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T R Ames

Publications and source records attributed to T R Ames.

53 records · Page 3Linked to original sources
PubMed1986

Study on the etiologic role of bovine respiratory syncytial virus in pneumonia of dairy calves.

Bovine respiratory syncytial virus (BRSV) was the viral agent most commonly identified in 14 epizootics of pneumonia in dairy calves. A microtiter serum-virus neutralization test proved to be the best means of identifying involvement of BRSV; seroconversion (fourfold or greater rise in titer) was demonstrated in 10 of the 14 epizootics. Only limited involvement of bovine viral diarrhea virus, infectious bovine rhinotracheitis virus, parainfluenza 3 virus, and bovine adenovirus type 3 was recognized. Pasteurella multocida was isolated in 12 of 14 epizootics, and Pasteurella haemolytica in 4 of 14 epizootics. Mycoplasmal and ureaplasmal agents were isolated in all 14 epizootics.

Animals↗
PubMed1986

Vertebral body abscesses in cattle: a review of five cases.

Over a 4-year period, vertebral body abscess (VBA) was diagnosed in 5 young cattle at the University of Minnesota, College of Veterinary Medicine. Review of these cases indicated that laboratory findings may not support a diagnosis of VBA and that the most important basis for diagnosis of this condition is a thorough neurologic examination. In 4 cases, necropsy revealed abscesses in the lungs or thoracic cavity as well, suggesting that a history of pneumonia preceding paresis may favor the diagnosis of VBA.

Abscess↗
PubMed1986

Seroepizootiologic study of bovine respiratory syncytial virus in a dairy herd.

A 16-month seroepizootiologic study of bovine respiratory syncytial virus (BRSV) infection was conducted in a dairy herd. Results indicated that antibodies to BRSV present in serum from newborn calves were derived through the ingestion of colostrum. This passive immunity in calves became undetectable in an average of 99 days (SD = 36.5; range = 30 to 208 days). Two epizootics of respiratory tract disease occurred during the study period, and an association with BRSV was demonstrated in both epizootics. In the 2 epizootics, clinical signs of respiratory tract disease were only mildly to moderately severe, with no mortality or evidence of chronic pneumonia occurring. Seemingly, the passive immunity failed to protect calves from infection and disease caused by BRSV. Additionally, it was observed that if active immunity was induced by infection with BRSV, this immunity protected from the development of clinical disease, but not from reinfection upon subsequent exposures to BRSV.

Animals↗
PubMed1986

Seroepizootiologic study of bovine respiratory syncytial virus in a beef herd.

A seroepizootiologic study of bovine respiratory syncytial virus in a beef herd was conducted from February 1983 through March 1984. During the study period, 3 separate respiratory tract disease epizootics were recognized in calves after they had been split into 3 groups. Bovine respiratory syncytial virus infection was diagnosed in each epizootic on the basis of serologic evidence, postmortem findings, and immunofluorescent examination of lung tissue. Additionally, there was serologic evidence for involvement of bovine adenovirus type 3 in the epizootics in 2 of the groups of calves, but not in the 3rd. In 2 groups of calves, respiratory tract disease occurred in 2 stages, with the 1st stage being mild followed by apparent recovery. The 2nd stage, which was associated with a change to colder weather, was clinically more severe, with death loss occurring.

Animals↗
PubMed1985

Effect of maternal antibody upon vaccination with infectious bovine rhinotracheitis and bovine virus diarrhea vaccines.

This report presents the normal rate of decay of maternal antibody and the influence of maternal antibody on responses to a single vaccination with modified-live bovine virus diarrhea and infectious bovine rhinotracheitis virus vaccines at 196 days of age and on response to vaccinations with the same vaccines given twice at 84 and 196 days of age. Passive immunity decreased to near zero over the first six months of life for both bovine virus diarrhea and infectious bovine rhinotracheitis controls. All calves seroconverted to bovine virus diarrhea vaccine at 84 days of age, even though high levels (greater than 1:32) of maternal antibodies were present. These calves did not seroconvert to infectious bovine rhinotracheitis vaccine at 84 days of age when high levels (less than 1:16) of maternal antibodies were present. Calves responded well to bovine virus diarrhea and infectious bovine rhinotracheitis vaccines given only once at 196 days of age after passive immunity disappeared. Calves which were revaccinated with infectious bovine rhinotracheitis seroconverted showing a more rapid response than the single vaccinates. Those revaccinated with bovine virus diarrhea showed an immediate response of small magnitude.

Animals↗
PubMed1985

Pulmonary response to intratracheal challenge with Pasteurella haemolytica and Pasteurella multocida.

Calves were inoculated intratracheally with 5 X 10(7), 5 X 10(8), or 5 X 10(9) colony forming units of either 18-hour stationary phase cultures or 4-hour log phase cultures of Pasteurella haemolytica. The log phase culture at all concentrations produced more severe clinical signs, hematological changes and pulmonary lesions at postmortem examination than did the corresponding stationary phase culture. More severe effects were seen with the larger doses especially with the log phase culture. Fibrinous bronchopneumonia with focal or multifocal necrosis was consistently produced by both the stationary and log phase cultures. To determine if this lesion was peculiar to P. haemolytica or whether it could be produced generally by rapidly growing Gram negative organisms, a 4-hour log phase culture of Pasteurella multocida was prepared in an identical manner to that used for the culture of P. haemolytica and given to calves intratracheally at the high bacterial dose (5 X 10(9]. The P. haemolytica produced more severe clinical, hematological and morphological changes than did the P. multocida. The lesions observed with P. multocida differed morphologically from those of P. haemolytica; there was a suppurative exudative component and minimal to no necrosis with P. multocida. It appears that an important pathogenic principle is produced by the rapidly growing P. haemolytica that causes it to produce a more severe clinical disease and more necrotizing pulmonary lesions than P. multocida.

Animals↗
PubMed1985

Oxytetracycline concentrations in plasma and lung of healthy and pneumonic calves, using two oxytetracycline preparations.

Drug concentrations in lung tissue and plasma pharmacokinetics of a long-acting preparation of oxytetracycline were compared with those of a standard preparation of oxytetracycline given to healthy and pneumonic calves. Both preparations achieved higher concentrations in the pneumonic lung when compared with those in the normal-appearing lung of the same group. A difference in concentrations in lung tissue was not found between preparations at either 24 or 48 hours. The plasma pharmacokinetic values did differ between preparations. Comparatively, the long-acting oxytetracycline had a smaller rate constant for disposition, a larger volume of distribution divided by bioavailability constant, and a longer half-life. A difference in pharmacokinetic values was not observed between healthy and pneumonic calves.

Animals↗
PubMed1985

Serologic studies of bovine respiratory syncytial virus in Minnesota cattle.

Serum antibody titers to bovine respiratory syncytial virus were determined for 559 cattle. Serum samples were obtained through the Minnesota State-Federal Brucellosis Laboratory and were collected over a 1-year period. Results of this study revealed an antibody prevalence of 65.5% to bovine respiratory syncytial virus. The distribution of antibody titers is presented, as well as analysis of titers based on breed, sex, and age of the cattle.

Animals↗
PubMed1984

Mastocytoma in a cow: a case report.

Mastocytoma was diagnosed in a four year old Holstein cow. The enlarging mass was clinically determined to be metastatic to the right superficial cervical lymph node. Cytological examination of both sites revealed mast cell neoplasia. Histopathological examination confirmed the presence of this tumor in these same sites as well as in liver, kidney and adrenal. Ultrastructurally, the mass contained round cells with electron dense granules in the cytoplasm.

Animals↗
PubMed1983

Oxytetracycline concentrations in healthy and diseased calves.

Pneumonia was induced in a group of calves that were then treated with oxytetracycline (OTC). When the plasma pharmacokinetics and tissue concentrations of this group were compared with those of healthy controls, obvious differences were observed. The volume of distribution and the half-life of OTC were increased in the group with pneumonia. Tissue concentrations of OTC (1.48 +/- 0.29 microgram/ml) were greater in the lungs of calves with pneumonia than that in the lungs (1.09 +/- 0.09 microgram/ml) of healthy controls. For the dose of OTC used, the correlation between serum concentration and tissue concentrations at 24 hours was poor. Seemingly, current concepts of antibiotic dosages and dosage intervals may be inadequate because they are based on blood and tissue values of healthy animals.

Animals↗
PubMed1982

Border disease in a flock of Minnesota sheep.

A flock problem affecting newborn lambs on a Minnesota farm was investigated. The lambs had hairy fleece and rhythmic tremors, and were unthrifty. Histologic examination revealed hypomyelinization of the CNS and hypertrophy of primary follicles in the skin. A virus antigenically related to bovine viral diarrhea virus was isolated. Serum neutralization showed that a large number of flock ewes had much higher titers to bovine viral diarrhea virus than did control animals.

Animals↗
PubMedDate not supplied

Pasteurella haemolytica A1 and bovine respiratory disease: pathogenesis.

The severe fibrinonecrotic pneumonia associated with pneumonic pasteurellosis usually results from colonization of the lower respiratory tract by Pasteurella haemolytica biotype A, serotype 1(A1). Despite recent research efforts, the authors lack a detailed understanding of the interactions and host response to P. haemolytica in the respiratory tract. The authors hypothesize that management and environmental stress factors or viral infection alters the upper respiratory tract (URT) epithelium allowing P. haemolytica to colonize the epithelium. Once the URT is colonized, large numbers of organisms enter the lung where they interact with alveolar macrophages. Endotoxin, released from the bacteria, crosses the alveolar wall where it activates pulmonary intravascular macrophages, endothelium, neutrophils, lymphocytes, platelets, complement, and Hageman factor leading to complex interactions of cells and mediators. It is the progression of this inflammatory response with neutrophil influx that is ultimately responsible for the pulmonary injury. Leukotoxin is a major virulence factor of P. haemolytica that allows it to survive by destroying phagocytic cells. At subcytolytic concentrations it may also enhance the inflammatory response by activating cells to produce mediators and release reactive oxygen metabolites and proteases.

Animals↗
PubMedDate not supplied

Ehrlichia equi infection of horses from Minnesota and Wisconsin: detection of seroconversion and acute disease investigation.

Equine granulocytic ehrlichiosis (EGE) is caused by infection with Ehrlichia equi. EGE has been reported primarily in northern California, where E equi is transmitted by the tick Ixodes pacificus. Reports of EGE and the emergence of human granulocytic ehrlichia in Minnesota prompted a seroprevalence study of E equi in horses of Minnesota and Wisconsin. Tick (Ixodes scapularis) endemic areas of Minnesota and Wisconsin were compared to nonendemic regions of Minnesota. Indirect fluorescent antibody was used to detect the presence of serum antibodies to E equi. Serum samples from healthy horses, 375 samples from I scapularis endemic counties, and 366 samples from nonendemic counties were screened at a 1:40 dilution. Results demonstrated a seroprevalence of 17.6% in endemic areas versus 3.8% in nonendemic areas. Ehrlichial DNA from 2 samples was successfully amplified by polymerase chain reaction and 919 base pairs were sequenced. The DNA sequence of 1 Minnesota/Wisconsin strain differed from the GenBank strain (M73223) of E equi at positions 84 and 886 and from the MRK strain of E equi at position 84, and was identical to the human granulocytic ehrlichiosis (HGE) agent. The 2nd Minnesota/Wisconsin strain was identical to the 1st with the exception of a substitution of "A" at position 453 that is not present in E phagocytophila, E equi, or HGE agent strain sequences. Based on the results of this study, we concluded that E equi is present and causes infection in horses in Minnesota and Wisconsin. The occurrence of infection is higher in tick endemic regions.

Acute Disease↗