Experimental Salmonella typhi infection in the domestic pig, Sus scrofa domestica.

The domestic pig, Sus scrofa domestica, was examined as a model for typhoid fever, a severe and systemic disease of humans caused by Salmonella typhi. Six pigs were inoculated 1 week post-weaning with approximately 10(10)colony forming units (cfu) of wild type Salmonella typhi strain ISP1820 intranasally and observed for 3 weeks. S. typhi was cultured from the tonsils of 50% of the pigs at necropsy. Cultures from all other organs analysed (ileum, colon, spleen and liver) were negative. No clinical or histopathological signs of disease were observed. Pigs inoculated in parallel with swine-virulent S. choleraesuis all exhibited signs of systemic salmonellosis indicating that the parameters of the experimental infection with S. typhi (e.g. route) were appropriate. Whereas the pig has a gastrointestinal tract that is very similar to humans, our results indicated that the unique features of host and microbe interaction needed to produce typhoid fever were not mimicked in swine. Nevertheless, our observation of tonsillar involvement was consistent with former observations of S. choleraesuis and S. typhimurium infections in swine and supports a role for the tonsil in all porcine salmonella infections.

Shigella infection as observed in the experimentally inoculated domestic pig, Sus scrofa domestica.

The domestic pig, Sus scrofa domestica, was investigated as a potential animal model for shigellosis. We examined the effects of pig age, pig breed and antibiotic pretreatment upon Shigella infection. Shigella dysenteriae, and Shigella flexneri (both virulent and avirulent strains) were utilized. Our results indicated that young (4-week-old), conventionally re ared, domestic pigs were routinely, but briefly, colonized (average=3.5+/-2.5 days) following oral or gavage administration ofS. flexneri, as determined by direct rectal cultures. The duration of S. dysenteriae colonization was significantly shorter. Inoculation of younger (2 days) or older (9 weeks) pigs with S. flexneri had no significant effect on infection duration. Similarly, infection of 4-week-old pigs with virulent and avirulent strains of S. flexneri had no effect upon the duration of infection, nor did the use of a swine-passaged S. flexneri isolate. Marked clinical, histopathological (gross and microscopic) and immunoIhistopathological signs of disease were absent in all infections. However, in instances where microscopic histopathological evidence was used to correctly identify infected pigs, tonsillar lesions were the consistently noted criteria. The tonsils are believed to be an important portal of entry for Salmonella choleraesuis, another member of the Enterobacteriaceae and a prevalent pig pathogen. Taken altogether, our results indicate that the domestic pig is unsuitable as a model for shigellosis.

Canine laryngeal rhabdomyoma.

Three canine laryngeal tumors were diagnosed as oncocytomas by light microscopy, but were determined to be rhabdomyomas following ultrastructural and immunocytochemical examination. Tumors consisted of large eosinophilic cells interspersed with smaller dark cells. Large tumor cells had a granular, intensely eosinophilic cytoplasm. Scattered through the tumors were a few elongated cells with cytoplasmic cross striations and multiple nuclei. Tumor cells from all three dogs contained numerous mitochondria and bundles of myofibrils with electron-dense Z-lines typical of striated muscle cells. Intracellular myoglobin and desmin were detected in the tumors by immunocytochemistry. Comparisons are made with a previous report of canine laryngeal oncocytomas.

Pathogenesis of change in the upper respiratory tracts of turkeys experimentally infected with an Alcaligenes faecalis isolate.

The course of changes within the upper respiratory tracts of turkey poults experimentally infected with Alcaligenes faecalis was studied. The initial change observed (5 days post-inoculation) was colonization of the upper respiratory tract by the bacterium. Changes in the nasal turbinates and trachea were first apparent as a focal loss of cilia but subsequently developed into a general loss of cilia (11 days post-inoculation). Eventually, the entire ciliated epithelial layer in the cranial region of the trachea was lost (13 days post-inoculation). With the loss of cilia and ciliated cells, a highly viscous mucus was able to accumulate in the anterior one-half to two-thirds of the trachea. In addition, changes in the gross structure of the trachea (flaccid trachea) were observed in all poults inoculated with A. faecalis. There was an apparent gradation in the severity of these changes from severe in the cranial region of the trachea to mild in the region just anterior to the bronchial bifurcation. The observations resulting from A. faecalis infection indicated two major tracheal changes responsible for the chronic and sometimes severe nature of this disease. These changes included a loss of ciliary activity and a flaccid trachea which together resulted in the accumulation and stasis of mucus and tracheal collapse.

Cytotoxic activity of pathogenic Alcaligenes faecalis in turkey tracheal organ cultures.

Turkey tracheal organ cultures were used to study the virulence of Alcaligenes faecalis isolants that have been shown to be pathogenic for turkey poults. Viable infected and noninfected tracheal rings were examined by phase-contrast microscopy, and fixed stained sections were examined by light microscopy. Alcaligenes faecalis at concentrations of 10(8) and 10(9) colony-forming units/ml caused ciliostasis, hydropic degeneration (characterized by blebbing of the plasma membrane, cellular swelling, and cytoplasmic vacuolation), and eventual sloughing of the ciliated epithelium. Only ciliated epithelial cells appeared affected. For comparison, other bacterial isolants not pathogenic for turkeys were tried in this system. These bacterial isolants included 3 isolants of A faecalis from human beings and isolants of Klebsiella pneumoniae, Escherichia coli, and A faecalis from turkeys. Inoculation of each of these bacterial cultures onto tracheal organ cultures failed to produce the lesions described.

Turkey respiratory tract adenoviruses: oncogenic potential in neonatal hamsters (Mesocricetus auratus).

The tumorigenic properties of 3 turkey adenoviruses (CUA, NC-K, and MST) isolated from turkeys with respiratory tract disease and injected into neonatal hamsters (Mesocricetus auratus) have been determined. One of 30 adenovirus isolates (CUA) induced tumors at the site of inoculation (subcutaneously or intracranially) in neonatal hamsters. The tumors were identified as fibrosarcomas and undifferentiated sarcomas. The tumors were found to be free of infective virus, but hamsters which had tumors produced antibody to the virus-specific tumor antigen detectable by the complement-fixation test. The antibody titers for the tumor antigen were from 1:8 to 1:16. Abnormalities were not observed in the major organs collected from hamsters inoculated with the virus. Inoculations of hamster embryo cells and of adult and baby hamster kidney cells with the 3 turkey adenoviruses at a high multiplicity of infection did not produce transformed cells in monolayers. Hamster cells were permissive for CUA virus, since cytopathic effect was observed in 3 to 5 days after inoculation.

Isolation of an etiologic agent of acute respiratory disease (rhinotracheitis) of turkey poults.

A small gram-negative motile bacillus was isolated from laboratory poults affected by acute respiratory disease (rhinotracheitis) of turkeys. The bacterium was inoculated intranasally into susceptible day-old poults; the poults developed typical clinical signs of acute respiratory disease, and the bacterium was reisolated. This same bacterium was isolated from commercial poults with typical signs of acute respiratory disease but not from poults of similar age which were clinically normal. The bacterium has not been identified taxonomically. We conclude that it is a primary etiologic agent for acute respiratory disease of turkey poults.

Histopathology of a rhinotracheitis of turkey poults associated with adenoviruses.

Tissues from turkey poults with adenovirus-associated respiratory disease were examined for microscopic lesions. Histopathologic changes observed in tissue from poults submitted with clinical signs of severe respiratory disease ranged from an acute mucoid rhinotracheitis through a fibrinonecrotic tracheitis to a chronic polypoid tracheitis with squamous metaplasia of the tracheal epithelium. Clinically normal poults housed with poults that subsequently developed clinical signs of the disease rarely had basophilic intranuclear inclusions within the epithelial cells of nasal turbinates.

Physicochemical characterization and pathogenicity studies of two turkey adenovirus isolants.

Two turkey adenoviruses were isolated from poults with respiratory disease, and their physicochemical properties were studied. The virus particles were unenveloped. contained DNA genome, replicated within the nuclei of infected cells, and were icosahedral in shape. Pathogenicity studies in poults indicated that North Carolina Kennedy isolant was a pathogen of relatively low virulence whereas the North Carolina Jackson isolant was nonpathogenic in commercial turkey poults.

Sequential sterile autolysis in the ovine fetus: macroscopic changes.

Sterile intrauterine autolysis was experimentally produced in 28 ovine fetuses in the last 3rd of gestation by umbilical artery ligation. The fetuses were retrieved by cesarean section after periods of sterile intrauterine autolysis ranging from 0.5 to 168 hours. The following autolytic changes, frequently reported as significant lesions in infectious abortions in cattle and sheep, were observed: subcutaneous blood-tinged gelatinous edema, blood-tinged fluid in the serous cavities, renal cortical softening, uniform reddish brown tissues, hepatic friability and mottling, and cloudy yellow to cloudy red abomasal contents. The appearance of these and other autolytic changes corresponded to sterile sequential autolytic changes reported in the rabbit fetus and used to determine duration of retention of stillborn infants and are of comparative biomedical significance. The sequential autolytic changes may be used as an index to duration of retention after death of a ruminant fetus and provide a basis for reappraising various infective abortifacients common to ruminants by allowing separation of specific lesions from strictly autolytic changes.