Molecular and serological evidence of Nairobi sheep disease virus in Haemaphysalis longicornis and sheep in eastern Shandong Peninsula, China.

NSDV circulates in eastern Shandong ticks and ruminants, requiring enhanced surveillance and control strategies.

This surveillance study documents the presence of Nairobi sheep disease virus (NSDV) in the eastern Shandong Peninsula, China, through molecular and serological investigation. Researchers collected 745 Haemaphysalis longicornis ticks (139 pools) and 246 ruminant serum samples during 2021 field surveillance in Weifang and Yantai regions. Molecular detection using qRT-PCR and nested PCR identified NSDV RNA in 9 tick pools (1.2% minimum infection rate). Complete genomic sequencing revealed one full genome with high nucleotide identity (>98%) to Chinese reference strains. Serological analysis demonstrated 5.7% seroprevalence (14/246) in ruminants, indicating local virus exposure. Phylogenetic analysis clustered Shandong isolates with other Chinese NSDV variants, suggesting regional spread rather than independent introductions. These findings extend NSDV's known geographic range beyond its historical East African endemic zone and document its establishment in Asia. The study highlights the importance of integrated tick-ruminant surveillance systems and underscores zoonotic and economic risks associated with this highly pathogenic orthonairovirus.

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