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Objective: To characterize the impact of Mannheimia haemolytica infection on feed intake and weight gain in feedlot heifers and to evaluate the clinical efficacy of isoflupredone acetate administered in combination with oxytetracycline., Animals: 96 weanling heifers in a research feedlot facility., Procedures: Bronchopneumonia was induced by intrabronchial infusion of M haemolytica. Control heifers underwent a sham procedure. Infected heifers were treated with oxytetracycline alone or in combination with isoflupredone acetate (OXY-ISO) or with nothing. Clinical variables were recorded daily for 7 days following disease induction, and feedlot performance indices were measured over a 12-week period., Results: Infection caused a reduction in dry-matter intake and average daily gain (ADG) in heifers that received no treatment. Oxytetracycline treatment alone did not prevent reductions in feed intake and ADG during the first week after infection was induced, whereas OXY-ISO treatment did prevent these reductions. Treatment with OXY-ISO also resulted in faster clinical improvement. No significant differences were evident between the oxytetracycline and OXY-ISO groups with respect to dry-matter intake or ADG throughout the study period., Conclusions and Clinical Relevance: Isoflupredone acetate appeared to be a useful clinical adjunct to treatment with oxytetracycline in cattle with acute M haemolytica bronchopneumonia.

Objective: To investigate the effect of opsonization of Rhodococcus equi with R. equi-specific antibodies in plasma on bacterial viability and phagocyte activation in a cell culture model of infection., Sample: Neutrophils and monocyte-derived macrophages from 6 healthy 1-week-old foals and 1 adult horse., Procedures: Foal and adult horse phagocytes were incubated with either opsonized or nonopsonized bacteria. Opsonization was achieved by use of plasma containing high or low concentrations of R. equi-specific antibodies. Phagocyte oxidative burst activity was measured by use of flow cytometry, and macrophage tumor necrosis factor (TNF)-α production was measured via an ELISA. Extracellular and intracellular bacterial viability was measured with a novel R. equi-luciferase construct that used a luminometer., Results: Opsonized bacteria increased oxidative burst activity in adult horse phagocytes, and neutrophil activity was dependent on the concentration of specific antibody. Secretion of TNF-α was higher in macrophages infected with opsonized bacteria. Opsonization had no significant effect on bacterial viability in macrophages; however, extracellular bacterial viability was decreased in broth containing plasma with R. equi-specific antibodies, compared with viability in broth alone., Conclusions and Clinical Relevance: The use of plasma enriched with specific antibodies for the opsonization of R. equi increased the activation of phagocytes and decreased bacterial viability in the extracellular space. Although opsonized R. equi increased TNF-α secretion and oxidative burst in macrophages, additional factors may be necessary for effective intracellular bacterial killing. These data have suggested a possible role of plasma antibody in protection of foals from R. equi pneumonia.

Objective: To validate a radioimmunoassay for measurement of procollagen type III amino terminal propeptide (PIIINP) concentrations in canine serum and bronchoalveolar lavage fluid (BALF) and investigate the effects of physiologic and pathologic conditions on PIIINP concentrations., Sample Population: Sera from healthy adult (n = 70) and growing dogs (20) and dogs with chronic renal failure (CRF; 10), cardiomyopathy (CMP; 12), or degenerative valve disease (DVD; 26); and sera and BALF from dogs with chronic bronchopneumopathy (CBP; 15) and healthy control dogs (10 growing and 9 adult dogs)., Procedure: A radioimmunoassay was validated, and a reference range for serum PIIINP (S-PIIINP) concentration was established. Effects of growth, age, sex, weight, CRF, and heart failure on S-PIIINP concentration were analyzed. In CBP-affected dogs, S-PIIINP and BALF-PIIINP concentrations were evaluated., Results: The radioimmunoassay had good sensitivity, linearity, precision, and reproducibility and reasonable accuracy for measurement of S-PIIINP and BALF-PIIINP concentrations. The S-PIIINP concentration reference range in adult dogs was 8.86 to 11.48 mug/L. Serum PIIINP concentration correlated with weight and age. Growing dogs had significantly higher S-PIIINP concentrations than adults, but concentrations in CRF-, CMP-, DVD-, or CBP-affected dogs were not significantly different from control values. Mean BALF-PIIINP concentration was significantly higher in CBP-affected dogs than in healthy adults., Conclusions and Clinical Relevance: In dogs, renal or cardiac disease or CBP did not significantly affect S-PIIINP concentration; dogs with CBP had high BALF-PIIINP concentrations. Data suggest that the use of PIIINP as a marker of pathologic fibrosis might be limited in growing dogs.

Objective: To evaluate viral and bacterial respiratory pathogens and Mycoplasma spp isolated from lung tissues of cattle with acute interstitial pneumonia (AIP) and cattle that had died as a result of other causes., Sample Population: 186 samples of lung tissues collected from cattle housed in 14 feedlots in the western United States., Procedure: Lung tissues were collected during routine postmortem examination and submitted for histologic, microbiologic, and toxicologic examinations. Histologic diagnoses were categorized for AIP, bronchopneumonia (BP), control samples (no evidence of disease), and other disorders., Results: Cattle affected with AIP had been in feedlots for a mean of 1272 days before death, which was longer than cattle with BP and control cattle. Detection of a viral respiratory pathogen (eg, bovine respiratory syncytial virus [BRSV], bovine viral diarrhea virus, bovine herpesvirus 1, or parainfluenza virus 3) was not associated with histologic category of lung tissues. Bovine respiratory syncytial virus was detected in 8.3% of AIP samples and 24.0% of control samples. Histologic category was associated with isolation of an aerobic bacterial agent and Mycoplasma spp. Cattle with BP were at greatest risk for isolation of an aerobic bacterial agent and Mycoplasma spp., Conclusions and Clinical Relevance: Analysis of these results suggests that AIP in feedlot cattle is not a consequence of infection with BRSV. The increased, risk of isolation of an aerobic bacterial agent from cattle with AIP, compared with control cattle, may indicate a causal role or an opportunistic infection that follows development of AIP.

Objective: To compare concentrations of 3-methyleneindolenine (3MEIN) in lung tissues obtained from feedlot cattle that died as a result of acute interstitial pneumonia (AIP) and cattle that died as a result of other causes and to compare blood concentrations of 3MEIN in healthy feedlot cattle and feedlot cattle with AIP., Study Population: Blood samples and lung tissues collected from 186 cattle housed in 14 feedlots in the western United States., Procedure: Samples of lung tissues were collected during routine postmortem examination and submitted for histologic, microbiologic, and toxicologic examination. Blood samples were collected from cattle with clinical manifestations of AIP and healthy penmates. Histologic diagnoses were categorized as AIP, bronchopneumonia (BP), control samples, and other disorders. Concentrations of 3MEIN were determined in lung tissues and blood samples, using an ELISA., Results: Concentrations of 3MEIN in lung tissues were significantly greater in AIP and BP samples, compared with control samples. Absorbance per microgram of protein did not differ between BP and AIP samples. Blood concentrations of 3MEIN were significantly greater in cattle with AIP, compared with healthy cattle or cattle with BP. Odds of an animal with AIP being a heifer was 3.1 times greater than the odds of that animal being a steer., Conclusions and Clinical Relevance: Increased pulmonary production of 3MEIN may be an important etiologic factor in feedlot-associated AIP.

Mycoplasma arginini was isolated from the pharynges and tonsils of 4 of 6 swine necropsied during an epizootic of respiratory tract diseases and lameness. The organism was also isolated from 2 of 16 asymptomatic swine examined in the same herd approximately 10 months after the epizootic. In addition, M arginini, Acholeplasma laidlawii, and other acholeplasmas were isolated from recycled effluent of an anaerobic lagoon used for disposal of waste from the swine herd. This observation represents the 1st report of a Mycoplasma species isolated from a lagoon or sewage system. The pathogenicity of a strain of M arginini isolated during the epizootic was examined by inoculating young swine intranasally, intratracheally, intravenously, and intraperitoneally. The agent colonized in the pharynges of 2 pigs inoculated intranasally, but did not produce overt signs of clinical disease. Although neutralizing antibodies to M arginini were not detected, 1 animal that had been infected naturally and 2 that had been inoculated intravenously did develop complement-fixing antibodies. The findings indicate that M arginini can colonize in the nasal and pharyngeal mucosae of swine, but that it is not highly pathogenic for these animals.

To evaluate the relationship between pneumonic lesions and distribution of bacteria, lungs from calves inoculated with Pasteurella multocida were examined histologically by use of immunoperoxidase technique. Pneumonic lesions fundamentally consisted of broncho-pneumonia with fibrinopurulent pleuritis. The lesions were confirmed to be associated with inoculated P multocida, using the immunoperoxidase technique. The P multocida antigen was detected not only in the bacterial clusters in the lesions, but also in the cytoplasm of infiltrating neutrophils and macrophages. Further, immunoelectron microscopy indicated that the inoculated bacteria generally were phagocytosed and digested by neutrophils.

Fourteen 6-month-old calves were infected with Pasteurella haemolytica or infectious bovine rhinotracheitis (IBR) virus. Four calves were inoculated sequentially with IBR virus followed by P haemolytica at a 5-day interval. Calves were inoculated by allowing them to inhale an aerosol of the organism or by placing an inoculum in the right lung, using fiberoptic bronchoscopy. Clinical signs of infection were recorded, and the calves, if they survived, were killed and necropsied 3 days after inoculation with P haemolytica (or 8 days after inoculation with IBR virus). The extent of pulmonary lesions was determined, and the lower respiratory tract (lungs and lower trachea) was examined for both organisms. Inoculation of the calves by aerosolization with IBR virus alone resulted in mild respiratory tract disease. Mild-to-moderately severe respiratory tract disease developed as a result of sequential inoculations by aerosolization with IBR virus and P haemolytica. However, respiratory tract disease did not develop in calves exposed by aerosol to P haemolytica alone. Large numbers of these organisms were recovered from the lower respiratory tract of the dually inoculated calves, only indicating delayed pulmonary clearance. Mild clinical signs of disease but substantial, though localized, pneumonic lesions developed in calves inoculated with P haemolytica by fiberoptic bronchoscopy. Calves inoculated with IBR virus by the latter procedure developed moderately severe respiratory tract disease involving 25% to 30% of the total lung volume. Lesions occurred mainly in the right lung, but the left lung also had marked lesions in these calves.(ABSTRACT TRUNCATED AT 250 WORDS)

The pneumopathogenicity in calves of 2 strains of bovine viral diarrhea (BVD) virus, isolate 2724 (a noncytopathogenic virus) and isolate 72 (a cytopathogenic virus), was compared. All calves were inoculated endobronchially, using fiberoptic bronchoscopy. Two calves were given Pasteurella haemolytica, 2 calves were given the noncytopathogenic BVD virus, and 2 calves were given cytopathogenic BVD virus. Five calves were inoculated sequentially with BVD virus and, 5 days later, with P haemolytica. Two of these calves were inoculated with the noncytopathogenic BVD virus and the other 3 with the cytopathogenic strain. Both BVD virus strains caused marked respiratory tract disease in the calves sequentially inoculated with P haemolytica and also impaired pulmonary clearance of P haemolytica. However, the effect of the cytopathogenic strain was more severe than the noncytopathogenic strain, indicating that strains of BVD virus may vary in their pneumopathogenicity for calves.

Lung infections of specific-pathogen-free rats were studied to determine cross-immunity between infections with Pasteurella pneumotropica and Angiostrongylus cantonensis. Rats were found to have differences in mortality due to pneumonic infections with P pneumotropica and A cantonensis and to coinfections of P pneumotropica and A cantonensis. Single infections of P pneumotropica were not dosage-dependent in their lethality for specific-pathogen-free rats. The mortality of coinfection with P pneumotropica and A cantonensis was significantly lower than that of a monoinfection with P pneumotropica, demonstrating a cross-protective phenomenon.