Cholera track may spark cure

Saturday Star - - NEWS - SHAUN SMILLIE

IN THE lab­o­ra­to­ries of the Na­tional In­sti­tute of Com­mu­ni­ca­ble dis­eases (NICD) a killer stored for decades in sub-zero tem­per­a­tures has fi­nally given up the se­crets of its death trail.

That killer is Vib­rio cholera 01, the causi­tive or­gan­ism of cholera, which claims tens of thou­sands of lives each year.

Each sam­ple held in the lab­o­ra­tory was col­lected when cholera epi­demics swept through the coun­try.

These sam­ples and thou­sands of oth­ers col­lected across the globe have al­lowed sci­en­tists to track the ge­netic trail of the dis­ease as it spread across the globe.

This study, which was re­leased on Thurs­day, an­a­lysed ge­nomic data from 1 070 Vib­rio cholerae pop­u­la­tions from 45 African coun­tries, over a pe­riod of 49 years.

What the sci­en­tists were track­ing is the sev­enth pan­demic of cholera that be­gan in 1961, and moved through Asia, Africa, the Caribbean and Latin Amer­ica and caused the deaths of be­tween about 21 000 to 143 000 deaths per year.

The sev­enth pan­demic was driven by a strain of Vib­rio cholerae called 7PET.

Pre­vi­ous stud­ies, say sci­en­tists, have been un­able to pro­vide such a de­tailed pic­ture of the pathogen as it jour­neyed across con­ti­nents.

“Our re­sults show that mul­ti­ple new ver­sions of 7PET bac­te­ria have en­tered Africa since the 1970s.

“Once in­tro­duced, cholera out­breaks fol­low sim­i­lar paths when spread­ing across that con­ti­nent.

“The re­sults give us a sense of where we can tar­get spe­cific re­gions of Africa for im­proved sur­veil­lance and con­trol,” says Dr François-Xavier Weill, first au­thor on the African study and prin­ci­pal in­ves­ti­ga­tor from the In­sti­tut Pas­teur.

The largest epi­demic in his­tory is con­tin­u­ing in Ye­men where the num­ber of cases is close to a mil­lion.

Dr Karen Keddy of the NICD, con­trib­uted to the lo­cal arm of the in­ter­na­tional study.

“In Asia, your en­demic case num­bers are larger, whereas in Africa it re­ally does come in waves, cholera then dis­ap­pears for a few years then an­other big out­break, oc­curs then it dis­ap­pears,” she says.

Ear­lier re­search of the 7PET strains even pin­pointed the ge­o­log­i­cal lo­ca­tion where the dis­ease left from when it dis­em­barked for Africa from Asia.

This point is the Bay of Ben­gal, and sci­en­tists aren’t too sure why this is so.

Air­line travel has also en­abled the faster trans­mis­sion of cholera around the globe.

South Africa hasn’t had any se­ri­ous cholera out­breaks re­cently Keddy said, and this is thanks to good vig­i­lance and a health-care sys­tem that has re­sponded quickly when the dis­ease strikes.

It is also a dis­ease where pa­tients re­cover re­mark­ably quickly.

“This is such an easy dis­ease to man­age if you are just pre­pared for it,” says Keddy.

“Be­cause you save lives through re­hy­dra­tion, you don’t need costly an­tibi­otics be­cause even­tu­ally the pa­tient de­vel­ops im­mu­nity.”

South Africa’s largest cholera out­break in re­cent years hap­pened in 2001 when there were more than 100 000 cases, ac­cord­ing to Dr Juno Thomas, of the NICD, who was not part of the study.

Most of South Africa’s cur­rent cases of cholerae are caused by pa­tients bring­ing the dis­ease across the bor­der un­in­ten­tion­ally.

The ma­jor­ity come from Zim­babwe, and some­times a pa­tient will ar­rive from In­dia with symp­toms.

In 2008/2009 there was a cholera out­break in Zim­babwe that spilled over mainly into Lim­popo.

Doc­tors with­out bor­ders per­son­nel work­ing in Musina, iden­ti­fied the first case and raised the alarm.

But by hav­ing a bet­ter un­der­stand­ing of how the dis­ease spreads, Keddy be­lieves health pro­fes­sion­als will be given an edge in fight­ing the pathogen.

“If we can trace where cholera gets in­tro­duced, and how it gets in­tro­duced, if we can de­fine how it gets into the en­vi­ron­ment and stays in that en­vi­ron­ment, then it will be so much eas­ier to come up with cam­paigns.”

How­ever more work needs to be done.

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