Fine-needle aspiration and cytology as an antemortem method for evaluating injection-site lesions

Charles E. Wiedmeyer, DVM, PhD, Diplomate ACVP; Thomas J. Fangman, DVM, MS, Diplomate ABVP; Kent Schwartz, DVM, MS; Brian Payne, DVM

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Objectives: To apply a fine-needle aspirate (FNA) technique to evaluate grossly visible injection-site reactions by cytologic examination and determine agreement with gross and histopathological findings.

Materials and methods: Two trials were conducted. In both, pigs were vaccinated with porcine circovirus type 2 vaccine at weaning and 17 days later. Seven days after the second vaccination, pigs with grossly visible injection-site lesions were selected (Trial 1, n = 40; Trial 2, n = 12). In Trial 1, pigs were manually restrained for the FNA procedure. In Trial 2, pigs were sedated and the FNA procedure was conducted using two different-sized hypodermic needles (18-gauge and 22-gauge). After the FNA procedure, pigs were euthanized and the injection-site lesions and lymph nodes dissected and submitted for histopathologic interpretation. All cytologic preparations were examined by a board-certified veterinary clinical pathologist.

Results: In Trial 1, the cytologic interpretation of the samples was mild lymphocytic to mixed inflammation. Lesions were suggested to be the result of an immunologic response to the vaccine, not hemorrhage or abscess. In Trial 2, no differences were detected between preparations made with an 18-gauge or 22-gauge needle. Cytologic and histological findings agreed, reporting low to moderate numbers of lymphocytes and macrophages, with low numbers of neutrophils, foreign material, and bacteria.

Implications: The FNA procedure described is a potential technique practitioners can utilize to characterize tissue-reaction lesions without the need for euthanasia or surgical biopsy.

Keywords: antemortem, injection sites, fine-needle aspirate, cytology

RIS citationCite as: Wiedmeyer CE, Fangman TJ, Schwartz K, et al. Fine-needle aspiration and cytology as an antemortem method for evaluating injection-site lesions. J Swine Health Prod 2014;22(5):244-247.

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