Lack of abundant core virome in mosquitoes from a temperate climate region despite a mosquito species-specific virome.

In arthropod-associated microbial communities, insect-specific viruses (ISVs) are prevalent yet understudied due to limited infectivity outside their natural hosts. However, ISVs might play a crucial role in regulating mosquito populations and influencing arthropod-borne virus transmission. Some studies have indicated a core virome in mosquitoes consisting of mostly ISVs. Employing single mosquito metagenomics, we comprehensively profiled the virome of native and invasive mosquito species in Belgium. This approach allowed for accurate host species determination, prevalence assessment of viruses and , and the identification of novel viruses. Contrary to our expectations, no abundant core virome was observed in mosquitoes from Belgium. In that regard, we caution against rigidly defining mosquito core viromes and encourage nuanced interpretations of other studies. Nonetheless, our study identified 45 viruses of which 28 were novel, enriching our understanding of the mosquito virome and ISVs. We showed that the mosquito virome in this study is species-specific and less dependent on the location where mosquitoes from the same species reside. In addition, because has previously been observed to influence arbovirus transmission, we report the prevalence of in Belgian mosquitoes and the detection of several mobile genetic elements. The observed prevalence ranged from 83% to 92% in members from the complex.IMPORTANCE mosquitoes are important vectors for arboviruses like West Nile virus and Usutu virus. Virome studies on individual , and on individual mosquitoes in general, have been lacking. To mitigate this, we sequenced the virome of 190 individual and 8 individual mosquitoes. We report the lack of a core virome in these mosquitoes from Belgium and caution the interpretation of other studies in this light. The discovery of new viruses in this study will aid our comprehension of insect-specific viruses and the mosquito virome in general in relation to mosquito physiology and mosquito population dynamics.