Oropouche Virus & Italian Mosquitoes: Vector Competence Study
Vector Competence of Italian Mosquitoes for Oropouche Virus: Implications for European Risk
Table of Contents
Introduction
Oropouche virus (OROV) is an emerging arbovirus traditionally circulating in the Amazon basin, causing Oropouche fever – a dengue-like illness. Recent outbreaks in central and South America, coupled with the first documented cases in Italy in 2024, raise concerns about its potential establishment in new geographical regions, particularly Europe. Effective public health responses require a thorough understanding of the virusS transmission dynamics, crucially dependent on the vector competence of local mosquito populations. This study investigates the ability of two primary Italian arbovirus vectors, Culex pipiens and Aedes albopictus, to transmit the recently circulating Cuban strain of OROV, providing critical insights into the potential risk of local transmission.
Background on Oropouche Virus and Vector Competence
OROV, belonging to the Orthobunyavirus genus, is primarily transmitted by Culicoides midges in its natural sylvatic cycle. tho,outbreaks increasingly involve Aedes and Culex mosquitoes as bridge vectors,amplifying the virus and transmitting it to humans. Vector competence – the ability of a mosquito to acquire,maintain,and transmit a virus – is a complex trait influenced by multiple factors,including mosquito species,virus strain,and environmental conditions.
Previous research, including a systematic review by Carlson [1], has highlighted the importance of midgut barriers in limiting OROV acquisition and dissemination, suggesting that viral incompatibility with mosquito physiology is less of a factor than previously thought. Payne et al. [2] recently reported a single positive saliva sample from Cx. pipiens, indicating a potential, albeit limited, role for this species in OROV transmission. Understanding the vector competence of European mosquito populations is thus paramount.
Methods
This study assessed the vector competence of Italian Cx. pipiens and Ae. albopictus mosquitoes for the OROV strain responsible for the 2024 outbreaks in Cuba. Mosquitoes were exposed to OROV through an artificial blood meal. Following virus exposure, mosquitoes were maintained under controlled laboratory conditions, and their infection status was assessed at multiple time points post-infection. Viral titers were determined in mosquito bodies, saliva, and legs using plaque assays. Transmission potential was evaluated by assessing infection rates in F1 progeny. Due to Biosafety Level 3 (BSL-3) constraints,sample sizes were limited,and experiments were not fully replicated.
Results
Our study revealed a lack of robust OROV infection in both cx. pipiens and Ae. albopictus. While no OROV infection was detected in Cx. pipiens, the single positive saliva sample reported by Payne et al. [2] warrants continued investigation. In Ae. albopictus,we observed limited viral replication in the mosquito body,but dissemination to the saliva and legs was minimal. Importantly, no transmission to the F1 generation was observed in either species. Thes findings suggest a low vector competence for the tested OROV strain in the studied Italian mosquito populations.
Discussion
The observed lack of efficient OROV infection and transmission in Italian Cx. pipiens and Ae. albopictus mosquitoes provides preliminary evidence of a negligible risk of local OROV circulation via these two primary vectors.This aligns with Carlson’s [1] findings emphasizing the role of midgut barriers in restricting virus acquisition. However,the detection of a positive saliva sample in Cx. pipiens by Payne et al.[2] underscores the need for ongoing, geographically targeted surveillance.
It is indeed crucial to acknowledge the limitations of our study, including the absence of biological replicates and the limited sample sizes imposed by BSL-3 requirements. The assessment of transmission was restricted to the F1 generation, and further studies evaluating subsequent gonotrophic cycles are necessary. Despite these limitations, our results offer an early indication to health authorities regarding the current risk level.
The possibility of viral adaptation and co-evolutionary processes cannot be discounted.OROV may evolve to overcome existing mosquito barriers, possibly leading to increased vector competence and geographical expansion. The recent introduction of OROV cases into Italy and other non-endemic regions, alongside its expanding presence in Central and South America, necessitates a proactive approach.
Conclusion and Future directions
This study provides evidence that Italian Cx. pipiens and Ae. albopictus mosquitoes exhibit limited vector competence for the recently circulating Cuban strain of OROV. However