Ways to counter the on­slaught of vec­tor-borne dis­eases

In­dia does not have to bear the on­slaught of vec­tor-borne dis­eases year af­ter year. It is pos­si­ble to con­trol mos­qui­toes that spread these dis­eases. Here's how

Down to Earth - - FRONT PAGE - VIBHA VARSHNEY and KUN­DAN PANDEY from Delhi; ANAND VATTAMANNIL from Ker­ala; MANUPRIYA from Kar­nataka

SCI­EN­TISTS SAY a month of con­cen­trated ef­forts is all it takes to con­trol mos­qui­toes re­spon­si­ble for dis­eases like dengue and chikun­gunya. But the claim sounds far­fetched at a time when al­most the en­tire coun­try has been re­port­ing these dis­eases for the past eight months (see ‘Vec­tor war in­ten­si­fies’ on p24).

The coun­try reg­is­tered 36,110 con­firmed cases of dengue and 14,656 cases of chikun-gunya till Septem­ber 11. Govern­ment data shows dengue has also claimed 70 lives. An alarm­ing num­ber of cases have been re­ported of an­other type of fever whose symp­toms are sim­i­lar to chikun­gunya and dengue. It is being dubbed mys­tery fever. Un­able to un­der­stand what causes the fever, govern­ment agen­cies have started screen­ing for Zika, an­other vec­tor-borne dis­ease, as a pre­cau­tion. The Na­tional In­sti­tute of Virol­ogy, Pune, has al­ready checked over 300 blood sam­ples for Zika virus, but the sam­ples have tested neg­a­tive, con­firms D T Mourya, di­rec­tor of the in­sti­tute.

Ask B N Nag­pal, sci­en­tist at the Na­tional In­sti­tute of Malaria Re­search, Delhi, why the coun­try has failed to avert such an out­break of vec­tor-borne dis­eases and he says it is be­cause of lack

of po­lit­i­cal will. “Even if ex­ist­ing meth­ods are em­ployed prop­erly, it is pos­si­ble to con­trol the pop­u­la­tion of mos­qui­toes,” says Nag­pal. His sen­ti­ments were echoed by the Na­tional Green Tri­bunal, which on Septem­ber 21, rep­ri­manded the Delhi govern­ment for its “shame­ful and shock­ing” re­sponse to the out­break. The cap­i­tal has so far reg­is­tered four dengue deaths.

Shift­ing places

A fall­out of this po­lit­i­cal ap­a­thy has been the fail­ure of the govern­ment to adapt to the chang­ing na­ture of Aedes ae­gypti mos­quito, which is re­spon­si­ble for the dis­eases plagu­ing the coun­try.

Nor­mally, the mos­quito would breed only in clean stag­nant wa­ter ac­cu­mu­lated in pot­holes, dis­carded con­tain­ers and tyres. Not only has in­ter­mit­tent rains as­so­ci­ated with cli­mate change in­creased breed­ing places for the mos­quito, the vec­tor is also adapt­ing to newer en­vi­ron­ments. Now there is ev­i­dence that it can grow in dirty wa­ter, us­ing it as a habi­tat through­out the year. A study pub­lished in the In­dian Jour­nal of Med­i­cal Re­search in 2015 shows that Aedes mos­qui­toes that breed in dirty wa­ter are big­ger and have longer wing spans. The Na­tional Vec­tor Borne Dis­ease Con­trol Programme’s 2016 Ur­ban Vec­tor­Borne Dis­ease Scheme does not con­sider dirty wa­ter as a breed­ing area. The au­thors of the 2015 study sug­gest that the coun­try’s vec­tor con­trol programme should in­clude sewage drains as breed­ing habi­tats of dengue vec­tor mos­qui­toes.

The scheme in­cludes meth­ods such as con­trol­ling mos­quito breed­ing sites, use of anti-lar­val meth­ods with ap­proved lar­vi­cides and bi­o­log­i­cal con­trol through lar­viv­o­rous fishes and bi­o­lar­vi­cides. And even these are not being em­ployed prop­erly, which is clear from the cur­rent out­break.

High on re­search, low on prac­tice

Many in­no­va­tive meth­ods have been de­vel­oped in the past few years to fight mos­qui­toes, but they are still in ex­per­i­men­tal stages (see ‘Pull the weapons’, p24). One way is the use of crowd-sourced data to pre­dict the dis­ease out­breaks in ad­vance. Sci­en­tists at Nanyang Tech­no­log­i­cal Univer­sity ( ntu), Na­tional Univer­sity of Sin­ga­pore ( nus), and the In­dian In­sti­tute of Tech­nol­ogy Bom­bay, Mum­bai( iitb), col­lab­o­rated to cre­ate a we­band mo­bile-based ap­pli­ca­tion for dengue sur­veil­lance. The Mo-Buzz ap­pli­ca­tion com­bines three el­e­ments of dengue man­age­ment—pre­dic­tive sur­veil­lance, civic en­gage­ment and health com­mu­ni­ca­tion. It was first used in Colombo in 2013 through a group of Sri Lanka’s pub­lic health in­spec­tors. The in­spec­tors mon­i­tored dif­fer­ent ar­eas in the city and fed their re­ports in the sys­tem, which used a pre-loaded al­go­rithm to gen­er­ate hotspots of in­fec­tion in real time. “The pre­dic­tions in­formed pub­lic health in­spec­tors about the ar­eas that needed im­me­di­ate in­ter­ven­tions,” says May O Lwin, pro­fes­sor at ntu and the prin­ci­pal in­ves­ti­ga­tor at Mo-Buzz. The ap­pli­ca­tion also al­lows cit­i­zens to “re­port dengue-breed­ing sites through geo-tagged pic­ture re­ports”. The ap­pli­ca­tion has not been tried in In­dia so far be­cause of fund­ing is­sues, says Ravi Poova­iah of iitb, who was part of the team that de­vel­oped the app.

In fact, the lone ex­per­i­ment in In­dia to use crowd sourced data for sen­si­tis­ing peo­ple about dengue has been tried by a Mum­bai-based agency called Va­mane­tra Digi­health. The com­pany, set up in April 2014, started an app in Mum­bai to de­tect dengue-breed­ing spots in the city. “The re­sponse from the pub­lic was luke­warm pri­mar­ily be­cause of lim­ited mar­ket­ing of the prod­uct and the un­der­ly­ing cam­paign,” says Rintu R Pat­naik, manag­ing part­ner, Va­mane­tra Digi­health. He adds that the ve­rac­ity of data is a big is­sue on crowd-sourc­ing plat­forms. “The chal­lenge we faced in run­ning the trial was sim­i­lar to what the pub­lic health teams reg­u­larly face—peo­ple are gen­er­ally un­will­ing to volunteer or al­low health work­ers to find trou­ble spots that can al­low mos­quito breed­ing.” Though the com­pany has stopped de­vel­op­ing apps that re­quire crowd sourc­ing of data, they are still work­ing on mod­ules that rely on govern­ment data and open data sets. Pat­naik says the be­hav­iour of peo­ple can change for the bet­ter “through greater me­dia cov­er­age and aware­ness”.

Re­searchers across the globe are also ac­tively de­vel­op­ing ge­net­i­cally mod­i­fied (GM) mos­qui­toes to con­trol vec­tor pop­u­la­tion. GM mos­qui­toes are cre­ated by in­ject­ing the eggs with mod­i­fied dna. The male prog­eny is re­leased to mate with nor­mal mos­qui­toes and their prog­eny has a short life­span. Ox­itec, a Bri­tish com­pany, has tested GM mos­qui­toes in Piraci­caba, Brazil, and found that it re­sulted in an 82 per cent de­cline of the mos­quito pop­u­la­tion in the area in just eight months. In Au­gust this year, the com­pany got a go-ahead from the US Food and Drug Ad­min­is­tra­tion to re­lease the GM mos­qui­toes as part of an

Vec­tor-borne dis­eases can be con­trolled through sus­tained ef­forts. A clas­sic ex­am­ple is how Sri Lanka has man­aged to erad­i­cate malaria by shift­ing to an in­te­grated vec­tor-con­trol programme. They also car­ried out strong sur­veil­lance to en­sure that pa­tients were iso­lated and treated in the ini­tial stages

in­ves­ti­ga­tional field trial in Key Haven in Florida Keys. Res­i­dents of Key Haven will soon vote on the trial and the fi­nal ap­proval will be given by the Florida Keys Mos­quito Con­trol Board. “In In­dia, we have rec­om­mended con­trolled field tri­als of GM mos­qui­toes,” says K Gu­nasekaran, sci­en­tist at the Vec­tor Con­trol Re­search Cen­tre in Puducherry. He says the Depart­ment of Science and Tech­nol­ogy is in the process of pre­par­ing guide­lines for con­duct­ing tri­als in In­dia.

The use of GM mos­quito, how­ever, is con­tro­ver­sial as they have been im­pli­cated in the spread of the Zika virus. Zika virus in­fec­tion be­gan in those ar­eas of Brazil where Ox­itec had first re­leased the mod­i­fied mos­qui­toes. Even ac­tivists in Florida Keys are against the use of these mos­qui­toes.

Use of Wol­bachia bac­terium has shown po­ten­tial in con­trol­ling the vec­tor. The bac­terium re­duces the growth of the dis­ease­caus­ing virus such as dengue, chikun­gunya and Zika in the body of Aedes ae­gypti. Both Wol­bachia- in­fected male and fe­male mos­qui­toes are re­leased into the environment. When they mate with nor­mal mos­qui­toes, they trans­fer the bac­terium to the prog­eny. Wol­bachia is self-sus­tain­ing. “This makes the method cost ef­fec­tive,” says Lewti Hung­han­foo, com­mu­ni­ca­tions ad­viser for Elim­i­nate Dengue, in­ter­na­tional col­lab­o­ra­tion led by Monash Univer­sity, Aus­tralia.

Some ex­per­i­ments have also shown that when Wol­bachia- in­fected male mos­qui­toes mate with nor­mal fe­male mos­qui­toes, they are un­able to re­pro­duce. Sin­ga­pore plans to in­tro­duce male Aedes mos­qui­toes car­ry­ing Wol­bachia bac­te­ria in three hous­ing es­tates in Oc­to­ber this year. The field trial will con­tinue for six months to as­sess the im­pact on the mos­quito pop­u­la­tion. In­dia too plans to use Wol­bachia in the next two years.

Pre­lim­i­nary re­search shows that par­a­sitic fun­gus Me­tarhiz­ium brun­neum has the po­ten­tial to con­trol the pop­u­la­tion of the Aedes mos­quito. A study pub­lished on July 7, 2016, in PLoS Pathogens demon­strates that the fun­gus can at­tack Aedes lar­vae in a rapid and ef­fec­tive way. Re­searchers of the study say the ap­proach is safe for hu­mans. The big­gest ad­van­tage of the fun­gus is that it grows in fresh­wa­ter, which is the nat­u­ral habi­tat of Aedes mos­quito.

There is an In­dian in­ven­tion to com­bat mos­qui­toes as well. Hawker is an in­dige­nous mos­quito and fly trap­per de­vel­oped by Ker­ala res­i­dent Mathews K Mathew. The de­vice uses bio­gas to lure mos­qui­toes and sun­light to kill them. It makes use of the smell from the sep­tic tank to at­tract the mos­qui­toes. Once the mos­qui­toes get trapped, the heat built up inside the de­vice kills them. Mathew says a sin­gle Hawker can con­trol mos­quito pop­u­la­tion in 0.4 hectare of land and its sur­round­ings. He ini­tially used Hawker in churches and old age homes and has got a patent for the prod­uct. He now plans to start mass-pro­duc­ing the de­vice, which cur­rently sells for ` 1,500.

He is in talks with of­fi­cials of the Kochi Mu­nic­i­pal Corporation ( kmc) be­cause the city has over 260,000 sep­tic tanks. A se­nior kmc of­fi­cial says, “The de­vice is the most ef­fec­tive fly rem­edy we have seen so far. It does not pro­duce chem­i­cals or other toxic waste and has a larger op­er­a­tional area with lit­tle main­te­nance cost. We have al­ready pro­posed to use Hawker widely.”

Experts say the key lies in us­ing a com­bined ef­fort, which should have both na­tional poli­cies and lo­cal in­no­va­tions. “All the in­no­va­tive meth­ods have po­ten­tial, but it is un­likely that any of them when used alone, will be ef­fec­tive in dis­ease pre­ven­tion and con­trol. None has been fully val­i­dated so it is too early to tell which will be most ef­fec­tive,” says Duane J Gubler, pro­fes­sor emer­i­tus and found­ing di­rec­tor of Sig­na­ture Re­search Pro­gram in Emerg­ing In­fec­tious Dis­ease, Duke- nus Med­i­cal School, Sin­ga­pore.

The vec­tor Aedes ae­gypti has spread across the globe and In­dia is in­fested with it. It is time we used the one-month op­por­tu­nity to con­trol the pop­u­la­tion. We have both es­tab­lished and ex­per­i­men­tal tools. “These are not dif­fi­cult to im­ple­ment. What is dif­fi­cult is to have sus­tain­able com­mit­ment by the govern­ment and the peo­ple,” says Gubler.


Lal Ba­hadur Shashtri Hospi­tal in New Delhi. The cap­i­tal reg­is­tered four dengue deaths till Septem­ber this year

Colombo mayor A J M Muza­m­mil (sec­ond from right) launches the Mo-Buzz ap­pli­ca­tion for map­ping dengue hotspots at the Colombo Mu­nic­i­pal Coun­cil on Fe­bru­ary 12, 2015. Hawker (left) is a de­vice ef­fec­tive in con­trol­ling mos­quito pop­u­la­tion in sep­tic tanks


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