Seroprevalence of segmented flavi-like Alongshan virus in horses.

Overview

• This study investigated the presence of Alongshan virus (ALSV), a tick-borne segmented flavi-like virus, in horse populations from multiple continents, finding a widespread and high prevalence of antibodies against the virus, which indicates frequent exposure.
• The research highlights the role of horses as sentinels for monitoring emerging tick-borne pathogens and calls for further studies to assess the potential health risks posed by ALSV to both animals and humans.

Background and Importance

• The emergence of new infectious diseases is a growing global health concern due to factors such as climate change, biodiversity loss, and increased international travel and trade.
• Ticks act as vectors transmitting many pathogens that lead to human and animal diseases, increasing the need for effective surveillance programs.
• Alongshan virus (ALSV) was first identified in 2017 in human patients in China and belongs to the segmented flavi-like virus group, which is unusual because typical flaviviruses have non-segmented genomes.
• ALSV can infect various mammals, but its natural reservoirs (hosts), modes of transmission, and geographical distribution are poorly understood.

Study Objectives

• To determine the seroprevalence (presence of antibodies indicating past infection or exposure) of ALSV in horses from different geographic regions including the Americas, Europe, and Oceania.
• To assess whether horses could serve as sentinel animals for ALSV surveillance and to better understand the virus’s spread.

Methods

• Used commercial serum pools from horses across three continents to test for anti-ALSV antibodies.
• Conducted a detailed antibody testing in a cohort of 473 Thoroughbred horses from Germany.
• Performed longitudinal monitoring of 124 horses over five years to track changes in antibody levels over time.

Key Findings

• Antibodies against ALSV were detected in 12 out of 13 serum pools from different global regions, indicating the virus has a wider geographic presence than previously recognized.
• In the German Thoroughbred cohort, a very high seroprevalence was observed, with 87.1% of horses testing positive for ALSV antibodies.
• A statistically significant association was found between horse age and antibody positivity – older horses were more likely to have antibodies, suggesting cumulative exposure over time.
• Longitudinal data showed dynamic antibody level changes with 71.77% of tracked horses testing positive at least once during the five-year study, indicating ongoing or repeated exposure rather than a single outbreak.

Implications

• The widespread presence of ALSV antibodies in horses suggests that the virus is commonly circulating in tick populations in diverse ecological regions.
• Horses, due to their high seroprevalence and accessibility, can be used as effective sentinel species to monitor the prevalence and spread of ALSV and potentially other tick-borne viruses.
• Understanding ALSV transmission dynamics is important for assessing risks to human health, as the virus was initially found in humans and shares features with other medically important flaviviruses.
• The findings call for intensified research into the ecology of ALSV, including identification of natural reservoirs, transmission cycles, and potential zoonotic risk.

Conclusion

• This study reveals that ALSV exposure is common in horse populations across different continents, highlighting a broader distribution than previously known.
• Frequent exposure reflected in high seroprevalence underscores the importance of further monitoring and research to understand the role of ALSV in animal and human disease.
• Overall, horses represent a valuable indicator species for tracking emerging tick-borne pathogens like ALSV in the environment.