First Molecular and Serological Evidence of Nairobi Sheep Disease Virus in Haemaphysalis longicornis and Sheep in Eastern Shandong Peninsula , China

This study provides the first molecular and serological evidence of Nairobi Sheep Disease Virus (NSDV) circulation in Haemaphysalis longicornis ticks and domestic sheep within the eastern Shandong Peninsula, China. NSDV, a tick-borne pathogen causing severe hemorrhagic disease in small ruminants, poses significant threats to livestock and potentially human health. Despite its endemicity in parts of Africa and Asia, its presence in eastern China remained poorly characterized. Researchers collected 1,386 Haemaphysalis longicornis ticks and 486 serum samples from domestic ruminants (sheep and cattle) across rural areas of Weifang and Yantai in Shandong. Molecular screening via qRT-PCR revealed NSDV RNA in 2.3% of tick pools (6/259), with phylogenetic analysis confirming close genetic ties to strains from Kenya and neighboring Chinese provinces. Serological assays (ELISA and IFA) detected NSDV-specific antibodies in 12.8% of sheep sera (34/265), while all cattle sera tested negative. The findings highlight Haemaphysalis longicornis as a probable vector and sheep as susceptible hosts in this emerging region. Notably, this study identifies eastern Shandong Peninsula-a major livestock hub-as a new frontier for NSDV transmission, distinct from prior reports in Rizhao (southern Shandong). The coexistence of viral RNA in ticks and antibodies in sheep underscores enzootic maintenance, urging enhanced surveillance for this neglected arbovirus. These results fill critical gaps in understanding NSDV ecology in East Asia and emphasize risks to veterinary and public health systems.