l-->SYCI-IT~ .

lllOSQUITOES CO~SIDEREL> AS TR.\~S:\1 ITTERS OF YELLOW FEYER Al\' D liL\L:\RL\.

13Y CHARLES J. FINLAY, ill.D., HAVANA.

(from the~ \". l\Iedica.l Record of ~Lly ::!.], 1899 .)

THE despised mosquito, denounced by me ;.incc ISS I :1s the :~gent of trans­missirm of yellow feYer. is now attract­ing- consider:1hle attention :1n•ong di'­tingui!>hed and s:~gacious obsen·ers who attribute to that in!>ect :111 important r(lle in tl

11e etiology and propag·ation of the

m:daria infection. To those who are familiar with the biologic:II conditions and the h:1hits of the mosquito, this" ill n"t l•e a matter for !>Urprise; r:1ther should \Ye wonder how, cnn~idcring the specia 1 aptitudes of the insect, other in­oculalde di~e:1ses are not equally trans­mitted hy it. e~peci:dly such :~s :ne due to germs in the blood ur in the tis~ues that lie \Yithin reach of ih sting . .:\luch light, however. has been thrown upon this singular eclecticism by modern ide:~s concerning the process by which some b lood-sucking insects com·ey cer­tai n diseases.to warm-ldoocled animals. \Ve are induced by them to 1·egard as one of the essential conditions th:1t the tr:1 nsmitting insect should itse lf expen­ence a true infection, which may not endanger its life nor greatly disturb its p hysiological funct ions. but must always

require. on the p:1rt ofthe insect. patho­genons susceptibility for the specific g-l-rms which it i,; called upon to trans­mit. lt will thus be readily nnder~tood why the s:1me insect 111:1y tr:1nsmit only CCI t:1in germs :111cl not others, as also tlwt, :mwng- i11sects of the same kind, some species m:1y possess that faculty while others do not.

Among the public:1tions that have :ljlJll':lrcd concerning the transmission of mal:~ri:~ hy mosquitoes, the most im­portant onL·, :1nd th:1t which h:1s c:msed mo~t sensation, ha.-; heen the lecture de­livered, a fL'\\' months :1go, by Robert Koch, in which he clecl:!rcs himself lkcidedly in favor of the mosquito theory as the one which most phusibly accounts for the propag:1tion ofthc said disL·asc. In support of his idea he cites a \'cry appropriate precedent. the Tex:1s fC\'er, a c:1ttlc disease, the etiology and propagation of \Yhich v\·erc so ahly cle:.red up in 1 S9z by Dr. Thenhald Smith, chief of the diYision of animal p:tthology in the Bureau of Animal In­dustry, United !States o~· America. Dr. ~mitl-1 proved that the germ of the

. nl \ r '-, l P.STCI!E

blood). Thi~ tnstal1t:e, at any tate . shows that h:.och's assertiou. that

"wlJL•re there are no mosquitoe" tlll.:re is no m:.Iaria,'' is altogether too ahsn­

lnte. In those camps, I believe the

pmp:tgation must han: been cllected

through the !lies (of which there was a g-reat ahundance). The~e insects, in

spite of :til prec;111tions, !tad :llltple

opportunities of pickin;; np, from tlte clisch:trges of the mal:tria p:ttients, not

only the m:tlaria p:tr:t,ite., containL·d in the extral·:ts.<tcd hltJod, hut :tlso some

infL·ctious inll:,tinal germ, with hoth of

which organis<lh the,· m:ty lLt\'t con­t:nninated the food .tnd beverage' u,cd

h\· thL· lllvn wit" sui"L'l]IIL'IItly showed

,ign> of the cl"nlde illf,·cti"tl. .\ \ el­lnll'-fe,L·r epidunic occuning uttder "im­

ilar circumsl:tttces, in the absence of

.\ elln\1'-k\·er lll<l"t]llitc>es, mi~ht ll•>t he so readily rL·cnncikd with Ill\' tlte.,ry

:tl>Out that di't':tse, \\ ltich is foutJclnl

upon more defittite aud more cxclu"i,·e

arguments than those recorded in con­nection with the mal:tria infectiou.

The follo"·ing in~tance may "cn·e to illthtrate my meaning In the c.tpital of i\l.:xic\l, and in other tJi,tricts of

similar :tltitttde ahol'e the ,ea iel'el,

.illexic:ttl" who never ltal'e ,.i,ited the

l"wlaud, h:tve no imntunitl wltat,oever

against l'ellnw fever, a sure proof that

nn epidemic., of that di~ease ever occ:ut

in that p:trt of tile countn·. It some­time., h.tpp::n, hnwcl'er. that a re,ident

of the c:tpital t:1kes' the infecti•>n IJ_y .!.!O<D!,! to \'cr;~ Cn1z, thottgh the dis­ea'e may not d~dare ibelf nntil hi, return to the e:tpital. 1n ~11ch c:t~es.

the yellow fever will run its usua l cnurse, with the same symptoms and

progno~i,. as if tlie patient had remained at \'era C1uz; with this ditrerence only:

that in \'era Cruz nth~r susceptible

persons might readily ha\'c caught the

infL·ctiun from him, whereas in .'lie:--ico

lite dihe:tse is nn·er prop:tg<lted. If the infediotJ could he trall:,lltilted through U>lll:il't with the patient or hih secrc·­

tiott~, i>y inhaling his etnanations in the

"ick roottl, or by the use of contam­in<~tl'd fond or beverage,., there \\'nuld

he t<o imaginable rea,nn why till' dis­

ease ~hould not he tran~mitted :tt !\Tex­

ico '"' well a" at \'L·ra Cruz. ~nrh n<>t being the ca,.,e, we mu"t inter: tir,.,t,

th:tt a f:tdnr ll'l<ich is nece,.,sary for the tr:tn,.mi~sion is pre,ent at \'era Cruz.

hut is :thsent from ~fexico; atnl second .

from tilL' circumstance of the disL·a"e not i>ei<Jg tr:tn,.tni,.,.iJ,J,· through the

fcnm,., of expo>:>ure l.!llllllH:rated aho\'L·,

that the yellow-fever germ i,., patho­

genous only when introduced in" less tri1·ial manner, prohahly by inoculation

1111der the epidennis or even directly intn a blood-1·esscl. Hence my theory

of the mosquito. 1\-~·w .Jf<,squito Theory.- .i\ly orig-­

tnalmoS(Jllito theory, however, in 1·iew

of the facts brought to lig-ltt by Dr. T.

H. Smith. in his admir;tl>le denwnstra­tinn of the tran;,mi~sion of the Te:-.ts

fever through the agency of the cattle tick, requires now to he somewhat

modilied. ~o a, to include the important

circun-:stance that the f:tcttlt,· of trans­

lllitting the yello\\'-iel·er~l'l'll1 need not hL· limitl'd to tltc parent ins< ct, directly

PSYCHE. [July •~Q9-

contaminated hy stinging a yellow-lever patient (or perhaps by contact with or feeding from his discharges), hut may be likewise inherited by the next gener­ation of mosquitoes i~sued from the con­t:uninated parent. \\ 'ith this new

development, indeed, the theory seems to coyer the wlwlc ground of conditions \vhich arc known to govern the trans­mi~sion or non-tran~mi~siun of the di,.;ease. :111d to account for every well :lllthenticated fact on record.

There are dift(-rent ~pecies of mos· qnitocs which :ue peculiar to ccrtain localities. cYen \Yithin the yellow-feYer zone, though we are not able to :tccotmt for their preferences in this respect. nor for the circumst:mces which determine their pcrm.onency in such limitecl :1re:1s. Tt is a fact. howcYer, that the " dome~­tic mo~quito" (h_Y which term f mer~n such specie~ as constitute a p:trasite :llld commens:il of man) slunl"~ no inclin:t­tion whatc\"er for extcnsi\'e excursion ~n long as the female insects lind at hatH! com·enient subjects from whom they can draw the warm life-blood which they apparently require, not so much for their own nourishment as for the flurposes of O\'ulation and for the repro­duction ol their species. That the tropical species cannot \Yell establish themsch·es in temperate or cold cli­mates, will he re:tdilv understood hv rqwating the tollowi;Jg experiments.: Let a mosquito of the small diurnal species found in T-Iavana he introduced into :1 te~t tube pnwidcd with a ther­mometer; if the tcmper:tture he low­(!red. it will he seen th:lt, when it Clils

to between 15 ' and 19 C. (59° and 66.;: 0 F'.), the insect becomes benumbed, and unless it finds ,.,omc ol•jcct upon which it can fasten its claws it '"ill drop to the bottom of the tube. in a condition of apparent death, in which it will re­main so long as the temper:tturc is kept between 15 and o L'. (59_. and :JZ°F.). On allowing the temperature to rise :tgain, when it reaches ahoYe 1)

0 to 1<)0

l'. the mosquito will gradu:dly reYi\L' and soon reco\·crs its normal agility :md the power of stinging. On the other hand. if the mmquito is confined in a c)o,ed tul)L• and tloe air gradually rare­

fled. the insect :tppears to lose the po\Yer of supporting; ihell on its wings, :md abo th:ot of stitll_·ning its proho~ci~

for the purpo''' of ~tinging. \\'ith tL'IIl­

pnature~ below ::::;° C. (7i' F.). the time re<1uircd hy the culex mosquito to digest the blood and get JTady for another bite is prolonged to ~cYeral

day~; and, according to my oh~erY:l­

tions, the pupae of that species, if kept at tempemtures below 23' C. giYe fiYe males to one female. whereas at 25°-30 C. the proportions are revcr~ed. lT ence it follows that during the cold season in Ha,·:ma there arc comparatiYely fe w mosquitoes of that kind in :1 condition to propagate the yellow fen:-r. "\ t sea mosquitoes will s:ln' them,eiYes from being blown into the water only hy aYoiding the deck and other exposed parts of :l Yes~cl, and in tran·lling to\Yard cooler region~ th,·y will han• ;In ad,!ition:d motiYe for seeking refu~e in the warmer and more sheltered parts ot the ship. li enee the likl'lilwnd of

July r~o;.q. PSJ"CHE. ,

their gathering in the holds of vessels, in which the source of yellow-fever in­fections h:-~s b een, many :1 time, dis­tinctly located. Once hoxed up inside the hold of :1 vessel. the contamin:-tted

mosquito may he reduced to the neces­sity of dr:-~wing its blood supply (fautc de micux) f1o111 lower animals, such as rats, etc., :-~nd to lay its eggs in :1ny collectiop of fresh watl'l' th:tt may have found ih. way through the chinks or otherwise. On land, mm-quitoes will instinctively frequent the basement or ground HcH)r of hou,es in preference to

the upper one,, and they seldom seck the open air of their own :-~ccord. while their usu:tl functions c;tn he fultilkd under ~hL·ltcr, e'>cept when they are

ready to Ia~ their eg_~s. !'his is in accordance with the matemal in~tinct

,,·hich te:1che' them to procure undi:-,­ttuhed pos,es,ion of "'me "tagn:111t waters lor their l:IrY:tt' during the two

or more week' required fur the com­piete development of the \\'ingecl insect; a condition seldom sati~fied within inhabited dwellings. On the :1pprnach of its n;ctnral death, the parent insect returns to the' s:-~me waters where its egg-s have been laid, :1nd its cadaver remaius floating on the water, to he de\'oured hy ih own lan·ae. Entrapped

during the uncon,ciott" act of a per"m putting on his hat in a contaminated locality, mosquitoes may he CfJn\·eyed to di,t:mt house~; ;l!ld inside of boxes, trunks, p:ucels, de .. prm·ided that a sufficient degree of moisture and p:tr­ticles of a\·ail.t ldt• food exi~t in their

conveyed to any distance that may be reached within the natural term of the in~e ct's life (which sometimes lasts as mnny :ts thirty or thirty·five days).

~Tv experiments upon yellow-fever mosquitoes have already been pub­lished; their n:sulb may be thus briefly recorded: first, Reproduction of the di,ea~e, in a mild form, within five to twenty-five days after ha\·ing applied contaminated mo&y_uitoes to 'usceptihle suhjecb; second, partial or complete immunityag:tim,tyellow fe\·er, obtained e\·en when no patlwgenous manifest:l­tion had followed th<>Sl' inoculation>.; third. fin:tll_v, the coincidence ofculttttes nwde with the heads and proho:-,cides of contaminated nwsquitoe:-, gi\'ing the identical micrococcus in tetr:~ds (i\I. tetragenus febris flavae; l\1. tetragenus Yer~atili», Sternberg; tetracoccus \'l'r­~atili') prn·iously di,co\·ered by me, in coll:thoration with Dr. C. Delgado, in

the blood :tnd secretions of yellow-fe\'er patients. ·

\\'ith such an nrray of nidence (pre­sumpti\'e or otherwise) as to the rt.Ie of the mo~quito in the propng:-~tion of yel­low fe\'er, :md the concurrence of Koch, l\Ianson, and other experts of the highe~t order in their advocacy of a similar doctrine for the tran~misFion of

malaria, the time seems at last come when decided measures of protection ngainst mosquitoes should he seriously con,idered; the more so as the ener­getic spirit of the 1\nglo-~nxon race is :tbout to replace the f:ttalistic npnthy of former nt!ers in Cuh:1 and Porto Rico.

place of Clltdinement, they can he Thl' 'uggc,tion of Koch, calling for

I'S i'CHE.

dwellings from which mosquitoes could he barred out, in order that the German colonies of Eastern Africa might he freed from malaria, ought surely to be acted upon in countrie~ where it is not only m:-~bria that bas to be contended with, but abo the dre:-~dful yellow fever, aptly called the" plague" in the early Spanish chronicles of i\p1erica, from its :1nalogies with the Orient:1l dise<tse of that name. \\rhy should not the houses, in yellow-fever countries. be proviJed with mosquito blinds, such as

arc used in the United States as a mere matter uf comfort, whereas here it might be a question of I ife or death? The mosquito laJTae mig-ht he de,troyed in swamps, pools, privies, sinks, street­sewers, and other ~tagnant waten. where they are bred, hy a methodical use of permanganate of potassium or other such substances, in order to lessen the almndance of mosquitoes; but the most c-ssential point must be to prevent tl1ose insects fr6m reaching yellow-fever patients, and to secure a proper disin­fection of all suspicious discharges, in otJer to forestall the contamination of those insects. \Veil ventilated hospitals should be built on high grounds, with

no sttgnant waters or marshes in their vicinity, the doors and windows pro­tected by mosquito blinds, a good s\S­

tem of drainage and sewerage, with facilities for disinfecting all suspicious discharges, and for destroying ~uch

mosquitoes and larv;~e as might be found within the building. Only the upper stories should be occupied hv the ~ick, aud none but yellow-fe\'er patient!'. and such malaria patients as are im­nmne ag:tinst yellow-fever, &hould ht·

admitted. The examn1ntion for admis­sion might be carried out in a separ;Jtc building, and a separate departmeut de1·oted to suspicious cHses under obser­vation.

\Vith -.nch h";.pit.tls at hand. :.nd an efficient hoard of health that \\'ould "l't'

to the proper arrangements for patient" who could be left in their homes, and general s'tnitary improvements in and around the principal cities, there can h('

little doubt that yellow fever mig-Itt he stamped out of Cuha and Porto Ri~o, and malaria reduced to a minimum. It would then he the hu~iness of the port and quarantine otticers to prevent the introduction of fresh germs.

THE COl\IJ\IOTIO.:'\ 1.:--J KANS~\S A:\TU ::-.liSSOURf UPO~ TriE

APPEARANCE OF DISSOSTEIRA 1:\' COLORADO.

BY s. J· l!UNTEH, LAWRENCE, KA:\TSAs.

In looking over the literature upnn Dissnslf'ira longipcnnis Thos .. I was surpri~ed tD find that Ill> detailed record

had been made, i11 litcr:ttnre readily ac ccssilJle to entomolog-ists, of the ~1an.:

fl'ars in Kansas and i\li""ouri caw,ed hy

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