Molecular evidence of prolonged shedding of lumpy skin disease virus (LSDV) in the semen of naturally infected cattle bulls.

Abstract

Shedding of lumpy skin disease virus (LSDV) in the semen of experimentally infected cattle bulls has been proven, but research on LSDV shedding in semen following natural infection is scarce. This study aimed to assess the incidence and duration of LSDV shedding in the semen of bulls following natural infection. Testing of 78 cattle bulls from four LSD outbreak-affected breeding farms in India during 2022-2023 confirmed LSDV infection through LSDV real-time quantitative PCR and antibody ELISA. Subsequent real-time quantitative PCR analysis of semen samples identified LSDV genome in semen from 13 of the 66 bulls (19.6%) across three farms (two in North and one in Northeast India), demonstrating LSDV shedding in semen under field conditions. The LSDV genome was detected up to 235 days post-onset of clinical signs in one bull and up to 175 days in four bulls, providing molecular evidence of prolonged shedding of LSDV in the semen of naturally infected bulls. Shedding of LSDV in semen occurred in both Indian and European cattle breeds, mostly in bulls with generalized skin nodular lesions. Some bulls continued shedding post-seroconversion and clinical recovery. Although unsuccessful virus isolation from semen limits inferences on infectivity, sequencing and phylogenetic analysis of marker genes from selected LSDV-positive semen samples revealed two distinct LSDV lineages (LSDV 1.2.1 and 1.2.2) in bulls. This study provided first molecular evidence of prolonged shedding of LSDV in the semen of bulls following natural LSDV infection in the field, emphasizing the need to screen semen from such bulls before use.