Do traditional mosquito repellent plants work as mosquito larvicides?

A CAJM study on the effectiveness of African traditional plants as mosquito repellents.Malaria is a serious health problem in many African countries, including Zimbabwe1 and the concept that malaria transmission can be interrupted by the use of residual insecticides has long been the basis for malaria control programmes. In Zimbabwe, mosquitoes are widely controlled by the use of residual spraying in rural areas and this is paid for the government.2 This puts pressure on scarce resources to sustain the mosquito control programme, hence there is need to evaluate indigenous plants as mosquito larvicides. Of all the plants mentioned as mosquito repellents, Lippia javanica and Ocimum canum were very common and therefore were evaluated as larvicides. The Bulawayo City council used Termephos “Abate®” to control nuisance mosquitoes10 and 300 litres of used oil to treat defective septic tanks. Coopex Larvicide® containing 2 pc permethrin was evaluated in Gokwe11 and results suggest that the larvicide has no effect on the pupa but the emerging adults die later on

Knock down and insecticidal activity of the plants Tagetes minuta, Lippia javanica, Lantana camara, Tagetes erecta and Eucalyptus grandis on Anopheles arabiensis mosquitoes

The knock down and insecticidal effects of the plants Tagetes minuta, Lippia javanica, Lantana camara, Tagetes erecta and Eucalyptus grandis were evaluated against Anopheles arabiensis mosquitoes in thatched round huts in Mumurwi village. Leaves from these plants were smouldered in order to provide mosquito repellent smoke. Complete knock down was provided 40 minutes after mosquitoes were exposed to smoke of T. erecta, 60 minutes to smoke of T. minuta and E. grandis and 120 minutes to smoke of L. javanica. Complete knock down of mosquitoes could not be provided by L. camara within the 140-minute exposure period. The KT50 (time required to knock down 50% of the mosquitoes) values were 24.985 minutes (T. minuta), 34.473 minutes (T. erecta), 59.119 minutes (L. javanica), 59.828 minutes (L. camara) and 25.245 minutes (E. grandis). The KT90 (time required to knock down 90% of the mosquitoes) values were 48.060 minutes (T. minuta), 50.169 minutes (T. erecta), 178.341 minutes (L. javanica), 140.220 minutes (L. camara) and 47.998 minutes (E. grandis). Mortality rates 24h after exposure were 40% (T. minuta), 100% (T. erecta), 75% (L. javanica), 90% (L. camara) and 100% (E. grandis). In conclusion, smoke from the plants T. erecta, T. minuta and E. grandis had very fast knock down rates with T. erecta, L. camara and E. grandis killing over 90% of the An. arabiensis mosquitoes. Plant smoke is important in mosquito control

Drastic reduction in density of Blattella germanica and Periplaneta americana cockroaches after the application of fenitrothion and lindane in Dema, Zimbabwe

Field studies were conducted in villages near the peri urban Dema area, Seke district, Zimbabwe, in order to understand the effect of the insecticides fenitrothion and lindane on Periplaneta americana and Blattella germanica cockroaches. A total of 63, 72 and 71 rooms were used for control, fenitrothion and lindane respectively. The mean density per room for P. americana before spraying was 43.5, 42.7 and 44.1 for the control, fenitrothion and lindane respectively. The mean density per room for B. germanica before spraying was 51.4, 50.2 and 47.1 for the control, fenitrothion and lindane respectively. A reduction in population density of P. americana was 3.2%, 83.8% and 99.3% in the control, fenitrothion and lindane rooms respectively. A reduction in population density of B. germanica was 87.8% and 82.8% in fenitrothion and lindane rooms respectively. An increase of 9.9% in the control rooms was observed. The majority of P. americana cockroaches died one month post spray with fenitrothion killing 78.2% and lindane 37.4% of all cockroach collections. However, the number of dead B. germanica cockroaches was almost of the same order for fenitrothion (71.9%) and lindane (74.5%). The residual effect of fenitrothion was 3 months on both cockroach nymph species and that of lindane was 1 month. In conclusion, both fenitrothion and lindane had impact on cockroach density, and fenitrothion showed a residual effect of 3 months

Mosquito coil emissions and health implications.

Burning mosquito coils indoors generates smoke that can control mosquitoes effectively. This practice is currently used in numerous households in Asia, Africa, and South America. However, the smoke may contain pollutants of health concern. We conducted the present study to characterize the emissions from four common brands of mosquito coils from China and two common brands from Malaysia. We used mass balance equations to determine emission rates of fine particles (particulate matter < 2.5 microm in diameter; PM(2.5)), polycyclic aromatic hydrocarbons (PAHs), aldehydes, and ketones. Having applied these measured emission rates to predict indoor concentrations under realistic room conditions, we found that pollutant concentrations resulting from burning mosquito coils could substantially exceed health-based air quality standards or guidelines. Under the same combustion conditions, the tested Malaysian mosquito coils generated more measured pollutants than did the tested Chinese mosquito coils. We also identified a large suite of volatile organic compounds, including carcinogens and suspected carcinogens, in the coil smoke. In a set of experiments conducted in a room, we examined the size distribution of particulate matter contained in the coil smoke and found that the particles were ultrafine and fine. The findings from the present study suggest that exposure to the smoke of mosquito coils similar to the tested ones can pose significant acute and chronic health risks. For example, burning one mosquito coil would release the same amount of PM(2.5) mass as burning 75-137 cigarettes. The emission of formaldehyde from burning one coil can be as high as that released from burning 51 cigarettes

To what extent does salt (NaCl) affect Anopheles gambiae sensu lato mosquito larvae survival?

The effect of salt (NaCl) on Anopheles gambiae sensu lato (s.l.) mosquito larval breeding was ascertained under laboratory conditions. No larval mortality occurred when the Cl– concentrations were between 0.017 ppt (0.03 ppt salinity) and 7.371 ppt (13.25 ppt salinity). However, 9%, 24%, 73.5%, 91.5% and 99.5% larval mortality occurred at 10.828 ppt (19.49 ppt salinity), 16.069 ppt (28.95 ppt salinity), 18.739 ppt (33.77 ppt salinity), 32.587 ppt (58.82 ppt salinity) and 47.326 ppt (85.37 ppt salinity) NaCl concentrations respectively. The lower NaCl concentrations resulting in LC50, (lethal concentration for 50% larval mortality), LC90 (lethal concentration for 90% larval mortality), LC95 (lethal concentration for 95% larval mortality), and LC99 (lethal concentration for 99% larval mortality) were 23.12 ppt (41.19 ppt salinity), 24.91 ppt (44.42 ppt salinity), 27.76 ppt (49.56 ppt salinity) and 33.87 ppt (60.568 ppt salinity) respectively. The upper NaCl concentration resulting in LC50, LC90, LC95 and LC99 were 32.89 ppt (58.83 ppt salinity), 37.21 ppt (66.63 ppt salinity), 44.79 ppt (80.32 ppt salinity) and 63.76 ppt (114.55 ppt salinity) respectively. In conclusion, the level of water salinity may indicate the presence or absence of An. gambiae s.l. mosquito larvae and this information can be used for disease control purposes

Insecticide susceptibility tests conducted in Kamhororo, Masakadza and Chilonga villages in Zimbabwe during the 2011 malaria period

Insecticide susceptibility tests using World Health Organization papers treated with 4% dichloro-diphenyl-trichloro-ethane (DDT), 0.05% deltamethrin, 0.05% lambda-cyhalothrin, 0.5% etofenprox, 0.15% cyfluthrin and 0.75% permethrin were conducted in Kamhororo, Masakadza and Chilonga villages, Zimbabwe. Three to 5-day old female <em>Anopheles gambiae sensu lato</em> adult mosquitoes were used. Deltamethrin knocked down 100% of the mosquitoes from Kamhororo, Masakadza and Chilonga at 35 min exposure. DDT did not knock down 100% of the mosquitoes from Kamhororo and Masakadza but did so in Chilonga. One hundred percent knockdown was achieved for cyfluthrin when exposed to mosquitoes from Kamhororo (60 min), Masakadza (25 min) and Chilonga (25 min). Etofenprox knocked down 100% of the mosquitoes collected from Kamhororo (30 min), Masakadza (30 min) and Chilonga (55 min). Knockdown of mosquitoes due to deltamethrin, DDT, cyfluthrin, permethrin; lambda-cyhalothrin and etofenprox were different at different observation times. One hundred percent mortality due to deltamethrin, DDT, etofenprox, lambdacyhalothrin and cyfluthrin was recorded for mosquitoes collected from all the 3 sites. One hundred percent mortality due to pemethrin was recorded for mosquitoes collected from Kamhororo and Chilonga but mortality was 98.5% for those collected from Masakadza. No knockdown or mortality occurred in the controls from each locality. The kd₅₀ (knockdown of 50% of the mosquitoes) values were 24.4-73.7 min (DDT), 8-13 min (pemethrin), 9.4-16.3 min (cyfluthrin), 9.4-14.4 min (etofenprox), 8.7-13 min (lambda-cyhalothrin) and 12.1-15.9 min (deltamethrin). The kd₉₀ (knockdown of 90% of the mosquitoes) values were 45.6-199.5 min (DDT), 14.7-26.5 min (pemethrin), 16.5-34.9 min (cyfluthrin), 21.8-24.4 min (etofenprox), 16.3-31.6 min (lambdacyhalothrin) and 21-25.3 min (deltamethrin). No insecticide resistance was recorded from the 3 sites

PERCEPTIONS ABOUT MALARIA TRANSMISSION AND CONTROL USING ANTI-MALARIA PLANTS IN MOLA, KARIBA, ZIMBABWE

An ethnobotanical survey was conducted in Mola, Kariba district, in order to collect information on some common herbal remedies used by traditional healers and rural folk in the treatment and prevention of malaria. Structured questionnaires were administered to 220 respondents in Mola, Kariba. Two hundred and twenty questionnaires were administered to respondents who were between the ages of 14 andd 80 years. There were 88 (40%) males and 132 (60%) females with mean ages of 41.0682+17.4572 and 41.5000 + 18.7028 for males and females respectively. A total of 192 (87.3%) of the respondents mentioned mosquitoes as transmitting malaria, one (0.3%) mentioned dirty water and 27 (12.4%) did not know. Fifty-four (24.5%) respondents did not know signs and symptoms of malaria. High body temperature, headache and shivering (23.2%) were major signs used in diagnosing malaria. A total of 155 (70.5%) respondents would go to the clinic if they suspect that they have malaria and 36 (16.4%) will visit a Traditional Healer. The following plants were mentioned as being used as anti—malarials: Carica papaya L. (Caricaceae), Zea mays L. (Sapindaceae), Amblygonocarpus andongenis (Olvi.) Exell and Torre (Leguminosae), Zanha africana (Radlk.) Exell (Sapindaceae), Solanum incanum L. (Solananceae), Solanum indicum L. (Solanaceae), Solanum panduriforme E. May (Solanaceae), Diplorhynchus condylocarpon (Muell. Arg.) Pick. (Apocynaceae), Harungana madagascariensis Poir (Guittiferae), Pterocarpus angolensis DC (Leguminosae), Euclea divinorum Hiern (Ebenaceae), Sclerocarya caffra Sond (Anacardiaceae), Terminalia sericea DC (Combretaceae), Aloe chabaudii Schonl. (Liliaceae), Aloe excelsa Berg. (Liliaceae), Aloe greatheardii Schoni (Liliaceae), Colophospermum mopane (Benth.) J. Leonard (Leguminosae) and Garcinia huillensis Oliv. (Guttiferae). In clonclusion, several plants used as anti-malarials were identified and their acivity will be determined. Key Words: Malaria, Zimbabwe, Antimalarial plants Nig. J. Nat Prod. And Med. Vol.5 2001: 4-