Emergency vaccination of cattle against lumpy skin disease: Evaluation of safety, efficacy, and potency of MEVAC® LSD vaccine containing Neethling strain

Abstract

Lumpy skin disease (LSD) is an emerging disease of cattle causing significantly high economic losses. Control of LSD depends on the use of homologous attenuated LSD virus strains isolated originally from South Africa (the Neethling strain). The virus belongs to the genus Capripoxvirus, which includes sheep pox virus and goat pox virus. The present study was conducted to evaluate the safety and efficacy of a new live attenuated LSD vaccine produced by Middle East for Vaccines (MEVAC^®) based on the Neethling strain. Tests were performed both in Egypt and Vietnam. Safety was evaluated by inoculation of five cattle with 10 times the recommended dose and observation of the animals for 14 days. Immunogenicity was tested at different periods post-vaccination (PV) in animals receiving the recommended doses of the vaccine using ELISA and virus neutralization test. Five cows were used to determine the protection index (PI) and non-vaccinated control cattle were included. Three calves were challenged by intradermal inoculation of the wild virus (5 × 10⁵ TCID₅₀) 28 days PV. Field or mass vaccination experiments were conducted in Vietnam during national campaigns in the summer of 2021 with 4301 vaccinated animals closely monitored after vaccination. In the field, around 2% (80/4301) of the animals showed hyper-reactivity, and 0.6% (24/4301) showed small skin swellings that disappeared within few hours PV. Abortion was recorded in three animals (0.3% 3/867). Challenged animals were resistant to clinical disease and PI value was 3.5 log₁₀. Meanwhile, antibody levels determined by the ELISA were inconsistent among animals and laboratories during the study period. Overall, the findings point to a new safe and effective LSD vaccine.

Keywords: Lumpy skin disease; Neethling strain; Post-vaccination reaction; Seroconversion; Vaccine; Vaccine evaluation.

Fig. 1

A cow’s head showing tears, ruffled hair, and wrinkled face skin after lumpy skin disease vaccination

Fig. 2

Average rumination index monitored after vaccination in two cattle farms in Vietnam. Farm-1 (n = 30): average rumination index decreased by 1st day post-vaccination (PV), then recovered and tended to increase from 2nd day and remained stable afterwards. Farm-2 (n = 35): average rumination index increased by 2nd day PV then decreased from 3rd to 4th days and was recovered afterwards

Fig. 3

Average health index monitored after vaccination in two cattle farms in Vietnam. Farm-1 (n = 30): showed minor fluctuations after vaccination. Farm-2 (n = 35): average health index was stable after vaccination. PV: Post-vaccination

Fig. 4

Average milk yield monitored after vaccination in two cattle farms in Vietnam. Farm-1 (n = 30): average milk yield tended to increase slightly after vaccination (from 10.4 L/day at 1 day before vaccination to 11.5 L/day at 7th day PV). Farm-2 (n = 35): average milk yield of vaccinated cows decreased slightly after vaccination (from 17.5 L/day at 1 day before vaccination to 15.6 L/day at 7th day PV). PV: Post-vaccination

Fig. 5

Seroconversion percent of vaccinated animals (n = 65) at different intervals post-vaccination using IDvet Capripox ELISA. (D: days post-vaccination)