1976
Jupp et al.:
Culex rubinotiis, virus vector, IV
651
Muspratt, J. 1955. Research on South African Culicini Kokernot, R. H., K. C. Smithburn, H. E. Paterson & (Diptera: Culicidae). III. A check list of the species and B. M. Mcintosh. 1960. Isolation of Germiston virus, a their distribution, with notes on taxonomy, bionomics and hitherto unknown agent, from culicine mosquitoes, and a identification. J. Ent. Soc. S. Afr. 18: 179. report of infection in two laboratory workers. Amer. J. Worth, C. Brooke & Botha de Mcillon. 1960. Culicine Trop. Med. Hyg. 9: 62-69. mosquitoes (Diptera: Culicidae) recorded from the Province Mcintosh, B. M., P. G. Jupp, I. S. L. Dos Santos & G. M. of Mocambique (Portuguese East Africa) and their rela Meenehan. 1976. Culex (Eumelanomyia) rubinotus Theo tionship to arthropod-borne viruses. Anais Inst. Med. Trop. bald as vector of Banzi, Germiston and Witwatersrand 17: 231-56. viruses. I. Isolation of virus from wild populations of C. rubinotus. J. Med. Ent. 12: 637-40.
J. Med. Ent.
20 February 1976
Vol. 12, no. 6: 651-656
1
2
3
3
By D a n i e l E. S o n e n s h i n e , C o n r a d E. Y u n k e r , G a r l e t o n M . C l i f f o r d , G o r d o n M . Clark > a n d J. A. R u d b a c h 3
4
Abstract: Relative abundance of larval Rocky Mountain wood ticks, Dermacentor andersoni Stiles, in mountainous terrain of western Montana was measured by release and recapture of radiolabeled ticks. Laboratory-reared larvae tagged with 14-Carbon or 125-Iodine were released in equal numbers at selected points within 1 of 2 study areas during the natural larval activity periods of 1967-1969. Tagged larvae subsequently recovered on small rodent hosts trapped in these areas and identified provided an estimate of tick population size per acre (ha) (;i:2 S.E.): 119,163 ± 50,864 (294,333 ± 125,633) and 388,622 ± 212,750 (959,896 ± 525,214) in 1967 and 1969, res pectively. Hosts from which most of the ticks were obtained were Neotoma cinerea (40.9% of larvae; 30.6% of nymphs), and Spermophilus lateralis (35.1% of larvae; 60.3% of nymphs). Other hosts were Peromyscus maniculatus (17% of larvae; 4.9% of nymphs), and Eutamias amoenus and E. ruficaudus (7.0% of larvae; 6.6% of nymphs). Larval activity was restricted to a 9- to 11 -week period between mid-June and early September, peaking once in late July or early August. Nymphal activity, already evident when trapping began, remained constant until it declined after mid-August. Labeling of larval ticks by exposure to radioactive iodine vapor appears to be at least as efficient as labeling them through inoculation of ovigerous parents with 14-Carbon.
5
andersoni Stiles ( C o o l e y 1932, P h i l i p 1937, C l a r k et al. 1 9 7 0 ) , little is k n o w n of t h e size of t h e p o p u l a t i o n t h a t c a n be sustained or the e n v i r o n m e n t a l factors affecting it. K n o w l e d g e of v e c t o r - p o p u l a t i o n d y n a m i c s s h o u l d b e a n i n t e g r a l p a r t of r e s e a r c h i n t o t h e e p i z o o t i o l o g y of disease a g e n t s t r a n s m i t t e d b y this tick, especially of R o c k y M o u n t a i n s p o t t e d fever r i c k e t t s i a a n d C o l o r a d o tick fever ( C T F ) v i r u s . Specifically, m o r e i n f o r m a t i o n is n e e d e d o n i m m a t u r e ticks a n d t h e i r s m a l l m a m m a l hosts. The i n t e r c h a n g e of p a t h o g e n s b e t w e e n t h e s e i m m a t u r e stages a n d hosts p r o v i d e s a n i m p o r t a n t m e a n s of s p r e a d of disease a g e n t s as w e l l as t h e r e s e r v o i r for i n f e c t i o n of t h e m a n - b i t i n g a d u l t ticks. W e s t u d i e d t h e r e l a t i v e a b u n d a n c e of i m m a t u r e D. andersoni b y r e l e a s e a n d r e c a p t u r e of r a d i o i s o t o p e t a g g e d i m m a t u r e ticks i n 2 m o u n t a i n o u s a r e a s of w e s t e r n M o n t a n a w h e r e p e r s i s t e n t foci of C T F h a d b e e n identified.
T h o u g h m u c h has been l e a r n e d a b o u t the ecology of
the
Rocky
Mountain
wood
tick,
Dermacentor
'Supported, in part, by a Contract AT-(40-l)-3514, with the Division of Biology and Medicine, U. S. Atomic Energy Com mission, Washington, D. C. 'Biology Department, Old Dominion University, Norfolk, Virginia 23508, U.S.A. U . S. Department of Health, Education, and Welfare, Public Health Service, National Institutes of Health, National Institute of Allergy and Infectious Diseases, Rocky Mountain Laboratory, Hamilton, Montana 59840, U.S.A. Deceased. department of Microbiology, University of Montana, Missoula, Montana 59801, U.S.A.
T h i s s t u d y is p a r t of c o n t i n u i n g
i n v e s t i g a t i o n s of t h e n a t u r a l h i s t o r y of C T F et a l . 1 9 7 0 ) . population
(Clark
D e s c r i b e d h e r e a r e s o m e a s p e c t s of
dynamics
and
host
utilization
of
the
tick v e c t o r . MATERIALS A N D METHODS
3
4
Tagging.
A l l ticks u s e d i n this s t u d y w e r e
D.
andersoni l a r v a e f r o m stocks m a i n t a i n e d a t t h e R o c k y Mountain Laboratory, Hamilton, Montana. were
tagged
with
14-Carbon
by
Most
the m e t h o d
of
S o n e n s h i n e & Y u n k e r (1968) i n v o l v i n g t r a n s o v a r i a l
Downloaded from http://jme.oxfordjournals.org/ by guest on June 6, 2016
CONTRIBUTIONS TO THE ECOLOGY OF COLORADO TICK FEVER VIRUS 2. Population dynamics and host utilization of immature stages of the Rocky Mountain wood tick, Dermacentor andersoni
J. Med. Ent.
652
1 2 5
Radioassay.
Larval
ticks
collected
from
host
a n i m a l s w e r e i d e n t i f i e d a n d l a r v a l D. andersoni w e r e t e s t e d for e v i d e n c e of r a d i o a c t i v i t y .
Controls held
i n t h e field a n d i n t h e l a b o r a t o r y w e r e also a s s a y e d . Radioassays were d o n e with a Nuclear Chicago gas flow d e t e c t o r ( m o d e l 4 7 0 ) a n d d e c a d e s c a l e r ( m o d e l 8 1 6 6 ) t o d e t e r m i n e t h e p r e s e n c e of 14-C l a b e l i n g . I n 1969, t h e s e
field-collected
a n d control specimens
w e r e also t e s t e d w i t h a N u c l e a r C h i c a g o solid scintil lation spectrometer (model DS-5), radiation analyzer a n d d e c a d e scaler (model N o . 1810). Field studies.
FIG. 1. Mill Canyon study area. In 1967, ticks marked with 14-Carbon were released only in 10 contiguous squares of trapping grid C at 108 locations. Five live traps were set at each intersect of grids B and C. Population estimate was based on collections in grid C only. r e l e a s e d i n t e n 2 3 - m c o n t i g u o u s s q u a r e s of a r e a C . W i t h i n the squares, 200 m a r k e d larvae were released at
each
of
108 e q u i d i s t a n t
points.
adjacent
t r a p p i n g g r i d (FIG. 1, a r e a B) w a s u s e d as a c o n t r o l t o m o n i t o r t h e d i s p e r s a l of t a g g e d l a r v a e . I n 1968, a n e w s t u d y a r e a w a s s e l e c t e d i n R o a r i n g L i o n C a n y o n (FIG. 2). t h a t of M i l l C a n y o n [±34°] )
}
W
This area, very similar to ( a l t h o u g h its s l o p e w a s less
a s used in the ensuing 2 years.
Inter
sects w e r e l o c a t e d a t 2 0 - m i n t e r v a l s o n b o u l d e r s o r i n t h e b r u s h of t h e c a n y o n s l o p e .
These were done during the summer
An
R e l e a s e of t h e
t a g g e d ticks w a s d o n e o n l y i n a n a r e a of 0.36 h a
of 1 9 6 7 - 1 9 6 9 o n t h e n o r t h w a l l s of 2 c a n y o n s of t h e
( i d e n t i f i e d b y t h e d o t t e d lines i n FIG. 2 a n d 3).
Bitterroot
before, a control grid was located n e a r b y .
Mountains
in
Ravalli
County,
near
As 3
J u l y 1968, 16,200 14-C l a b e l e d l a r v a e w e r e r e l e a s e d
Hamilton, Montana. In
On
1967, field s t u d i e s w e r e d o n e i n 2
sites i n M i l l C a n y o n .
trapping
This habitat, described a n d
i n b a t c h e s of 2 0 0 a t 9 e q u i d i s t a n t p o i n t s i n e a c h of the 9 innermost squares formed
by the
trapping
i l l u s t r a t e d b y C l a r k e t a l . ( 1 9 7 0 ) , is a m i x t u r e of
intersects.
t u m b l e d b o u l d e r s a n d loose t a l u s i n t e r s p e r s e d w i t h
ticks w e r e r e l e a s e d a t a d e n s i t y of 2 0 0 l a r v a e / p o i n t
scattered
(total = 20,250).
average
trees,
primarily
s l o p e is 4 2 ° .
In
Ponderosa places, a
pines.
Its
considerable
i n t e r m e d i a t e v e g e t a t i v e c a n o p y is f o r m e d of Acer,
S i m i l a r l y , o n 19 J u l y 1969, 14-C l a b e l e d A t this t i m e , a l s o , 125-1 t a g g e d
larvae were released at the same points at a density of 1 0 0 / p o i n t ( t o t a l =
8100).
Vaccinium.
Also,
S m a l l m a m m a l h o s t s of D. andersoni w e r e t r a p p e d
t h e r e is a s c a t t e r e d l o w e r c a n o p y of Ribes,
Rubus,
w i t h live b o x t r a p s of w o o d o r m e t a l c o n s t r u c t i o n .
Prunus, Rosa
Amelanchier,
and
Berberís.
Spirea
and
Radioecological
investigations
In
1967, t h r e e 7.5 c m
X
15 c m
X 25 c m X 50 c m
metal
t r a p s a n d t w o 15 c m
l e d g e n e a r t h e r i m of t h e c a n y o n w a l l (FIG. 1, a r e a
traps were baited with peanut butter a n d
C).
o a t s a n d set a t e a c h i n t e r s e c t of a r e a s B a n d C .
O n 19 J u l y , 2 1 , 6 0 0 14-C l a b e l e d l a r v a e w e r e
X
7.5 c m
w e r e d o n e i n a n a r e a of a b o u t 0 . 5 4 h a o n a r o c k y
wooden rolled In
Downloaded from http://jme.oxfordjournals.org/ by guest on June 6, 2016
t r a n s f e r of r a d i o l a b e l e d m e t a b o l i t e s ( 1 4 - C l a b e l e d g l u c o s e w a s u s e d i n this s t u d y ) f r o m p a r e n t f e m a l e s to progeny. T a g g e d larvae were assayed a n d those r e g a r d e d as s u i t a b l y l a b e l e d w e r e s e l e c t e d for r e l e a s e i n t h e field (see S o n e n s h i n e & C l a r k 1968 for a r e v i e w of s e l e c t i o n c r i t e r i a ) . T h e t a g g e d ticks w e r e a s s a y e d i n lots a n d t h o s e lots w i t h a v e r a g e c o u n t s a t least 2 0 0 - 3 0 0 p e r m i n . a b o v e b a c k g r o u n d w e r e s e l e c t e d for r e l e a s e . A l s o , i n a n e x p e r i m e n t a l t r i a l ( 1 9 6 9 o n l y ) , s o m e l a r v a e w e r e t a g g e d w i t h 125-1 b y exposure to radioactive iodine vapors a n d were released a l o n g w i t h those tagged with 14-C. This w a s d o n e i n t h e b e l i e f t h a t 125-1 w o u l d b i n d w i t h c u t i c u l a r p r o t e i n ( O ' B r i e n & W o l f e 1964). The ticks w e r e l a b e l e d w i t h 125-1 b y t h e diffusion m e t h o d described b y G r u b e r & W r i g h t ( 1 9 6 7 ) . Briefly, ticks w e r e c o u n t e d a n d d i s t r i b u t e d a m o n g o p e n e n d e d glass t u b e s , w h i c h w e r e s t o p p e r e d w i t h silkmesh. T u b e s were placed in a v a c u u m desiccator j a r w h e r e u p o n iodine vapors were released from lOmCi KI b y t h e a d d i t i o n of a n a p p r o p r i a t e a m o u n t of a c i d d i c h r o m a t e s o l u t i o n . L a b e l i n g w a s a l l o w e d t o c o n t i n u e for 18 h r a t r o o m t e m p e r a t u r e . U n c o n j u g a t e d 125-1 w a s r e m o v e d f r o m t h e s y s t e m b y flushing w i t h a i r i n t o a n a l k a l i n e bisulfate t r a p .
Vol. 12, no. 6
Sonenshine et al.:
15176
653
Ecology of Colorado tick fever virus
pies w e r e r e m o v e d o n s e l e c t e d d a t e s t h e r e a f t e r , a n d s u r v i v i n g l a r v a e w e r e c o u n t e d a n d a s s a y e d for p e r s i s t e n c e of r a d i o a c t i v i t y . L a b e l e d a n d u n l a b e l e d l a r v a e w e r e also h e l d i n t h e l a b o r a t o r y t o d e t e r m i n e t h e effect of t h e n u c l i d e o n s u r v i v a l of ticks. RESULTS
1968 a n d 1969, 2 m e t a l a n d 1 w o o d e n t r a p s w e r e u s e d a t e a c h i n t e r s e c t of b o t h g r i d s . T r a p s w e r e set a t w e e k l y i n t e r v a l s i n a f t e r n o o n s a n d c h e c k e d the following m o r n i n g s . C a p t u r e d animals were identified a n d m a r k e d with n u m b e r e d e a r tags. A g e , sex a n d w e i g h t w e r e r e c o r d e d a n d i n f r a o r b i t a l blood samples a n d ectoparasites were collected. B l o o d s a m p l e s w e r e d i l u t e d 1: 10 i n n o r m a l s a l i n e containing 5 0 % normal rabbit serum a n d antibiotics a n d i m m e d i a t e l y f r o z e n i n s t y r o f o a m b o x e s c o n t a i n i n g solid C 0 . T h e animals were released a t t h e i r c a p t u r e sites i m m e d i a t e l y t h e r e a f t e r u n l e s s heavily parasitized. I n t h e l a t t e r case t h e y w e r e transported to the laboratory a n d thoroughly d i v e s t e d of p a r a s i t e s ; t h e f o l l o w i n g d a y t h e y w e r e r e t u r n e d to the study a r e a a n d released at their c a p t u r e sites. T i c k s w e r e h e l d for r a d i o a s s a y a n d subsequent virus isolation a t t e m p t s . 2
N o loss of r a d i o a c t i v i t y w a s o b s e r v e d a m o n g live, t a g g e d ticks h e l d i n s u r v i v a l c o n t a i n e r s , e i t h e r i n t h e field o r i n t h e l a b o r a t o r y . Population dynamics of larvae and nymphs. In both s t u d y a r e a s a n d i n all 3 y e a r s , l a r v a l h o s t - s e e k i n g activity w a s restricted to a 9- to 11-week period, w h i c h o c c u r r e d from m i d - J u n e t h r o u g h early September (FIG. 4 ) . P e a k s o c c u r r e d i n early A u g u s t (1967) a n d m i d - t o l a t e - J u l y ( 1 9 6 8 a n d 1969). N y m p h a l host-seeking activity e x t e n d e d over a m u c h longer period t h a t included spring a n d summer. N y m p h a l activity, already evident w h e n t r a p p i n g b e g a n e a c h y e a r (in 1 y e a r as e a r l y as A p r i l ) , c o n t i n u e d a t a r e l a t i v e l y c o n s t a n t level a n d finally d e c l i n e d after m i d - A u g u s t .
1
¿ g ^ 4 í * 9 S f c ^
o
o
Jupp et al.:
Culex rubinotiis, virus vector, IV
651
Muspratt, J. 1955. Research on South African Culicini Kokernot, R. H., K. C. Smithburn, H. E. Paterson & (Diptera: Culicidae). III. A check list of the species and B. M. Mcintosh. 1960. Isolation of Germiston virus, a their distribution, with notes on taxonomy, bionomics and hitherto unknown agent, from culicine mosquitoes, and a identification. J. Ent. Soc. S. Afr. 18: 179. report of infection in two laboratory workers. Amer. J. Worth, C. Brooke & Botha de Mcillon. 1960. Culicine Trop. Med. Hyg. 9: 62-69. mosquitoes (Diptera: Culicidae) recorded from the Province Mcintosh, B. M., P. G. Jupp, I. S. L. Dos Santos & G. M. of Mocambique (Portuguese East Africa) and their rela Meenehan. 1976. Culex (Eumelanomyia) rubinotus Theo tionship to arthropod-borne viruses. Anais Inst. Med. Trop. bald as vector of Banzi, Germiston and Witwatersrand 17: 231-56. viruses. I. Isolation of virus from wild populations of C. rubinotus. J. Med. Ent. 12: 637-40.
J. Med. Ent.
20 February 1976
Vol. 12, no. 6: 651-656
1
2
3
3
By D a n i e l E. S o n e n s h i n e , C o n r a d E. Y u n k e r , G a r l e t o n M . C l i f f o r d , G o r d o n M . Clark > a n d J. A. R u d b a c h 3
4
Abstract: Relative abundance of larval Rocky Mountain wood ticks, Dermacentor andersoni Stiles, in mountainous terrain of western Montana was measured by release and recapture of radiolabeled ticks. Laboratory-reared larvae tagged with 14-Carbon or 125-Iodine were released in equal numbers at selected points within 1 of 2 study areas during the natural larval activity periods of 1967-1969. Tagged larvae subsequently recovered on small rodent hosts trapped in these areas and identified provided an estimate of tick population size per acre (ha) (;i:2 S.E.): 119,163 ± 50,864 (294,333 ± 125,633) and 388,622 ± 212,750 (959,896 ± 525,214) in 1967 and 1969, res pectively. Hosts from which most of the ticks were obtained were Neotoma cinerea (40.9% of larvae; 30.6% of nymphs), and Spermophilus lateralis (35.1% of larvae; 60.3% of nymphs). Other hosts were Peromyscus maniculatus (17% of larvae; 4.9% of nymphs), and Eutamias amoenus and E. ruficaudus (7.0% of larvae; 6.6% of nymphs). Larval activity was restricted to a 9- to 11 -week period between mid-June and early September, peaking once in late July or early August. Nymphal activity, already evident when trapping began, remained constant until it declined after mid-August. Labeling of larval ticks by exposure to radioactive iodine vapor appears to be at least as efficient as labeling them through inoculation of ovigerous parents with 14-Carbon.
5
andersoni Stiles ( C o o l e y 1932, P h i l i p 1937, C l a r k et al. 1 9 7 0 ) , little is k n o w n of t h e size of t h e p o p u l a t i o n t h a t c a n be sustained or the e n v i r o n m e n t a l factors affecting it. K n o w l e d g e of v e c t o r - p o p u l a t i o n d y n a m i c s s h o u l d b e a n i n t e g r a l p a r t of r e s e a r c h i n t o t h e e p i z o o t i o l o g y of disease a g e n t s t r a n s m i t t e d b y this tick, especially of R o c k y M o u n t a i n s p o t t e d fever r i c k e t t s i a a n d C o l o r a d o tick fever ( C T F ) v i r u s . Specifically, m o r e i n f o r m a t i o n is n e e d e d o n i m m a t u r e ticks a n d t h e i r s m a l l m a m m a l hosts. The i n t e r c h a n g e of p a t h o g e n s b e t w e e n t h e s e i m m a t u r e stages a n d hosts p r o v i d e s a n i m p o r t a n t m e a n s of s p r e a d of disease a g e n t s as w e l l as t h e r e s e r v o i r for i n f e c t i o n of t h e m a n - b i t i n g a d u l t ticks. W e s t u d i e d t h e r e l a t i v e a b u n d a n c e of i m m a t u r e D. andersoni b y r e l e a s e a n d r e c a p t u r e of r a d i o i s o t o p e t a g g e d i m m a t u r e ticks i n 2 m o u n t a i n o u s a r e a s of w e s t e r n M o n t a n a w h e r e p e r s i s t e n t foci of C T F h a d b e e n identified.
T h o u g h m u c h has been l e a r n e d a b o u t the ecology of
the
Rocky
Mountain
wood
tick,
Dermacentor
'Supported, in part, by a Contract AT-(40-l)-3514, with the Division of Biology and Medicine, U. S. Atomic Energy Com mission, Washington, D. C. 'Biology Department, Old Dominion University, Norfolk, Virginia 23508, U.S.A. U . S. Department of Health, Education, and Welfare, Public Health Service, National Institutes of Health, National Institute of Allergy and Infectious Diseases, Rocky Mountain Laboratory, Hamilton, Montana 59840, U.S.A. Deceased. department of Microbiology, University of Montana, Missoula, Montana 59801, U.S.A.
T h i s s t u d y is p a r t of c o n t i n u i n g
i n v e s t i g a t i o n s of t h e n a t u r a l h i s t o r y of C T F et a l . 1 9 7 0 ) . population
(Clark
D e s c r i b e d h e r e a r e s o m e a s p e c t s of
dynamics
and
host
utilization
of
the
tick v e c t o r . MATERIALS A N D METHODS
3
4
Tagging.
A l l ticks u s e d i n this s t u d y w e r e
D.
andersoni l a r v a e f r o m stocks m a i n t a i n e d a t t h e R o c k y Mountain Laboratory, Hamilton, Montana. were
tagged
with
14-Carbon
by
Most
the m e t h o d
of
S o n e n s h i n e & Y u n k e r (1968) i n v o l v i n g t r a n s o v a r i a l
Downloaded from http://jme.oxfordjournals.org/ by guest on June 6, 2016
CONTRIBUTIONS TO THE ECOLOGY OF COLORADO TICK FEVER VIRUS 2. Population dynamics and host utilization of immature stages of the Rocky Mountain wood tick, Dermacentor andersoni
J. Med. Ent.
652
1 2 5
Radioassay.
Larval
ticks
collected
from
host
a n i m a l s w e r e i d e n t i f i e d a n d l a r v a l D. andersoni w e r e t e s t e d for e v i d e n c e of r a d i o a c t i v i t y .
Controls held
i n t h e field a n d i n t h e l a b o r a t o r y w e r e also a s s a y e d . Radioassays were d o n e with a Nuclear Chicago gas flow d e t e c t o r ( m o d e l 4 7 0 ) a n d d e c a d e s c a l e r ( m o d e l 8 1 6 6 ) t o d e t e r m i n e t h e p r e s e n c e of 14-C l a b e l i n g . I n 1969, t h e s e
field-collected
a n d control specimens
w e r e also t e s t e d w i t h a N u c l e a r C h i c a g o solid scintil lation spectrometer (model DS-5), radiation analyzer a n d d e c a d e scaler (model N o . 1810). Field studies.
FIG. 1. Mill Canyon study area. In 1967, ticks marked with 14-Carbon were released only in 10 contiguous squares of trapping grid C at 108 locations. Five live traps were set at each intersect of grids B and C. Population estimate was based on collections in grid C only. r e l e a s e d i n t e n 2 3 - m c o n t i g u o u s s q u a r e s of a r e a C . W i t h i n the squares, 200 m a r k e d larvae were released at
each
of
108 e q u i d i s t a n t
points.
adjacent
t r a p p i n g g r i d (FIG. 1, a r e a B) w a s u s e d as a c o n t r o l t o m o n i t o r t h e d i s p e r s a l of t a g g e d l a r v a e . I n 1968, a n e w s t u d y a r e a w a s s e l e c t e d i n R o a r i n g L i o n C a n y o n (FIG. 2). t h a t of M i l l C a n y o n [±34°] )
}
W
This area, very similar to ( a l t h o u g h its s l o p e w a s less
a s used in the ensuing 2 years.
Inter
sects w e r e l o c a t e d a t 2 0 - m i n t e r v a l s o n b o u l d e r s o r i n t h e b r u s h of t h e c a n y o n s l o p e .
These were done during the summer
An
R e l e a s e of t h e
t a g g e d ticks w a s d o n e o n l y i n a n a r e a of 0.36 h a
of 1 9 6 7 - 1 9 6 9 o n t h e n o r t h w a l l s of 2 c a n y o n s of t h e
( i d e n t i f i e d b y t h e d o t t e d lines i n FIG. 2 a n d 3).
Bitterroot
before, a control grid was located n e a r b y .
Mountains
in
Ravalli
County,
near
As 3
J u l y 1968, 16,200 14-C l a b e l e d l a r v a e w e r e r e l e a s e d
Hamilton, Montana. In
On
1967, field s t u d i e s w e r e d o n e i n 2
sites i n M i l l C a n y o n .
trapping
This habitat, described a n d
i n b a t c h e s of 2 0 0 a t 9 e q u i d i s t a n t p o i n t s i n e a c h of the 9 innermost squares formed
by the
trapping
i l l u s t r a t e d b y C l a r k e t a l . ( 1 9 7 0 ) , is a m i x t u r e of
intersects.
t u m b l e d b o u l d e r s a n d loose t a l u s i n t e r s p e r s e d w i t h
ticks w e r e r e l e a s e d a t a d e n s i t y of 2 0 0 l a r v a e / p o i n t
scattered
(total = 20,250).
average
trees,
primarily
s l o p e is 4 2 ° .
In
Ponderosa places, a
pines.
Its
considerable
i n t e r m e d i a t e v e g e t a t i v e c a n o p y is f o r m e d of Acer,
S i m i l a r l y , o n 19 J u l y 1969, 14-C l a b e l e d A t this t i m e , a l s o , 125-1 t a g g e d
larvae were released at the same points at a density of 1 0 0 / p o i n t ( t o t a l =
8100).
Vaccinium.
Also,
S m a l l m a m m a l h o s t s of D. andersoni w e r e t r a p p e d
t h e r e is a s c a t t e r e d l o w e r c a n o p y of Ribes,
Rubus,
w i t h live b o x t r a p s of w o o d o r m e t a l c o n s t r u c t i o n .
Prunus, Rosa
Amelanchier,
and
Berberís.
Spirea
and
Radioecological
investigations
In
1967, t h r e e 7.5 c m
X
15 c m
X 25 c m X 50 c m
metal
t r a p s a n d t w o 15 c m
l e d g e n e a r t h e r i m of t h e c a n y o n w a l l (FIG. 1, a r e a
traps were baited with peanut butter a n d
C).
o a t s a n d set a t e a c h i n t e r s e c t of a r e a s B a n d C .
O n 19 J u l y , 2 1 , 6 0 0 14-C l a b e l e d l a r v a e w e r e
X
7.5 c m
w e r e d o n e i n a n a r e a of a b o u t 0 . 5 4 h a o n a r o c k y
wooden rolled In
Downloaded from http://jme.oxfordjournals.org/ by guest on June 6, 2016
t r a n s f e r of r a d i o l a b e l e d m e t a b o l i t e s ( 1 4 - C l a b e l e d g l u c o s e w a s u s e d i n this s t u d y ) f r o m p a r e n t f e m a l e s to progeny. T a g g e d larvae were assayed a n d those r e g a r d e d as s u i t a b l y l a b e l e d w e r e s e l e c t e d for r e l e a s e i n t h e field (see S o n e n s h i n e & C l a r k 1968 for a r e v i e w of s e l e c t i o n c r i t e r i a ) . T h e t a g g e d ticks w e r e a s s a y e d i n lots a n d t h o s e lots w i t h a v e r a g e c o u n t s a t least 2 0 0 - 3 0 0 p e r m i n . a b o v e b a c k g r o u n d w e r e s e l e c t e d for r e l e a s e . A l s o , i n a n e x p e r i m e n t a l t r i a l ( 1 9 6 9 o n l y ) , s o m e l a r v a e w e r e t a g g e d w i t h 125-1 b y exposure to radioactive iodine vapors a n d were released a l o n g w i t h those tagged with 14-C. This w a s d o n e i n t h e b e l i e f t h a t 125-1 w o u l d b i n d w i t h c u t i c u l a r p r o t e i n ( O ' B r i e n & W o l f e 1964). The ticks w e r e l a b e l e d w i t h 125-1 b y t h e diffusion m e t h o d described b y G r u b e r & W r i g h t ( 1 9 6 7 ) . Briefly, ticks w e r e c o u n t e d a n d d i s t r i b u t e d a m o n g o p e n e n d e d glass t u b e s , w h i c h w e r e s t o p p e r e d w i t h silkmesh. T u b e s were placed in a v a c u u m desiccator j a r w h e r e u p o n iodine vapors were released from lOmCi KI b y t h e a d d i t i o n of a n a p p r o p r i a t e a m o u n t of a c i d d i c h r o m a t e s o l u t i o n . L a b e l i n g w a s a l l o w e d t o c o n t i n u e for 18 h r a t r o o m t e m p e r a t u r e . U n c o n j u g a t e d 125-1 w a s r e m o v e d f r o m t h e s y s t e m b y flushing w i t h a i r i n t o a n a l k a l i n e bisulfate t r a p .
Vol. 12, no. 6
Sonenshine et al.:
15176
653
Ecology of Colorado tick fever virus
pies w e r e r e m o v e d o n s e l e c t e d d a t e s t h e r e a f t e r , a n d s u r v i v i n g l a r v a e w e r e c o u n t e d a n d a s s a y e d for p e r s i s t e n c e of r a d i o a c t i v i t y . L a b e l e d a n d u n l a b e l e d l a r v a e w e r e also h e l d i n t h e l a b o r a t o r y t o d e t e r m i n e t h e effect of t h e n u c l i d e o n s u r v i v a l of ticks. RESULTS
1968 a n d 1969, 2 m e t a l a n d 1 w o o d e n t r a p s w e r e u s e d a t e a c h i n t e r s e c t of b o t h g r i d s . T r a p s w e r e set a t w e e k l y i n t e r v a l s i n a f t e r n o o n s a n d c h e c k e d the following m o r n i n g s . C a p t u r e d animals were identified a n d m a r k e d with n u m b e r e d e a r tags. A g e , sex a n d w e i g h t w e r e r e c o r d e d a n d i n f r a o r b i t a l blood samples a n d ectoparasites were collected. B l o o d s a m p l e s w e r e d i l u t e d 1: 10 i n n o r m a l s a l i n e containing 5 0 % normal rabbit serum a n d antibiotics a n d i m m e d i a t e l y f r o z e n i n s t y r o f o a m b o x e s c o n t a i n i n g solid C 0 . T h e animals were released a t t h e i r c a p t u r e sites i m m e d i a t e l y t h e r e a f t e r u n l e s s heavily parasitized. I n t h e l a t t e r case t h e y w e r e transported to the laboratory a n d thoroughly d i v e s t e d of p a r a s i t e s ; t h e f o l l o w i n g d a y t h e y w e r e r e t u r n e d to the study a r e a a n d released at their c a p t u r e sites. T i c k s w e r e h e l d for r a d i o a s s a y a n d subsequent virus isolation a t t e m p t s . 2
N o loss of r a d i o a c t i v i t y w a s o b s e r v e d a m o n g live, t a g g e d ticks h e l d i n s u r v i v a l c o n t a i n e r s , e i t h e r i n t h e field o r i n t h e l a b o r a t o r y . Population dynamics of larvae and nymphs. In both s t u d y a r e a s a n d i n all 3 y e a r s , l a r v a l h o s t - s e e k i n g activity w a s restricted to a 9- to 11-week period, w h i c h o c c u r r e d from m i d - J u n e t h r o u g h early September (FIG. 4 ) . P e a k s o c c u r r e d i n early A u g u s t (1967) a n d m i d - t o l a t e - J u l y ( 1 9 6 8 a n d 1969). N y m p h a l host-seeking activity e x t e n d e d over a m u c h longer period t h a t included spring a n d summer. N y m p h a l activity, already evident w h e n t r a p p i n g b e g a n e a c h y e a r (in 1 y e a r as e a r l y as A p r i l ) , c o n t i n u e d a t a r e l a t i v e l y c o n s t a n t level a n d finally d e c l i n e d after m i d - A u g u s t .
1
¿ g ^ 4 í * 9 S f c ^
o
o
