Turning latrines into fly traps - Various documents on results from research grant

Content - Summary

This library entry contains background documents for a grant that Steve Lindsay is leading and which is funded by the Bill and Melinda Gates Foundation.

Goal(s):
The goal of this project is to design traps that attract, capture and kill flies in latrines in an effort to reduce fly-transmitted diarrheal diseases.

Abstract of Paper 1 (Lindsay et al. 2012):
Background: Chrysomya spp are common blowflies in Africa, Asia and parts of South America and some species can reproduce in prodigious numbers in pit latrines. Because of their strong association with human feces and their
synanthropic nature, we examined whether these flies are likely to be vectors of diarrheal pathogens.
Methodology/Principal Findings: Flies were sampled using exit traps placed over the drop holes of latrines in Gambian villages. Odor-baited fly traps were used to determine the relative attractiveness of different breeding and feeding media. The presence of bacteria on flies was confirmed by culture and bacterial DNA identified using PCR. A median of 7.00 flies/ latrine/day (IQR = 0.0–25.25) was collected, of which 95% were Chrysomya spp, and of these nearly all were Chrysomya putoria (99%). More flies were collected from traps with feces from young children (median = 3.0, IQR = 1.75–10.75) and dogs (median = 1.50, IQR = 0.0–13.25) than from herbivores (median = 0.0, IQR = 0.0–0.0; goat, horse, cow and calf; p,0.001). Flies were strongly attracted to raw meat (median = 44.5, IQR = 26.25–143.00) compared with fish (median = 0.0, IQR = 0.0–19.75, ns), cooked and uncooked rice, and mangoes (median = 0.0, IQR = 0.0–0.0; p,0.001). Escherichia coli were cultured from the surface of 21% (15/72 agar plates) of Chrysomya spp and 10% of these were enterotoxigenic. Enteroaggregative E. coli were identified by PCR in 2% of homogenized Chrysomya spp, Shigella spp in 1.4% and Salmonella spp in 0.6% of samples.
Conclusions/Significance: The large numbers of C. putoria that can emerge from pit latrines, the presence of enteric pathogens on flies, and their strong attraction to raw meat and fish suggests these flies may be common vectors of diarrheal diseases in Africa.

Abstract of paper 2 (Lindsay et al., 2012):
African pit latrines produce prodigious numbers of the latrine fly, Chrysomya putoria, a putative vector of diarrhoeal pathogens. We set out to develop a simple, low-cost odour-baited trap for collecting C. putoria in the field. A series of field experiments was carried out in The Gambia to assess the catching-efficiency of different trap designs. The basic trap was a transparent 3L polypropylene box baited with 50 g of fish, with a white opaque lid with circular entrance holes. We tested variations of the number, diameter, position and shape of the entrance holes, the height of the trap above ground, degree of transparency of the box, its shape, volume, colour, and the attractiveness of gridded surfaces on or under the trap. Traps
were rotated between positions on different sampling occasions using a Latin Square design. The optimal trapping features were incorporated into a final trap that was tested against commercially available traps. Features of the trap that increased the number of flies caught included: larger entrance holes (compared with smaller ones, p,0.001), using conical collars inside the holes (compared with without collars, p = 0.01), entrance holes on the top of the trap (compared with the side or bottom, p,0.001), traps placed on the ground (compared with above ground, p,0.001), the box having transparent sides (compared with being opaque, p,0.001), and with no wire grids nearby (compared with those with grids, p = 0.03). This trap collected similar numbers of C. putoria to other common traps for blow flies. The optimum trap design was a transparent box, with a white plastic lid on top, perforated with 10 conical entrance holes, placed on the ground. Our simple trap provides a cheap, low-maintenance and effective method of sampling C. putoria in the field.

Authors:
Paper 1 1: Lindsay, T. C., Jawara, M., D’Alessandro, U., Pinder M., Lindsay S.W.

Paper 2: Lindsay, S. W., Lindsay, T. C., Duprez, J., Hall, M. J. R., Kwambana, B. A., Jawara, M., Nurudeen, I. U., Sallah, N., Wyatt, N., D’Alessandro, U., Pinder, M., Antonio, M.

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Further documents (not available for download from this website):

Abstract of paper 3:

Lindsay, T. C., Jawara, M., D’Alessandro, U., Pinder, M., Lindsay, S. W. (2013) Preliminary studies developing methods for the control of
Chrysomya putoria, the African latrine fly, in pit latrines in The
Gambia. Tropical Medicine and International Health volume 18 no 2 pp 159–165

Objective
To explore ways of controlling Chrysomya putoria, the African latrine fly, in pit latrines. As pit latrines are a major source of these flies, eliminating these important breeding sites is likely to reduce village fly populations, and may reduce the spread of diarrhoeal pathogens.

Methods
We treated 24 latrines in a Gambian village: six each with (i) pyriproxyfen, an insect juvenile hormone mimic formulated as Sumilarv® 0.5G, a 0.5% pyriproxyfen granule, (ii) expanded polystyrene beads (EPB), (iii) local soap or (iv) no treatment as controls. Flies were collected using exit traps placed over the drop holes, weekly for five weeks. In a separate study, we tested whether latrines also function as efficient flytraps using the faecal odours as attractants. We constructed six pit latrines each with a built-in flytrap and tested their catching efficiency compared to six fish-baited box traps positioned 10 m from the latrine. Focus group discussions conducted afterwards assessed the acceptability of the flytrap latrines.

Results
Numbers of emerging C. putoria were reduced by 96.0% (95% CIs: 94.5–97.2%) 4–5 weeks after treatment with pyriproxyfen; by 64.2% (95% CIs: 51.8–73.5%) after treatment with local soap; by 41.3% (95% CIs = 24.0–54.7%) after treatment with EPB 3–5 weeks after treatment. Flytraps placed on latrines collected C. putoria and were deemed acceptable to local communities.

Conclusions
Sumilarv 0.5G shows promise as a chemical control agent, whilst odour-baited latrine traps may prove a useful method of non-chemical fly control. Both methods warrant further development to reduce fly production from pit latrines. A combination of interventions may prove effective for the control of latrine flies and the diseases they transmit.

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Abstract of Paper 4:

Promoting Health and Advancing Development through Improved Housing in Low-Income Settings
Authors: Andy Haines, Nigel Bruce, Sandy Cairncross, Michael Davies,
Katie Greenland, Alexandra Hiscox, Steve Lindsay, Tom Lindsay, David Satterthwaite, and Paul Wilkinson
Journal of Urban Health: Bulletin of the New York Academy of Medicine
doi:10.1007/s11524-012-9773-8

ABSTRACT
There is major untapped potential to improve health in low-income communities through improved housing design, fittings, materials and construction. Adverse effects on health from inadequate housing can occur through a range of mechanisms, both direct and indirect, including as a result of extreme weather, household air pollution, injuries or burns, the ingress of disease vectors and lack of clean water and sanitation. Collaborative action between public health professionals and those involved in developing formal and informal housing could advance both health and development by addressing risk factors for a range of adverse
health outcomes. Potential trade-offs between design features which may reduce the risk of some adverse outcomes whilst increasing the risk of others must be explicitly considered.

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Documents available for download below:
1 - Development of odour-baited flytraps for sampling the African latrine fly, Chrysomya Putoria, a putative vector of enteric diseases (2012)
2 - Chrysomya Putoria, a putative vector of diarrheal diseases (2012)

Bibliographic information

Lindsay, S. (2013). Turning latrines into fly traps - Various documents on results from research grant. London School of Hygiene and Tropical Medicine, UK

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English Europe & Central Asia Fundamental research and engineering Rural Sub-Saharan Africa

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