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PubMed2002

[Standardization of the method proposed by the World Health Organization for determining the susceptibility levels of leishmaniasis vectors to insecticides].

The WHO method for determining insecticide resistance was standardized for several species of Lutzomyia sand flies under laboratory and field conditions. The biological assays were applied solely to optimize the conditions for the control, i.e., without insecticide, and to estimate mortality due to handling or other unfavorable conditions. Adult female flies from 3 laboratory colonies and one field strain were tested: two laboratory strains of Lutzomyia longipalpis, one laboratory strain of Lutzomyia serrana and one field-collected strain of Lutzomyia quasitownsendi. The WHO method was compared with one modified in which, during the post-exposure period, the recommended plain tube apparatus was replaced with a plastic container layered with damp plaster of Paris. Three paper substrate types were compared under each condition: olive oil additive, silicon oil additive and plain paper. The measured variable was percent mortality in 24 h. For the WHO protocol, the L. longipalpis strains indicated a 0-10% mortality, L. serrana 20-80% and L. quasitownsendi 10-50%. With the modified WHO apparatus, the average mortality was < 4% for all species. No significant differences were observed among the paper treatments. These results indicate a strong species-specific effect of post-exposure conditions on sand flies. To establish baseline levels of insecticide resistance in Lutzomyia sand flies, the WHO method is recommended only for L. longipalpis, and the modified method for L. serrana, L. quasitownsendi and closely related species.

Animals↗
PubMed2002

Low insecticide deposit rates detected during routine indoor residual spraying for malaria vector control in two districts of Gokwe, Zimbabwe.

Questions have been raised about the quality of indoor residual spraying for malaria vector control after the decentralization of the national malaria control program in Zimbabwe. Given the critical role this control method plays, we conducted an exercise to determine the amount of insecticide (mg active ingredient/m2 of lambda-cyhalothrin) applied during routine house spraying. Severe insecticide underdosing was detected. Spraying efficiency ranged between 63.4 and 76.1% on walls, and 52.7 and 63.2% on roofs. Differences between 2 districts suggested the problem originates from deficient training and lack of pump calibration. Underdosing can undermine effective residual insecticide activity and the expected reduction in disease transmission.

Aerosols↗
PubMed2002

[Efficacy, toxicity and mechanism of insecticide KR-100: a preliminary study].

KR-100 is a newly developed long-lasting insecticide that incorporates cinerins substance, drug-release control substance and synergistic agent following certain procedures under carefully regulated conditions. Tests of the efficacy, toxicity, stability and long-term effect of KR-100 were conducted, and it was show that the insecticide possessed strong and long-lasting effect against mosquitoes, flies and cockroaches but was by no means toxic to human. Morphological study of KR-100 under scanning electron microscope revealed porous membrane form. This insecticide, therefore, can be safely applied with good pesticidal effect.

Animals↗
PubMed2001

Teratogenicity test of dimethoate containing insecticide formulation and heavy elements (Cu, Cd) in chicken embryos after administration as single compounds or in combination.

The teratogenic effects of heavy elements (Cu-sulphate, Cd-sulphate) and a 38% dimethoate containing insecticide formulation (Bi 58 EC) were studied on chicken after administration as a single compounds or in combination. The test materials were injected directly into the airchamber with an injector on day 12 of incubation. Applied concentrations of heavy elements (Cu-sulphate, Cd-sulphate) were: 0.01-0.001% and the concentration of pesticide was 0.1%. Final volume was 0.1 ml/egg. Evaluation was done on day 19 of incubation. After the administration of heavy elements (Cu-sulphate, Cd-sulphate) on day 12 of incubation, the average body mass of embryos significantly decreased at all the treated dose groups as compared to the control. Embryonic mortality did not increase at all the two dose levels of Cu-sulphate and at 0.001% conc. of Cd-sulphate, while the highest concentration of Cd-sulphate killed 20% of embryos treated. The number of embryos with developmental anomalies did not differ markedly from the control. The simultaneous administration of heavy elements (Cu-sulphate, Cd-sulphate) and dimethoate containing insecticide a statistically significant reduction in embryonic body mass occurred at all the treated dose groups. The incidence of developmental anomalies was markedly higher after the simultaneous use of heavy elements (Cu-sulphate, Cd-sulphate) and dimethoate containing formulation than in tests based on the separate use of heavy elements. Embryonic mortality increased at all the treated dose groups and reached almost 20% rate. In summary, it can be established that the simultaneous administration of heavy elements (Cu-sulphate, Cd-sulphate) and the dimethoate containing insecticide caused higher toxicity with respect to test of individual toxicity of heavy elements.

Abnormalities, Drug-Induced↗
PubMed2002

How will the reduction of tariffs and taxes on insecticide- treated bednets affect household purchases?

One of the steps called for in the fight against malaria is the removal of tariffs and taxes on insecticide-treated bednets (ITNs), netting materials, and insecticides, with a view to reducing the retail prices of ITNs and thus increasing utilization. In this paper we develop an approach for analysing the extent to which reform of tariff and tax policy can be expected to increase ITN purchases. We consider the following questions: (1). How much does the retail price of ITNs change if tariffs and taxes are reduced or eliminated? (2). How responsive is consumer demand to changes in the retail price of ITNs? Data on the price elasticity of demand for ITNs are very limited. Nevertheless, they suggest that ITN demand is not highly responsive to lower prices if household preferences are held constant. The reduction in retail prices associated with the removal of tariffs and taxes depends on the structure of the market in individual countries. In Nigeria, reducing the tariff on insecticides from 42% to zero and the tariff on netting materials from 40% to 5% is expected to increase ITN purchases by 9-27%, depending on the elasticity used. Country-specific information about market structure and cost conditions is needed if predictions are to be made as to how a specific policy change will affect ITN purchases.

Africa↗
PubMed2002

[Levels of organochlorine insecticides in Polish women's breast adipose tissue, in years 1997-2001].

Although manufacture and use of chlorinated insecticides was banned or severely restricted in most of countries in the 1970s, the residues of these compounds are still detected in various environmental matrices all over the world. Their highest levels are found in adipose tissue of beings at the top of food chain, including humans. Levels of persistent organochlorine compounds in human specimens are monitored by numerous scientific organizations in various countries, including Poland. The purpose of the study was to survey the current levels of selected organochlorine insecticides (isomers alpha-, beta-, gamma-, delta-HCH, o,p'- and p,p'-DDT, DDE i DDE, oxy-chlordane and heptachlor) in women's breast adipose tissue which can be an indicator of body burden. A total of 67 samples of adipose breast tissue collected between 1997 and 2001 from non-cancer patients, aged from 15 to 74 years have been analyzed. The analytical procedure included extraction, clean-up and analysis by means of GC-ECD with GC-MS confirmation. In all the samples analyzed p,p'-DDE, p,p'-DDT and beta-HCH were present (mean values, expressed as mg/kg of fat: 0.7700, 0.0720, and 0.0635 respectively) with p,p'-DDE, found to be dominant analyte. The levels of the remaining compounds, were usually about or below the method quantification limits (from 0.0025 to 0.0060 mg/kg of fat). The results for DDTs and beta-HCH for the oldest group (above 50 years) were 2.1 to 3.6 times higher than the youngest group (below 39 years). The results obtained in this study are similar to those reported in analogous samples collected from women living in other European countries with similar climate and history or organochlorines usage as well as in the USA. The presence of some organo-chlorine insecticide residues in women's adipose tissue, even those, who were born even 10-15 years after most countries introduced severe restrictions or banned the use of these compounds may be cause for anxiety. That is due to the potential of these compounds to promote toxic effects, including disrupting the human endocrine system.

Adipose Tissue↗
PubMed2002

Influence of selected insecticides on phosphatase activity in groundnut (Arachis hypogeae L.) soils.

Selected insecticides, Chloropyrifos, Dichlorovos, Methyl parathion, Phorate and Methomyl, at concentrations ranging from 0 to 10 kg ha(-1) were tested for their non-target effects towards activity of phosphatases in two soils. In soil samples receiving 2.5 kg ha(-1) of the insecticides Dichlorovos, Phorate and Methomyl and also in soil samples receiving 5.0 kg ha(-1) of the insecticides, Chloropyrifos and Methyl parathion, the activity of phosphatase was significantly more at 20 days period of incubation and decreased progressively with increasing period of incubation.

Arachis↗
PubMed2003

[Approximation to the CDC method to determine insecticide susceptibility in leishmaniasis vectors].

The Centers for Disease Control (CDC, USA) has proposed a simplified method for the determinations of insecticide resistance in adult mosquitoes, using 250 ml Wheaton bottles containing measured dosages. Insects are transferred into the bottle for 1 hour and monitored for mortality at regular intervals. In standardizing the CDC method for use with phlebotomine sand flies, effects of the solvent without insecticide were evaluated. Two colonized sand fly vector species were used: Lutzomyia longipalpis (F50 and F54) and Lutzomyia serrana (F17). Groups of 10 to 24 unfed females 1-3 days old were transferred for 1 h to Wheaton bottles with the following pretreatment: (1) without additive, (2) 0.5 ml of acetone, or (3) 1.0 ml of acetone. Three to 5 replicates were undertaken for each condition and each species. In the control bottles, the insects rested quietly and after 1 h appeared normal. In bottles with 0.5 and 1.0 ml acetone, a repellent effect was observed in L. longipalpis and L. serrana within the first 10 min. A small proportion of the L. serrana became prostrate, but recovered quickly after removal from the bottle. Field test performed with Lutzomyia quasitownsendi produced results simialar to those of the L. serrana colony flies. The insecticide bioassays were performed with L. longipalpis (F60) flies. Females were exposed to three graded doses of lambdacyhalothrin (10, 50 and 100 micrograms/bottle), and mortality was recorded at five-minute intervals. Regression lines for the 3 concentrations were compared within the context of the CDC method. The advantages of the CDC method over the WHO protocols were four: lower cost, fewer insects required, an entire group of insects exposed to the same surface, and ease of field use.

Acetone↗
PubMed2002

Testing insecticide susceptibility of Phlebotomus perniciosus and P. papatasi (Diptera: Psychodidae) in Italy.

A study was undertaken to establish the susceptibility of two recently colonized sand fly species, Phlebotomus perniciosus and P. papatasi to some insecticides. A laboratory colony of P. papatasi, unexposed to insecticides for a period of ten years, was used as reference strain. Bioassay tests were carried out according to the WHO standard protocols based on the mortality rates recorded at different exposure times. Serial (from 1 to 60 min) exposures to DDT 2%, lambda-cyhalothrin 0.06% and permethrin 0.2% were tested on groups of 30 adult sugar-fed female sand flies, for a total of 7,470 specimens. Data were subjected to probit analysis and the susceptibility was calculated at LT50 and LT95 by comparison with the laboratory reference strain. The LT50 values for P. perniciosus were 19.9, 3.2 and 6.9 min, and for P. papatasi 18.0, 7.4 and 11.0 min, using DDT, lambda-cyhalothrin and permethrin, respectively. The results showed that two Italian populations of P. perniciosus and P. papatasi from Campania region and from Rome, respectively, are susceptible to the insecticides tested as compared with the reference strain used.

Animals↗
PubMed2003

Cost-effectiveness of social marketing of insecticide-treated nets for malaria control in the United Republic of Tanzania.

OBJECTIVE: To assess the costs and consequences of a social marketing approach to malaria control in children by means of insecticide-treated nets in two rural districts of the United Republic of Tanzania, compared with no net use. METHODS: Project cost data were collected prospectively from accounting records. Community effectiveness was estimated on the basis of a nested case-control study and a cross-sectional cluster sample survey. FINDINGS: The social marketing approach to the distribution of insecticide-treated nets was estimated to cost 1560 US dollars per death averted and 57 US dollars per disability-adjusted life year averted. These figures fell to 1018 US dollars and 37 US dollars, respectively, when the costs and consequences of untreated nets were taken into account. CONCLUSION: The social marketing of insecticide-treated nets is an attractive intervention for preventing childhood deaths from malaria.

Bedding and Linens↗
PubMed2003

[Seminal profile in workers exposed to cholinesterase inhibitor insecticides].

The objective of this study was to determine the physical, chemical and cytomorphologic characteristics of semen obtained from workers exposed to cholinesterase inhibitor insecticides and compare them with samples of the same nature obtained from unexposed subjects, and in addition, to correlate those findings with blood levels of cholinesterase. The study group consisted of 29 adult males, age range 20-54, that were exposed to cholinesterase inhibitor insecticides during 4 hours per day for a variable lapse (one year minimum), whereas the control group consisted of 30 unexposed individuals of the same gender, and similar age range. A thorough medical examination was performed in every individual. It consisted of an occupational medical history and complete physical exam. A blood sample was obtained in all the subjects in order to determine total cholinesterase levels by the modified S. Hestrin Hydroxamate method. Semen analysis was done in specimens collected after recent masturbation following a 3-day abstinence period. The data was processed and analyzed by the SAS computerized statistics program. The results revealed significant differences between both groups (p < 0.05) for the following variables: sperm count per mL., percentage of fast, mobile and immobile, live and dead spermatozoids. Spermatozoa morphology was found to be within normal limits as established by the WHO. Nevertheless, the differences related to the percentage of big head and amorphous spermatozoids was significant (p < 0.05). The results indicate that cholinesterase inhibitor insecticides affect certain variables of the semen analysis and hence the quality of the semen.

Adult↗
PubMed2003

Susceptibility of black fly larvae (Diptera: Simuliidae) to lawn-care insecticides individually and as mixtures.

Urban and suburban watersheds have the potential to be highly impacted by chemicals, especially insecticides to control insect pests on lawns, ornamental plants, and home gardens. Three of the most common lawn-care insecticides detected in urban watersheds, carbaryl, chlorpyrifos, and malathion, have been evaluated using an acute orbital shaker toxicity test to determine their respective concentrations that produce 50% mortality (LC50) in Simulium vittatum Zetterstedt cytospecies IS-7 larvae. Results of the 48-h LC50 tests show chlorpyrifos to be the most toxic to black fly larvae (LC50 = 0.28 microg/L) followed by carbaryl (LC50 = 23.72 microg/L) and malathion (LC50 = 54.20 microg/L). These insecticides were also tested as binary and ternary mixtures using the toxic unit (TU) approach. Toxicity was shown to be greater than additive for the ternary mixture of chlorpyrifos-carbaryl-malathion (LC50 = 0.56 TU) and the binary mixtures of chlorpyrifos-malathion (LC50 = 0.72 TU) and carbaryl-malathion (LC50 = 0.78 TU). The binary combination of chlorpyrifos and carbaryl was shown to be additive (LC50 = 0.98 TU). These results indicate that aquatic invertebrate populations in urban and suburban streams may experience a higher-than-expected increase in toxicity-related effects when all three chemicals are present in the waterway.

Animals↗
PubMed2003

Insecticide susceptibility status of Aedes aegypti to DDT and dieldrin in desert and non-desert parts of Rajasthan.

Seasonal prevalence and insecticide susceptibility tests were carried out on the adults of Aedes aegypti, the vector of dengue and dengue hemorrhagic fever(DF/DHF), in three desert (Bikaner, Jaisalmer and Jodhpur) and three non-desert (Alwar, Ajmer and Jaipur) districts of Rajasthan. Among the three species viz. Ae. aegypti, Ae. vittatus and Ae. w-albus encountered during the survey the former was the most prevalent species. Studies were carried out both in rural and urban areas against different concentrations of two organochlorines (DDT and Dieldrin). In rural areas resistance has been observed with DDT and dieldrin both in desert and non-desert parts while an intermediate resistance has been observed in the urban areas with both the insecticides which required further verification. Resistance was more pronounced in rural areas as compared to urban areas. LC50 along with regression equation and Chi-square values have been determined for both the insecticides.

Adaptation, Physiological↗
PubMed1957

Control of health hazards likely to arise from the use of organo-phosphorus insecticides in vector control.

The widespread use of DDT and the chlorinated hydrocarbon group of insecticides for the control of mosquitos and flies has led to the emergence of resistant strains of flies. Where the DDT group of insecticides is ineffective for the control of resistant insects, it appears that the use of the organo-phosphorus group of insecticides may be an alternative. However, it seems probable that their introduction and application under the same conditions in which DDT has been safely used might carry serious risks to the health of the men who apply them. In this paper, the authors indicate what these dangers are, how they manifest themselves, and how they might be controlled. Four methods of blood-cholinesterase determinations, carried out in the laboratory and in the field, are described in an annex.

Cholinesterases↗
PubMed1961

Resistance of Aedes aegypti to certain chlorinated hydrocarbon and organophosphorus insecticides in Puerto Rico.

Failure to control Aëdes aegypti in Puerto Rico has suggested resistance to the insecticides, particularly DDT. A laboratory colony (named Isla Verde strain) was established from material obtained near the International Airport. This strain proved highly resistant to DDT and dieldrin as well as various other insecticides. The scientific and practical significance of this is far-reaching. Heretofore, it was thought that populations of Aëdes aegypti could be resistant to the DDT group of insecticides or to the dieldrin group but not to both, and that one type of resistance involved biochemical, toxicological and genetic characteristics different from the other. This theory must now be modified or even abandoned. From the practical point of view, it is clear that the continued use of DDT or dieldrin for Aëdes aegypti control in Puerto Rico is questionable, for it is not wise to attempt to overcome high resistance by increasing the concentration or rate of application. Further, the situation demonstrated for Puerto Rico may also obtain in other islands of the Caribbean where Aëdes aegypti is known to be DDT-resistant.

Aedes↗
PubMed1959

Residual insecticides and the problem of sorption.

Whereas laboratory investigations have elucidated the mechanism of sorption of residual insecticides and demonstrated that their persistency is determined by a number of physico-chemical factors and is therefore theoretically calculable, the variables encountered in the field may produce results in apparent conflict with those theoretically expected. Attempts to enhance persistency through the prevention of sorption, although promising, have so far not been fully successful. It is consequently also necessary to assess the residual effectiveness of insecticides, "effectiveness" here being viewed as a biological effect expressed in terms of the mosquito mortality produced. For this purpose bio-assay tests have been used, but with very variable results, and it is suggested that a study of the bio-assay technique itself is needed. This should be conducted in parallel with chemical determinations of the total amount of insecticide present both on and below the sprayed surface.

Animals↗
PubMed1964

THE ASSESSMENT OF INSECTICIDAL IMPACT ON THE MALARIA MOSQUITO'S VECTORIAL CAPACITY, FROM DATA ON THE PROPORTION OF PAROUS FEMALES.

In malaria eradication the residual insecticide exerts upon the mosquito's vectorial capacity a direct insecticidal impact, the order of which may be measured by observing the decrease in the proportion of parous females. The impact is expressed as the product of the degree of reduction of the expectation of infective life (termed the longevity factor of impact) and that of the expectation of life (the density factor). To compute the factors from the proportion parous it is necessary to know also the mean difference in age between the nulliparous and the youngest parous females in the sample, and the sporogonic period of the parasite.Graphs are presented to enable the field worker, who has observed these parameters, to read off from his data the proportion surviving one day, the expectation of infective life and the expectation of life. Examples from the field are used to illustrate the manner of computing the direct insecticidal impact with the aid of the graphs. It is emphasized that this method can only measure the relative impact on vectorial capacity, and will not show whether the actual level of vectorial capacity is such that a malaria reproduction rate of <1 is indicated.

Animals↗
PubMed2003

Topical toxicity of two acetonic fractions of Trichilia havanensis Jacq. and four insecticides to larvae and adults of Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae).

The toxicity of botanical origin compounds such as two acetonic fractions of the seed kernels of the Meliacea Trichilia havanensis Jacq with insecticide properties (azadirone (F12) and the mixture F18 [1,7+3,7-di-O-acethylhavanensin (4:1)], three insecticides commercially available (imidacloprid, natural pyrethrins+PBO, triflumuron) and phloxine B, were tested in the laboratory. Topical bioassays using third instar and newly emerged adults of the lacewing Chrysoperla carnea (Stephens) at the maximum field recommended rate in Spain for commercials and at 1,000 ppm of active ingredient for T. havanensis acetone fractions and phloxine-B, were carried out. Imidacloprid and triflumuron were very toxic to third instar larvae inhibiting adult emergence, being the rest of insecticides harmless. Fecundity and fertility were not affected by the non-toxic compounds. Concerning adults, only imidacloprid and natural pyrethrins killed them significantly 24 hours after treatment. Phloxine B, triflumuron and T. havanensis fractions were harmless and did not cause any effect on fecundity and fertility with the exception of triflumuron, which reduced considerably the egg hatch. It can be concluded that T. havanensis acetonic fractions and phloxine B were non-toxic to larvae and adults of C. carnea when treated topically, whereas triflumuron, natural pyrethrins and imidacloprid affected one or more of the evaluated parameters under our conditions.

Acetone↗