae. albopictus were most susceptible to metofluthrin, with mortality rates >80%. On the other hand, mortality rates ranging from 5.0 to 100% were observed from all populations exposed to d-trans allethrin, d-allethrin, and prallethrin. In addition, significant correlations between KT50 of metofluthrin and d-allethrin (r = 0.758, P = 0.011), metofluthrin and prallethrin (r = 0.676, P = 0.032), d-allethrin and d-trans allethrin (r = 0.832, P = 0.003), d-allethrin and prallethrin (r = 0.921, P = 0.000), and d-trans allethrin with prallethrin (r = 0.941, P = 0.000) were detected, suggesting some levels of cross-resistance within the pyrethroid insecticides. This study demonstrated that metofluthrin can induce high insecticidal activity in Ae. albopictus in Malaysia, followed by d-trans allethrin, d-allethrin, and prallethrin.