Jeffrey J. Zimmerman

Detection of ceftiofur and oxytetracycline in oral fluids of swine with a pen-side competitive ELISA test after intramuscular injection.

Human studies have demonstrated the utility of oral fluids for the detection of hormone levels, infectious agents, and recreational drug use (Hofman, 2001). Components of human oral fluids are well understood, and human clinicians use oral fluids in diagnostic tests because of the ease, lack of intensive training, and relative painlessness associated with the collection of samples (Ghalaut et al., 2010). Oral fluids have also been examined as a matrix for diagnostic testing in domestic mammals (Prickett & Zimmerman, 2010). A protocol for collection and testing of oral fluids has been validated for the detection of disease (Prickett et al., 2008; Kittawornrat et al., 2010) and cortisol levels (Parrott & Mission, 1989) in swine. Levels of virus in oral fluid have been shown to increase proportionally to the amount of virus in serum of infected pigs (Kittawornrat et al., 2010). Currently, serum is the primary body fluid used in diagnostic testing for domestic mammals, but urine and milk are used in veterinary applications as well. Cow s milk is intensively screened for the presence of antibiotic residues, and tests have been adapted specifically for this purpose. These tests include commercial, tank-side, real-time applications in the field (SNAP Test; IDEXX Laboratories, Westbrook, ME, USA). The SNAP test is a competitive ELISA that is validated for detection of antibiotic residues in raw milk bulk tank samples. The AOAC Research Institute conducted an independent validation of the SNAP assay at the Department of Animal and Nutritional Sciences, University of New Hampshire and at the Dairy Quality Control Institute. (Certification Report of the New SNAP Beta-Lactam, AOAC Performance Tested Method 030302). When the manufacturer s raw milk test protocol is followed, two dots appear in the results window of the test kit; one representing the control for the test and one representing the sample. A SNAPshot test reader (IDEXX Laboratories) is used to quantify the result by comparing the reflective density of the test and control dots. For milk samples, when the ratio of these densities (control:test) exceeds 1.06, the test is reported as positive. The manufacturer reports detect levels at or below 13 ppb for ceftiofur and 50 ppb for oxytetracycline in milk. The purpose of this pilot study was to determine whether the SNAP test could detect antibiotic levels in the oral fluids of pigs after intramuscular (IM) injection with oxytetracycline or ceftiofur at labeled doses. Pigs were housed at Iowa State University, and all activities were approved by the Institutional Animal Care and Use Committee. The study used four pens (three pigs per pen) arranged in a 2 · 2 format with shared flooring such that all pens had nose-to-nose contact with the other three pens. Animals were fed an antibiotic-free diet that met NRC guidelines for swine. No antibiotic treatments were administered to any of the pigs for the 84 days prior to the study. At time zero, prior to any antimicrobial treatment, oral fluid was collected from all four pens by hanging a cotton rope in each pen for a minimum of 10 min or until all three pigs chewed on the rope. The portion of the rope saturated with oral fluid was put into a plastic bag (EPC, Chicago, IL, USA), and fluids were squeezed from the rope until they accumulated in the bottom of the bag. The bag was punctured with a 14-gauge Monoject sterile needle (Tyco Healthcare Group LP, Mansfield, MA, USA), and the fluid was drained into a 50-mL Falcon plastic tube (BD Biosciences, Mississauga, ON, Canada). The plastic tube was capped tightly, placed in its own plastic bag, and remained separate from the other tubes until testing. To conduct the study, each of the three pigs in Pen 1 and Pen 3 were restrained with a hog snare and injected intramuscularly (IM) with ceftiofur sodium (Naxcel ; Pfizer Animal Health, New York, NY, USA) at 4.36 mg ⁄ kg bodyweight. Pigs in Pen 2 and Pen 4 were injected IM with 18.18 mg ⁄ kg of oxytetracycline (Liquamycin LA-200 ; Pfizer Animal Health). Injections were performed using a Monoject 12-cc syringe (Tyco Healthcare Group LP), and a Monoject 20-gauge needle (Tyco Healthcare Group LP) and were administered in the dorsal-caudal neck region. Oral fluid samples were then collected as described earlier from the treated pens at 2, 6, 12, and 24 h postinjection and J. vet. Pharmacol. Therap. 34, 515–517. doi: 10.1111/j.1365-2885.2010.01259.x. SHORT COMMUNICATION

Persistence of Porcine Reproductive and Respiratory Syndrome in Pigs

First reported in the United States in 1987 and in Europe in 1990, porcine reproductive and respiratory syndrome has rapidly become the most important infectious disease problem in the North American swine industry. The etiological agent, porcine reproductive and respiratory syndrome virus (PRRSV), is a member of the family Arterivirdae in the order Nidovirales. PRRSV is a single-stranded, enveloped, positive-sense RNA virus with a genome of approximately 15 kb in length containing 8 open reading frames (ORFs) which are expressed as subgenomic mRNA. At present, PRRSV is present in at least 60 percent of North American swine herds (USDA:APHIS:VS, 1997)