Tag Archives: flies

No evidence that current sanitation interventions stop faecal exposure

A systematic review [1] of 29 studies found “little to no effect from sanitation interventions” on “faecal-oral transmission of enteric and other pathogens”. The transmission pathways reviewed included “faecal pathogens or indicator bacteria in drinking water, hand contamination, sentinel toys, food, household and latrine surfaces and soil, as well as flies and observations of human faeces”.

There was some evidence showing the association of sanitation “with reductions in flies and a small effect on observations of faeces”. There was also evidence showing “an inverse relationship between the distance of a water supply from a latrine and level of faecal contamination of such water supply”.

The authors of the review conclude that current sanitation efforts in low-income countries are ineffective and unable to prevent contamination along well-known pathways. This may be because “interventions often fail to achieve universal coverage or use”, which is the subject of another systematic review [2].

As expected from researchers, they are also recommend that more rigorous studies are required to investigate the impact of sanitation interventions on multiple transmission pathways.

Unfortunately this important study is not available as an open access article.

[1] Sclar GD, Penakalapati G, Amato HK, Garn JV, Alexander K, Freeman MC, Clasen T. Assessing the impact of sanitation on indicators of fecal exposure along principal transmission pathways : a systematic review. International Journal of Hygiene and Environmental Health. 2016 Oct 1.DOI:10.1016/j.ijheh.2016.09.021

[2] Garn, J.V., Sclar, G.D., Freeman, M.C., Alexander, K.T., Penakalapati, G., Brooks, P.,Rehfuess, E.A., Clasen, T.F. The impact of sanitation interventions on latrine coverage and latrine use : a systematic review and meta-analysis. International Journal of Hygiene and Environmental Health. 2016 Oct 11.DOI: 10.1016/j.ijheh.2016.10.001

Characteristics of latrines in central Tanzania and their relation to fly catches.

Characteristics of latrines in central Tanzania and their relation to fly catches. PLoS One. 2013 Jul 18;8(7).

Irish S, Aiemjoy K, Torondel B, Abdelahi F, Ensink JH.

The disposal of human excreta in latrines is an important step in reducing the transmission of diarrhoeal diseases. However, in latrines, flies can access the latrine contents and serve as a mechanical transmitter of diarrhoeal pathogens. Furthermore, the latrine contents can be used as a breeding site for flies, which may further contribute to disease transmission. Latrines do not all produce flies, and there are some which produce only a few, while others can produce thousands. In order to understand the role of the latrine in determining this productivity, a pilot study was conducted, in which fifty latrines were observed in and around Ifakara, Tanzania.

Drop-hole modification and trap placement

Drop-hole modification and trap placement

The characteristics of the latrine superstructure, use of the latrine, and chemical characteristics of pit latrine contents were compared to the numbers of flies collected in an exit trap placed over the drop hole in the latrine. Absence of a roof was found to have a significant positive association (t=3.17, p=0.003) with the total number of flies collected, and temporary superstructures, particularly as opposed to brick superstructures (z=4.26, p<0.001), and increased total solids in pit latrines (z=2.57, p=0.01) were significantly associated with increased numbers of blowflies leaving the latrine.

The number of larvae per gram was significantly associated with the village from which samples were taken, with the largest difference between two villages outside Ifakara (z=2.12, p=0.03). The effect of latrine superstructure (roof, walls) on fly production may indicate that improvements in latrine construction could result in decreases in fly populations in areas where they transmit diarrhoeal pathogens.