Mos­quito gut bac­te­ria may of­fer clues to malaria con­trol

Porterville Recorder - - HEALTH / SCIENCE - By LAURAN NEERGAARD

WASH­ING­TON — Mos­qui­toes har­bor gut bac­te­ria just like peo­ple do — and the bugs in­side the bugs may hold a key to fight­ing malaria.

To­day, bed nets and in­sec­ti­cides are the chief means of pre­vent­ing malaria, which sick­ens about 200 mil­lion peo­ple around the world and kills 400,000 a year, mostly chil­dren in Africa. But what if sci­en­tists in­stead could hatch malaria-re­sis­tant mos­qui­toes?

Johns Hop­kins Univer­sity re­searchers re­ported Thurs­day that ben­e­fi­cial bac­te­ria liv­ing in­side a mos­quito’s gut can help do just that — two some­what ac­ci­den­tal dis­cov­er­ies that, if they pan out, might one day of­fer a novel way to pro­tect against malaria.

“If you get it to work, these mos­qui­toes would re­main re­sis­tant,” said Ge­orge Di­mopou­los, a mi­cro­bi­ol­ogy pro­fes­sor at Hop­kins Bloomberg School of Pub­lic Health who helped lead the re­search. In­stead of hav­ing to kill swarms of mos­qui­toes, “you would ba­si­cally con­vert a malaria-trans­mit­ting mos­quito pop­u­la­tion to one that can­not trans­mit.”

Malaria is spread by fe­male Anophe­les mos­qui­toes that bite an in­fected per­son and then, af­ter the dis­ease­caus­ing par­a­sites in­cu­bate in­side the in­sect’s gut, pass on the in­fec­tion by bit­ing some­one else.

Peo­ple, an­i­mals, even in­sects har­bor a com­mu­nity of mostly healthy in­testi­nal bac­te­ria, what’s called the gut mi­cro­biome. Re­searchers have long known that some of those nat­u­ral mos­quito germs are ca­pa­ble of at­tack­ing malaria par­a­sites. The hur­dle: How to spread that pro­tec­tion to enough mos­qui­toes in the wild to make a dif­fer­ence.

One Hop­kins team dis­cov­ered an odd­ball strain of bac­te­ria that mos­qui­toes can eas­ily pass to one an­other. Called Ser­ra­tia AS1, it lives in both the gut and ovaries of mos­qui­toes. Un­like other mos­quito germs, males trans­mit this strain to fe­males dur­ing mat­ing, and fe­males can in­fect their off­spring.

Ge­net­i­cally al­ter­ing that bac­te­ria to emit some anti-malaria com­pounds sup­pressed par­a­site growth with­out hurt­ing the mos­qui­toes. Re­searchers fed the revved-up germs to a small num­ber of mos­qui­toes and let them mate with nor­mal mos­qui­toes in the lab. Sure enough, the en­tire next gen­er­a­tion har­bored the malaria sup­press­ing germ, Hop­kins malaria re­searcher Marcelo Ja­cobs-lorena re­ported in the jour­nal Science.

In a sec­ond set of ex­per­i­ments, Di­mopou­los’ team made an even more cu­ri­ous dis­cov­ery. They al­tered a mos­quito im­mu­nity gene to make it more ac­tive and help the in­sects bet­ter fend off malaria in the first place.

Some­how, that sub­tle ge­netic change also al­tered the in­sects’ usual gut bac­te­ria and made them more at­trac­tive to mates. Mod­i­fied male mos­qui­toes be­gan seek­ing out un­mod­i­fied fe­males, and un­mod­i­fied males sought out mod­i­fied fe­males, Di­mopou­los said.

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