Search Results

Abstract

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)

Abstract

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.

Animals—6 heifers.

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, and immunofluorescence.

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)

Abstract

Objective—To evaluate antibiotics for treatment of cattle with leptospirosis caused by Leptospira borgpetersenii serovar hardjo.

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 3 days).

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 2001;219:636–639)

Abstract

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)

Abstract

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.

Abstract

Objective—To evaluate gross, histopathologic, and serum biochemical findings caused by Leptospira interrogans serovars pomona and bratislava inoculated in dogs.

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 ×10⁷ L 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 2005;66:1816–1822)

Abstract

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 and perivasculitis.

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)

Abstract

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.

Design—Cross-sectional study.

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.

Abstract

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.

Design—Cross-sectional study.

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 2000;216:676–682)