|dc.description.abstract||Tabanids are biting flies commonly referred to as horse flies, deer flies or clegs. They belong to the family Tabanidae composed of more than 4 400 species belonging to 114 genera with a cosmopolitan distribution. Tabanids are of economic importance worldwide due to their ability to transmit various pathogens including bacteria, viruses and protozoa. In southern Africa little has been done to characterize tabanid flies to species level using molecular techniques, and there is insufficient knowledge on the role played by tabanid flies in transmission of haemoparasites. As a result the current study was aimed at characterizing tabanid flies (Tabanidae) in selected study sites in Lesotho, South Africa and Zambia. Morphological identification and molecular techniques were used to characterize tabanid flies found in the three countries to species level. Furthermore, this study sought to detect protozoan parasites of veterinary importance harboured by the sampled tabanid species. Lastly, metagenomic analysis was conducted to determine the gut microbiota of the sampled tabanid flies in order to identify genera of medical or veterinary importance and genera involved in symbiotic associations with arthropods.
A total of 529 tabanid flies comprising of 2 from Lesotho, 307 from South Africa and 157 from Zambia, were collected. Morphological analysis revealed a total of 5 different genera collected from the sampled areas namely: Ancala, Atylotus, Haematopota, Philoliche and Tabanus. The overall number of members from the genus Tabanus was greater than all other genera combined. Morphological identification was further supported by amplification of mitochondrial cytochrome oxidase 1 (CO1) gene whereby the PCR products were sequenced and the retrived sequences matched with the above mentioned genera from the NCBI database. Phylogeny of southern African tabanid flies using CO1 gene sequences supported monophyly in Tabanidae when compared to other tabanid flies from the NCBI database. In addition, tabanid flies from the Afrotropic region were found to be genetically distinct from those found in the Nearctic and the Neotropical regions. This is probably due to influence of variable environmental factors in different geographical areas which are probably affecting genetic makeup of the flies.
Deoxyribonucleic acid extracted from South African Tabanus par and T. taeniola tested positive for the presence of Trypanosoma congolense and T. theileri whilst one member from T. par was positive for the presence of Trypanozoon species. Deoxyribonucleic acid extracted from Zambian tabanid flies tested positive for the presence of Besnoitia besnoiti, Babesia bigemina, Theileria parva and for Trypanozoon species at 1.27% (2/157), 5.73% (9/157), 30.11% (30/157) and 9.82% (14/157) respectively.
Analysis of gut microbes from the seven South African tabanid flies produced a total of 407 689 assembled sequences and a total of 505 operational taxonomic units (OTUs). The most abundant phylum was Proteobacteria (44.55%), followed by unclassified bacteria with 37.08%. The other important detected phyla included Tenericutes (8.91%), Firmicutes (7.33%) and Bacteroidetes (1.98%). Analysis of gut microbes associated with twelve tabanid flies from Zambia revealed 2 524 727 assembled sequences and 2 285 OTUs per fly species. A total of 12 phyla were recovered from the produced OTUs. The abundant bacterial phyla were Proteobacteria (57.81%), followed by Tenericutes with 22.67% and the least phyla detected included Planctomycetes, Gemmatimonadetes, WS3 as well as Chlamydiae. The Spiroplasma was the genus detected amongst all tabanid species and is suspected to be a mutual or commensal symbiont in the gut of tabanid flies. Furthermore, the following genera which has species of medical or veterinary or environmental importance were detected from the gut of tabanid flies by means of metagenomics analyses: Enterobacter, Serratia, Klebsiella, Shigella, Escherichia, Proteus, Providencia, Acinetobacter, Zymobacter, Vibrio, Comamonas, Pseudomonas, Brochothrix, Bacillus, Staphylococcus and Enterococcus. This is study has pioneered detection of bacterial genera of medical, veterinary and invironmental significance by metagenomics in tabanid flies.
This is the first report of detection of Besnoitia besnoiti, Babesia bigemina, Theileria parva and various trypanosome species by PCR from southern African tabanid flies. Additionally, it is for the first time gut microbes associated with tabanid flies are explored by metagenomic analysis. This study has demonstrated that there is a high abundance of different tabanid fly species in South Africa and Zambia. However, not much can be said regarding tabanid flies from Lesotho due to the fact that in the current study only 2 specimens were captured during a 3 months sampling period. Nonetheless, this study has not determined the vectorial capacity of tabanid flies for the detected protozoan parasites and bacteria. It has been reported that tabanid flies mechanically transmit some Trypanosoma species as well as bacterial species such as Anaplasma marginale, Bacillus anthracis and Listeria monocytogenes. Further studies to determine if tabanids are capable of transmitting tick-borne parasites such as Babesia species and Theileria species are required. Transmission of Besnoitia species by tabanid flies is not clarified, and their association with tabanid flies needs to be further explored. Whilst a lot of research and control strategies are focused on tsetse flies and ticks, it is evident that tabanid flies need to be considered for inclusion in such efforts as well. The findings obtained in this study open doors for future studies, particularly in identifying candidate microbes that can be used in the control of tabanid flies as well as in determining the actual role played by symbiotic microbes inside the tabanid flies||en_US