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- Author or Editor: N. James MacLachlan x
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Objective—To evaluate clinical, microbiologic, and pathologic outcomes in mice after inoculation with 4 equine-origin Corynebacterium pseudotuberculosis strains.
Animals—15 C3H/HeJ mice.
Procedures—In a preliminary study, the optimum route of inoculation was determined. In the main study, mice were allocated to 4 treatment groups (3 mice/group). One slow- or rapid-growing equine-origin C pseudotuberculosis strain was inoculated ID into the mice of each treatment group.
Results—All 4 strains had distinct tropism for the liver. Histologic lesions associated with rapid-growing strains included focally extensive unencapsulated areas of acute, massive coagulative necrosis of hepatocytes with intralesional colonies of bacteria and variable portal hepatitis characterized by accumulations of mononuclear and polymorphonuclear inflammatory cells. In contrast, the livers of mice inoculated with slow-growing strains had multiple discrete, randomly distributed foci of hepatocellular necrosis and neutrophilic hepatitis that were considerably less severe than the lesions in the mice inoculated with the rapid-growing strains. Significantly more bacterial colonies were recovered from the organs of mice inoculated with rapid-growing than with slow-growing strains of bacteria. Bacteria were isolated from the liver, spleen, lungs, and mesenteric lymph nodes of mice inoculated with rapid-growing strains and from the liver and lymph nodes of mice inoculated with slow-growing strains.
Conclusions and Clinical Relevance—Study of host-bacteria interactions in hosts that are naturally infected with C pseudotuberculosis is difficult because of underlying genetic variability among animals, expense, and requirements for multiple replicates and control animals. The C3H/HeJ mice may provide a useful means for studying virulence mechanisms of C pseudotuberculosis.
Objective—To compare replication of bluetongue virus (BTV) and epizootic hemorrhagic disease virus (EHDV) in pulmonary artery endothelial cells (ECs) obtained from juvenile cattle, sheep, white-tailed deer (WTD; Odocoileus virginianus), and black-tailed deer (BTD; O hemionus columbianus).
Sample Population—Cultures of pulmonary artery ECs obtained from 3 cattle, 3 sheep, 3 WTD, and 1 BTD.
Procedure—Purified cultures of pulmonary artery ECs were established. Replication, incidence of infection, and cytopathic effects of prototype strains of BTV serotype 17 (BTV-17) and 2 serotypes of EHDV (EHDV-1), and (EHDV-2) were compared in replicate cultures of ECs from each of the 4 ruminant species by use of virus titration and flow cytometric analysis.
Results—All 3 viruses replicated in ECs from the 4 ruminant species; however, BTV-17 replicated more rapidly than did either serotype of EHDV. Each virus replicated to a high titer in all ECs, although titers of EHDV-1 were significantly lower in sheep ECs than in ECs of other species. Furthermore, all viruses caused extensive cytopathic effects and a high incidence of cellular infection; however, incidence of cellular infection and cytopathic effects were significantly lower in EHDV-1-infected sheep ECs and EHDV-2-infected BTD ECs.
Conclusions and Clinical Relevance—There were only minor differences in replication, incidence of infection, and cytopathic effects for BTV-17, EHDV-1, or EHDV-2 in ECs of cattle, sheep, BTD, and WTD. It is not likely that differences in expression of disease in BTV- and EHDV-infected ruminants are attributable only to species-specific differences in the susceptibility of ECs to infection with the 2 orbiviruses. (Am J Vet Res 2003;64:860–865)
Objective—To compare seroprevalence of antibodies against equine arteritis virus (EAV) in horses residing in the United States with that of imported horses.
Sample Population—Serum samples from 364 horses on 44 equine operations in California and 226 horses imported from various countries.
Procedure—Serum samples were collected from each imported horse and from up to 20 horses on each operation. For resident horses, the number of sampled horses on each operation was determined on the basis of the number of horses on the operation. Samples were tested for antibodies against EAV by use of a serum neutralization test.
Results—1.9% of resident horses and 18.6% of imported horses were seropositive to EAV, including 16.1% of imported stallions.
Conclusions and Clinical Relevance—Results indicate that the EAV seroprevalence of horses residing in California is considerably lower than that of imported horses, including imported stallions. (J Am Vet Med Assoc 2001;219:946–949)
Objective—To evaluate serum feline trypsin-like immunoreactivity (fTLI) concentration and results of abdominal ultrasonography, CBC, and serum biochemical analyses for diagnosis of pancreatitis in cats.
Animals—28 cats with clinical signs compatible with pancreatitis.
Procedure—Serum fTLI concentrations were determined, and abdominal ultrasonography, CBC, and serum biochemical analyses were performed prior to histologic evaluation of pancreatic, hepatic, and intestinal specimens. On the basis of histologic results, cats were categorized as having a normal pancreas (n = 10), pancreatic fibrosis with ongoing inflammation (9), pancreatic fibrosis without inflammation (4), and acute necrotizing pancreatitis (5). Serum fTLI concentrations and results of CBC, serum biochemical analyses, and histologic evaluation of hepatic and intestinal specimens were compared among groups.
Results—Significant differences in serum fTLI concentrations or any hematologic or biochemical variable were not detected among the 4 groups of cats. Median serum fTLI concentrations were 51 µg/L (range, 18 to 200 µg/L) in cats with a normal pancreas, 32 µg/L (range, 12 to > 200 µg/L) in cats with pancreatic fibrosis and ongoing inflammation, 124 µg/L (range, 36 to > 200 µg/L) in cats with pancreatic fibrosis without ongoing inflammation, and 30 µg/L (range, 24 to 84 µg/L) in cats with acute necrotizing pancreatitis. We detected a high prevalence of concurrent hepatic and intestinal tract disease in cats with pancreatitis.
Conclusion and Clinical Relevance—In cats with clinical signs of pancreatitis, serum fTLI concentration is poorly associated with histopathologic diagnosis. (J Am Vet Med Assoc 2000;217:37–42)
Objective—To compare growth characteristics of strains of equine arteritis virus (EAV) of differing virulence to horses in rabbit kidney (RK)-13 cells and equine endothelial cells (EECs) cultured from the pulmonary artery of a foal.
Sample Population—13 strains of EAV, including 11 field isolates of differing virulence to horses; the highly virulent, horse-adapted Bucyrus strain; and the modified-live virus (MLV) vaccine derived from it.
Procedure—The growth characteristics of the 13 strains were compared in EECs and RK-13 cells. Viral nucleoprotein expression, cytopathogenicity, and plaque size were compared to determine whether growth characteristics of the 13 strains were predictive of their virulence to horses.
Results—Cytopathogenicity, viral nucleoprotein expression, and plaque size induced by all 13 viruses were similar in RK-13 cells, whereas virulent strains of EAV caused significantly larger plaques in EECs than did the avirulent strains of EAV. Paradoxically, the highly attenuated MLV vaccine and 1 field isolate of EAV caused plaques in EECs that were larger than those caused by any of the other viruses, and sequence analysis confirmed the field isolate of EAV to be indistinguishable from the MLV vaccine.
Conclusions and Clinical Relevance—With the notable exception of the MLV vaccine, growth of the various strains of EAV in EECs was predictive of their individual virulence to horses. Thus, EECs provide a relevant and useful model to further characterize determinants of virulence and attenuation amongst strains of EAV. (Am J Vet Res 2003;64:779–784)