Intraspecific differences between cottontail and woodchuck isolates of the trichostrongylid nematode
Obeliscoides cuniculi (Graybill)
by Nelson Samuel
A thesis submitted to the Graduate Faculty in partial fulfillment of the requirements for the degree of
MASTER OF SCIENCE in Zoology
Montana State University
© Copyright by Nelson Samuel (1970)
Abstract:
The investigations reported in this paper were Undertaken to determine whether isolates of
Obeliscoides cuniculi from the southern woodchuck (Marmota monax monax) and the eastern
cottontail rabbit (Sylvilagus floridanus mearnsi) are identical or two distinct strains. Infections were
induced in laboratory rabbits by oral inoculation of 3,000 infective larvae of woodchuck and cottontail
origin. In the first experiment, the course of the infection was studied in two 5-animal groups, by
following fecal egg counts twice weekly during a 5 month period. The second experiment comprised
two groups, each containing 6 animals, all of which were necropsied 28 days postinoculation.
The prepatent period averaged about 17 days in the woodchuck strain and 15 days in the cottontail
strain. Worm egg output by the cottontail strain was much higher than in the woodchuck strain. The
cottontail strain exhibited 2 peaks before egg production decreased from the maximum to a low level.
In two rabbits the woodchuck strain also showed a second peak. At 161 days postinoculation, the
average number of cottontail strain eggs passed in a 24-hour period was 17,931, compared with 2,998
in the woodchuck strain.
More worms were recovered at necropsy from rabbits infected with the cottontail strain than from
rabbits infected with the woodchuck strain. The female-to-male ratio in the cottontail strain was 1:1.3
at 28 days and 1:2.03 on day 168 postinoculation. A similar sex ratio was obtained in the woodchuck
strain.
The associated pathological changes were primarily those of gastritis, the mucosa being studded with
petechial haemorrhages in small localized areas, edematous fundic rugae, and a few areas of ulceration.
Histological studies revealed that the woodchuck strain in some instances produced the most severe
lesions. In older infections a few crateriform ulcers were more common in rabbits infected with the
woodchuck strain than in the cottontail strain.
Measurements of adult Obeliscoides cuniculi of both strains showed significant differences (P<0.01) in
length of body, esophagus, spicules, and in the distance from anterior end to vulvar region.
Retardation of the parasite at the fourth stage was the most consistent phenomenon observed in rabbits
infected with the cottontail strain. The inhibited larvae remained in the mucosa as long as 225 days.
In accordance with the above findings, it is concluded that 0. cuniculi isolates of woodchuck and the
cottontail origin which were used in this study represent distinct strains having a number of unique
physiological and morphological characteristics. S t a t e m e n t o f P e r m i s s i o n t o Copy
In p re se n tin g th is
th e sis
in p a r tia l
f u l f i l l m e n t o f th e r e q u ir e ­
m en ts f o r an a d v a n c e d d e g r e e a t M o n tan a S t a t e U n i v e r s i t y , I a g r e e t h a t
t h e L i b r a r y s h a l l make i t
fre e ly a v a ila b le fo r in sp e c tio n .
a g re e t h a t p e r m is s io n f o r e x t e n s i v e co p y in g o f t h i s
th e s is fo r sc h o la rly
p u r p o s e s may b e g r a n t e d b y my m a j o r p r o f e s s o r , o r , i n h i s
th e D ire c to r o f L i b r a r i e s .
p u b lic a tio n of th is
th e sis
It is
I fu rth e r
a b s e n c e , by
u n d e r s to o d t h a t any c o p y in g o r
f o r f i n a n c i a l g a in s h a l l n o t b e allo w ed
w i t h o u t my w r i t t e n p e r m i s s i o n .
S ig n a tu re
D a te
.
/9 7 /).
INTRASPECIFIC DIFFERENCES -BETWEEN COTTONTAIL AND WOODCHUCK
ISOLATES OF THE TRICHOSTRONGYLID NEMATODE
OBELISCOIDES 'CUNICULI ,(GRAYSILL)
by
NELSON SAMUEL
A t h e s i s s u b m i t t e d ■t o t h e G r a d u a t e F a c u l t y i n p a r t i a l
f u l f i l l m e n t ,of t h e r e q u i r e m e n t s f o r t h e d e g r e e
of
MASTER OF SCIENCE •
in ■
Z o o lo g y
fed:
H ead, M ajo r D e p a rtm e n t
" C h a irm a n , E x a m i n i n g Comm^xtee
G r a d u a t e D ean .
MONTANA STATE UNIVERSITY
B o z e m a n , M o n ta n a
A u g u s t , 1970
iii
ACKNOWLEDGMENTS
They a u t h o r e x p r e s s e s , h i s s i n c e r e , g r a t i t u d e t o D r . D a v i d E.
W o r l e y , f o r a d v i c e , g u i d a n c e a n d e n c o u r a g e m e n t d u r i n g the> c o u r s e
o f t h i s ■s t u d y .
Thphks a r e a l s o e x te n d e d t o :
D r.
C. K. A n d e r s o n
f o r e x a m i n i n g t h e s t o m a c h t i s s u e s ; Mr. D o n a l d . F r i t t s , f o r p h o t o ­
m ic r o g r a p h s ; D r. E. P .
S m i t h ; f o r •,a s s i s t a n c e w i t h t h e s t a t i s t i c a l •
a n a l y s e s ; M r. R i c h a r d H. J a c o b s o n , f o r t e c h n i c a l a s s i s t a n c e a n d
enco u rag em en t th ro u g h o u t t h i s
i n v e s t i g a t i o n ; ,M r s . K a t h e r i n e K.'
S fcitet# f o r - r e a d i n g t h e m a n u s c r i p t ;
fo r h e r h elp in .ty p in g
a n d fco m y , f r i e n d , R o b e r t a A l l e n ,
the, f i n a l d r a f t o f t h i s p a p e r .
S p e c i a l t h a n k s a r e e x t e n d e d to. t h e B o a rd o f M i s s i o n s o f t h e
U n i t e d M e t h o d i s t C h u r c h , New Y o r k , f o r t h e g r a n t o f t h e C r u s a d e
S c h o l a r s h i p , w h ich e n a b le d t h e . c o m p le tio n o f - t h i s . s t u d y . • A p p re c i­
a t i o n is . a l s o e x p r e s s e d to t h e I n t e r n a t i o n a l I n s t i t u t e o f E d u c a tio n
o f t h e U n i t e d N a t i o n s f o r s p o n s o r i n g a . summer s t u d y p ro g r a m m e ' .at '
M ich ig an S t a t e U n i v e r s i t y .
iv
TABLE 0F CONTENTS
Page
I
VITA .
.
.
.
. .
.
ACKNOWLEDGMENTS ■" .
.
.
.
.
.
......................................... ...
r
ii '
. , .......................... •....................... .....
iii.
LIST OF TABLES, ..........................................................................
LIS T OF FIGURES-. .
. . . .
.
ABSTRACT .
, .
!.
.
introduction
.
.
.
. .
.
. .
. .
.
.. .
v
..
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. .
. :
. ,
..................................
vi
v ii
......,............i......
I.
MATERIALS AND METHODS
6
RESULTS '
10
Worm e g g o u t p u t ; i n f e c e s
. . . . . .. .
....
. . . ,. . .
IQ
Worm..s e x ^ r a t i o s . . .. . . . . .................................................................................12
D i s t r i b u t i o n - o f -worms i n t h e s t o m a c h . . . . . . . . . . .
12
P a th o g e n ic ity . . . . . . .
. . . . . ....
.. .
. . . . • •
12.
S t a t i s t i c a l a n a ly se s
. .. . ; . . . . . . . .
. . . -. . . . .
23
DISCUSSION .
.
. . . . . . . . . . . . . . . . . . . . . . . . .
H i s t o t r o p i c .'fo rm s
LITERATURE CITED .
.,
25
., ...................................
. . . . .
.
. .
28
. ,. .
..
.
. .
. . ,
.
31
V
LIST ,OF TABLES
Page
T a b le
i:
II.
I ll;
C o m p a r a t i v e r e c o v e r y o f - (9. auniout^ l a r v a e ,a n d •a d u l t s o f
w oodchuck and c o t t o n t a i l s t r a i n s from -l a b o r a t o r y r a b b i t s
a t 168 d a y s . p o s t i n o c u l a t i o n . . . . . . . . . . . . .
...
13
C o m p a r a t i v e r e c o v e r y o f ©. ounicut-i; l a r v a e a n d a d u l t s .,of ■
w o odc huck- a p d c o t t o n t a i l . s t r a i n s f r o m l a b o r a t o r y r a b b i t s .
a t 28 d ay s . p o s t i n o c u l a t i o n
. . . . , . . . . . . -. . . . . .
14
M e a s u r e m e n t s o f QbelisoerLdes- euni'ouli l a r v a e a n d . a d u l t s •
d i r e c t l y from w oodchuck and a f t e r p a s s a g e i n l a b o r a t o r y '
r a b b i t s . . . . . ,. . ■......................................... . . . •
• . 24
vi
LIST OF FIGURES
F ig u re
I.
2 ,3 .
Page
A v e r a g e ■f e c a l e g g . c o u n t s o f . l a b o r a t o r y ' r a b b i t s e x p o s e d t o
3 , 0 0 0 l a r v a e o f 0. Qun-LeuZv.
P o i n t s •show n a r e .irtean. v a l u e s
f o r 4 -a n im a i gro u p s . . . . . . . . .
.............................................. .
11
C o m p arativ e ly m p h o c y tic i n f i l t r a t i o n s i n .g a s trie ..m u c o s a o f
r a b b i t s i n f e c t e d w i t h 0. eun-Leuti, o f t h e c o t t o n t a i l s t r a i n
(2) and t h e w oodchuck s t r a i n , (3) (2 8 -d a y i n f e c t i o n s ) .
A z u r e E o s i n a t e (A. E . ) x 1 2 5
16
4 . ■ E o s i n o p h i l s (E) s u r r o u n d i n g 0. cun-LeuZi l a r v a (L) o f t h e
c o t t o n t a i l s t r a i n .e m b e d d e d i n g a s t r i c m ucosa (2 8 -d ay
i n f e c t i o n ) . A. E. , x 380 ..................................................................................
5.
6.
C e l l u l a r d e b r i s ' i n t h e lu m e n o f g l a n d s (N) a n d e o s i n o p h i l s
(E) a r o u n d 0. cuyiiauZi l a r v a (L) o f t h e w o o d c h u c k s t r a i n
em bedded i n g a s t r i c m ucosa (2 8 -d a y i n f e c t i o n ) .
A. E. , x 425
................................................................................................................
17
C r a t e r i f orm m u c o s a l u l c e r w i t h c o a g u l a t i o n n e c r o s i s (C)
i n 1 6 8 - d a y r a b b i t i n f e c t i o n w i t h 0. oun-LcuZ-L' (w o o d c h u c k
stra in ).
A. E . , x - 1 0 0 ........................................................................
19
7.
An a r e a o f n e c r o s i s (N) i n t h e g a s t r i c m u c o s a .
A narrow .
f i s s u r e .(F) l e a d s f r o m t h e n e c r o t i c a r e a t o t h e . e p i t h e l i a l ■
s u r f a c e i n 1 6 8 - d a y r a b b i t i n f e c t i o n w i t h 0,- aun-teuZ-L (wood­
chuck s t r a i n ) .
A. E .,, x 1 6 0 ........................................................................19
8.
U n i f o r m f o c a l c e l l u l a r i n f i l t r a t i o n a n d em b e d d e d l a r v a
o f 0.- ounieuZv (w o o d c h u c k s t r a i n ) i n g a s t r i c m u c o s a o f
r a b b i t (168-day i n f e c t i o n ) .
A. E . , x 120
9.
17
(L)
C o n g e s t i o n (C) a n d h a e m o r r h a g e (H) b e l o w t h e m u s c u l a r i s
m u c o s a e (M) w i t h 0. oun-ieuZ-L (w o o d c h u c k s t r a i n ) l a r v a (L)
em bedded i n g a s t r i c m ucosa o f r a b b i t (2 8 -d ay i n f e c t i o n ) .
A. E . , x 95
21.
21
v ii
ABSTRACT
The i n v e s t i g a t i o n s r e p o r t e d i n t h i s p a p e r w e r e U n d e r t a k e n t o d e t e r ­
m i n e w h e t h e r i s o l a t e s o f Obel-Lsooides o u n io u ti f r o m t h e s o u t h e r n wood-r
c h u c k (Mavmota monax monax) a n d t h e e a s t e r n c o t t o n t a i l r a b b i t (S ylvild g u s
flo v id a n u s meaVnsi) a r e i d e n t i c a l o r tw o d i s t i n c t s t r a i n s . I n f e c t i o n s
w e re in d u c e d i n l a b o r a t o r y r a b b i t s by o r a l i n o c u l a t i o n o f 3 ,0 0 0 i n ­
f e c t i v e l a r v a e o f w oodchuck and c o t t o n t a i l o r i g i n .
In th e f i r s t e x p e ri­
m e n t , t h e c o u r s e o f t h e i n f e c t i o n w as s t u d i e d i n tw o 5 - a n i m a l g r o u p s , b y
f o l l o w i n g f e c a l e g g c o u n t s t w i c e w e e k l y d u r i n g a 5 m o n th p e r i o d .
The
s e c o n d e x p e r i m e n t c o m p r i s e d tw o g r o u p s , e a c h c o n t a i n i n g 6 a n i m a l s , a l l
o f w h ic h w e re n e c r o p s i e d 28 days p o s t i n o c u l a t i o n .
T he p r e p a t e n t p e r i o d a v e r a g e d a b o u t '1 7 d a y s i n t h e w o o d c h u c k s t r a i n
a n d 15 d a y s i n t h e c o t t o n t a i l s t r a i n .
Worm e g g o u t p u t b y t h e c o t t o n t a i l
s t r a i n w as much h i g h e r t h a n i n t h e w o o d c h u c k s t r a i n .
T he c o t t o n t a i l
s t r a i n e x h i b i t e d 2 p e a k s b e f o r e eg g p r o d u c t i o n d e c r e a s e d fro m t h e m ax i­
mum t o a low l e v e l .
I n tw o r a b b i t s t h e w o o d c h u c k s t r a i n a l s o s h o w e d a
second p eak .
A t 161 d a y s p o s t i n o c u l a t i o n , t h e a v e r a g e n u m b e r o f c o t t o n ­
t a i l s t r a i n e g g s p a s s e d i n a 2 4 - h o u r p e r i o d w as 1 7 , 9 3 1 , c o m p a r e d w i t h
2 ,9 9 8 i n th e w oodchuck s t r a i n .
M ore worms w e r e r e c o v e r e d a t n e c r o p s y f r o m r a b b i t s i n f e c t e d w i t h
t h e c o t t o n t a i l s t r a i n t h a n from r a b b i t s i n f e c t e d w i t h t h e w oodchuck
stra in .
T he f e m a l e - t o - m a l e r a t i o i n t h e c o t t o n t a i l s t r a i n w as 1 : 1 . 3 a t
28 d a y s a n d 1 : 2 . 0 3 on d ay 168 p o s t i n o c u l a t i o n .
A s i m i l a r s e x r a t i o was
o b ta in e d i n th e woodchuck s t r a i n .
T he a s s o c i a t e d p a t h o l o g i c a l c h a n g e s w e r e p r i m a r i l y t h o s e o f g a s t r i ­
t i s , t h e m ucosa b e in g s tu d d e d w ith p e t e c h i a l h ae m o rrh ag e s i n s m a ll l o c a l ­
i z e d a r e a s , e d e m a t o u s f u n d i c r u g a e , a n d a few a r e a s o f u l c e r a t i o n .
H i s t o l o g i c a l s t u d i e s r e v e a l e d t h a t t h e w o o d c h u c k s t r a i n i n some i n s t a n c e s
p ro d u c e d t h e m ost s e v e r e l e s i o n s .
I n o l d e r , i n f e c t i o n s a few c r a t e r i f o r m
u l c e r s w e r e m o re common i n r a b b i t s i n f e c t e d w i t h t h e w o o d c h u c k S t r a i n
th an i n th e c o t t o n t a i l s t r a i n .
M e a s u r e m e n t s o f a d u l t Obet-Lsooides o u n io u li o f b o t h s t r a i n s s h o w e d
s i g n i f i c a n t d i f f e r e n c e s (P < 0 .0 1 ) i n l e n g t h o f b o d y , e s o p h a g u s , s p i c u l e s ,
and i n t h e d i s t a n c e fro m a n t e r i o r en d t o v u l v a r r e g i o n .
R e t a r d a t i o n o f t h e p a r a s i t e a t t h e f o u r t h s t a g e w as t h e m o s t c o n ­
s i s t e n t phenom enon o b s e r v e d i n r a b b i t s i n f e c t e d w i t h t h e c o t t o n t a i l
stra in .
The i n h i b i t e d l a r v a e r e m a i n e d i n t h e m u c o s a a s l o n g a s 225 d a y s .
I n a c c o r d a n c e . w i t h t h e a b o v e f i n d i n g s , i t i s c o n c l u d e d t h a t 0.
o u n io u li i s o l a t e s o f w o o d c h u c k a n d t h e c o t t o n t a i l o r i g i n w h i c h w e r e u s e d
i n t h i s s tu d y r e p r e s e n t d i s t i n c t s t r a i n s h a v in g a num ber o f u n i q u e ■
p h y s i o l o g i c a l and m o rp h o lo g ic a l c h a r a c t e r i s t i c s .
INTRODUCTION
G ra y b ill
(1923) b a s e d h i s
o r i g i n a l d e s c r i p t i o n .o f
O beliseoides
eu n io u li,- a t r i c h o s t r o n g y l i d n e m a t o d e p a r a s i t e o f r a b b i t s , h a r e s , a n d '
ro d e n tsj
on s p e c i m e n s o b t a i n e d f r o m t h e s t o m a c h o f d o m e s t i c r a b b i t s
(O pyctolagus. aunieu lu s) i n New J e r s e y .
O b elisa u s, b u t- t h e f o l l o w i n g y e a r h e p r o p o s e d O belisaoides
g e n e r i c name
b e c a u s e t h e name
(G ra y b ill,
O rig in a lly he a ssig n e d th e
O beliscus vias p r e o c c u p i e d i n t h e p h y lu m M o l l u s c a
1 9,24).
The m o r p h o l o g i c a l f e a t u r e s o f t h e a d u l t
i
O belisaoides
c u n ie u li h a v e b e e n d e s c r i b e d b y G r a y b i l l ( 1 9 2 3 ) a n d C h a n d l e r ( 1 9 2 4 ) .
A lic a ta
(1932) d e s c r i b e d th e -l i f e h i s t o r y
th e h o s t.
He a l s o
and d e v e lo p m e n ta l s ta g e s , i n
d e s c r i b e d p r e p a r a s i t i c d ev e lo p m e n t and t h e r e s p o n s e s
of t h i r d s ta g e la rv a e to v a rio u s p h y s ic a l s ti m u l i .
N e ith e r he no r -
D i x o n ( 1 9 6 5 ) w e r e a b l e t o e s t a b l i s h p e r c u t a n e o u s 0.
a u n ia u li i n f e c t i o n s ,
in r a b b its .
A lic a ta
g u in e a p i g , w h ich i s
(1932) f o llo w e d t h e c o u r s e o f i n f e c t i o n i n t h e
an a b n o rm a l h o s t f o r t h i s n e m a to d e .
He a l s o u s e d .
0. a u n ia u li l a r v a e f o r t h e i m m u n i z a t i o n ■o f r a b b i t s a g a i n s t t h i s p a r a s i t e
( A l i c a t a , 1 9 65).
W o r le y
ra b b its
(1963) i n v e s t i g a t e d w h e th e r
0. a u n ia u li i n f e c t i o n s i n
r e s e m b l e d g a s t r i c n e m a t o d i a s i s o f •r u m i n a n t s , a n d c o n c l u d e d t h a t
a num ber o f s i m i l a r i t i e s
to d e i n f e c t io n
e x iste d .
He a l s o s u g g e s t e d t h i s
r a b b i t nem a­
a s , a l a b o r a t o r y m odel o f ru m in a n t h e l m i n t h i a s i s .
L a te r
W o r le y a n d Thom pson ( 1 9 6 3 ) i n v e s t i g a t e d t h e e f f i c a c y o f u s i n g r a b b i t s in fe c te d w ith
0. a u n ia u li-as a s y s t e m f o r a n t h e l m i n t i c , s c r e e n i n g .
-
T in er
(1965)
2
-
fo u n d t h a t t h e e f f e c t o f t h i a x a n t h e n e .d e la y e d em bryonal
d e v e lo p m e n t and d e s t r o y e d g ro w in g l a r v a e
(1966)
c o n c l u d e d t h a t many s i m i l a r i t i e s
p roduced by t h i s
vn v itv o .
a t.3
e x i s t b etw e en t h e i n f e c t i o n
g a s t r i c nem ato d e o f r a b b i t s
O stevtagta i n f e c t i o n s o f c a t t l e a n d s h e e p .
in fe c te d w ith th is
R u sse ll e t
and
Tvtohostvongytus o r
They s u g g e s t e d t h a t r a b b i t s
s t o m a c h , worm c o u l d b e u s e d a s a m o d e l i n t h e l a b o r a ­
to r y f o r th e s tu d y o f ru m in an t 't r i c h o s t r o n g y l o i d o s i s .
S c h w a rtz and -
S h o o k ( 1 9 3 1 ) r e p o r t e d t h a t r a b b i t s i n f e c t e d w i t h s t o m a c h worm s s u f f e r
fro m d i a r r h e a , e m a c i a t i o n , u l c e r a t i o n o f t h e s t o m a c h . w a l l , an em ia and
may e v e n d i e f r o m t h e i n f e c t i o n .
F ernando
(1968) s t u d i e d t h e d i s t r i b u t i o n
w ith in v a rio u s ;tis s p e s
of
i n th e. i n t e s t i n a l c e l l s
a fte r h o st in fe c tio n ,
0. c u n to u tt.
H em oglob i n .-was d e t e c t e d w i t h ­
o f fo u rth , s ta g e la r v a e
a p p r o x im a te ly 6 days •
and c o n tin u e d t o i n c r e a s e t h r o u g h o u t d e v e lo p m e n t.
I t w as a l s . o p r e s e n t i n p e r i e n t e r i c - f l u i d
f e m a l e a n d m a l e a d u l t w o rm s .
of te s t tissu e
o f h e m a t i n com pounds
and i n th e body w a l l o f b o th
0. o u n to u tt h a s b e e n u s e d a s -a s o u r c e
f o r c e r t a i n h is tp c h e m ic a l te c h n iq u e s in th e stu d y o f -
h i s t o , c h e m i s t r y o f - . t h e t r i c h o s t r o n g y l i d o s e s b y F r a n d s e n - ( 1 9 6 5 ) , who
a l s o r e p o r t e d t h a t c a rb o h y d r a te s and c o lla g e n w ere p r e s e n t i n . d i f ­
fe ren t tissu e s
of th is p a ra s ite
(E ra n d se n , 1966).
O bettsqotdes o u n to u tt i n f e c t i o n s : i n r a b b i t s a n d . h a r e s . h a v e
b e e n r e p o r t e d in 'm a n y a r e a s . o f t h e U n i t e d S t a t e s .
D orney.(1 9 6 3 )
re­
p o r t e d t h a t 98% o f 1the- f e - c a l ■s a m p l e s c o l l e c t e d d u r i n g tw o c o n s e c u t i v e
—3—
w i n t e r s from c o t t o n t a i l r a b b i t s
W isco n sin c o n ta in e d
(S y lv tla g u s flovvdanus) i n G r e e n B a y ,
Obe-Ilsoeldes o v a .
t h a t t h e i n c i d e n c e - 0.
M o rg a n a n d W a l l e r
(1940) fou n d
ounlc u l l a s 11,9% i n t h e Io w a c o t t o n t a i l
(S y lv lla g u s flo v ld a n u s m e a m si).
C lan cy
e t a l. ( 1 9 4 0 ) r e p o r t e d t h a t
t h i s - p a r a s i t e o c c u r r e d . i n t h e e a s t e r n . c o t t o n t a i l ■(S y lv lla g u s
floT ldanus
m qlluvus) a n d i n t h e New E n g l a n d ■c o t t o n t a i l . (Sylvllagus- tv a n s ltlo n a lls )
th ro u g h o u t-C o n n e c tic u t.
W o r le y
(1963) r e f e r r e d t o A l b r e c h t 's un­
p u b l i s h e d r e p o r t t h a t 68% o f t h e c o t t o n t a i l r a b b i t s
w ere i n f e c t e d w ith t h i s
s t o m a c h worm .
e x a m i n e d i n O hio
T h e -in c id e n c e , o f i n f e c t i o n w ith
0. e u n la u ll i n K a n s a s - r a b b i t s (S y lv lla g u s flovldanus). w as 16.6%
(F ra n k lin
e t a l. 19,66) a n d i n C l e v e l a n d C o u n ty * O k la h o m a , was 81.7%
i n swamp r a b b i t s .
(S yIvvlagus ^cmevloanus aquqtlaus) ( S m i t h , 1 9 4 0 ) .
( 1 9 3 4 ) f o u n d , t h i s p a r a s i t e i n " - r a b b i t s o f c e n t r a l O k la h o m a .
( 1 9 3 6 ) e x a m i n e d 54 s t o m a c h s o f s n o w s h o e h a r e s
Ward
A ld o u s
-(Lepus amevloanus
phaeenetus) f r o m a - s t u d y a r e a n e a r C u s h i n g , M i n n e s o t a . a n d r e p o r t e d t h a t
h a l f o f t h e m w e r e i n f e c t e d w i t h a n a v e r a g e o f ,.99
per hare.
D u n a g a n ..(1957) a n d L u b i n s k y
O bellsooldes o u n lcu ll
(1-957) r e p o r t e d
t h e snow shoe h a r e o f A la s k a and C an ad a, r e s p e c t i v e l y ,
0. o u n lo u ll i n
and P ark
(1 9 3 2 )
f o u n d - th e p a r a s i t e i n a K ansas .ja c k r a b b i t
(Lepus- c a llfo v n lo u s m ela n o tls)
i n . t h e New Y o r k Z o o l o g i c a l , P a r k . ,
( 1 9 4 4 ) n o t e d t h a t , 1116 o u t
o f 1428 s n o w s h o e h a r e s
E rick sO n
from M in n e s o ta w e re i n f e c t e d w i t h t h i s s p e c i e s .
He c o n s i d e r e d t h a t t h i s s t o m a c h worm i n f e c t i o n w as s i g n i f i c a n t i n p r o ­
d u cin g m o r t a l i t y - i n - t h e h a r e p o p u la tio n .
-4 —
O belis ooi.des o u n ic u li h a s p r e v i o u s l y b e e n r e p o r t e d f r o m w o o d c h u c k s
(Mavmota monax monax) i n M i s s o u r i ( T w i c h e l l , 1 9 3 9 ) ; I t a s c a P a r k ,
M in n eso ta
( W a lla c e , 1 9 4 2 ) ; c e n t r a l 'O h i o " and E a s t L a n s i n g , M ic h ig a n
(R ausch and T i n e r , 1 9 4 6 ).
T he l a t t e r a u t h o r s s u g g e s t e d t h a t t h e w ood­
c h u c k may b e a common h o s t f o r t h i s p a r a s i t e .
i n one l o c a l i t y
i n e a s t e r n O h io b y W o r le y
T h is was s u b s t a n t i a t e d
( p e r s o n a l c o m m u n i c a t i o n ) who
f o u n d a l l ■7 w o o d c h u c k s e x a m i n e d . w e r e i n f e c t e d w i t h m o d e r a t e o r h e a v y
worm b u r d e n s .
B ecause o f a num ber o f d i s c r e p a n c i e s i n th e d e s c r i p t i o n s
m easu rem en ts o f
and
O belisooides o u n io u li s p e c i m e n s f r o m d o m e s t i c r a b b i t s
i n T e x a s a n d New J e r s e y > C h a n d l e r ( 1 9 2 4 )
t h a n on e N o rth A m eric an s p e c i e s
of
f e lt th a t th ere
O b elisc o id e s.
b e e n no r e p o r t o f c o m p a ra tiv e s t u d i e s
c o u l d b e m o re
H ow ever, t h e r e h a s
on t h e b i o l o g y o f
0. o u n io u li
fro m d i f f e r e n t h o s t s .
A lic a ta
(1932)
fo u n d im m a tu re s t a g e s
n e c r o p s i e d a t d a y 31 p o s t i n o c u l a t i o n .
o f worms i n i n f e c t e d r a b b i t s
I t w as n o t e v i d e n t w h e t h e r t h e
t e r m " i m m a t u r e s t a g e " w as synonym ous, w i t h f o u r t h s t a g e l a r v a e w h i c h h e
d esc rib e d .
site s
R u sse ll
e t a l. ( 1 9 6 6 ) r e c o v e r e d n u m b e r s o f i m m a t u r e p a r a ­
i n d i r e c t p r o p o r t i o n t o th e s i z e o f t h e in o cu lu m g iv e n to r a b b i t s
n e c r o p s i e d 51 d a y s p o s t i n o c u l a t i o n .
S o llo d
e t a l. ( 1 9 6 8 ) c o n t r i b u t e d
f u r th e r to th e d e s c rip tio n of th e p a r a s i t i c stag es of
T h ey c l a s s i f i e d
0. o u n io u li.
as h i s t o t r o p i c form s f o u r t h s t a g e l a r v a e o b t a i n e d by
d i g e s t i o n o f g a s t r i c m ucosae s c r a p e d from r a b b i t s n e c r o p s i e d d u r in g
—5—
p re p a te n c y .
T he t e r m h i s t o t r o p i c p h a s e h a s b e e n u s e d t o d e n o t e t h e p e r i o d
d u r in g w h ich nem ato d e l a r v a e a r e p r e s e n t i n t h e t i s s u e s .
Some o f t h e
l a r v a e re m a in a l o n g e r tim e t h a n t h e n o r m a l . I t o 2 w eek p e r i o d i n t h e
m ucosa and f a i l . t o
g ro w a f t e r m o l t i n g t o t h e f o u r t h s t a g e .
(1954) o b s e r v e d t h i s p r o c e s s i n
S o m m e rv ille
Ostevtag-ia civaumei-ncta i n s h e e p a n d
f o u n d t h e l a r v a e r e m a i n e d i n t h e m u c o s a a s l o n g a s 3 m o n th s.. • H o w e v e r,
t h e r e h a s b e e n no r e p o r t o f a p r o lo n g e d h i s t o t r o p i c - p h a s e o f d e v e lo p ­
m ent f o r
0. c u n ic u li w h i c h r e s e m b l e s t h e l a r v a l t i s s u e s t a g e o f 0.
piToumo-incta d e s c r i b e d b y S o m m e r v i l l e ( 1 9 5 4 ) .
T h is p r o j e c t was i n i t i a t e d
is tic s
to
com pare t h e b i o l o g i c a l c h a r a c t e r ­
o f w oodchuck and c o t t o n t a i l i s o l a t e s
o f 0.
OuwLcuIi- a n d t o s t u d y
i t s h i s t o t r o p i c .p h a se .
\
'
MATERIALS ANB METHODS
The n em ato d e s t r a i n s , i s o l a t e d fro m a n ' e a s t e r n c o t t o n t a i l r a b b i t
(S y tv ita g u s fto v id a n u s m ea m si) a n d a s o u t h e r n w o o d c h u c k (Mavmota monax
monax.) i n O h i o - i n 1959 a n d 1965 r e s p e c t i v e l y , w e r e m a i n t a i n e d , i n l a b o r a v
to ry ra b b its
(O vyetolagus-o u n ip u tu s).
The m a i n t e n a n c e o f
o u n io u ti b.&s b e e n d e s c r i b e d p r e v i o u s l y ( W o r l e y , 1 9 6 3 ) .
w ere i n d i v i d u a l l y hou sed , i n w ir e b o tto m e d
The r a b b i t s
( h a l f - i n c h m esh) c a g e s .
T h ey w e r e f e d n o n m e d i c a t e d P e a v e y r a b b i t p e l l e t s
M in n e a p o lis, M in n eso ta). - I n f e c tiv e
O betisooides-
( th ir d stag e)
( P e a v e y Company,"
l a r v a e w ere c u l t u r e d by
i n c u b a t i n g a . m i x t u r e o f s t e r i l i z e d p e a t m oss arid f r e s h l y p a s s e d f e c e s , ,
f r o m i n f e c t e d . r a b b i t s f o r 8 t o 10 d a y s a t 20° t o 24°C i n .-c o v e re d g l a s s
d ish e s.
In fe c tiv e
l a r v a e w e r e h a r v e s t e d b y t h e B a e r m a n n , t e c h n i q u e , '■
L a r v a e w e r e w a sh e d ,- c o n c e n t r a t e d b y s e d i m e n t a t i o n a n d s t o r e d i n w a t e r
a t ; 3° -to '4°G f o r 3 - 5 d a y s b e f o r e i n n o c u l a t i o n . ,
T h e m e t h o d u s e d f o r ■c u l t u r i n g
feces to .o b ta in in fe c tiv e
k e p t .a s u n ifo rm as p o s s i b le i n b o th t h e .s t r a i n s ..
k ille d
l a r v a e w as
A fe w - l a r v a e w e r e h e a t
f o r m e a s u r e m e n t s a n d - p r e s e r v e d i n a m i x t u r e o f 95 p a r t s
eth an o l-an d 5 .p a r ts
70%
g l y c e r o l . ■ A l l m e a s u r e m e n t s w e r e m ade o n l a r v a e -
f r o m c u l t u r e s . 8 d a y s ■o l d .
A d u l t worms r e c o v e r e d f r o m a n a t u r a l l y
i n f e c t e d w o o d c h u c k i n O h io i n 1963 w e r e u s e d ■f o r m o r p h o l o g i c a l s t u d i e s .
T h e s e s p e c i m e n s w e r e .c o m p a re d w i t h a d u l t worms o f . t h e w o o d c h u c k s t r a i n •
a f te r 7 p a s s a g e s .in la b o r a to r y .ra b b its
stra in s
and a d u l t s
of th e c o t t o n t a i l
a f t e r m o re t h a n 10 p a s s a g e s . • T he t o t a l l e n g t h o f a d u l t worms -
—7—
w as m e a s u r e d w i t h t h e a i d o f a B & L m i c r o p r o j e c t o r .
T he l a r v a l a n d
o t h e r m e a s u r e m e n t s o f t h e a d u l t s w e r e made w i t h a L e i t z O r t h o l u x m i c r o ­
s c o p e e q u i p p e d w i t h an o c u l a r m i c r o m e t e r .
M o rp h o lo g ical d if f e r e n c e s '
b e t w e e n l a r v a e a n d a d u l t s . o f t h e tw o s t r a i n s w e r e c o m p a r e d s t a t i s t i c a l l y
u sin g s ta n d a rd d e v ia tio n s , a n a ly s is .o f v a r ia n c e ,
range t e s t
(D u n can , 1 9 5 5 ).
and D u n c an !s m u l t i p l e
T he d a t a w e r e p r o c e s s e d b y t h e . c o m p u t e r
S ig m a 7 BPM/BTM-D^B■a t t h e c o m p u t i n g c e n t e r , M o n t a n a . S t a t e U n i v e r s i t y .
T en C a l i f o r n i a n c r o s s - b r e d r a b b i t s
o f tw o l i t t e r s , b o m . a n d r e a r e d
i n th e co lo n y o f th e V e te r in a r y R e se a rc h L a b o r a to ry , w ere a l l o t t e d
tw o g r o u p s ,
and
, each c o n ta in in g 5 a n im a ls.
to
The a g e o f t h e . a n i - .
m a l s r a n g e d f r o m 128. t o 153 d a y s a n d t h e y w e i g h e d 6 - 8 p o u n d s a t t h e
s t a r t o f th e ,e x p e rim e n t.
I n f e c t i o n s i n e a c h a n im a l w e r e in d u c e d by
o r a l i n o c u l a t i o n o f 3 ,0 0 0 i n f e c t i v e
c a th e te r.
G ro u p s
and c o t t o n t a i l s t r a i n
l a r v a e g iv e n w i t h - a "B ard" p l a s t i c ■
a n d C-j. r e c e i v e d e q u i v a l e n t n u m b e r s o f w o o d c h u c k
la rv a e .
F e c a l egg c o u n ts
(L a n e , 1928) w ere
c a r r i e d o u t t w i c e w e e k l y • i n e a c h g r o u p f r o m d ay 25 p o s t i n o c u l a t i o n t o
w eek 23.
A l l r a b b i t s w e re w e ig h e d w e e k ly and w e re k e p t u n d e r d a i l y
o b s e r v a t i o n . . P r e i n o c u l a t i o n f e c a l e x a m in a tio n s w e re p e r f o r m e d .w ith
s a t u r a t e d sodium c h l o r i d e f l o t a t i o n
t o en su re- t h a t a l l a n im a ls w ere
free of g a s tro in te s tin a l p a ra s ite s .
F e c a l e x a m in a tio n s w e re p erfo rm ed
r o u t i n e l y fro m t h e 1 3 th day p o s t i n o c u l a t i o n u n t i l eg g s f i r s t
in th e f e c e s .
Two r a b b i t s
fro m g ro u p
and o n e . from
appeared
w e r e re m o v e d
d u r i n g t h e t e s t a n d t h e r e s t w e r e n e c r p p s i e d on t h e 1 6 8 d a y •p o s t i n o c u ­
la tio n .
-8 In th e second e x p e rim e n t, tw elv e C a lif o r n ia n c r o s s - b r e d r a b b its
r a n g i n g i n a g e f r o m 196 t o 199 d a y s ,w e r e a l l o t t e d t o 2 s i x - a n i m a l g r o u p s
(Wg a n d C g ) .
They w e r e i n o c u l a t e d w i t h 3 , 0 0 0 i n f e c t i v e
w oodchuck s t r a i n
( g r o u p C2 ) .
m en t.
la rv a e of th e
( g r o u p Wj) a n d a n e q u i v a l e n t d o s e o f c o t t o n t a i l l a r v a e
Two r a b b i t s
f r o m group] Cg w e r e e l i m i n a t e d f r o m t h e e x p e r i ­
One o f t h e s e d i e d a n d t h e o t h e r g a v e b i r t h
course of th e p r o je c ts
day p o s t i n o c u l a t i o n .
to young e a r ly in th e
T h e - r e m a i n i n g 10 r a b b i t s w e r e k i l l e d
on t h e 2 8 t h
In b o th e x p e rim e n ts l i t t e r m a t e s w ere s e p a r a te d
i n t o p a i r s b y s e x a n d o n e o f e a c h p a i r w as a l l o t t e d
to each ex p e rim e n ta l
g r o u p . • A l l t h e . r a b b i t s w e r e k i l l e d b y i n j e c t i n g a b o u t 5 ml.-, o f a i r i n
t h e o u t e r m a r g i n a l y e i n . o f t h e e a r . o r b y o v e r e x p o s u r e .to c h l o r o f o r m .
T h e - :s to m a c h o f e a c h a n i m a l w as l i g a t e d
to r e ta i n i t s
co n te n ts.
a t t h e e s o p h a g u s a n d t h e duodenum
I t w as re m o v e d f r o m t h e abdom en a n d t r a n s f e r r e d
t o a p e t r i d i s h c o n t a i n i n g 0.86% s a l i n e s o l u t i o n .
A p p ro x im a te ly o n e .s q .
cm. o f s t o m a c h t i s s u e a l o n g t h e l a t e r o v e n t r a l s i d e o f t h e g r e a t e r c u r v a ­
t u r e a n d o p p o s i t e t h e e s o p h a g e a l . o p e n i n g w as t a k e n f o r h i s t o l o g i c a l
stu d ie s.
T h e s t o m a c h , t i s s u e w as p r e s e r v e d i n 10% b u f f e r e d f o r m a l i n .
T h e - t i s s u e s w e r e s e c t i o n e d a t -6 m i c r o n s a n d s t a i n e d i n a z u r e e o s i n a t e
u s i n g ..H adlow 's- m e t h o d ■( L i l l i e ,
19-54) .
T h e - s t o m a c h w as o p e n e d a l o n g t h e
l e s s e r c u r v a t u r e a n d t h e m u c o s a l l i n i n g w as s c r a p e d .
T he i n g e s t a a n d
t h e m u c o s a l s c r a p i n g s w e r e w a s h e d t h r o u g h a 1 0 0 -m e s h s c r e e n t o - r e m o v e
fin e r d e b ris.
The w a s h in g s w e re exam ined and t h e num ber and s e x o f t h e
a d u l t - worm s w e r e r e c o r d e d .
A f t e r t h o r o u g h w a s h i n g , t h e s t o m a c h w as c u t
-9 in to
a n t e r i o r and p o s t e r i o r h a l v e s .
T he tw o p o r t i o n s
o f t h e sto m ach
w e r e i n c u b a t e d o v e r n i g h t on a m e c h a n i c a l s h a k e r a t 37°C i n w i d e m o u t h e d
b o ttle s
c o n t a i n i n g 0.86% s a l i n e s o l u t i o n t o f r e e h i s t o t r o p i c fo r m s f r o m
th e m ucosa.
The s to m ach t i s s u e and c o n t e n t s o f t h e b o t t l e s
w a s h e d on a 2 0 0 - m e s h s c r e e n ,
th e n w ere
c e n t r i f u g e d an d im m a tu re fo rm s r e c o v e r e d
w ith th e a id o f a d i s s e c t i n g m icro sco p e .
RESULTS
Worm e g g o u t p u t i n f e c e s :
days
The p r e p a t e n t p e r i o d a v e r a g e d a b o u t 17
(ra n g e 1 7 -1 9 ) i n t h e w oodchuck s t r a i n
th e c o tto n ta il s t r a i n .
a n d 15 d a y s
(ra n g e 15-17) in
Egg o u t p u t i n t h e f e c e s o f r a b b i t s
a n d C^) g i v e n 3 , 0 0 0 i n f e c t i v e l a r v a e i s
illu s tra te d
( g r o u p s W^
i n F i g u r e 1=
Egg
p r o d u c t i o n d u r i n g t h e f i r s t w e e k s o f p a t e n c y i n c r e a s e d m o re r a p i d l y i n
th e c o t t o n t a i l s t r a i n
W ^ ).
( g r o u p C^) t h a n i n . t h e w o o d c h u c k s t r a i n
(group.
T he e g g o u t p u t f l u c t u a t e d a t a h i g h l e v e l f o r 6 - 1 1 w e e k s p o s t ­
in o c u la tio n ,
in fe c tio n s
4 ra b b its
a f t e r w h ich i t
d ecreased a b ru p tly .
In th e l a t e r s ta g e o f
egg o u t p u t was d i m i n i s h e d g r a d u a l l y i n b o t h s t r a i n s .
i n f e c te d w ith th e c o t t o n t a i l s t r a i n ,
w ere o b s e r v e d .
In a l l
tw o p e a k s o f e g g o u t p u t ,
T he f i r s t p e a k a v e r a g e d a b o u t ■889 e g g s / g o f f e c e s a n d
w as b e t w e e n t h e 6 t h a n d 8 t h w e e k o f i n f e c t i o n .
The s e c o n d p e a k o c c u r ­
r e d b e t w e e n 8 t o 11 w e e k s p o s t i n o c u l a t i o n w i t h a n a v e r a g e o f 1000
e g g s/g o f - f e c e s .
Group. W^ s h w e d a p e a k a v e r a g i n g 499 e g g s / g o f f e c e s
d u r in g t h e 8 th o r . 9 t h week o f i n f e c t i o n .
Two o f f o u r . r a b b i t s i n t h i s
g r o u p sh o w e d a s e c o n d p e a k o f 559 e g g s / g o f f e c e s b e t w e e n t h e I l t h
1 6 th w eek p o s t i n o c u l a t i o n ,
peak.
tiv e ly .
a p p r o x i m a t e l y 25 a n d 21 d a y s a f t e r t h e f i r s t -
A t 161 d a y s p o s t i n o c u l a t i o n ,
h o u r p e r io d by r a b b i t s
T h e m ean r a t i o
and
t h e . n u m b e r o f e g g s p a s s e d i n •a 2 4 -
i n g r o u p s Wj a n d C j w as 2 , 9 9 8 a n d 1 7 , 9 3 1 r e s p e c ­
o f e g g s p e r g ra m o f f e c e s t o worms i n t h e w ood­
c h u c k s t r a i n w as I e g g / g / w o r m o r 2 . 9 5 e g g s / g / f e m a l e .
In th e c o t t o n t a i l
700 • - Woodchuck strain
600 -
® - Cottontail strain
S 200
P rep aten t
Period
We eks P o s t i n o c u l a t i o n
Figure I. Average fecal egg co u n ts of laboratory rabbits exposed to 3,000 larvae of 0. cunicuM .
mean values for 4-anim al groups.
Points shown are
-1 2 stra in ,
t h e r a t i o w as 0 - 9 3 e g g / g / w o r m o r : 2 . 5 6 e g g s / g / f e m a l e .
Worm s e x r a t i o s :
The f e m a l e - t o - m a l e worm r a t i o
i n a 2 8 ’ d a y -o ld
i n f e c t i o n w as - a b o u t : 1 : 1 . 19 i n w o o d c h u c k ■s t r a i n ' a n d 1 : 1 . 3 0 i n c o t t o n t a i l s tra in in fe c tio n s.
1 :1 .7 5 i n
I n 1 6 8 -day i n f e c t i o n s ,
t h e f e m a l e - t o - m a l e . r a t i o w as
t h e woodchuck, a n d , 1 : 2 . 0 3 i n c o t t o n t a i l - s t r a i n s .
D i s t r i b u t i o n o f worms i n t h e s t o m a c h :
in h ib ite d
f o u r t h s t a g e l a r v a e from t h e
T h e • a v e r a g e ■r e c o v e r y o f
a n t e r i o r h a l f o f t h e s t o m a c h w as
75 worms i n th e . w o o d c h u c k s t r a i n , a n d 201 i n t h e c o t t o n t a i l s t r a i n . . I n t h e p o s t e r i o r h a l f , v e r y fe w l a r v a l f o r m s o f e i t h e r s t r a i n w e r e r e ­
co v ered .
T he t o t a l worms a n d t h e f o u r t h s t a g e . l a r v a e r e c o v e r e d a r e
show n i n T a b l e s I .and I I .
A t .168 d a y s p o s t i n o c u l a t i o n , 41.49% o f t h e
g r o u p Wj w e r e f o u r t h s t a g e . f o r m s , v e r s u s .5 5 .0 4 % o f t h e g r o u p . C j .
28 d a y - o l d i n f e c t i o n ,
In a
t h e f o u r t h s t a g e l a r v a e c o m p r i s e d 28.3% and 31.6%
o f t h e w o rm .b u rd e n in ,w o o d c h u c k and c o t t o n t a i l s t r a i n s
re sp e c tiv e ly .
T h e ■a d u l t worms o f b o t h s t r a i n s -w ere g e n e r a l l y c o n f i n e d t o t h e
c a r d i a c a n d a n t e r i o r p o r t i o n o f t h e ;. f u n d i c r e g i o n i n e a r l y p a t e n c y
I n t h e l a t e r p a t e n t p e r i o d , t h e g a s t r i c - m u c o s a o f . t h e body and t h e
f u n d i c r e g io n s h ad an ev en d i s t r i b u t i o n
o f w o rm s .
i n t h e p r e s e n t s t u d y o f ■a p y l o r i c i n f e c t i o n w i t h
t h e p y l o r i c w a l l w as t h i c k e n e d , i n o n e r a b b i t
Pa th o g e n ic ity :
No e v i d e n c e was f o u n d
0. ouni-cuU , a l t h o u g h
(g ro u p W j ) .
G r o s s p a t h o l o g i c a l , o b s e r v a t i o n s . i n -g r o u p s Wg a n d
Cg show t h a t p e t e c h i a l l e s i o n s , w e r e . c o n c e n t r a t e d i n t h e c a r d i a c a n d
f u n d i c -re g io n s.
T he a s s o c i a t e d p a t h o l o g i c a l c h a n g e s w e r e p r i m a r i l y
T ab le I .
C o m p a r a t i v e r e c o v e r y o f 0. Ouniout-L l a r v a e and a d u l t s o f w o o d c h u c k a n d
c o t t o n t a i l s t r a i n s f r o m l a b o r a t o r y r a b b i t s a t 168 d a y s p o s t i n o c u l a t i o n . *
G ro u p a n d s t r a i n
R a b b i t No.
L4.
Wi
Number o f worms r e c o v e r e d
A d u lts
T o ta l
O .C .
71
50
160 ( I Her,
49?)
210
o .c.
74
33
77 ( 37cr,
409)
HO
O .C .
75
106
44 ( 3icr,
139)
150
(W oodchuck)
2 .1
% r e c o v e r y -----------------------C1
(C o tto n ta il)
% r e c o v e r y ------------------------
*
3 ,0 0 0 l a r v a e p e r r a b b i t .
3 .1
5 .2
o .c.
76
195
72 ( 69o%
39)
267
o .c.
77
369
143 ( 770",
669)
512
o.c.
78
208
430
(26 5d% 1 6 5 9 )
638
o .c.
80
223
302
(224d",
525
8 .3
7 .9
78?)
1 6 .2
T ab le I I .
C o m p a r a t i v e r e c o v e r y o f 0. o u n ic u li l a r v a e a n d a d u l t s o f w o o d c h u c k a n d
c o t t o n t a i l s t r a i n s fr o m l a b o r a t o r y r a b b i t s a t 28 d a y s p o s t i n o c u l a t i o n . *
G roup a n d s t r a i n
R a b b i t No.
L4.
W2
(W oodchuck)
125
239 C ie o d t,
79?)
364
O .C .
82
106
169 ( 85or,
84?)
275
O .C .
83
70
384
(205cr, 1 7 9 ? )
454
O .C .
84
59
270 (146(7, 1 2 4 ? )
329
O .C .
85
125
307
(167(7, 1 4 0 ? )
432
3 .3
8 .8
99
427
O .C . 87
*
3 ,0 0 0 l a r v a e p e r r a b b i t .
1 2 .1
( 2 6 8 dr, 1 5 9 ? )
526
88
190
347 (219(7, 1 2 8 ? )
537
O .C . 91
130
313
(147(7, 1 6 6 ? )
443
O .C . 92
284
381 (196(7, 1 8 5 ? )
665
O .C .
% r e c o v e r y ------------------------
T o tal
O .C . 81
% r e c o v e r y -----------------------C2
(C o tto n ta il)
Number c)f worms r e c o v e r e d
A d u lts
5 .9
1 2 .2
1 8 .1
-1 5 th o se of g a s t r i t i s ,
t h e m ucosa b e in g s tu d d e d w ith r e d d o ts i n s m a ll
l o c a l i z e d a r e a s , ed e m a to u s f u n d i c r u g a e , p e t e c h i a l h a e m o r rh a g e s and
a fe w a r e a s o f u l c e r a t i o n .
The n u m b e r a n d s e v e r i t y o f p e t e c h i a l
h a e m o r r h a g e s -on t h e g a s t r i c m u co sa a p p e a r e d t o . i n c r e a s e i n t h e c a r d i a c ,
r e g i o n i n gro-up Wg.
The r a b b i t s
d is trib u te d p e te c h ia l le sio n s
i n g r o u p Cg h a d m i l d a n d u n i f o r m l y
in th e fu n d ic re g io n .
H isto lo g ic a l
s t u d i e s r e v e a l e d t h a t t h e g r o u p Wg i n som e i n s t a n c e s p r o d u c e d t h e m o s t
se v e re .le s io n s
and h ae m o rrh ag e s b elo w t h e m u s c u la r is m ucosae
(F ig u re 9)
T h e r e w e r e m a n y 'e m b e d d e d l a r v a e ,. w i t h l a r g e n u m b e rs o f e o s i n o p h i l s
and
ly m p h o c y te s i n t h e s u r r o u n d in g t i s s u e , w h e re a s i n t h e r a b b i t s o f ;g r o u p
Cg t h e i n f i l t r a t i o n
of e o sin o p h ils
(F ig u res
T he e m b e d d e d l a r v a e w e r e s e e n b o t h i n w o o d c h u c k
2 and 3 ) .
and c o t t o n t a i l s t r a i n s
(F ig u re s. 4 , 5 , and 8 ).
At n ec ro p sy a l l r a b b its
e x c e lle n t c o n d itio n .
a n d l y m p h o c y t e s w as m i l d a n d u n i f o r m
o f g r o u p s W^ a n d C^ a p p e a r e d t o b e -in
The p o s t e r i o r end o f t h e f u n d i c r e g i o n a p p e a re d
t o b e . t h e m o s t common s i t e o f t i s s u e
p e te c h ia l le sio n s
ra b b its
changes in b o th s t r a i n s .
a n d a few c r a t e r i f o r m u l c e r s w e r e m o r e common i n
i n f e c t e d w i t h woodchuck s t r a i n
( F i g u r e s 6 and 7 ) .
O ld
th an in c o t t o n t a i l in fe c tio n s
A fe w f r e s h p e t e c h i a l h a e m o r r h a g e s w e r e p r e s e n t
' a l o n g w i t h t h e o l d o n e s i n tw o r a b b i t s
(g ro u p C ^).
M ore o r l e s s . s i m i ­
l a r p a t h o l o g i c a l c h a n g e s .in th e t i s s u e w ere se e n i n b o th s t r a i n s .
a f f e c t e d a r e a s o f e i t h e r gro u p
In
(W]_ a n d C ^ ) , t h e c r y p t s W e r e • d i l a t e d a n d
t h e u s u a l s m o o t h , l i n e a l a r r a n g e m e n t o f t h e g a s t r i c n iu c o s a w as l a c k i n g .
-1 6 -
F ig u re s 2 ,
3.
C o m p a ra tiv e ly m p h o c y tic i n f i l t r a t i o n s i n g a s t r i c m ucosa
o f r a b b i t s i n f e c t e d w i t h 0. o u n ia u li o f t h e c o t t o n t a i l
s t r a i n (2) and t h e w oodchuck s t r a i n (3 ) (2 8 -d a y i n f e c ­
tio n s).
A z u r e E o s i n a t e (A. E . ) x 1 2 5 .
-1 7 -
—1 8 -
E x p l a n a t i o n ■o f f i g u r e s . :
F i g u r e 4 , ' E o s i n o p h i l s (E) s u r r o u n d i n g 0. CuniIouZ-I. l a r v a (L) o f t h e
c o t t o n t a i l , s t r a i n e m b e d d e d i n •g a s t r i c ' m u c o s a ( 2 8 - d a y i n f e c ­
t i o n ) , A, E. , x '380 =
F ig u re 5.
C e l l u l a r d e b r i s i n t h e lu m en o f g l a n d s (N) a n d e o s i n o p h i l s
(E) a r o u n d .0.. CuniIcuZi- ■l a r v a (L) o f t h e w o o d c h u c k s t r a i n ■
em b e d d e d i n g a s t r i c m u s o s a ( 2 8 - d a y i n f e c t i o n ) .
A. E , ,
x 425.
-1 9 -
—2 0 -
E x p la n a tio n of f i g u r e s :
F ig u re 6.
C r a t e r i f o r m m u c o s a l u l c e r w i t h c o a g u l a t i o n n e c r o s i s (C) i n
1 6 8 - d a y r a b b i t i n f e c t i o n w i t h 0. ouni-eut-l ■(w o o d c h u c k ■s t r a i n ) . .
A, E . , x 1 0 0 .
F i g u r e 7. ' An a r e a o f n e c r o s i s (N) i n t h e g a s t r i c m u c o s a . . A n a r r o w
f i s s u r e (F ) l e a d s f r o m t h e n e c r o t i c a r e a t o t h e e p i t h e l i a l
s u r f a c e i n 1 6 8 - d a y r a b b i t i n f e c t i o n w i t h 0. GunyIeuti. (wood-:
c h u c k s t r a i n ) . A. E . , x 1 6 0 .
-2 1 -
-2 2 -
E x p la n a tio n o f f i g u r e s :
F i g u r e 8.
U n i f o r m f o c a l c e l l u l a r i n f i l t r a t i o n a n d e m b e d d e d l a r v a (L)
o f 0. e u n ie u li (w o o d c h u c k s t r a i n ) i n g a s t r i c m u c o s a o f .
r a b b i t ■( 1 6 8 - d a y i n f e c t i o n ) .
A. E . , x 1 2 0 .
F ig u re 9.
C o n g e s t i o n (C) a n d h a e m o r r h a g e (H) b e l o w t h e m u s c u l a r i s
m u c o s a e (M) w i t h 0. ouniouli. (w o o d c h u c k s t r a i n ) l a r v a (L)
em bedded i n g a s t r i c m ucosa o f r a b b i t (2 8 -d a y i n f e c t i o n ) .
A. E . j x 9 5 . '
-2 3 I n o t h e r a r e a s , n e c r o s i s w as l e s s p r o m i n e n t a n d o f t e n l i m i t e d t o s m a l l
c l u m p s ■o f c e l l u l a r d e b r i s . ( F i g u r e 5 ) .
c o m p ris e d o f ly m p h o id c e l l s
N o d u les o f c e l l u l a r i n f la m a tio n
and e o s i n o p h i l s w ere n o te d i n t h e s e a r e a s .
L y m p h o id n o d u l e s w e r e o f t e n e x t e n d e d t o t h e m u s c u l a r i s m u c o s a e .
It
a p p e a re d t h a t th e f u n c t i o n a l g a s t r i c p aren ch y m al c e l l s w ere r e p la c e d
i n a f f e c t e d a r e a s by i n v a g i n a t e d s u r f a c e e p i t h e l i u m .
th e u lc e r s
th e t i s s u e
changes w ere:
At t h e s i t e
of
an e ro d e d e p i t h e l i a l l a y e r ,
c o a g u l a t i o n n e c r o s i s , w h i c h e x t e n d e d t o m u s c u l a r i s m u c o s a e i n somec a s e s o f th e woodchuck s t r a i n
( F i g u r e s 6 and 7 ) , and a c o n c e n t r a t i o n
of le u k o c y te s.
F e c e s w e re form ed and o f n o rm a l c o n s i s t e n c y i n a l l a n im a ls th r o u g h ­
o u t th e ex p e rim e n ts.
No b l o o d w as e v i d e n t f r o m a g r o s s . e x a m i n a t i o n o f
th e s t o o l s .
T h e r e w as n o s i g n i f i c a n t d e c l i n e i n b o d y w e i g h t .
H o w e v e r, t h e
i n c r e a s e i n w e i g h t w as s u p p r e s s e d d u r i n g w e e k s 8 t o 10 p o s t i n o c u u l a t i o n ,
w hen f e c a l e g g c o u n t s w e r e h i g h i n b o t h s t r a i n s .
S t a t i s t i c a l a n a ly sis
i n d i c a t e d t h a t le n g th m easu rem en ts o f a d u l t
0. e u n io u li o f w o o d c h u c k a n d r a b b i t o r i g i n w e r e . s i g n i f i c a n t l y d i f f e r e n t
a t t h e 1% l e v e l
(T a b le I I I ) .
The l e n g t h s o f t h i r d s t a g e l a r v a e o f w ood­
chuck and c o t t o n t a i l s t r a i n s w ere n o t s i g n i f i c a n t l y
d iffe re n t.
M easurem ents'^" o f ObeZisooides ouniouZi l a r v a e a n d a d u l t s
w oodchuck and a f t e r p a s s a g e i n l a b o r a t o r y r a b b i t s . .
T ab le I I I .
d ire c tly
fr o m
________________ Number o f p a s s a g e s ________________
D ire c t
(W oodchuck s t r a i n )
7
>10
(W oodchuck s t r a i n
(C o tto n ta il s tr a in )
1 0 . OOa ± 2 . 3 ( 1 7 ) *
0 . 6 9 a ± 0.0 2
8 . 80b ± 0. 45 (30)
0.66b ± 0 .0 4
7 . 4 0 c ± 0 .7 2 (16)
0 . 5 9 c ± 0.05
0 . 42b ± 0. 02
0.39C
A d u lt m ale
Body
Esophagus
0.48a
S p ic u le s
±
o.0 2
+
0.0 3
A d u lt fe m a le
1 9 . 90a ± 0 .8 5 (33)
Body
Esophagus
V u lv a
In fe c tiv e
13.52% ± 1.09 (20)
1 1 . 0 6 c ± 2 . 1 8 (34)
0 . 9 3 a ± 0.05
0 . 86b ± 0.0 6
0 . 77c ± 0.0 6
15.58a ± o . 7 3
10.5 4b ± 0 . 8 8
8 . 7 6 C ± 0.8 5
larv a e
Body
0 . 67b ± 0 . 0 3 (50)
0 . 66b ± 0 . 0 3 (50)
T ail
0 . 0 6 b ± 0 . 0 1 (32)
0 . 0 6 b ± 0.00 4 (42)
L en g th i n m i l l i m e t e r s .
* Number o f worms i n p a r e n t h e s e s .
a M eans b e a r i n g d i f f e r e n t s u p e r s c r i p t l e t t e r s
d iffe r sig n ific a n tly
(P < 0 .0 1 ).
1
NJ
4N
I
DISCUSSION
T h i s i n v e s t i g a t i o n w as d e s i g n e d t o a s c e r t a i n w h e t h e r t h e p h y s i o ­
l o g i c a l and m o r p h o l o g i c a l d i f f e r e n c e s b e tw e e n i s o l a t e s
of
Obet-iscoides
OuniLouti- f r o m t h e w o o d c h u c k a n d c o t t o n t a i l r a b b i t w e r e s u f f i c i e n t l y
s ig n if ic a n t to w a rran t t h e i r c la s s i f i c a t io n
th is p a ra site .
V a ria tio n s
stra in
of ra b b it o rig in
num ber o f a d u l t
The p r e p a t e n t p e r i o d i n t h e
( g r o u p W^) w as 2 d a y s . l o n g e r t h a n i n . t h e
(gro u p C ^ )•
of
i n t h e -n a tu re and r a t e o f e g g . p r o d u c tio n
w e r e among t h e m o s t p r o m i n e n t d i f f e r e n c e s .
w oodchuck s t r a i n
a s tw o d i s t i n c t s t r a i n s
c o tto n ta il
T h e •h i g h -egg o u t p u t i n a 2 4 - h o u r - p e r i o d b y worms
( g r o u p . C^) s h o w s , e i t h e r h i g h f e c u n d i t y o r a g r e a t
f e m a l e w o rm s .
T he e g g c o u n t a t 165 d a y s p o s t i n o c u l a t i o n
w as c o m p a r e d t o t h e n u m b e r o f f e m a l e s r e c o v e r e d a t n e c r o p s y on d ay 168
p o stin o c u la tio n .
The m e a n . r a t i o
o f f e m a l e s t o . e g g s / g r a m o f f e c e s was
a p p r o x im a te ly , th e sam e i n b o th s t r a i n s .
c o tto n ta il stra in
R a b b i t s ■i n f e c t e d . w i t h t h e
( g r o u p C^) w e r e m o re c o n s i s t e n t i n e x h i b i t i n g 2 p e a k s ,
a p p r o x im a te ly 3 w eeks a p a rt.T h ere w ere no o b v io u s c l i n i c a l s ig n s a s s o c i a t e d w ith th e i n f e c t i o n s
in e ith e r s tr a in .
The t i s s u e
r e a c t i o n s i n t h e g a s t r i c m u c o s a b ec am e
i n c r e a s i n g l y m arked i n o l d e r i n f e c t i o n s .
a f te r in fe c tio n
T h u s , a n i m a l s k i l l e d 28 d a y s
e x h i b i t e d h y p e r e o s i n o p h i l i a c o n c e n t r a t e d -aroUri-d t h e
e m b ed d e d l a r v a e o f t h e c o t t o n t a i l s t r a i n .
In th e w oodchuck s t r a i n , -
ly m p h o c y t o s is w as-m uch m o r e ;p ro n o u n c e d an d t h e l a r v a e w e re s u r r o u n d e d
by e o s in o p h ils .
In o ld e r in fe c tio n s
t h e c e l l u l a r i n f i l t r a t i o n was
- 26—
d iffu se d - r a t h e r th an lo c a liz e d .
em b e d d e d i n t h e t i s s u e
In b o th s t r a i n s
t h e l a r v a e w ere d e e p ly
c l o s e t o t h e m u s c u l a r i s -m u c o s a e ,
The e x p e r i m e n t c o n d u c t e d b y . R o s s a n d P u r c e l l
T rieh o stp o -
( 1 9 6 9 ) on
ngytus a xei sh o w e d t h a t t h e s e v e r a l p a s s a g e s o f t h i s p a r a s i t e i n o ne
h o s t s p e c i e s w o u ld r e d u c e t h e p a t h o g e n i c i t y - o f .th e p a r a s i t e .
p re s e n t stu d y i s
The
in agreem ent w ith th e s e a u th o rs w ith r e f e r e n c e to th e
c o tto n ta il s tra in ;o f
0. QuwI guI-I^ w h i c h h a d m o re t h a n 12 p a s s a g e s i n
lab o ra to ry - r a b b i t s .
On t h e o n e h an d ,- t h e w o o d c h u c k s t r a i n
seem ed:
m o d e r a t e l y w e l l :a d a p t e d , t o t h e new h o s t a f t e r 8 p a s s a g e s i n l a b o r a t o r y
ra b b its.
N e v e r t h e l e s s , t h e m a r k e d t i s s u e dam age i n r a b b i t s
a n d ¥ « ) b y t h e w o o d c h u c k s t r a i n w as p r o b a b l y d u e t o i t s
(groups
in co m p lete
a d a p t a b i l i t y . t o t h e new h o s t .
I n g e n e r a l , m o re worms w e r e r e c o v e r e d a t n e c r o p s y f r o m r a b b i t s .
(groups
a n d Cg), i n f e c t e d w i t h t h e c o t t o n t a i l , s t r a i n
(groups
a n d W2 ) i n f e c t e d w i t h t h e w o o d c h u c k s t r a i n .
f e m a l e .r a t i o
(1932),
T he m a l e - t o - f e m a l e r a t i o w a s 1 : 1 i n r a b b i t s
i n f e c t e d w ith 1 ,0 0 0 l a r v a e
e t -a t.3 1 9 6 6 ) .
f e m a l e r a t i o w as 1 : 3 .
v a ria tio n s
T he m a l e - t o -
i n b o t h s t r a i n s w as i n a g r e e m e n t . w i t h , t h e r a t i o . o f ' I .'81:1
fo u n d by : A l i c a t a
(R u ssell
t h a n from r a b b i t s
(S o iled
e t a t.'^ 1 9 6 8 ) a n d 2 , 5 0 0 l a r v a e
H o w e v e r, W o r le y
(1963) fo u n d t h a t t h e m a l e - t o - .
P o s s ib ly th e sex r a t i o
i n h o s t a g e a n d am o u n t o f i n o c u l u m .
d i f f e r e n c e s may b e d u e t o
G e n e r a l l y , i n m o s t 1o f .
t h e n e m a to d e s , m ales a r e fe w er i n num ber and s h o r t e r ,liv e d , th a n fe m a le s .
of a p a r tic u la r sp e c ie s.
T h is a p p e a re d to b e r e v e r s e d i n
I
0.- eunioutv.
-2 7 As • t h e i n f e c t i o n b e c a m e o l d e r t h e m a l e s i n c r e a s e d i n n iim b e r. ' I t was
n o t e v id e n t w h e th e r t h e m ales h ad g r e a t e r lo n g e v ity th a n fe m a les o r
w h e th e r th e i n h i b i t e d
f o u r th , s t a g e la r v a e ',
c o n t r i b u t e m a in ly t o t h e m ale p o p u l a t i o n .
may h a v e i n f l u e n c e d t h e s e x r a t i o
if
t h e y c o u l d ■d e v e l o p , w o u l d
P ro b a b ly , b o th th e s e fa c to r s
of th is p a ra site .
The d i f f e r e n c e s b e t w e e n m ean l e n g t h s o f a d u l t worms f r o m e a c h
s t r a i n w ere s i g n i f i c a n t a t th e I p e r c e n t l e v e l ,
b o t h s e x e s o f w ood­
c h u c k s t r a i n worm s f r o m l a b o r a t o r y ' r a b b i t s h a d -mean l e n g t h s - g r e a t e r
th an th o se o f th e c o t t o n t a i l s t r a i n . i n
th is
t h e sam e h o s t s ;
The r e s u l t s
of
stu d y s u g g e s t .th a t th e d if f e r e n c e s in le n g th s o f s p i c u l e s , body,
e s o p h a g u s -and t h e d i s t a n c e f r o m a n t e r i o r e n d t o v u l v a r r e g i o n b e t w e e n
t h e tw o s t r a i n s
r e f l e c t som e f o r m o f - i n h e r e n t d i f f e r e n c e r a t h e r t h a n
h o s t in f lu e n c e , as th e h o s ts
stra in s.
re m a in ed u n d e r s i m i l a r c o n tro l, i n b o th
I n f l u e n c e . o f t h e h o s t on a n y m e a s u r e m e n t s o f t h e . p a r a s i t e may
b e .ru le d o u t.
D i f f e r e n c e ' s . b e t w e e n worms r e c o v e r e d , f r o m w o o d c h u c k s a n d
la b o ra to ry .ra b b its
i n f e c t e d w i t h t h e , sam e s t r a i n . w e r e a l s o s i g n i f i c a n t '
i n a l l .m e a su re m e n ts.
■
The c o m p a r a t i v e s t u n t i n g o f t h e . a d u l t worms o f -
w oodchuck s t r a i n i n l a b o r a t o r y r a b b i t s
r a b b i t h o s t w ere l e s s
T he
su g g e sts t h a t c o n d itio n s in th e
f a v o r a b le th a n i n th e woodchuck.
aAnlt -O betisopides o u n ia u li m e a s u r e d b y . A l i e a t a ( 1 9 3 2 ) w e r e
much s m a l l e r t h a n t h e . w o r m s exam ined, b y e i t h e r C h a n d l e r
th e a u th o r.
The g r o w t h o f t h e p a r a s i t e i s
(1924) o r by
i n f l u e n c e d b y a n u m b e r, o f
f a c t o r s su ch as ag e , s i z e , p h y s i c a l c o n d itio n , m e ta b o lic r a t e
and fo o d
-2 8 su p p ly o f th e h o s t .
The s p e c i m e n s m e a s u r e d b y C h a n d l e r sh o w ed g r e a t e r
l e n g t h i n body and s p i c u l e s -th an t h o s e m e a s u re d by t h e a u t h o r .
th e se d iffe re n c e s
P erhaps
i n s i z e w e r e d u e t o h o s t i n f l u e n c e on t h e p a r a s i t e s .
H i s t o t r o p i c .f o r m s :.
The t e r m " h i s t o t r o p i c " r e f e r s
f o u r t h s t a g e l a r v a e p r e s e n t in , t h e t i s s u e
w eek p e r i o d , i n w h ic h g ro w th i s
t o t h e n em ato d e
f o r l o n g e r t h a n t h e n o r m a l .1 -2
i n h i b i t e d a f t e r th e t h i r d m o lt.
In h i­
b i t i o n o f l a r v a l d ev e lo p m e n t i n - t h e h o s t h a s b e e n n o t e d i n s e v e r a l h o s t t
p a r a s i t e s y s te m s ,. e . g .
(M ic h e l, - 1 9 5 2 ),
Tri-ohostrongylus v e to rta e fe rm is i n . r a b b i t s
O sterta g ia eireum oinbta i n s h e e p ( D u n s m o r e , 1 9 6 0 ) , a n d
O sterta g ia o s te r ta g i i n c a l v e s ( M i c h e l , 1 9 6 3 ) .
R o b e rts and K e ith
(1959) o b serv ed - a r r e s t e d l a r v a l s t a g e s o f
Haemon-
chus .,Jplaeei in , ca lves a n d s t a t e d t h a t " o n r e m o v a l - o f t h e a d u l t worms b y
p h e n o t h i a z i n e t h e im m a tu re s t a g e s
t h e r e u p o n move i n t o
b o w e l a n d c o n t i n u e t h e i r d e v e l o p m e n t " .-
th e lu m en-of th e
They s u g g e s t e d t h a t - t h e m a tu r e .
worms may b e r e s p o n s i b l e f o r i n h i b i t i n g t h e d e v e l o p m e n t o f l a r v a e .
D u n sm o re
sta tin g
(1 9 6 3 )
f u r t h e r d e v e lo p e d t h e h y p o t h e s i s o f R o b e r ts and K e i t h ,
t h a t t h e immune r e a c t i o n o f t h e h o s t w o u l d o n l y a l l o w c e r t a i n
l a r v a l num bers t o m a tu re i n o r d e r t o m a i n t a i n a t o l e r a t e d l e v e l o f
a d u lts
i n t h e sto m ach .
I n h i b i t i o n o f d ev e lo p m e n t a t t h e f o u r t h l a r v a l s t a g e i n
eo n to rtu s w as r e p o r t e d b y D i n e e n a n d W a g la n d ( 1 9 6 6 ) .
im m u n o lo g ica l i n t e r p r e t a t i o n
Haemonehus
T h ey a c c e p t e d a n
fo r th e cause o f la r v a l r e ta r d a tio n
t h a n t h e i n t e r p r e t a t i o n b a s e d upon c o m p e titio n b e tw e e n p a r a s i t e s
ra th e r
for
-2 9 e i t h e r sp ace o r n u t r i t i o n a l re q u ire m e n ts.
M ich el
( 1 9 5 2 ) w as o f t h e
o p i n i o n t h a t a r r e s t e d s t a g e s o f l a r v a e u s u a l l y d e v e l o p i n r e l a y s w hen
th e re s is ta n c e o f th e h o s t d e c lin e s .
A nderson e t
a l. ( 1 9 6 5 ) s u g g e s t e d t h a t i n h i b i t i o n o f t h e p a r a s i t e
O stevtagia o s te v ta g i w as a s s o c i a t e d w i t h p h y s i o l o g i c a l c h a n g e s o c c u r r i n g
I h t h e h o s t o r p a r a s i t e a t a p a r t i c u l a r t i m e a n d was n o t n e c e s s a r i l y a
f u n c t i o n o f a c q u i r e d im m u n ity .
S o llo d
(1967) a d v a n c e d an e p id e m io ­
lo g ic a l e x p la n a tio n to account fo r i n h ib itio n of th e e a r ly fo u rth s ta g e
l a r v a e i n 0.
R u sse ll
o stev ta g i.e t a t. ( 1 9 6 6 ) o b s e r v e d i n h i b i t e d O b e tisc o id e s,o u n ic u li .
l a r v a e s i m i l a r t o t h e a r r e s t e d im m a tu re s t a g e s o f o t h e r t r i c h o s t r o n g y l e
p a ra site s
i n r a b b i t s n e c r o p s i e d on - d a y 51 p o s t i n o c u l a t i o n .
e t,
S o ile d
a t. ( 1 9 6 8 ) r e c o v e r e d e a r l y f o u r t h s t a g e l a r v a e , w h i c h a p p e a r e d t o b e r e t a r d e d i n t h e i r d ev e lo p m e n t,
fro m t h e g a s t r i c m ucosa o f t w o . r a b b i t s
k i l l e d w hen t h e i r i n f e c t i o n s b e c a m e p a t e n t . .
D e la y e d d e v e lo p m e n t h a s b e e n o b s e r v e d by th e a u t h o r i n l a b o r a t o r y
ra b b its
in f e c te d w ith
e t a l. ( 1 9 6 8 ) .
0. eu n ie u ti', t h i s c o n f i r m s t h e f i n d i n g s o f S o l l o d
;,
:
T he p e r c e n t a g e r e c o v e r y o f r e t a r d e d l a r v a e o f t h e w ood­
c h u c k s t r a i n . i n 2 8 - d a y i n f e c t i o n s w as h a l f t h a t o f t h e c o t t o n t a i l . s t r a i n .
T h e w o o d c h u ck - s t r a i n - e x h i b i t e d a c o n t i n u o u s - d e c r e a s e i n i n h i b i t e d
as th e age of th e i n f e c t io n
in c re a se d .
larv a e
R e ta rd a tio n o f th e p a r a s ite
at
t h e - f o u r t h s t a g e w as t h e m o s t c o n s i s t e n t p h en o m en o n o b s e r v e d i n a n i m a l s ■
( g r o u p C-J^ a n d Cg) i n f e c t e d w i t h t h e c o t t o n t a i l s t r a i n .
T he d e g r e e o f
-3 0
re ta rd a tio n .in v o lv e d le s s
t h a n h a l f o f t h e worm b u r d e n i n t h e w o o d c h u c k
a n d m o re t h a n h a l f o f t h e t o t a l worm p o p u l a t i o n i n t h e c o t t o n t a i l s t r a i n
i n 168-day i n f e c t i o n s .
co m p rised l e s s
A t 28 d a y s p o s t i n o c u l a t i o n , i n h i b i t e d
la rv a e .
t h a n h a l f , o f t h e worm b u r d e n i n b o t h s t r a i n s . ■ No f o u r t h
s t a g e f o r m s w e r e o b s e r v e d i n tw o r a b b i t s i n f e c t e d w i t h
'0. ouniculi-
(w o o d c h u c k s t r a i n ) w h i c h w e r e n e c r o p s i e d on - d a y 225 p o s t i n o c u l a t i o n . :
P a r a lle l in fe c tio n s
o f tw o o t h e r r a b b i t s w i t h t h e c o t t o n t a i l s t r a i n ,
show ed i n h i b i t i o n a t t h e e a r l y f o u r t h s t a g e .
w oodchuck s t r a i n ,
in h ib ite d at th ird
a t .168 d a y s p o s t i n o c u l a t i o n .
A fe w l a r v a e o f t h e
s t a g e w ere o b s e r v e d i n .t w o r a b b i t s
T he l a r v a e w e r e - s t i l l e n s h e a t h e d a n d w e r e
a p p r o x i m a t e l y -.the sam e s i z e a s t h e , i n f e c t i v e l a r v a e i n o c u l a t e d .
C h itw o o d
(1 9 5 7 )
fa v o re d th e u se o f p h y s i o l o g ic a l and g e n e r ic
f a c t o r s ' a s b e i n g m o re v a l u a b l e f o r s u b s t a n t i a t i n g
stra in s
r e l a t i o n s h i p s b etw een
th a n m o r p h o lo g ic a l d i f f e r e n c e s . ■ The woodchuck s t r a i n d i f f e r e d
fro m t h e - c o t t o n t a i l s t r a i n
a s : • d elay e d p a te n c y ;
i n some m a j o r b i o l o g i c a l c h a r a c t e r i s t i c s
such
lo w e g g o u t p u t w i t h o r w i t h o u t a s e c o n d p e a k ; low
p e r c e n t a g e r e c o v e r y o f worms a t n e c r o p s y ; s e v e r e p e t e c h i a l l e s i o n s a n d
s p o ra d ic o c c u rre n c e o f u l c e r s ; and g r e a t e r le n g th s i n b o d y , s p i c u l e s ,
v u lv a r re g io n and eso p h ag u s.
These c h a r a c t e r i s t i c s
t e n c e o f tw o d i s t i n c t s t r a i n s . o f
sim ila ritie s
co n firm th e e x i s ­
0. Oun-Iauli i n s p i t e o f a n u m b e r . o f
i n . t h e w o o d c h u c k a n d c o t t o n t a i l s t r a i n s ..
O b serv atio n s of
a .p ro lo n g ed , h i s t o t r o p i c . form a l s o c o n f ir m t h a t i n h i b i t i o n a t t h e e a r l y
f o u r t h s t a g e i s . . a n a t u r a l phenom enon i n . t h e
life
c y c l e .o f t h i s p a r a s i t e .
LITERATURE CITED ■
A l d o u s C. M.
1936.
Food h a b i t s
Mammoli ' 1 7 : " 1 7 5 ^ 1 7 6 .
A l i c a f c a , J . E.
1932;
ooide's- e u n io u li..
___ ;_________, . .
1965.
of
Lepus amevieanus phaeemetus.
J; •
L i f e h i s t o r y o f t h e r a b b i t s t o m a c h worm O belisJ . A g r i . R e s . W a s h i n g t o n , D. C.-, 4 4 : 4 0 1 - 4 2 0 ,
I n d u c t i o n o f p a r t i a l im m u n ity i n r a b b i t s
to
O b eliS co id es . e u n ie u li - . f o l l o w i n g i n t r a p e r i t o n e a l - i n o c u l a t i o n w i t h
h o m o lo g o u s i n f e c t i v e
l a r v a e .-
J.
P a ra sito l.
51 ( 2 .
S ect.
2):
.
39.
A n d e r s o n , W.., J ; A r m o u r , F , W. J e n n i n g s ," J ,, D. R i t c h i e , a n d -G: M. •
U r q u h a r t 1965.
I n h i b i t e d d e v e l o p m e n t o f O stevta g ia .o s te v ia g i.
( C o r r e s p o n d e n c e ) V e t. R ec.
77: 146-147.
.
C h a n d l e r , A. C.. 1 9 2 4 ,
Some p a r a s i t i c ro u n d w o rm s o f t h e r a b b i t - w i t h
d e s c r i p t i o n s . o f tw o n e w , s p e c i e s .
P r o c . . U. S ; N a t v M us.
66 ( A r t , 1 6 ) : 1 - 6 .
C h i t w o o d , M. B,
1957,
In tra s p e c ific v a ria tio n s
S y s t e m a t i c Z o o l.- 6 : 1 9 - 2 3 .
i n p a ra s itic ._ n e m a to d e s .
C l a n c y , C. F . , E.< J u n g h e r r , a n d P , R. S i m e .
1940.
In te in a l p a ra site s
o f c o t t o n t a i l r a b b i t s i n C o n n e c t i c u t . • J . W i l d l . M g t. 4 ( 2 ) :
162-168.
D in e e n ., J . K. a n d B; M. W a g l a n d .
1 9 6 6 . ' T he d y n a m i c s o f - t h e h o s t p a ra s ite re la tio n s h ip .
V.
E v id en ce f o r im m u n o lo g ica l e x h a u s tio n
i n . s h e e p , e x p e r i m e n t a l l y i n f e c t e d w i t h Haemonehus eo n to vtu s.
P a ra s ito l.,
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___ I tooa BTES
N378
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c o p .2
9 H I
S a m u e l , Ne I s o n
In tra sp e c ific d iffe re n c e s b etw een c o t t o n t a i
and w oodchuck i s o l a t e s .
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