ABSTRACT
BACKGROUND: 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. OBJECTIVES/HYPOTHESIS: To compare the detection rate (DR) of two LAMP assays versus PCR for the detection of CaPV. ANIMALS: This study used 105 apparently health animals (AHA) and 59 clinically sick animals (CSA). METHODS AND MATERIALS: 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. RESULTS: 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. CONCLUSION AND CLINICAL IMPORTANCE: 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.
Subject(s)
Lumpy Skin Disease/diagnosis , Animals , Capripoxvirus/genetics , Cattle , Lumpy Skin Disease/virology , Nucleic Acid Amplification Techniques/veterinary , Polymerase Chain Reaction/veterinary , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
Free-range rural chickens (FRCs) dominate the poultry industry in developing countries and chickens are exposed to multi-host infections, including Newcastle disease virus (NDV). The knowledge about the characteristics of NDV from FRCs is limited. This study investigated the persistence, spread and risks of NDV from FRCs. NDV isolates (n = 21) from unvaccinated FRCs in Tanzania were characterised by conventional intracerebral pathogenicity index (ICPI) and sequence analysis of a partial region of the deduced fusion protein encompassing the cleavage site. Results showed that five isolates were screened as lentogenic, nine as mesogenic and six as velogenic. Phylogenetic analysis of the 21 isolates compared to reference sequences revealed three, four, nine and five isolates in genotypes 1, 2, 3c and 4a, respectively. Genotype 3c also included published sequences of Tanzanian isolates obtained from exotic birds and chicken isolates from Uganda. The analysis showed that NDV were persistently present among chicken populations and possibly spread through live chicken markets or migration of wild birds. Differences in amino acid sequences detected around the cleavage site separated the isolates in six types. However, cleavage site pattern could not fully differentiate mesogenic isolates from velogenic isolates.
