In recent years, tick-borne viral diseases have gained increasing attention due to their public health implications. The study titled "Striking tick-borne virus diversity and potential reservoirs documented during One-Health-based cross-sectional screening in Anatolia," published in Parasites & Vectors, highlights significant findings about the prevalence and diversity of tick-borne viruses across Anatolia, encompassing 19 provinces from seven distinct geographical regions.
Study Overview
The primary objective of the study was to screen for tick-borne viral pathogens in a One-Health framework, which integrates human, animal, and environmental health. A total of 1,358 samples were collected, including animal plasma and host-removed ticks. This expansive reach allowed researchers to employ generic and specific amplification assays and subsequent sequencing to identify potential viral pathogens. Remarkably, four viral entities emerged from the data: Crimean-Congo Hemorrhagic Fever Virus (CCHFV), Tetracyclic Tick Virus 1 (TcTV-1), Tick-Borne Nairovirus (TAMV), and Japanese Mammalian Tick Virus (JMTV). Notably, a tentative novel nairovirus was also detected.
Crimean-Congo Hemorrhagic Fever Virus (CCHFV)
CCHFV was one of the most significant findings. Identified in 18.7% of pooled tick samples and 1.1% of plasma samples, CCHFV is endemic to the region, with over 11,000 documented human infections between 2002 and 2018. Its average mortality rate during this period stood at 4.8%. Predominantly found in areas of Africa, Eastern Europe, the Middle East, and Asia, its emergence in Europe has recently heightened concern, particularly in countries such as Bulgaria, Greece, Spain, and Portugal.
In Anatolia, CCHFV primarily circulates in central and eastern regions, particularly around the Kelkit Valley. The study’s findings indicated the presence of three distinct CCHFV lineages, including the widely documented Europe 1 and 2 as well as an African lineage, highlighting the expanding genomic diversity of CCHFV in Anatolia. This genomic diversity raises concerns about its virulence and the potential for disease outbreaks linked to emerging variants. The findings suggest that the ongoing introduction of divergent virus clades may be influenced by migratory birds along the African-Western Palearctic flyway.
Tetracyclic Tick Virus 1 (TcTV-1)
TcTV-1 emerged as the most frequently identified tick-borne pathogen in the study, detected in six of the eleven tick species assessed, with an overall prevalence of 6.3%. This virus has been primarily documented in China. Its detection in the cattle plasma from Şanlıurfa province marks a significant finding, suggesting cattle may serve as reservoirs for zoonotic transmission. Interestingly, TcTV-1 was found to infect a variety of domestic animals, including sheep, goats, and dogs, increasing its potential vectors and hosts.
The genetic variability identified within TcTV-1 warrants further investigation to determine its implications for host transmission dynamics and virulence. Given the evidence of co-infections with other pathogens, including Rickettsia, the potential for severe health impacts on affected individuals must be further explored.
Tick-Borne Nairovirus (TAMV)
Another notable virus identified was TAMV, previously documented primarily in Central Asia. This study detected TAMV genomic material in tick samples and reinforces the notion of its spread across regions, including Anatolia. Historically associated with febrile diseases, TAMV has seen limited study within human populations. The presence of the virus across several tick species raises questions about its transmission mechanisms and animal reservoirs, emphasizing the necessity for further research in the region.
Japanese Mammalian Tick Virus (JMTV)
JMTV was also identified, primarily in Eastern Anatolia and the Black Sea regions, showcasing its prevalence and indicating localized viral diversity. Genome analysis revealed distinct clades, shedding light on the virus’s evolutionary trajectory and environmental adaptability. The presence of JMTV alongside CCHFV-positive cases could suggest potential interactions that may influence disease outcomes in a recognizable CCHFV-endemic setting.
Novel Nairovirus Discovery
In an exciting discovery, the study identified a novel nairovirus with significant genetic divergence from previously characterized strains. It forms a new lineage within the Nairoviridae family and was consistently detected in tick pools. Further exploration through genome sequencing and transcriptome analysis is essential to understand its ecological role and potential pathogenicity.
Implications for Public Health
The findings from this cross-sectional study contribute significantly to our understanding of tick-borne diseases in Anatolia. The integration of One-Health approaches helps bridge gaps between environmental, animal, and human health, ultimately directing targeted public health interventions.
Monitoring and Future Research: Continuous monitoring of tick populations and associated viral genomes is crucial. Regular surveillance helps in assessing the emergence of new variants and their public health implications. Furthermore, expanding the scope of research to investigate the role of domestic and wild animal reservoirs in virus transmission is vital for effective control strategies.
This study sets a foundation for future investigations that can inform public health policies and practices in combating tick-borne diseases. By ensuring ongoing research into emerging viral pathogens and their transmission dynamics, we can better protect vulnerable communities against the associated health threats.
Conclusion
The exploration of tick-borne viral diversity in Anatolia underscores the importance of integrated health surveillance and underscores the complexities of zoonotic disease management. By shedding light on the existing viral diversity and potential reservoirs, this investigation serves as a call to action for heightened awareness and proactive measures in addressing tick-borne diseases globally.
