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 127.2 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
Conclusion 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. (Am J Vet Res 2001;
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
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.
Conclusion and Clinical Relevance—Increased
pulmonary production of 3MEIN may be an important
etiologic factor in feedlot-associated AIP. (Am J Vet