Objective—To determine whether a monovalent
Leptospira borgpetersenii serovar hardjo (type hardjobovis)
vaccine commercially available in Australia,
New Zealand, Ireland, and the United Kingdom would
protect cattle from renal colonization and urinary
shedding when exposed to a US strain of Leptospira
borgpetersenii serovar hardjo.
Animals—24 Hereford heifers that lacked detectable
antibodies against serovar hardjo.
Procedure—Heifers received 2 doses, 4 weeks
apart, of the commercial hardjo vaccine (n = 8) or a
monovalent US reference hardjo vaccine (8) or were
not vaccinated (controls; 8). Heifers were challenged
16 weeks later by intraperitoneal inoculation or conjunctival
instillation. Serum antibody titers were measured
weekly, and urine samples were examined for
leptospires. Heifers were euthanatized 11 to 14
weeks after challenge, and kidney tissue was examined
for evidence of colonization.
Results—All 8 heifers vaccinated with the reference
vaccine were found to be shedding leptospires in
their urine and had evidence of renal colonization. All
4 control heifers challenged by conjunctival instillation
and 2 of 4 control heifers challenged by intraperitoneal
inoculation shed leptospires in their urine, and
all 8 had evidence of renal colonization. In contrast,
leptospires were not detected in the urine or tissues
of any of the 8 heifers that received the commercial
hardjo vaccine. Heifers that received the commercial
hardjo vaccine had significantly higher antibody titers
than did heifers that received the reference vaccine.
Conclusions and Clinical Relevance—Results suggest
that cattle that received 2 doses of the commercial
hardjo vaccine were protected against renal colonization
and urinary shedding when challenged with L
borgpetersenii serovar hardjo strain 203 four months
after vaccination. (Am J Vet Res 2001;62:995–1000)
Objective—To compare sensitivity and specificity of
various polymerase chain reaction (PCR) assays for
detection of Leptospira borgpetersenii serovar hardjo
in bovine urine and to compare results of the optimal
PCR assay with results of immunofluorescence,
nucleic acid hybridization, and bacteriologic culture.
Procedure—Heifers were exposed to serovar hardjo
type hardjo-bovis by conjunctival instillation of 106 leptospires
on 3 successive days. Urine samples were
collected before and after infection. Sensitivity and
specificity of 5 PCR assays were compared, to determine
the optimal assay for use with bovine urine samples.
The optimal PCR assay was then compared with
results of bacteriologic culture, nucleic acid hybridization,
Results—A PCR assay with the best combination of
specificity (100%) and sensitivity (91%) was selected
for comparison with the other diagnostic tests.
Sensitivity for nucleic acid hybridization was 55%,
whereas sensitivity for bacteriologic culture and
immunofluorescence was 89 to 93%.
Conclusions and Clinical Relevance—Bacteriologic
culture, PCR, and immunofluorescence were sensitive
for detection of L borgpetersenii serovar hardjo type
hardjo-bovis in urine specimens of cattle, but a single
technique was not the most sensitive for each animal
tested. Therefore, the use of 2 techniques in combination
is warranted for maximal sensitivity for diagnosis.
(Am J Vet Res 2000;61:316–320)
Objective—To evaluate antibiotics for treatment of
cattle with leptospirosis caused by Leptospira borgpetersenii
Design—Randomized controlled trial.
Animals—42 healthy mixed-breed cattle.
Procedure—Cattle were inoculated via conjunctival
instillation with L borgpetersenii serovar hardjo. After
infection and urinary shedding of L borgpetersenii
were confirmed, cattle were treated with various
antibiotics. To determine effectiveness of antibiotic
treatment, urinary shedding of L borgpetersenii was
monitored for 4 to 6 weeks after administration of
antibiotics, using darkfield microscopic examination,
microbial culture, immunofluorescence testing, and a
polymerase chain reaction assay.
Results—All inoculated cattle developed leptospirosis
and shed leptospires in their urine. The following
antibiotic treatments resulted in elimination of urinary
shedding of leptospires: a single injection of oxytetracycline
(20 mg/kg [9 mg/lb] of body weight, IM), tilmicosin
(10 mg/kg [4.5 mg/lb], SC), or a combination
product that contained dihydrostreptomycin-penicillin
G (25 mg/kg [11.4 mg/lb], IM) or multiple injections of
ceftiofur sodium (2.2 or 5 mg/kg [1 or 2.3 mg/lb], IM,
once daily for 5 days, or 20 mg/kg, IM, once daily for
Conclusions and Clinical Relevance—Successful
resolution of leptospirosis in cattle by administration
of dihydrostreptomycin-penicillin G confirms results
obtained by other investigators. Three other antibiotics
(oxytetracycline, tilmicosin, and ceftiofur) also
were effective for resolving leptospirosis and may be
useful substitutes for dihydrostreptomycin, an antibiotic
that is no longer available for use in food-producing
animals in the United States. Cost, safety, and
withdrawal times of these various treatment options
need to be considered. (J Am Vet Med Assoc
OBJECTIVE To determine the survivability of Mycobacterium bovis on salt and salt-mineral blocks in typical weather conditions in Michigan over two 12-day periods at the height of summer and winter.
SAMPLE 4 salt (NaCl) and 4 salt-mineral blocks inoculated with pure cultures of a strain of M bovis currently circulating in Michigan livestock and wildlife.
PROCEDURES In the summer and again in the winter, inoculated blocks were placed in secured outdoor facilities where equal numbers of each block type (2/type/season) were exposed to shade or sunlight. Samples were collected from randomly selected areas on the surface of each block beginning within 1 hour after placement (day 0) twice a day for the first 4 days and once a day from days 7 through 11. Bacterial culture of samples was performed to detect viable M bovis.
RESULTS Depending on the exposure conditions, salt blocks yielded viable M bovis for up to 2 days after inoculation and salt-mineral blocks yielded viable M bovis for > 3 days. Survival time was greatest on salt-mineral blocks kept outdoors in the shade during the winter. The odds of recovering viable M bovis from salt-mineral block samples were 4.9 times as great during the winter (vs the summer) and 3.0 times as great with exposure to shade (vs sunlight).
CONCLUSIONS AND CLINICAL RELEVANCE Results from this study indicated that salt and salt-mineral blocks should be considered potential sources of bovine tuberculosis when designing risk mitigation programs for cattle herds in areas with wildlife reservoirs of M bovis.
Objective—To evaluate gross, histopathologic, and
serum biochemical findings caused by Leptospira
interrogans serovars pomona and bratislava inoculated
Animals—Twenty-seven 8-week-old female Beagles.
Procedure—Dogs were randomly assigned to challenge
or control groups. Challenge groups were conjunctivally
inoculated on 3 successive days with
5 ×107L interrogans serovar pomona (n = 12) or
serovar bratislava (11). Clinical signs were recorded
throughout the experiment, and clinical pathology
assays, bacteriologic culture, and necropsies (6 or 7
dogs necropsied at each time point) were done on
postinoculation day (PID) 7, 10, 14, and 20.
Results—Infection could not be confirmed in any
serovar bratislava–inoculated dog, and control dogs
remained healthy throughout the experiment.
Positive culture and fluorescent antibody test results
were confirmed in 11 of 12 serovar pomona–inoculated
dogs. Fever and lethargy starting at PID 7 were
the most common clinical signs in serovar
pomona–infected dogs. On day 10, gross lesions
included multifocal renal and pulmonary hemorrhage
and perirenal edema. Serovar pomona–inoculated
dogs had histopathologic lesions including hepatitis,
interstitial nephritis, and pneumonia at PID 7, 10, 14,
and 20. Increases in BUN, anion gap, and bilirubin
concentration occurred on PID 10, 14, and 20.
Platelet counts in dogs with positive results of bacteriologic
culture were decreased from baseline values
on PID 10, 12, and 14.
Conclusions and Clinical Relevance—
Conjunctival inoculation with L interrogans serovar
pomona resulted in a high rate of infection with concomitant
hemorrhagic and inflammatory lesions of
the kidneys, liver, and lungs. (Am J Vet Res
Objective—To develop a method for inducing acute
leptospirosis in dogs.
Animals—31 nine-week-old female Beagles.
Procedure—Beagles were randomly assigned to 2
inoculation groups or a control group. Dogs were
inoculated on 3 successive days by conjunctival instillation
of 5 X 107 cells of Leptospira kirschneri serovar
grippotyphosa strain 82 (12 dogs) or strain RM 52 (14
dogs). Control dogs (n = 5) were similarly inoculated
with sterile leptospiral culture media. Clinical signs,
clinicopathologic variables, anti-leptospiral antibody
titers, and evidence of leptospires in tissues and body
fluids were evaluated. Dogs were euthanatized and
necropsied on days 7, 14, 22, or 28 after inoculation or
as required because of severe illness.
Results—Clinical signs in infected dogs included conjunctivitis,
lethargy, diarrhea, dehydration, vomiting,
and icterus. Consistent clinicopathologic alterations
included azotemia, hyperphosphatemia, increased
anion gap, hyperbilirubinemia, and an increase in alkaline
phosphatase activity. Leptospires were cultured
from the kidneys (11/12), urine (6/9), aqueous humor
(9/12), blood (12/12), and liver (12/12) of dogs inoculated
with strain 82. Only 3 of 14 dogs became infected
after inoculation with strain RM 52.
Histopathologic lesions in infected dogs included
interstitial nephritis, renal tubular degeneration and
necrosis, pulmonary hemorrhage, and hepatic edema
Conclusions and Clinical Relevance—Conjunctival
exposure to L kirschneri serovar grippotyphosa strain
82 resulted in acute leptospirosis in all inoculated
dogs, but only 3 of 14 dogs inoculated with strain RM
52 became infected. This method of infection by
serovar grippotyphosa can be used to study the
pathogenesis and prevention of leptospirosis in dogs.
(Am J Vet Res 2004;65:1100–1107)
Objective—To determine whether cattle testing positive
for Mycobacterium avium subsp paratuberculosisas
determined by microbial culture of feces or antibody
ELISA were more likely to have false-positive
responses on the caudal fold tuberculin (CFT) test or
interferon-γ (IFN-γ) assay for Mycobacterium bovis
than cattle testing negative for M paratuberculosis.
Animals—1,043 cattle from 10 herds in Michigan.
Procedure—Feces and blood samples for plasma
were collected from cattle ≥ 24 months old on the day
the CFT test was read. Fecal samples were submitted
for microbial culture for M paratuberculosis. Plasma
samples were tested for antibody against M paratuberculosis,
and IFN-γ after stimulation with purified
protein derivative tuberculin from M bovis or M avium.
Results—Of 1,043 cattle, 180 (17.3%) had positive CFT
test results (suspects) and 8 (0.8%) had positive IFN-γ
assay results after stimulation with purified protein
derivative tuberculin from M bovis. Forty-five (4.3%) and
115 (11.0%) cattle tested positive for M paratuberculosis
as determined by microbial culture of feces and antibody
ELISA, respectively. Cattle with positive responses
for M paratuberculosis appeared to have an
increased likelihood of false-positive results on the CFT
test, although this association was not significant.
Conclusions and Clinical Relevance—No significant
association was detected among cattle testing positive
for M paratuberculosis as determined by microbial
culture of feces and antibody ELISA and positive
CFT test and IFN-γ assay results for M bovis. (J Am
Vet Med Assoc 2005;226:429–435)
Objective—To determine the prevalence of antibodies against 6 Leptospira serovars and determine risk factors associated with positive Leptospira titers in healthy client-owned dogs in Michigan.
Animals—1,241 healthy dogs at least 4 months of age.
Procedures—Dogs were examined by veterinarians at private practices. Vaccinated and unvaccinated dogs were enrolled in the study, which occurred prior to the availability of a 4-serovar (Canicola, Grippotyphosa, Icterohaemorrhagiae, and Pomona) Leptospira vaccine. Sera were tested by use of the microscopic agglutination test to determine antibody titers against Leptospira serovars Bratislava, Canicola, Grippotyphosa, Hardjo, Icterohaemorrhagiae, and Pomona. A questionnaire was used to collect demographic information about each dog to identify risk factors associated with seropositive status.
Results—309 of 1,241 (24.9%) dogs had antibody titers against at least 1 of the 6 Leptospira serovars, which suggested exposure to Leptospira spp. Prevalence of antibodies was highest to serovar Grippotyphosa, followed by Bratislava, Canicola, Icterohaemorrhagiae, and Pomona. Age, travel outside Michigan, exercise outside fenced yards, and exposure to livestock and wildlife were significant risk factors for positive titers.
Conclusions and Clinical Relevance—Among healthy dogs from the lower peninsula of Michigan, > 20% have antibodies against leptospiral serovars historically considered uncommon but more recently incriminated as causing clinical canine leptospirosis. Wildlife and livestock may be of increasing importance as reservoirs for canine leptospirosis as urbanization continues to occur. Expanded vaccination strategies may partially mitigate these trends.
Objective—To determine the extent of leptospirosis
in persons exposed to infected swine, confirm the
source of disease, define risk factors for infection,
and identify means for preventing additional infections
during an outbreak in Missouri in 1998.
Sample Population—240 people and 1,700 pigs.
Procedure—An epidemiologic investigation was conducted
of people exposed to infected pigs from the
University of Missouri-Columbia swine herd. The investigation
included review of health of the pigs, a crosssectional
study of the people handling the pigs, serologic
testing of human and porcine sera, and risk-factor
analysis for leptospirosis within the human population.
Results—Serologic testing of samples collected at the
time of the investigation indicated that 59% of the pigs
had titers to leptospires, denoting exposure. Of the
240 people in the exposed study population, 163 (68%)
were interviewed, and of these, 110 (67%) submitted a
blood sample. Nine (8%) cases of leptospirosis were
confirmed by serologic testing. Risk factors associated
with leptospirosis included smoking (odds ratio [OR],
14.4; 95% confidence interval [CI],1.39 to 137.74) and
drinking beverages (OR, 5.1; 95% CI, 1.04 to 24.30)
while working with infected pigs. Washing hands after
work was protective (OR, 0.2; 95% CI, 0.03 to 0.81).
Conclusions and Clinical Relevance—Leptospirosis
is a risk for swine producers and slaughterhouse
workers, and may be prevented through appropriate
hygiene, sanitation, and animal husbandry. It is essential
to educate people working with animals or animal
tissues about measures for reducing the risk of exposure
to zoonotic pathogens. (J Am Vet Med Assoc