LUNOWORMS IN OREGON SWINE
A THESl.S
submitted to
in partial !ulffilaent. of
the requiremcta f'or the
deg;ree of
MASTER OF SCiiWCE
June 1952
rllHfBr
Redacted for Privacy
rf Drryfrd rf ?rfclrsf ffldn
D {t rre d llJc
Redacted for Privacy
t
ffrrd*lrlffirStirr
Redacted for Privacy
Dlrf ffir
I*,r th*r [r
tlrr I lrf* Lu#lln
Grateful acknowledgment ia lli&de to Dr. J. N. Shaw 1 Head 1
Department or Veterinary Medicine tor his help in outlining and
encouragement in the execution of this project; to Dr. J.
Schnaut~,
o.
Associate Profe saor and Dr. J. F. Bone 1 Instructor 1
Department or Veterinary Medicine 1 tor assistance rendered in
conducting this study; to J. E. Oldtield, Assistant Professor
and T. K. Jolmaon 1 Swine Herdaman 1 Animal Husbandry Depart,ment
!or their help in procuring experimental animals and materials;
to Dorothy McKey Fender, Ento.,logist 1 HcMinn"rille, Oregon tor
her suggestions in working with and help in identifying the
earthwol'JU; and to Dr. O. B. Muth, Veterinar1an,
Veterinary Medicine tor photographic work.
De~nt
of
TABLE OF CC!JTENTS
ACKN<liLEDGMENT
INTR<I>UC'l'ION
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REVIEW OF THE LITERATURE
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ibrpholog;y o!' Metastronqlua e1ongatus •
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Classification of SWine Lungwonu
A Reri.ew of PNvioua Work
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Lite Cycl.e of Swine Lungwonu •
Intermediate Host
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Location of Larvae in Earthworms
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Persistence ot Swine Lungwo:ra LarTae •
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THE INCIDF.NCE OF LWGWOBHS IN OREGON SillNE
Method of Examination
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Diacuasion
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THE CORRELATIC.W BE'lWEE'll LUNGWORM INF'ESIATIOlf AND THE
ECONOMICS OF PORK PRODUCTim • • • • • •
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Experimental Animals
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Infectious Material
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Material and Methods •
Source of infectious material
Technique used to determine the degree o!
infectiri.ty of the earthwonu
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Guinea Pig Infestation Trial• •
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Experimental Infestation of SWine with Lungwonu
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TABLE OF CONTENTS (CONTINUED}
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Discussion •
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JmLlOOIAPHI
APPENDIX
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TABLE OF FIGURES
Figure 1
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Figure 2
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Figure 3
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!ABLE OF PLATES
Plate 1
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Plate 2
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Plate 3
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Plate 4
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Plate 5
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Pl.a te 6
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Plate
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LUNGWORHS IN OBEG<Ji a-liNE
INTROOUCTION
Lungwonu are known to exist in all parts of the United States
and Canada.
IJ.terature reporting the percentage of infested swine
was found in only two instances.
Spindler (12, p.42) reported an in­
cidence of 69 per cent of 348 swine examined in southem states.
incidence of
3~
An
per cent has been reported b;y Hawkins in Michigan
(5, p.l78). .ls yet, no tabulation of the per cent of infestation has
been reported for Oregon swine.
Little information has been found in
the literature to show correlation between infestation and animal
productiTity.
The two main obJectiTea of this study were to find the incidence
ol lungworm infestation in swine in Oregon and t _o detennine the ef­
fects of infestation on the economic production of pork.
REVIEW OF THE LITERATURE
Classification of Swine Lungwonu
Lungworas are helminths or parasitic worms.
The;y ant claasifie<l
according to the intemational code of soological nomenclature, each
parasite having a proper phylum., class, order, famil;y, genus and
apecie6.
plu-la:
Helminths of veterinar;y importance are found in one of three
Platyhelminthes or flatworms (flukes and tapeworms), Nematbel­
JBintbe s or rouoivorms and Acanthocephala or thorny-headed worms.
following is a brief classification of the lungwrms of swine as
The
2
recorded by Morgan and Hawkins (5, pp.3.3-.34):
PHYLUM:
CLASS:
NEMATHELMINTHES
Vogt (tro
Carus, 186.3)
NBMATODA Rudolpbi, 1808
SUBCLASS PHASMIDA ChitlDod and Chitwood, 193.3
ORDER RHAIDITINA Chitl«>>d, 19.3.3
SUOORDER STRONGYLIN.A. Railliet and Henry, 191.3
SUPERFAMILY !!ETASTRONGILOIDEA Lane, 1917
Famil7 Metastrongylidae Leiper, 1909
Genus Metastrongylus lblln, 1861
Species (type) el9ngatus (Dujardin, 1845)
pudendotectus (Vostokov, 1905)
salmi (Gedoelst, 192.3)
Morphology of Ketastrong:rlus elongatua
Metastrongylus elongatus, the type species of lungworm in swine,
baa been described by J.j!jnnig (4, pp.209-2l.O).
He reported that the
wrms are thread-like in appearance and white in color.
The male JDa7
reach a length of 25 mm. ; the female is uauall.y larger, reaching a
length ot 58 ma.
The oral aperature is surrounded by six snall lips.
The male bursa is relatively 81118.l.l..
Filaform spicules terminating in
a single hook, and measuring 4 to 4•2
111111.
are present in the male.
The posterior end of the female is fiexed ventrally, the vu1.va opening
in the area of the anus.
The vagina measures 2 mm. in length.
The
eggs are oval and they are about 5.3 microns long and .35 microns wide.
When laid, they contain a fully developed embryo.
3
A Review of Previous Work
Work of the Yarious investigators who contributed to the lmovledge
of the life cycle of lungworm in swine was reviewed by Schwartz and
Alicata (7, pp.2-3).
They reported that J..euchart. in 1876 was one of
the first to believe that swine lungworm was a heteroxenous parasite
with an invertebrate intermediate host.
This opinion was shared by
Cobbold who considered the earthworm to be the intermediate host.
Neither of these men, however, substantiated hie hypothesis with con­
trolled experiJDmts that were recorded.
Work carried on in the Zoological Division of the United St&tea
Department of Agriculture by Ransom and re}X)rted by Kohler in 1920, as
well as an independent study carried on by Schwartz, showed that the
embryonated egg or liberated larva obtained from the uterus of a gravid
female when ted to a susceptible hog failed to dnelop.
Schwartz and
Allcata (8, p.l05) reYiewed the work Hot.aier and Hobmaier published in
1929, in which they found the earthliOrm to be tbe intermediate host in
swine lungvorm infestation and were able to d8100nstrate one molt in
both the definitive and intermediate host.
They confirmed the
Hobmaiers' t1ndinga of the earthvora as the intermediate host but
demonstrated conclusiYely that tvo mlts occur in the earthworm.
Life Cycle of SWine LWlgvonu
Schwartz and Allcata found no significant difference in rate ot
developaent or details
ot migration of the larva
in the inte1"118diate
host and, therefore, treat the life cycle of all three species a• one.
4
In summarizing their tindin s on the life cycle, the folloldng descrip­
tion is given (7, pp.39-40):
Earthlftlrms
beco~
infested with swine lungworm larvae as a result
of ingesting the eggs eliminated with the feces of infested swine.
The
first stage larvae are found free in the lumen of the alimentary canal
ot the earthworm.
The larvae tbe.n penetrate the wall of the esophagus
and are found in greatest concentration in its posterior portion.
Larvae may also be found in !ewer numbers in the mterior portion of
the esophagus and in the wall of the crop.
They are rarely found in
the gizzard, and only occasionally in that portion of the intestine
just posterior to the gizzard.
Sooner or later, the larvae invade the
blood eyst.em and reach the hearts by wq ot the dorsal blood vessel.
The larvae tend to accumulate in the hearts
am
rarely succeed in
reaching the ventral blood vesael..
In earthworms, growth and developaent ot the larvae to the in­
fective stage is accompanied by two molts.
The first molt ma;y take
place as early as eight days after the earthworms have been exposed to
infestation, but uauall7 a longer period is required.
The second • l t
in the earthworm has been observed as early as ten days after intee­
tation
(7,
p.21).
Under natural conditions pigs become infested with lungworms as a
result of 8Wal.lowing infested earthworms which they bring to the sur­
face lllbile rooting.
Once the infective larvae are free in the intestine• of the pigs,
they penetrate ita wall &r¥1 follow the course of the lymph.
The larvae
5
become arrested in the
esenteric lymph nodes and are fot.md there in
large numbers for a few days after experimental infection.
Those
larvae that escape from the lymph nodes reach the lungs presumabq
through the right side of the heart.
The larvae arrested in the lymph nodes, and those lolhich get to
the lt.mgs before molting, undergo the two final molts as early as
three dqs after entering the definitive host.
Further development in
the lungs involves growth and differentiation.
Fully embryor».ted eggs
are present, at least in the species MetaGtrongylus el.opgatus, as early
as 24
d~s
att.er the ingestion of infective larvae.
Intel'llediate Ho at
Four genera of earthworms were authoritatively determined. in the
investigations of Schwartz and Alicata (7, p.l8).
'ftle first tbree
genera were determined apecifical.ly and the last gmerically only.
Von
Schucban and Zunker were reported as finding the first three species
as the intermediate host also, sod noting that Eisenia foet.ida is the
most. suitable ho at.
Tbe three species specifically determined were:
1. Eisenia
.toetida, the coDDOn manure worm, often found in old manure piles and
soil rich in organic matter.
2. Allobophora caliginosa variety
trapezoides, which is found. in much the same location as the manure
worm.
J. Lumbricus terrestrias, the night crawler of fiahertlal.
This
species was not reported by Schwartz and Alicata as being present in
an1•l pastures.
6
The eartlwora that was deter.adned generically only belongs to the
genua Diplocardia.
Macnab and Fender (2, pp.69-75), in their discus­
sion of Oregon earthworms, mention the finding of the first three
apecies in the st;ate of Oregon.
Shope (11, pp.441-442), in working
with lungliiOrm in awine, carried on trials with a species o! earthwonu
not
entioned by the other workers as a suitable intermediate host.
Dr. Libbie Hyaan tmtati vely identified this earthworm ao Octolasiua
lactia.
Location o! LarYae in Earttn.oraa
The location or the larvae in the intermediate host has been
wrked out in detail by Schwartz and Porter (9, p.4.31).
Examination
of 6.3 earthwonaa (EiMnia toetida) lhowed a total of 5,142 larYae.
0!
these, 4,819 (9.3.7.3 per cent) were found in the calciferous glands.
The remaining larYae were found in the anterior eaophagua, hearts,.
crop,intestinea, dorsal blood veeeel, ventral blood vessel and giz­
zard in decreasing concentrations.
The cal1:iterous glands
al"e
dila­
tions in the walls of the e110pbagua in the posterior tour segments
(XI-XV), the lUMn of which ia invaded b7 blood ainuaes.
The .tunctioo ot the calciferous glands is debatable.
and Porter
Schwartz
(9,. p.4.38) state that these gla:rxis are found only in ter­
restrial annelida that live for the most. part in an anoxybiotic envi:r­
Ollllllm t.
the
The calciferous glao:i s · secrete
eaco3
which is believed to fix
co2 , forming Ca(HC03 ) and thereby protecting the earthworas !roa
an excess o!
co2 •
Tbe7 feel that the larvae of swine lunporm are
7
oxybfotic nematodes, just as the adult lungworm& are, and asa\.1118 that
the preferred location in the calciferous glands is due to the fact
that larvae are best adapted to an enviromaent in which
co2
does not
accwaulate t.o an excess.
Persistence of Swine Lungworm Larvae
Spindler (13, p.63) in 1938 reported finding infectious earth­
worms in hog lots that had not been used for the previous four years.
SeTenty-fiYe sexua.ll.y mature earthworms were examined and 35 (46.6 per
cent) were found infested with lungworm larvae.
from one to a hundred per annelid.
The larvae varied
The viability of the larvae was
tested by feeding them to susceptible swine.
The pigs became infested
as adjudged b7 the finding of lungworm eggs in
t~
feces 31 days .a fter
ingestion.
The viabilitY" of lungworm larvae has been studied by B. H. Ransom
of the Bureau of Animal. Industry, and reported by Schwartz and Alicata
(7, p.l7) following Ransom's death.
Two cultures of artificially
hatched lungworm larvae, one in water and. the other in a mixture of
sterile feces and charcoal, were made February 5th
temperature.
am kept at rooa
Daily examination of the cultures was •de.
Aa late as
March 21st, a live larva was found in the charcoal-feces mixture.
Five viable larYae were found in the water culture as late as March
31st,
wh~
the culture was permitted to dry up.
Schwartz snd Alicata
also reported that the Hobmaiera were able to maintain larvae ot
Metastrongylus elongatua in a moist media for as long as three mnths.
8
Viability of the egg of swine lungwo:nn8 has been reported by
Kates (1, p.271) who showed that the tirne of surv1Yal varied with
depth at lllhich
~be
eggs were placed.
Lungworm eggs 1n feces on the
surface ot outdoor unshaded plots were destroyed in 25 days.
Sub­
surface tecee, buried at depths ot 6, 8 and l2 inches contained so•
eggs that remained Ti.able tor 381 dqe - but the majority aucclabed 1n
about 290 dqs.
trials.
Here again, viability was tested. by swine infestation
The exp: r.tmental animals were fed earth-worms rendered infec­
tious by the eggs in que at ion.
9
THE INCIDENCE
~
LUNGWORKS IN OREGON SWINE
"Thumps", or difficult respiration, has been seen in many young
pigs along with poat-mortem d1 scover7 of lungworms in diseased ani­
mals.
'ftds has made the swine grover oonscious of the existence of
thi a parasite and interested in infox,nation about it.
Because reli­
able statistics are lacking, it has been impossible to answer ql.l! stions
concerning the prevalence of thie disease in Oregon swine.
A statistical report of the incidence of lungworm infestation in
Oregon swine vas undertaken as one of the two main objectives of this
paper.
In the earq stages of this investigation only mim.als with a
know history wre examined.
As it became apparent that the incidence
of infestation vas in excess of 50 per cent, all swine known to han
been raised in Oregon were examined in nearby al.augbterbouses.
!his
method made it possible to examine a statistical.l.y' significant nl.DDber
of animala lblle minimising the nlJilber of trips necessary to procure
specimal.a.
In all., sixteen trips were made to the two main slaughter­
houses that supply the Alban7-GorTallis area.
Because of the location
of these slaughterhouses, it is safe to asSUile that at least 90 per
cent of the 518 animals examined were raised in the
ill811ette Valley,
with the majority coming from Linn and Benton Countiea.
Method of Examination
the lungs and trachea vere remved intact from the carcass.
A
pair ot fiYe and one-half inch acissors was used to open the trachea
10
and right and left stem bronchi to their terndnation near the basal
border of the diaphragmatic lobes of the lung.
An animal was
con­
sidered free fro
infestation if no adult lungwr
this dissection.
Several specimens of l\lllgl«)rms were taken from the
lungs of po.sit!Te cases.
were revealed by
These were brought to the latoratory where
a nWiber were preserv-ed in 10 per cent formalin and submitted to
Dr. L. A. Spindler of the Zoological Division of the United States
id.~tification.
Department of Agriculture for
used
The remainder were
to increase the nuaber of lungworm larv-ae present in tb:! earth­
woras later
ployed in the inoculation of experimental animals.
Discussion
A total of .518 pigs were exanined post-morte
of lungwonna.
were negatin.
for the presence
Of these, 269 (51.9 per cent) were positive and 249
Table I reveals the incidence of infestation sholllll by
this survey.
Among the animals examined were 20 slaughter-weight animals
(19Q-240 pounds) from the College swine herd.
of 65 per cent was observ-ed in this group.
1 lungworm incidence
Thirt.y-nine pigs raised
by children in 4-H clubs slso were examined md an incidence of
,58.97 per cent revealed. These ani.Jial.s asauae particUlar signifi­
cmce inaem.uch as it may be assuaed that aanagemert. of these animals
adhered cl.oaely to
reco~~~Dended
standards.
Saaples were collected over a period of eight months.
A decrease
1n the incidence of infestation was noticed in the late months:
it is
ll
Table I
The Iacid.enc.e of
»._~.
Eula2necl
SOurce
2• 2...Sl
CUatoll Wl*
z-t..:n
~l.
2-l~
?~7..;,Sl
8-3-Sl
e-:n~
~51
~.31..:51
9-,..:n
9-14- Sl
9-21-.51
9-26-Sl
23
1.2
1t
4-2o;.:Sl
4- 2.3-51
•tt
l.\lilgWO
•
o• s. c.
Cutoa W1
•.
4~
8
JO
22
TOtALS
...
8
4
2
65..2
66..6
27
1
19
;s.a
ss
45
ss.o
2S
1.6
9
.)5
2l
28
1
20
20
46
68
l«l
4~
ll
8
6
13
Per ceilt ol
We nation
75.0
6.5.-0
66
•
•
1S
uaber
egatift
1
14
4-1
CUatoa kU1
Inteetation in Oregon SWine
Sll
u
u
l3
SO•O
6.5~0
at
40
'
se~. o
so;o
'
31
&f.~O
46.9
4.?
16
1.2
57~1
...12...
...JL
22. 2
2111
249
51.,
*fhe teeM ttCuatoa Jdll• nter:a to swiM broUght to t.h.e
ela'Qgbt-erhouae to be Jd.lled • dheMfi arul retumfJCl to
the tanner tor h1a owa cOileumpt,.ion..
preallled that tbia <laUDe vaa due in part
to th• lcmg periods or
drought in wbich paa\.ure aoll vu hard and roo-ting 41.courage.d.
o.t' aftectecl u\aals showed eo•i.c.terable variat10D rangmg ti'O
waa the
pre~c•
ot nbpleural petechiae..
L\algl
groul)r
_,re severe illt..tatioaa
ebowed lobular itnelveaent., part1cularl¥ in the baMl ana of the dia­
phragut.ic lobe.
r.age
These le:aione exhibited the cbar'acteriet1c
fro . priu.r7
:1n.f'l.a1:lraation to reaolutlorl.
pn~c
12
The incicienc'e ot lllngl«)rm infestation in oregon swine, as re­
vealed by this surve;y was 51.9 per cent.
of 518 pigs examined.
Parasites were found in 269
13
!HE CORRELATION BETWEEN LUNGWORM INFESTATI·ON AND THE
ECONOMICS OF PORK PBODUCTI<JI
Spindl.er feels that the small amount of quantitative inforaation
available regarding the extent to Which parasites can inhibit the
growth of pigs, coupled with the misaing element or contrast in aub­
lethal farm infestation, where all or nearly all animals are atfected,
are primarily responsible for the failure of swine raisera to appre­
ciate the injuriousness or parasitic diseases (14, p.426).
<:he
ot the main objectives of this paper
waa
to determine the
correlation between lungworm infestation and the economics of pork
~
production.
To do this, it was necessary to raise pigs tree
worms, and to minim:! ze or eliminate other nematode paraa:ites.
ot lungIt was
al.ao necessary to control the degree of infestation of experiaental
animals by developing suitable infectious material.
Teclmiquea involved in raising the experimental animal a, in in­
creasing the infectivity of the intermediate hoat, and in detel'llining
the degree of infestation in both the intermediate and definitive
boats are described.
Material and Metboda
F.xperilllental Aniula
All an:lma) a used in these trials were raised under conditions de­
signed to prevent natural inteatation by nematodes.
Three purebred
Berkshire aows, all bred to the same boar, were transported fl"'lll the
14
swine bam to the veterinary barn in accordance with the McLean County
qstem ot parasite control.
These sows were placed in separate ceaent­
fioored, box stalls a week prior to the expected farrowing date.
deep straw Utter was used for bedding.
A
All aovs farrowed within a
three-day period, each giving birth to nine live young.
All piglets
were weighed, earmarked and the:tr navels treated with tincture of
iodine.
In the abaence
ot a brooder, heat lampe were suspended in the
center ot each stall tbree teet trom the noor.
Guard ralls of tw
by eight-inch timbers wre placed aro UDd the eircumtercce
stalls ten inches from the fioor t.o prevent the
crushing the young.
time.
BOWS
ot the
from lying
OD
anQ
Only one pig died between farrowing and weaning
The pregnant and nursing sows were aaintai.ned on a ration, the
coapoaiticn of which is ahown in Table U.
Table II
Pregnant and Nursing Sow Diet
Per cent
Ingredients
Barley
Oats
Alfalfa aeal
Tankage
So7bean meal
Linseed aal
Bone ~~~eal
IJ.aeatone
Iodized salt
62.0
16.0
s.s
6.0
4.0
2.0
o.6
o.s
0.4
At three and one-halt weeks ot age all animals were bled troa the
anterior vena cava and the he110globin levels (Spencer Hetb:>d) deter­
mined.
As was expected
ot pigs raised on cement, the hemoglobin level
15
was low (see 'l'abJ.e V).
Six pigs lere found to be definitely anemic.
Treatment was initiated using tw ounces of ferrous sulphate and one­
half' ounce o! copper sulf te suspended in 500 ml. of bla.ckstra.p UXllaa­
s s.
This mixture w s painted upon sections of rubber
to the guard rails.
This method was 1b tnd to be
nnertube nailed
!'fecti ve and prefer­
able to the older sy-stem of painting the sow's udder.
At one liiOnth
or
age, all ale piglets were castrated and three
trial groups o! eight were established.
An aniliBl w a sacrificed and
examined poat-1110rt.em !or evidences of parasitism; none was !olD'ld.
Group A was designated as the control and was composed of tour
males and tour famales.
These eight pigs had a total weight of 151.7
pounds.
Group B, the Jll)derately infested group, bad a total weight of
151.3
pounds ani was composed of tiYe males and three females.
Group
c,
the heaYily infested group, had a total weight of 151.2
poUDda and included ti ve males and three females.
Two anemic pigs were included in each of the three experimental
groups.
ancl
All groupe were composed of three pigs from each of tw aowa
two froa the third.
lntectious material was given per orua at
weekl.7 intervals tor
eight weeks CCNEencing at the fourth week of age.
weaned at six weeks.
All pigs were
Following weaning the experi.J!Iental animals were
uintainecl on a ration, the composition of vhich is shown in Table
In addition to the dey feed, a <iail.y milk a.1pplement vas given.
ll1l.k was fed during the six-week post-farrowing period.
For the
m.
Whol.e
16
remainder of
t~
to each group.
trial, three pounds of reconstituted. skim milk was fed
The animals were protected against hog cholera by vac­
cina.ting with ROVAC (Lederle).
Table i l l
Growing and Fattening Pig Diet
Ingredients
Per cent
39~0
Com
Oat a
Ali'a.lfa meal
39~0
s.s
Tankage
6~0
So7bean meal
4.0
2. 0
Linseed meal
o•6
o•.s
o.4
Bone meal
Limestone
Iodi~ed
salt.
Infectious lfaterial
.Source of infectious matet'1al.
Earthworms were obtained from the
*>il surrounding the hog holding shecls of the John .Abbe Slaughter
Company
of Corvallia.t Oregon.
This location was selected
soil was knolm to be an ideal habitat tor earthworms.
be~ause
the
It was believed
that most earthworms found in this locallty would harbor· swine lwg­
worm larvae.
A total of about 2,500 earthl!IOnas were precured.
All
were pigmented.,. the body being conspicuously ringed with bmds ot
purple or reddish bro1m contrasting with nearly colorless interseg­
mental areas.
served.
A variation in length between 60 and 130 ma. was
Several spec-imens were identified by Dorothy McKey
ob­
Fender~
Entomologist at Linfield College, McMinnville, Oregon as Eiscia
17
foetida (Plate 1 in Appendix).
Schwartz and Portel" (9, p.4.30) atate
that thie species appears to be tte most. suitable intermediate host. of
t.he swine ltmgWOrm.
All worms originally obtained were placed. in a
wooden container' filled with e. mixture of soil, mEilure and sawdust.
'lhe soU surface of the box was covered at all tiJAes with several
layers of 1110ist paper towels to prevent dehy'dration.
Technique
used to determine the degree of infectirl.ty of_,_ the­
.
eartb•ft)l"llB.
Several specimens of the earthlft)rma used in this experi­
ment were exudned
to <ietermine it they harbored swine lnng1110rm larTae
(Plate 2 in Appendix).
Earthwo-rms were anesthetized accord:ing to the method recoiDJlendec:l
by Macnab and FencieF (.3,
all adhering debris.
p.97). The
worms were first washed to remove
They were then placed in a petri dish containing
sufficient tap water to cover thea.
Ninety-tive per cent alcohol was
added, a cubic cent.illeter at a time•
With each addition of alcohol,
the li'Orms exhibited convulsive
Subsequent additions
or
I~Dvements
which lasted a sbort t.ime.
alcohol were made upon recovery.
When com­
plete anaesthesia wa-s reached, the worm f'aUed to retponci to extemal
stimuli and. w-as transferred to a dissecting tray.
!he liiDrm waa grasped
by the tail with thumb forceps and shaken until it extended t .o ita rull
length.
It was pinned to the dissecting t .ray in a natural position and
a mid-line l.ongitucHnal inci.ai.on was mad:e through the dorswa1 extcdillg
troaa the first to about the se"VeDteenth SOIIite. A cliase:cting micro­
acope facilitated the remoYal. of the anterior portion of the a1 iaaenta.ry
18
canal and the adhering portions or the circulator.r system.
terial vaa
trans~erred
This
Jl&­
to an ordinary glass slide and teasing needles
were used to aeparate the tissues.
A cover glass was place<l over the
tissues and microscopic larvae counts were made.
The use ot wide
field lOX oculars and the low power (lOX) objectiYe wu found .,st,
conwnient tor making quantitative larvae counta.
Early examjnations were exploratory in nature and served only to
show that all earthworms contained larvae.
QuantitatiYe counts were
made only atter ·t he intecti'rlty ot the interaed.iate host vas increased.
This was accomplished by adding large nl.lld:>ers
ot lungworm eggs
aoil containing the experimental eart.tnlorma.
Eggs were obtained by
mincing adult lungwoms, procured fro
to tbe
the lungs of freshly killed
bogs, in a petri di. 8h containing saline solution.
Quantitative counts ot 27 earthliiOrma totalled 4743 larvae or an
average of 175.5 larvae per worm.
This average contplres favorably
with that of 26 earthworms examined b7 Schwartz and Porter (7 1 p.4,30)
where an average of 161 larvae per worm was found.
Guinea Pig Infestation Trials
Experiaental infestation of guinea pigs was attempted in an ef­
fort to dete.rmine the ability of t.he l\Ulgwona larvae to inYade body
tissues.
Ckl August. 1 1 1951, three guinea pigs, weighing between 200 and
250 grams, were fed the anterior portions of three earthliiOraa.
!he
exposed anillals were then kept under obsenation tor the appearance
19
of pneumonic or other aymptome associated with lungmrm infestation.
en
No untoward symptoms were observed.
September 1, 1951, the exposed
guinea pigs were sacrificed and the lunge and trachea removed and exa­
Jiined.
Careful dissection of these organs failed to reveal the pree­
ence of parasites.
ExperilBltal Infestation
ot
Swine 'With Lunponaa
Initial doses of earthliiOrms were given the individual members
ot
the moderate and heavily infested groups on Saturday, September 22.
1951. Subsequent doses were given each Saturdq until a total of
eight doses had been administered.
Whole earthworms or their anterior
portions were placed in amall gelatin capsules, lubricated with min­
eral oU, and administered oral.ly with the aid of a mouth specullDI.
Each of the members of the moderately infested group received three
earthwl'lls a week, until a total of 24 eart.h_,rma was admini.atered.
The eight pigs compri8ing the heavily infested group were subdivided
into tour groups of two pigs each.
lndi'ri.iiual aembers received a
total of 40 1 80 1 200 and 400 earthworms respectivel.7.
The earmark, dam nUIIIber, sex, birt.hweight and hemoglobin levels
ot the piglets comprleing the various groups as well as the nl.Uilber of
earthworas givm aa a weekly dose and the total number of earthwol"JJ8
administered is given in Table IV.
the piglets were one
The initial dose was givm when
nth of age and continued at weekly intenals
until a total of eigtt doses was administered.
20
Table IV
statist.ical Record of Experimental Piglets
Pig number Dam nuaber
Sex
Birtht'leight
pounds
Hemoglobin
p ./100
Earthworms
ml. weekly dose total
Experiamtal Control Group
216
220
225
228
230
2.32
2.34
237
5o-63
50-6.3
49-137
49-137
49-137
47-.38
47-38
47-.38
H
3.9
.3 .1
3.6
3.5
.3.9
4.0
M
.3.6
F
3. 7
H
F
M
F
F
7.9
6.1
6.3
5.8
8.3
9.4
10.5
7.0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
)bderately Infested Experiaental Group
213
218
219
226
22!1
2.33
235
2.36
50..6.3
So-6.3
5o-6.3
49-137
49-137
47-38
47-38
47-.38
M
M
F
F
F
M
M
M
3.4
2.8
4.2
4.0
.3 . 8
3•.3
3.6
3.4
6•.3
5.8
6.7
3
.3
8.4
.3
3
24
24
.3
.3
24
24
24
5
5
10
10
25
25
40
40
5.9
9~6
9.6
9.3
.3
3
24
24
24
Heavily Infested Experiaental Group
214
217
221
22.3
224
2.31
2.38
239
so-63
50-63
50-63
49-137
49-137
47-.38
47-.38
47-38
M
H
F
M
M
K
F
r
.3~5
3~1
.3.1
4.4
2.85
.3.7
.3.5
.3.0
7.6
8.4
8.0
6~1
5.2
9.4
9.1
9.4
50
50
80
80
200
200
400
400
Weekly records of weight gains and dail.7 records of .teecl conau.p­
t1on were kept. in an effort to determine what effect, i t &1171 11.BlgWora
infestation had on the growth and teed utilization of the a1'fected.
21
Figures 1, 2 and 3 record the average weight gains ot the pigs
pigs.
within each group at weekly intervale.
The ratio of teed used to produce a pound of pork varied between
a high of 3.55 to 1 and a low ot 3.40 to 1.
The most efficient utili­
zation ot teed was seen in the experimental control group (3.40 to 1).
The teed conversion ratios of pigs in both the mderatal.;y and heavil.7
intested experimental groups were almost identical, being 3.55 to 1
and 3.54 to 1 respectively.
Inaamuch as all of the teed conversion
ratios obtained in these trials are well within the normal range, no
significance is attached to the variations that exiat among the
groups.
Following the attempted experiaental infestation, all animals
were observed tor syaptoms associated with lung"NDrm infestation.
earliest and most
COJIIIIOD &y~~ptom
The
seen was a cough, accompanied in
severe casea by difficult respiration.
Confirmation of infestation
was •de by finding lungworm eggs in the feces of the exposed piga.
Schwart.z and Alicata ( 7, p.40) record the finding of lungworm eggs in
the tecea aa early as 24 days following experiaental exposure.
Eggs
were first seen in this investigation 28 days following the initial
administration of the intest.ed earth1110ras.
The max1aua mlllber of eggs
was shed during the titth week following exposure.
Periodic fecal
exudnat1ons showed a tendency tor egg passage to decrease atter the
titth week.
Post-mortem examinations were made ot the two pigs that died as a
result of the heavy lungworm intestation.
In both cases death was
22
WEIGHT
AVERAGE
OF
AGE
CONTROL
IN
WEEKS
Figure 1
GROUP
PIGS
2.3
--·---- ----------------,
. - - - - - - - - - - - - - - -·--WEIGHT
AVERAGE
OF
MODERATELY
INFESTED
PIGS
50
40
30
20
10
oL-_L__L-~--~~---L--L--L--~~--~~-~~~~~~~-~-i
4
5
6
7
8
8
10
AGE
II
1Z
IN
13
WEEKS
Figure 2
14
15
16
17
II
18
2fl
21
24
WEIGHT
AVERAGE
OF
AGE
HEAVILY
IN
WEEKS
Figure
3
INFESTED
PIGS
25
ascribed to a verminous
~elU!¥)nia.
Following is a description o£ these
animals and the affected tissues.
Pig number 2.38 died at lJ weeks of age, after receiving a total
of 400 earthworms.
Its weight at this time was 48.5 pounds.
All or­
gans in the abdominal cavity appeared normal with the exception of the
liver.
A .oderate scarring of this organ was observed.
The thoracic
cavity was opened and the trachea, lungs and heart were removed.
The
atrio-ventricular valves of the heart were slightly thickened, Dugges­
ting a tendency toward vegetative endocarditis.
The lungs showed an
extr e vem!noua pneUI:lOnia ldth an extensive metaatrongylus infesta­
tion.
The parasites were too nu.eroua to cotmt.
The lungs exhibited
definite marbling, accompanied by edema and moderate fibrosis, were
tim and lacked elasticity.
'the trachea, bronchi and smaller bron­
chioles contained an edematous exudate.
Scattered pneumonic lobules
were present especially along the basal edge of the diaphragmatic lobe
and in the right apical lobe.
Pneumatic areas involved three to five
contiguous lobules and exhibited both red and grey hepatization.
Scattered lobules presented a fi.
atelectatic appearance of recent
pneumonic processes.
Pig number 224 was the smallest in ita litter, weighing 2.85
pound when farrowed.
200 eart.hwrm.s.
'nlia heavily infested pig received a total of
It was found dead in its pen at 13~ weeks
Its weight at tbis time was 30.25 potmds.
or
age.
The organs in the abdoJiinal
cavit.y were normal in gross appearance with the exception of the liver
where a slight scarring vas observed.
A longitudinal incision made
26
throughout the l«lgth of the 8ttiBll intestines failed to reveal the
preseiM:e of ascarids.
Parasite eggs, other thm those of swine ltmg­
¥:>rm, were not found on
r ecal
examination.
'l'he thorax was opened and
the trachea, lungs and heart were removed in toto.
pneumonia was present (Plate 3 in Appendix).
pleural petechiae.
A severe vel"'llinoue
The lung revealed sub­
Scattered pneumonic lobules were present and ex­
hibited both red ana grey hepatization.
Moderate fibrosis of the lung
as well as scattered. atelecatic areas were observed.
Lungwol"'Bl8 were
extreael7 numerous and were estimated to total about 7000 (Plate 4 in
Appendix).
The following technique was employed in this approx:i.D&tion:
para­
sites were carefully removed fran the right Bide of the lung and placed
in a beaker containing 1000 Ill. of saline solution.
parasite mixture was agitated
'l'he saline­
am three 50 111..-samples were transferred
to petri di llhes for counting.
per 50 ml. of saline solution.
An
average ot 175 parasitea · was found
This figure was multiplied by 20 in
order to approximate the ntBBber ot lungworm& in the original 1000 Ill.
of sallne.
The total parasite count was then multiplied by two be­
cause specimals were obtained trom only the right. side of the lungs.
The degree of lungworm infestation in the experi.m.ental. aniuls is
recorded in Table V.
The tissues examined were obtained from the
killing noar af the loeal slaughterhouse.
marheted for human consumption.
All of these pigs were
27
Table V
Degree of Lungworm Intestation in Experimental Pigs
Pig umber
Slaughterhouse
Date
Weight
lba.
Degree of
Infestation*
Experi.maltal Control Group
216
220
225
228
230
232
234
237
John Abbe
steen Brothers
)bnroe Street
Monroe Street
~nroe
stnet
steen Brothers
Steen Brothers
Stee Brothers
l-28-52
2-11-~2
2-25-52
2-25-52
2-25-52
2-ll-52
2-11-52
2-11-52
185
194
195
200
144
180
197
195
light.
light
negative
negatiYe
negatiw
negative
negativ.
negative
lbderately Infested Experimental Group
213
218
219
Monroe Street
lbnroe street
:tbnroe Street
226
Monroe Street
Monroe Street
Monroe Street.
Jfmlroe Street
Steen Brothers
229
233
235
236
2-11-52
2-ll-52
2-ll-52
2-ll-52
2-25-52
2-25-52
2-11-52
2-ll-52
182
188
208
186
180
IIOderate
moderate
moderate
moderate
hea.,.
200
light
187
190
moderate
heav,y
Heavily Infested Experimental Group
214
217
221.
223
224
2.31
238
239
1-28-52
2-ll-52
Steen Brothers
2-ll-52
steen Brothers
2-ll-52
died during trial ll-18-51
Steen Brothers
2-11-52
died during trial ll-17-51
Monroe street
2-25-52
John Abbe
Steen Brothers
*tlo. of 1unglll0raa
observed.
0
0-10
1~100
lOQ-1000
1000 or above
185
191
175
181
30
181
48
180
Classification
negative infestation
light infestation
moderate infestation
heaYT infestation
extreme infestation
light
heavy
moderate
moderate
extreme
he
a..,.
extNIII8
heav,y
Discussicm
The death of two members of the heavily infested group, to which
extremely large n.umbers of parasitized earthworms (200 a.nd. 400) were
administered, indicates that lethal infestations occur.
The remainder of the heavily infested pigs, together with the
moderately infested animals, showed a sublethal syndrome characterized
by coughing and occasional difficult respiration.
It will be noted that two of the control anim.a:Ls showed a light
lungworm infestation on post-mortem examination ('fable V).
Since in­
fested earthworms were not administered to any member of the control
group, t18 mode of infestation cannot be positively <ietermined.
Dur­
ing the first two weeks of these trials, bowever, tbe suckling pigs
were kept with their sows, il"respectiYe ot whether they received.
tested material or not..
in~
It is thought that one of the infested pig­
lets regurgitated one or more earthworms, wich were then ingested by
the
two affected members of tbe control group. The cement noors and
curbs in the stalls housing the experimental animal.s min:brd ze the
possibility of non-experimental earthworms gaining acceas to the pens.
Weekly weight averages of the members of the three experimental
groups are shown in graphic form {Figures 1, 2 and .3).
these figures
that
J:llq' be
fai~ed
Comparison of
to re:veal a significant deviation in any group
attributed to lungworm infestation.
It is apparent that
the growth rate o.f all groups was depressed between the twelfth and
thirteenth week and again between the twentiet.h and twenty-first week.
This inhibitory effect was believed to be due primarily to the increa­
sed area required by the growing pigs.
This condition corrected it­
self when the groups were further subdivided and fewer pigs allotted to
each box stall.
Additional evidence of the mtifonnity of all experi­
mental groups is obtained by noting the similarity of carcasses at the
ti.Jne of slaughter (See Plate 5~ 6 and 7 1n Appendix) •
The most efficient utilization of feed was made by the experimen­
tal control group (3.40 to 1).
Feed conversion ratios of the moderat­
ly and heavily infested experimental groups were almost identical,
between 3.55 to 1 and 3.54 to 1 respectively.
No significance is at­
tached to this variation.
From these observations it may be concluded that mderate lung­
worm infestation in swine are not essentially detri.JEntal. to the de­
finitive host.
Similar conclusions have been drawn regarding the
pathog.U.city ot lungworm infestation in the other species of doMstic
aniula.
In his work with abeep, Shaw (10, pp.6-7) waa able to pro­
duce experimental lungworm infestation in all but tw of the 27 laaba
where infestation was attempted.
In thia group o! infested animals no
untoward spsptom could be observed with the exception of a moderate
cough.
Tqlor, in a discussion of lungworm infestation o£ cattle (15,
p. 703), sUIUI&J'izes hie observations in the following quotation:
"According to the modem teaching• o! paraaitology, the nematode
W01'118
concerned in these diseases are not to be regarded as essential.l.T
pathogenic but as able to live in their hosts without giving rise to
an)" systemic disturbances ao long as the)" are present in reasonable
30
nuabera.
What these reasonable nUIIbera might be varlea eonaiderabl7
vitb the species of wora concerned, btt. in several instances it ia a
ll&tter of thousands and in some of tens of thousands."
Lungworm eggs were first observecl in the feces ot experimentally
infested piga 28 dqs following exposure; maxiiiU1D numbers being passed
during the fifth week.
A continuous decliDe in the nuaber ot eggs
produced was observed from this tiae on.
Schwart.z ( 6, pp.3-4) reports
tla t lun&1«)1'11l8 that gain access to young 8N'ine mq
the lungs or otherwise disposed ot.
be eliminated
t~a
If the parasite continues to liYe
in the definitive host., a reduction in the nUIIber of eggs produced
occurs.
These tindinga suggest that swine lungwo:raa are aelt-l.1aiting
and that continued re-intestation is essential
paraaiti...
tor prolonged
31
1.
Naturally occurring swine lungworm larvae were 4ernonetre.ted in the
COJIIIIOn
.2~
manure wcr m, Eisenia foetida •
Artificial lungworm infestation was pmdueed by feeding earth1110rma
containing swine lungworm larvae to susceptible pigs.
3. Extreme lungworm infestation in young pigs resulted in a venainous
pneUIIIOnia that
te~nated
fatally.
4. !bderate or sublethal lungworm infestation seldom produced aD7
pathologic syndrome other than a moderate cough.
5. Th.e time necessary to produce marketable hogs was not lengthened
b)r swine lungworm in.t estation.
6. No significant differences were seen when a comparieon of the cal"­
caaaes of the Yarious experiment&l groups were made.
·• .
32
BIBLIOGRAPHY
1.
Kates, K. c. ObaerYations on the viability ot eggs of lungwo:rms
of swine. Joumal of parasitology 27: 265.-272. 1941.
2.
Macnab, James A. am D. McKey Fender. An introduction to Oregon
earthworms with additions to the Washington list..
lorthwest science 21:69-75. May, 1947.
3.
earthworm
4. M6nn1g,
anato~.
Aida to the teaching aid atwiy of
Turtox news 24:97-99. 1946.
H. o. Veterinary helminthology and entomology.
Bailllere, Tindall am Cox 209-213. 1934.
5. Jobrgan, B. B. and P. A. Hawkins .
Minneapolis, Burgess, 1949.
London,
Veteri.M.ey helmintholog.
177-lSO.
6. Schwartz, Benjamin A. Controlling lungworss of swine, Washington,
United. states departmmt of agr1culture 1 1936. 5p.
(United States department ot agriculture leaflet 118).
7.
Schwartz, Benjamin A. and Joseph E. Alicata. Life history of
l'\&lgWOnlB parasitic in adne. Washington, thited St.ates
depart112nt of agriculture, 1934. 41P• (United States
depart.ment of agriculture technical bulletin 456).
Abstract. The developaent' ot
Metastrongylus elongatus and. !!!,:. pudendotectus 1n their
inter.diate hosts. Journal of paraaitoloa 16:105.
1929.
8.
9. Schwartz, Benjamin A. and Dale A. Porter. The localization of
swine lungwra larTae in the earthvora, HelodrUua
toetidua. Livro Jubil.ar Prof. Travaseos. Rio de
Janerio, Brasil ni. pp.429-440. 19.38.
10.
Shaw, James N. L\Blgworma (Dictzocaulua Filaria Rudolphi) in
sheep and goats. Co:rvallis, Oregon state college, 1934.
l2p. (Oregon. Agricultural experiJiant station. Station
bulletin no. 327) •
11.
Shope,
12.
SpincUer, L. A. The incidence of worm parasites in swine 1n our
aouthem states. Proceedings ot helminthological aociet:,y
ot Washington 1:40-42. 19.34.
a.
E. An intermediate host tor the tndne influenza v1rua.
Science 89:441-442. 19.39.
3.3
13.
eart.hworas.
Waetlington.
1.4.
of pig a.
Persistence of swine lungworma in
Proceedings of helminthologieal society of
5:63. 1938.
Effect of parasites on the growth
Veterinary medicine 46:421-427. 1951.
15. Taylor 1 E. L. Further notes on husk.
63:703-706. 1951.
The veterinary record
APPENDIX
34
Plate 1 - The Comm:>n Manure vlonn, Eisenia foetida (2X)
35
Plate 2 - Swine Lungworm Larvae ( 70X)
36
Plate 3 - Verminous Pneumonia -- Hog Lung
37
Plate 4 - Swine Lung'WO:rm (2X)
Plate 5 - Carcasses of Control Group Pigs
Plate 6 - Carcasses of MOderately Infested Pigs
Plate 7 - Carcasses of Heavily Infested Pigs