Rapid Visual Detection of Feline Panleukopenia Virus Using Colorimetric Loop-Mediated Isothermal Amplification Assay

Feline panleukopenia is an acute, highly contagious, and fatal infectious disease, posing a serious threat to the health and conservation of felids. It is necessary to develop diagnostic tools suitable for point-of-care testing (POCT). Herein, a colorimetric loop-mediated isothermal amplification (LAMP) assay targeting the FPV VP2 gene was developed using cresol red as a colorimetric indicator. The colorimetric LAMP enables result interpretation by visual observation of a color change from violet to yellow after amplification at 64 °C for 40 min. The limit of detection was 18.38 copies/µL for pMD-VP2 plasmid and 10^1.62 TCID₅₀/mL for crudely extracted nucleic acids. This method exhibits no cross-reactivity with other common feline pathogens, and shows good repeatability. Nevertheless, this method is unable to differentiate FPV from canine parvovirus (CPV) owing to their high genetic similarity. Testing of 153 clinical samples revealed a 40.52% (62/153) positive rate, with 98.04% agreement compared to a commercial qPCR kit (42.48% positive rate). Collectively, the developed colorimetric LAMP assay offers a specific, sensitive, simple and visual approach for FPV detection, demonstrating great potential for field point-of-care applications.