Pathology of Clostridium perfringens type C enterotoxemia in horses.

Clostridium perfringens type C is an important cause of enteritis and enterocolitis in foals and occasionally in adult horses. The disease is a classic enterotoxemia, and the enteric lesions and systemic effects are caused primarily by beta toxin, 1 of 2 major toxins produced by C. perfringens type C. Until now, only sporadic cases of C. perfringens type C equine enterotoxemia have been reported. We present a comprehensive description of the lesions in 8 confirmed cases of type C enterotoxemia in foals and adult horses. Grossly, multifocal to segmental hemorrhage and thickening of the intestinal wall were most common in the small intestine, although the colon and cecum were also frequently affected. All horses had variable amounts of fluid, often hemorrhagic intestinal contents. The most characteristic microscopic lesion was necrotizing or necrohemorrhagic enteritis, with mucosal and/or submucosal thrombosis. Numerous gram-positive rods were occasionally seen in affected mucosa. A definitive diagnosis of C. perfringens type C enterotoxemia in all 8 cases was based on the clinical history, gross and histologic lesions, and detection of the beta toxin in intestinal contents.

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.

Study of laryngopharyngeal pathology in Thoroughbred horses in southern California.

REASONS FOR PERFORMING STUDY: There is increasing anecdotal evidence among horse owners, trainers and equine clinicians of a high prevalence of subepiglottic ulcers, suggested to have a negative effect on racing performance. OBJECTIVES: To provide a prevalence study and pathological characterisation of laryngopharyngeal lesions with emphasis in the subepiglottic area and, in particular, subepiglottic ulcers. METHODS: The study was carried out on 91 Thoroughbred racehorses received for post mortem examination from 4 major Southern California racetracks. The most common reason for submission was catastrophic musculoskeletal injury, but others include sudden death, laminitis, colic, colitis, neurological disorders, pleuropneumonia and arytenoid chondropathy. Laryngopharyngeal specimens were collected and examined grossly; selected cases were also examined histopathologically. RESULTS: Thirteen horses (143%) had at least one type of laryngopharyngeal abnormality, 7 horses (7.7%) had lesions in the subepiglottic soft tissues, including 4 subepiglottic ulcers, 2 soft palate 'kissing lesions' and one 'subepiglottic scar'. Eight horses (8.8%) had lesions elsewhere in the laryngopharynx, including mucosal ulcerations, arytenoid chondropathy, epiglottic entrapment and partial absence of arytenoid cartilage. CONCLUSIONS AND POTENTIAL RELEVANCE: Lesions in the subepiglottic area were among the most prevalent in this study, suggesting that an important percentage of laryngopharyngeal abnormalities may be missed during routine endoscopy of the standing horse, which often does not include the examination of subepiglottic tissues. Pathologically, subepiglottic ulcers were chronic-active with viable hyperplastic epithelial margins, suggesting that proper healing and re-epithelialisation should occur with appropriate treatment. In most cases, the lesions observed do not necessarily indicate a clinical problem and more extensive prevalence studies and correlation between abnormalities found and performance are needed to assess the clinical relevance of subepiglottic soft tissue lesions accurately.

Allele frequency and likely impact of the glycogen branching enzyme deficiency gene in Quarter Horse and Paint Horse populations.

Glycogen Branching Enzyme Deficiency (GBED), a fatal condition recently identified in fetuses and neonatal foals of the Quarter Horse and Paint Horse lineages, is caused by a nonsense mutation in codon 34 of the GBE1 gene, which prevents the synthesis of a functional GBE protein and severely disrupts glycogen metabolism. The aims of this project were to determine the mutant GBE1 allele frequency in random samples from the major relevant horse breeds, as well as the frequency with which GBED is associated with abortion and early neonatal death using the tissue archives from veterinary diagnostic laboratories. The mutant GBE1 allele frequency in registered Quarter Horse, Paint Horse, and Thoroughbred populations was 0.041, 0.036, and 0.000, respectively. Approximately 2.5% of fetal and early neonatal deaths in Quarter Horse-related breeds submitted to 2 different US diagnostic laboratories were homozygous for the mutant GBE1 allele, with the majority of these being abortions. Retrospective histopathology of the homozygotes detected periodic acid Schiff's (PAS)-positive inclusions in the cardiac or skeletal muscle, which is characteristic of GBED, in 8 out of the 9 cases. Pedigree and genotype analyses supported the hypothesis that GBED is inherited as a simple recessive trait from a single founder. The frequency with which GBED is associated with abortion and neonatal mortality in Quarter Horse-related breeds makes the DNA-based test valuable in determining specific diagnoses and designing matings that avoid conception of a GBED foal.

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).

Comparison of VIDAS enzyme-linked fluorescent immunoassay using Moore swab sampling and conventional culture method for Salmonella detection in bulk tank milk and in-line milk filters in California dairies.

A comparison of the VIDAS Salmonella (SLM) assay using the manufacturer's recommended sampling method or a Moore swab sampling method demonstrated that the Moore swab method detected a greater number of positive samples (83.0% vs. 67.92%). When results using a conventional culture technique were compared to the VIDAS SLM assay using Moore swab sampling, there was good agreement (97.5%). When the VIDAS SLM assay was used to test in-line milk filters and compared to results from the conventional culture method, there was also good correlation between test results (95.57%). Overall, the VIDAS SLM assay using a modified sampling method compared favorably to the conventional culture method and had the advantages of taking less time to obtain a negative or presumptive positive result, being less technically complicated and requiring less screening of non-lactose fermenting colonies from negative samples.

Mycoplasma infection in a commercial goat dairy caused by Mycoplasma agalactiae and Mycoplasma mycoides subsp. mycoides (caprine biotype).

A commercial dairy goat herd of 600 animals experienced sudden onset of arthritis/polyarthritis, clinical mastitis, and sudden death in does. The offending infectious agents were Mycoplasma agalactiae and M. mycoides subsp. mycoides (caprine biotype). The disease syndrome began approximately 4 weeks following the 1) introduction into the herd of a lactating doe with no apparent clinical signs and 2) a breakdown of proper hygienic conditions in the milking parlor. Over a period of 3 weeks, 90 does (15%) either died or were culled because of arthritis/polyarthritis and mastitis. A management decision resulted in only the does affected with M. mycoides subsp. mycoides being submitted for necropsy; those affected with M. agalactiae, which were in a different "string," were not submitted for evaluation. Gross necropsy of the does affected with M. mycoides subsp. mycoides showed purulent discharges from the udders, enlarged supramammary lymph nodes, enlarged and firm spleens, and swollen livers. Microscopic findings were characterized by a loss of vascular integrity and diffuse fluid leakage in multiple organs. Antibiotic therapy with tylosin was attempted but was not successful. The outbreak was terminated following the removal or segregation of affected does and implementation of hygienic conditions in the milking parlor.

Halicephalobus gingivalis (H. deletrix) infection in two horses in southern California.

Two horses, a 16-year-old male Holsteiner and a 5-year-old male miniature horse, were diagnosed with halicephalobiasis at the California Veterinary Diagnostic Laboratory System, San Bernardino Branch, in April and June of 1998. Over a period of 4 weeks, the Holsteiner horse developed renal dysfunction, blepharospasm, and blindness in the right eye. A 15-cm-diameter mass was detected on ultrasound examination in the right kidney. Terminally, the animal developed seizures and was euthanized. The miniature horse had a 6-week-long illness characterized by testicular enlargement and uveitis. This animal developed ataxia and died. Necropsy examination revealed bilateral enlargement of the kidneys in both horses, petechial hemorrhages of the optic nerve (Holsteiner), and a diffusely firm and enlarged left testicle (miniature horse). Microscopic evaluation of tissues revealed granulomatous nephritis, optic neuritis, retinitis, and encephalitis in both horses and orchitis in only the miniature horse with intralesional rhabditiform nematodes. Halicephalobus gingivalis was found in the urine sediment of both animals and in semen of the Holsteiner horse.

Type C botulism in turkeys: determination of the median toxic dose.

The median toxic dose (TD50) of type C botulinum in turkeys was determined using an up-and-down method for toxicologic testing. Birds were dosed intravenously with 10, 20, or 40 mouse lethal dose per kilogram body weight (MLD/kg) of type C botulism toxin and observed for 5 days. Administration of toxin resulted in acute death, posterior paresis, or no effect, depending upon the dose. The TD50 causing posterior paresis was calculated as 25.75 MLD/kg (confidence interval = 17.08-38.82 MLD/kg). Posterior paresis was identified as the principal sign associated with sublethal botulism toxicosis in turkeys. The resultant posterior paresis was similar to the clinical syndrome observed in an unsolved field investigation.

Mycoplasma bovis associated with decubital abscesses in Holstein calves.

Between April of 1990 and March of 1992, calves on a Holstein calf ranch experienced subcutaneous decubital abscesses involving the brisket region, dorsal aspect of the carpus, and lateral aspect of the stifle joints. Fifty out of 2,500 (2%) Holstein calves between the ages of 3 and 12 weeks were affected. Needle aspirates of brisket abscesses from 8 calves and 6 live or dead calves with 1 or more decubital abscesses were submitted for examination. Two of the 6 calves in addition had bronchopneumonia. Mycoplasma bovis was isolated from all abscesses and 1 lung. Formalin fixed tissues taken from the affected areas also revealed M. bovis by immunoperoxidase staining. No evidence of joint involvement was apparent, and no mycoplasma was isolated from the joints adjacent to affected areas. Attempts to isolate mycoplasma from milk and environmental samples were unsuccessful.

A fatal case of oak poisoning in a double-wattled cassowary (Casuarius casuarius).

A double-wattled cassowary died following a clinical course of severe diarrhea, anorexia, and polydypsia. At necropsy, prolapse of the penis, severe enteritis, and swelling of the kidneys with subcapsular heavy deposits of urates were noted. Histologic lesions comprised nephrosis, interstitial edemia of the muscle, and sloughing of the intestinal villi. Leaves collected from the gizzard were identified as coast live oak (Quercus agrifolia). Diagnosis of oak poisoning was made based on the renal lesions and the finding of a high content of tannins in the liver and gastrointestinal tract. Oak poisoning has not been reported previously in avian species.

The influence of crumble and mash feed on oral lesions of white leghorn laying hens.

The effect of crumble and mash feed on oral lesions in laying hens was investigated. Each of two groups of white leghorn hens (group A, n = 120; group B, n = 120) was separated into crumble- and mash-fed treatments. At the start of the trial, group A chickens were free of oral lesions, whereas group B chickens had nearly 100% prevalence of oral lesions. The trials began at 17.4 and 22 wk of age and ended at 32 and 33 wk of age for groups A and B, respectively. Chickens were housed in cages indoors, fed free choice, and serologically monitored. Oral lesions were periodically evaluated by visual scoring. Lesion prevalence peaked in group A chickens at 23-25 wk of age, concurrently with an outbreak of respiratory disease, and decreased to a low level at the end of the trial. For most of the trial, crumble-fed chickens had significantly lower oral lesion prevalence than mash-fed chickens (P < 0.05). Lesion prevalence in group B chickens decreased after treatments began and maintained this trend to the end of the trial. Compared with mash-fed chickens, crumble-fed chickens in group B had significantly lower oral lesion prevalence throughout the trial (P < 0.001). Neither group had significant differences in oral lesion scores between treatments. Most lesions were on the lower palate, pinpoint to 2 mm in diameter, often multiple, and bilaterally symmetrical. Feed analyses for mycotoxins and heavy metals were within normal limits. The inciting etiology of oral lesions was not elucidated in this trial. However, this work demonstrated that once lesions were present, feed type had a strong effect on persistence of oral lesions.

Intranuclear inclusions of unknown pathogenic significance from diagnostic cases in three avian species.

Intranuclear inclusions were observed with light microscopy in tissues from necropsy cases from three different species of birds. Because of the nature of these inclusions, the species affected, or their distribution, the inclusions were considered of unknown pathogenic significance. The inclusions were examined ultrastructurally. Parvovirus-like particles were observed in the intranuclear inclusions of pigeon hepatocytes and duodenal stromal cells from a quail. Finely granular eosinophilic intranuclear inclusion bodies from two unrelated pigeon cases were found to be composed of loosely organized filaments. One liver sample from a 16-week-old laying chicken had prominent eosinophilic hepatocellular intranuclear inclusions composed of electron-dense coarsely granular amorphous material.

Viral pathogenesis of a nephrotropic infectious bronchitis virus isolated from commercial pullets.

Infectious bronchitis was diagnosed in 3-to-4-week-old pullets from an outbreak in a commercial flock in California. The disease was characterized by head swelling, watery discharge from the eyes and nostrils, and urates in kidneys. Mortality ranged from 1.8% to 12.5% per week. The isolation of a coronavirus from a suspension of pooled kidneys from clinically ill chickens at the fifth passage in 10-day-old chicken embryos, gross and histologic renal lesions, and seroconversion by enzyme-linked immunosorbent assay in inoculated birds suggested that the virus isolated was a nephrotrophic strain of infectious bronchitis virus (IBV). The virus isolate was found to be a previously unrecognized serotype, based on virus neutralization tests performed in embryonated chicken eggs. Nephropathogenicity of the IBV isolate was confirmed by inoculation of the viral isolate into specific-pathogen-free chicks and demonstration of renal lesions. The isolation of nephrotropic strains of IBV has not been reported previously from poultry in California.

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.

Recurrent transient paresis in a turkey flock.

Recurring episodes of extreme leg weakness and associated mortality were documented in a turkey flock at 8 to 15 weeks of age. Flock mortality attributed to posterior paresis was approximately 12%, or 4800 of 40,000 turkeys. Four of six open-confinement units were affected. Gross and histological examinations revealed no significant lesions. Immunology and virology were uninformative. There were no significant differences in serum chemistry between clinically affected and normal turkeys. Testing of feed, water, soil, and tissues revealed no common toxicants. Isolation and supportive care for affected turkeys, both in the laboratory and in the field, frequently resulted in full recovery. Injection of a test group of affected turkeys with Type C botulism antitoxin appeared to enhance recovery. However, repeated attempts to detect botulism toxin in serum, liver, or cecal contents using mouse bioassay procedures were unsuccessful.

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.

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.

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.

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.