An experimental infection model to induce digital dermatitis infection in cattle

Bovine digital dermatitis (DD), also known as papillomatous digital dermatitis (foot warts), has been recognized as a major cause of lameness in cattle, with important economic and welfare consequences. The evaluation of therapeutic and preventive interventions aiming to control DD infections in dairy cattle is often challenged by the complex multifactorial etiology of the disease. An experimental infection model to induce acute DD lesions in a controlled environment is proposed. The goal was to provide a standard way of reproducing DD infections independent of external factors that could confound the natural course of the disease, such as management practices or infection pressure, resulting in transmission of DD between animals. A group of 4 yearling Holstein heifers free of any clinical evidence of hoof disease was recruited from a commercial dairy farm and housed in an experimental facility in 1 pen with slatted flooring. The hind feet were wrapped to mimic conditions of prolonged moisture (maceration) and reduced access to air (closure) and inoculated at the heel and dewclaw areas with a homogenate of a naturally occurring DD lesion skin biopsy or a culture broth of Treponema spp. After a period of 12 to 25 d, 4 of 6 and 1 of 4 dewclaw areas inoculated with biopsied DD lesion or a Treponema spp. culture, respectively, had gross lesions compatible with DD. Histopathology confirmed the gross diagnosis in the sites inoculated with tissue homogenate. In the site inoculated with Treponema spp. culture broth, histopathology revealed an incipient DD lesion. Treponema spp. were detected by PCR in both naturally occurring DD homogenate and Treponema spp. culture broth inoculation sites. An experimental infection model to induce acute DD in cattle was developed, which may be used to evaluate interventions to control DD and study the pathogenesis of this infectious hoof disease in a controlled manner.

Zygomycotic Lymphadenitis in Slaughtered Feedlot Cattle

During the 12 months of 2006, zygomycotic lymphadenitis was diagnosed in 194 of 198 feedlot steers (0.04% of cattle slaughtered during that period) in a California slaughterhouse as part of bovine tuberculosis surveillance. Mesenteric lymph nodes were involved in 190 cases. Affected lymph nodes were enlarged (2 to 42 cm in greatest dimension), firm, and mottled gray-white to yellow with multiple granular or caseocalcareous foci. Histologically, nodal architecture was effaced by necrosis, granulomatous inflammation, and fibrosis. In approximately 20% of the cases, granulomas were mainly restricted to subcapsular sinuses and afferent lymphatic vessels, causing granulomatous lymphangitis. Nonseptate, irregularly branching hyphae with nonparallel walls and bulbous enlargements were common in necrotic areas and within the cytoplasm of multinucleated giant cells. Fungal cultures were performed on 124 affected lymph nodes using 7 media, but no zygomycetes were cultured. Fungal DNA was amplified from 20 lymph nodes. Amplicons from 16 nodes had nearly 100% homology with sequences for Rhizomucor pusillus; 4 amplicons had (> 98%) homology with Absidia corymbifera sequences. Zygomycosis should be considered in the differential diagnosis for granulomatous lymphadenitis in feedlot steers.

Genetic diversity of bovine ulcerative mammary dermatitis-associated Treponema

The etiology of bovine ulcerative mammary dermatitis (UMD) is poorly characterized. The goal of this study was to genetically analyze spirochetes present in UMD lesions. DNA prepared from UMD lesion biopsies and from spirochetes cultured from the corresponding lesion biopsies was PCR amplified using primers for the 16S rDNA-tRNA(ile) intergenic spacer region (ISR) of Treponema 16S-23S rDNA. Analysis of cloned ISR amplicons from three cultivable UMD-associated spirochetes indicated that two isolates cluster closely with cultivable papillomatous digital dermatitis (PDD)-associated and human-associated Treponema phylotypes, while the remaining isolate is unique. Analysis of ISR amplicons from UMD lesion biopsies identified additional not-yet-cultivable Treponema phylotypes. Our results revealed the presence of a genetically diverse Treponema population in an UMD lesion.

Equine abortion associated with the Borrelia parkeri-B. turicatae tick-borne relapsing fever spirochete group

Direct amplification and sequencing of the 16S rRNA gene and a variable region of the flagellin gene from fetal liver-associated spirochetes belonging to the Borrelia parkeri-B. turicatae tick-borne relapsing fever spirochete group with a late-term abortion in a mare are described.

Genetic identification and characterization of a novel virus related to human hepatitis E virus from chickens with hepatitis-splenomegaly syndrome in the United States

Hepatitis-splenomegaly (HS) syndrome is an emerging disease in chickens in North America; the cause of this disease is unknown. In this study, the genetic identification and characterization of a novel virus related to human hepatitis E virus (HEV) isolated from bile samples of chickens with HS syndrome is reported. Based upon the similar genomic organization and significant sequence identity of this virus with HEV, the virus has been tentatively named avian HEV in order to distinguish it from human and swine HEV. Electron microscopy revealed that avian HEV is a non-enveloped virus particle of 30-35 nm in diameter. The sequence of the 3' half of the viral genome ( approximately 4 kb) was determined. Sequence analyses revealed that this genomic region contains the complete 3' non-coding region, the complete genes from open reading frames (ORFs) 2 and 3, the complete RNA-dependent RNA polymerase (RdRp) gene and a partial helicase gene from ORF 1. The helicase gene is the most conserved gene between avian HEV and other HEV strains, displaying 58-61% aa and 57-60% nt sequence identities. The RdRp gene of avian HEV shares 47-50% aa and 52-53% nt sequence identities and the putative capsid gene (ORF 2) of avian HEV shares 48-49% aa and 48-51% nt sequence identities with the corresponding regions of other known HEV strains. Phylogenetic analysis indicates that avian HEV is genetically related to, but distinct from, other known HEV strains. This discovery has important implications for HEV animal models, nomenclature and natural history.

Pathologic and bacteriologic findings in 27-week-old commercial laying hens experimentally infected with Salmonella enteritidis, phage type 4

Two strains of 27-wk-old commercial laying chickens (strain A, brown-egg-laying type and strain B, white-egg-laying type) were inoculated either orally (PO) or intravenously (IV) with a field isolate of Salmonella enteritidis phage type 4. Chickens were sequentially necropsied at regular intervals throughout the 17-wk observation period. Gross and microscopic lesions were most evident between 1 and 14 days postinoculation (DPI). Gross lesions consisted of enlarged livers with white foci, enlarged and mottled white spleens, fibrinous exudate in the peritoneum, and atretic, misshapen ovarian follicles. Microscopic lesions included multifocal coagulative necrosis of hepatocytes and inflammation, fibrinous exudation in vascular sinuses of the spleen, and fibrinosuppurative inflammation of the peritoneum and ovarian follicles. The proportion of reproductive organ infections (ovary and oviduct) in the IV group, 83% (20/24, P = 0.007; 50% and 33% for strains A and strain B birds, respectively), was higher than that of the PO group, 46% (11/24; 29% and 17% for strains A and B, respectively), for the first 16 days of observation postinoculation. The proportion of fecal shedding for the IV group of birds was significantly (P = 0.009) lower, 29% (7/24; 33% and 25% respectively for strain A and strain B birds, respectively), than the PO group, 67% (16/24; 75% and 58% for strain A and strain B birds, respectively). Three (2.6%) of 234 egg pools were culture-positive for group D Salmonella from strain A chickens (1 of 119 pools from the IV group and 2 of 115 pools from the PO group of birds). Chickens infected with the field strain of S. enteritidis phage type 4 harbored the organism in tissues only for a brief time, most clearing within 8 DPI and nearly all within 16 DPI. Overall the percentage of culture-positive birds did not differ significantly (P > 0.05) between birds with and without lesions, but isolation of S. enteritidis tended to be more frequent when lesions were evident. This experiment also demonstrated that brown-egg-laying-type chickens were more susceptible than white-egg-laying-type chickens to S. enteritidis phage type 4 isolated from California based on gross and microscopic lesions and bacteriologic findings.

Farm- and host-level risk factors for papillomatous digital dermatitis in Chilean dairy cattle

A cross-sectional study was conducted in southern Chile between January and March, 1996, to identify risk factors for papillomatous digital dermatitis (PDD) in lactating dairy and dual-purpose cows. A total of 3,265 cows from 22 farms were examined in the milking parlor for PDD lesions. Additional information was collected from dairies' computerized records and by direct interview of managers. Data were analyzed using logistic and logistic-binomial regression (with dairy as a random-effect term). German Red-Pied (dual-purpose) cows were significantly (P < 0.05) less likely (odds ratio (OR) = 0.3) to have PDD lesions than German Black-Pied and Holstein crossbreds. First-parity cows had the highest odds of PDD, and odds diminished, in a dose-effect manner, as parity increased. Odds of PDD increased with increasing days in lactation. Cows that calved during winter were more likely to have PDD (OR = 1.4) than those calving at any other season. Cows on farms that bought heifers in the past 10 years had a 3-fold increase in the odds of PDD compared to those on farms that never bought heifers. Loose-housed cows had a higher risk of PDD (OR = 7), followed by cows in free stalls or in open corrals (OR = 2.8 and 1.3, respectively), compared to cows on pasture all year. Cows on dairies that used a footbath during 1996 were less likely (OR = 0.3) to have PDD than those in dairies not using one. Parlor type was associated with PDD, but this was likely an effect of parlor design on ease of inspection of cows' feet. A policy of trimming all cows' vs. only lame cows' feet and a policy about buying adult cows did not have significant effects on PDD risk.

Papillomatous digital dermatitis in Chilean dairies and evaluation of a screening method

Outbreaks of papillomatous digital dermatitis (PDD) have been reported from many countries, but there is little information on prevalence and geographic distribution of the disease. Our objectives were to describe prevalence of PDD on dairies belonging to the two main dairy-producer associations in Chile, and to evaluate a milking-parlor screening method for detection of PDD in dairy cows. First, a self-administered questionnaire was sent to all 214 association dairy managers. Seventy percent of the 119 respondents had observed PDD on their dairies. About 83% of the 63 responding managers had first seen PDD during the previous 10 years. Subsequently, a random sample of 43 dairies stratified by association was selected from the total 214 for PDD screening. During milking, we inspected cows' feet for PDD lesions; 91% of dairies had cows affected by PDD; median PDD prevalence for milking cows in dairies was 6.1%. Finally, in one dairy, PDD screening at the parlor was compared to PDD diagnosis by inspecting restrained cows in a chute. The screening method had a sensitivity of 0.72, and a specificity of 0.99. This study demonstrated that PDD was widespread on study dairies in Chile. The screening test presented can be used as a cost efficient method to estimate prevalence of PDD either on individual dairies or in large-scale surveys.

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.

Association between long periods without high-speed workouts and risk of complete humeral or pelvic fracture in thoroughbred racehorses: 54 cases (1991-1994)

OBJECTIVE

To determine whether a two-month or longer period without official high-speed workouts (lay-up) is associated with humeral or pelvic fracture in Thoroughbred racehorses.

DESIGN

Reprospective study.

ANIMALS

Thoroughbred racehorses in California that were euthanatized because of a complete humeral or pelvic fracture.

PROCEDURE

Age, sex, activity, number of lay-ups, number of days from a race or official timed workout to fracture, number of days from end of last lay-up to fracture, mean duration of lay-ups, and total number of days in race training were compared between horses with humeral fractures and horses with pelvic fractures. A case-crossover study was used to estimate relative risk for fracture of the humerus or pelvis occurring within hazard periods of 10 and 21 days following lay-up, compared with periods following more regular participation in official racing or timed workout events.

RESULTS

Horses with pelvic fractures were more often female, older, and had 0 or > or = 2 lay-ups. Horses with humeral fractures were typically 3-year-old males that had 1 lay-up. Horses with pelvic fractures had more total days in race training, fewer days from last exercise event to fracture, and a greater number of days from end of last lay-up to fracture than horses with humeral fractures. Return from lay-up was strongly associated with risk for humeral fracture during hazard periods of 10 and 21 days (relative risk = 71 and 45, respectively).

CLINICAL IMPLICATIONS

Risk of humeral fracture may be reduced if horses are cautiously reintroduced into race training after lay-up.

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.

Papillomatous digital dermatitis (footwarts) in California dairy cattle: clinical and gross pathologic findings

Clinical, gross pathologic, and therapeutic studies were performed on a contagious, painful, wart-like digital disease of unknown etiology in California dairy cattle. The disease was called papillomatous digital dermatitis (PDD). Survey indicated that the disease spread geographically throughout southern California over the past few years. In 1991, 31% of herds had papillomatous digital dermatitis, whereas in 1994, 89% were affected. Increased incidence occurred during late spring and summer, 1-3 months after the rainy season. Within-herd morbidity ranged from 0.5% to 12% per month. Study of 93 cows in 10 drylot dairies revealed that 91% had characteristic circumscribed, erosive to papillomatous, intensely painful lesions often surrounded by a ridge of hyperkeratotic skin bearing hypertrophied hairs. Lesions were 2-6 cm across (88%), circular to oval (78%), and raised (59%) and had surfaces that were uniformly erosive and granular (31%), uniformly papillary (28%), or composites of both appearances (41%). Lesions were most frequently seen in lactating heifers (31%) and 3-year-old cows (43%). Clinical signs were characterized by lameness, with walking on toes and clubbing of hooves. Lesions exclusively involved the hind limbs in 82% of cows and the plantar/palmar regions in 84% of cows. Lesions had high (89%) prediliction for plantar/palmar skin bordering the interdigital space. Lesions exclusively involved either the medial or lateral digit in 10% and 28% of cows, respectively. In 50% of cows, both medial and lateral digits of individual limbs were involved; in most cows (31%), lesions apposed each other across the plantar interdigital space, whereas in others (19%), lesions confluently involved the entire plantar/palmar commissural skin folds. In another 12% of cows, lesions were axial. High proportions of lesions showed complete therapeutic responses to antibiotics: parenteral penicillin (9/9) and ceftiofur (41/44), and topical oxytetracycline (4/4). Recurrence or new lesion development occurred in 48% of cows reexamined 7-12 weeks after complete therapeutic response was observed. Overall, the findings indicated that PDD is a distinct disease entity of economic importance in which bacteria may play an important pathogenic role.

Papillomatous digital dermatitis on a commercial dairy farm in Mexicali, Mexico: incidence and effect on reproduction and milk production

This retrospective study of papillomatous digital dermatitis (PDD) was performed using data for cows that calved between July 1993 and June 1994 on a Mexicali, Mexico, dairy farm in order to calculate incidence rates, and to compare milk yield and reproduction data between affected and nonaffected dairy cows. A total of 190 out of 577 (33%) cows were affected during lactation and six (1%) during the dry period. Fifty-two of 77 (68%) cows that had lesions in the previous lactation and were also present on the farm in the current lactation had lesions in the current lactation. The highest risk for PDD occurred during the first month of lactation (9%). The yearly estimated cumulative incidence risk was 35% and the incidence density rate was 44.6 cases per 1000 cow-months. More animals were affected in summer and fall than in winter and spring. Purchased animals were 3.4 times more likely to be affected than animals born on the farm. Survival analyses indicated healthy cows conceived 93 days after calving (median), but affected cows conceived 113 days after calving (median) (P < 0.01). PDD-affected animals produced less milk than healthy cows, but the difference was not statistically significant in the multiple regression.

Humoral response of dairy cattle to spirochetes isolated from papillomatous digital dermatitis lesions

OBJECTIVE

To determine whether a humoral response against spirochetes isolated from papillomatous digital dermatitis (PDD) lesions is elicited in dairy cattle affected with PDD.

SAMPLE POPULATION

41 cattle with PDD from 8 dairies (study population) and 30 cattle from 2 dairies free of PDD (control population). Additionally evaluated were 32 cattle from a dairy with a past history of PDD but no current disease, and 52 cattle from a dairy with high prevalence of PDD, 25 with and 27 without detectable lesions.

PROCEDURE

ELISA were used to evaluate the humoral response of all cattle to representative isolates from 2 groups of spirochetes of unknown species isolated from PDD lesions. Specificity of the response was evaluated, using immune sera prepared against each of the spirochetes, and by adsorption studies of immune and field sera. The potential for confounding by an antibody response to other spirochetes associated with diseases of cattle was assessed.

RESULTS

The antibody response (specific) to both PDD spirochete groups of cows with PDD was significantly increased, compared with that of cows from PDD-free dairies. There was no association between antibody response to PDD-associated spirochetes and antibody response to other spirochetal diseases of cattle. None of the cattle from the dairy with previous history of PDD but without current disease were classified as test positive by either PDD ELISA. There was a significant (P < 0.01) difference in classification results for both PDD ELISA for cattle with PDD from the dairy with a high herd prevalence of PDD, compared with cattle without detectable disease from the same dairy.

CONCLUSIONS AND CLINICAL RELEVANCE

The humoral response in cattle with PDD lesions was significantly different from that in cattle without detectable lesions, thus providing additional information regarding the potential role of spirochetes isolated from PDD lesions in the etiopathogenesis of PDD.

Acute hemorrhagic pulmonary infarction and necrotizing pneumonia in horses: 21 cases (1967-1993)

OBJECTIVE

To characterize history, clinical signs, and pathologic findings in horses with histologically confirmed acute hemorrhagic pulmonary infarction and necrotizing pneumonia.

DESIGN

Retrospective study.

ANIMALS

21 horses.

RESULTS

19 of the 21 horses were Thoroughbred racehorses in training. Eighteen horses had had strenuous exercise immediately prior to onset of illness. Fifteen horses had a serosanguineous nasal discharge during hospitalization. Seventeen horses had radiographic evidence of pulmonary consolidation and pleural effusion. Nine of 14 horses had ultrasonographic evidence of large pulmonary parenchymal defects consistent with consolidation. Pleurocentesis yielded a suppurative, serosanguineous effusion in the 14 horses in which it was performed. Bacteria were isolated from all transtracheal aspirates (14) and from 6 of 12 pleural fluid samples. Actinobacillus suis-like organisms and Streptococcus equi subsp zooepidemicus were most commonly isolated. Nineteen horses were hospitalized and treated. Mean duration of treatment was 5 days, and most horses were euthanatized because of secondary complications, continued costs of medical treatment, or poor prognosis for future performance. Pathologic lesions included well-demarcated regions of hemorrhagic pulmonary infarction with necrosis and a serosanguineous pleural effusion. Thrombosis of pulmonary vessels was found in 11 horses.

CLINICAL IMPLICATIONS

An acute or peracute onset of severe respiratory distress, with serosanguineous nasal discharge, ultrasonographic and radiographic evidence of severe pulmonary consolidation, and serosanguineous suppurative pleural effusion, is strongly suggestive of pulmonary infarction in horses. Horses with pulmonary infarction responded poorly to conventional treatment for pleuropneumonia and had a poor prognosis for recovery.

Prevalence of Salmonella in municipal sewage treatment plant effluents in southern California

Effluents from 12 sewage treatment plants in southern California were examined for Salmonella using a Moore swab technique. Eight of the 12 plants were positive for Salmonella when sampled at the chlorination/dechlorination site (inside the plant). Effluents from 11 of 12 sewage treatment plants were positive for Salmonella when samples were analyzed downstream of the chlorination/dechlorination site, before effluents merge with the receiving stream (outside the plant). Two of the three control sites, an urban runoff, a raw potable water reservoir, and two other sites were also positive for Salmonella. A total of 683 Salmonella isolations were represented by 11 serogroups and 54 serotypes from 26 of 32 sampling sites. Effluents from three treatment plants and one control site (raw potable water resevior) yielded Salmonella enteritidis phage type 4, in addition to other serotypes.

Papillomatous digital dermatitis in 458 dairies

OBJECTIVE

To estimate prevalence of papillomatous digital dermatitis (PDD) in California dairies during 1993, to describe temporal and spatial patterns of PDD and response of cows to treatment, and to evaluate herd-related risk factors for PDD.

DESIGN

Epidemiologic survey.

SAMPLE POPULATION

All southern California dairies and a 50% random sample of the rest of California dairies.

PROCEDURE

A questionnaire was mailed to managers of 1,429 selected dairies.

RESULTS

Prevalence of PDD during 1993 was significantly higher for dairies in the south (75.3%) and central (68.8%) regions, compared with north coast (33.3%) and north (23.1%) regions of the state. Herd mean and median proportions of affected cows in PDD-affected herds were 11.6 (SEM = 0.9) and 5%, respectively. Most (74%) dairy managers surveyed observed PDD for the first time during 1992 or 1993. Highest PDD activity was reported as taking place in summer in the south and in fall and winter in the north coast and north regions; an obvious pattern was not determined for the central region.

CLINICAL IMPLICATIONS

PDD was widespread in California dairies during 1993 and affected a high proportion of cows, especially in the south and central regions of the state.

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.

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.

Sewage effluent: likely source of Salmonella enteritidis, phage type 4 infection in a commercial chicken layer flock in southern California

Following the diagnosis of Salmonella enteritidis, phage type 4, infection in a commercial layer flock in southern California, effluent from a nearby sewer treatment plant was investigated as a potential source of infection. Between July 1994 and March 1995, 68 Salmonella isolations, comprising 27 serotypes, were made from the inflow (raw sewage) and effluent (treated sewage). Thirty-nine of 68 (57%) isolations yielded six serotypes, which consisted of S. enteritidis 12% (8/68), S. cerro 10% (7/68), S. typhimurium 7.4% (5/68), S. tennessee 7.4% (5/68), S. give 7.4% (5/68), S. mbandaka 7.4% (5/68), and S. panama 6% (4/68). The remaining 43% (29/68) isolations were represented by 21 serotypes. Seventeen S. enteritidis isolates originating from the effluent (creek water), resident feral animals (rodents, stray cats, skunks), and chickens (organs, eggs) of the affected flock were subjected to plasmid profile and restriction endonuclease analysis. Twelve of the 17 isolates had identical plasmid profile and restriction digestion patterns. Two of 17 isolates showed similar patterns but both differed from the rest; and 1 of 17 did not yield plasmids. Two other isolates were found to be different from each other and from the rest of the group.

Salmonella enteritidis, phase type 4 infection in a commercial layer flock in southern California: bacteriologic and epidemiologic findings

Salmonella enteritidis, phage type 4 (SE PT4), was isolated from five of six 27-wk-old layer chickens submitted for necropsy from a flock of 43,000. Bacteriologic and epidemiologic investigations on the ranch revealed that five of the eight flocks (n = 176,000) were infected. The prevalence of SE PT4 in randomly selected healthy birds ranged from 1.7% (in caged birds) to 50% (in free-range birds) and prevalence in culled birds (kept on dirt floor houses) ranged from 14% to 42%. The estimated overall prevalence of group D Salmonella in eggs contaminated with group D Salmonella was 2.28 per 10,000. The estimated prevalence of group D Salmonella in eggs from caged birds in three infected houses ranged from 1.5 to 4.1 per 10,000, whereas in two houses of free-range birds, prevalence was 14.9 to 19.1 per 10,000. Three of the eight flocks on the ranch remained negative for Salmonella between May 1994 and December 1995 or until removed from the ranch. Salmonella enteritidis PT4 was also isolated from 12.5% (6 of 48) of mice; 57% (four of seven) of cats; and two of two skunks tested. Environmental drag swabs and well water samples yielded multiple serotypes of Salmonella (23/180 and 5/14, respectively) but not S. enteritidis.

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.

Spirochetes isolated from dairy cattle with papillomatous digital dermatitis and interdigital dermatitis

Two groups of spirochetes were isolated from papillomatous digital dermatitis (PDD) lesions in dairy cattle. The two groups could be readily differentiated on the basis of morphologic and immunologic characteristics and enzymatic activity. A spirochete isolated from an interdigital dermatitis (IDD) lesion appeared morphologically and antigenically similar to spirochetes in one of the PDD groups and exhibited an identical enzyme activity pattern. The two groups of PDD spirochetes had characteristics most consistent with the genus Treponema. The PDD and IDD isolates differed morphologically from previously described bovine Treponema spp. Although spirochetes have been observed to be one of the predominant bacterial morphotypes in PDD and IDD and are found invading the stratum spinosum and dermal papillae in PDD lesions, the significance of these spirochetes in the etiopathogenesis of PDD and IDD is presently unknown.

Causes of death in racehorses over a 2 year period

Necropsies were performed on 496 horses that had a fatal injury or illness at a California racetrack during the period February 20th 1990 to March 1st 1992. The primary cause of death was categorised by breed, activity at time of injury or illness and organ system affected. Most of the submissions were Thoroughbred horses (432) and Quarter Horses (46). Most of the injuries occurred while racing (42%) and in training sessions (39%); with fewer non-exercise (12%) and accident (7%) related injuries or illnesses. Musculoskeletal injuries accounted for 83% of the Thoroughbred and 80% of the Quarter Horse submissions. The Thoroughbred horses incurred 306 fractures with 263 in the limbs and 90% of those in the forelimbs. The proximal sesamoid bone(s), third metacarpal bone and humerus were the most common bones fractured in Thoroughbred horses and Quarter Horses. Other major causes of death included respiratory, digestive and multi-organ system disorders.

Tracheal aspergillosis in 6 1/2-week-old chickens caused by Aspergillus flavus

A case of localized tracheal aspergillosis in 6 1/2-week-old single-comb white leghorn pullets caused by Aspergillus flavus is documented. Yellow caseous plaques adherent to the mucosal surface of the tracheas were observed grossly. In several tracheas, the plaques occluded the lumina, and the surrounding tracheal walls were reddened. Histologically, the mucosa was necrotic and infiltrated with macrophages, and fibroplasia was evident in the subadjacent tracheal wall. The lumen of the trachea was almost completely occluded by a combination of fungal mycelia and pyogranulomatous exudate. Portions of tracheal cartilage were elevated into the lumen of the trachea. Other than a sudden increase in mortality to 0.5% per day, there was no evidence of disease in the flock. Depletion of bursal lymphocytes, with concomitant cryptosporidiosis, was evident on histological examination. Acute infectious bursal disease was diagnosed in the succeeding flock at this ranch based upon serology and typical histology.

An association between complete and incomplete stress fractures of the humerus in racehorses

Twenty-one horses had a complete unilateral humeral fracture during race training or racing at a California racetrack during the period 24 February 1990 to 10 July 1991. Fractures occurred approximately equally in left and right limbs, and in males and females. Most fractures occurred during training, and in 2- and 3-year-old horses. Only 5 of 16 Thoroughbred horses with known racing records had previously raced more than once, and their mean time between races was less than the time between their last race and fracture (P = 0.07). Ten of 13 humeri studied further had gross evidence of periosteal callus bridging one portion of the fracture line, indicative of a pre-existing stress fracture.

Hyperglycemia and reproductive defects in non-diabetic gravidas: a mouse model test of a new theory

The frequent association of various reproductive anomalies with maternal diabetes is explained by a theory that predicts such defects will occur even in transient moderate hyperglycemia in non-diabetic gravidae. A first test of this hypothesis produced strongly supportive results in a mouse model. Thirteen C57BL/6J dams on a grain (control) diet produced (in the 4th week after first mating) 64 pups, 62 surviving to maturity. In the same time interval on a high sucrose diet, fourteen isogenic dams produced only 5 pups, none surviving 5 days (p much less than .001). Additional ongoing studies of the underlying glucose-ascorbate antagonism and of early vs. perinatal hyperglycemia are described briefly.

Experimentally induced thiamine deficiency in beagle dogs: pathologic changes of the central nervous system

Brain and spinal cord were examined in twenty-two 2- to 5-month-old Beagle dogs fed a purified thiamine-deficient ration for 84 +/- 42 (range, 32 to 134) days. Eleven dogs were used as principals, 6 were pair-fed controls, and 5 were controls fed ad libitum. Thiamine at 300 micrograms/kg of body weight was administered IM to control groups once a week. Lesions occurred in 2 topographic patterns in the brain of 8 of the principals. In pattern I, only the caudal colliculi were involved. In pattern II, the suprasplenial gyri of the cerebral cortex and the claustra, caudal colliculi, cerebellar nodulus, and medial vestibular nuclei were commonly involved. In both patterns I and II, gray matter was primarily involved, and in bilateral structures, the 2 sides were affected. Lesions were not limited to a given cerebral lamina or layer of the cerebellum, whereas sulcal areas were relatively spared, and the cingulate gyri were completely spared. Microscopic appearance of the lesions varied greatly among locations and individual principals. Collectively, regressive and reparative changes indicated that there was a progressive process which began with spongiosis and ended with tissue necrosis. These included hydropic vacuolation of the neuropil and myelin sheaths followed by demyelination, neuronal cell body necrosis, hypertrophy and hyperplasia of endothelial cells, necrosis of glia, neutrophil infiltration, disintegration of neuropil, and, finally, accumulation of lipid-containing phagocytes. Axonal degeneration was variable. Neuronal necrosis in the brain stem was characterized by acute swelling and lysis and by shrinkage of the cell body in cerebral and cerebellar cortex and basal ganglia.

Bovine post-parturient haemoglobinuria: two distinct entities in New Zealand

Haematological and biochemical features of sixteen cases of post-parturient haemoglobinuria (PPH) from 15 farms in the Waikato and Bay of Plenty regions are described. Characteristically there was a marked regenerative anaemia as well as spherocytosis and haemoglobinaemia. Heinz body formation occurred in 140% of erythrocytes depending on the case. Nine of 11 cases examined had subnormal serum inorganic phosphorus concentrations. On two of eight farms there was widespread anaemia in clinically healthy herd mates and in one of these the anaemia was associated with large numbers of Heinz bodies. Hypophosphataemia was widespread in four of ten herds and individual cows were hypophosphataemic in all ten. Six of eight herds had a low selenium status as determined by glutathione peroxidase activity in whole blood. Hypocupraemia and hypomagnesaemia were not consistent findings. It is concluded that there are two distinct entities of PPH in the region. On one farm the disease was typical of that seen in Northland, New Zealand. The clinical case was a young cow and there was widespread subclinical Heinz body anaemia in herd mates. All but one of the cows sampled in that herd had normal serum inorganic phosphorus levels. On most other farms PPH closely resembled that described from North America. Affected cases were miltiparous, high producing and had low serum inorganic phosphorus levels. The possible pathogenesis of these two entities is discussed.

Glycemic modulation of tumor tolerance in a mouse model of breast cancer

Marked sensitivity of tumor tolerance to blood glucose level is demonstrated in a mouse model of human breast cancer. A theory is cited that explains the high association of hyperglycemia with malignancy, especially breast cancer, via glycemic modulation of cellular immunity. Three groups of BALB/C mice were injected with an aggressive mammary tumor and placed on three dietary regimens designed to produce three different glycemic levels. Mortalities 70 days after injection were 16 of 24 hyperglycemic mice, 8 of 24 normoglycemic, and 1 of 20 hypoglycemic (chi-square p less than .005). Taken together with other experiments and human data discussed briefly, this result suggests that glycemic modulation of tumor tolerance should be evaluated in human trials.

Osmolal excretion after open heart surgery

Water and osmolal balance was investigated during the peri-operative period in twenty unselected adult patients presenting for open heart surgery. On the day before surgery the mean urine output was 1.13 litres/sq m/24 hours and osmolal output 430 mOs/sq m/24 hours. Using a haemodilution cardiopulmonary bypass technique, patients received 2.62 litres/sq m and 792 mOs/sq m in the operating room. The pattern of excretion of this water and solute load was identified. Patients were still in positive balance on the day following surgery despite a considerable diuresis, with solute retention exceeding water retention.

Pre-oxygenation--how long?

Pre-oxygenation was studied in 12 fit volunteers and 20 patients using an oxygen flow of 8 litres/minute delivered from a standard anaesthetic machine via a Magill or Bain breathing attachment. End-tidal nitrogen concentrations of 4% or less were achieved within 3 minutes; the fastest times were achieved using the Magill breathing system when the reservoir bag was filled with oxygen prior to application to the face. Gas-tight fits of face masks on patients were found to be essential.

Adrenal and hepatic calcium stearate crystal deposits in dogs fed a thiamine-deficient diet

The nature and histologic environment of birefringent crystals found incidentally at necropsy in the liver and adrenal glands of dogs fed a thiamine-deficient diet were studied. The crystals were identified as calcium stearate by ultrastructural and x-ray microdiffraction techniques. Crystals were observed intracellularly within cytoplasmic vacuoles and extracellularly within sinusoids. Generally, crystals were also observed in pair-fed controls that were given a purified diet (equal in weight to that consumed by the thiamine-deficient animals) plus supplemental thiamine. Crystal deposits were found in trace amounts in a few of the ad libitum-fed controls. Although thiamine deficiency may be involved in promoting crystal deposition in the adrenal cortex, calcium stearate crystal formation within the adrenal glands and the liver appears unrelated to dietary thiamine deficiency per se, but is probably related to deficiency of an unidentified nutrient in the purified thiamine-deficient diet.

Experimentally induced thiamine deficiency in beagle dogs: clinical observations

Twenty-three 2- to 5-month-old Beagle dogs were fed a purified thiamine-deficient ration (2 to 3 micrograms of thiamine/100 g of ration) at a rate of 40 to 70 g/kg of body weight/day depending on age. Eleven dogs were used as principles, 6 as pair-fed controls, and 6 as ad libitum-fed controls. Controls were treated once a week with an IM dose of 300 micrograms of thiamine hydrochloride/kg of body weight. Three stages of clinical disease occurred in the principals: (i) an initial short (18.0 +/- 7.9 days) stage of induction, during which the dogs usually grew suboptimally, but were otherwise healthy, (ii) an intermediate stage of preliminary clinical signs of deficiency, characterized by a variable period (58.5 +/- 37.0 days) of progressive inappetance, failure to grow, loss of body weight, and coprophagia, and (iii) a terminal stage, which, in most dogs, was abrupt in onset and short (7.6 +/- 6.0 days) and consisted of either a neurologic syndrome or sudden unexpected death syndrome. Eight of the principals developed the neurologic syndrome characterized by anorexia, emesis, CNS depression, paraparesis, sensory ataxia, torticollis, circling, exophthalmos, tonic-clonic convulsions, profound muscular weakness, recumbency, and then died. Common reflex abnormalities included exaggerated patella reflex, proprioceptive and supporting reflex deficits, induced torticollis and ventroflexion of head, and absent eye menace (blink) reflex. Three other principals developed the sudden unexpected death syndrome. Common signs of deficiency were inappetance and paresis. Two were found dead and 1, with severe ECG abnormalities (including elevation of ST segment and tall or deeply inverted T waves), was killed.

Polioencephalomalacia of dogs with thiamine deficiency

A naturally occurring neurological disease occurred in six dogs fed cooked meat. Clinical signs were anorexia, progressive spastic paraparesis, recumbency, convulsions and death. The disease was characterized by bilaterally symmetrical spongy change and necrosis of brainstem nuclei with a lesion distribution pattern similar to that in thiamine deficient foxes and cats. An associated thiamine deficiency was evidenced by decreased thiamine levels in the blood of one dog and in the food of another, and rapid remission of clinical signs in a dog given thiamine hydrochloride. Thermal destruction of thiamine through cooking of the foods probably caused the dietary deficiency.

Neuronal-visceral GM1 gangliosidosis in a dog with beta-galactosidase deficiency

A 9-month-old dog with a history of progressive motor dysfunction was shown to have a deficiency in brain beta-galactosidase activity. The canine disease, like that of children with GM1 gangliosidosis, is characterized by accumulation of GM1 ganglioside in the brain, liver, and spleen, and membranous cytoplasmic bodies in neurons. The dog's pedigree suggests an autosomal recessive pattern of inheritance.