CURRENT STATUS OF METATRANSCRIPTOMIC AND RELATED STUDIES IN HEMATOPHAGOUS DISEASE-TRANSMITTING VECTORS

The incidence of numerous vector-borne diseases (VBDs) has recently increased alarmingly due to various widespread factors, including unplanned urbanization, greater human mobility, environmental changes, vector resistance to insecticides, and evolving pathogens. In this context, the World Health Organization (WHO) has repositioned effective and sustainable vector control as a key approach to prevent and eliminate VBDs. It has been shown that the microbiome influences development, nutrition, and pathogen defense in disease-transmitting vectors such as mosquitoes, sandflies, tsetse flies, triatomine bugs, and ticks. Consequently, understanding the endogenous regulation of vector biology can aid in developing effective approaches for vector control. In this respect, a metatranscriptomic approach analyzes all the expressed RNAs in an environmental sample (meta-RNAs) and can thus reveal how the metabolic activities of the microbiome influence vector biology. This review includes an extensive analysis of available literature on microbial and viral studies for some of the major hematophagous disease-transmitting arthropods, with a focus on studies that used next generation sequencing (NGS) approaches. Since a consensus terminology for these “meta-sequencing analyses” has not yet been established, a definition of these terms is presented here to provide the framework for systematically sorting the available information for each of the VBDs analyzed here to single out metatranscriptomic analyses. Finally, key gaps in knowledge were identified for some of these hematophagous disease-transmitting arthropods which will prove very useful for driving future studies.