Jiangting Niu

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.

Feline herpesvirus type 1 (FHV-1) is one of the major pathogens causing upper respiratory tract disease (URTD) in cats, and is widely prevalent among domestic cats and other felids worldwide. Herein, we developed a closed one-tube colorimetric and fluorescent LAMP assay targeting the FHV-1 TK gene, using cresol red as the colorimetric indicator and EvaGreen as the fluorescent dye. The assay was completed within 40 min at 63 °C, with results readable either by colorimetric observation or fluorescence amplification curve. FHV-1-positive reaction could be confirmed by a color change from violet to yellow with the naked eye, and also could be determined by fluorescence amplification curve. The assay showed no cross-reactivity with other related pathogens, and had a detection limit of 100 copies. Among 87 clinical nasal swabs tested, 44 were positive, achieving an overall agreement of 97.7% compared to TaqMan quantitative PCR. The newly developed LAMP assay is simple, efficient, result-visual and reliable, which can be applied in the clinical diagnosis and epidemiological investigation of FHV-1, especially for point-of-care testing of FHV-1 in primary veterinary clinics and field settings.