Onde1·stepoort J o·urnal of Veterinary Sc·ience and Animal Industry, Volume 12, Num);er 2, April, 1939.
Printed in the Union of South Africa by the Go,·crnment Printer, Pretoria.
Observ ations on the Life-history of Bunosto- mum trigonocephalum, a Hookworm
of Sheep and Goa t s .
By ll. J. 0 Wl'LEPP, Section of Parasitolog-y, Ouclerstepoort.
lY a footnote of a previous r;ommunieation (1937) the writer very briefly outlined the :>alient feature,; of the parasitie stages in the life history of this parasite. In the ensuing pages these are dealt with in gTeater cletail, and information, which has since become available, is also incorporated.
'l'he fullest and most trustworthy aecounts of the biology of certain stages in the life history of this parasite are two eomm uuica- tions by Cameron (1923 and 1927); in the former the author deals with the biology of the infective larva and in the second larval parasitie stages are de,;cribed. Hesse (1923) supposedly gives the morphology ancl biology of the free living larval stages, bllt Cameron (1923) has "ho1Yn that Hesse's cultures must have become contaminated and thnt his (Hesse's) observations of the 3rd stage larvae were not made on the larTae of this hookworm but possibly on those of a .Vernatodims Hp. 'l'hf' writer (Hl07) agTeerl with Cameron in so far that Hesse clicl uot make his ohHervatiom; of the latter stage on hookworm larvae, but differs from Cameron in thinking that it was not .Yemato- rh'l'·us sp, ll'hic·h He,;se obsen·ed, but probably lan·ae of some Tn:clwstrOII,IJ.IJlus sp.; second ,;tage larvae of both iVPmotodir1.ls sp.
an(] B1mosfo11~1un sp. have relatively very long tail;:; arul this long- tail is retained as the sheath of the third Htag-e infective larvae. On the other baud second stag-e larvae of Trichostron.rn;lvs Hpp. lwve relat.ively much shorter tails, aud an examination of Hesst>'s fig-urf'~
of the second stage larvae, shows it to possess sueh a short tail, whose sheath is retained in the third stag-e ns fig-ured by Hesse in hiH figure of the 3nl stag-e lar·va.
In the eommon strongyloid parasites of sheep Mi'innig has found the following- to he the average length;; in m.m. of the hody anrl of the tail sheaths of 0n1 stage larva.
O.c.* H .c.
I
Tr. col.Average body leng-t-hs.-.-.. -.-... -,---- 0-·-79--.--- 0-·
69 --~
0 · 69Tail sheath............... 0·214 0·142 0·094
H.t. ~ - ~
0·57 t l·l 0· 14 0·326
2
* O.c. = Oesophagostomum columb-ianum.
Tr. col. = 'rrichostrongylus colubr~Jonnis.
N. sp. ~ Nematodirus spath:iger.
305
H.c. -= Haemonchus contortus. B.t. .- Bunostomum
trigonocephalum.
I.IFE-HISTOHY ()lo' " .BCNOSTCHIH'M TltH;ONOCI·:J'HAJXlll .,_
Hc-~:;:;e gi,·es thP b()(ly length of his 0nl stage larvae as 0 ·45 to 0·7 m.m. and from his tignre of the Jnl stage lan·.1e the tail sheath is about 0·!:1 m.uL long-; these IHPasuremenb; agTee fairly dosely with those of a T·ricf,ostrongyl11S larnl.
The writer is able to c:ordinn Cameron':; obsenations on the biology of tue infedive larvae and wishe:; only to ruake t.be followiug renra rks. Eggs removed hom graYid females and cultured at 2G° C.
in a fairly firm medium of sterili~>ed sheep·, fae!'es were found to hat<-h horn the :24th hour· om-Yanls, the majority h;l\·ing hakbed J(j hom·;; after c·omJueJH:euwnt of incubation. The mature larYae hegau to neep out of the meclinm from the fifth clay ouwanls. For hir;
<'XperinJPrJt,; the-• writer c·olleded larY:W from the-• sicle;; of tlw eulture bott-les hom thP 8th day onwards.
The 'niter also triecl the Goode)· ;;kin penPtrat ion technique, using the ski11 of Yery young mice and rats, but in uo instanC'e wa;;
he able to ohserve any larvae attempting to penet.rate the skin, and in all casPs the larYae were again all rec:oYerecl from the surfac·e of
ih(> ~kin nnd none \\'e1·e ohtainecl h om tlw water on '"hic-h the ski 11
hacl been floated. The only response of the lnrYHe "·hich \\'US uotecl
"·as nn inl're;~secl activity "·lwn the skin bt>C'amc> "·nnt1er ;~;; a. rc>:;ult- of its c·oJJtHd "·ith tlw ~Ynrm watt'r belo'"·
\Vit.h l'Pganl to the morphology ancl biology of the Yarious h ee li~-ing lan-ai stages, the writer f?uncl thP~e to be pntcticalJ~, iclentil'al with those l'Pc:ordecl by the wnter (193 1) for Gru.r;erw fJO('li];srPI1s ancl the l'Pacler is refen·ecl to thi,; Hc-c·mJnt for t·ht> JJec·esRary cletails;
the only cliffc>retH'e wns a slight morphologieal one in that the aYt>rage lt>ngtlt of the:' lan·ae:>, aucl r·onspquentl:v ;~lso itR internal organs, "·as slight]_-~- smaller in lJ. trir;ol/or·ejJlllllmn t.han in G. Jlochyscelis. The follo\\·ing nJc•asurements wen· o!Jtainecl by the writer b)- measuring n mnerous f!nshea thPcl t hi rcl Rtag·p lan·n whi!'h hnd been kill Pel hy g-Pntle ht>at.
Length O·ftfi;~ to 0-fi:t2 m.m. AwragP O·fi0(; m.nt.
Hreaclth 0·022 to 0·024 m.nl.
LP!tg-th huc·ca] tnlw O·OlfJ to 0·01() lll.ltl.
Length oesophagus 0·13:) to0-142 JJLJil.
J,pngth tail RhPath 0·15 to 0-FlR m.m.
Uenital jJl'iJI!ordium fron1 aJttPrior t'tHl 0-:!(il) to 0·275 m.1t1.
Exc-retory pore from anterior encl 0 · (1!.)9 to 0 ·] 02 m.m.
Ken·e ring from anterior t'llcl 0·08:) t.o
o-mn
!ll.llLWithout the sheath tbP tot.al body lPngt.h Yariecl fron1 0-4(;4 to 0·545 m.n1. tlw majority of the larne being hom 0·!)05 to 0·510 111.111.
long; thP tail Yariecl in length from O·OG2 to 0·0(i4 m.m. The a.bon ntt>asnremt'nts are slight])' in excess of thosP giYeJJ by .Monnig·.
PA!lASITIC STAGES.
The youngest forms obt.n inefl hy ('a me ron (1927) were intestinal forms which had reached a length of 2·8 m.n1. ThesP IYere 4th stage larvae pnn-iclecl with a proYisional buccal capsule. He failed to observe any forms showing the trnnsitiou from the 8rcl to the 4th
30G
lL .r. OltTLEPl'.
stag-e larvae. The writer suggest,; that Cameron would have observed
thi~ stage had be examined the lung-s, because, as is ,.;hown below, the
\\'riter was able to obtain this stag-e from the lungs anrl never from the inte,tine.
Beller (1928) appears to h;~v,e heeu the first to <·ondmle that infection coul<l be protlul'ed either through the skin or 11er os. He based his conrlusioa on the follO\Yiug experimeu t. Two young sheep (one rlncl two yt>ar old) aucl t'Yo one year old goats \\·ere used, antl one of e<tl'h was infected through the skin ancl the otlwr b\·o reoeive,]
l;~rvae, suspended in \I'Hter, \\·ith a pipette through the mouth. Proper precautions \\'ere taken to prevent oral infection taking place in tlw,;e ,;het'p iufeded <·utaneously. l>rior to the expf>I·iment the faeee,.;
of the she.f'p and goats had been examined on several o<;c·a,;ions and helminths egg;; \\'ere fomHl to he absent in all. The one year old sheep h;Hl about 100 larvae appliecl in moist cotton wool 011 the left ,
qicJe of the che;;t; portions of the ;.;kin were excised after J0, :30, 4f) and GO minutes and immecliately fixed aurl later sectioned; he found that afi-pJ· :~() mim1te~ larvae wpre already present in the ,.;ulwulis. After 17 clay hookworm Pggs were diag-nosed in tht> fae<·es. 'l'he sheep <lied after :_W rlayt> and 42 hookwonnt> were recoveree] from the snwll intestine of which only a small proportiou 1\'ei·e mature. The seeond sheep (two year old) received about 200 lanae into the mouth;
hookwonnt> eggs made thei.r appearance in the faeces after 24 cla:p.
The sheep was slaug-htered after 71 dayR and 112 mature hookworms were colleeterl. Of the two goats, one had about 200 lanae U]Jplied to its ,;kin and the other re<>eivecl about 200 larvae into its mouth.
Hookworm eggs \Yere found to be present iu the faeces of both goats after 17 Llays. In the cutaneously infeetecl goat, slanghtere(l 7J day;;
after infedion, one female hookworm, 22 mm. long \\'as recovered;
the other goat \YUS also slaughtered at the same time and two female
\\·orm,; w!:'re founrl. The faeces of both goats were no"'· neg-ative for hookwornJ egg&
'L'here can be no doubt that Beller set up a cutaneous iufedion in one of the sheep and his finding of Jar·vae in the skin, 00 minutes after exposure, definitely sho1Ys that they hacl penetrated the skin.
The writer, however, <loubts \l·hether t·he eggs seen in the faeces after 17 a,ll(l 24 clays orig-inate<l from thi;; exposure; although no st.rong·ylid eggs were pre,;ent in faeces prior to the experime11t, the possibility that thet>e animals wer,e infeetecl prior to the experilllent is not exeluded as hookworms may haYe been present wl1ich had not yet re;u;hecl the egg laying- :;tage. The eggs observed after 17 days in oue sheep and the two g-oats ancl after 24 days in the other sheep most probably origi11atecl from such worms which had rto\Y becorne mature. That the oue sheep harboured hookworms from two <liffer·ellt iufeetions is ,;hown by th,e worn1;; recovere<l from it at post morten1 :16 days after the enta11eous infection; Beller state:; that only a small ]Jroportion of these worm:; were mature, the remainder being smaller. The nwture worrns probably laid those eggs \Yhich \\·ere Reeu ou the ] 7th dav ancl the remainino· worms were the r,e;;ult of the eutaneou~ infediou·. At post mortem"' uf the other sheep and two goai:t;, 71 days after infec-tion, onl:v mature wormt> were fo111l<l to he pre;;ent IYhich i,; what one \\·otdd expect as, according to the writer's findings, the larvap heeome mature frorn lhe lOt-h week after infection.
~07
Ll FE-Il LSTOJIY OF . ' H UXOSTO~l t; J\1 Tlnl; OXOC t·:l'HALC~I
'l'he writer carried out his experiments on lambs, reared from ewes which were known to be free of this parasite, and which lived in a paddock where the parasite had never been present. The original material was obtained from a sheep brought in from the Beth a 1 ] )istrict; this sheep was killed and post mortemed on the same day of its arrival and never came into contact with any of the sheep kept at the Onderstepoort station; these latter sheep being knmvn to be free of this hookworm. The Bethal sheep carried a heavy IJ1/,/wstomum infection and faeces obtained from the rectu!n were mixed with sterile sheep faeces and cnltured in jam bottle;; m
the usual wav at 26° C. Numerous hookworm la rn1e were recovered from the side; of the bottle from the 8th day onwauls and these larvae were used to set up an infection. Seven lambs an<l three young goats were used in the first experiment: These were divided into two groups nml treated as follows; four lambs an<l two goats had adiYe larvae applied behind their ears ou six consecutive days and three lambs and one goat were on the same days drenched with a minimum amount of wnter containing active larvae in suspensiou, care being taken tbnt no moisture with suspt>nded larvat> esr:ape<l from the mouth.
Faeces from all these sheep were eollected weekly from the 8ixth week onwards and cultured at 26° C. and the resultant larvae examined for hookworm larvae. Nine weeks after the commencement of the experiment one of the sheep, which had reeeived active larvae behind the ears, die(l, and on po8t mortem abont two hundred almost full-grown B1mosto IIW 111 trigonocezJhal'U?n wer·e found. 'l'he feJllales eontained no eggs in their uteri. Tbe parasiteR neeupierl the whole of the ileum posterior to the duodenum. 'l'be sheep was Yery anaemir and showed degenerative (fatty) changes of the liver and marked gelatinization of the fatty tissues. As all possibility of an oral infection harl been exduded it followed that this severe infection could only have originatefl from the larva.e applied behind the eanl, penetrating- the intact skin.
A week later, i.e. 10 weeks after the initial infection, one of the cutaneously infected sheep began to pass hookwonu eggs iu itH fae!'.efi as revealed by the presence of hookworm larvae after culture. The following week, i.e. 11 weeks after the initial infectioin, the remain- ing two sheep which were cutaneously infeetecl also began to pass hookworm egg8. Up to this time all the goatR and the two orally infected sheep remained negative. The two orally infected shee1J, however, began to pass hookworm eggs 14 weeks after the initial infection ancl the orally infected goat also pasRe<l hookworm eggs two weeks later. ThJe two goats infected <·utaneously remained uninfeded and were eventually discharged from the experiment aR negatiYe, after they had been observed for 18 'web.
From the above results it was quite clear that infection coul<l be brought about either through the skin or through the mouth; whether larvae, which are admitted through the mouth, pass direct to the intestine and there complete their development, or whether they first have to migrate through the lungs, has not yet been establish eel.
308
R. J. OllTLEl'P.
Having now established the faet that larva of B. t-rigonoce]Jhalwtn can penetrate the intact skin and eventually reach the intestine t.o complete their development, the nf'xt step was to ascertain the route followed hy the larvae.
Three lambs were used in the next experiment and each reeeived a single application of numerous 3rd stage larvae hehind the ears.
On the 8th day after infection one of the lambs was killed; eighteeu ani and early 4th stage larYae, still ensheathed in the sheath of tlw tlrd stage, were recovered from the lungs; most of these latter had already developed the provisional mouth capsule, hut in ,;ome only the beginning;; of the capsule were eYiclent. A minuh• examina- tion of ull the scrapings from the w bole of the trac-hea, oc-,;ophagus and small intestine failed to reveal any hookworm larvae. This lamb thus showed t.bat larvae had traveiled from the skin and ha(l reached the lungs, but had not yet reached the intestine; further that the larvae hacl undergone development during their sojourn in the lungs as shown by the different ;;tages of development of the larvae re(·overed. The ~econd lamb ,,·as slaughtere(l 11 clays after infection and its trachea, oesophagus, lung-s and intestine thoroughly examined. Only one early 4th stage larva was retovered from the lung·s and this larva appf'ared to have iust finished the development of its proYisional mouth capsule. Two 4th ~tage larvae were recovered from scrapings of the intestine; they '"ere exsheathed and the provisional buecal capsules were provided -with dorsal and ventral lancets. Sex difff'rentiat.ion harl not yet become evident. Scraping-s from the trachea and oesophagus were negative. The third lamb wns slaug·htered 15 days after infection and the organs thoroughl.v examined. Larvaf' were absent from the lungs and none were f(nmd in scrapings of the trachea and oesophagns. In the intestine 45 4th stage larvae were recovered, all sho,Ying sex differentiation hut no development of the adult mouth eapsnle.
The lungs of all three lambs showed punctate haemorrhagic markings on their outer surface; these markings were numerout; in the fin;t. lamb slaughtered, less in the second lamb, and only five werf:' seen in the last lalllb. On section tlw lungs of the first lamb showe!l extensive hlf'edings into the alveoli.
Front the above experiment it is evident that in travelling frolll t.he skin to the intestine, the larvae passNl through the lungs where they passed from the 3rcl to the 4th stag-e. Although no larvae were recovered from the trachea and oesophagus one is justified in assum- ing, frolll analogy of the route followed by other hookworm larvae, that they had travelled via the blood stream to the lungs and from ther·e via the trar:hea, mouth and oesophagus to the intestine. Also that the time taken to reach the lungs was less than 8 clays after infeetion and to reach the intestine between 8 and l l days after infection.
The next experiment was undertaken in order to asc·ertain the Ahortest time in which the larvae travelled from the skin to the lungs, the length of time in which larvae could still be recovered from the lungs, and whether larvae could be recovered from the blood, trachea and oesophagus en route from the skin to the intestine.
309
LIFE-HISTORY OF " H17l\OSTOMU~I THI<;OJ\OCI-:l:'IL\Ll"M ''.
In this exverimeu t nine lambs were used and each rec:eived a single apiJlication of uu 111erous ac:ti ve 3n1 stage larvae behind the ears. T'he first lamb was slaughtered three days after infection; the blood was collec:ted, hydrolised, sedimen ted and ceu trifuged aml then cmd u lly examined; the lungs, trachea, oesophag-us a tHl in I.e~ tine::; 11·ere abo utrefully examinerl, but in no case was any larnt rt>covered. The second aml third lambs were killed four an cl fiYe cla vs after infediou respectiYel.v and ,.;imilarly exalllined hut ,,·itb uegatiYe results. The fourth lamb wa,.; killed six clays after iufect.ioJJ ancl ,.;i1nilarly examiued and about 20 third stag-e huvae were recoYered hom the lungs; blood, trachea anll oesophagu,.; "·ere negativt>. The fifth lantb ''"as killecl 8 days after i11fedion; truchea, oesophagu,; and intestine \\'ere negative for larvae, hut about 400 :~rd and -:l:th stage larvae "·er.e recovered from the lungs; the 4th stage larvae were encysted in the 0nl stage cuticle and the prm·isional mouth capsule ,,·a,; preseut. The :;ixth lamb was slaughtered 10 days after infedion; trachea, oesophagus and iutestiJJe were negative for la rvaP, hut ahou t 50 3rd and 4th stage larvae were recovered from the lungs. The next lamb (7th) was killed 13 clays after infeetion; unfortunately, while the lungs were being examined, the oesophagus aJJcl intestine were destroyed and consequently were not examinecl; the blood and trachea were negative for larvae; only oue :~rd aud 011e 4th stage larva \Yere recover·ed from. the lungs. The eighth lamh was killed 17 days after infection; blood, hlllgs, tral:hea and oesophagus were negative for larvae, but 3!) 4th stage larvae "·ere recovere1l from the inte;;tine, all of which showed sex differentiation: The last lamb (9th) was killed 20 clay,; after infection; no larvae were recovered from the blood, lungs, trachea and oesophagus; about 100 fourth stage b rvae were recovered from the small in testiue all of which showed sex differentiation; the largest lila les ,,·ere 0 · 17 111111. long and the largest females 3 · !39 nun. long.
The following conclusion ean he drawn from the abon' expen- ment. Firstly, the larvne are able to reac·h the lungR in six days;
a.lthough no larvae were rec·overecl p.rior f.o ~>ix days the possihilit,v of their reaching this site in a shorter periocl is not excluded heeause ::unong the larvae recovered after ,;ix clays, so.!Jie showed uo further development, showing that they had just recently reached the lungs, whereas some had proceeded t{) develop and had real·hecl the lethargus stage, sho,ving that they had reacbell the lungs some time previously, ::lecondly, the larvae eoutinue to develop in the lungs anrl pn,.;s over to the fourth stage in thil:l organ. They !'all remain in this ~ite until the VHh clay and possibly up to the loth day, but ns shown hy the [He,·ious experiment, they may reach the intestine on the lltlt day.
'l'he writer believes that all the larvae clo not reach the lungs at:
the same time, the interval lwtwePn those first reaching the lungs and the last to do ,.;o being !lue to whether the larvae enter a hloocl
ve~sel sooner or latPr after penetrating the skin. 1'he first larvae to reach the lungs would ('Ontinue their devel·opment ancl also be the first to migrate from this organ, whereas those reaching the lungs later ''"ould only leave this organ and 1·each the intestine after an interval of time equal to that separating the first ancl bst unival of the larva in the lungs. Furtlter. it woullcl appear that the time spent by the larvae in the lung,; iR about five days, bec·ause there
~no
1l.. J. ORTLEl'P.
was an int.en·al of fivt days between the first appearance of the ln.nae in the lung;; and their fir~! appearance in the intestine. If this i::; truE' then it follows that no larvae reach the lungs after 12 daYs after infection becaww hom the 17th claY onwards no larvae WE',rt' rec·overe<l from the lungs and onl)· iutestina"l forms "·ere present.
The next experillJE'n1 was c:n rie<l out i11 order to folllow the
dt::n~lopmental ;;t.ages of the intt>stinal forms of I his parasite. Six lambs were used for this experiment. All \Yere once exposed to a mnssive infection of adi,·e ~lrd stage lan·ae appliPd behind th'3 ears.
A lnmh was then ;;laughtered at 0, 4, 5, G, 7 anfl 9 \\·Peks after exposurP. The lamh ~;laughtered after :1 weeks hud only 4t!J sbge larvae iu the inte;;tine, somP of \Yhich were passing into the next stage. The larvae recon~recl from the riamb slaughterP<l after four weeks hall the adnlt mouth n1psule full_y develope<l, hut all were still enclosed ill tht> Ht>pantlf•d f·ut-icle of the fmn!h stage.
Of the remaining- four lamhs, three, ,;]aughtered 5, (i and I wt->eks aft.er infection, onl)· hafl adolescPnt m:1:les a.n<l female~ present all of ''"hi~h had nude1gonP ecrl.1·si~; in the lnmb slaughtere<l 9 \Yeeh after infection mnture IU>rms "·t>re t·olleded whosp female,; had seg-m en te<l eggs in their oYej ectors.
The result of all the foregoing· experiments may be SUJJJmari~ed
as follO\YS. Eggs are able to hatc·h with in 24 houn; under suita hie L"OIHlitions of temperatUJP and moisture. The first stage llan·n which emerg'es pa~:o;es through the sPc·onn stage lllld reaches the in£ec·tive 3rd stage in five day::;. These lnrYae can set up nn infec·tion Pither through thP mouth or through the skin. \\~lwu applied to tlte skin they penetratt> it a-nd pre~umably enter a bloocl Yessel and are then can·ied hy the hlnod to the lungs whif·h they rench within six clays. ln thi~ organ tl1ey remain for ahout fi1·e days <ltuing which period they g-roiY and pass into the next or fourth stage provicle<l w1th a provisional buccal capsule. They no"· nndergo an ecd;~·sis nnd p1·esumably creep up the trachea to the mouth and are then
~\Y:1llo1Yed. 'l'l1<>1' reach the int·estine from the 11th day onwards as )·ou ng 4tJJ stag-~ lanae; here tht>). g-ro11· a ncl on the J 5th clay. and perhap,; earlier, sex ditterentiatimt becomes apparent. They continue to fee<l aucl gro"· aud in three weekil after infe<·tion they hegi11 t.o
pa,.;~; oYer to the JJPXt or final stage. In four weeks the ad11:Jt sblg<> is
<;omplete<l but tht> lana<" nr<> still enclose<l in the cuticle of the preYious or 4th stng·t>. During t.l1e fifth \Yt>ek the cuticle i,.; shed and the emerg-ing- forms from nnw onward continue to feed and grow until the 9th week, when the.Y are fully mature ancl the females
<·ontain segnwnt<>d eggs.
"MOHPHOLOGY OF THE LARVAE.
'l'he morphology of the free living, first, second and third stage brvn.e (Fig. 1) is i<lenli<·al to that <le,:;cribecl for the <·orresponcling stages of Gnigrria pachysr·elis, exc·<>pt. that the third stage lnnae is slightly smaller. The nJorphology of the pnrasil ic fourth and fifth stng-et; have heen acleqn:Jiel_v de<snibecl hy Cameron (1927). An examination of hi,; tlt'sniptiom; a11<l clrawings shmYS thnt the enrliest
au
LU'E-I-IlSTORY OF ' ' lJCl\"OSTO.HCH TlUGO~OCEPI-L\.LUM ' '.
forms which he was able to study correspond to those found by the writer from the third week onwards after infection. Below the writer will iu consequence oonfine himself to the parasitic portion of the third stage and to the fourth stage larva.
, O·tmm.
l<~ig. 1.- Anterior and posterior extremities of third stage larva,
0·171Z7/t-.
Fig. 2.-Late third stage larva from the lungs just prior LO onset of lethargus.
~12
R. J. ORTLEPP.
\Vhen the infective la.rYa penetrates the skin it presumably also casts its envelloping cuticle, all larvae which were recoYereJ from the lungt> being exsheathed. 'l'he youngest larvae recovered from the lungs, six days after infection, appear to haYe undergone very little or no development; their _si:r.e and shape of oesophagus was similar to that of the infective stage. Once in the lungs they proceed to grow and this growth is very marked in the lateral direction in that a considerable thickening takes placP accompanied by practically no increase in length. This thicknes~ is <hle to changes which take p1lnce in the oesophagus and intestine. The accompanying figure (Fig. 2) shows a late third stage lana which is on the pom t of passing into the lethargns stage. It will be noted thnt the oesophagus and intestine :n·e much robu:-;ter than similar organs found in the infediYe stage; the lengtht> of these organs have also undergone a slight change, the oesophagus increasing slightly and thP intestine decreasing slightly in length. The folilowing table g·ives the chief measurements of five late third o;tage larYae just prior to lethargus (measurement in mm.).
1. 2. 3. 4. 5.
Body length .. 0·522 0·510 0·505 0·5 0·52:!
Body breadth ....... 0·046 0·04:1 0·044 0·058 0·055 Length oesophagus ... 0·177 0·16ii 0·165 0·17 0·151 Max. thickness oesophagus .... 0·02 0·018 0·018 0·02 0·01!) Length of tail. ... 0·046 0·049 0·04!) 0·045 0·058 Length buccal tube .......... 0·016 0·015 0·015 0·015 0·016 Nerve ring from front .. O·ll6 0·119 0·112 0·115 0·121 Ex e. pore from front .... 0· 123 0·13:3 0·11!) 0·12 0· 13 Genit. primordium from tail tip 0·216 0·232 0·223 0· 21:1 0·22
- - - - -
'\Vhen comparing these lanae with similar stage larvae uf Gaiger£a JJachyscelis it will be note<l that morphological1ly thet;e two are ve1·y si Ill ilar, the ouly apparent difference being that the Ia rvae of B. fr1gonocep/wl71m. are slightly smaller. 'l'hey have the same reddish colour and show the same t,ype of movement prior to tlethargus.
Duri11g letharguH the sallie t.ypro o£ morphological changes set in, the lliOSt marked of which is the development of the provisional huccal capsule. The first indication8 of this caps1de is a hreaking up of the body tissues het.wePH the anterior and posterior levPls of the buccal tube; at. first the oesophagus i:-; not involved, but :1:-;
development procf'eds the breaking up of the tissup also enf'roaf'hes on to the outer !limits of the oesophagus. A cavit.\· round the anterior tip of the oesophagus is thus formed whose outer border hef'ome"
cuticularized. Eventually the whole of the anterior tip uf the oesophagus disappears, except its cuticular lining which remair.s a~
a thin stran<l joining the old mouth of the third stage larva to tli<>
base of the buccal capsule of the fourth stage. Figures 0 A and. B show the anterior extremity of a larva in which the buecal capsule i~
partially developed and Figure 3 G shows a llarva with the capsule 310
f.JJ··J·:-ILI STOH 1 01' lll'SOSTO~ll' ~I T Jill di:">OC I·: I'LL\ IX~!
t;Oillpld ely fon11ecl. ily tl1is time a nt•\\· eutide lw~ hee11 formt:'ti <IIH!
the lan·n i~ now surrounded hy the det:u·l1ed t·nticlP of the third staw·. 2\/o se:-; di!fertmtiat ion h;1s _vPt taken place nnd 110 tedh or
lant·et~ are j)I'!'SPJJt :'tt the hu~e of tl1e huccnl capsllle. Ftirt·her deYelopmPnt in si;~,e t.:d;e.~ placp ;n tilt~ lung.~ <11111 the lan·ap :11·e now ready to migrnt.c to the intestinP. Fin· enshPatlwd fourth ·d:q.~·e
larLw, I'Pt·o,·erPd fro111 tiiP lung·., eight. days aftPr infPd.i.on, gan• the following j)l'LJII'ip[e IIH'<lS11H'IIIPIIh in nllll.
I. :!. :{. -L :).
Length of hudy inc·luding
sh(·ath. ... II 5BI I) :;:1n II :;;;I II ;)f)~ II ,-,.-,7
Lcn~th of hocly without sh<'ath () 57 I)
'" L () ;;:\ II •>8 I) ,;:n
Brt'aclth of hodv. I) I)() II 0!)!) 0 ();ji{ 0 o,;;; () ()!)f)
Le11gth OC':·Hlpha..gu~. 0· I :il II· I :i:l ll· I+•> II· In II· 14s
M.outh (·a.p~tde, drpth ..... I). 0:!!1 I) 1)~7 I) O:lG I) O:W I) II:W Mouth eapsul<·, hrt'adth. II o:11 II 0:!8 0· O:W II·O:W 0 II:!! I
Ex<'. porr fn1rn front. II· I ~7 I)· 1:!:! ll· l:ll II· 1n
N('n'<' ring from front. II· I Iii I)· IU 0· II II· ll(i tl· II:!
L<>ngth of tai I a.nd shpath . 0·05S I) Oii6 I) ();)8 I) 06 O·tl•iS L<>n~th of tail wit! tout shrath. II 0+:> I) 11:!8 0 0+:! II 0!) n-o+·>
Gen. primonliurn from tail tip
(<'.x!'lucling sheath) .... I)· 27:) II·:!+!J 0· :!+7 0· :!+(i 0· ;lf):!
A. J3 .
C.0·057llut,
o -rmm.
F'i~. :L :\. B, :111d ('.- Antt>rior t>:o\ln•IIJiLiP~ of fourth stag:t• lar\·:tt• showing clc·\·t'lopnwnl of prO\·isi"nal hll<'<·al t·a
I " "'''·
Tht• ~IIJ:dlP~t t·n~ht•:ttht>tl fourtl1 ,;I:Jg-p lar\':t t·'lli'OUnti'I'P<l \\':tC\
0·:->IH n1111. long· with a lllaxinllJJJJ thi('knp,;,; of 0·04!i n1n1. :tnd rhe larg·est lana of this ~tagt· 0 ·!j\F1 111111. long "·ith :t nmxi nn1111 t hici;nP>'s of 0·00:!. the ~hPath exel11<lPrl in :tll nH·:t~UI'Piltf'nh.
\Yheu the lan·al' rench the iutestiuP from the llt-h da\· 011\l':tl'lls nftt•r i11fretio11 they havP ulre:uh· lost tlwi1· sheaths. The ·,niter ha,;
not been able to ;.e,·oYer nny l:;n.:tt' in th(• prot·e;;,; of (·;J.-<ting their skin anrl hP is in eousef)uenl'e not ahlt> to ;;tate "·hethrr el'dysi;; t:tkeK place in t·he lung·s, rluring mig-r:d.ion to thP intt>sti11e or nftt>r I'P<H:hillg- the inte,;t·i11P.
R. J. OHTLEPJ'.
AHer reaLOhing tht· intt-stint>, tlt>Yelopment pro<"eetl~ more rapidl:v, the younge~t larYae rPCOYf're<l from thE' intt>stinp \Yt->re two larYae O·SJ(i and 0·828 n11n. long, "·hid1 hatllo:-;t tht'ir ,;hf'ath~ and in whirh sex diffPrt->ntiatiun had not yet taken pla!'e. 'l'be principal measure-
JlJPn t·s i 11 Jlllll. of thes.- h,·o Lu·Yae ~~ rp giYe11 helow : --
Length of borly. . . ............................ . llrearlth of hody... . ... .
Length of oC'sophngus ..
Maximum thickness of OC'Sophagus ..................... . HucTa.\ capsule, dl'pth ... .
llurea.\ capsule, breadth .. . Exc. pore frorn front. ..... .
Nerve rin~ frorn front, . ............................... . Length of ta i I. ..
I.
0·816 0·05(\
0·234 0 03:1 0 031 () 03 0·168 0· 150
() 078
I
•)
0 8~8
0 Oii8 0· :228
o·m6
0·033 0·032 O·liiO 0· J:l5 0·0:)8 - - - -
A ,;triking fea ttHP of these Ia n :w as t·om pared with fourth stag-P lan·ae re('o\·Pred fru111 tlw lung·s wa~ t.hnt .in thP intt'~tinal form a dorsal and two subventrnl lann•ts wen~ prt>sent in t.he hase of thP
c-ap~1de (Fig. 4 A) "·!wrens tht>~t· \H'rP :1hsent in thP lung fortlls.
Fig.
A c.
0· 2 l!l7/l.
4.- A. Anterior pxtremity of fourth stag.· Ia rva s[,owinll: fully de,·t·lopC'd provisional btHTal rapsul<> with portion of an intPstinnl villus.
B. Posterior extremity of lllak fourth stagP lana.
C. Posterior extremity of f<>mal<> fourth stage lan·a.
315
The uext lut uf larYae recoYered from the iutet>ti ne w<"re from a lamb which had bee11 cutaueously infected 15 <lays previou;;ly. These lan·ae all showed se.s. (li:fferentiatiou, lhe n10st marke<l exteruul feature being the stump:v taib in the males and elongate tails of the felllales (Fig. 4 H and ('); "·hen·as in the larYae reco,·en•d 11 days after iufeetion t.he huc!"al c<1psule \Yas iu a straight line with the longitudinal axis of the hod.Y anrl the mouth aperture faePd directly forwardK, iu thei't' latter lanae the hucc:d cap,;u}p was tilted <lorsal- wards and corrsequently the lllouth fa<;ed <lntero-don:Hdly .
.lu the follo"·iug- tahlP the priucipal measurenH•Ilts in nun. of thE' lar·g-est t.hre-P males and lhe largt~;;t threE' felllales :n·t• givPn :-
MALE~. FE:\lAr.E~.
I. :!. :l. I. ·) :L
ilody length .... ~-76 2·{i\) 2·04 2·:!.7 :2·8:3 2-i)!) Body thieknC'Ss. 0· 12 0· I 16 tl· 102 O·l:! 0· 168 0· l!i Length oe~ophagus. ....... o-.n 0·468 o-:1\JG ll·48 l)·!i4 0·4:>H Tbiekness of OPsophagt"
Ant. end. 0·04 0·04 0 ·O:lli 0·04 0·044 0 04~
l'ost. end ... 0·06 0·057 O·O!i 0·048 0·063 0 ·O!i7
Huccal mpsulP~
Depth. ()·\)54 0·058 0·048 O·Oii-1 1)·06 O·OMl
BrC'adth. 0·06 0·06 O·OMl 0·06 0·072 O·Oli6
I~ X('. pore from front .... 0·03 o-:lo2 0·264 0·3();) 0·:312 o-:l
Nerve ring from front ... 0·282 o-:1 0·:24 ' 0·27 0·:1 0·264
Cen·ical pap. from front. 0·:!9ii 0·288 0· :!:)7 0·2!J () <11 0·:!8!i
Vulvn, from tail tip .... 1 ·16 I ·46 l -~
Lcn~th tail. .. 0·09 0·072 O·O(; 0· IOH 0·12 0·1:!6
'l'he.~e larvae sho1n•d r1o sign of a dt>velopiug adult mouth
eapsule. The g-enital primonli urn of the rn;des ha;; seg-menh•d and shifted and •·onsi;;;ts of <I row of .-ells to1Y:l rds t be posU•rior end of lhe body. Tn tht> fen1:llf' the YUIY:l ha~ he<.:on1e cl<•m:Hcatt>d nnd tht>
g~~nit:d eells b<t,·e ~wg-mented h> for111 an anl.l'rior and postPrior ro,,. of cells, ,,·hich ,,·ill gin• rise to the uteri ancl oYaries, and <l t"l'ntral ma:;s of <;ells ("tlllllef"ling· tht>s<• b1·o rm1·s and the ,·ulYa; this t·e>ntral maRs of t·elb is dPstinetl to form tbP ,·;q:rin:L
LarYae rel·o,·ered 17 daYs after infedion ,-;howed tht· sanlP rnorphologi<"al d~·lails <lH tho,;e' tleseribed :1hon·, t•xcept tlwt the body hud ht~t·ornP larg-er and tht• gt'nitalia had t·ordinuf'd to g-ro11·. The brge,;t female was 2·K mn1. long- and O·Ir>G rnrn. thick :md tlw largest male 2·:{!) nnn. long and 0·12 mm. thick. 'J'ht>roe was no sign of a developing adult mouth r-ap;mlt•.
Larvat• reeovert>d 20 days after infection abo showed no ::;ig-us of
<L deYelopiug adult mouth cap:;ule. The largest female was :1-54 llllll.
long a11tl 0·192 mn1. thick and the lnrgest male ,,.UK :{-:l(j 111m. long anc1 0·19 111111. thick.
Ou the 21st da1· after infedion larvae were recoven•d in which tht· heg-innings of 'the adult rnoutb capsuiP ''"ere just noticeable.
These. howpver, ll"ere not· I Ire largrst. lnn:w; the largeRt female wus 01G
lt. :r. ORTf.],;pp.
3·~ mn1. long aucl 0·194 mm. thick aud the larg-est male 3·1 mm. long and 0·15() u1m. thick. The female larvae, where development of the adult mouth capsule had commenced, varied in length from 3 ·02 mm.
by 0·14 unn. thick to 3·7 mm. loug- by 0·1G8 mm. thick. Ko male larvae showell a d-eveloping adult mouth capsule.
Ln.n-ae recovered from the intestine 28 days after in feetiou sho"·erl a cousiderable further development. The adult mouth eapsule was now fully formed and the provisional buccal eapsule was separated off; a new skin had been formed a ncl tbe lan·ae wer-e ensheathed in the cutiele of the fourth stag-e. The lanae had thus reached their final or fifth stage, the genitalia bad increased in size, those of the male were extending from the posterior extremity of the body to a bout mi dwa.y, "·here the future testicular portion was recurved backwards and made a few loops. The female g-enitalia have not yet acquired an opening- to the exterior, but the vaginal cavity hat:> ma1le its appearance. 'rhe eavity of the future ovejedors can just he made out in some larvae. The rest of the genital a.pparatu,; is still solirl and the future ovaries are reeurveu and wavy.
The females have uow reaehed a length of 4 · 02 llllll. by 0 ·] 98 nnn. thick an!l the n1ales 0-9:1 mm. long by 0·19 mnJ. thick.
The development of the adult mouth eapsule and of the geuital organs have been elearly described anrl figured by Cameron (1927) with whose fin!lings the writer agrees. These appear to he irlentical to those obsen-ations made by the wr·iter on the lanae of Gaigeria pachyscel is.
\Vi t h reg a rrl to the rlevelo pmeu t of the bursal rays the w ri tP r can corroberate C<~meron's (1927) observations. namely that the Jllain Yentral branch of the lateral hands gives rise to the ventral, antero- lateral and part of the medio-lateral rays. This de,-elopment !lifters from that found by the writer to occur in Grri.r;eria pachyscelis; in this hookworm the medio-lateral ray does not arise from the Yentral branch of the lateral bands but, together with the postero-lateral ray, is formed from a seeondary branch arising ventrall.v near the
h<ht' of the dorsal branch of the later·al banos.
From this stage onwards the larvae moult during the fifth week after infection and then feed and g-row to attain sexual maturity in from nine to ten weeks after infection.
13LOLOGY ot-· THE l.'A:rtASITIC TnnlJJ AND l<'ouwrn STAta: LARVAE.
The lung forJUs of the third stage larvae live on blood, they have a red colour, probably derived from the haemoglobin of the blood. Prior to lethargus they are active, negativel,v photo- and geotropie and show an increased aetivity when gentle heat is applied.
The fourth stage larvae attach themselves to the villi of the small intestine, by drawing portions of the villi throug-h the mouth into the buccal capsule, these portions are lacerated by the buccal lancets and the larvae feed on the liberated blood. Both these stages eannot withstand any drying either HI the ensheathed or exsbeatbed condition.
317
J.n'E-HISTORY 01' " BCNOSTO~JrM TIU(:Oe>OC'EPHALUM "
SuMMARY.
l. .Eggs passed in the faeees of sheep or goa is or obtained frolll the uteri or gravid fe111ales are able to hatch in from 24 to 36 houn;
under- suitable eonditiuus of aeration, temperature and moi:>ture.
~. The larvae have three JH·evnra~iti<~ ~tages Pach separated by an ecdysis. The cuticle of the seeond stage is retained as a protective sheath for the third or infeetiYe stage which is reaehetl in five to eight days after hatehing.
~l. Morphologically and biologicall~· tlw <lifferent lanae are pra.ctieally identical to those of Gaigeria ]Jachysr·elis.
4. lnfeetion of the host takes plare either by venetration of the skin or via the mouth.
fi. Afier penetrating the skin the larvae prueeed to the lung·s whieh they reaeh within six days; the route taken is presumabl)r via the blood stream.
6. In the lungs the larvae remain for- about fhe da.vs during which period they feed, grow and pass into the fourth ~tage provided with a provisional bur('al <:apsule.
7. The larvae now migrate to the intestine presumably via the t.rar-h!'a, moutl1 anrl oesophages. When first seen in the intestine they have already Bhed their sheath, but no sex differentiation is yet eYi<lent; sex differentiation sets in ahout fom· <lays latr>r. Hnccal lancets also appear.
8. The larvae nttaeb themselves to the iniestin:d villi au<l feed on the liberatell hlood. They grow and begin to pass into the final or fifth stag<' in ahout a. week after reaehing: the intestine.
9. Final p('dysis takes phwe abmtt 10 days later.
10. Growth <~ontinues ancl the egg laying stage i;; reache<l 111 rnne to ten weeks aft!'r infection.
B KF'ERENCES.
CAME.RON, T. \V. M. (HJ27). On the Parasitic Developnwnt of Jlonodrmfus frigonncephallfs, the ShePp Hookworm. Jnl. Helm. Vol. 5. pp. l49-H12, London.
OH.'l'LEPP, H. J. (1937). Observation~ on the Morpholog;y and Life-history of Ga·i(l1'1'in rxu·h yscelrs B.a. ill. and Henry 1910. A Hook worm .l'arasi te of ShPep and Goats. Onde1·st . . /11/. Vet. 81'. rf': Anim. Indus., Vol. 8, pp.
·183-212, Pretorin.
(ReferPne<~s to additional lit<~rature may be found in the last-named publication.)
318
