Evaluation of Temephos as a Larvicide against Simulium Ochraceum (Diptera: Simuliidae) in Guatemala1

Takaoka, Hiroyuki; Ochoa, J. O.; Takahashi, Mika; Takahasi, Hirosi

doi:10.1093/jmedent/18.2.145

Cited by 9 publications

(4 citation statements)

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“…In the watershed investigated, the critical level of 8000 Sim ulium per person-year (Suzuki, 1983) was exceeded during each of the 5 years prior to starting the larval control. Takaoka et al (1981), Ochoa (1982), and Suzuki (1983) found 0.064% , 0.33% , and 0.099% of¯ies from the study area with infective larvae of O. volvulus, respectively. During control operations, however, the mean density of the vector decreased to zero in about 80% of the collection sites and was less than the critical threshold for transmission (i.e.…”

Section: Discussionmentioning

confidence: 81%

Successful control of onchocerciasis vectors in San Vicente Pacaya, Guatemala, 1984-1989

Ochoa¹,

Castro²,

Barrios³

et al. 1997

Annals of Tropical Medicine And Parasitology

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Between 1984 and 1989, the onchocerciasis-vector control zone on the pilot area of San Vicente Pacaya, Guatemala, which had been subject to experimental control since 1979, was extended from 91.3 to 148.6 km2. Temephos was used as a larvicide against Simulium ochraceum s.l. the target species. As a new strategy, only breeding sites with water discharges of 0.1-10 litres/s were treated, every 2 weeks. This approach provided a substantial reduction in effort, number of treated sites, time and cost. To assess the effect of the temephos, nine sites were selected in which standardized collections of adult Simulium were made twice a month, by human bait. There was an obvious difference between the pre- and post-control mean densities of flies at each site. In the northern area, which includes the Lavaderos, Barretal, Colina and Rodeo sites, the biting density in 1979, before treatment, varied between 10 and 64 flies/man-hour (FMH). Four years later, this had been reduced to 0.1-3.2 FMH, and by the end of the present study, in 1989, the mean density was zero FMH. In the southern area, which lies south-east of Lavaderos (and includes Guachipilin, Ingerto, Pena Blanca and Sierra Morena), the density during the pre-control phase was 24 FMH at one of the two sites investigated at the time and 39.3 FMH at the other. It fell to 0.1-0.5 FMH after 5 years of control and to zero (three sites) or close to zero (< or = 0.5 FMH; one site) for the last 4 years of the present study. To assess the effect of vector control on onchocerciasis prevalence and incidence, 1280 residents from six endemic communities, out of 12,000 permanent inhabitants, were examined. In Santa Cruz, Patrocinio and Los Rios, the prevalence of skin microfilariae in the subjects from each community fell from 8.1%-37.8% during the pretreatment, base-line period to 0.0%-31.5% when the study foci were totally integrated into the vector-control operation following treatment. Incidence among children (aged < or = 9 years) varied from 0%-25% for the period 1982-1984 but, thereafter, not a single case appeared in four of the six study communities (Santa Cruz, Patrocinio, Los Rios and Berlin). Incidence in Guachipilin did not decline appreciably, probably because of human migration into the area from other onchocerciasis foci. The prevalence of nodules followed a similar trend to those of the prevalence and incidence of skin microfilariae, falling from 9.1%-45.0% pre-control to 1.8%-14.3% 10 years later.

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Section: Discussionmentioning

confidence: 81%

Successful control of onchocerciasis vectors in San Vicente Pacaya, Guatemala, 1984-1989

Ochoa¹,

Castro²,

Barrios³

et al. 1997

Annals of Tropical Medicine And Parasitology

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“…The main technique has thus been the rapid release of emulsifiable concentrates (Lee et al, 1975). For the very different conditions of attempting to control 5. ochraceum, an inhabitant of tiny streams in montane forest in Central America, slow release blocks were developed as already discussed (Takaoka et al, 1981;Tabaru et al, 1982). Application techniques must be developed for each special circumstance.…”

Section: Dosage Rates and Application Methodsmentioning

confidence: 99%

“…Pieces of this solid material (2 g or more) are placed in the water inside a wire-mesh basket. The number of 2-g brickettes required to maintain a concentration of 01 mg/litre for 60 min is added to each basket (Takaoka et al, 1981). In this interesting study, all water courses discharging between 0-1 and 50 litres/s were considered to be potential breeding sites (Nakamura et al, 1981).…”

Section: Slow-release Formulationsmentioning

confidence: 99%

The feeding behaviour ofSimuliumlarvae, and the development, testing and monitoring of the use of larvicides, with special reference to the control ofSimulium damnosumTheobald s.l. (Diptera: Simuliidae): a review

Walsh

1985

Bull. Entomol. Res.

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The control of Simulium has always relied largely on the use of insecticides against the larvae, and this is the case in the current large-scale Onchocerciasis Control Programme against the vector S. damnosum Theobald in West Africa. Resistance to temephos has occurred in some vector species, and it is necessary to find alternatives to this preferred larvicide. In order to provide a frame of reference for the development of new larvicides or formulations, the literature relating to larval filter-feeding behaviour is first reviewed in detail. Then the physico-chemical conditions in larval habitats are outlined. The types of formulations and classes of insecticide used in Simulium control are considered, with particular attention being given to emulsifiable concentrate formulations and the reasons for their effectiveness. Particulate formulations, which have been recommended on environmental grounds, are also discussed. Techniques used in the screening of larvicides are considered, and it is concluded that flow-through systems are necessary; mini-gutter tests conducted using water and fauna from rivers to be treated are to be strongly preferred, followed by stream trials. Knowledge of Bacillus thuringiensis var. israelensis as a Simulium larvicide is reviewed in detail. The environmental impact of control of Simulium larvae, both in the tropics and the temperate zone, is extensively reviewed. Throughout, key features which might lead to improved larvicide formulations and testing procedures, together with serious gaps in our knowledge are emphasized.

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“…This control trial began in 1979 in a small valley of Lavaderos, then gradually expanded to other neighboring valleys, with a final coverage of about 90 km 2 in January 1984. An outline of the control operation and the results of entomological evaluations have already been reported [ 41 , 42 ]. Details of the entire program were reported by Yamagata et al [ 43 ] and are excerpted below.…”

Section: Area Vector-control Trialmentioning

confidence: 99%

6) Epidemiology and Control of Guatemalan Onchocerciasis

Takaoka

Suzuki²

2015

Trop.Med.Health

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Recent studies on the epidemiology and control of Guatemalan onchocerciasis, chiefly made by the Guatemala–Japan Cooperative Project on Onchocerciasis Research and Control, are reviewed. Epidemiological features of Guatemalan onchocerciasis are summarized as to characteristic altitudinal distribution of endemic areas, disease manifestation, vector taxonomy, biology and transmission dynamic of the disease. Extensive insecticide studies in the field and laboratory demonstrate that the characteristic situations of Guatemalan streams where Simulium ochraceum, the main vector of onchocerciasis, breeds require ingenious methods of larviciding. Finally, the feasibility of an area vector control is indicated by the successful control operation in the San Vicente Pacaya Pilot Area, in which a new fixed-dose larviciding method was applied.

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Evaluation of Temephos as a Larvicide against Simulium Ochraceum (Diptera: Simuliidae) in Guatemala1

Cited by 9 publications

References 0 publications

Successful control of onchocerciasis vectors in San Vicente Pacaya, Guatemala, 1984-1989

Successful control of onchocerciasis vectors in San Vicente Pacaya, Guatemala, 1984-1989

The feeding behaviour ofSimuliumlarvae, and the development, testing and monitoring of the use of larvicides, with special reference to the control ofSimulium damnosumTheobald s.l. (Diptera: Simuliidae): a review

6) Epidemiology and Control of Guatemalan Onchocerciasis

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