Characteristics of Thoroughbred and Quarter Horse racehorses that sustained a complete scapular fracture.

REASONS FOR PERFORMING STUDY: To determine if scapular fractures occur in racehorses with distinctive characteristics. OBJECTIVES: To test the hypothesis that Thoroughbred (TB) and Quarter Horse (QH) racehorses with a scapular fracture have similar characteristics that are different from those of their respective racetrack populations. METHODS: Necropsy findings, case details, last race information and career earnings for TB and QH racehorses that had a scapular fracture in California between 1990 and 2008 were retrospectively compared between breeds. Horse signalment, career earnings, career starts and race characteristics were obtained for all California racehorses. Comparisons were made between affected horses, other racehorses that died, and all horses that raced, in California during the 19 year period. RESULTS: Seventy-three TB and 28 QH racehorses had a similar, complete comminuted scapular fracture with an articular component, and right forelimb predilection. The QHs had a higher incidence of scapular fracture incurred during racing than TBs (0.98 vs. 0.39/1000 starters). The TB and QH incident rates for musculoskeletal deaths incurred racing were 20.5 and 17.5/1000 starters, respectively; however, a greater proportion of TB musculoskeletal deaths occurred training (40% vs. 8%). Horses with a scapular fracture were more likely to be male and aged 2 or ≥ 5 years than the racetrack population. Most affected QHs (64%) were 2-year-olds; most TBs (74%) were aged ≥ 3 years. Scapular fractures occurred more commonly during racing in QHs (70%) than TBs (44%). Race-related scapular fracture was more likely to occur in a Maiden race than in a non-Maiden race. Horses with a scapular fracture had fewer career starts than the racetrack population. CONCLUSIONS AND POTENTIAL RELEVANCE: Despite breed differences for signalment and exercise distances, both breeds incur a complete scapular fracture that is more likely to occur in the right scapula of young and older, male racehorses, early in their race career or after few races. Quarter Horses sustain a catastrophic scapular fracture more frequently than TBs.

Sudden death in racing Thoroughbred horses: an international multicentre study of post mortem findings.

REASONS FOR PERFORMING STUDY: To improve the understanding of exercise related sudden death in Thoroughbred racehorses. OBJECTIVES: To describe the post mortem findings in cases of sudden death associated with exercise in 268 Thoroughbred racehorses. METHODS: Gross and histological post mortem findings of 268 cases of sudden death were collated and reviewed. Cases originated from 6 racing jurisdictions around the world. Sudden death was defined as acute collapse and death in a closely observed and previously apparently healthy Thoroughbred racehorse, during, or within one hour after, exercise. Cause of death as determined by the attending pathologist was categorised as definitive, presumptive or unexplained and compared between the different populations. Cardiopulmonary lesions recorded at post mortem examination were compared between different populations. RESULTS: Pathologists recorded a definitive cause of death in 53% (143/268) of cases. Major definitive causes of sudden death included cardiac failure, apparent pulmonary failure, pulmonary haemorrhage, haemorrhage associated with pelvic fractures or with idiopathic blood vessel rupture, and spinal cord injury. A presumptive cause of death was made in 25% (67/268) of cases and death remained unexplained in 22% (58/268) of cases. There were several statistically significant inter-population differences in the cause of death and in reporting of cardiopulmonary lesions. CONCLUSIONS: Sudden death can be attributed to a variety of causes. Causes of sudden death and the lesions found in cases of exercise-related sudden death are similar in different racing jurisdictions. However, the lesions are often not specific for the cause of death and determination of the cause of death is therefore affected by interpretation by the individual pathologist.

The isolation of exotic Newcastle disease (END) virus from nonpoultry avian species associated with the epidemic of END in chickens in southern California: 2002-2003.

During the first 11 months of the 2002-2003 exotic Newcastle disease (END) epidemic in chickens in southern California, a total of 27,688 cloacal and tracheal (oropharyngeal) swab pools and/or tissue pools from 86 different avian species other than chickens and turkeys were submitted for Newcastle disease virus (NDV) isolation and characterization. Fifty-seven specimens (0.23%), representing 12 species of birds and 13 unspecified species, from a total of 24,409 accessions or submissions were positive for NDV. The NDV isolate was characterized as ENDV by real-time reverse transcription-polymerase chain reaction (RT-PCR). Of the 11,486 premises with other avian species, 1599 also had chickens. There were 1900 positive chicken samples from 164 premises, and 56 positive other avian species from 51 premises. Twelve premises had both positive chickens and positive other avian species. All positive other avian species were located on premises either on or within a 1 km radius of known infected premises. In this epidemic, premises with positive other avian species were significantly more likely to have chickens, and were significantly more likely to have positive chickens (OR = 3.7, P < 0.0001).

Spatial and temporal clustering of Salmonella serotypes isolated from adult diarrheic dairy cattle in California.

Electronic records from the California Animal Health and Food Safety Laboratory System between January 1, 1991, and June 30, 1998, were reviewed, and data on 593 Salmonella serotypes isolated from feces or intestinal contents of adult dairy cattle with diarrhea were analyzed to determine spatial and temporal clustering. A statistically significant clustering in space was detected with 10 (Typhimurium, Montevideo, Muenster, Anatum, Give, Menhaden, Kentucky, Agona, Derby, and Newport) of the 13 serotypes examined. Significant temporal clustering was also detected with 10 serotypes (Typhimurium, Montevideo, Muenster, Anatum, Give, Newbrunswick, Menhaden, Kentucky, Derby, and Newport). Six serotypes (Anatum, Menhaden, Montevideo, Muenster, Newbrunswick, and Newport) were significantly spatially and temporally clustered. A difference in temporal and spatial distribution patterns of some serotypes associated with diarrhea in adult dairy in California was found. Knowledge of the specific type of clustering, if present, should improve our understanding of the transmission and control of salmonellosis in the field.

Hoof size, shape, and balance as possible risk factors for catastrophic musculoskeletal injury of Thoroughbred racehorses.

OBJECTIVE: To evaluate hoof size, shape, and balance as risk factors for catastrophic musculoskeletal injuries (CMI), including suspensory apparatus failure (SAF) and cannon bone condylar fracture (CDY) in Thoroughbred racehorses. ANIMALS: 95 Thoroughbred racehorses that died between 1994 and 1996. PROCEDURE: 38 quantitative measures of hoof size, shape, and balance were obtained from orthogonal digital images of the hoof and were compared between case horses with forelimb CMI (70), SAF (43), and CDY (10) injuries and control horses whose death was unrelated to the musculoskeletal system (non-CMI, 25). Comparison of group means between cases and controls was done using ANOVA, and multivariable logistic regression was used to estimate odds ratios. RESULTS: Odds of CMI were 0.62 times lower for a 5mm increase in ground surface width difference and 0.49 times lower for a 100-mm2 increase in sole area difference. Odds of SAF were 6.75 times greater with a 10 degrees increase in toe-heel angle difference and 0.58 times lower with a 100-mm2 increase in sole area difference. Odds of CDY were 0.26 times lower with a 3 degrees increase in toe angle, 0.15 times lower with a 5-mm increase in lateral ground surface width, and 0.35 times lower with a 100-mm2 increase in sole area difference. CLINICAL RELEVANCE: Decreasing the difference between toe and heel angles should decrease risk of SAF for Thoroughbred racehorses and should be considered in addition to increasing toe angle alone to help prevent catastrophic injury. Trimming the hoof to perfect mediolateral symmetry may not be a sound approach to avoiding injury.

Program for surveillance of causes of death of dogs, using the Internet to survey small animal veterinarians.

OBJECTIVE: To develop a prototype program for surveillance of causes of death of dogs, using resources developed for the World Wide Web, to enable collection of data from veterinarians in small animal practice and dissemination of results in a timely manner at minimal expense. DESIGN: Epidemiologic survey. SAMPLE POPULATION: Small animal veterinarians who were members of NOAH, Veterinary Information Network (VIN), or VetPlus-L. PROCEDURE: Internet electronic communications and Web pages were used for solicitation and collection of data, dissemination of results, and follow-up discussions with participants. Data were stored in a relational database. RESULTS: 25 veterinarians actively submitted case material. On the basis of analysis by region and school of veterinary medicine attended, these veterinarians were representative of all small animal practitioners in the United States. During the 6-month study, 621 case reports were submitted. Analysis of results included determination of number of dogs, with proportions calculated for primary reason for death, primary clinical sign, and breed, as well as creation of a map depicting distribution of the practitioners. Additional data were obtained for analysis to provide information of interest. CLINICAL IMPLICATIONS: A national database representative of dogs examined by small animal practitioners would be a valuable source of information. Rapidly and easily accessible return of information and results is important for any surveillance system. The program described here appears to be a successful method for collecting data from practitioners.

Word search performance for diagnoses of equine surgical colics in free-text electronic patient records.

The objectives of the current project were to: (1) identify limitations of search sensitivity and positive predictive value (PPV) for free-text surgical diagnoses included in electronic patient records maintained at the University of California, Davis, Veterinary Medical Teaching Hospital (VMTH), (2) develop procedural or programmable recommendations for removing these limitations, and (3) provide guidelines for effective search strategies for users performing aggregate searches using the VMTH clinical information system. Search sensitivity corresponds to detection sensitivity (the capacity of a search term to 'identify' a relevant document) and search PPV indicates the proportion of retrieved documents that are relevant. All horses submitted to the VMTH for a gastrointestinal (GI) disorder requiring surgical intervention in 1995 were identified using procedure codes for billing purposes and stored in the electronic patient record. Patient records and surgical reports were reviewed for causes of GI disorders, and variation in naming of these disorders. Key word searches were performed for four GI disorders, and search performance was evaluated by estimating search sensitivity and PPV. Search sensitivity ranged from 33% to 98%, and PPV ranged from 2% to 74%. The procedural recommendation that would likely have the greatest influence on minimizing these search limitations would be more uniform naming of GI disorders. This would free searchers from having to anticipate all of the exact word combinations that could be used in the relevant documents, and also minimize retrieval of irrelevant documents.

Assessment of spatial and temporal clustering of ampicillin- and tetracycline-resistant strains of Pasteurella multocida and P haemolytica isolated from cattle in California.

OBJECTIVE: To determine whether ampicillin- and tetracycline-resistant strains of Pasteurella multocida and P haemolytica isolated from California cattle with pneumonia were spatially and temporally clustered and to compare overall estimates of percentages of these isolates resistant to these antimicrobials with estimates obtained on the basis of regional and temporal information. DESIGN: Epidemiologic study. SAMPLE POPULATION: Records of P multocida and P haemolytica isolates obtained from lung or tracheal wash samples collected from California cattle with pneumonia between July 1, 1991 and July 31, 1996. Only isolates obtained from samples submitted by dairies and calf ranches were used. PROCEDURE: Spatial clustering of ampicillin- and tetracycline-resistant isolates was assessed by use of nearest-neighbor and Cuzick and Edwards' analyses. Linear clustering along a north-south line was assessed by use of runs and maximum length of runs tests. Temporal clustering was assessed by use of scan tests. Spatial-temporal clustering was assessed by use of Barton's method. Regional estimates of percentages of P multocida and P haemolytica resistant to ampicillin or tetracycline were calculated. RESULTS: There was significant spatial clustering of resistant isolates and significant linear clustering along a north-south line. Significant differences in regional estimates of percentages of antimicrobial-resistant isolates were found. CLINICAL IMPLICATIONS: Results support the hypothesis that antimicrobial-resistant organisms can be clustered at the local level and reinforce the need to establish regional estimates of percentages of bacterial isolates that will be susceptible to commonly used antimicrobials.

Relationship between race start characteristics and risk of catastrophic injury in thoroughbreds: 78 cases (1992).

OBJECTIVE: To investigate relationships of several racehorse characteristics and race conditions with risk of a catastrophic musculoskeletal injury (CMI) resulting in euthanasia in Thoroughbreds during racing in California in 1992. DESIGN: Retrospective longitudinal study. ANIMALS: Thoroughbreds that incurred CMI during racing and all California race entrants in 1992. PROCEDURE: Necropsy records were reviewed, and race start information was obtained. Incidence risk of CMI/1,000 race entrants was estimated. Relationships between CMI during racing and race-meet, entrant age and sex, race type and length, and racing surface type and condition were evaluated by use of logistic regression. RESULTS: Incidence risk of CMI was 1.7/1,000 entrants. A higher risk of CMI was found at 2 fair race-meets, with incidence risks of 4.9 and 5.5/1,000 entrants. Risk of injury in male horses was 1.7 times greater than that in female horses, and influence of age on risk depended on race type. Risk of injury for horses 2 to 5 years old was two times greater for claiming horses than for maiden horses. Race length or racing surface type (dirt vs turf) or condition (fast, muddy, yielding) were not significantly associated with risk of CMI. CLINICAL IMPLICATIONS: Incidence of CMI was similar among 12 of 14 major and fair race-meets and among various race lengths and racing surface types and conditions, whereas incidence of CMI was influenced by entrant age and sex as well as race type. Investigators should consider controlling for age and sex, race-meet, and race type whenever possible in studies of risk of CMI.

A novel protein polymorphism differentiates the California serotype of infectious bronchitis from other serotypes common to California.

The California (Cal) serotype of infectious bronchitis virus (IBV) was isolated from layer flocks in southern California in the early 1980s. Since then, it has spread to the broiler-producing regions of central California, where it has been implicated in respiratory disease outbreaks in vaccinated flocks. Lack of a procedure for quickly identifying IBV serotypes in commercial chicken flocks has prevented the causal association of the IBV Cal serotype with respiratory disease outbreaks. A protein polymorphism has been identified in the matrix protein of the Cal serotype; it appears to be unique among other common serotypes of infectious bronchitis virus found in California. This polymorphism can be identified on western blots using raw or concentrated infectious allantoic fluid as the source material. Identification of the Cal serotype and of serotypes in the Mass and Conn groups can be performed rapidly using field samples from suspect flocks. The identification of this polymorphism provides an alternative method for the rapid identification of the Cal serotype of IBV.

Postmortem evaluation of homotypic variation in shoe characteristics of 201 thoroughbred racehorses.

OBJECTIVES: To develop a standard technique for evaluation of racehorse shoes, to assess homotypic variation (interlimb variation) in shoe characteristics, and to determine whether shoe characteristics varied with age and sex. DESIGN: Cross-sectional study. ANIMALS: Thoroughbred racehorses (n = 201) that died or were euthanatized at California racetracks between August 1992 and July 1994. PROCEDURE: Shoe characteristics were measured on horses examined after death. Percentage of agreement was used to compare shoe characteristics between limbs (homotypic variation). Using chi 2 analysis, shoe characteristics were compared between horses grouped by age and sex. RESULTS: Toe grabs were present on 90.5% of horses, and rim shoes were present on 15.9% of horses. Heel traction devices were less frequent on front (2.5%) than rear (6%) hooves. Pads were present on 24.9% of horses, with bonded rim pads most common. Special types of shoes were present cn 5% of horses. Percentage of agreement between left and right front hooves and between left and right rear hooves was high (20/25 variables; % agreement > or = 99). In contrast, percentage of agreement between left front and left rear hooves and between right front and right rear hooves was low (2/25 variables; % agreement > or = 99). Presence of a pad was significantly (P < 0.05) associated with age, and several shoe variable (size, presence of a special shoe, overall wear matched) were significantly (P < 0.05) associated with sex. CLINICAL RELEVANCE: Except for variables related to special shoes, wear, and weight, 1 shoe for the respective fore- or hind limbs could be used as an indicator for the contralateral shoe worn by Thoroughbred racehorses without substantial loss of information. However, 1 shoe could not be used as an indicator for shoe characteristics of all 4 limbs. Some shoe characteristics are associated with age and sex, and these variables should be considered possible confounders in studies of shoe characteristics.

Horseshoe characteristics as possible risk factors for fatal musculoskeletal injury of thoroughbred racehorses.

OBJECTIVE: To evaluate selected shoe characteristics as risk factors for fatal musculoskeletal injury (FMI) and specifically for suspensory apparatus failure (SAF) and cannon bone condylar fracture (CDY) of Thoroughbred racehorses in California. DESIGN: Case-control study. ANIMALS: Thoroughbred racehorses (n = 201) that died of were euthanatized at California racetracks between August 1992 and July 1994. PROCEDURE: Shoe characteristics were compared between case horses affected by FMI (155), SAF (79), and CDY (41) and control horses that died for reasons unrelated to the appendicular musculoskeletal system (non-FMI; 46). Multivariable logistic regression was used to estimate odds ratios for FMI, SAF, and CDY. RESULTS: Toe grabs were identified as possible risk factors for FMI, SAF, and CDY. The odds of FMI, SAF, and CDY were 1.8, 6.5, and 7.0, respectively, times greater for horses shod with low toe grabs than for horses shod without toe grabs on front shoes. Horses shod with regular toe grabs on front shoes had odds 3.5, 15.6, and 17.1 times greater (P < 0.05) for FMI, SAF, and CDY, respectively, compared with horses shod without toe grabs. The odds of horses shod with rim shoes were a third (P < 0.05) of those shod without rim shoes for either FMI or SAF. The apparent association between toe grab type and CDY may, in part, be attributable to concurrent SAF and CDY injuries in many horses. CLINICAL RELEVANCE: Avoiding the use of toe grabs should decrease the incidence of FMI, especially SAF, in Thoroughbred racehorses. The use of rim shoes that are more consistent with natural hoof shape may decrease injury risk.

Dairy cattle abortion in California: evaluation of diagnostic laboratory data.

A descriptive study was undertaken on 595 dairy cattle abortion submissions to the California Veterinary Diagnostic Laboratory System from July 1, 1987, to December 31, 1989, to determine the etiologic nature and distribution (seasonal and geographical) of dairy cattle abortion in California as reflected by laboratory submissions. Univariate analysis was performed to characterize abortion-related submissions by farm and laboratory variables, and logistic regression analysis was performed to determine factors that may influence success of abortion diagnosis in the laboratory. The proportions of dairies that submitted abortion-related specimens from northern, central, and southern milksheds during the 2.5-year period were 20.3%, 15.7%, and 13.1%, respectively, and 60% of submissions were from medium-sized (200-999 cows) dairies. Submissions consisted of fetus (58%), placenta (2%), fetus and placenta (12%), and fetus, placenta, and maternal blood (0.84%); fetal tissues and uterine fluid constituted the rest. An apparent pattern in abortion submissions was indicated by a peak in submissions during the winter and summer of 1988 and 1989. Infectious agents were associated with 37.1% of submissions; noninfectious causes, 5.5%, and undetermined etiology, 57.3%. Bacterial abortion accounted for 18% of etiologic diagnoses; protozoal, 14.6%; viral, 3.2%; and fungal, 1.3%. Submissions comprising fetus, placenta, maternal blood, or their combinations were associated with a higher likelihood of definitive diagnosis for abortion than tissues, as were fresher specimens and submissions associated with the second trimester of fetal gestation.

Fatal musculoskeletal injuries incurred during racing and training in thoroughbreds.

OBJECTIVE: To characterize and contrast data from Thoroughbreds that incurred a fatal musculoskeletal injury (FMI; injury resulting in death or euthanasia) during racing or training and data from all California race entrants during a 9-month period in 1991. DESIGN: Case-control study. ANIMALS: Thoroughbreds that incurred a FMI during racing or training at a California race-meet and all California race entrants from January through June and October through December 1991. PROCEDURE: Age and sex were compared with chi 2 and Fisher's exact tests among horses fatally injured while racing and training. A log-linear model was fit to assess the relationship between race-meet and age and sex of California race entrants. Incidence risk of racing FMI was estimated per 1,000 race entrants, and the relationship between the occurrence of FMI during racing with race-meet, age, and sex was evaluated by logistic regression. RESULTS: Injury type and sex-specific age distributions differed among the horses fatally injured during racing and training. Age and sex distributions of the race entrants were not independent and varied among race-meets. Overall incidence risk of racing FMI was estimated at 1.7/1,000 race entrants. Risk of racing FMI in male horses was about twofold that in female horses, and in 4-year-olds was twofold that in 3-year-olds. CLINICAL IMPLICATIONS: Age and sex-related differences in risk of incurring a FMI during racing should be considered when comparing fatal injury rates among race-meets.

Comparison of maternal blood and fetal liver selenium concentrations in cattle in California.

Selenium concentration was measured in paired maternal blood samples and fetal liver specimens collected at a San Joaquin County, Calif, slaughterhouse (beef = 19, dairy = 54) and from bovine aborted fetuses submitted to the California Veterinary Diagnostic Laboratory System (CVDLS; beef = 20, dairy = 20). Of the slaughterhouse samples and specimens, dairy maternal blood selenium concentration was significantly (P < 0.001) higher (mean +/- SD; 0.22 +/- 0.056 microgram/ml) than that for beef breeds (0.137 +/- 0.082 microgram/ml). The CVDLS mean maternal blood selenium concentration for the dairy-breed samples (0.192 +/- 0.028 microgram/ml) was similar to that for the slaughterhouse dairy-breed samples, but was greater than that for the slaughterhouse beef-breed samples. Slaughterhouse mean fetal liver selenium content also was higher (P < 0.001) for the dairy breeds (0.777 +/- 0.408 microgram/g), compared with the beef breeds (0.443 +/- 0.038 microgram/g). Mean fetal liver selenium content for slaughterhouse specimens was higher (P < 0.002) than that for the CVDLS specimens (beef, 0.244 +/- 0.149 microgram/g; dairy, 0.390 +/- 0.165 microgram/g). At the CVDLS, dairy fetal liver content was greater (P < 0.001) than that for beef breeds. Mean ratio of fetal liver selenium content to maternal blood selenium concentration was 3.53 +/- 1.89 for dairy breeds at the slaughterhouse (liver-to-blood correlation [r] = 0.38), and was 2.11 +/- 1.00 for dairy breeds at the CVDLS (r = 0.31) and 3.43 +/- 1.50 for beef breeds (r = 0.58). Both slaughterhouse breed ratios were significantly (P < 0.002) greater than the CVDLS dairy-breed ratio. On the basis of these results, breed and source location should be taken into account when interpreting selenium values. Fetal liver selenium content should only be used as a screening test and combined with whole blood selenium concentration from clinically normal herdmates to evaluate herd selenium status.

Serotypes of Salmonella isolated from California turkey flocks and their environment in 1984-89 and comparison with human isolates.

Serotypes of Salmonella from turkeys and their environment identified at the California Veterinary Diagnostic Laboratory System (CVDLS) between 1984 and 1989 are reported. Between 1988 and 1989, Salmonella serotypes from turkeys were compared from two sources: from routine submissions to the CVDLS (primarily associated with the National Poultry Improvement Plan), and from a random sample of turkey farms conducted by the National Animal Health Monitoring System (NAHMS). Serotype isolation frequencies were ver similar under these two systems. Serotypes identified most frequently under both systems were (listed from most to least frequent): Salmonella kentucky, S. anatum, S. heidelberg, S. reading, and S. senftenberg. This isolation pattern was different from that found in humans in California; only S. heidelberg was relatively common in both humans and turkeys during this period.

The correlation between serum selenium and blood selenium in cattle.

The selenium (Se) concentration of paired blood and serum samples from cattle was determined by 2 methods: 1) atomic absorption spectroscopy using hydride generation (HG-AAS), and 2) inductively coupled argon plasma emission spectroscopy using hydride generation (ICP). Samples from 327 cattle were analyzed by HG-AAS, and samples from 344 cattle were analyzed by ICP. The data were examined by linear regression analysis, and the technique of inverse prediction was utilized to determine prediction intervals for estimating blood Se concentration from known serum Se concentration. The correlation coefficients, by simple linear regression of serum Se on blood Se, were 0.79 (r2 = 0.62) and 0.88 (r2 = 0.77) for the HG-AAS data and the ICP data, respectively. For the HG-AAS data, the inverse prediction formula for estimating blood Se when serum Se is known, at the 95% prediction interval, was [formula; see text]. For the ICP data, the inverse prediction formula for estimating blood Se when serum Se is known, at the 95% prediction interval, was [formula; see text]. The prediction intervals were quite wide, and the accuracy of estimating blood Se from a known serum Se was not useful for diagnostic purposes. The use of serum Se concentration to assess nutritional status of cattle with respect to Se does not appear to be appropriate.

Patterns of bovine dairy submissions to the California Veterinary Diagnostic Laboratory System.

Dairy cattle submissions to the California Veterinary Diagnostic Laboratory System (CVDLS) were analyzed to determine submitter statistics. Eligible submissions were those received July 1, 1987 through December 31, 1989 for reasons other than regulatory brucellosis serology. A comprehensive list frame of California dairies was constructed from Brucella Ring Test information and served as the comparison population for the study. Analyses were performed based on geographic location, herd size, proximity to a CVDLS laboratory, and frequency of submission. Thirty-nine percent of the 2,490 California dairies in the reference population had submitted specimens greater than or equal to 1 time to the CVDLS during the study period. Twenty-three percent of the reference population had submitted greater than or equal to 2 times. Specimens were more likely to be submitted from larger herds than smaller herds. Larger dairies also submitted specimens more frequently. Dairies in the northern part of the state were more likely to submit specimens and submitted more frequently than southern herds when herd size was accounted for in the analysis. Mean submission rate (+/- SD) for the 970 submitting dairies was 1.4 (+/- 1.8) submissions/year. Forty-six percent of the dairies accounted for 80% of submissions, whereas only 14% of dairies accounted for 50% of all diagnostic dairy submissions.

An outbreak of equine neonatal salmonellosis.

An outbreak of salmonellosis in foals occurred on a large Thoroughbred farm in California. Only foals less than 8 days of age exhibited clinical signs, which included depression, anorexia, and diarrhea. Three foals died from septicemia. The agent responsible was Salmonella ohio, which is rarely involved in salmonellosis in horses. During the course of the outbreak, S. ohio was isolated from 27 of 97 mares (27.8%) and 34 of 97 foals (35.1%). Mares were the presumed source of infection for foals. The absence of clinical signs in mares allowed for increased exposure of foals through environmental contamination. Although foals continued to become infected after strict control measures were adopted, none became ill. Salmonella serotypes of seemingly low virulence can produce serious disease outbreaks.

Nonspecific reactions in an enzyme-linked immunosorbent assay caused by binding of immunoglobulins in situ to egg-propagated infectious bronchitis virus.

High levels of nonspecific background absorbance and increased variability were found in a previously optimized enzyme-linked immunosorbent assay (ELISA) for infectious bronchitis virus (IBV) antibody after changing to commercially available non-pathogen-free eggs for viral antigen production. An increase in bound viral antigen in the assay caused a proportionate increase in the nonspecific binding of the conjugate, independent of other variables, in the absence of serum. Virus was propagated in non-pathogen-free eggs, and individual viral proteins were separated by polyacrylamide gel electrophoresis and transferred to nitrocellulose. Localization of chicken IgG-virus complexes were identified by immunoprecipitation with peroxidase-conjugated anti-chicken IgG. Specific staining at molecular weights corresponding to major proteins of IBV was demonstrated in these viral preparations. Virus grown in specific-pathogen-free eggs and treated in the same manner showed only slight amounts of staining. This evidence suggests that viral antigens grown in eggs from a non-pathogen-free flock bind with maternal chicken immunoglobulins present in the allantoic cavity of eggs. This IgG caused nonspecific reactions in our chicken ELISA system and gives cause for concern in any diagnostic system requiring the propagation of agents in fertile eggs.