Abstract
Simple SummaryThe ability to identify the source of vertebrate blood in mosquitoes, ticks, and other blood-feeding arthropod vectors greatly enhances our knowledge of how vector-borne pathogens are spread. The source of the bloodmeal is identified by analyzing the remnants of blood remaining in the arthropod at the time of capture, though this is often fraught with challenges. This review provides a roadmap and guide for those considering modern techniques for arthropod bloodmeal identification with a focus on progress made in the field over the past decade. We highlight genome regions that can be used to identify the vertebrate source of arthropod bloodmeals as well as technological advances made in other fields that have introduced innovative new ways to identify vertebrate meal source based on unique properties of the DNA sequence, protein signatures, or residual molecules present in the blood. Additionally, engineering progress in miniaturization has led to a number of field-deployable technologies that bring the laboratory directly to the arthropods at the site of collection. Although many of these advancements have helped to address the technical challenges of the past, the challenge of successfully analyzing degraded DNA in bloodmeals remains to be solved.Understanding vertebrate–vector interactions is vitally important for understanding the transmission dynamics of arthropod-vectored pathogens and depends on the ability to accurately identify the vertebrate source of blood-engorged arthropods in field collections using molecular methods. A decade ago, molecular techniques being applied to arthropod blood meal identification were thoroughly reviewed, but there have been significant advancements in the techniques and technologies available since that time. This review highlights the available diagnostic markers in mitochondrial and nuclear DNA and discusses their benefits and shortcomings for use in molecular identification assays. Advances in real-time PCR, high resolution melting analysis, digital PCR, next generation sequencing, microsphere assays, mass spectrometry, and stable isotope analysis each offer novel approaches and advantages to bloodmeal analysis that have gained traction in the field. New, field-forward technologies and platforms have also come into use that offer promising solutions for point-of-care and remote field deployment for rapid bloodmeal source identification. Some of the lessons learned over the last decade, particularly in the fields of DNA barcoding and sequence analysis, are discussed. Though many advancements have been made, technical challenges remain concerning the prevention of sample degradation both by the arthropod before the sample has been obtained and during storage. This review provides a roadmap and guide for those considering modern techniques for arthropod bloodmeal identification and reviews how advances in molecular technology over the past decade have been applied in this unique biomedical context.
Highlights
A quarter of pathogen outbreaks affecting humans in the 20th century were spread by hematophagous arthropod vectors, showcasing the important role of vector surveillance, ecological research, and vector control in public health practice [1]
While utilized less frequently than Mitochondrial DNA (mtDNA) for vertebrates, Ribosomal DNA (rDNA) can be a powerful tool for identifying bloodmeal source. rDNA is present in the genome of all eukaryotes in a series of tandem repeats consisting of two rapidly evolving internal transcribed spacers (ITS) sandwiched between extremely conserved coding sequences for 18S, 5.8S, and 28S
Proof of concept experiments were able to separate human- or chicken-fed mosquitoes one full week after ingestion of the bloodmeal [145], and gerbil- or rabbit-fed ticks after molting [208]. This methodology was applied to wild caught ticks [146,209], fleas [210], and mosquitoes [211] with mixed results. While this technique is theoretically capable of determining meal source long after digestion of the bloodmeal giving it great potential for use across arthropod species, specificity and species resolving power remain a challenge
Summary
A quarter of pathogen outbreaks affecting humans in the 20th century were spread by hematophagous arthropod vectors, showcasing the important role of vector surveillance, ecological research, and vector control in public health practice [1]. Molecular identification of arthropod bloodmeal sources has become an increasingly important tool as the global public health community seeks to further understand the transmission dynamics of arthropod-vectored pathogens [2]. 1980s, were limited in their ability to identify vertebrate hosts to only those species for which anti-sera had been generated. These tests had low species-specificity, restricting identification to order, family, or genus [3,4]. This review highlights molecular advancements in bloodmeal identification made over the past decade since previously reviewed [2], and briefly discusses traditional methods that remain useful for cost effective analysis
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