Objective—To model the plasma tetracycline concentrations in swine (Sus scrofa domestica) treated with medication administered in water and determine the factors that contribute to the most accurate predictions of measured plasma drug concentrations.
Sample—Plasma tetracycline concentrations measured in blood samples from 3 populations of swine.
Procedures—Data from previous studies provided plasma tetracycline concentrations that were measured in blood samples collected from 1 swine population at 0, 4, 8, 12, 24, 32, 48, 56, 72, 80, 96, and 104 hours and from 2 swine populations at 0, 12, 24, 48, and 72 hours hours during administration of tetracycline hydrochloride dissolved in water. A 1-compartment pharmacostatistical model was used to analyze 5 potential covariate schemes and determine factors most important in predicting the plasma concentrations of tetracycline in swine.
Results—2 models most accurately predicted the tetracycline plasma concentrations in the 3 populations of swine. Factors of importance were body weight or age of pig, ambient temperature, concentration of tetracycline in water, and water use per unit of time.
Conclusions and Clinical Relevance—The factors found to be of importance, combined with knowledge of the individual pharmacokinetic and chemical properties of medications currently approved for administration in water, may be useful in more prudent administration of approved medications administered to swine. Factors found to be important in pharmacostatistical models may allow prediction of plasma concentrations of tetracycline or other commonly used medications administered in water. The ability to predict in vivo concentrations of medication in a population of food animals can be combined with bacterial minimum inhibitory concentrations to decrease the risk of developing antimicrobial resistance.
Objective—To test the hypothesis that feedlot cattle
with acute interstitial pneumonia (AIP) have bacterial
infection of the lung or liver and concurrent bovine
respiratory syncytial virus (BRSV) infection significantly
more often than pen mates without AIP.
Animals—39 feedlot cattle with signs consistent
with AIP and no history of treatment with antimicrobials
and 32 healthy control cattle from the same
Procedure—Lung and liver specimens were
obtained postmortem for bacterial or mycoplasmal
culture and histologic examination; lung tissue was
assessed for BRSV infection immunohistochemically.
Results—Among affected cattle, 26 had AIP confirmed
histologically. Lung tissue from 11 cattle with
AIP yielded microbial respiratory tract pathogens on
culture; tissues from control animals yielded no
microbial growth. In 4 cattle with AIP and 2 control
animals, liver abscesses were detected; bacteria
were isolated from abscessed tissue in 3 and 1 of
those animals, respectively. Immunohistochemically,
9 cattle with AIP and no control animals were BRSV-positive.
Histologically, 9 AIP-affected cattle had only
acute alveolar damage with exudation, and the other
17 had acute exudation with type II pneumocyte
hyperplasia. No lesions of AIP were detected in control
animals. Only 4 AIP-affected cattle had bacterial
infection of the lung with concurrent BRSV infection.
Conclusions and Clinical Relevance—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. (Am J Vet Res 2004;65:1525–1532)