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Efficacy of Electrocuting Devices to Catch Tsetse Flies (Glossinidae) and Other Diptera.

Vale GA, Hargrove JW, Cullis NA, Chamisa A, Torr SJ - PLoS Negl Trop Dis (2015)

Bottom Line: At energies per pulse of 35-215mJ, the efficiency was enhanced by reducing the pulse interval from 3200 to 1ms.Efficiency was low at 35mJ per pulse, but there seemed no benefit of increasing the energy beyond 70mJ.Grids that are less efficient, but more economical, are recommended for studies of relative numbers available to various baits.

View Article: PubMed Central - PubMed

Affiliation: South African Centre for Epidemiological Modelling and Analysis, University of Stellenbosch, Stellenbosch, South Africa; Natural Resources Institute, University of Greenwich, Chatham, United Kingdom.

ABSTRACT

Background: The behaviour of insect vectors has an important bearing on the epidemiology of the diseases they transmit, and on the opportunities for vector control. Two sorts of electrocuting device have been particularly useful for studying the behaviour of tsetse flies (Glossina spp), the vectors of the trypanosomes that cause sleeping sickness in humans and nagana in livestock. Such devices consist of grids on netting (E-net) to catch tsetse in flight, or on cloth (E-cloth) to catch alighting flies. Catches are most meaningful when the devices catch as many as possible of the flies potentially available to them, and when the proportion caught is known. There have been conflicting indications for the catching efficiency, depending on whether the assessments were made by the naked eye or assisted by video recordings.

Methodology/principal findings: Using grids of 0.5m2 in Zimbabwe, we developed catch methods of studying the efficiency of E-nets and E-cloth for tsetse, using improved transformers to supply the grids with electrical pulses of ~40kV. At energies per pulse of 35-215mJ, the efficiency was enhanced by reducing the pulse interval from 3200 to 1ms. Efficiency was low at 35mJ per pulse, but there seemed no benefit of increasing the energy beyond 70mJ. Catches at E-nets declined when the fine netting normally used became either coarser or much finer, and increased when the grid frame was moved from 2.5cm to 27.5cm from the grid. Data for muscoids and tabanids were roughly comparable to those for tsetse.

Conclusion/significance: The catch method of studying efficiency is useful for supplementing and extending video methods. Specifications are suggested for E-nets and E-cloth that are ~95% efficient and suitable for estimating the absolute numbers of available flies. Grids that are less efficient, but more economical, are recommended for studies of relative numbers available to various baits.

No MeSH data available.


Related in: MedlinePlus

Effect of pulse interval on catches of tsetse from grids.A: E.net grid beside cloth. B: E-cloth. Catches at each interval tested are expressed as a percent of simultaneous catches from a control grid operating at a pulse interval of 15ms. Separate comparisons are made at various energy levels (mJ) per pulse, and the results are plotted separately. The test and the control treatments involved in any one plot had the same energy per pulse. Vertical bars through plots indicate the 95% confidence limits of the mean percent. Plots are often displaced a little horizontally to ensure that the confidence limits of the each plot can be distinguished.
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pntd.0004169.g004: Effect of pulse interval on catches of tsetse from grids.A: E.net grid beside cloth. B: E-cloth. Catches at each interval tested are expressed as a percent of simultaneous catches from a control grid operating at a pulse interval of 15ms. Separate comparisons are made at various energy levels (mJ) per pulse, and the results are plotted separately. The test and the control treatments involved in any one plot had the same energy per pulse. Vertical bars through plots indicate the 95% confidence limits of the mean percent. Plots are often displaced a little horizontally to ensure that the confidence limits of the each plot can be distinguished.

Mentions: In a series of experiments with E-net and E-cloth grids the catches at various pulse intervals were compared with those using the 15ms standard. The energy per pulse varied between experiments but within experiments it was always the same for the standard and test frequencies. The results (Fig 4, S2 Table) for each type of grid showed that pulse energy had no clear impact on the effects of pulse frequency. Given the confident limits of the plots, there is some latitude in fitting curves to the frequency data. However, it does seem that the most appropriate curves are complex. Thus, with the E-net (Fig 4A), the catches started to decline when pulse frequency increased above 1ms, but remained roughly level between 15ms and 70ms, before declining sharply to 3200ms. With the E-cloth (Fig 4B) the results were similar except that the catch at intervals of around 1ms seemed hardly greater than 100%, and the section of roughly level catches seemed more extensive, occurring between 5ms and 100ms.


Efficacy of Electrocuting Devices to Catch Tsetse Flies (Glossinidae) and Other Diptera.

Vale GA, Hargrove JW, Cullis NA, Chamisa A, Torr SJ - PLoS Negl Trop Dis (2015)

Effect of pulse interval on catches of tsetse from grids.A: E.net grid beside cloth. B: E-cloth. Catches at each interval tested are expressed as a percent of simultaneous catches from a control grid operating at a pulse interval of 15ms. Separate comparisons are made at various energy levels (mJ) per pulse, and the results are plotted separately. The test and the control treatments involved in any one plot had the same energy per pulse. Vertical bars through plots indicate the 95% confidence limits of the mean percent. Plots are often displaced a little horizontally to ensure that the confidence limits of the each plot can be distinguished.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4631496&req=5

pntd.0004169.g004: Effect of pulse interval on catches of tsetse from grids.A: E.net grid beside cloth. B: E-cloth. Catches at each interval tested are expressed as a percent of simultaneous catches from a control grid operating at a pulse interval of 15ms. Separate comparisons are made at various energy levels (mJ) per pulse, and the results are plotted separately. The test and the control treatments involved in any one plot had the same energy per pulse. Vertical bars through plots indicate the 95% confidence limits of the mean percent. Plots are often displaced a little horizontally to ensure that the confidence limits of the each plot can be distinguished.
Mentions: In a series of experiments with E-net and E-cloth grids the catches at various pulse intervals were compared with those using the 15ms standard. The energy per pulse varied between experiments but within experiments it was always the same for the standard and test frequencies. The results (Fig 4, S2 Table) for each type of grid showed that pulse energy had no clear impact on the effects of pulse frequency. Given the confident limits of the plots, there is some latitude in fitting curves to the frequency data. However, it does seem that the most appropriate curves are complex. Thus, with the E-net (Fig 4A), the catches started to decline when pulse frequency increased above 1ms, but remained roughly level between 15ms and 70ms, before declining sharply to 3200ms. With the E-cloth (Fig 4B) the results were similar except that the catch at intervals of around 1ms seemed hardly greater than 100%, and the section of roughly level catches seemed more extensive, occurring between 5ms and 100ms.

Bottom Line: At energies per pulse of 35-215mJ, the efficiency was enhanced by reducing the pulse interval from 3200 to 1ms.Efficiency was low at 35mJ per pulse, but there seemed no benefit of increasing the energy beyond 70mJ.Grids that are less efficient, but more economical, are recommended for studies of relative numbers available to various baits.

View Article: PubMed Central - PubMed

Affiliation: South African Centre for Epidemiological Modelling and Analysis, University of Stellenbosch, Stellenbosch, South Africa; Natural Resources Institute, University of Greenwich, Chatham, United Kingdom.

ABSTRACT

Background: The behaviour of insect vectors has an important bearing on the epidemiology of the diseases they transmit, and on the opportunities for vector control. Two sorts of electrocuting device have been particularly useful for studying the behaviour of tsetse flies (Glossina spp), the vectors of the trypanosomes that cause sleeping sickness in humans and nagana in livestock. Such devices consist of grids on netting (E-net) to catch tsetse in flight, or on cloth (E-cloth) to catch alighting flies. Catches are most meaningful when the devices catch as many as possible of the flies potentially available to them, and when the proportion caught is known. There have been conflicting indications for the catching efficiency, depending on whether the assessments were made by the naked eye or assisted by video recordings.

Methodology/principal findings: Using grids of 0.5m2 in Zimbabwe, we developed catch methods of studying the efficiency of E-nets and E-cloth for tsetse, using improved transformers to supply the grids with electrical pulses of ~40kV. At energies per pulse of 35-215mJ, the efficiency was enhanced by reducing the pulse interval from 3200 to 1ms. Efficiency was low at 35mJ per pulse, but there seemed no benefit of increasing the energy beyond 70mJ. Catches at E-nets declined when the fine netting normally used became either coarser or much finer, and increased when the grid frame was moved from 2.5cm to 27.5cm from the grid. Data for muscoids and tabanids were roughly comparable to those for tsetse.

Conclusion/significance: The catch method of studying efficiency is useful for supplementing and extending video methods. Specifications are suggested for E-nets and E-cloth that are ~95% efficient and suitable for estimating the absolute numbers of available flies. Grids that are less efficient, but more economical, are recommended for studies of relative numbers available to various baits.

No MeSH data available.


Related in: MedlinePlus