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1.
OBJECTIVE: To characterize the genetic diversity of Haemophilus parasuis field isolates with regard to serovar, herd of origin, and site of isolation. SAMPLE POPULATION: Isolates of H parasuis obtained from pigs in 15 North American herds and multi-farm systems. PROCEDURE: 98 H parasuis isolates were genotyped with the enterobacterial repetitive intergeneic consensus based-polymerase chain reaction (ERIC-PCR) technique and serotyped via agar gel precipitation test. Genomic fingerprints were analyzed and dendrograms were constructed to identify strains from the same serovar group, herd of origin, or isolation site and to evaluate the genetic variability within these categories. RESULTS: Serovar 4 (39%) and nontypeable (NT) isolates (27%) were most prevalent. Thirty-four distinct strains were identified among the 98 isolates, using a 90% similarity cutoff. Strains from serovar 4 and NT isolates had high genetic diversity (12 and 18 strains, respectively). One to 3 major clusters of prevalent strains could be identified in most of the evaluated herds. Haemophilus parasuis strains isolated from the upper respiratory tract were either serovar 3 or NT isolates. Potentially virulent strains (isolated from systemic sites) were either serovars 1, 2, 4, 5, 12, 13, or 14, or NT isolates. CONCLUSIONS AND CLINICAL RELEVANCE: Although H parasuis had high genetic diversity overall, only a few strains caused disease in these herds. The ERIC-PCR technique was more discriminative than serotyping, and a broad genetic variety was observed within particular serovar groups.  相似文献   

2.
Glasser's disease accounted for less than 1% of total swine mortalities in an 11 year retrospective postmortem survey of swine submissions at three provincial government diagnostic laboratories in southern Ontario. However, Glasser's disease was suspected in 17 of 83 boar mortalities at the Record of Production Boar Test Station between 1983 and 1985 and was much more common in specific-pathogen-free (SPF) boars than in conventional boars. The prevalence of the causative organism, Haemophilus parasuis, was determined for 19 SPF herds in Ontario classified as "Excellent" under the Ontario Swine Herd Health Policy. Nasal swabs from two-month-old pigs were cultured on chocolate agar containing 1.5 mug/mL lincomycin, 5 mug/mL bacitracin, and 0.1 mug/mL crystal violet. Three herds were negative for H. parasuis infection; 16 herds contained clinically healthy carrier pigs.  相似文献   

3.
Haemophilus parasuis: new trends on diagnosis, epidemiology and control   总被引：35，自引：0，他引：35  
Haemophilus parasuis is a commensal organism of the upper respiratory tract of conventional pigs, but under appropriate conditions can invade and cause severe systemic disease, characterized by fibrinous polyserositis, arthritis and meningitis. Factors involved in systemic invasion by H. parasuis remain largely unknown. However, major advances in our knowledge of H. parasuis include (1) development of a species-specific PCR test to detect H. parasuis in clinical samples, (2) study of molecular epidemiology within and between herds, by use of a repetitive element-based PCR, (3) the proposal of an alternative serotyping technique, (4) development and testing of a new in vivo model for pathogenesis and virulence studies, and (5) use of controlled exposure of young pigs to low doses of live, virulent H. parasuis strains to reduce nursery mortality in affected swine herds.  相似文献   

4.
Haemophilus parasuis can cause pneumonia and systemic disease in swine but it is also a coloniser of the upper respiratory tract of healthy pigs. These differences in pathogenicity are probably the result of diverse mechanisms of virulence in different strains. Since serum-resistance is a feature frequently found in systemic pathogens, 31 H. parasuis strains of different clinical origin were tested and a variety of serum susceptibility levels detected. Nasal strains from healthy piglets were sensitive to the bactericidal effect of the serum, while systemic strains were mainly resistant. The pulmonary strains included both serum-sensitive and serum-resistant strains. Interestingly, the serum-resistant pulmonary strains were isolated from animals with systemic lesions. Heat-treatment of the sera abolished the bactericidal activity, indicating that complement is a key factor in this effect. Equivalent susceptibility was observed with rabbit and porcine sera, and the presence of H. parasuis specific antibodies did not increase the killing of the strains by serum. In an attempt to associate serum-resistance to a surface determinant of the bacteria, agglutination in acriflavine was tested but no direct link with serum susceptibility was found. The results indicate that serum-resistance is a virulence mechanism in H. parasuis.  相似文献   

5.
This approach maximizes sensitivity of serology-based monitoring systems by considering spatial clustering of herds classified as false positive by herd testing, allowing outbreaks to be detected in an early phase. The primary objective of this study was to determine whether swine herds infected with influenza viruses cluster in space, and if so, where they cluster. The secondary objective was to investigate the combining of a multivariate spatial scan statistic with herd test results to maximize the sensitivity of the surveillance system for swine influenza. We tested for spatial clustering of swine influenza using the Cuzick–Edwards test as a global test. The location of the most likely spatial clusters of cases for each subtype and strain in a sample of 65 sow and 72 finisher herds in 2001 (Ontario, Canada), and 76 sow herds in 2003 (Ontario, Canada) was determined by a spatial scan statistic in a purely spatial Bernoulli model based on single and multiple datasets.

A case herd was defined by true herd-disease status for sow or finisher herds tested for H1N1, and by apparent herd-disease status for sow herds tested for two H3N2 strains (A/Swine/Colorado/1/77 (Sw/Col/77) and A/Swine/Texas/4199-2/98 (Sw/Tex/98)). In sow herds, there was no statistically significant clustering of H1N1 influenza after adjustment for pig-farm density. Similarly, spatial clustering was not found in finisher herds. In contrast, clustering of H3N2 Sw/Col/77 (prevalence ratio = 12.5) and H3N2 Sw/Tex/98 (prevalence ratio = 15) was identified in an area close to a region with documented isolation of avian influenza isolates from pigs.

For the H1N1 subtype tested by ELISA, we used an approach that minimized overall misclassification at the herd level. This could be more applicable for detecting clusters of positive farms when herd prevalence is moderate to high than when herd prevalence is low. For the H3N2 strains we used an approach that maximized herd-level sensitivity by minimizing the herd cut-off. This is useful in situations where prevalence of the pathogen is low. The results of applying a multivariate spatial scan statistic approach, led us to generate the hypothesis that an unknown variant of influenza of avian origin was circulating in swine herds close to an area where avian strains had previously been isolated from swine. Maximizing herd sensitivity and linking it with the spatial information can be of use for monitoring of pathogens that exhibit the potential for rapid antigenic change, which, consequently, might then lead to diminished cross-reactivity of routinely used assays and lower test sensitivity for the newly emerged variants. Veterinary authorities might incorporate this approach into animal disease surveillance programs that either substantiate freedom from disease, or are aimed at detecting early incursion of a pathogen, such as influenza virus, or both.  相似文献   


6.
Faeces samples were taken three times at two-week intervals, from the farrowing units of four herds of known Brachyspira (formerly Serpulina) status and one of unknown Brachyspira status. Brachyspira hyodysenteriae, Brachyspira pilosicoli, Brachyspira intermedia and Brachyspira group III were isolated from the faecal samples from the weaners in the herds using either a maximum of 50 ppm of olaquindox or no feed additives. The detection rates were relatively consistent. However, B hyodysenteriae was not detected at one sampling in a known positive herd. The prevalence of Brachyspira species was also studied in feeder pigs originating from LSO 2000 health class farrowing units, comparable with specific pathogen-free herds. These farms were free from swine dysentery, sarcoptic mange, swine enzootic pneumonia and progressive atrophic rhinitis. Fifty of 428 herds were sampled once. B hyodysenteriae was not isolated from any of them, but B intermedia, B pilosicoli and Brachyspira group III were isolated from five, 14 and 37 of the herds, respectively. The detection of Brachyspira species did not relate to the prevalence of diarrhoea in the herds, as judged by the farmers. The herds using carbadox (40 to 50 ppm) had a lower prevalence of Brachyspira species than those using olaquindox (40 to 50 ppm).  相似文献   

7.
Serum samples from 458 swine from eight specific pathogen-free (SPF) herds swine were compared to samples from 178 swine from eight non-SPF herds in Illinois using the complement fixation (CF) test for Mycoplasma hyopneumoniae antibodies. In SPF herds, 9.4% of the samples gave positive test results, compared to 51.7% of the samples from non-SPF herds. The range of reactor rates in SPF herds was 0–26.9% and in non-SPF herds 3.4–100%. Used on herd basis with some modification, the CF test should be useful in monitoring state and nationally accredited SPF swine herds.  相似文献   

8.
Haemophilus parasuis is a colonizer of the upper respiratory tract and the causative agent of Gl?sser's disease in swine. This study focused on the nasal carriage of H. parasuis after treatment with marbofloxacin. Three marbofloxacin treatments (three doses of 2mg/kg body weight [bw] every 24h, two doses of 4 mg/kg bw every 48 h and 8 mg/kg bw in one single shot) were used and all of them reduce significantly (p<0.05) the nasal carriage of H. parasuis as compared to control animals. Moreover, H. parasuis was not detected in the nasal cavities of piglets after administering the highest dose. The effect of a dose of 8 mg marbofloxacin/kg bw in one shot was further studied in a farm with clinical cases of Gl?sser's disease using a longitudinal study. Statistically significant reduction of nasal carriage of H. parasuis was detected during the first week after treatment in comparison with the control group. However, a clear relationship between the minimum inhibitory concentration (MIC) of the different strains, their putative virulence or the treatment group (antibiotic or control) from which they were isolated was not detected. Finally, the effect induced by the antibiotic treatment on the bacterial strains seemed to be transitory, since diverse H. parasuis strains (with high and low marbofloxacin MICs) were observed 7 days after finishing the treatment.  相似文献   

9.
Three trials were conducted to establish if young primary specific pathogen free (SPF) pigs could be protected from Glasser's disease by vaccination. Three age groups of cesarean-derived isolator-reared gnotobiotic pigs were vaccinated twice at 4 and 6, 3 and 5, and 2 and 4 wk of age respectively with a formalin killed aluminum hydroxide adsorbed bacterin prepared from three strains of Haemophilus parasuis isolated from Ontario pigs affected with Glasser's disease. When challenged two weeks later with the homologous strains of virulent bacteria, all the vaccinated pigs remained healthy, while 17/18 nonvaccinated pigs became severely sick or died between three and seven days postchallenge. The one surviving nonimmunized pig was retarded in growth. All of the nonimmunized pigs had visible lesions of polyserositis, the most common being polyarthritis (14/18). Other lesions were fibrinous meningitis, pericarditis, pleurisy and/or peritonitis. Two of the pigs died with a septicemia. Haemophilus parasuis was isolated from 15/18 nonimmunized pigs, usually from several of the affected sites. The organisms were not isolated from the immunized pigs, nor from the surviving nonimmunized pig. Attempts to detect the presence of specific antibodies against the H. parasuis strains in the sera of the immunized or exposed pigs by the passive hemagglutination test or by enzyme linked immunoassay were unsuccessful. The results of this work indicate that primary SPF pigs can be protected from Glasser's disease by vaccination as early as 2 and 4 wk of age. The nature of this protective mechanism was not established in this study.  相似文献   

10.
Development of a PCR test to diagnose Haemophilus parasuis infections.   总被引：30，自引：0，他引：30  
A polymerase chain reaction (PCR) test was developed in order to improve the accuracy and speed of diagnosis of Haemophilus parasuis, an economically important respiratory pathogen that affects swine. The gene sequence of the 16S small subunit ribosomal RNA of H. parasuis (GenBank M75065) was compared with 56 16S sequences of related bacteria, including those frequently isolated from pig tissues. Two species-specific primers were designed: HPS forward and HPS reverse. The predicted size of the amplified PCR product was 821 bp. The PCR test could detect a minimum of 102 bacteria and 0.69 pg of DNA. Thirty-one H. parasuis isolates, including 12 different serovars and 19 field isolates, were positive using the PCR test. No amplification was observed when the test was run using DNA from 15 other bacterial species commonly isolated from swine tissues. A weak band was observed when the PCR test was performed using Actinobacillus indolicus DNA as template. Clinical samples tested by PCR included tissues and swabs from 5 animals naturally infected with H. parasuis and 1 experimentally infected animal. The PCR was positive in 26 of 30 clinical samples. Four samples showed weak bands, and these results were not considered positive. Haemophilus parasuis was isolated from 18 of 30 of these samples. Tissues from specific pathogen-free (SPF) pigs and from unrelated species were negative for H. parasuis isolation and PCR. The developed PCR was successfully used in the diagnosis of H. parasuis infection, especially when compared with traditional microbiology techniques.  相似文献   

11.
Prevalence of Haemophilus parasuis serovars among isolates from swine.   总被引：11，自引：0，他引：11  
Two hundred sixty Haemophilus spp isolates that had been obtained from the respiratory tract and other sites of swine were acquired from diagnostic laboratories, primarily in the United States and Canada. The majority of isolates (243/260) were biochemically characterized as H parasuis; however, a few isolates of taxa distinct from H parasuis (taxa "minor group," D, E, and F) were identified. Fourteen H parasuis serovars were identified, and of those previously described, the most prevalent were 5 (24.3% of isolates), 4 (16.1%), 2 (8.2%), and 7 (3.7%). Three new serovars that were also prevalent included ND4 (11.1%), ND3 (8.6%), and ND5 (6.6%). Serovars 1, 3, 6, C, D, and new serovars ND1 and ND2 were infrequently identified, and 15.2% of isolates were nontypeable. It was not uncommon to isolate multiple serovars from swine of the same herd or related herds. Distribution of serovars among isolates from the United States and Canada was generally similar; however, a higher prevalence of serovar 5 and a lower prevalence of serovars 2, ND3, and ND5 were evident in isolates from Canada. Comparison of isolates obtained from the respiratory tract of swine without polyserositis with those obtained from swine with polyserositis revealed an increased frequency of serovars 4 and 5, and a decreased frequency of serovar 2, among isolates from swine with polyserositis. However, all prevalent serovars were isolated from swine with polyserositis, and data were not indicative of an association between serovar, site of isolation, or pathogenic potential.  相似文献   

12.
Tonsillar and nasal swabs were collected from weanling pigs in 50 representative Ontario swine herds and tested for the presence of 5 important bacterial upper respiratory tract pathogens. All but 1 herd (2%) tested positive for Streptococcus suis by polymerase chain reaction (PCR); 48% of herds were S. suis serovar 2, 1/2 positive. In all but 2 herds there was evidence of Haemophilus parasuis infection. In contrast, toxigenic strains of Pasteurella multocida were detected by a P. multocida--enzyme-linked immunosorbant assay (PMT-ELISA) in only one herd. Seventy-eight percent of the herds were diagnosed positive for Actinobacillus pleuropneumoniae by apxIV PCR. Sera from finishing pigs on the same farms were also collected and tested by ELISA for the presence of A. pleuropneumoniae antibodies. Seventy percent of the herds tested had evidence of antibodies to A. pleuropneumoniae including serovars 1-9-11 (2%), 2 (4%), 3-6-8-15 (15%), 5 (6%), 4-7 (26%), and 12 (17%). This likely represents a shift from previous years when infection with A. pleuropneumoniae serovars 1, 5, and 7 predominated. At least 16% and possibly as many as 94% of the herds tested were Actinobacillus suis positive; only 3 of the 50 herds were both A. pleuropneumoniae and A. suis negative as judged by the absence of a positive PCR test for apxII. Taken together, these data suggest that over the past 10 years, there has been a shift in the presence of pathogenic bacteria carried by healthy Ontario swine with the virtual elimination of toxigenic strains of P. multocida and a move to less virulent A. pleuropneumoniae serovars. As well, there appears to be an increase in prevalence of S. suis serovar 2, 1/2, but this may be a reflection of the use of a more sensitive detection method.  相似文献   

13.
Haemophilus parasuis is a colonizer of the upper respiratory tract of pigs and the etiological agent of Gl?sser's disease, which is characterized by a fibrinous polyserositis, meningitis and arthritis. Gl?sser's disease has never been reported in wild boar (Sus scrofa), although antibodies against H. parasuis have been detected. The goal of this study was to confirm the presence of this bacterium in wild boar by bacterial isolation and to compare the strains to H. parasuis from domesticated pigs. Therefore, nasal swabs from 42 hunted wild boars were processed for bacterial isolation and subsequent H. parasuis identification by specific PCR, biochemical tests and 16S rRNA gene sequencing. Two different strains of H. parasuis from two wild boars were isolated. These strains belonged to serotype 2 and were included by 16S rRNA gene sequencing and MLST analysis in a cluster with other H. parasuis strains of nasal origin from domestic pigs. During this study, Actinobacillus minor and Actinobacillus indolicus, which are NAD-dependent Pasteurellaceae closely related to H. parasuis, were also isolated. Our results indicate similarities in the respiratory microbiota of wild boars and domestic pigs, and although H. parasuis was isolated from wild boars, more studies are needed to determine if this could be a source of H. parasuis infection for domestic pigs.  相似文献   

14.
Reference strains for Haemophilus parasuis serovars 1 to 7 were examined for virulence by inoculation of guinea pigs. Guinea pig response to intraperitoneal inoculation was similar for the 7 reference strains. However, apparent differences in virulence were detected after intratracheal inoculation. Cells of the references strains for serovars 1 and 5 were most invasive, causing moribundity or death at higher doses and a persistent septicemia at lower doses. Haemophilus parasuis could be isolated from respiratory and systemic sites; purulent bronchopneumonia, pericarditis, and pleuritis were apparent in infected guinea pigs. Inoculation of cells of the reference strains for serovars 2 and 6 also resulted in bronchopneumonia and moribundity or death in some guinea pigs; however, reisolation of H parasuis and microscopic lesions at necropsy were less pronounced than those observed with serovars 1 and 5. Inoculation of cells of serovars 3, 4 and 7 induced only transient clinical signs and minimal evidence of H parasuis infection at necropsy. The data from intratracheal inoculation of guinea pigs are similar to data from other investigations in swine, indicating differences in the pathogenic potential of H parasuis strains. Thus, guinea pigs may be useful as a laboratory animal model for examining cellular factors associated with virulence and immunogenicity of H parasuis.  相似文献   

15.
Serum alpha-1-acid glycoprotein (alpha 1AG) was measured in 212 Landrace White pigs between birth and finishing age. The alpha 1AG level of healthy pigs five to ten months of age was 338 +/- 79 micrograms/mL, and the upper normal limit in mature swine has been established as 500 micrograms/mL. In both specific pathogen-free (SPF) and conventional pigs, the alpha 1AG level within one day of birth was 14,263 +/- 2,393 micrograms/mL, 40 times the normal adult value, but rapidly decreased to 699 +/- 186 micrograms/mL by four weeks of age. In conventional pigs, alpha 1AG began to increase after four weeks, averaged 1,428 micrograms/mL by eight weeks, but gradually decreased to adult levels by 20 weeks of age. In comparison, alpha 1AG of SPF pigs was only 800 micrograms/mL at eight weeks and decreased more rapidly to normal by 16 weeks of age. The conventional pigs had a high incidence of clinical pneumonia and specific antibodies to Actinobacillus pleuropneumoniae and Mycoplasma hyopneumoniae at the age of eight weeks. As the clinical pneumonia disappeared, serum alpha 1AG level also gradually declined. In contrast, SPF pigs had little clinical illness, low alpha 1AG, and little serological evidence of microbial infection. Conventional pigs with nonrespiratory infections, encephalitis, or with hernias had increased alpha 1AG. While the very high alpha 1AG level of the neonatal pig may be due to genetic influences, increases later in life are likely in response to stimuli from its external environment. Monitoring of serum alpha 1AG in several herds aided in the recognition of disease processes and may have potential use in swine herd health management.  相似文献   

16.
Haemophilus parasuis, the bacterium responsible for Gl?sser's disease, is a pathogen of significant concern in modern high-health swine production systems but there is little information regarding the identity or function of its virulence factors. Several important human mucosal pathogens, including the closely related bacterium Haemophilus influenzae, utilize IgA proteases to aid in defeating the host immune response and facilitate disease but it is unknown whether H. parasuis synthesizes any product with IgA protease activity. To investigate potential virulence mechanisms of H. parasuis, we evaluated five strains for their ability to digest purified IgA. Western blotting demonstrated cleavage of swine IgA, but not human IgA1, following incubation with culture supernatants from three strains, two of which are known to cause invasive disease. No genes with homology to the H. influenzae IgA protease genes iga and igaB could be identified in any H. parasuis strain using either PCR or Southern blotting. These results demonstrate that a novel IgA protease produced by some strains of H. parasuis cleaves the swine IgA heavy chain at a site not found in human IgA1.  相似文献   

17.
Chronic pleuritis (CP) in Danish pigs for slaughter is by far the most frequent finding at the routine post-mortem meat inspection. An initial investigation published in 1990 demonstrated infectious and management-related risk factors. Serological testing for additional infectious agents, as well as the need to consider the effect of disease clustering at the herd level, required a re-analysis of the data.

Our re-analysis used a representative sample of 4800 pigs originating from 623 Danish herds. Each pig was examined for the presence of CP and progressive atrophic rhinitis (PAR). The gender of the pig, the weight of the carcass, and the herd of origin were also recorded. Individual blood samples were examined for seropositivity for Actinobacillus pleuropneumoniae (AP) serotypes 2, 6, 7, 12, Haemophilus parasuis, Mycoplasma hyopneumoniae (MYC) and swine influenza (SI). Herd-level information retrieved through a questionnaire included health status, production type, herd size (i.e. pigs per year) and vaccination procedures.

Associations between CP and infectious, individual and herd-related factors were investigated by logistic regression with random effects. Among pigs from herds with conventional health status, seropositivity for AP serotypes 2 and 6, and MYC had odds ratios (ORs) of CP of 9.0, 1.6 and 1.8, respectively. Neither seropositivity for AP serotype 7 nor SI were associated with CP by themselves, but interacted: OR of CP of 5.3 (1.8) when present at the same time among pigs exhibiting (not exhibiting) PAR. An association of PAR with CP was found, and PAR interacted with AP serotype 7: OR=10.0 (4.3) when both factors were present among pigs exposed (non-exposed) to SI. The OR (0.97) for an increase of carcass weight by 1 kg was negligible.

In pigs from specific pathogen-free (SPF) herds, seropositivity for MYC and herd size were associated with CP. Moreover, for a herd size of 1000 pigs, CP was associated with exposure to MYC by an OR of 3.3 (decreasing to 1.9 when the herd size was increased by 1000). Farrow-to-finish as opposed to finishing herd had an OR of CP of 3.2.

In conventional herds, seropositivity for AP serotype 2 and MYC were associated with 51% and 29% of the occurrence of CP. In SPF herds, farrow-to-finish as opposed to finishing herds was associated with 47% of the occurrence of CP. Seropositivity for MYC was associated with 33% (39%) of the occurrence of CP in herds with a size > (≤) 1500 pigs.  相似文献   


18.
A nation-wide Salmonella enterica surveillance and control programme was initiated in Danish finishing herds over the first quarter of 1995. In Denmark, all swine for slaughter are identifiable by a unique herd code. For each herd code, and depending on the herd's annual kill, random samples ranging from four to more than 60 swine are obtained quarterly at the abattoir. A meat sample from each pig is frozen, and meat juice (harvested after thawing) is examined for specific antibodies against S. enterica using an indirect enzyme-linked immunosorbent assay (ELISA). The ELISA combines several S. enterica O-antigens, and allows detection of antibody response after a variety of different S. enterica serovar infections. Results are transferred to a central database, which each month (based on meat-juice tests obtained in the previous 13 weeks) assigns all herds into three S. enterica infection levels: Level 1, in which the S. enterica prevalence is deemed low and acceptable; Level 2, where there is a moderate prevalence of S. enterica seroreacl.ors (from > 50% in the smallest to > 10% in the largest herds); Level 3, in which S. enterica seroreactor prevalence is clearly unsatisfactory ( > 50% for most herd sizes). Irrespective of Salmonella level, all herds receive a monthly update on the current results of the S. enterica test results. If a herd is categorized in Level 2 or 3, it must receive an advisory visit by a practising veterinarian and a local swine extension specialist, and certain management hygiene precautions must be taken. If a herd is categorized in Level 3, the finishers from the herd must additionally be slaughtered under special hygiene precautions. This is supervised by the veterinary authorities.

During 1995, 604000 samples were tested for S. enterica, corresponding to 3.0% of the total kill. In December 1995, 15522 herds (representing > 90% of the national production) were categorized into one of the three levels: 14551 herds (93.7%) in Level 1; 610 herds (3.9%) in Level 2; 361 herds (2.3%) in Level 3. The proportion of serologically positive meat-juice samples collected during 1995 ranged from a mean of 2.9% in smaller herds (101–200 swine slaughtered per year) to 6.1% in relatively large herds (more than 5000 swine slaughtered per year).  相似文献   


19.
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20.
Porcine leptospirosis in Iowa   总被引：1，自引：0，他引：1  
The epidemiology of leptospirosis in Iowa swine was examined on the basis of serologic results and herd data from 55 herds in the National Animal Health Monitoring System (NAHMS) program and culture results and histories from 578 cases of reproductive failure submitted to the Iowa Veterinary Diagnostic Laboratory during a 3-year period. Thirty-eight percent of sera from NAHMS herds contained antibodies against 1 or more of 12 leptospira antigens. Leptospires were isolated from 9 (1.6%) of 578 cases of reproductive failure. Seven (78%) of the isolates were identified as Leptospira interrogans serovar kennewicki and 2 (22%) as serovar grippotyphosa. In 7 herds from which leptospires were isolated, attack rates ranged from 1% to 84%. Clinical leptospirosis, characterized by reproductive failure and confirmed by isolation of leptospires, was sporadic. No significant differences in farrowing averages and reproductive problems were observed between vaccinated and nonvaccinated NAHMS herds or between herds with higher (43-63%) or lower (14-40%) percentages of animals that were serologically positive against serovar bratislava.  相似文献   

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