Microbiologic findings in feedlot cattle with acute interstitial pneumonia

Abstract

Results indicated that microbial respiratory tract pathogens are more common in cattle with AIP than in healthy pen mates. Control of bacterial pneumonia late in the feeding period may reduce the incidence of AIP at feedlots where AIP is a problem.

Feedlot Acute Interstitial Pneumonia

“…2,4 Emphysematous bullae or interstitial emphysema may be grossly evident. 2,4 It is important, however, to remember that the presence of grossly evident emphysema does not by itself confirm a diagnosis of AIP. Emphysema can develop after agonal breathing in cattle that die due to a variety of causes.…”

“…3 In some cases, lungs with gross lesions of AIP also have grossly apparent lesions of fibrinous bronchopneumonia (BRD) in the cranial and/or ventral lung, with firm, dark red, gray, or brown lung that has fibrin on the pleural surface. 2,5 In such cases, primary, possibly chronic, bronchopneumonia may have predisposed the animal to development of superimposed (secondary) AIP. This lesion is sometimes referred to as the upstairs-downstairs lesion.…”

“…[2][3][4] Neutrophils, macrophages, and sometimes eosinophils infiltrate into alveoli and airways. Edema and hemorrhage may be present in some lobules.…”

“…In cases of cattle that live longer, proliferation of alveolar type II pneumocytes occurs and is seen microscopically (the proliferative phase of AIP). [2][3][4] With more time, inflammatory cells and fibrous tissue may infiltrate the interstitial space. These are the microscopic lesions used to identify AIP.…”

Pathologies of Acute Interstitial Pneumonia in Feedlot Cattle

“…Post-mortem, animals were classified AIP positive by presenting histopathological lesions such as alveolar fibrin, hyaline membrane formation and pneumocyte hyperplasia in at least one lobe (Sorden et al, 2000;Woolums et al, 2004). Histopathological lesions were further defined as focal AIP (less than 10% of lobule affected), patchy AIP (more than 10% but less than 50% of the lobule affected), diffuse AIP (more than 50% of the lobule affected), bronchopneumonia (focal or diffuse acute/chronic), chronic bronchopneumonia (bronchopneumonia plus evidence of chronicity such as fibrosis or atelectasis), histopathological interstitial pneumonia (interstitial pneumonia lacking gross lesions described for AIP but having interstitial cellular or acellular interstitial infiltrates upon histopathological analysis).…”