Comparison of the local safety of two multi-component feline vaccines, adjuvanted (1 mL) versus non-adjuvanted at reduced volume (0.5 mL), using computed tomography imaging

In 2020, a new 0.5 mL presentation of PUREVAX® RCP FeLV was registered and introduced in Europe. The objectives of this study were to investigate the local safety of this non-adjuvanted vaccine at reduced volume by classical methods (clinical examination, histopathology) and to evaluate the suitability of an alternative non-invasive methodology, the computed tomography (CT). For this purpose, the course of local reactions was assessed for 3 months after subcutaneous injection of PUREVAX® RCP FeLV 0.5 mL and compared to an adjuvanted vaccine, LEUCOFELIGEN® FeLV/RCP 1.0 mL. Injection site reactions consisted mainly of swelling reactions, which were more frequent, more pronounced and long-lasting in the adjuvanted vaccine group. Microscopically, in this group, moderate to severe inflammatory reactions were observed on day 7 (D7) and D21 post-injection and still present on D84, while mild inflammatory lesions were observed in the non-adjuvanted vaccine group only on D7 and D21. With the adjuvanted vaccine, inflamed areas were measurable by CT scan in all cats on D7 and D21, whereas they were detected only on D7 and only in 20 % of cats from the non-adjuvanted vaccine group. Besides the higher frequency, the mean inflamed volume was nearly 300 times larger in adjuvanted vaccine group on D7. Using different methodologies, the favorable safety profile of PUREVAX® RCP FeLV 0.5 mL was confirmed. Furthermore, the vaccine is aligned with current vaccination guidelines by inducing less inflammatory reactions, being adjuvant-free and injectable under a reduced volume, thus improving the convenience of administration in recommended sites (eg, legs). CT scan proved to be a suitable non-invasive method for the experimental follow-up of injection site reactions, yielding results consistent with clinical assessment and histopathology on D7 and D21. CT scan substantiated large differences between the investigated vaccines with a more prominent inflammatory reaction after injection of an adjuvanted vaccine.

CT angiography and MRI imaging features do not predict the tumor type and grade of feline injection site sarcoma

Computed tomographic angiography (CTA) and magnetic resonance imaging (MRI) have been described as methods for preoperative surgical planning in cats with feline injection site sarcomas (FISS), however, few published studies have compared these modalities. The objective of this retrospective, secondary analysis study was to determine if imaging features of FISS on CTA and MRI are predictive of neoplastic peritumoral projections. Archived data from a previous prospective study were retrieved for 10 cats with FISS. All cats had been evaluated in a single anesthetic episode with MRI and dual phase CT (CTA) imaging followed by surgical removal. Histopathological grading and targeted histopathology of imaging-identified peritumoral projections were performed. Two observers evaluated the CTA and MRI studies for FISS shape, margination, size, enhancement pattern, postcontrast uniformity, pre- and postcontrast margination, the number of muscles involved, mass mineralization, and bone lysis. Metal was present in the imaging field of three of 10 cats, resulting in one nondiagnostic MRI. Peritumoral projections were detected in all cats with both imaging modalities, and most were benign. At least one neoplastic peritumoral projection was detected in six cats using MRI, five cats using CTA, and three cats with both modalities. Higher grade FISS were larger than low grade using MRI, and FISS were larger using MRI. Other FISS imaging features using MRI and CTA were similar. Findings supported use of either MRI or CTA for detecting neoplastic peritumoral projections in cats with FISS. Authors recommend CTA for cats with known metallic objects in the scan field.