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PubMed1995

Characterization of resistance to organophosphate, carbamate, and pyrethroid insecticides in field populations of Aedes aegypti from Venezuela.

Resistance to the organophosphates (OP) temephos, malathion, and pirimiphos methyl, and the carbamate propoxur was found to be low (< 5-fold) in 3 Aedes aegypti populations collected from Falcon and Aragua states of Venezuela. Resistance to chlorpyrifos (OP), permethrin, and lambda-cyhalothrin (pyrethroids) was moderate (7-fold) in both populations. Mechanisms of resistance were investigated with the synergists piperonyl butoxide (mixed function oxidase inhibitor) and S, S, S-tributyl phosphorothioate (DEF, an esterase inhibitor). Nonspecific esterase and oxidase enzymes played a significant role in OP and carbamate resistance, respectively. Resistance to pyrethroid insecticides was not affected by DEF or piperonyl butoxide. This suggested the presence of another mechanism such as altered target site sensitivity (kdr). Biochemical tests showed significantly greater amounts of esterase activity in field strains, whereas insensitive acetylcholinesterase was not involved in either OP or carbamate resistance. These results must be considered in future control programs for Ae. aegypti, because OPs and pyrethroids are currently used in vector control in most countries of Central and South America.

Aedes↗
PubMed1996

Some emerging issues on the malaria problem in Kenya.

Malaria in Kenya has been characterised by marked variability in its epidemiology, partly reflecting the obstacles and progress made in the control strategies. The impact of anti-vector activities in the 1970s and before have been observed for variable lengths of time afterwards. Malaria has re-emerged in areas previously with little or no transmission. The recovery of infective Anopheles gambiae vector in higher altitudes affirms the potential for transmission in areas where epidemics have been known to occur. Morbidity and mortality patterns in the otherwise endemic lowlands have become increasingly severe, an observation which would be attributed to the increasing inefficacy of chloroquine. Efforts to promote personal protection suffer substantial setbacks in sustainability inspite of apparent acceptability. There are indications that the mosquito vector susceptibility to permethrin and other insecticides will now require continual monitoring in order to detect development of significant resistance. In this communication, we review some emergent issues in malaria transmission in Kenya and the potential for control as adduced from historical and contemporary perspectives.

Altitude↗
PubMedDate not supplied

Multiresidue liquid chromatographic method for simultaneous determination of pyrethroid insecticides in fruits and vegetables.

A simple and rapid liquid chromatographic (LC) method has been developed for simultaneous determination of 9 pyrethroid insecticides (biphenthrin, cypermethrin, fenpropathrin, fenvalerate, flucythrinate, methothrin, permethrin, py-115, and tetramethrin) in fruits and vegetables. Residues are extracted from crops with methanol and partitioned with toluene. Extracts are cleaned up by Florisil-charcoal column chromatography. LC separation is performed on a muBondapak C18 stainless steel column with acetonitrile-deionized water as mobile phase. The insecticides are detected at 206 nm with 0.03 absorbance unit full scale. Recoveries of 9 pyrethroid insecticides from 6 crops (cucumbers, tomatoes, cabbages, apples, pears, and peaches) fortified at 0.5-5.0 mg/kg were 62.7-129.2%. Detection limits were about 0.05 mg/kg, except for py-115, for which detection limit was 0.10 mg/kg.

Chromatography, Liquid↗
PubMedDate not supplied

Modification of AOAC multiresidue method for determination of synthetic pyrethroid residues in fruits, vegetables, and grains. Part I: Acetonitrile extraction system and optimization of florisil cleanup and gas chromatography.

We present a multiresidue method for determination of synthetic pyrethroids in fruits, vegetables, and grains. The method is a modification of AOAC Method 970.52. Residues are extracted with acetonitrile (for fruits and vegetables) or acetonitrile-water (2 + 1) (for grains) and then transferred to hexane. Coextractives are removed by acetonitrile partitioning and open-column chromatography with deactivated Florisil. The final extract is analyzed by gas chromatography with electron capture detection (GC-ECD). An HP-17 wide-bore column is used to determine the individual isomeric contents of each insecticide. The method was used to recover 8 pyrethroids (biphenthrin, fenpropathrin, cyhalothrin, permethrin, cypermethrin, fluvalinate, fenvalerate, and deltamethrin) spiked at 0.01-4.0 mg/kg in 20 crops (apple, pear, peach, banana, grape, strawberry, potato, tomato, cucumber, pepper, cabbage, carrot, celery, polished rice, wheat, green gram, buckwheat, sorghum, maize, and barley). Recoveries of the 8 pyrethroid insecticides in 6 crops ranged from 83.8 to 112.8%, with a coefficient of variation (CV) of 2.00 to 12.09% for the narrow-bore capillary GC (n = 6) and from 82.8 to 106.4%, CV = 2.93-12.19%, for the wide-bore capillary GC (n = 6). The minimum detectable levels of 0.004-0.028 mg/kg (for fruits and vegetables) or 0.01-0.08 mg/kg (for grains) for the 8 pyrethroids are easy to detect.

Acetonitriles↗
PubMedDate not supplied

[Evaluation of malaria vector control measures in central Vietnam (1976-1991)].

Activities used to control malaria transmission in the pilot station of Vanh Canh in the Binh Dinh Province of central Vietnam from 1976 to 1991 have been evaluated. These activities were: spraying DDT in and around the houses in the villages and the settlements in the fields; spraying lambdacyalothrin in the houses; and use of bed-nets impregnated with permethrin. Their efficacy was measured by the number of fever episodes due to malaria infections among the population. The spraying of DDT in the houses was followed by a reduction of malaria infection by more than 90%. However, spraying of the settlements was not advantageous. The termination of DDT spraying was not followed by an increase of malaria infections. Spraying with lambdacyalothrin was slightly more effective than with pyrimiphos and DDT. The use of pesticide-impregnated bed-nets was efficient, especially in the villages far away from the forest. Thus, these activities can contribute to the control of the malaria endemic in central Vietnam.

Adolescent↗
PubMed1996

The role of the family physician in the day care setting.

Injuries and infectious respiratory, gastrointestinal and dermatologic diseases are common in day care settings. Most day care injuries are contusions, abrasions and cuts involving the head and extremities. Impact-absorbing surfaces under playground equipment, safely-proofing of all play areas, increased staff supervision, and staff and parental education might reduce injuries by as much as 75 percent. Respiratory illnesses are the most common day care infections. Chemoprophylaxis with rifampin is required for all close contacts of children infected with Haemophilus influenzae type B and Neisseria meningitidis. Diarrheal illness may be caused by viral pathogens, bacterial agents such as Shigella, Campylobacter or Salmonella, or parasitic infections caused by Giardia lamblia and Cryptosporidium. Strict hand-washing procedures, especially before food preparation and after toileting, may reduce diarrheal illness by 50 percent. Head lice (Pediculosis capitis) and scabies are common dermatologic infections spread by direct contact and through clothing, bedding and hair brushes. Screening and treating affected children with permethrin preparations and thoroughly washing bedding and clothing are necessary to stop outbreaks. Use of universal precautions for the handling of stool is essential to prevent the spread of both ordinary diarrheal illnesses and serious infections such as hepatitis A and B, human immunodeficiency virus and cytomegalovirus.

Child↗
PubMed1996

Toxicity of insecticides to Toxorhynchites splendens and three vector mosquitos and their sublethal effect on biocontrol potential of the predator.

Toxicity of six larvicides ie fenthion, temephos, malathion, deltamethrin, alphamethrin (Fendona), OMS 3031 and five adulticides ie malathion, fenitrothion, propoxur, deltamethrin, permethrin to Aedes aegypti, Culex quiquefasciatus, Anopheles stephensi and the predator, Toxorhynchites splendens was studied for evaluating safety margin. Concentrations of alphamethrin that killed 50% larvae of T. splendens were 53 and 12 times more than that which killed Cx. quinquefasciatus and Ae. aegypti. In case of deltamethrin, concentrations required to kill 50% larvae of T. splendens were 14 and 5 times more than that required against other two species. Other larvicides tested were equally toxic to both T. splendens and vector mosquitos. There was no significant difference in the toxicity of larvicides to T. splendens and An. stephensi. Deltamethrin was 25-132 times less toxic to adults of T. splendens in comparison to vector mosquitos. For other adulticides the range was 1-10. Immature developmental time of T. splendens was not affected by any of the insecticides tested. However, predation rate was lowered when larvae of Ae. aegypti previously exposed to fenthion and temephos were offered. Whereas, alphamethrin and OMS 3031 did not affect the feeding rate of the predator. There was a significant reduction in the pupal weight and pupation as a result of the predator feeding on the insecticide treated prey. There was a significant negative relationship between rate of pupation and dosage. The present study indicates that synthetic pyrethroids owing to their higher safety margin can be used in an integrated vector management program.

Aedes↗
PubMed1997

Sustainability of pyrethroid-impregnated bednets for malaria control in Afghan communities.

Between 1992 and 1995 a series of studies was undertaken to assess the long-term suitability of pyrethroid-impregnated bednets (PIBs) for malaria control in Afghan refugee communities in two villages in North-West Frontier Province, Pakistan. During 1992, 86% of bednet owners volunteered to have their bednets re-impregnated, and a further 15% of families purchased nets at two-thirds of cost price. From 1992 onwards, 27% of the villagers returned to Afghanistan, and annual house spraying campaigns were introduced to protect those still resident but sleeping without bednets. Within 3 years, these campaigns, together with PIBs, reduced the annual incidence of malaria by 87%, from 597 to 78 cases per 1000 population. Nevertheless, 65% of resident families continued to re-impregnate their nets annually with permethrin. To assess whether PIBs were still being used and were still protective, in view of these reduced transmission rates, we carried out a case--control study in 1994 on febrile or otherwise symptomatic patients presenting at village health centres. Comparison of the slide-positivity rates of PIB users and those without bednets showed that regular usage reduced the odds of contracting falciparum and vivax malaria to 0.22 (95% confidence interval (CI): 0.09-0.55) and 0.31 (95% CI: 0.19-0.51), respectively. There was no evidence of a sex- or age-bias in bednet use or in protective effect. The results indicate that a community-based PIB programme is an appropriate malaria control measure in areas where management or security problems make traditional house-spraying campaigns impossible. A relevant finding for those involved in the monitoring of bednet distribution projects is that the local coverage of bednets and the local impact on malaria, even when introduced to remote areas, can be estimated very cheaply by health centre microscopists who simply catalogue blood film diagnoses according to patients' bednet use practices.

Afghanistan↗
PubMed1996

Insecticide impregnated cotton fabrics of different hydrophobicity against Aedes aegypti (Diptera:Culicidae).

Residual efficacy of synthetic pyrethroids, viz, permethrin, deltamethrin, lambdacyhalothrin and an insect repellent DEPA in cotton fabrics of different hydrophobicity was tested against Aedes aegypti. Amino silicone was used for enhancing the hydrophobicity of the fabrics. The results showed that there was an increasing trend in repellency/feeding deterrency with the increase in hydrophobicity up to 17.5 weeks at an optimum level of 30g/l. The adulticidal effect lasted for 1 to 4 weeks and this lower residual activity was attributed to the repellency of the treated fabrics. The results indicated that the residual efficacy of cotton fabrics could be enhanced by treating with an hydrophobic agent that increases the availability of the insecticide on the surface.

Aedes↗
PubMed1997

Efficacy of three synthetic pyrethroids against three mosquito species in Arkansas and Louisiana.

Adult mortality of Anopheles quadrimaculatus, Culex quinquefasciatus, and Aedes sollicitans was observed following ultra-low-volume (ULV) exposure to Responde, Permanone 31-66 RTU, and Scourge. Permanone 31-66 RTU (1:2.13, permethrin:PBO) and Scourge (1:3, resmethrin:PBO) were applied at 0.00175 lb AI/acre, while Responde (1:3, prallethrin:PBO) was applied at 0.001 lb AI/acre, and all were evaluated at 100, 200, and 300 ft. downwind of application. Significant mortality differences (P < or = 0.05) were observed among all compounds at 15 min and at 1, 12, and 24 h posttreatment against An. quadrimaculatus and Cx. quinquefasciatus. Responde exhibited significantly greater (P < or = 0.05) control (knockdown) against An. quadrimaculatus at both 15 min and 1 h posttreatment than did Permanone 31-66 RTU or Scourge; however, some recovery occurred by 12 h posttreatment. At 15 min posttreatment, Responde and Scourge were significantly (P < or = 0.05) more effective against Cx. quinquefasciatus than Permanone 31-66 RTU except at 300 ft. downwind, where Scourge was significantly (P < or = 0.05) more effective than either compound. No significant mortality differences (P < or = 0.05) were observed among the 3 compounds at 15 min, 1 h, 12 h, and 24 h posttreatment when tested against Ae. sollicitans. No significant mortality differences (P < or = 0.05) were observed between the 1:3 and 1:5 (prallethrin: piperonyl butoxide) formulations of Responde at any time posttreatment when tested against Ae. sollicitans.

Aedes↗
PubMed1996

Application of deltamethrin-impregnated bednets for mosquito and malaria control in Yunnan, China.

The results of research in China in recent years show that: 1) Different laboratory sensitivity of adult Anopheles minimus, An. sinensis and Culex pipiens quinquefasciatus to deltamethrin exist in Yunnan. Although the range and duration for the use of permethrin and deltamethrin was limited, resistance of An. minimus, An. sinensis and Cx. pipiens quinquefasciatus to different extent in some areas existed. 2) On walls built with cement and covered with a thin layer of lime on which deltamethrin at a dosage of 0.025 g/m2 was sprayed, 100% of the mosquitos were stricken down within 3 days, 80% at the 15th day, 50% at the 20th day. The residual effectiveness on the bamboo and wood walls was good and could last for over 40 days, but on the mud walls a mortality of only 40% on the spraying day was observed, indicating that deltamethrin was not suitable for this purpose. Deltamethrin spraying reduced total caught mosquitos within 30 days, but there was no difference between the effects of deltamethrin (0.025 g/m2) and DDT (2 g/m2) at the 60th day. Deltamethrin effect on reducing densities of endophilic An. vagus, An. culicifacies and exophilic An. philippinensis was better than that of DDT (lasting over 60 days), but its effect on semi-endophilic An. sinensis lasted only 15 days. Against An. mininus, it showed good effects within 20 days but did not last as long as DDT (60 days). Residual deltamethrin and DDT spraying could both control malaria vectors, reduce the infection of infants by malaria, and reduce malaria parasite carrier rates (within 50 days). 3) Laboratory experiments showed that deltamethrin-impregnated bednets at a dosage of 0.015 g/m2 had a positive effect on An. minimus. The residual effect of unwashed deltamethrin-impregnated bednets at a dosage of 0.015 mg/m2 against An. sinensis was apparent and could last for 13 months. When an impregnated bednet was washed for the first time at the 12th month, its mortality effect on An. sinensis was reduced quickly to lower than 50%. The residual effect could last for 2-3 months when washed at the 6th month, but was lost when washed for the second time at the 12th month. 4) The effects of the impregnated-bednets on An. sinensis were different, even opposite, between different investigations. However, the treated bednets caused the density of An. minimus in houses to fall by 67.94%, and the total density in houses and cattle shelters by 67.91%. Moreover, it could shorten the life span of An. minimus. It did not work on the outdoor density of An. minimus. It is necessary to integrate with other measures, for achieving the desired effect.

Adult↗
PubMed1997

[Preliminary evaluation of the incidence and control of insects--pest control in Polish hospitals].

The evaluation of the infestation and methods of insect disease vectors control in 748 hospitals in Poland in the period of 1990 to 1995 were done. The insect species, places of their occurrence and control agents were analysed. Blattella germanica L. occurred most frequently (71% hospitals). Blatta orientalis and Monomorium pharaonis were found in 40% and 17% hospitals respectively. Kitchens, laundries and baths were most infested. Sometimes insects were found also in central sterilization units and operating theaters. Controls of insects in hospitals were performed one to four times a year mostly by spraying with residual formulation. The control agents contained pyrethroids (mostly permethrin, but also deltamethrin and cypermethrin) and carbamates (bendiocarb, propoxur). Baits with hydramethylnon, boric acid, methoprene and chlorpyrifos were used not very often. The authors suggest reduction in using the spraying agents. The baits are recommended because they delay the development of the resistance to pesticides in controlling insect populations and are safer.

Animals↗
PubMed1998

Travel medicine: helping patients prepare for trips abroad.

One third of persons who travel abroad experience a travel-related illness, usually diarrhea or an upper respiratory infection. The risk of travelers' diarrhea can be reduced by eating only freshly prepared, hot foods. Combination therapy with a single dose of ofloxacin plus loperamide usually provides relief from travelers' diarrhea within 24 hours. Using a diethyltoluamide (deet)-containing insect repellent and wearing permethrin-coated clothing can reduce the risk of malaria, yellow fever and other diseases contracted from insects. Routine immunizations such as tetanus, measles, mumps and rubella, and influenza should be updated if necessary before the patient embarks on the trip. Hepatitis A immunization should be administered to persons traveling to places other than Canada, Australia, New Zealand, Japan and western European countries. Typhoid vaccination should be considered for travelers going to developing countries. Yellow fever immunization is indicated for travelers going to endemic areas of South America and Africa. Malaria prophylaxis with chloroquine is indicated for travelers going to Mexico and Central America. Mefloquine is recommended for those traveling to areas where malaria is resistant to prophylactic treatment with chloroquine. Medical advice for patients planning trips abroad must be individualized and based on the most current expert recommendations.

Humans↗
PubMed1994

[Mechanisms of resistance to organophosphate insecticides, carbamates, and pyrethroids in populations of Musca domestica L. (Diptera: Muscidae)].

Resistance to organophosphorus insecticides (malathion, chlorpyriphos, pyrimiphos-methyl); carbamates (propoxur); and pyrethroids (permethrin, deltametrine, cypermetrine, and lambda cialotrine) was studied in field populations of Musca domestica; results were compared with a susceptible reference strain. The method of topic application was employed in the bioassays; the synergist effect of the s,s,s tributyl phosphorotrioate and of the piperonyl butoxide (PB) was also tested. Biochemical microplate tests were also carried out to determine the presence of esterase and acetylcholinesterase enzymes in the three populations. Generalized resistance to malathion (FR = 264.6; 164.0; 154.7) was observed.

Animals↗
PubMed1994

[Status of insecticide resistance in 4 strains of Musca domestica collected in animal farms].

Resistance to insecticides made from different chemical compounds were studied in 4 strains of Musca domestica collected from 2 poultry farms and 2 cow farms following WHO methodology. A high resistance to malathion was observed (resistance factor values ranging from 102X to 252X), and moderate, to diazinon, fenthion, dichlorvos, DDT, and propoxur. Resistance to the deltametrine and permethrin pyreturins was not observed.

Animal Husbandry↗