Objective—To determine the effects of interleukin
(IL)-1β on matrix synthesis and degradation by chondrocytes
cultured in a 3-dimensional (3-D) gel medium.
Sample Population—Chondrocytes from 7 dogs.
Procedure—Articular chondrocytes were harvested
and cultured in 3-D gel medium alone or with 10 or 20
ng IL-1βml that was added beginning on day 0, 3, 6,
or 9. On days 3, 6, 12, and 20 of 3-D culture, samples
of the liquid medium were evaluated for glycosaminoglycan
(GAG), prostaglandin E2 (PGE2), and
matrix metalloprotease (MMP)-3 content. The 3-D
plug in each well was evaluated for histologic characteristics
of viability, cell morphology, and proteoglycan
staining, immunohistochemically stained for collagen
type II, and spectrophotometrically analyzed for GAG
Results—Significant differences for all variables were
detected between controls and each IL-1β group,
among groups with different IL-1β concentrations, and
among groups with IL-1β added at various time points.
Chondrocytes exposed to IL-1β had loss of GAG,
increased PGE2 and MMP-3 concentrations, and lack
of collagen type-II synthesis. These IL-1β effects
appeared to be time and concentration dependent.
Conclusions—Addition of IL-1β to chondrocytes in 3-
D gel medium results in time- and concentrationdependent
effects on matrix synthesis and degradation
and provides an appropriate in vitro model for
many of the pathophysiologic events associated with
osteoarthritis. (Am J Vet Res 2000;61:766–770)
Procedure—Uninfected CRFK cells or CRFK cells
infected with FHV-1 were cultured in Dulbecco's modified
Eagle's medium or in 1 of 7 test media containing
various concentrations of lysine and arginine. Viral
titer and CRFK growth rate were assessed in each
Results—Media depleted of arginine almost completely
inhibited viral replication, whereas 2.5 or 5.0
µg of arginine/ml of media was associated with a significant
increase in FHV-1 replication. In media with
2.5 µg of arginine/ml, supplementation with 200 or
300 µg of lysine/ml reduced viral replication by 34.2
and 53.9%, respectively. This effect was not seen in
media containing 5.0 µg of arginine/ml. Growth rates
of CRFK cells also were suppressed in media containing
these concentrations of amino acids, but they
were not significantly different from each other.
Conclusions and Clinical Relevance—Arginine
exerts a substantial growth-promoting effect on
FHV-1. Supplementation of viral culture medium with
lysine attenuates this growth-promoting effect in
media containing low concentrations of arginine.
Analysis of data from this study indicates that high
concentrations of lysine reduce in vitro replication of
FHV-1 but only in media containing low concentrations
of arginine. Clinical trials will be necessary to
determine whether supplemental administration of
lysine, with or without arginine restriction, will be useful
in the management of cats with FHV-1 infections.
(Am J Vet Res 2000; 61:1474–1478)
Objectives—To determine the sensitivity of bacteriologic
culture of pooled fecal samples in detecting
Mycobacterium paratuberculosis, compared with bacteriologic
culture of individual fecal samples in dairy
Study Design—Cross-sectional study.
Animals—24 dairy cattle herds.
Procedure—Individual and pooled fecal samples
were submitted for bacteriologic culture, and results
were compared between these groups.
Results—Ninety-four and 88% of pooled fecal samples
that contained feces from at least 1 animal with
high (mean, ≥ 50 colonies/tube) and moderate (mean,
10 to 49 colonies/tube) concentrations of M paratuberculosis,
respectively, were identified by use of
bacteriologic culture of pooled fecal samples.
Prevalences of paratuberculosis determined by bacteriologic
culture of pooled and individual fecal samples
were highly correlated.
Conclusions and Clinical Relevance—Bacteriologic
culture of pooled fecal samples provided a valid and
cost-effective method for the detection of M paratuberculosis
infection in dairy cattle herds and can be
used to estimate prevalence of infection within a
herd. (J Am Vet Med Assoc 2003;223:1022–1025)
Objective—To determine efficacy and safety of a
commercial modified-live canine distemper virus
(CDV) vaccine used for prophylaxis in domestic ferrets.
Animals—Sixteen 16-week-old neutered male ferrets.
Procedures— Equal groups of ferrets were inoculated
subcutaneously at 16 and 20 weeks of age with
saline (0.9% NaCl) solution or a vaccine derived from
the Onderstepoort CDV strain and attenuated in a primate
cell line. Live virulent CDV was administered to
all ferrets intranasally and orally 3 weeks after the second
inoculation. Clinical signs and body weights were
monitored regularly during the study. Blood samples
for serologic examination were drawn prior to each
inoculation, before challenge exposure, and 10, 15,
and 21 days after exposure. Blood samples for
reverse transcriptase polymerase chain reaction (RT-PCR)
were obtained 5 days after the first vaccination,
and 5, 10, 15, and 21 days after challenge exposure.
Results—After challenge exposure, control ferrets
had significantly more clinical signs and weight loss,
compared with vaccinates. All vaccinated ferrets survived,
whereas all control ferrets died. The RT-PCR
assay was successful in detecting CDV in blood and
fresh or formalin-fixed tissues from infected ferrets.
Conclusions and Clinical Relevance—Findings suggest
that the vaccine when given SC to domestic ferrets
as directed is safe and protective against challenge
exposure with virulent CDV. The RT-PCR assay
may simplify detection of CDV in fresh and fixed tissues.
(Am J Vet Res 2001;62:736–740)
To evaluate the efficacy of the 3 major classes of anthelmintics used for the treatment of hookworms in dogs in the US and an extralabel treatment with an FDA-approved product for use in cats in a Labrador kennel with a history of persistent hookworm infections.
22 dogs housed in a single kennel comprised of the following breeds: 19 Labrador Retrievers, 1 English Cocker Spaniel, 1 Chesapeake Bay Retriever, and 1 Boykin Spaniel.
We performed a fecal egg count (FEC) reduction test using 22 dogs that were allocated randomly to 1 of 5 treatment groups: pyrantel pamoate (Pyrantel pamoate suspension), fenbendazole (Safe-Guard suspension 10%), milbemycin oxime (Interceptor), moxidectin plus imidacloprid (Advantage Multi), and emodepside plus praziquantel (Profender topical solution for cats). FEC was performed on samples collected on days 0 and 11.
FEC reductions for the milbemycin oxime, moxidectin plus imidacloprid, and emodepside plus praziquantel groups were 43.9%, 57.4%, and 100%, respectively. The FEC increased following treatment for the pyrantel and fenbendazole groups.
These data demonstrate that the Ancylostoma caninum infecting the dogs in this kennel are highly resistant to all major anthelmintic classes approved for use in dogs in the US but are susceptible to emodepside. This was the first report of multiple anthelmintic drug–resistant A caninum in a dog kennel that does not involve Greyhounds.
Objective—To determine the effect of experimental
infection with bovine viral diarrhea virus (BVDV) on llamas
and their fetuses, evaluate seroprevalence
of BVDV in llamas and alpacas, and genetically characterize
BVDV isolates from llamas.
Animals—4 pregnant llamas for the experimental
infection study and 223 llamas and alpacas for the
Procedure—Llamas (seronegative to BVDV) were
experimentally infected with a llama isolate of BVDV
via nasal aerosolization. After inoculation, blood samples
were collected every other day for 2 weeks; blood
samples were obtained from crias at birth and monthly
thereafter. For the seroprevalence study, blood was
collected from a convenience sample of 223 camelids.
Isolates of BVDV were characterized by reverse transcription-
polymerase chain reaction assay.
Results—Viremia and BVDV-specific antibody
response were detected in the experimentally infected
llamas, but no signs of disease were observed. No
virus was detected in the crias or aborted fetus,
although antibodies were evident in crias after
colostrum consumption. Seroprevalence to BVDV
was 0.9% in llamas and alpacas. Sequences of the
llama BVDV isolates were comparable to known
Conclusions and Clinical Relevance—Findings suggest
that llamas may be infected with BVDV but have
few or no clinical signs. Inoculation of llamas during
gestation did not result in fetal infection or persistent
BVDV infection of crias. Seroprevalence to BVDV in
llamas and alpacas is apparently low. The most likely
source for BVDV infection in camelids may be cattle.
(J Am Vet Med Assoc 2003;223:223–228)
Objective—To determine whether flies can acquire
porcine reproductive and respiratory syndrome virus
(PRRSV) and disperse the virus throughout a designated
Animals—60 four-month-old pigs.
Procedure—On day 0, 28 of 60 pigs were inoculated
with PRRSV MN 30-100 (index variant). On the same
day, 100,000 pupae of ochre-eyed houseflies and
100,000 pupae of red-eyed (wild-type) houseflies
were placed in the swine facility for a release-recapture
study. Flies were recaptured at 2 locations within
the swine facility, 6 locations immediately outside
the facility, and 30 locations 0.4, 0.8, 1.3, 1.7, 1.9, and
2.3 km from the facility. Traps were emptied on days
2, 7, 8, 10, and 14. Samples derived from flies were
tested by use of a polymerase chain reaction assay,
virus DNA was sequenced, and viruses were tested
for infectivity by means of a swine bioassay.
Results—PRRSV RNA homologous to the index
PRRSV was detected in trapped flies collected inside
and immediately outside the facility and from 9 of 48
samples collected at 0.4 km, 8 of 24 samples collected
at 0.8 km, 5 of 24 samples collected at 1.3 km, and
3 of 84 samples collected at > 1.7 km from the facility.
Two samples collected at 0.8 km contained genetically
diverse variants of PRRSV. Swine bioassays
revealed the virus in flies was infectious.
Conclusions and Clinical Relevance—Flies
appeared to become contaminated with PRRSV from
infected pigs and transported the virus ≥ 1.7 km. Flyborn
transmission may explain how PRRSV is seasonally
transported between farms. (Am J Vet Res 2004;65:1284–1292)
Objective—To monitor ovine herpesvirus type 2
(OvHV-2) infection status and the association
between OvHV-2 infection and development of clinical
signs of malignant catarrhal fever (MCF) in cattle.
Animals—30 mature adult cows and 18 cattle submitted
Procedure—Blood and milk samples were collected at
monthly intervals from 30 adult cows for 20 consecutive
months. Nasal and ocular swab specimens were also
collected during months 9 through 20. Polymerase chain
reaction (PCR) assay for detection of OvHV-2 was performed
on blood, milk, nasal swab, and ocular swab
specimens. Competitive inhibition ELISA (CI-ELISA) for
detection of antibodies against MCF viruses was performed
on serum samples obtained prior to study initiation
and monthly during the last 12 months. Tissues
obtained from herdmates without clinical signs of MCF
that were submitted for necropsy were analyzed for
OvHV-2 DNA via PCR assay for possible sites of latency.
Results—Initially, 8 of 30 cows had positive CI-ELISA
results. Seroconversion was detected in 4 cows. Ovine
herpesvirus type 2 DNA was intermittently detected in
blood, milk, nasal secretions, or ocular secretions from
17 of 30 cows. Twenty-one cows had positive CI-ELISA
or PCR assay results. No cattle in the study developed
clinical signs of MCF. Results of PCR assays performed
on tissue samples from 2 of 18 animals submitted for
necropsy were positive for OvHV-2.
Conclusions and Clinical Relevance—OvHV-2 infection
can occur in cattle without concurrent development
of clinical MCF. Ovine herpesvirus type 2 DNA
was detected intermittently, suggesting fluctuating
viral DNA loads or reinfection in subclinical cattle. A
definitive site of latency was not identified from tissues
obtained during necropsy. (J Am Vet Med Assoc
Objective—To evaluate the influences of animal age, bacterial coinfection, and porcine reproductive and respiratory syndrome virus (PRRSV) isolate pathogenicity on virus concentration in pigs.
Animals—Twenty-one 2-month-old pigs and eighteen 6-month-old pigs.
Procedure—Pigs were grouped according to age and infected with mildly virulent or virulent isolates of PRRSV. The role of concurrent bacterial infection was assessed by infecting selected pigs with Mycoplasma hyopneumoniae 21 days prior to inoculation with PRRSV. On alternating days, blood and swab specimens of nasal secretions and oropharyngeal secretions were collected. On day 21 after inoculation with PRRSV, selected tissues were harvested. Concentrations of PRRSV were determined by use of quantitative real-time PCR and expressed in units of TCID50 per milliliter (sera and swab specimens) or TCID50 per gram (tissue specimens).
Results—Concentrations of virus were higher in blood and tonsils of pigs infected with virulent PRRSV. Pigs infected with virulent PRRSV and M hyopneumoniae had significantly higher concentrations of viral RNA in lymphoid and tonsillar tissue. Coinfection with M hyopneumoniae resulted in a higher viral load in oropharyngeal swab specimens and blood samples, independent of virulence of the PRRSV isolate. Two-month-old pigs had significantly higher viral loads in lymph nodes, lungs, and tracheal swab specimens than did 6-month-old pigs, independent of virulence of the PRRSV isolate.
Conclusions and Clinical Relevance—Multiple factors affect PRRSV concentration in pigs, including pathogenicity of the PRRSV isolate, age, and concurrent infection with M hyopneumoniae.
Objective—To evaluate sensitivities at the herd level
of test strategies used in the Voluntary Johne's
Disease Herd Status Program (VJDHSP) and alternative
test strategies for detecting dairy cattle herds
infected with Mycobacterium paratuberculosis.
Design—Nonrandom cross-sectional study.
Sample Population—64 dairy herds from
Pennsylvania, Minnesota, Colorado, Ohio, and
Wisconsin. Fifty-six herds had at least 1 cow shedding
M paratuberculosis in feces; the other 8 herds
were free from paratuberculosis.
Procedure—For all adult cows in each herd, serum
samples were tested for antibodies to M paratuberculosis with
an ELISA, and fecal samples were submitted
for bacterial culture for M paratuberculosis. Sensitivities
at the herd level (probability of detecting infected herd)
of various testing strategies were then evaluated.
Results—Sensitivity at the herd level of the testing
strategy used in level 1 of the VJDHSP (use of the
ELISA to test samples from 30 cows followed by confirmatory
bacterial culture of feces from cows with
positive ELISA result) ranged from 33 to 84% for
infected herds, depending on percentage of cows in
the herd with positive bacterial culture results. If follow-
up bacterial culture was not used to confirm positive
ELISA results, sensitivity ranged from 70 to
93%, but probability of identifying uninfected herds
as infected was 89%.
Conclusions and Clinical Relevance—Results suggest
that the testing strategy used in the VJDHSP will
fail to identify as infected most dairy herds with a low
prevalence of paratuberculosis. A higher percentage
of infected herds was detected if follow-up bacterial
culture was not used, but this test strategy was associated
with a high probability of misclassifying uninfected
herds. (J Am Vet Med Assoc 2002;220: 1053–1057)