Tsetse fly evolution, genetics and the trypanosomiases - A review

Abstract

<p><p id="x-x-x-sp0065">This reviews work published since 2007. Relative efforts devoted to the agents of African trypanosomiasis and their <a href="https://www.sciencedirect.com/topics/immunology-and-microbiology/tsetse-fly" title="Learn more about Tsetse Fly from ScienceDirect's AI-generated Topic Pages">tsetse fly</a> vectors are given by the numbers of PubMed accessions. In the last 10 years PubMed citations number 3457 for <a href="https://www.sciencedirect.com/topics/immunology-and-microbiology/trypanosoma" title="Learn more about Trypanosoma from ScienceDirect's AI-generated Topic Pages">Trypanosoma</a> brucei and 769 for <em><a href="https://www.sciencedirect.com/topics/immunology-and-microbiology/glossina" title="Learn more about Glossina from ScienceDirect's AI-generated Topic Pages">Glossina</a></em>. The development of <a href="https://www.sciencedirect.com/topics/immunology-and-microbiology/simple-sequence-repeat" title="Learn more about Simple Sequence Repeat from ScienceDirect's AI-generated Topic Pages">simple sequence repeats</a> and <a href="https://www.sciencedirect.com/topics/immunology-and-microbiology/single-nucleotide-polymorphism" title="Learn more about Single Nucleotide Polymorphism from ScienceDirect's AI-generated Topic Pages">single nucleotide polymorphisms</a> afford much higher resolution of <em>Glossina</em> and <em>Trypanosoma</em> <a href="https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/population-structure" title="Learn more about Population Structure from ScienceDirect's AI-generated Topic Pages">population structures</a> than heretofore. Even greater resolution is offered by partial and <a href="https://www.sciencedirect.com/topics/immunology-and-microbiology/whole-genome-sequencing" title="Learn more about Whole Genome Sequencing from ScienceDirect's AI-generated Topic Pages">whole genome sequencing</a>. Reproduction in <em>T. brucei</em> sensu lato is principally clonal although <a href="https://www.sciencedirect.com/topics/immunology-and-microbiology/genetic-recombination" title="Learn more about Genetic Recombination from ScienceDirect's AI-generated Topic Pages">genetic recombination</a> in tsetse <a href="https://www.sciencedirect.com/topics/immunology-and-microbiology/salivary-gland" title="Learn more about Salivary Gland from ScienceDirect's AI-generated Topic Pages">salivary glands</a> has been demonstrated in <em>T. b. brucei</em> and <em>T. b.</em> rhodesiense but not in <em>T. b. gambiense</em>. <p id="x-x-x-sp0070">In the past decade most genetic attention was given to the chief human African trypanosomiasis vectors in subgenus <em>Nemorhina</em> e.g., <em>Glossina f. fuscipes, G. p. palpalis</em>, and <em>G. p. gambiense</em>. The chief interest in <em>Nemorhina</em> <a href="https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/population-genetics" title="Learn more about Population Genetics from ScienceDirect's AI-generated Topic Pages">population genetics</a> seemed to be finding vector populations sufficiently isolated to enable efficient and long-lasting suppression. To this end estimates were made of <a href="https://www.sciencedirect.com/topics/immunology-and-microbiology/gene-flow" title="Learn more about Gene Flow from ScienceDirect's AI-generated Topic Pages">gene flow</a>, derived from <em>F</em><em>ST</em>and its analogues, and <em>Ne</em>, the size of a hypothetical population equivalent to that under study. <a href="https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/genetic-drift" title="Learn more about Genetic Drift from ScienceDirect's AI-generated Topic Pages">Genetic drift</a> was greater, gene flow and <em>Ne</em> typically lesser in savannah inhabiting tsetse (subgenus <em>Glossina</em>) than in riverine forms (<em>Nemorhina</em>). Population stabilities were examined by sequential sampling and genotypic analysis of nuclear and <a href="https://www.sciencedirect.com/topics/immunology-and-microbiology/mitochondrial-genome" title="Learn more about Mitochondrial Genome from ScienceDirect's AI-generated Topic Pages">mitochondrial genomes</a> in both groups and found to be stable. <a href="https://www.sciencedirect.com/topics/immunology-and-microbiology/gene-frequency" title="Learn more about Gene Frequency from ScienceDirect's AI-generated Topic Pages">Gene frequencies</a> estimated in sequential samplings differed by drift and allowed estimates of effective population numbers that were greater for <em>Nemorhina</em> spp than <em>Glossina</em> spp. <p id="x-x-x-sp0075">Prospects are examined of genetic methods of <a href="https://www.sciencedirect.com/topics/medicine-and-dentistry/vector-control" title="Learn more about Vector Control from ScienceDirect's AI-generated Topic Pages">vector control</a>. The tsetse long generation time (<em>c.</em> 50 d) is a major <a href="https://www.sciencedirect.com/topics/medicine-and-dentistry/contraindication" title="Learn more about Contraindication from ScienceDirect's AI-generated Topic Pages">contraindication</a> to any suggested genetic method of tsetse population manipulation. Ecological and modelling research convincingly show that conventional methods of targeted <a href="https://www.sciencedirect.com/topics/medicine-and-dentistry/insecticide" title="Learn more about Insecticide from ScienceDirect's AI-generated Topic Pages">insecticide</a> applications and traps/targets can achieve cost-effective reduction in tsetse densities.</p>