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Pulse-exposure effects of selected insecticides to juvenile Australian crimson-spotted rainbowfish (Melanotaenia duboulayi).

Laboratory toxicity studies were conducted in southeastern Queensland, Australia, to determine the acute lethal effects of a 1-h pulse exposure of selected insecticides to adult and juvenile (<72 h old) crimson-spotted rainbowfish, Melanotaenia duboulayi (Castlenau). In addition, to its ecological significance, this native fish is a predator of mosquitoes. Two organophosphate (OP) compounds (temephos and pirimiphos-methyl), an entomophathogenic bacterium (Bacillus thuringiensis variety israelensis [Bti]) and two insect growth regulators (IGRs) (s-methoprene and pyriproxyfen) were evaluated. Although none of the five insecticides were acutely toxic to adult M. duboulayi under the test conditions, temephos and pirimiphos-methyl were found to be toxic to juveniles, with 24 h pulse exposure LC50 values of 27 and 15 microg/liter (ppb), respectively. Of the two OPs, pirimiphos-methyl was the most toxic, with a lethal dose ratio (pulse exposure LC50 temephos/ pulse exposure LC50 pirimiphos-methyl) of 1.8 (95% CL 0.5-6.4). These pulse exposure LC50 values represented 40 and 4.5% of the estimated environmental concentrations (EEC) for a 15 cm deep water body, respectively. Bti and the two IGRs had no acute toxic effects at up to 10 and 12.5 times the EEC, respectively. Accordingly, in the interests of environmental conservation and integrated pest management (IPM), preference should be given to the latter three insecticides for control of mosquito larvae in juvenile M. duboulayi habitat.

Animals↗

Insecticide susceptibility of Aedes aegypti and Aedes albopictus across Thailand.

Aedes aegypti (L.) and Aedes albopictus (Skuse), two important vectors of dengue fever and dengue hemorrhagic fever, were collected from Mae Sot, Nakhon Sawan, Nakhon Ratchasima, Surat Thani, and Phatthalung, Thailand, from July 2003 to April 2004. The patterns of insecticide susceptibility to temephos, malathion, and permethrin of both Ae. aegypti and Ae. albopictus larvae were determined. Ae. aegypti from all study sites were resistant to permethrin, they but were susceptible to malathion. Resistance to temephos was detected in all strains of Ae. aegypti, except those from Nakhon Ratchasima. Ae. albopictus larvae had low levels of resistance to all three insecticides, except Mae Sot and Phatthalung strains, which were resistant to permethrin.

Aedes↗

Evaluation of temephos and chlorpyrifos-methyl against Culex pipiens (Diptera: Culicidae) larvae in septic tanks in Antalya, Turkey.

The larvicidal activity of chlorpyrifos-methyl and temephos was evaluated against Culex pipiens L. (Diptera: Culicidae) in septic tanks in Antalya, Turkey. Chlorpyrifos-methyl (Pyrifos MT 25 emulsifiable concentrate [EC] ) was evaluated at application rates of 0.04, 0.08, and 0.12 mg active ingredient (AI)/liter, and temephos (Temeguard 50 EC) was evaluated at 0.02, 0.04, and 0.06 mg (AI)/liter during a 21-d study. Generally, overall larval reduction in septic tanks from single- and multifamily dwellings treated with either larvicide was significantly greater than pretreatment levels and control tanks for the duration of the study. At 14 d posttreatment, duration of control was greatest in multifamily tanks treated with chlorpyrifos-methyl at the highest application rate with similar levels of control through 21 d for single-family dwellings (range 97-100%). Septic tanks from both types of family dwellings treated at the highest application rate of temephos resulted in >90% reduction through day 21 (range 91-100%). Laboratory bioassays of septic tank water treated at field application rates, without daily dilution, revealed that complete larval mortality was achieved for 21 d at each application rate and formulation. It is thought that daily addition of water and organic matter to the septic tanks in the single and multifamily dwellings influenced the duration of effectiveness of the larvicides.

Analysis of Variance↗

Cross-resistance to pyrethroid and organophosphorus insecticides induced by selection with temephos in Aedes aegypti (Diptera: Culicidae) from Cuba.

A sample of Aedes aegypti (L.) from Santiago de Cuba, Cuba, with a high level of temephos resistance (19.58x at the 50% lethal concentration [LC50]), was subjected to temephos selection to evaluate the utility of this organophosphate insecticide for mosquito control. High resistance developed after six generations of selection (200.00x). Little or no cross-resistance was observed to the organophosphates, malathion and fenitrothion, but high cross-resistance was observed for the pyrethroid deltamethrin (337.5x) and the organophosphate fenthion (12.74x). Synergism tests implicated detoxifying esterases in temephos and fenthion resistance and deltamethrin resistance was associated with a cytochrome P450 monooxygenasa. Biochemical tests, polyacrylamide gel electrophoresis (PAGE), and inhibition studies confirmed the presence of elevated esterase activity associated with temephos resistance. Pyrethroid resistance could be associated with a glutathione-S-transferase mechanism but not the esterases. The cross-resistance to deltamethrin from temephos selection could limit the use of both insecticides for Ae. aegypti control.

Aedes↗

Evolution of resistance under insecticide selection pressure in Culex pipiens quinquefasciatus (Diptera, Culicidae) from Martinique.

Population surveys of Culex pipiens quinquefasciatus carried out in 1991 and 1999 were compared with data collected in 1990 before the beginning of the control program against this mosquito. Larval samples collected in 1999 displayed resistance to the four tested insecticides: permethrin, propoxur, temephos, and chlorpyrifos. Temephos resistance ratio at LC50 (RR50) ranged between 8.1- and 42-fold compared with 2.9- and 4.6-fold in 1990, and chlorpyrifos RR50 ranged between 8.6- and 123-fold compared with 6.4- and 19-fold in 1990. This increased resistance to organophosphorus insecticides was associated with a sharp decrease of susceptible genotypes at two loci (Ester and ace-1), as well as to an allele replacement at the Ester locus.

Animals↗

Susceptibility of the leaf-eating beetle, Galerucella calmariensis, a biological control agent for purple loosestrife (Lythrum salcaria), to three mosquito control larvicides.

We evaluated the susceptibility of Galerucella calmariensis, a species used to control purple loosestrife (Lythrum salicaria), to three mosquito control larvicides. Larvae and adults were fed loosestrife cuttings dipped in Abate (< or = 375 g x L(-1)), Altosid (< or = 250 g x L(-1)), and Bacillus thuringiensis var israeliensis (Bti) (< or = 110 g x L(-1)). Eggs on cuttings were dipped in the same concentrations. Pupae were immersed in Abate and Altosid solutions (< or = 474.4 microg x L(-1) and < or = 1,169.2 microg x L(-1), respectively). Hatching success of eggs dipped in Abate (> or = 3.75 g x L(-1)) was reduced significantly and survival was significantly lower among larvae and adults eating cuttings dipped in Abate (> or = 0.17 g x L(-1) and > or = 2.27 g x L(-1), respectively). Hatching success of eggs dipped in Altosid (> or = 2.52 g x L(-1)) was reduced significantly. With exposure to Altosid, larval survival to pupation and adult emergence was reduced significantly at concentrations of > or = 2.92 g x L(-1) and > or = 0.63 g x L(-1), respectively. Altosid (> or = 0.23 g x L(-1)) also delayed the onset of pupation and adult emergence among larvae that survived to pupate. Larvae that survived with exposure to Altosid (> or = 1.72 g x L(-1)) grew to 70% larger than those exposed to lower concentrations. Pupal survival was unaffected with exposure to Abate and Altosid and adult survival was unaffected with exposure to Altosid. Bacillus thuringiensis var israeliensis did not adversely affect any life stage of G. calmariensis. The mean Abate concentration on cuttings exposed to operational spraying was in the range that reduced egg hatchability and adult survival but was higher than concentrations that caused complete mortality of larvae. The mean Altosid concentration on cuttings exposed to operational spraying was in the range that reduced hatching success in eggs and delayed pupation and adult emergence of larvae.

Animals↗

Response of Aedes aegypti (Diptera: Culicidae) larvae to three xenobiotic exposures: larval tolerance and detoxifying enzyme activities.

The ability of mosquito larvae to tolerate toxic compounds (temephos, Bacillus thuringiensis var. israelensis, toxic vegetable leaf litter) was examined on a laboratory larval strain of Aedes aegypti L. Bioassays and detoxifying enzyme activity measurements were performed to compare tolerance/resistance capacities. The possibility of a functional plasticity of detoxifying equipment was investigated through experimental determination of the inductive effect of each xenobiotic within a given generation. In the same way, the selective effect of a toxic leaf litter was also investigated along successive generations. Results revealed that differential cytochrome P450 monooxygenase, esterase, and glutathione S-transferase activity levels correlated with the bioassay results. Both induction and selection increased larval tolerance to the xenobiotics used and increased the levels of larval detoxifying enzyme activities.

Aedes↗

Laboratory evaluation of susceptibility of natural subpopulations of Aedes aegypti larvae to temephos.

Aedes aegypti showed the ability to develop resistance to different insecticides, including temephos, the most widely used larvicide. The objectives of this work were to 1) determine the resistance value of 4 natural subpopulations of Ae. aegypti, identified by their different haplotypes, to the insecticide temephos "Abate 1G (1%)"; 2) determine the lethal concentration (LC)50 and LC90 values by using the Rockefeller strain as control; and 3) estimate the resistance ratios. Mosquito samples were collected in Catamarca, Córdoba, and Posadas (Argentina) and in Yacuiba (Bolivia). Six insecticide concentrations were tested. The Rockefeller strain and the Posadas sample showed susceptibility to the diagnostic concentration (0.012 mg/liter), whereas the mortality in Catamarca was 87%. In the Yacuiba and Córdoba collections, mortality was 74% and 75%, respectively, indicating resistance. These results were coincident with those of the Probit analysis from which the highest resistance ratios were estimated for the last 2 subpopulations (5.2 and 4.9, respectively). Before this study, no information was available about the existence of resistance in natural populations of Ae. aegypti in the studied area.

Aedes↗

Cameroon: an African model for final stages of guinea worm eradication.

The Cameroon Guinea worm eradication program initiated case containment activities in 1991 in the Mayo-Sava Division, the only endemic region in the country. These activities differed from the Pakistan program, the only other operational model for dracunculiasis case containment, in two important ways. In Cameroon, next-level supervisors received reports of new cases from village health workers during routine weekly visits to endemic villages. The Pakistan program established a faster case reporting scheme that allowed higher level personnel (sector supervisors and regional managers) to confirm cases within one week of worm emergence. Second, in Cameroon case containment activities were extended only to villages reporting five or more cases the previous transmission season and villages with recent confirmed cases. In Pakistan, all villages reporting cases during the previous year were included in the program. A village-by-village case search one year after initiation of case containment in the Mayo-Sava indicated decreases of 60% in the number of cases and 51% in the number of villages reporting cases. Based on the apparent success of the efforts in Cameroon, we propose a two-stage scheme for implementation of case containment. Both stages are based on rapid detection and containment of cases, within 24 hr of worm emergence, by village-based health workers. In stage 1, cases are reported and confirmed during routine weekly visits to the endemic villages by next-level supervisors. Weekly reporting should be extended to all villages with recent confirmed cases and to as many villages reporting cases during the previous transmission season as logistically possible.(ABSTRACT TRUNCATED AT 250 WORDS)

Cameroon↗

Dracunculiasis eradication: delayed, not denied.

By the end of 1998, Asia was free of dracunculiasis (Guinea worm disease), with Pakistan, India, and Yemen having interrupted transmission in 1993, 1996, and 1997, respectively. Transmission of the disease was also interrupted in Cameroon and Senegal during 1997. Chad reported only 3 cases during 1998. Dracunculiasis is now confined to only 13 countries in Africa. The overall number of cases has been reduced by more than 97% from the 3.2 million cases estimated to have occurred in 1986 to 78,557 cases reported in 1998. Because the civil war in Sudan remains the major impediment to eradication of dracunculiasis, the interim goal is to stop all transmission outside that country by the end of 2000. The most important operational need now is for national programs to improve the frequency and quality of supervision of village-based health workers in order to enhance the sensitivity of surveillance and effectiveness of case containment.

Africa South of the Sahara↗

Selection and characterization of temephos resistance in a population of Aedes aegypti from Tortola, British Virgin Islands.

A collection of Aedes aegypti from Tortola, British Virgin Islands, with a high level of temephos resistance (46.8-fold at the 95% lethal concentration [LC95]) was selected to higher resistance with temephos in the laboratory. After 13 generations of pressure, the temephos resistance ratio increased to 180.6 (LC95), whereas in the absence of selection pressure the resistance ratio declined to 8.5. Relatively low levels of resistance or cross-resistance to other organophosphate and carbamate insecticides, and a high level of resistance to the pyrethroid permethrin were also observed. Synergism tests implicated detoxifying esterases in temephos resistance and the presence of elevated esterase activity was confirmed by biochemical tests; however, no evidence was found of insensitive acetylcholinesterase. Mendelian crosses indicated that temephos resistance was inherited as a monofactorial trait. The presence of high levels of temephos and permethrin resistance in Ae. aegypti has important implications for Aedes control programs.

Aedes↗

Effects of temephos (Abate 4E) on fiddler crabs (Uca pugnax and Uca minax) on a Delaware salt marsh.

The nontarget effects of temephos (as Abate 4E, 44.6% active ingredient) on fiddler crabs were examined on the salt marsh at Bombay Hook National Wildlife Refuge, near Dover, DE. Six 170 x 170-m plots were established; 3 were sprayed on 4 occasions at a rate of 1.5 fl oz/acre (0.054 kg active ingredient/ha) and 3 were controls. On each plot, marsh fiddler crab (Uca pugnax) populations were monitored by repeatedly counting the number of burrow holes in 2 counting areas marked out along tidal guts. One half of each counting area was covered with bird netting to evaluate sublethal toxic effects, which, if present, could result in increased susceptibility to bird predation. A statistically significant linear association was established between the number of holes and the number of crabs. No significant differences were found in the numbers of holes (or crabs) in the sprayed vs. control plots and in the covered vs. uncovered sections. However, survival of juvenile crabs in in situ bioassays was significantly reduced (16% lower) by the spraying. Median acetylcholinesterase activity in claw muscle of red-jointed fiddler crabs (Uca minax) collected 2 days after an operational spray with Abate 4E was significantly reduced (28% lower) compared to unsprayed crabs. In view of the toxicity to juvenile crabs and the cholinesterase inhibition, we recommend continued monitoring and research for nontarget impacts of Abate 4E on fiddler crabs to establish whether the reported level of cholinesterase inhibition results in acute or chronic toxicity.

Acetylcholinesterase↗

Field efficacy and nontarget effects of the mosquito larvicides temephos, methoprene, and Bacillus thuringiensis var. israelensis in Florida mangrove swamps.

We compared the efficacy and nontarget effects of temephos, Bacillus thuringiensis var. israelensis (B.t.i.), and methoprene applied by helicopter to control mosquito larvae in mangrove swamps on Sanibel Island, FL, in May 1997. Three sites per treatment and 3 untreated sites were used. Temephos (Abate) was applied at 37 ml/ha (43% active ingredient [AI]), B.t.i. granules (Vectobac G) were applied at 5.606 kg/ha (200 International Toxic Units/mg), and methoprene (Altosid ALL) was applied at 213 ml/ha (5% AI). Efficacy was quantified by monitoring the survival of caged and uncaged larval Aedes taeniorhynchus. We quantified mortality of sentinel nontarget amphipods (Talitridae) at all sites, monitored the effect of temephos on flying arthropods using light traps, and collected dead insects in tarps suspended under mangroves in areas treated with either temephos or methoprene. Each pesticide showed good overall efficacy but occasional failures occurred. No detectable mortality of amphipods or flying insects attributable to pesticides was found. The inconsistent field efficacies of the pesticides indicate a need for reinspection of treated sites in this habitat.

Aedes↗

Insecticide susceptibility status of Culex tritaeniorhynchus giles, vector of Japanese encephalitis in Delhi.

Laboratory studies were carried out to ascertain the current susceptibility status of adult and larval stages of the Culex tritaeniorhynchus mosquito, vector of Japanese encephalitis, to various insecticides used under public health programs in India. The present study revealed that exposure of adult mosquitoes to diagnostic concentrations of DDT - 4.0%, malathion - 5.0%, fenitrothion - 1.0%, and propoxur - 0.1% could induce only 50.0, 10. 0, 15.0, and 5.0% mortality, respectively, indicating that the species was resistant to all of these insecticides. The LT50 and LT95 values calculated using diagnostic concentrations of DDT, malathion, fenitrothion, and propoxur were found to be 56.4 and 136, 138 and 272, 185 and 258, and 187 and 249 min, respectively. However, when adult mosquitoes were exposed to the diagnostic concentration of synthetic pyrethroids, viz., deltamethrin - 0.025%, permethrin - 0.25%, and lambdacyhalothrin - 0.1%, 100.0% mortality was observed, indicating that the species was highly susceptible to these adulticides. Larval susceptibility tests carried out using diagnostic dosages of DDT- 0.008, temephos- 0.02, fenthion- 0.008, fenitrothion- 0.125, and malathion- 0.005 mg/l failed to induce any mortality, indicating that larvae were resistant to these larvicides. The LC50 and LC90 values calculated for commonly used larvicides, viz., temephos and fenthion, were 0.1511 and 1.9098, and 0.6151 and 2.395 mg/l, respectively. Increase in tolerance level were estimated at 95.5- and 299.4-fold when these LC90 values were compared with diagnostic dosages of temephos and fenthion, respectively.

Animals↗

[The community and the control of Aedes aegypti: perception and behavior regarding temephos larvicide].

Given the persistence of Aedes aegypti foci in the Santiago de Cuba municipality in 1998, a survey was made among the dwellers of the houses to find out their acceptance and behaviour in relation with temephos, to precise over the reasons why the product was not kept in water containers and to know the aspects associated with the existence of foci and their control. It was found that there were filled water tanks in houses where there was daily water supply so that dirt can deposit and water be used later. In 72.2% of the houses, water tanks were washed and refilled every 4 day approximately. It was concluded that water dirtiness was an additional factor to keep water in tanks, the use of temephos(abate) in water tanks for domestic use did not meet the objective pursued by this larvicide, the role of fumigation was overvalued and lack of appropriate knowledge may influence the behaviour of these surveyed persons.

Aedes↗

Efficacy of a flowable concentrate formulation of Bacillus thuringiensis (H-14) against larval mosquitoes in southern Iran.

A flowable concentrate formulation of Bacillus thuringiensis (H-14) [Bactimos FC (1000 ITU/mg)] was evaluated for the control of mosquito larvae in simulated ponds and natural breeding sites in Kazeroun (Fars Province), southern Iran. A comparison was made with Abate emulsifiable concentrate. Bactimos FC caused 93-96% anopheline and 97% culicine larval mortality 24 h posttreatment in simulated ponds and natural breeding sites, when used at the rate of 0.2 cc/m2. Abate (0.015 cc/m2) resulted in significantly higher anopheline (98.1%) and culicine (100%) mortality at 24 h posttreatment. There was a relatively sharp decline in larval mortality 48 h posttreatment when Bactimos FC was applied. Five-day applications were suggested to prevent pupal production.

Analysis of Variance↗

Efficacy of two temephos formulations against Chironomus salinarius (Diptera: Chironomidae) in the saltwater lagoon of Venice, Italy.

Two formulations of the organophosphorus insecticide, temephos (Abathion Granulare, 1% AI granular and Tambro Compresse, 2% AI tablet) were evaluated against Chironomus salinarius midge larvae in 50 x 50 m experimental plots in the saltwater lagoon of Venice, Italy. Each formulation was applied at 0.2 and 0.4 kg AI/ha. Abathion Granulare produced 56 to 73% larval reduction at 0.2 kg AI/ha and 69 to 83% reduction at 0.4 kg AI/ha during 3 wk after treatment. Abathion Granulare lost effectiveness at 4 wk after application at both rates. Posttreatment larval reductions resulting from Tambro Compresse applications ranged from 77 to 86% for 3 wk, and 82 to 92% for 4 wk at rates of 0.2 and 0.4 kg AI/ha, respectively. The tablet formulation (Tambro Compresse) gave better control of C. salinarius (magnitude and duration) than the granular formulation (Abathion Granulare) in these evaluations.

Animals↗