Susceptibility of Two Rocky Mountain Bighorn Sheep to Experimental Infection with Anaplasma ovis Author(s): Todd Tibbitts, Will Goff, William Foreyt, and David Stiller Source: Journal of Wildlife Diseases, 28(1):125-129. Published By: Wildlife Disease Association DOI: http://dx.doi.org/10.7589/0090-3558-28.1.125 URL: http://www.bioone.org/doi/full/10.7589/0090-3558-28.1.125
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Journal
of Wildlife
Diseases,
28(1),
© Wildlife
Susceptibility
of Two
Rocky
Experimental
Infection
Mountain
Bighorn
with Anaplasma
Sheep
pp. 125-129 Association 1992
1992,
Disease
to
ovis
Todd Tibbitts, Will Goff,24 William Foreyt,’ and David Stiller,3 Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman, Washington 99164, USA; 2 United States Department of Agriculture, Agricultural Research Service, Animal Disease Research Unit, Pullman, Washington 99164, USA; United States Department of Agriculture, Agricultural Research Service, Animal Disease Research Unit, Moscow, Idaho 83843, USA; Author to whom allcorrespondence should be addressed
In
ABSTRACT:
ruminants has
in
not
North
the
been
America,
clearly
is particularly
the
epidemiology defined.
meager
role
of
of
anaplasmosis
Such
information
in regard
to bighorn
from
bighorn
sheep
severe
with
and
tetracycline
sheep
while
were
ciated that
mild
bighorn
if exposed
words: sheep,
ceptibility,
other
infection.
the
may
in
Anaplasmosis
is an
infectious,
occurs
by passage
accidents
(Blood
et al.,
placental
transfer
has
terized orexia
(Zaugg, domestic
by anemia, and possibly
been coileus 1963),
ovis, sus-
been
trans-
margin-
white-tailed
(Odo-
deer
(Kreier (Odocoileus
and Ristic, hemionus)
and pronghorn americana) (Zaugg,
apparently
have
not
been
antelope 1987a), attempted Howe A. sheep, equiv-
Since bighorn sheep and domestic livestock share habitat in certain regions of the United States, it is important to deter-
ex-
Infection of is charac-
depression, (Weinman
of A. 1956).
in bighorn sheep (Ovis canadensis). et al. (1964) attempted experimental marginale infection of two bighorn but technical weaknesses produced ocal results.
by the spp.
of infected
observed
1987b). ruminants icterus, death
but
course et al.,
have cattle
virginianus) mule deer 1988),
in spleen-intact usually results in in sheep, reflect-
A. ovis infections in splenectomized
1981),
(Zaugg, (Antilocapra
noncon-
Also,
described
(Kuttler,
via ticks, bitand iatrogenic
1979).
more the clinical in cattle (Splitter Experimental
asso-
indicate affected
caused Anaplasrna
blood to susceptible animals ing flies, blood transfers,
perimentally susceptible
A.
in is
infection.
tagious disease of ruminants hematropic rickettsiae, Transmission
that
Ana plasma canadensis,
canadensis
experimental
ing ale
nature.
Anaplasmosis,
Ovis
un-
(Kimcan be
produced in splenectom(Magonigle et al., 1981). Inter-
A. ovis infection or splenectomized goats more severe disease than
bighorn
typically
in sheep anaplasmosis
estingly,
re-
recovered
The results be adversely
organism
experimentally ized sheep
well
Both
sheep
sheep to
animal
a condition
domestic with
Key bighorn
the treatment.
berling,
par-
responded
anaplasmosis 1988). Acute
subclinical
in
high
One and
spleen-intact,
ovis-exposed
resulting
anemia.
without
Rocky cana well ovis Both
Idaho.
relatively
therapy
treatment,
eventfully
in
infection
disease, icterus
quired
sheep
developed
clinical
asitemias, to
domestic
in concert with intercurrent diseases (Kimberling, 1988). However, decreased live weight of market animals due to suboptimal gains is common and accompanies
sheep.
We report the susceptibility of two Mountain bighorn sheep (Ovis canadensis adensis) to experimental infection with characterized field isolate of Anaplasrna obtained
wild
mine the potential role of bighorn sheep as reservoirs of anaplasms. A prerequisite to such investigations is knowledge of bighorn sheep susceptibility to Ana plasma sp.
anand
Ristic, 1968). The two Ana plasma spp. of importance to livestock in the United States are A. marginale of cattle and A. ovis of sheep and goats. Ana plasma marginale infection in susceptible cattle produces clinical dis-
infection. The was to determine horn sheep A. ovis.
purpose the
to experimental
Two spleen-intact horn sheep were A 7-mo-old male
ease (Blood et al., 1979), while A. ovis infection in domestic sheep is usually subclinical, with signs of infection exhibited
female 125
(On)
of this experiment susceptibility of big-
were
infection
with
Rocky Mountain bigused in this experiment. (Wh717) and 13-mo-old obtained
as
wild
ani-
JOURNAL
126
OF WILDLIFE
mals.
Each
other
bighorn
DISEASES,
was
animal sheep
(USDA-ARS,
VOL.
28, NO.
maintained
in an
Animal
with
outdoor
Disease
rum samples. as previously with some
facility Research
Each salt
animal was provided water, and high quality alfalfa hay
and alfalfa pellets. oculated on separate both
were
housed
indoors
the inoculations was caught and hood
placed
animal restraint of the ulation
Each animal occasions for
was inhowever,
3 wk
over
the
head
to
(PBS). The containing (Fraction
before
were done. Each animal restrained by hand and settle
a
the
before sampling. Preinoculation and sampling was done once each 3 wks before inoculation. Preinocblood samples were collected for
serology,
preparation
and
examination
of
Giemsa-stained blood smears, and determination of packed cell volume (PCV). The A. ovis stabilate represented an isolate obtained by feeding adult Derrnacentor andersoni plasma sp. the
field
periment USA) (Stiller domestic
ticks seropositive at
used.
United
Station (Dubois, on a susceptible et a!., 1989). When sheep developed
parasitemia, bilate (1972),
the
collected domestic
blood
preparation and stored Both
was
States
from Anasheep in Sheep
for sta-
as described by in liquid nitrogen
bighorn
sheep
Ex-
Idaho 83423, domestic sheep the susceptible an ascending collected
were
Love until
inoculated
intravenously with the A. ovis blood stabilate containing 2 x 10 infected erythrocytes per inoculum. After inoculation, blood
samples
serology, evaluation
were
taken
determination of Giemsa-stained
twice of
weekly
for
PCV and the blood smears
to determine the percent parasitized erythrocytes (PPE). Following blood smear detection of Ana plasma sp. bodies, blood samples were collected daily and processed as previously described. The animals were observed daily for anorexia and icterus. An indirect immunofluorescence nique (IIF) Ana plasma
was sp.
used for antibodies
depression,
the detection in bighorn
The IIF described modifications.
procedure was done (Goff et a!., 1985) Briefly, the A.
ovis antigen was prepared by washing infected domestic sheep red blood cells (RBC’s) four times at 400 x G in phosphate buffered saline (0.15 M NaCl, 10 mM Na2HPO4, 3 mM KH2PO4, pH 7.2)
Unit, Pullman, Washington 99164, USA) for approximately 3 mo before moving each to an individual indoor isolation facility. mineral
1992
1, JANUARY
aration slides RBC’s. and with to
pellet was resuspended 1% bovine serum V) to a PCV of 20%
.
in PBS albumin This prep-
was applied to glass microscope to produce a thin smear of infected The slides were air dried, covered, stored at -70 C. Before incubation test serum, the slides were warmed
room
and
temperature
in
a desiccator
jar
fixed
in cold acetone. Recombinant protein-G conjugated with fluorescein isothiocyanate (Zymed, San Francisco, California 94080, USA), diluted 1:80 in PBS was used to detect specific IgG. It was determined electrophoresis G would Tibbitts,
by
gel
that bind unpubl.
diffusion and recombinant
immunoprotein-
IgG of bighorn obs.). Positive
ative IIF control A. avis-infected
sheep (T. and neg-
sera were obtained and naive domestic
from sheep,
respectively. A dilution of the positive trol serum that consistently produced weak reaction was used as a reference.
of Se-
a A
1/100 dilution of the same serum and a negative control serum, along with the weak positive reference dilution were applied were
to each initially
antigen screened
slide. All at a 1/100
and titers of all positive sera following 2-fold serial dilutions. was defined as any reaction positive control. Preinoculation bighorn sheep plasma oculation PCV’s
=
determined A positive the weak
serum samples from were IIF negative.
sp. bodies were blood smears (On
test sera dilution
50,
Wh717
Kradel,
=
53)
were
conbigand
1970).
Both
with
both Ana-
not seen in preinand preinoculation
sidered to be within normal limits for horn sheep (Franzmann, 1970; Woolf
tech-
con-
bighorn
A. ovis.
The
sheep became prepatent period
infected was 20
SHORT
because the to Anaplasma
SO
25
SO
20
#{163}and I0
10
,o
20
30
40
50
animals
SO
Osys Post-Inoculation
FIGURE
1.
parasitized resulting
ma
from
ovis.
21
volume
(PPE)
5,
D-D,
tively typical patent
cell
experimental
S
Wh717;
and
Packed
erythrocytes
for
On;
for Or!;
in
days
two
On
percent sheep
Anaplas-
with
PCV
-,
PPE
#{149}-#{149},
and
and bighorn
infection
PCV
PPE
(PCV)
from
Wh717,
(Fig. 1). These prepatent for livestock infections, periods of 20-40 days
for
for Wh717.
respec-
noted in experimental wild ruminant infections (Howe et a!., 1964; Kreier and Ristic, 1963; Zaugg, 1987a; Zaugg, 1988). The highest PPE for On was 12 which occurred and
on post-inoculation
for Wh717 30. Both
PID
anemia Wh717,
icterus, with
Pfizer,
New
resolved Both
and lethargy. oxytetracycline York,
without bighorn by
1/20,000 PID 30, asitemia
in both
The
limited Ana
New
studies
plasma
may
(Fig. that
to A.
sp.
be refractory
in
1). been
wild
ruminants
indicate to serious
that
done these clinical
disease (Kuttler, 1984). However, to our knowledge, this is the first study involving bighorn sheep and A. avis. One or a combination of 3 factors may have influenced the severity horn sheep. 2 x 10
of the infections in these bigFirst, the inoculation dose of
A. ovis
in this study was ed to maximize
infected
erythrocytes
used
high. However, we wantthe chances of infection
A.
Roby In
et al.,
1961;
it is dif-
addition,
to determine
the
parasites in blood in a study using marginale
reported erythrocytes
nitrogen
stasus-
infective
in terms from
ti-
of numbers of blood stabi-
there was an inverse retiter and length of time were stored in liquid
(Kliewer
et a!.,
1973).
Second, by necessity,
the
extremely confinement shown that
stressful conditions of indoor and handling. It has been this kind of stress in bighorn
sheep tivity, tisol
lead
have
cattle,
lates. However, lationship between that the stabilates
10017,
20. Peak serum titers of reached on approximately coincided with peak pananimals
of infectious For example,
lished
USA)
1981;
number bilates.
Wh717 was (LA-200,
antibiotic treatment. sheep seroconvented
A. marginale)
(mainly
York
for for
body weight, iv. when the to 9%. The infection of On
PID were which
hosts
26,
was 20 which occurred on animals developed severe
at 25 mg/kg PCV dropped
with
(PID)
(9% PCV, 83% reduction and 19% PCV, 62% reduction
On), treated
ovis
day
(Kuttler,
et al., 1956). if not impossible,
tens were infected
periods are and prehave been
spleen-intact that sple-
animals are more susceptible infection than spleen-intact
Splitter ficult,
ceptible
127
of bighorn sheep was unknown,
we were using is well established
It
nectomized to Anaplasma
20
)
susceptibility sp. infection
because
animals.
SO
COMMUNICATIONS
leads with
to an elevated
(Harlow
increase levels
et a!.,
that
Cohen,
bighorn
1971).
sheep,
son, 1973; this regard,
to,
or
ing domestic have been
can
(Balow In
studies
has
pathogenicity
study
in susceptibility
and
In
involv-
sheep adjusted
captivity. Third, the isolate of A. ovis may been relatively virulent. It is important well characterized, low passage level be used
stress(Hud-
and Hiblen, 1982). be useful to undertake
sheep and bighonn born in, and well
genicity studies. true of previous
et a!.,
involving
as a result of in cortisol levels
Spraker it would
a comparative
be
estab-
It is well
immunosuppression
been demonstrated induced increase
gulates must
accon-
exposure
to immunosuppression
isolates
were, and
in adrenal of serum
1987).
prolonged
sheep unnatural
levels of, glucocorticosteroids
increased 1975;
wild bighorn subjected to
that to, have that field patho-
This typically has not been studies involving wild un-
and Ana plasma spp. This oversight corrected if the role of wildlife
species in Anaplasma accurately assessed. used in this study
epizootiology is to be The blood stabilate was a true field isolate
128
JOURNAL
not
OF WILDLIFE
subjected
to selective
and
passage,
DISEASES,
which period
a prolonged
VOL.
28,
NO.
1, JANUARY
due
pressure
was not maintained of liquid nitrogen
1992
roids:
to for (