Sudden death caused by spinal cord injury associated with vertebral fractures and fetlock failure in a Thoroughbred racehorse.

The most prevalent causes of death in racehorses are musculoskeletal injuries, causing ~83% of deaths within the racing industry in California and elsewhere. The vast majority of these injuries have preexisting lesions that predispose to fatal injury. A 4-y-old Thoroughbred colt suffered an acute suspensory apparatus failure, including biaxial proximal sesamoid bone fractures of the right front fetlock, causing loss of support of the fetlock joint and consequent fall with fractures of the cervical and sacral spine. Cervical fracture caused spinal cord damage that resulted in sudden death. A preexisting lesion in the medial proximal sesamoid bone likely predisposed to complete fracture of this bone and fetlock breakdown. Interestingly, a comparable osteopenic lesion was present in the intact medial proximal sesamoid bone of the left forelimb, which is consistent with bilateral repetitive overuse injury in racehorses. The morphologic features of the cervical and sacral spine fractures were compatible with acute injury; no evidence of preexisting lesions was seen. Most likely, these acute vertebral fractures occurred as a result of the horse falling. This case emphasizes the importance of performing a detailed autopsy in horses that suffer an appendicular musculoskeletal injury, particularly in fatal cases when the horse dies following a leg injury.

Etiology and risk factors for bovine respiratory disease in pre-weaned calves on California dairies and calf ranches.

Our study objective was to estimate the magnitude of association of BRD risk factors including failure of passive immunity transfer, sex, age, and the detection of suspected BRD etiological pathogens in pre-weaned dairy calves in California. A conditional logistic regression model and a mixed-effects logistic regression model were used to estimate the association of these potential risk factors with BRD from a matched and nested case-control studies, respectively. For each exposure covariate, the odds ratio (OR) is the ratio of odds of an exposure in a BRD calf (case) to that in a non-BRD calf (control). In the matched case-control study, an interaction term between failure of transfer of passive immunity and sex of calf showed that female calves were more negatively impacted by failure of transfer of passive immunity compared to male calves. The odds ratios comparing failure of transfer of passive immunity in BRD score positive calves versus controls for male calves was 1.34 (95 % CI: 0.87, 2.06) and was 2.47 (95 % CI: 1.54, 3.96) for female calves. The model odds ratios varied from 1.74 (95 % CI: 1.26, 2.42) for Mycoplasma spp. to 9.18 (95 % CI: 2.60, 32.40) for Histophilus somni, with Mannheimia haemolytica and Pasteurella multocida having an OR of 6.64 (95 % CI: 4.39, 10.03) and 6.53 (95 % CI: 4.44, 9.59), respectively. For bovine respiratory syncytial virus positive calves, the OR was 4.60 (95 % CI: 3.04, 6.97). Findings from the nested case-control study showed that based on thoracic ultrasonography findings consistent with BRD, the odds of a calf being 1 day older compared to a day younger were 1.01 (95 % CI: 1.00, 1.02) among BRD cases. For the bacterial and viral pathogens, the OR for Mycoplasma spp. and Pasteurella multocida were 1.85 (95 % CI: 1.24, 2.75) and 1.86 (95 % CI: 1.28, 2.71), respectively. The OR values for these pathogens were similar when both thoracic auscultation and ultrasound findings were used to detect cases of BRD. Based on positive scores for BRD using the California BRD scoring system, the OR for facility type, calf ranch versus dairy farm, was 3.17 (95 % CI: 1.43, 7.01), Mannheimia haemolytica was 3.50 (95 % CI: 2.00, 6.11), Pasteurella multocida was 1.78 (95 % CI: 1.21, 2.60), and bovine coronavirus was 2.61 (95 % CI: 1.85, 3.70). Results from both study designs showed the difference in relative contributions of age, sex, immune status, and pathogens in BRD occurrence between cases and controls in pre-weaned dairy calves.

An outbreak of late-term abortions, premature births, and congenital deformities associated with a bovine viral diarrhea virus 1 subtype b that induces thrombocytopenia.

Bovine viral diarrhea virus 1 (BVDV-1) subtype b was isolated from premature Holstein calves from a dairy herd that experienced an outbreak of premature births, late-term abortions, brachygnathism, growth retardation, malformations of the brain and cranium, and rare extracranial skeletal malformations in calves born to first-calf heifers. Experimental inoculation of 3 colostrum-deprived calves aged 2-4 months old with this BVDV isolate resulted in thrombocytopenia, lymphopenia, and leukopenia. Outbreaks of brachygnathism are rarely associated with BVDV, and thrombocytopenia is rarely associated with BVDV-1 strains.

Malignant edema in postpartum dairy cattle.

Five cases of postparturient vulvovaginitis and metritis in cattle caused by Clostridium septicum (malignant edema) are described in the current report. The diagnosis was established based on detection of C. septicum by culture and fluorescent antibody test. All animals were Holsteins, and 4 were primiparous (the parity of 1 animal was not reported). All animals developed clinical signs 1-3 days after calving, consisting of swelling of perineal and perivulvar areas, fever, and depression. Perineal, perivulvar, and perivaginal gelatinous and often hemorrhagic edema was consistently observed on gross examination. Longitudinal vulvar, vaginal, cervical, and uterine body tears, covered by fibrinous exudates, were also present. Microscopically, vulvar, vaginal, and uterine mucosae were multifocally necrotic and ulcerated. Large Gram-positive rods, some with subterminal spores, were present within the edematous subcutaneous and submucosal tissues. Clostridium septicum was demonstrated by culture and/or fluorescent antibody test in tissues of most animals. These cases of malignant edema were considered to be produced by C. septicum and predisposed by the trauma occurring during parturition.

Antimicrobial resistance in Salmonella enterica subspecies enterica serovar Dublin from dairy source calves in the central San Joaquin Valley, California (1998-2002).

The present study describes antimicrobial resistance patterns of Salmonella enterica subspecies enterica serovar Dublin (S. Dublin) in clinical submissions from calves and temporal and farm-type trends in antimicrobial resistance patterns of the isolates. A total of 300 isolates of S. Dublin were obtained from fecal or internal organs of calves fewer than 120 days of age originating from 84 dairies and 18 calf ranches from July 1998 to December 2002. The isolates were susceptibility tested to a panel of 10 antimicrobials using the disk diffusion assay. Temporal and farm-type trends in individual antimicrobial inhibition zone sizes were assessed and antimicrobial resistance patterns were described using cluster analysis. Isolates obtained from calf ranches compared with dairies exhibited decreased susceptibility to florfenicol, gentamicin, neomycin, sulfisoxazole, sulfamethoxazole/trimethoprim, and tetracycline. During the years 1998-2002, decreasing susceptibility was seen for ceftiofur, enrofloxacin, and sulfamethoxazole/trimethoprim. There were 20 different antimicrobial resistance patterns in the isolate set, indicating that S. Dublin has the ability to transfer and pick up resistance genes with relative ease. The trends seen in antimicrobial resistance in S. Dublin may likely be linked to antimicrobial drug use in young calves.

Multiple episodes of 1080 (sodium monofluoroacetate) intoxication in a California calf-raising operation.

Over a 1-y period, a California calf-raising operation experienced 4 separate episodes of sudden death in 4-6-mo-old steers. Each episode occurred in 1-3 contiguous pens on 1 of 3 properties owned by the operation, but eventually all 3 properties were involved. In each episode, animals appeared normal at the evening feeding but at the subsequent morning feeding were found dead or dying. Remaining live calves had a stiff gait and were often dribbling urine, but did not show respiratory signs until they were down and agonal. At postmortem examination, calves consistently had moderate-to-large numbers of ecchymotic and suffusive hemorrhages on the epicardial surface and moderate-to-large amounts of fluid in the pericardial sac. Pulmonary edema and/or moderate amounts of watery fluid in the thoracic and abdominal cavities were present in a smaller percentage. On histologic examination, the myocardium had variable myofiber degeneration characterized by hypereosinophilia and fragmentation with mild interstitial infiltrates. Testing of heart and liver samples for monensin found levels lower than in previous cases of monensin toxicity. Rumen content was negative for oleandrin and grayanotoxins. Sodium monofluoroacetate (trade name: 1080) was consistently detected at ⩾10 ppb in kidney and liver, and was concluded to be the cause of the intoxication.

Parapoxviral vulvovaginitis in Holstein cows.

A group of Holstein first-calved heifers developed small pustules and ulcers on the vulva and in the vagina during the first 1-4 wk postpartum. The lesions varied from small red pinpoint foci to pustules and ulcers, 3-5 mm diameter. Some ulcers coalesced to form large ulcerated areas up to 15 mm diameter. In some animals, these ulcers progressed to become deep ulceration of the vaginal and vulvar mucosa with >50% of the mucosa involved. Vaginal biopsies from 4 heifers and vaginal individual swabs from 8 heifers for a combined sampling of 9 heifers were taken for clinical assessment. Six of the 9 heifers had parapoxvirus based on histopathology and/or PCR. Histologic examination of the biopsies of the pustules identified ballooning degeneration of the epithelium with degenerate epithelium containing eosinophilic intracytoplasmic inclusions consistent with a parapoxvirus in 3 of 4 biopsies. Testing for bovine herpesvirus 1, 2, and 4, bovine viral diarrhea virus, bovine papular stomatitis virus, and orf virus remained negative.

Pathology of blackleg in cattle in California, 1991-2015.

Blackleg is an infectious disease of cattle and rarely other ruminants, produced by Clostridium chauvoei and characterized by necrotizing myositis. In most cases of blackleg, the large muscles of the pectoral and pelvic girdles are affected, with other skeletal muscles and the heart involved less frequently. We studied 29 blackleg cases selected from the archives of the California Animal Health and Food Safety Laboratory, 1991-2015. Immunohistochemistry was also evaluated to detect C. chauvoei in formalin-fixed, paraffin-embedded (FFPE) tissues of cattle. Nineteen animals had gross and/or microscopic lesions in both skeletal muscle and heart, 9 had lesions in the skeletal musculature alone, and 1 in the heart alone. Gross lesions in the skeletal musculature involved the following muscle groups: hindquarters ( n = 8), forequarters ( n = 5), neck ( n = 5), lumbar area ( n = 3), brisket ( n = 2), diaphragm ( n = 2), abdominal wall ( n = 1), thoracic wall ( n = 1), and tongue ( n = 1). Of the 20 animals that had lesions in the heart, 11 had pericarditis and myocarditis; 7 had pericarditis, myocarditis, and endocarditis; and 1 each had pericarditis and myocarditis. Immunohistochemistry was 100% sensitive to detect C. chauvoei in FFPE skeletal muscle and/or heart of cattle with blackleg. Simultaneous lesions in skeletal musculature and heart were relatively common in blackleg cases in California; the most affected skeletal muscles were those of the hindlimbs.

Cecal infarction in neonatal calves.

Cecal infarction is an uncommon lesion in calves that results in localized peritonitis and, on occasion, perforation with secondary diffuse peritonitis and death. This lesion in calves has not been described previously. We reviewed the postmortem cases of cecal infarction in dairy calves ≤30 d of age that had been submitted over the course of 5 y to the Tulare branch of the California Animal Health and Food Safety Laboratory System. The area of cecal infarction and the associated lesion margins were examined histologically. Ischemic necrosis of the mucosal side of the cecal wall with various degrees of neutrophilic inflammation of subjacent tissues was found consistently, and thrombosis and vascular occlusion within the areas of necrosis and inflammation was found in 21 of 34 cases. Cecal infarction cases were then compared to controls using a retrospective matched case-control study design. Cases ( n = 34) and controls ( n = 86) were compared with respect to bacteremia (as defined by pure culture of a single bacterial agent from lung and/or liver), species of bacteria isolated, and for the presence of K99 Escherichia coli (calves ≤5 d), attaching and effacing E. coli, Cryptosporidium (calves ≥5 d of age), Salmonella isolation from the intestine, rotavirus, Bovine coronavirus, and Bovine viral diarrhea virus. In addition, the presence of rumenitis or abomasitis, and omphalitis were compared between cases and controls. There were no significant differences in ruminal, abomasal, or umbilical cord tissue inflammation, or pathogen test-positive status between cases and controls.

Outbreaks of bovine herpesvirus 2 infections in calves causing ear and facial skin lesions.

We describe 3 outbreaks of superficial dermatitis caused by bovine herpesvirus 2 (BoHV-2) in dairy breed calves. Clinically, all of the affected calves were 12-26 d of age, had alopecia and crusts on the face and ears, and were non-pruritic and afebrile. Affected animals recovered spontaneously without any treatment within 2-4 wk after onset of clinical signs based on 1 herd with follow up. Histologic examination of all skin crust or tissue samples identified neutrophilic inflammation, mild hyperkeratosis, multinucleate syncytial cells, and intranuclear inclusion bodies in the syncytial cells. Real-time PCR testing on affected surface crusts or tissue provided evidence of BoHV-2, and testing, where performed, was negative for parapoxvirus including bovine papular stomatitis virus and the ovine form of malignant catarrhal fever tested in EDTA blood samples. Bovine viral diarrhea virus also was negative by ELISA, as well as bovine herpesvirus 1 by immunohistochemistry. Direct electron microscopy of infected tissues in the first outbreak revealed herpesvirus-like particles.

Whole-Genome Sequencing and Concordance Between Antimicrobial Susceptibility Genotypes and Phenotypes of Bacterial Isolates Associated with Bovine Respiratory Disease.

Extended laboratory culture and antimicrobial susceptibility testing timelines hinder rapid species identification and susceptibility profiling of bacterial pathogens associated with bovine respiratory disease, the most prevalent cause of cattle mortality in the United States. Whole-genome sequencing offers a culture-independent alternative to current bacterial identification methods, but requires a library of bacterial reference genomes for comparison. To contribute new bacterial genome assemblies and evaluate genetic diversity and variation in antimicrobial resistance genotypes, whole-genome sequencing was performed on bovine respiratory disease-associated bacterial isolates (Histophilus somni, Mycoplasma bovis, Mannheimia haemolytica, and Pasteurella multocida) from dairy and beef cattle. One hundred genomically distinct assemblies were added to the NCBI database, doubling the available genomic sequences for these four species. Computer-based methods identified 11 predicted antimicrobial resistance genes in three species, with none being detected in M. bovis While computer-based analysis can identify antibiotic resistance genes within whole-genome sequences (genotype), it may not predict the actual antimicrobial resistance observed in a living organism (phenotype). Antimicrobial susceptibility testing on 64 H. somni, M. haemolytica, and P. multocida isolates had an overall concordance rate between genotype and phenotypic resistance to the associated class of antimicrobials of 72.7% (P < 0.001), showing substantial discordance. Concordance rates varied greatly among different antimicrobial, antibiotic resistance gene, and bacterial species combinations. This suggests that antimicrobial susceptibility phenotypes are needed to complement genomically predicted antibiotic resistance gene genotypes to better understand how the presence of antibiotic resistance genes within a given bacterial species could potentially impact optimal bovine respiratory disease treatment and morbidity/mortality outcomes.

Jejunal hematoma in cattle: a retrospective case analysis.

Sixteen years of adult cattle submissions to the California Animal Health and Food Safety Laboratory System were examined and data captured from cases with anaerobic cultures of intestinal content. Analysis was performed to determine if there were statistical differences between case submission types (nonbloody intestinal content [129 cases], bloody intestinal content [134 cases], and jejunal hematoma [JH; 51 cases]) for the presence of Clostridium perfringens (314 cases), C. perfringens toxinotypes (35 cases), and C. perfringens toxins (51 cases) in the content. Across submission types, significant differences were found in the isolation of C. perfringens between different specimen types (live cow, dead cow, or tissue from a field necropsy) with field samples being the most likely to have C. perfringens detected and live animals the least likely (P = 0.001). In cases of JH, detection of C. perfringens by enzyme-linked immunosorbent assay was more likely when a live or dead animal was submitted (P = 0.023) or when a live animal was submitted (P = 0.019) compared with submission of field necropsy tissues. These differences were not observed when cultures were performed to detect C. perfringens in cases of JH. There were no statistical differences between submission types with regard to any other variables evaluated. Detailed histologic examination of 21 cases of JH suggested disturbance of normal vascular or lymphatic function as the underlying problem in this entity.

Assessment of a fluorescent antibody test for the detection of antibodies against epizootic bovine abortion.

The current study was directed at developing and validating an indirect fluorescent antibody test (IFAT) capable of detecting antibodies specific for the agent of epizootic bovine abortion (aoEBA). Sensitivity and specificity was determined by comparing antibody titers from 114 fetuses infected with aoEBA with 68 fetuses diagnosed with alternate infectious etiologies. Data established specificity at 100% and sensitivity at 94.7% when cutoff criteria for a positive test were assigned at a titer of ≥1,000. Potential cross-reactivity was noted in samples from 3 fetuses with antibody titers of 10 or100; all were infected with Gram-positive organisms. The remaining 65 fetuses infected with microbes other than aoEBA, and an additional 12 negative reference sera, did not have detectable titers. The IFAT-based serology assay is rapid, reproducible, and unaffected by fluid color or opacity. Total fetal immunoglobulin (Ig)G was also evaluated as an aid for diagnosing EBA. Significantly higher concentrations of IgG were identified in fetuses infected with aoEBA as compared to those with alternate infectious etiologies. The presence of IgG is a sensitive indicator of EBA and increases the specificity of FAT-based serologic diagnosis when titers are 10 or 100. Taken together, serology and IgG analyses suggest that the incidence of EBA may be underestimated.

Systemic Bovine herpesvirus 1 infections in neonatal dairy calves.

During a 6-year period, 62 out of 2,980 calves examined (2.08%) between 1-30 days of age had lesions consistent with Bovine herpesvirus 1 infection. The mean and median age of affected calves was 14 days of age. Most cases of infection were in calves 12 and 15 days of age, with 34 calves (54.8%) affected; 14 calves (22.6%) were between 16-21 days of age; 11 calves (17.8%) were between 7-11 days of age; and 3 calves (4.8%) were between 22-30 days of age. In 29 of the calves, the adrenal gland was the only organ affected. In 25 calves, the adrenal gland and at least 1 other tissue had lesions consistent with herpes viral infection. Five animals had no adrenal lesions but had 1 or more additional tissue with lesions consistent with herpesvirus. Three animals had no adrenal gland present for examination but had lesions in other tissues. Organs and number of animals affected by Bovine herpesvirus 1 infection were adrenal gland (54), liver (18), lungs (15), kidney (8), small intestines (7), large intestines (7), rumen/omasum (7), trachea/larynx (3), abomasum (2), heart (1), esophagus (1), thymus (1), and lymph node (1).