# Evaluation of the vector competence of Ixodes persulcatus in the maintenance and transmission of Alongshan virus under laboratory conditions

## TL;DR

This study shows that Ixodes persulcatus ticks can efficiently transmit Alongshan virus to mice both vertically and horizontally under lab conditions.

## Contribution

The first experimental evaluation of Ixodes persulcatus vector competence for Alongshan virus.

## Key findings

- ALSV RNA levels in ticks peaked 7 days post-infection and were highest in midgut tissues.
- Ticks transmitted ALSV to mice through bites, with higher viral loads in mice bitten by immature ticks.
- Vertical transmission was confirmed as viral RNA was detected in eggs and all developmental stages.

## Abstract

Alongshan virus (ALSV) is an emerging tick-borne segmented flavivirus associated with human febrile illness, belonging to Jingmenvirus group in the family Flaviviridae. Ixodes persulcatus (I. persulcatus) has been considered as the competent vector of ALSV in the field studies; however, no experimental study has yet evaluated the vector competence of I. persulcatus in the maintenance and transmission of ALSV.

I. persulcatus adult ticks were infected with ALSV via anal pore microinjection. salivary glands (SG), midgut (MG), and ovaries (OV) were collected and subjected to quantitative real-time polymerase chain reaction (RT-qPCR) for ALSV RNA detection. Ticks fed on Kunming (KM) or NOD-SCID IL2rg-/- (NTG) mice, and their eggs, molted progeny, and mice tissues were collected for ALSV RNA detection to evaluate vector competence in maintaining and transmitting ALSV.

Viral RNA levels in ALSV-microinjected ticks increased significantly, peaking at 7 d.p.i. Viral RNA in SG, MG, and OV tissues showed a significant upward trend over time, with higher copy numbers in MG than in SG and OV. Eggs, hatched larvae, engorged larvae, molted nymphs, engorged nymphs, and adults all exhibited high levels of viral RNA copies, ranging from approximately 106 to 109 copies/μL. Viral RNA was detected in the blood and tissues of mice bitten by ALSV-infected adult, larval, and nymphal ticks, with lower RNA copies in adult-bitten mice than in larvae- or nymph-bitten mice. Notably, viral RNA copy numbers were significantly higher in the blood and tissues of mice inoculated with ALSV and then bitten by ALSV-free immature ticks, compared to those receiving ALSV alone.

The results demonstrate that I. persulcatus ticks are competent vectors for ALSV, capable of transmitting the virus both vertically and horizontally with high efficiency, with tick bite-induced modulation of viral levels in mice varying according to the developmental stage of the tick.