Lumpy skin disease (LSD) is an important viral disease of cattle characterized by fever, multiple cutaneous nodules and plaques, lesions of mucous membranes and internal organs, regional lymphadenopathy, progressive emaciation, skin oedema, and occasional mortality. The disease is caused by members of the genus Capripoxvirus (family Poxviridae), including lumpy skin disease virus (LSDV), sheep pox virus and goat pox virus; these viruses are antigenically and genetically related. In susceptible cell cultures, LSDV produces a characteristic cytopathic effect and intracytoplasmic inclusion bodies. Transmission in the field is considered to be predominantly via blood-feeding arthropod vectors, whereas direct contact transmission without vectors is generally inefficient (WOAH, 2024).

LSD is endemic in many countries of Africa and the Middle East and, since 2015–2016, has expanded into parts of southeastern Europe, the Balkans and the Caucasus, demonstrating its capacity for rapid transboundary spread under favourable ecological and movement conditions (WOAH, 2024). Rapid and accurate laboratory confirmation is essential for outbreak control: conventional gel-based PCR provides a simple, rapid and sensitive method for detecting capripoxvirus DNA in EDTA blood, tissue, semen or cell-culture samples, while validated quantitative real-time PCR assays offer faster turnaround, increased analytical sensitivity and the ability to quantify viral genomes. Real-time assays that discriminate LSDV from sheep pox and goat pox viruses have also been described (FAO, 2017; Lamien et al., 2011).

Control of LSD relies primarily on mass prophylactic vaccination of susceptible cattle populations in endemic and at-risk areas. Live-attenuated homologous vaccines (e.g., Neethling-strain derivatives) are widely authorized and used in Africa; harmonized regional vaccination campaigns and high coverage (commonly targeted at ≈80 % of the susceptible population) are important for effective suppression of virus circulation. Vaccination policy should consider maternal immunity and production status: calves born to naive dams may be vaccinated at any age, whereas calves with passive maternal antibodies are typically vaccinated at 3–6 months; practical programmes usually include vaccination of all age groups, including young calves and pregnant cows, and prioritize regional campaigns over ring vaccination where feasible (WOAH, 2024; Balinsky et al., 2008; Haegeman et al., 2021a).

Accurate potency assessment for seed virus and final vaccine preparations requires reliable titration in cell culture (tissue-culture tubes or microtitre plates) and, when the minimum immunising dose is not established, batch potency tests in cattle that compare lesion development after virulent challenge between vaccinated and control animals. Classical infectivity endpoints and titration calculations (e.g., the Karber method) remain widely used for these determinations (Haegeman et al., 2021a; Kärber, 1931).

In parallel with these classical approaches, our group and collaborators are developing and validating alternative, rapid methods for evaluation of veterinary vaccines — including lateral-flow devices, quantitative molecular assays and PCR-based surrogate potency approaches — that can reduce reliance on lengthy tissue-culture assays and extensive in vivo challenge testing while preserving reliable estimates of vaccine quality and potency (Abousenna et al., 2024; Shafik et al., 2024; Abousenna et al., 2021; Abousenna et al., 2020a; Abousenna et al., 2020b). These alternative methods have shown promise when applied to a range of veterinary vaccines (canine parvovirus, FMD, Rift Valley fever, sheep pox), and motivate the present evaluation of live-attenuated LSDV vaccine batches using qPCR against tissue-culture and challenge outcomes.

The present study aims to evaluate commercial batches of live-attenuated LSDV vaccine using a validated real-time PCR assay for identification and quantification, to compare qPCR-derived titers with conventional tissue-culture infectivity titration, and to assess the relationship between vaccine/seed virus titer and in vivo potency in a calf challenge model.