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At least 811 records · Page 45Linked to original sources
PubMed2006

Larvicidal efficacy and biological stability of a botanical natural product, zedoary oil-impregnated sand granules, against Aedes aegypti (Diptera, Culicidae).

Chemical analysis on Curcuma zedoaria rhizome volatile oil, using gas chromatography-mass spectrometer techniques, demonstrated the presence of beta-tumerone (19.88%), 1,8-cineole (8.93%), and 7-zingiberene (7.84%) as major constituents. Larvicidal efficacy against Aedes aegypti mosquitoes of zedoary oil and its formulated preparation, zedoary oil-impregnated sand granules, were investigated and compared with that of Abate(R)sand (temephos). Zedoary oil exhibited pronounced potential against the fourth instar larvae of A. aegypti with an LC(50) and LC(99) of 33.45 and 83.39 ppm, respectively. Application of zedoary oil at a dosage yielding ten times that of LC(99) offered complete larval mortality (100% mortality) for a period of 3 days, and the larval mortality subsequently decreased to lower than 50% after application for more than 5 days. Zedoary oil-impregnated sand granules provided remarkably longer activity, with a larval mortality of 100% for a period of 9 days; and mortality below 50% was obtained in week 3 of application. The complete larval mortality that resulted from applying temephos at dosages of 0.1 and 1 ppm persisted for a period of 6 days and 4 weeks, respectively, and the larval mortality below 50% was reported on day 18 and week 11, respectively. Testing A. aegypti species against stored samples of zedoary oil-impregnated sand granules demonstrated that the product stored at 4 degrees C showed the longest larvicidal activity, followed by those kept at ambient temperature and 45 degrees C, yielding a complete larval mortality for 9, 8, and 6 days, respectively. Most samples of zedoary oil-impregnated sand granules stored at each temperature for 1 month showed slightly higher efficacy than those kept for 2 months. The larvicidal efficacy of samples stored at 4 degrees C seemed to be comparable to that of the fresh sample. The efficacy in killing A. aegypti larvae and good biological stability of zedoary oil-impregnated sand granules make this product promising as an alternative to essential oil in the development of new botanical natural larvicide for use in mosquito control programs.

Aedes↗
PubMed1983

FLIT-MLO and No. 2 fuel oil: effects of aerosol applications to mallard eggs on hatchability and behavior of ducklings.

FLIT-MLO and No. 2 fuel oil are sprayed on wetlands for mosquito control during spring and summer. In one experiment to assess the effects of the spraying on birds, mallard eggs were sprayed with amounts of No. 2 fuel oil equivalent to 2.34, 4.67, or 18.70 liters/ha or FLIT-MLO equivalent to 9.35, 46.75, or 140.25 liters/ha on Day 6 of incubation. In a second experiment, mallard eggs were sprayed with 9.35, 46.75, or 140.25 liters/ha of FLIT-MLO on Days 3, 6, 12, or 18 of incubation. Hatchability of eggs sprayed with the highest treatment level of each substance was significantly lower than that of controls for the first experiment. Hatchability of eggs sprayed with FLIT-MLO in the second experiment was never significantly lower than that of controls. Ducklings from the first experiment, 36-48 hr old, were cold stressed for 1 hr at 8 degrees C and then immediately tested for their ability to respond to a fright stimulus. Ducklings from the group of eggs sprayed with 140.25 liters/ha of FLIT-MLO ran a significantly shorter distance from the fright stimulus than did controls. The effects of the heaviest exposure to FLIT-MLO (140.25 liters/ha) on egg hatchability and behavior of newly hatched young are uncertain because of the contradictory results for hatching success in the two experiments. However, normal applications of FLIT-MLO (9.35-46.75 liters/ha) or No. 2 fuel oil (2.34-4.67 liters/ha) do not appear to pose a threat to the embryos of breeding birds.

Animals↗
PubMed1983

Biochemical studies on malathion resistance in Anopheles arabiensis from Sudan.

The change from larval to adult mosquito control in the Gezira area of Sudan resulted in a decrease in the prevalence of malaria in this region. House spraying with malathion began in 1975 and resistance to this compound was first detected in 1978. Laboratory tests showed that adult Anopheles arabiensis Patton were resistant to malathion and phenthoate but susceptible to all other organophosphates tested. The larvae of this strain were susceptible to malathion. The malathion resistance in the adults was synergized by triphenyl phosphate, but not by piperonyl butoxide. This suggests that a carboxylesterase enzyme may be the basis of malathion resistance in this strain. Analysis of general esterase levels to alpha- and beta-naphthyl acetate showed that there was no quantitative change in the amount of carboxylesterase enzyme present in the resistant strain as compared to the susceptible. The absence of larval resistance suggests that house spraying rather than agricultural spraying is the major source of selection pressure. The presence of a high level of adult malathion resistance in A. arabiensis may decrease the efficacy of malathion for malaria control in Sudan. The lack of cross-resistance to organophosphates which do not contain a carboxylester bond means that insecticides such as fenitrothion are still practical alternatives.

Animals↗
PubMed1991

Studies on the environmental persistence of S-31183 (pyriproxyfen): adsorption onto organic matter and potential for leaching through soil.

Analytical methods were developed to allow the extraction and analysis of S-31183 (pyriproxyfen), 2-[1-methyl-2-(4-phenoxyphenoxy)ethoxy]pyridine, in organic matter from animal waste-water lagoons. Analysis of water and organic debris from a treated lagoon showed that the active ingredient readily adsorbed onto organic matter. S-31183 persisted on organic matter for over a 2-month period, during which time the concentration decayed at an exponential rate. In leaching trials with four different soil types, over 50% of the active ingredient applied remained in the upper 6 cm of a 30-cm soil column; there was no indication of a rapid potential for downward migration. The use of S-31183 for treating wastewater lagoons at doses which are effective for mosquito control did not result in any apparent problems of environmental incompatibility.

Adsorption↗
PubMed1987

An enzyme-linked immunosorbent assay for detection of flavivirus antibodies in chicken sera.

An enzyme-linked immunosorbent assay (ELISA) was developed to determine the presence of flavivirus antibodies to Murray Valley encephalitis (MVE) and Kunjin viruses in sentinel chicken sera. The development of a quick, reliable assay to detect antibodies to MVE was an essential part of a large-scale surveillance programme to monitor arbovirus activity in Western Australia. This assay was developed for use with alkaline phosphatase conjugated goat anti-mouse IgG using mouse anti-chicken globulin in an intermediate step. There was a significant difference in absorbance values between neutralization test positive and pre-bled sera. However, some sera obtained from sentinel chickens and deemed negative by neutralization demonstrated adsorbance levels above the cutoff level in the ELISA, which reflects the increased sensitivity of this technique. The ELISA test detected antibodies to MVE in chicken sera 7-10 days after infection, whereas these antibodies were only consistently detected by the neutralization test 24 days after infection. Antibodies to both MVE and Kunjin reacted positively with the MVE antigen, but there was little cross-reactivity between this antigen and antibodies to other togaviruses. The main advantages of the ELISA over the neutralization test for detecting antibodies to MVE virus in the sera of sentinel chickens are its greater sensitivity and the speed with which tests can be performed. Results are available within 48 h of receiving specimens and emergency mosquito control measures may then be implemented.

Animals↗
PubMed1990

Influence of an insect growth regulator on the larval development of an estuarine shrimp.

The influence of methoprene, an insect growth regulator used in mosquito control, on larval development of the estuarine grass shrimp (Palaemonetes pugio) was examined in the laboratory. No grass shrimp larvae successfully completed metamorphosis when continuously exposed to 1000 microg methoprene litre(-1). Completion of larval metamorphosis was significantly reduced by exposure to 100 microg litre(-1) of the isomeric mixture (R,S)-methoprene but not the single isomer formulation (S)-methoprene. No statistically significant difference was revealed, however, in ability to inhibit metamorphosis between these two isomeric types across the broad range of exposure concentrations from 0.1 to 1000.0 microg litre(-1). The first two larval stages and the final premetamorphic larval stage were more sensitive to methoprene toxicity than intermediate larval stages. Methoprene exposure did not alter either the duration of total larval development or the total number of larval stages prior to metamorphosis.

Journal Article↗
PubMed1987

Drugs, insecticides and other agents from Artemisia.

Essential oils from Artemisia (wormwood) are of botanical and pharmaceutical interest. They are used in traditional remedies in many parts of the world. In pure form the oil is a narcotic poison. Nearly all species are intensively bitter and strongly aromatic. Extracted substances from the plant have an antibacterial action and some of these substances have potential use in mosquito control. Other properties include toxicity to nematodes and inhibition of seedling growth of. Several chemical compounds have been isolated and identified.

Anthelmintics↗
PubMed1990

Drugs from seaweeds.

Extracts from seaweed are of botanical and pharmaceutical interest. They are used in traditional remedies in many parts of the world. A large number of edible seaweeds are consumed by the coastal peoples of Asia. Extracted substances from the plants have antibacterial actions and some of these substances have potential use in mosquito control. Other properties include antifungal activities and growth inhibition of other plants. Several chemical compounds have been isolated and identified.

Humans↗
PubMed2005

Effects of neem limonoids on the malaria vector Anopheles stephensi Liston (Diptera: Culicidae).

The effects of the neem (Azadirachta indica A. Juss) limonoids azadirachtin, salannin, deacetylgedunin, gedunin, 17-hydroxyazadiradione and deacetylnimbin on Anopheles stephensi Liston (Diptera: Culicidae) were investigated. In exploring advantages of pure neem limonoids, we studied the larvicidal, pupicidal, adulticidal and antiovipositional activity of neem limonoids. Azadirachtin, salannin and deacetylgedunin showed high bioactivity at all doses, while the rest of the neem limonoids were less active, and were only biologically active at high doses. Azadirachtin was the most potent in all experiments and produced almost 100% larval mortality at 1 ppm concentration. In general, first to third larval instars were more susceptible to the neem limonoids. Neem products may have benefits in mosquito control programs.

Animals↗
PubMed2000

Water management for controlling the breeding of Anopheles mosquitoes in rice irrigation schemes in Kenya.

An experiment to assess the impact of intermittent irrigation on Anopheles larval populations, rice yields and water use was conducted in the Mwea rice irrigation scheme in Kenya. Four water regimes including intermittent irrigation were tested in a complete randomized block experimental design. Intermittent irrigation was carried out on a weekly schedule, with flooded conditions from Saturday through Tuesday morning. Larval sampling at each plot was conducted every Monday and prior to draining of intermittently irrigated subplots on Tuesday. All the adult anopheline mosquitoes emerging from larvae collected in the experimental plots were identified as being An. arabiensis. By far the highest numbers of An. arabiensis 1st instar larvae were found in the intermittently irrigated subplots, indicating that the water regime provided the most attractive environment for egg laying. However, the ratio between the 4th and 1st instar larvae in the subplots was only 0.08, indicating very low survival rates. In contrast, the 4th/1st instar ratio for subplots with other water management regimes ranged between 0.27 and 0.68, suggesting a correspondingly higher survival than observed with intermittent irrigation. The total number of 4th instars was almost the same in the intermittently irrigated subplots and the irrigation system normally practised by the farmers. The failure to eliminate larval development up to the 4th instar in the former method was attributed to residual pools of water. Larval abundance fluctuated throughout the 12-week sampling period. The highest larval densities were recorded in the 3 weeks after transplanting the rice seedlings. Afterwards, larval numbers dropped dramatically as the height of rice plants increased. Rice yields at harvest did not show statistically significant differences among subplots with different water regimes. The average yield per hectare ranged from 4.8-5.3 metric tonnes. The average daily water percolation/seepage rate was 3.6 mm and did not significantly differ among different water management regimes. Further research is necessary to, among other things, determine whether rice yields could be increased by having flooded and drained intervals that were different from those used in this study. It would likewise be important to assess on a wider scale the feasibility of implementing intermittent irrigation with respect to farmer acceptance and required changes in irrigation system design and management.

Animals↗
PubMed2002

Characterizing stress gene expression in reef-building corals exposed to the mosquitoside dibrom.

We characterize two genes expressed in Acropora cervicornis upon exposure to 0.5 microg/l of dibrom, a pesticide used for mosquito control in the Florida Keys. Fragments of these genes were isolated, sequenced, and developed into chemiluminescent probes for Northern slot blots. Expression of target transcripts was detected in corals exposed to a variety of stressors including organophosphates, organochlorines, heavy metals, naphthalene, and temperature. Within the context of stressors examined, the D25 probe demonstrates toxicant and concentration specificity for organophosphates, whereas the D50 probe had broader specificity, detecting transcripts in corals exposed to dibrom, naphthalene, and temperature stress. After characterizing specificity in the lab, these probes were used on field samples taken from the Florida Keys. Both probes detected their targets in samples taken from the upper Florida Keys in August 2000. Preliminary search of sequence databases suggest similarity exists between D25 and a thioesterase.

Amino Acid Sequence↗
PubMedDate not supplied

Dengue: emergence as a global public health problem and prospects for control.

Dengue causes more illness and death than any other arboviral infection: there are at least 20 million infections in the world each year and several hundred thousand cases of a severe, life-threatening syndrome known as dengue haemorrhagic fever/dengue shock syndrome (DHF/DSS). In recent years, the geographical range of dengue has extended and DHF/DSS is occurring in new areas and with increased incidence. The reasons for the resurgence are complex, but parallel demographic changes and reduced efforts towards disease control. Control of dengue currently depends on controlling its mosquito vector. However, development of a vaccine offers greater hope in the long-term. The dengue group of flaviviruses is unique in that it comprises 4 distinct serotypes which have the potential to cause sequential infections with increased severity. It is reasoned, therefore, that any vaccine should induce solid immunity to all 4 serotypes. Knowledge regarding dengue immunity and pathogenesis is rapidly advancing and it is reasonable to believe that this information can be used to devise a safe and efficacious vaccine for dengue, but it seems unlikely that this will become available in the near future.

Dengue↗
PubMed2004

Live flavivirus vaccines: reasons for caution.

CONTEXT: Dengue, Japanese encephalitis, tick-borne encephalitis, yellow fever, and West Nile viruses cause substantial morbidity and mortality each year. Modern transportation and the relaxation of mosquito-control measures are largely responsible for the increase of disease caused by flaviviruses. Without effective antiviral drugs, vaccination offers the best chance of decreasing the incidence of these diseases, and live virus vaccines are the most promising and cost effective. However, flaviviruses can recombine, which raises the possibility of recombination between a vaccine strain and wild-type virus resulting in a new virus with potentially undesirable properties. STARTING POINT: Recently, Arunee Sabchareon and colleagues reported up to 90% seroconversion rates in a phase I trial of live-attenuated dengue-virus vaccines in children (Pediatr Infect Dis J 2004; 23: 99-109). Other live flavivirus vaccines have also been tested against dengue, Japanese encephalitis, and West Nile viruses. Thus far, efficacy seems promising. WHERE NEXT: Safety issues with the live flavivirus vaccines need to be recognised and addressed. The theoretical possibility of untoward recombination events can never be entirely dismissed, but steps can be taken to minimise risk. The development of non-live flavivirus vaccines should be encouraged.

Encephalomyelitis, Western Equine↗
PubMed1998

Dengue and dengue haemorrhagic fever.

The incidence and geographical distribution of dengue have greatly increased in recent years. Dengue is an acute mosquito-transmitted viral disease characterised by fever, headache, muscle and joint pains, rash, nausea, and vomiting. Some infections result in dengue haemorrhagic fever (DHF), a syndrome that in its most severe form can threaten the patient's life, primarily through increased vascular permeability and shock. The case fatality rate in patients with dengue shock syndrome can be as high as 44%. For decades, two distinct hypotheses to explain the mechanism of DHF have been debated-secondary infection or viral virulence. However, a combination of both now seems to be the plausible explanation. The geographical expansion of DHF presents the need for well-documented clinical, epidemiological, and virological descriptions of the syndrome in the Americas. Biological and social research are essential to develop effective mosquito control, medications to reduce capillary leakage, and a safe tetravalent vaccine.

Dengue↗
PubMed2001

Chlorinated pesticides and PCBs in sediments and molluscs from freshwater canals in the Hanoi region.

The concentrations of organochlorine pesticides and PCBs were determined in surface sediments and freshwater molluscs (Angulyagra sp.) from water canals in the region of Hanoi city. Results obtained show that the concentration of sigma DDT compounds in sediments range from 7 to 80 ng/g (dry weight) and from 6 to 864 ng/g (dry weight) in the soft tissues of molluscs. The concentrations of sigma DDTs were higher in populated sites and much lower in rural sites, indicating that the DDT has been used for mosquito control and not as a crop protection chemical. Hexachlocyclohexanes (HCHs) have also been widely used in the region but the current environmental concentrations are much lower than those of DDT's, which is due to the less persistence of those compounds. Polychlorinated biphenyls (PCBs) were measured, for example as aroclor 1254, in concentrations up to 40 ng/g (dry weight) and up to 76 ng/g (dry weight) in sediments and molluscs, respectively. Molluscs from water canals are a very popular food in the region. Taking into consideration the high DDT levels measured in these molluscs their consumption is worrisome and may expose the population to high levels of endocrine disrupting substances. Current PCB levels in sediments are lower than usually measured in industrialized countries. Therefore, PCB concentrations in aquatic molluscs are still also relatively low. These snails do not have enzyme ability to metabolize most of the CB congeners and, thus, are passive accumulators and a significant transfer pathway of CBs to consumers. Therefore, measures to phase out the use of these persistent and bioaccumulable chemicals should be adopted in order to prevent further environmental contamination.

Animals↗
PubMed2002

The epidemiology of yellow fever in Africa.

Yellow fever (YF) is still a major public heath problem, particularly in Africa, despite the availability of a very efficacious vaccine. The World Health Organization estimates that there are 200,000 cases of YF annually, including 30,000 deaths, of which over 90% occur in Africa. In the past 15 years, the number of YF cases has increased tremendously, with most of the YF activity in West Africa. This increase in YF activity is in part due to a breakdown in YF vaccination and mosquito control programs. Five genotypes of YF virus have been found in Africa, and each genotype circulates in a distinct geographical region. West Africa genotype I, found in Nigeria and surrounding areas, is associated with frequent epidemics, whereas the three genotypes in East and Central Africa are in regions where YF outbreaks are rare. Other factors, including genetic and behavioral variation among vector species, are also thought to play a role in the epidemiology of YF in Africa.

Aedes↗
PubMed2003

Factors influencing the toxicity of xenobiotics against larval mosquitoes.

In order to examine the factors influencing xenobiotic toxicity against larval mosquitoes, the larvicidal performances of two conventional insecticides (temephos and Bacillus thuringiensis var. israelensis: Bti) and a new potential phyto-insecticide (decomposed leaf litter) were compared under different conditions against three detritivorous larval mosquito types. Bioassays performed under standard conditions indicated differential tolerance levels according to the xenobiotic and the larval type. Bioassays performed under different conditions of xenobiotic dose and geometry of the water column indicated differential effects of those parameters on mortality rates. This allowed us to distinguish the performances of temephos versus those of Bti and leaf litter. These toxicological performances were examined as indicators for analysis of xenobiotic bioavailability for mosquito larvae in environmental water, and also for their comparative interest in field mosquito control.

Aedes↗
PubMed1998

Parasites in paradise: patterns of helminth distribution in hawaiian stream fishes

Of the 13 species of helminths that parasitize stream fishes in Hawai'i, seven species are considered to be native to the archipelago and the remaining six species to be introduced by man. Sources of colonization for native species are piscivorous birds for three species, and marine fishes for four species. Non-native helminths have been brought to Hawai'i in association with the importation of parasitized exotic species of poeciliids introduced into streams for mosquito control and as aquarium releases. Many of these introduced parasites have broad host specificity and now infect the five species of native gobioid stream fishes. Exotic parasites, including a roundworm Camallanus cotti, a tapeworm Bothriocephalus acheilognathi and a leech Myzobdella lugubris, are more widely distributed among Hawaiian streams than are native species.

Journal Article↗