Validation of a diagnostic tool for the diagnosis of lumpy skin disease

Lumpy skin disease (LSD) is caused by LSD virus which is a member of the Capripoxvirus (CaPV) genus. Although PCR provides for a rapid and sensitive diagnosis, it has limited use due to its complexity in terms of cost, time and equipment. Loop-mediated isothermal amplification (LAMP) is a simple, specific and cost-effective method with a diagnostic accuracy similar to PCR.

To compare the detection rate (DR) of two LAMP assays versus PCR for the detection of CaPV.

This study used 105 apparently health animals (AHA) and 59 clinically sick animals (CSA).

PCR and LAMP assays (LAMP1 and LAMP 2) were compared for detection of CaPV from AHA and CSA using blood and tissue samples. The detection was confirmed by sequencing of PCR positive samples. Analytical sensitivity and specificity of LAMP assays also were assessed.

The DR in CSA was 13.6% for PCR whereas for LAMP it was 39.0% and 25.4% for LAMP 1 and 2 methods, respectively. In AHA, the LAMP assay DR was 14.3% and 1.9% for LAMP 1 and 2, respectively. Phylogenetic tree analysis confirmed the identity of CaPV. Analytic sensitivity showed a detection limit of 8 copies/μL. The analytic specificity test showed no cross detection with other infectious agents.

Good sensitivity and specificity results for LAMP assay support its application in the routine diagnosis of LSD, whereas its ability to detect LSDV in apparently healthy animals shows its usefulness in identifying populations at risk of LSD.