Global distribution of tabanid flies, characterization and microbiome insights of Tabanus par (Diptera- Tabanidae)

Abstract

Tabanid species, commonly known as horse flies, are blood-feeding insects belonging to the family Tabanidae. These flies are significant pests due to their painful bites and their role as biological and mechanical vectors for various medical and veterinary pathogens, including parasites, bacteria, and viruses. Despite their importance, insufficient data exists regarding their classification and identification. This study addresses this gap by conducting a systematic review and meta-analysis of the global prevalence and distribution, followed by morphological, morphometric and genetic characterization using Tabanus par (T. par) as a model species. Additionally, the study explored the microbiome of T. par, including bacterial, viral, fungal and eukaryotic protozoan species. The systematic review revealed the presence of tabanid species across five continents and from 16 countries, with notable contributions from the USA, Croatia, and Bulgaria. An increasing trend in tabanid research was observed over the decades, with 209 species identified across five tribes. Morphological and genetic analyses of 30 T. par specimens confirmed species identification through mitochondrial cytochrome oxidase 1 (CO1) gene sequencing. Furthermore, phylogenetic analysis from the CO1 gene region showed that T. par collected from KwaZulu-Natal Province of South Africa are closely related to those of Mozambique as compared to those from West Africa. Metagenomic analysis of the T. par revealed distinct microbial diversity in the whole body (WB) and legs (L). Bacteria from the phylum Pseudomonodota were dominant, with Wolbachia sp. (34%) prevalent in WB and Burkholderia vietnamiensis (10%) in legs. The eukaryotic microbiome was dominated by the phylum Euglenozoa, with Trypanosoma theileri (32%) identified as a key pathogen. Fungal diversity was marked by Ascomycota, with Synchytrium and Fusarium proliferatum predominating in WB and legs, respectively. Viral metagenomics identified bacteriophages from Mycobacterium, Escherichia and Pseudomonas, with ten complete phage genomes characterized, indicating both lytic and temperate viral lifestyles. Additionally, three draft genomes of Spiroplasma species were identified from T. par. Pangenomics analysis revealed core genes associated with translation and replication, reflecting their endosymbiotic adaptation. In conclusion, findings of this entire study will contribute to the development of a comprehensive checklist of the family Tabanidae based on the systematic review and meta-analysis. Furthermore, data generated in this study documented a wide variety of microbial communities (bacterial, viral and fungal) harboured by South African T. par and will go a long way in playing a role in the formulation of solutions for the biological management of tabanid populations.