Characterisation of Mannheimia spp. strains isolated from bovine nasal exudate and factors associated to isolates, in dairy farms in the Central Valley of Mexico.

Mannheimia spp. strains obtained from bovine nasal exudates of either clinically healthy or clinically affected by respiratory tract disease animals were isolated and characterised to estimate the prevalence of isolated serotypes in dairy farms in Mexico, by means of a trans-sectional descriptive study. Strains were isolated and typified through biochemical and immunological tests. chi(2) or Fisher statistical tests were applied, as well as odds ratio calculation and logistic regression analysis to evaluate the association and effect of some variables on Mannheimia spp. isolation. The apparent prevalence rates of Mannheimia haemolytica was significantly higher in diseased bovines (OR = 1.94; p < 0.05), as well as in bovines younger than 1 year of age (OR = 23.98; p < 0.05), and in bovines not vaccinated against bovine pasteurellosis (OR = 1.52; p < 0.05). Age was the variable that remained in the logistic regression model. Serotype A1 showed the highest prevalence, even when most isolates were not-typable. Bovines younger than one year of age and those with disease were the groups with the highest frequency of M. haemolytica and Mannheimia glucosida isolates.

Immunohistochemical detection of antigens of distemper, adenovirus and parainfluenza viruses in domestic dogs with pneumonia.

The lungs of 35 dogs that died in Mexico from acute or subacute pneumonia were examined immunohistochemically for canine distemper virus (CDV), canine adenovirus (CAV) and canine parainfluenza virus (CpiV), to determine their frequency and occurrence and possible associations. CDV was identified in 27 (77%) cases, CAV in 20 (57%) and CpiV in 18 (51%). The most frequent dual association was that between CDV and CpiV (five cases; 14%). All three viruses, however, were identified in the same lung in 10 cases. Immunolabelling occurred in alveolar macrophages, monocytes, pneumocytes, epithelial cells and syncytial cells. It was concluded that immunohistochemistry is a useful diagnostic tool in canine respiratory disease to complement histopathological examination.

Seroprevalence study of bovine neosporosis in Mexico.

An indirect enzyme-linked immunosorbent assay was used to obtain epidemiologic information on bovine neosporosis in dairy herds of the Mexican central plateau. Sera were collected from 1,003 cows from 50 dairy herds. Forty-three herds (group A) had been experiencing a high abortion rate. The abortion rates for the remaining 7 herds (group B) were within normal limits for Mexico. Five-hundred sixty-one (56%) of the 1,003 sera were positive. The seroprevalence of Neospora caninum antibodies was 72% (95% CI = 68-75%) in group A and 36% (95% CI = 31-40%) in group B. These results clearly show that infection with N. caninum is widespread in Mexican dairy herds, as indicated by seropositive cows in group A and group B herds at the time of the sample collection.

Neosporosis in Mexican dairy herds: lesions and immunohistochemical detection of Neospora caninum in fetuses.

Of 211 aborted bovine fetuses collected from Mexican dairy herds between January 1996 and March 1999, 73 showed microscopical lesions consistent with neosporosis. Of these 73 fetuses, 58 (79%) showed lymphocytic myocarditis, 39 (53%) showed microgliosis and multifocal necrosis in the brain, 39 (53%) showed lymphocytic hepatitis, and 19 (26%) showed lymphocytic myositis. Immunohistochemical examination of brain, myocardium and liver from 53 of the same 73 fetuses demonstrated Neospora caninum antigens in 41 (77%), of which 19 (46%) gave positive results in one of the three sites, 15 (37%) in two, and seven (17%) in three. The results indicated the presence of neosporosis in a number of the main dairy farming regions of Mexico.

[Mechanisms of pathogenicity and adhesion in Pasteurella haemolytica]. / Mecanismos de patogenicidad y adherencia de Pasteurella haemolytica.

Pasteurella haemolytica is one of the bacteria most commonly isolated from pneumonic cases in ruminants. Some of the mechanisms and factors involved in the pathogenesis of the disease are partially documented; and the early stages of bacterial colonization have not been totally clarified. Therefore a review is presented in this paper, particularly related with the mechanisms of bacterial pathogenicity responsible of pulmonary damage to ruminants, as well as a detailed analysis of the adherence process.

Serotypes of Pasteurella multocida and Pasteurella haemolytica isolated from pneumonic lesions in cattle and sheep from México.

A total of 13,000 pairs of lungs were examined at Mexico's City abbatoir, where 8,000 corresponded to sheep and 5,000 to cattle. From those, 224 pneumonic lesions were observed, obtaining 97 positive isolates, which yielded 112 strains of Pasteurella sp. Forty isolates were identified as P. haemolytica and 72 as P. multocida. One-hundred percent of P. haemolytica belonged to biotype A. Serotypes were determined by indirect haemagglutination. P. multocida isolates were classified according to the acriflavine and hyaluronidase techniques, 61% belonged to type A, 25% to type D and 14% were untypified. Somatic serotypes were determined by gel immunodiffusion; serotype 3 was more frequent, in sheep 72% and in cattle 77%.

[Evaluation of phagocytosis, bactericidal effect, and cytotoxicity of Pasteurella haemolytica and Pasteurella multocida in bovine alveolar macrophages]. / Evaluación de fagocitosis, efecto bactericida y citotoxicidad de Pasteurella haemolytica y Pasteurella multocida en macrofagos alveolares de bovinos.

Evaluation of phagocytosis and bactericidal effect of Pasteurella haemolytica and P. multocida was conducted on bovine alveolar macrophages freshly obtained through bronchioalveolar washings from live animals. Cytotoxic activity of these bacteria on the alveolar macrophages was evaluated through the simple visual assay in microplates, using bovine blood leukocytes as a comparative target cell. In order to evaluate phagocytosis the following variables were considered P. haemolytica and P. multocida (independently) in contact with alveolar macrophages, P. haemolytica and P. multocida in suspension as a positive control of bacterial growth, and RPMI-1640 medium alone, as a negative control of bacterial growth. To measure bactericidal capacity, bacteria were incubated with plastic adhered alveolar macrophages at 30 minutes and 3 hours intervals. Samples incubated 30 minutes were taken as phagocytosis-base readings and at the 3 h interval to evaluate bactericidal capacity of the alveolar macrophages on phagocytized bacteria. Reading of the samples of each evaluation was conducted in a spectrophotometer a 380 nm. Phagocytosis results indicated that bacterial proliferation was higher when bacteria were alone as compared when they were with alveolar macrophages (p < 0.05). Bactericidal capacity of the macrophages was efficient because bacterial numbers were higher in the first evaluation as compared to the second (p < 0.05). It was demonstrated that the cytotoxic effect of P. haemolytica was more severe on blood leukocytes as compared to alveolar macrophages (p < 0.05). There was no evidence of P. multocida cytotoxicity on the evaluated cells. With the development of this technique for the obtention of alveolar macrophages and using spectrophotometry for the phagocytosis and bactericidal effect evaluations, numerous variables and samples can be tested, such as opsonized bacteria or to measure the behaviour of alveolar macrophages infected with different agents involved in the bovine pneumonic complex.

Pathogenesis of experimental bovine respiratory syncytial virus infection in sheep.

Conventionally reared lambs, seronegative to bovine respiratory syncytial virus (RSV), were inoculated with bovine RSV by an aerosol route. A mild clinical response, characterized by transient fever at postinoculation day (PID) 4, occurred and was accompanied by serous oculonasal secretions in less than 50% of the infected lambs. A decrease in total WBC was observed on PID 6 and 11, with a reduction in the total numbers of lymphocytes. Bovine RSV was recovered from nasal secretions of inoculated lambs from PID 2 to 6. The lambs were euthanatized, and at necropsy, the virus was only isolated from lambs killed between PID 2 and 4. Serum neutralizing antibodies were noticed as early as PID 6 and peaked at PID 13 to 15. Neutralizing antibodies were also detected at low concentration in pulmonary washings. Viral antigen was mainly located in alveolar walls and occasionally in bronchiolar epithelium and alveolar macrophages in lambs killed between PID 2 to 4. Later, specific fluorescence was only present in alveolar walls and was not observed in tissue from lambs killed after PID 22. Budding and free virus-like particles were observed by electron microscopy in type I and type II alveolar epithelial cells. Outstanding macroscopic lesions were not seen. Histologically, mild bronchiolitis and alveolitis were observed.

Interaction of bovine respiratory syncytial virus and Pasteurella haemolytica in the ovine lung.

The potential synergistic effect of bovine respiratory syncytial virus (RSV) and Pasteurella haemolytica in the production of pneumonia after aerosol/intranasal infection of conventionally reared lambs was evaluated. A mild clinical response was observed in lambs given virus and/or bacteria. Gross pulmonary lesions were seen in 3 of 6 lambs given RSV and then P haemolytica 3 or 6 days later, respectively (groups D and E), and in 1 lamb of 5 given virus and bacteria simultaneously (group G). Gross lesions were not seen in control sheep (group A), in lambs given virus or bacteria alone (groups B and C), or in lambs exposed to bacteria and then virus 3 days later (group F). Bovine RSV and P haemolytica were recovered from the lungs of 5 of 7 lambs with macroscopic lesions. Gross pulmonary lesions were cranioventral firm areas of red consolidation. Microscopically, the predominant lesion was a suppurative bronchopneumonia. Bovine RSV was recovered from the nasal cavity of 8 of 27 (30%) lambs given RSV during days 3 to 6 after viral inoculation, including 1 lamb in group B, 2 in groups D, E, and F, and 1 in group G. Pasteurella haemolytica was recovered from the nasal cavity of 9 of 28 (32%) inoculated lambs, including 2 lambs from groups C and E, 3 in group D, and 1 in groups F and G. Viral antigen, as determined by immunofluorescence, was concentrated mainly in individual cells in alveolar walls, some alveolar macrophages, and a few bronchiolar epithelial cells. In vitro alveolar macrophage assays indicated decreased numbers of Fc receptors on those macrophages collected from lambs given RSV 6 days before P haemolytica infection, as compared with that in the other groups. These cellular defects disappeared after 24 hours of culture. Seemingly, bovine RSV does facilitate P haemolytica pulmonary infection in conventional, immuno-competent lambs and provides evidence for decreased Fc receptors on alveolar macrophages.

A comparison of canine giant cell tumor and giant cell reparative granuloma of bone.

The clinical, radiographic, and pathologic features of a canine giant cell tumor of bone are compared with those of a giant cell reparative granuloma of bone. The giant cell bone tumor usually emerges from the epiphysis of long bones as a rapidly developing lytic bone lesion without periosteal new bone formation. The giant cell reparative bone granuloma originates preferentially in flat bones on the skull and mandible as a result of trauma-associated intraosseous hemorrhage, with new bone formation and sclerosis. Histologically, the neoplastic giant cells are scattered diffusely throughout the tissue, in contrast to the inflammatory giant cells that accumulate at the periphery of hemorrhages or around bone spicules. This peripheral accumulation is accompanied by a prominent collagenous and reticulum stroma. The morphologic and histochemical features of the giant cells can not be used as reliable tools to differentiate these two conditions.