Chapter 7 Health Issues Related to Drainage Management

8/20/2019 Chapter 7 Health Issues Related to Drainage Management

1/16

Chapter 7 - Health issues related to drainage water management

Martin S. FritschSwiss Federal Institute of Technology, Zurich, Switzerland

The interactions between drainage, water management and healthWater related diseases and their vectorsWater-borne excreta related infectionsHealth risks and chemical pollutionIntegrated control of transmission of vector-borne diseasesEnvironmental management measures in drainage water managementDevelopment of control strategies

The interactions between drainage, water management and health

roper surface and subsurface drainage to remove excess water in a safe and timel! mannerpla!s an important role in controlling water related diseases" #areful control and appropriatereuse of drainage water can help protect the environment and optimi$e the use of waterresources"

The health issues related to drainage water management can be grouped in three categories%

i" water related vector-borne diseases&ii" faecal'orall! transmitted diseases& andiii" chronic health issues related to exposure to residues of agrochemicals"

In tropical and subtropical regions there is a close link between the presence of excess water(due to lack of ade)uate drainage* and the transmission of water related vector-borne diseases"+alaria, schistosomiasis (bilhar$iasis* and l!mphatic filariasis are important water relatedvector-borne diseases" Despite control programmes, health services and available treatments,these diseases toda! represent a growing health problem"

Water related vector-borne diseases are caused b! bacteria, viruses and parasites (proto$oaand helminths* transmitted b! water related disease transmitting agents, also called vectors or

http://www.fao.org/docrep/w7224e/w7224e0b.htm#the%20interactions%20between%20drainage,%20water%20management%20and%20healthhttp://www.fao.org/docrep/w7224e/w7224e0b.htm#water%20related%20diseases%20and%20their%20vectorshttp://www.fao.org/docrep/w7224e/w7224e0b.htm#water%20borne%20excreta%20related%20infectionshttp://www.fao.org/docrep/w7224e/w7224e0b.htm#health%20risks%20and%20chemical%20pollutionhttp://www.fao.org/docrep/w7224e/w7224e0b.htm#integrated%20control%20of%20transmission%20of%20vector%20borne%20diseaseshttp://www.fao.org/docrep/w7224e/w7224e0b.htm#environmental%20management%20measures%20in%20drainage%20water%20managementhttp://www.fao.org/docrep/w7224e/w7224e0b.htm#development%20of%20control%20strategieshttp://www.fao.org/docrep/w7224e/w7224e0b.htm#water%20related%20diseases%20and%20their%20vectorshttp://www.fao.org/docrep/w7224e/w7224e0b.htm#water%20borne%20excreta%20related%20infectionshttp://www.fao.org/docrep/w7224e/w7224e0b.htm#health%20risks%20and%20chemical%20pollutionhttp://www.fao.org/docrep/w7224e/w7224e0b.htm#integrated%20control%20of%20transmission%20of%20vector%20borne%20diseaseshttp://www.fao.org/docrep/w7224e/w7224e0b.htm#environmental%20management%20measures%20in%20drainage%20water%20managementhttp://www.fao.org/docrep/w7224e/w7224e0b.htm#development%20of%20control%20strategieshttp://www.fao.org/docrep/w7224e/w7224e0b.htm#the%20interactions%20between%20drainage,%20water%20management%20and%20health


2/16

intermediate hosts" vector is an animal, often an insect, that transmits an infection from oneperson to another person or from infected animals to humans (#airncross and eachem, ./01*"+ost infections can onl! be transmitted b! a particular, disease-specific vector, e"g", malariab! Anopheles mos)uitoes" n intermediate host has a similar role to a vector" However, such anorganism does not activel! transmit a pathogen, like freshwater snails in the case ofschistosomiasis" 2ectors and intermediate hosts represent critical elements in various disease

transmission c!cles of parasitic water related diseases" In general, the! live in or near a)uaticenvironments"

Direct pathogen transfer and the transmission b! vectors and intermediate hosts re)uire specificenvironmental and socio-economic conditions" The conditions are defined b!%

i" )ualit! and )uantit! of water&ii" t!pe and fre)uenc! of human-water contacts&iii" number and distribution of vector or intermediate host breeding sites& andiv" exposure of humans to vector and intermediate host populations"

#onse)uentl!, the above-mentioned diseases can also be associated either directl! or indirectl!with the design and management of treatment and disposal plants for the re-use, treatment ordisposal of drainage water" The ke! criteria for such a health risk are%

i" introduction of temporar! or permanent open water surfaces bodies, e"g", constructed wetland,stabili$ation ponds, or evaporation ponds&

ii" suitabilit! of such water for vector breeding&

iii" accessibilit! for the local population&

iv" location in relation to human settlements and transport links (e"g", roads*& and

v" pollution b! organic or inorganic substances"

+isuse and lack of maintenance are the two main reasons wh! drainage structures (roaddrainage ditches, culverts, dam site drainage or drainage canals in irrigation schemes, and alsodrainage water treatment and disposal facilities* are often associated with environmental healthproblems" armers, associations or national agencies generall! conduct regular maintenanceon irrigation canals" Water )ualit! and flow velocit! are relativel! high" However, in drainagefacilities the opposite conditions are fre)uent" 3ilting, uncontrolled a)uatic weed growth, slowwater flow or stagnant pools associated with the resulting wetlands offer ideal breedingconditions for mos)uitoes and a)uatic snails" armers seem to concentrate on irrigation watermanagement rather than on drainage management"

+oreover, there is often a lack of ade)uate domestic water supplies and sanitation facilities"Thus, drainage canals or drainage water treatment and disposal facilities are often misused forwashing, drinking and uncontrolled disposal of human excreta or other waste b! the poorestand, thus, most vulnerable social groups" In this wa!, drainage water contributes to diseasetransmission"

Water related diseases and their vectors


3/16

Incidence of diseases - cases and mortalit!2ector-borne diseases% transmission b! insectsWater-based diseases% transmission b! a)uatic and semi-a)uatic snails

Incidence of diseases - cases and mortality

lthough the eradication of diseases such as malaria has long been an ob4ective, the problem isfar from being solved" ccording to the most recent information (WH5, .//6* the malariasituation is serious and deteriorating" 7lobal malaria mortalit! is estimated at ."8-9"6 million andglobal malaria cases at 1::-8:: million" +alaria is one of the most serious health problemsfacing frican countries and a ma4or limitation on their socio-economic progress" #hildren underthe age of five and pregnant women are most at risk" WH5 (.//6* reports that /: percent of theglobal burden of this disease can be attributed to environmental factors, including land and

water management"

3chistosomiasis is almost as widespread as malaria but rarel! causes immediate death" nestimated 9:: million people are infected and transmission occurs in about 6; countries" Theinfection is primaril! common in children who pla! in water inhabited b! the snail intermediatehost" Water development pro4ects, especiall! those associated with the irrigation of large areas,have often been associated with an increased incidence of schistosomiasis" Intestinalschistosomiasis was unknown or infre)uent in the *"

+alaria is transmitted b! the bite of a mos)uito of the genus Anopheles. The transmission c!cleis onl! between man and mos)uitoes" +an acts as the intermediate host or reservoir and the

http://www.fao.org/docrep/w7224e/w7224e0b.htm#incidence%20of%20diseases%20cases%20and%20mortalityhttp://www.fao.org/docrep/w7224e/w7224e0b.htm#vector%20borne%20diseases:%20transmission%20by%20insectshttp://www.fao.org/docrep/w7224e/w7224e0b.htm#water%20based%20diseases:%20transmission%20by%20aquatic%20and%20semi%20aquatic%20snailshttp://www.fao.org/docrep/w7224e/w7224e0b.htm#incidence%20of%20diseases%20cases%20and%20mortalityhttp://www.fao.org/docrep/w7224e/w7224e0b.htm#vector%20borne%20diseases:%20transmission%20by%20insectshttp://www.fao.org/docrep/w7224e/w7224e0b.htm#water%20based%20diseases:%20transmission%20by%20aquatic%20and%20semi%20aquatic%20snails


4/16

mos)uitoes as the vector" roto$oan parasites of the genus Plasmodium have to undergocomplex development and multiplication processes both in man and mos)uito before the! canbe further transmitted" 5nl! the female mos)uitoes are of importance for transmission, as the!need a blood meal for oviposition"

+alaria covers not onl! all developing countries, but is present on almost the entire land surface

between the latitudes ;:?< and >:?3" However, the distribution is not uniform and dependsmainl! on climate, altitude, population densit! and the specific environmental re)uirements ofthe mos)uitoes species"

Highl! endemic areas are sub-3aharan frica, #entral merica and the northern part of 3outh merica, the Indian subcontinent and 3outheast sia"

In the last two decades, a growing number of malaria cases have been observed (WH5, .//>*"However, this cannot onl! be explained b! the increasing population" To a large extent, this isalso due to the increasing number of W@Ds such as irrigation and drainage schemes or h!dro-electric dams" With the introduction of new open water surfaces in the form of canals, pondsand artificial lakes, new mos)uito breeding sites have been created"

However, the persistence of the disease is also due to the absence of effective long-lastingvaccines, and the growing resistance of malaria pathogens and mos)uitoes to treatment andinsecticides, respectivel!" A! the end of ./08, 8: of the .8: potential malariatransmitting Anopheles species were alread! recorded to be resistant to one or more pesticides(including DDT*" t least .. of those 8: species are known to be important and dangerousmalaria transmitters (WH5, ./0/*"

urthermore, malaria transmission is not onl! related to W@Ds" Deforestation, mining, roadconstruction and all the negative conse)uences of rapid and uncontrolled urbani$ation are alsocontributing to the creation of mos)uito breeding sites" In this context, urban drainage pla!s twoke! roles" 5n the one hand, it is an essential and effective tool for reducing and eliminatingmos)uito breeding sites b! controlling surface water and waterlogging and b! eliminatingunnecessar! open water surfaces" However, on the other hand poorl! maintained drainagecanals can represent potential breeding sites for various mos)uito species if the! arepermanentl! flooded and a)uatic weeds are not cleared"

inall!, a fresh risk might result from climatic change" irst reports suggest that global warmingcan change the geographical distribution of mos)uito breeding and shift the malariatransmission border line to the north (WH5, .//>*"

ymphatic filariasis

+os)uito-borne filariasis includes a group of diseases which lead to inflammations andobstructive lesions of the l!mphatic s!stem" ilarial parasites are nematode worms, which alsoneed an insect to complete their life c!cle" The main disease is !uchereria"ancrofti or elephantiasis and is transmitted b! mos)uitoes of the genera #ule$.During a bite, amos)uito might take up a number of microfilariae which then undergo a development c!cle inthe mos)uito" When the infected mos)uito bites again, the infectious larvae enter first the skinand then the l!mph vessels and l!mph glands" Bnlike malaria, filarial infection re)uires repeatedand length! exposure to the vector due to the low pathogen load per bite" or !. "ancrofti, longexposure to repeated infection will finall! lead to severe and disfiguring deformities of the legs,


5/16

arms and genitals" C!mphatic filariasis affected about .9: million people in .//;& 0:= of caseswere reported either from tropical frica or India (WH5, .//>*"

lthough filariasis is more of a serious urban health problem, it can cause significant healthha$ard in rural settlements and farming communities where poor surface drainage, lack ofsanitation facilities and environmental pollution through uncontrolled waste and excreta disposal

are prevalent" The principal vector, #ule$ %uin%uefasciatus &fatigans', breeds in polluted waterin ditches, drains, tanks, barrels, tins and an! kind of water accumulation container"

Mos%uito "ionomics

There are more than 1 ::: known mos)uito species" However, of the .8: species that arepotential vectors, onl! 1: are considered dangerous" The three genera Anopheles,

Aedes and #ule$, from three sub-families, are disease relevant"

The epidemiolog! and the life c!cle stages demonstrate the importance of climatic factors andthat water is the essential environmental component for mos)uitoes" The immature stages suchas eggs, larvae and pupae re)uire an a)uatic environment, whereas adult mos)uitoes live interrestrial ecos!stems" The )ualit! and )uantit! of water, whether it is running or standing,shallow or deep, clean or polluted, sweet or brackish, shaded or sunlit, permanent or seasonal,and finall! the climate will determine which particular species can breed" summar! of theph!sical and biological factors is given below (WH5, ./09*"

h!sical factors% In general mos)uitoes prefer higher air humidit! and average watertemperatures between 91 ?# and 11?# in order to complete their a)uatic stages within twoweeks" @ainfall can be a limiting as well as a positive factor" @ain will fill ditches, rivers, ponds,etc", but heav! rain can have a flooding effect and flush out breeding places" +os)uitoes do notnormall! reproduce where excess water is )uickl! removed" 3unlight or shade can also bepositive or negative depending on the species" ll these factors also determine the resting andbiting habits" 3ome species rest and feed indoors and'or outdoors" eak biting activit! is usuall!about one hour before dawn" However, Aedes is a da!time biter, and man! Anopheles bitethroughout the night"

Aiological factors% The presence of vegetation and floating plants are important for optimalbreeding conditions" irst, the plants are larval food and, more importantl!, the! provide shelterfrom predators and protection against wave movement" Therefore, mos)uito larvae are notfound on the open surfaces of large water bodies" The abundance of a number of species islinked to the presence of specific plants"

s a group, mos)uitoes breed in an almost infinite variet! of si$es, t!pes and )ualities of waterbodies and each species re)uires specific environmental breeding and living conditions"

However, most of the mos)uito vectors breed in a rather restricted and narrow range of habitats"It is the number of potential transmitting species and their population d!namics which makescontrol efforts difficult" comprehensive classification b! species, countr! and habitat, includingpotential environmental management measures, is presented in the +anual on Environmental+anagement for +os)uito #ontrol (WH5, ./09*"


6/16

./08*" +os)uito fish can be propagated commerciall! and introduced into drainage water" Thefish are most effective during the warmer months of the !ear"

Water-based diseases transmission by a!uatic and semi-a!uatic snails

Schistosomiasis

There are three ma4or t!pes of schistosomiasis that affect man% S. haemato"ium, S.mansoni and 8" )aponicum. The disease is caused b! female and male trematode wormsinhabiting the blood vessels of the urinar! bladder &S. haemato"ium, S. )aponicum' or the portaland mesenteric veins &S. mansoni'. T!pical visible s!mptoms of schistosomiasis infection areblood in the urine in the case of S. haemato"ium, and intermittent diarrhoea and faecescontaining blood in the case of S. mansoni (ordan and Webbe, ./09*" lthough effectivechemotherap! is available, the costs per treatment and per caput make it too expensive forman! developing countries"

The transmission of all three species is based on a complex four-phase c!cle which includes the

presence of freshwater snails (igure /*" Eggs expelled in the urine or faeces of an infectedperson ma! reach water, where the! hatch rapidl! into miracidia, a free-swimming brief larvalstage" Depending on the species, the miracidia have to find a specific a)uatic or semi-a)uaticfreshwater snail as intermediate host within 9; hours"

S. haemato"ium, S. mansoni and S. )aponicum re)uire snails of the genera *ulinus,*iomphalaria and +ncomelania, respectivel!" +ncomelania are semi-a)uatic snails that live partof the time outside water in moist soil or mud" In the snails, the parasites develop within ; to >weeks into cercariae, a second free-swimming larval stage" It is at this stage that the! areinfectious for man" 3nails shed numerous cercariae into the water" These have to find humanbeings in contact with water in order to penetrate their skin" Having penetrated the skin of thehost, the parasites find their wa! through the veins, heart and lungs to the final organ, there

recommencing the c!cle with egg production (ordan and Webbe, ./09*"

*ionomics of snail intermediate hosts

lthough individual snail species re)uire a specific ph!sical environment, the variet! of a)uatichabitats is almost infinite" +arshes and swamps, permanent or temporar! ponds and pools,natural or man-made freshwater lakes or reservoirs, seasonal or permanent or slow flowing river streams, irrigation or drainage canals, rice fields and all other t!pes of standing, slow flowing orimpounded water are potential snail breeding sites" 7enerall!, the water needs to be shallow,clean or brackish, with little turbidit!" The duration of the life c!cle depends on watertemperatures" The ideal water temperature ranges from - # to 90 ?#"

3nail intermediate hosts of both S. haemato"ium and S. mansoni show great toleranceregarding pH values (8"1-/*, mean water temperatures (.0?-1:?#* and salinit!" 3nails are foundin shaded water bodies but are also known to be active when exposed to direct sunlight" Theshedding of cercariae correlates with da!-time and thus the intensit! of sunlight" urthermore,snails have a remarkable capabilit! to survive long periods (8-0 months* in moist sand or mud(aestivation*" Their main source of food is organic matter originating from deca!ing submergedor emerged vegetation, different species of algae, bacteria and fungi"


7/16

However, both of these a)uatic snail species are sensitive to water velocit! and water tablefluctuations" Tolerable average current speed ranges between :":-:"1 m's (obin and Ippen,./>;& obin et al., ./0;*" In natural rivers, snails are generall! dislodged due to turbulence andfleeting shear stresses along the transition $one between the embankment vegetation and theriver bed sediments, which are their actual habitat $one (ritsch, .//1*"

"I#$%& ' Transmission cycle of schistosomiasis

Water-borne e(creta related infections

+ost of the a)uatic vector or intermediate host habitats correspond to sites where humansaccess water for washing, bathing, swimming (mainl! children* or fishing"

#airncross and eachem (./01* proposed a classification of water-borne diseases in order tomore full! understand the effects of excreta disposal%

i" aecal-oral diseases (non-bacterial*% Infections transmitted from person to person due todomestic contamination and lack of personal h!giene" Examples% hepatitis , giardiasis"

ii" aecal-oral (bacterial*% erson-to-person transmission with longer transmission c!cles eitherthrough contaminated food, crops or water contaminated with faecal material" Examples%2arious diarrhoeas and d!senteries like cholera, /. coli diarrhoea or salmonellosis, entericfevers such as t!phoid"

iii" 3oil transmitted helminths% Eggs of parasitic worms are expelled in faeces and re)uire a

development stage in moist soils" The! reach the human host either b! being ingested onvegetables or b! penetrating the soles of the feet" Transmission takes place in communaldefecation areas or around dirt! latrines without clean concrete floors" Examples% ascariasis,trichuriasis, hookworm"

iv" Aeef and pork tapeworms% Transmission c!cle includes an intermediate development stage inan animal and infection of man occurs when the meat is eaten without sufficient cooking"


8/16

Transmission can be triggered through the application of sewage sludge as fertili$er on gra$ingland" Examples% taeniasis"

v" Water-based helminths% The most t!pical example is that presented above in the section onschistosomiasis" s indicated, eggs in faeces must reach water in order to undergo the nextdevelopment stage in an a)uatic snail" The guinea worm (fasciolopsiasis* follows a similar

c!cle"

vi" Excreta related insect vectors% ilariasis transmitting #ule$ mos)uitoes prefer to breed inhighl! polluted water" Aadl! maintained, unventilated latrines or uncovered septic tanks offer thebest breeding conditions, mainl! in urban areas" However, filariasis ma! also reach man simpl!b! being carried b! flies or cockroaches"

n important characteristic is the persistence of a specific pathogen, i"e", its abilit! to survive inthe environment and whether animals, either in series or parallel, are part of the transmissionc!cle in view of the above classification, water )ualit! and the environmental conditions aroundwater bodies can be seen to pla! an essential role in the transmission"

Thus, unlined open drains, stabili$ation and evaporation ponds or wetlands might becomeparticularl! dangerous transmission sites" It is at such sites that excreta disposal, animal feedingand human water contacts might occur in a concentrated and uncontrolled form, so leading tothe necessar! pathogen-man'animal contacts"

Health ris)s and chemical pollution

Health risks related to water )ualit!, primaril! due to agrochemicals, represent a growingproblem" This is mainl! due to the intensified production and the expansion of irrigatedagriculture, often in association with food processing industries (5, .//1& Hespanhol, .//>*"In this context, both subsurface and open drains can have an impact on human health on four

levels%

i" Drainage water re-use (see #hapter 1*" Ceaching or surface runoff from fields treated withpesticides, e"g", herbicides, fungicides, insecticides or molluscicides (#airncross and eachem,./01*, represents a non-point source of toxic organic substances" If re-used as irrigation water,toxic substances can be ingested b! individuals directl! or indirectl! in the case of drainagewater being mixed with drinking water resources" nother source of direct water contaminationwith agrochemicals is the washing of spra!ing e)uipment in open drains or irrigation canals orthe spra!ing of irrigation canals and reservoirs against a)uatic weeds (Hespanhol, .//>*"Ceaching also includes the transport of inorganic substances like salts, nitrate, phosphorus orheav! metals" 3uch substances can lead to health problems if consumed in high enough doses(5, .//1*" However, salt will be less of a health problem as a salt! taste will prohibit

individuals from drinking too much salt polluted water" Trace elements are more of a concern inthe case of subsurface drainage water"

ii" Drainage water treatment and disposal" s outlined in #hapters 8 and >, both lead to anaccumulation, a transfer or a transition of pollutants" In addition, treatment facilities such asconstructed wetlands or stabili$ation ponds introduce new and permanent open water surfaces,and a)uatic weed growth" Here, the )uestion is whether this will change the human-watercontact patterns and create new vector breeding sites" urthermore, the )ualit! of inade)uatel!treated drainage water might also represent a potential health risk"


9/16

iii" The application of insecticides or molluscicides during chemical vector control campaigns"This can lead to short-term high concentrations of toxic chemicals in irrigation or drainagecanals" Bnprotected workers are exposed to health risks and local populations might consumepolluted water without being aware of the risks" Indirect contamination might occur through theingestion of fish"

iv" Bncontrolled disposal of industrial li)uid waste in drainage canals or treatment and disposals!stems" Due to the lack of environmental regulations and proper treatment plants, especiall! inurban areas, drains often serve as li)uid waste disposal sites for local industries, thusrepresenting dangerous point sources of toxic substances"

lthough health risks arising from chemical pollution are accepted as a ma4or environmentalconcern, data on medical implications are difficult to obtain and often unavailable for developingcountries" Due to the lack of environmental protection and regulation standards as well as thelack of environmental monitoring data, governmental services often neglect the issue ofpollution control"

Integrated control of transmission of vector-borne diseases

#omponents of integrated control approachesEnvironmental management for vector control

Components of integrated control approaches

#ontrol of water related diseases alwa!s re)uires the interruption of transmission c!cles, whichinclude a number of )uite different actors% man, animals, or vectors" These all have differentfunctions, react differentl! to environmental changes and have different capacities in eithertransmitting a disease or in resisting infection" There are basicall! three wa!s to disrupttransmission%

i" b! eliminating or reducing vector densities&

ii" b! protecting the susceptible host through immuni$ation, proph!lactic drugs, reduced man-vector contacts using repellents, window screening, bed nets, or b! installing ade)uate watersupplies and sanitation facilities& and

iii" b! reducing the reservoir of infection, b! treating infected people or animals and b!eliminating the pathogen in the host bod!"

"I#$%& *+ &lements for integrated control of schistosomiasis

http://www.fao.org/docrep/w7224e/w7224e0b.htm#components%20of%20integrated%20control%20approacheshttp://www.fao.org/docrep/w7224e/w7224e0b.htm#environmental%20management%20for%20vector%20controlhttp://www.fao.org/docrep/w7224e/w7224e0b.htm#components%20of%20integrated%20control%20approacheshttp://www.fao.org/docrep/w7224e/w7224e0b.htm#environmental%20management%20for%20vector%20control


10/16

Therefore, an effective and integrated disease and vector control strateg! has to integrate fourbasic elements (adapted and extended after WH5, ./00& Hespanhol .//>*% chemical vectorcontrol, biological vector control, environmental management, and medical treatment" igure .:presents an example of an integrated approach to controlling schistosomiasis"

+edical treatment is still considered as most important" In fact most research and financialresources are focused on medical or bio-medical issues" However, it is clear from the magnitudeof the present health problems, the increasing number and spread of diseases and the closeenvironmental interactions set forth above, that an! intervention can onl! be successful when allfour elements are integrated" This re)uires all parties involved to have a sound understanding of all environmental, social, economic and bio-medical implications of the epidemiologicald!namics of water related disease transmission"

The core of such an approach can be reduced to the formula% transmission and morbidit!control" Transmission control combines chemical, biological and environmental managementcontrol of vectors, intermediate hosts, or an! activit! in the field of water suppl!, sanitationfacilities and water treatment" +orbidit! control includes chemotherap! or an! medical control of the pathogen and the treatment of the disease" 5omen et al. (.//:* visuali$e the environmentalmanagement component as a vehicle having h!giene education and communit! participation aswheels rolling on the road of basic infrastructure"

&nvironmental management for vector control

In ./6/, WH5, 5 and B


11/16

the WH5 Expert #ommittee on 2ector Aiolog! and #ontrol defined three categories ofenvironmental management for vector control as shown in Table 0"

T.& / WH0 definition of environmental management

1efinition &(amples

Environmentalmodification

Cong-lasting or permanent transformation of land, waterand vegetation to prevent, reduce or eliminate vector orintermediate host breeding habitats (water related, vector-borne diseases* or environmental conditions which favourwater-borne and water-washed disease transmission"

7rading, filling, drainage,land levelling, housing,urban drainage"

Environmentalmanipulation

#hanges of environmental conditions tocreate temporary unfavourable breeding conditions forvector breeding or transmission"

Water level fluctuations,water velocit! changes,flushings, weed clearing,salinit! changes"

+odification ormanipulation ofhuman habitation or behaviour

n! environmental manipulation of modification measuresto reduce man-vector and2or man-pathogen contacts3

Aed nets, personalprotection, housescreening, safe bathingand laundr! places,latrines, wastewatertreatment, water suppl!"

#hemical vector control would include the application of repellents, attractants, insecticides,molluscicides and chemosterilants" Aiological vector control can be achieved b! the release ofpredators and microbial insecticides and b! genetic manipulation" inall!, the medicalinterventions would focus on morbidit! control, such as chemotherap!, vaccines, generaltreatment, improved nutrition, preventive health safeguards, proph!laxis and health education"

&nvironmental management measures in drainage water management

Drainage water treatment, re-use and disposal

Environmental management measures applied to drainage structures

In the context of drainage water re-use, treatment and disposal, the potential health risks can beanal!sed within a simplified s!stem of drainage water flow in combination with the transfer ofpathogens, toxic substances and the occurrence of potential vector breeding sites" This allowsone to differentiate whether a health risk is related to water )ualit!, vector breeding or both"

http://www.fao.org/docrep/w7224e/w7224e0b.htm#drainage%20water%20treatment,%20re%20use%20and%20disposalhttp://www.fao.org/docrep/w7224e/w7224e0b.htm#environmental%20management%20measures%20applied%20to%20drainage%20structureshttp://www.fao.org/docrep/w7224e/w7224e0b.htm#drainage%20water%20treatment,%20re%20use%20and%20disposalhttp://www.fao.org/docrep/w7224e/w7224e0b.htm#environmental%20management%20measures%20applied%20to%20drainage%20structures


12/16

or each of the three drainage water management options, a number of )uestions areformulated to identif! potential health risks" These are followed b! a range of recommendationsfor possible control and preventive measures"

1rainage water treatment, re-use and disposal

0irect re1use

t first glance, re-use ma! appear to be a water )ualit! problem mainl! regarding high saltconcentrations which can affect plant growth" However, pesticides in different forms can bewashed into surface drains and trace elements can be leached out b! subsurface drains" Wheredrainage water with high loads of pesticides and trace elements is re-used for irrigation, a healthrisk can occur for irrigation workers or for persons using this water for domestic purposes"

uestions%

i" What is the )ualit! of the drainage waterF Is the drainage water used directl! or blended with

high )ualit! waterF What are the maximum loads of toxic substances after the blendingF rethere seasonal changes in concentration according to agricultural management schedulesF

ii" How do individuals or social groups come into contact with irrigation water blended with re-used drainage waterF Do people use this irrigation water for an! other purposes such asdrinking, washing or cookingF re children in fre)uent contact with the waterF

iii" re there an! other risksF #an polluted water enter other h!drological c!cles with high )ualit!freshwater (e"g", groundwater*, which will then be used for drinkingF

#ontrol and prevention%

In the case of direct re-use, there are few opportunities for the application of environmentalmanagement measures" 5nce drainage water has entered an irrigation s!stem, it is probablethat individuals will come into contact with this water" Therefore, effective monitoring of the)ualit! standards of drainage effluents is most important" It is necessar! to develop safeguardstrategies in case of unacceptable or dangerous contamination levels"

Agriculture1forestry system and solar e2aporators

This s!stem of drainage water management, which aims at a continuous concentration of salt inprogressivel! smaller volumes of water, is less of a health risk, as saline water is unsuitable fordrinking" Here, the )uestion is whether this series of irrigation s!stems will create new openwater surfaces for vector breeding"

uestions%

i" Does the s!stem create new and permanent open water surfaces (e"g", solar evaporator*F

ii" If so, can the! serve as breeding sites for mos)uitoesF Do mos)uitoes alread! breed in thearea and to what extent are mos)uito transmitted diseases prevalentF re there mos)uito


13/16

species involved which can breed in brackish water (e"g", some Aedes,#ule$ and Anopheles species*F #an water snails tolerate the salt concentrationsF

iii" #an a)uatic weeds growF

iv" How near are settlements, roads or larger urban centresF What diseases are prevalentthereF


i" Intermittent dr!ing out of ponds or storage tanks for at least 8-6 da!s"

ii" If possible, lining of all facilities to avoid seepage and minimi$e a)uatic growth" In the case ofearth lining% regular weed control" 5nl! restricted or no applications of insecticides ormolluscicides"

iii" @estricted accessibilit! in order to reduce man-water contacts"

iv" 3ettlement planning% geographical separation of settlements from ponds and tanks"

v" +onitoring of vector breeding activities and water )ualit!"

vi" Evaluation of options"

#onstructed wetlands

The various ph!sical, chemical and biological treatment processes ma! re)uire a number ofwater retention structures such as constructed wetlands" This could lead to new and mostl!permanent open water surfaces" Here again, the )uestion is whether vector breeding sites will

be created, or whether the purification capacit! will determine the effluent )ualit! and thus thewater )ualit! for low-end consumers"

uestions%

i" How man! new and permanent water bodies will be createdF How large is the areaF

ii" What kind of vegetation (e"g", a)uatic weed* will growF

iii" Is the local population alread! exposed to water related diseasesF Where are thetransmission foci locatedF What vector or intermediate host species are involvedF

iv" Do their breeding re)uirements correspond to the environmental conditions created b! aconstructed wetland (e"g", for mos)uitoes*F

v" How near are settlements, urban centres and roadsF re there an! migration movements inthe areasF

vi" What is the )ualit! and performance of the local health serviceF What is the perception of thepopulation regarding environmental health issuesF


14/16

vii" re there an! data on prevalence, incidence, vector population d!namics or breedinghabitatsF


i" Water level fluctuations and intermittent dr!ing out of the wetland area"

ii" @estricted accessibilit!"

iii" 7eographical location outside and separated from human settlements"

iv" 5ff site% settlement planning and maintenance, housing improvement, personal protection"

v" Health education"

vi" +onitoring% vector populations, water )ualit!, case reporting"

vii" In the case of high communit! vulnerabilit! and environmental receptivit!% evaluation ofoptions"

&nvironmental management measures applied to drainage structures

Drainage s!stems need to be connected either with subsurface or surface drainage canaloutlets" In the case of surface collector canals, additional open water surfaces will beintroduced" In warm and hot climatic $ones, drainage canals include a number of t!picalfeatures which favour vector breeding, disease transmission and direct pathogen propagation,such as low and irregular flow velocities, low embankment slopes, high seepage, uncontrolledwater access, uncontrolled deposition of excreta and a)uatic weed growth"

/n2ironmental modification

+odifications to the drainage s!stem environment would include% the change from open to pipedor covered drains& canal lining with concrete in order to increase flow velocities and reducea)uatic weed growth& installation of special structures for cattle crossings and drinking& and boatramps to protect earth embankments"

/n2ironmental manipulation

The ke! elements of environmental manipulation would be flow and water level managementmeasures" eriodical flushing will help to dislodge snails and mos)uito larvae if drag forces or

shear stresses due to higher velocities exceed certain limits (obin, ./06& 5omen et al., .//:&ritsch, .//1*" Water level fluctuations can have distinct control impacts on both snail andmos)uito breeding" If the drop is fast enough, snails, larvae and eggs become stranded and die(ritsch, .//1*" Intermittent flow, dr!ing out of canals in connection with flushing, and watertable fluctuations can also be effective tools to control mos)uito or snail breeding" However, theapproach differs for snails and mos)uitoes, according to the locall! specific population d!namicand vector bionomics (5omen et al., .//:*" inall!, canal maintenance means weed control andthe removal of sediments" Weed control can be done either mechanicall!, chemicall! b!appl!ing herbicides, or biologicall! with fish"


15/16

Modification and manipulation of human ha"itation or "eha2iour

Interventions and environmental changes related to human habitation might not be sufficient ifcanals are continuousl! misused for excreta and waste disposal" In this case, health risks haveto be minimi$ed with a set of non-drainage related measures" This includes the improvement ofsanitation facilities and personal h!giene (e"g", water suppl! s!stems or latrines* and the

planning and maintenance of settlements"

1evelopment of control strategies

There are no standard packages of engineering techni)ues available, nor should environmentalmanagement be considered as the ultimate solution for controlling water related parasiticdiseases (ritsch, .//1*"

Airle! (.//8* has introduced a s!stematic approach to forecast vector-borne diseaseimplications" In this assessment methodolog! he addresses three main components whichcontribute to the potential health ha$ards%

#ommunity 2ulnera"ility3 This describes the prevalence of specific diseases in social groupssuch as children, adults, males, females, workers or farmers" The prevalence is brought intorelation with the proximit! of disease foci, the immune status, previous histor! of exposure,general health status and the role of migrants" 2ulnerabilit! is ranked as high, moderate or low"

/n2ironmental recepti2ity3 This is the receptivit! to transmission of the pathogen related to theabundance of the vector, to human contacts with water or vectors and to an! other ecological orclimatic factors favourable for transmission" The assessment is followed according to possibletransmission but not to occurrence, transmission easil! resumed, or to high receptivit!"

4igilance of the health ser2ices3 This describes the )ualit! and performance re)uired of a health

service to cope with an increased health ha$ard" The )uestion is whether a health service isable to support and manage vaccination campaigns, continuous case detection, drug provisionand deliver!, hospitals, sufficient and skilled staff, health education and information or means for chemical or biological vector control" The ranking includes% ver! good, effective preventivemeasures onl!, effective treatment onl!, and none"

The assessment of control strateg! effectiveness is organi$ed in a se)uence of flow charts andworksheets" It includes a comprehensive set of )uestions which finall! lead to the ranking of thethree components" The methodological approach forces one to focus on control elements andwill structure data and help to set up additional surve! or monitoring concepts if there is a lack of data" It will also help in assessing the )ualit! and reliabilit! of data" 5verall the final outcome(the total assessment of potential health ha$ards* will provide a sound basis for identif!ing the

re)uired set of safeguards and preventive intervention measures, including the environmentalengineering re)uired to control water management related diseases"


16/16

Chapter 7 Health Issues Related to Drainage Management

Documents

Transcript of Chapter 7 Health Issues Related to Drainage Management