Objective—To determine the disposition of gamithromycin in plasma, pulmonary epithelial lining fluid (PELF), bronchoalveolar lavage (BAL) cells, and lung tissue homogenate in cattle.
Animals—33 healthy Angus calves approximately 7 to 8 months of age.
Procedures—Calves were randomly assigned to 1 of 11 groups consisting of 3 calves each, which differed with respect to sample collection times. In 10 groups, 1 dose of gamithromycin (6 mg/kg) was administered SC in the neck of each calf (0 hours). The remaining 3 calves were not treated. Gamithromycin concentrations in plasma, PELF, lung tissue homogenate, and BAL cells (matrix) were measured at various points by means of high-performance liquid chromatography with tandem mass spectrometry.
Results—Time to maximum gamithromycin concentration was achieved at 1 hour for plasma, 12 hours for lung tissue, and 24 hours for PELF and BAL cells. Maximum gamithromycin concentration was 27.8 μg/g, 17.8 μg/mL, 4.61 μg/mL, and 0.433 μg/mL in lung tissue, BAL cells, PELF, and plasma, respectively. Terminal half-life was longer in BAL cells (125.0 hours) than in lung tissue (93.0 hours), plasma (62.0 hours), and PELF (50.6 hours). The ratio of matrix to plasma concentrations ranged between 4.7 and 127 for PELF, 16 and 650 for lung tissue, and 3.2 and 2,135 for BAL cells.
Conclusions and Clinical Relevance—Gamithromycin was rapidly absorbed after SC administration. Potentially therapeutic concentrations were achieved in PELF, BAL cells, and lung tissue within 30 minutes after administration and persisted for 7 (PELF) to > 15 (BAL cells and lung tissue) days after administration of a single dose.
Objective—To identify important pathogens and characterize their serologic and pathologic effects in porcine circovirus type 2 (PCV2)-infected pigs in relation to pig age and type of swine production system.
Animals—583 conventionally reared pigs.
Procedures—3- (n = 157), 9- (149), 16- (152), and 24-week-old (125) pigs from 41 different 1-, 2-, and 3-site production systems (5 pigs/age group/farm) were euthanized and necropsied. Pigs with and without PCV2 infection were identified (via PCR assay); infection with and serologic responses to other pathogens and pathologic changes in various tissues (including lungs) were assessed. Logistic regression models were constructed for effects overall and within each age group and type of production system.
Results—Compared with PCV2-negative pigs, PCV2-positive pigs were more likely to have swine influenza virus (SIV) type A and Mycoplasma hyopneumoniae infections and sample-to-positive (S:P) ratios for SIV H1N1 from 0.50 to 0.99; also, PCV2-positive pigs had higher serum anti-porcine reproductive and respiratory syndrome virus (PRRSV) antibody titers and more severe lung tissue damage. Infection with SIV (but lower SIV H1N1 S:P ratio) was more likely in 3-week-old PCV2-positive pigs and evidence of systemic disease was greater in 16-week-old PCV2-positive pigs than in their PCV2-negative counterparts. By site type, associations of coinfections and disease effects between PCV2-positive and -negative pigs were greatest in 3-site production systems.
Conclusions and Clinical Relevance—In PCV2-positive pigs, coinfections with SIV, M hyopneumoniae, and PRRSV are important, having the greatest effect in the early to late nursery phase and in 3-site production systems.
Objective—To evaluate variation of drinking-water flow rates in swine finishing barns and the relationship between drinker flow rate and plasma tetracycline concentrations in pigs housed in different pens.
Design—Cross-sectional (phase 1) and cohort (phase 2) studies.
Sample Population—13 swine finishing farms (100 barns with 7,122 drinkers) in phase 1 and 100 finishing-stage pigs on 2 finishing farms (1 barn/farm) in phase 2.
Procedures—In phase 1, farms were evaluated for water-flow variation, taking into account the following variables: position of drinkers within the barn, type of drinker (swing or mounted), pig medication status, existence of designated sick pen, and existence of leakage from the waterline. In phase 2, blood samples were collected from 50 pigs/barn (40 healthy and 10 sick pigs) in 2 farms at 0, 4, 8, 24, 48, and 72 hours after initiation of water-administered tetracycline HCl (estimated dosage, 22 mg/kg [10 mg/lb]). Plasma tetracycline concentrations were measured via ultraperformance liquid chromatography.
Results—Mean farm drinker flow rates ranged from 1.44 to 2.77 L/min. Significant differences in flow rates existed according to drinker type and whether tetracycline was included in the water. Mean drinker flow rates and plasma tetracycline concentrations were significantly different between the 2 farms but were not different between healthy and sick pigs. The plasma tetracycline concentrations were typically < 0.3 μg/mL.
Conclusions and Clinical Relevance—Many factors affected drinker flow rates and therefore the amount of medication pigs might have received. Medication of pigs with tetracycline through water as performed in this study had questionable therapeutic value.