Cholera is a
known waterborne disease which thrives in developing countries, the majority of
cases go unnoticed, yet more severe cases can be fatal. The disease is caused
by the bacteria Vibrio cholera. In
less developed countries rivers and ponds are the primary source of drinking
water for humans and animals, this water is consumed without any treatment to remove
harmful bacteria. Due to financial restraints these countries possess poor sewerage
management meaning contamination regularly occurs as a result of faecal matter finding
its way into the water system. Additionally, during times of high marine and
fresh water phytoplankton blooms there is a subsequent increase zooplankton numbers
(including copepods). Sochard et al.,
(1979) found V.cholerae to be present
in the guts of copepods, adding to bacterial transmission and an increase in cholera
outbreaks.
The study of
Colwell et al., (2003) investigated
the reduction of V.cholerae by filtration
of water before consumption in a feat to remove any zooplankton which may carry
the bacteria. Numerous villages in Bangladesh were employed to trial two
different methods of filtration or a control of no filtration of their drinking
water, a preliminary study using these methods was conducted before the full
study was completed. The full study was conducted for a total of 18 months with
each of the villages being assigned one particular treatment either filtration
using a sari, filtration using a nylon filter or no filter (control). Standardised
procedures were taught to the villagers on how to filter the water they
gathered and how to store water appropriately. The nylon net filters provided
for filtration were 150 µm mesh size and the sari’s were cotton and required
folding 4-8 times to create the ideal filter.
Compliance
of the villagers in maintaining the standardisation of the study was exemplary
and assisted in the success of the study. Due to the small sample number used in
preliminary experimentation, statistical significance was not obtained.
However, due to the higher sample number in the full study there was a significantly
lower number of cholera cases in the nylon and sari filtration groups compared to
the control. Due to the size of the sari and nylon filters copepods and particulate
matter were be removed from the water. Through analysis of the data it was
deemed that there were around half the number of cholera cases when the sari
was used in comparison to no filtration. This led to the conclusion that cases of
cholera were halved when copepods were removed from the water collected for domestic
use. Through laboratory examination the sari was determined to remove all
zooplankton, most phytoplankton and particulate matter greater than 20 µm, the
nylon filter was found to be almost as effective.
As sari
cloth is a common affordable material in Bangladesh and easily obtainable by
the villagers, this adds to its suitability as a filter for untreated water. As
similarly constructed material can be found worldwide at a relatively cheap
cost, its use as a filter can be applied globally to reduce cases of cholera.
These positive steps towards reducing the cholera causing V.cholerae show that there are still financially viable solutions
to waterborne disease control. Applications of simple measures in the
developing world which are cost effective could reduce ill health and reduce
contamination.
Colwell, R.R., Huq, A., Siraul
Islam, M., Aziz, K.M.A., Yunus,M., Huda Khan, N., Mahmuds, A., Sack, B.R.,
NAirre, G.B., Chakraborty,S., Sack, D.A. and Russek-Cohen, E. Reduction of
cholera in Bangladeshi villages by simple filtration. (2003). PNAS. 100 (3) pp. 1051-1055.
References
Sochard,
M.R., Wilson, D.F., Austin, B. and Colwell,R.R. (1979) Bacteria Associated with
the Surface and Gut of Marine Copepods. Applied
Environmental Microbiology. 37 (4) pp. 750-759.
Hi Emma,
ReplyDeleteThanks for the post! It was good to here a bit more about this study, its really neat as the finding can empower local people without the need to wait for aid/government intervention. Do you know how widely this use of cloth was rolled out (no pun intended) across the region after this? Did the authors also speculate as to if this would filter out other pathogens and parasites? Presumably it would be effective against parasitic worms etc.
Kind Regards
Hi Tom,
ReplyDeleteI'm glad you enjoyed it, as you said it shows that education and participation of individuals can assist in the prevention of disease. The research group performed a follow up study on the use of cloth as a filtration device 5 yeas after the original study, this can be viewed through this link, it makes for interesting reading http://mbio.asm.org.plymouth.idm.oclc.org/content/1/1/e00034-10.full.pdf+html. Some villagers were seen to be continuing with the use of cloth as filters, although not all the villagers had continued using filtration there appears to be a reduction in the cases of cholera and its use may even have a positive effect on others in the area not suing filtration. As the saris were folded to remove objects of 150µm or more the majority of organisms of this size would be removed including any parasitic organisms of this size. It is great to see that such simple and affordable methods can assist in the continued prevention of cholera in vulnerable areas.
Thanks
Emma