Plague as a weapon
Apr 13,2007 00:00 by Bend_Weekly_News_Sources

Sci­en­tists are wor­ried that a dis­ease as­so­ci­at­ed with dev­as­tat­ing me­di­e­val epi­demics may make a come­back as a weap­on.

An ar­ti­cle in this week’s is­sue of the med­i­cal jour­nal The Lan­cet dis­cusses the pos­si­bil­i­ty that the bac­te­ri­um re­spon­si­ble for plague—known in the Mid­dle Ages as the Black Death—could serve as a bioter­ror­ism agent. 

Infections from the mi­crobe, Yer­si­nia pes­tis, take sev­er­al forms.

In the ar­ti­cle, Mike Pren­tice of Uni­ver­si­ty Col­lege in Cork, Ire­land and Li­la Ra­hal­i­son of the Pas­teur In­sti­tute in An­ta­na­na­ri, Mad­a­gas­car, re­viewed the bac­te­ri­um’s ge­net­ic make­up, his­to­ry and modes of trans­mis­sion.

Shoot­ing dead­ly ar­rows, a shad­owy fig­ure of death seals the fates of plague vic­tims in this anon­y­mous 15th-century paint­ing, Al­le­go­ry of the Plague.

The mi­crobe mul­ti­plies in fleas that have fed on in­fected an­i­mals’ blood. This causes a block­age in the flea’s feed­ing sys­tem that makes the flea con­tin­u­al­ly re­gur­gi­tate and feed again, de­liv­er­ing the germ in­to the blood of what­ev­er it is bit­ing—of­ten a ro­dent or a hu­man.

Bu­bon­ic plague, the most com­mon form, has a sud­den on­set and causes diz­zi­ness, high fe­ver, pain­ful swellings and hemmhor­ages. These some­times turn black, ac­count­ing for the name Black Death. The most wide­spread ep­i­dem­ic is es­ti­mat­ed to have killed three quar­ters of the pop­u­la­tion of Eu­rope and Asia af­ter start­ing in Con­stan­ti­no­ple in 1334.

An­oth­er form of in­fec­tion, pneu­mon­ic plague, is quick­ly fa­tal and is the on­ly type di­rect­ly trans­mis­si­ble from per­son to per­son, by air droplets re­leased dur­ing cough­ing or sneez­ing.

Plague’s abil­i­ty to spread via droplets makes pos­si­ble aerosol-based weap­ons ca­pa­ble of caus­ing wide­spread pneu­mon­ic plague out­break, ac­cord­ing to Pren­tice and Ra­hal­i­son. Ex­ac­er­abat­ing the dan­ger, they added, is the bac­te­ri­um’s wide dis­tri­bu­tion, ease of cul­tur­ing, and availa­bil­i­ty of ex­pert ad­vice from form­er weap­ons sci­en­tists.

The dis­ease still pre­vails in parts of Asia and spo­rad­i­cal­ly oc­curs else­where; an es­ti­mat­ed 2,500 cases are re­ported an­nu­al­ly.

Un­treat­ed bu­bon­ic plague kills 50 to 90 per­cent of vic­tims, the re­search­ers said, though time­ly di­ag­no­sis and ther­a­py cut those per­centages to be­tween five and 15. An­tibi­otics are ef­fec­tive, but a Y. pestis strain in Mad­a­gas­car shows dis­turb­ing signs of hav­ing evolved re­sist­ance to some of these, they added. Some vac­cines are in de­vel­op­ment, one of which has reached phase II tri­als, the mid­dle stage in the clin­i­cal tri­als pro­cess.

Plague con­trol efforts in­volve mon­i­tor­ing and re­duc­ing ro­dent pop­u­la­tions where plague per­sists, the re­search­ers wrote. But “re­moval of the fleas’ nor­mal food sup­ply by poi­son­ing their usu­al hosts can in­crease hu­man con­tact with starv­ing fleas,” they added. Thus, “flea con­trol by ap­pli­ca­tion of in­sec­ti­cides in plague out­break ar­eas is al­so im­por­tan­t.”

Courtesy The Lancet and World Science staff