Infections with Immunogenic Trypanosomes Reduce Tsetse Reproductive Fitness: Potential Impact of Different Parasite Strains on Vector Population Structure

The parasite Trypanosoma brucei rhodesiense and its insect vector Glossina morsitans morsitans were used to evaluate the effect of parasite clearance (resistance) as well as the cost of midgut infections on tsetse host fitness. Tsetse flies are viviparous and have a low reproductive capacity, giving birth to only 6–8 progeny during their lifetime. Thus, small perturbations to their reproductive fitness can have a major impact on population densities. We measured the fecundity (number of larval progeny deposited) and mortality in parasite-resistant tsetse females and untreated controls and found no differences. There was, however, a typanosome-specific impact on midgut infections. Infections with an immunogenic parasite line that resulted in prolonged activation of the tsetse immune system delayed intrauterine larval development resulting in the production of fewer progeny over the fly's lifetime. In contrast, parasitism with a second line that failed to activate the immune system did not impose a fecundity cost. Coinfections favored the establishment of the immunogenic parasites in the midgut. We show that a decrease in the synthesis of Glossina Milk gland protein (GmmMgp), a major female accessory gland protein associated with larvagenesis, likely contributed to the reproductive lag observed in infected flies. Mathematical analysis of our empirical results indicated that infection with the immunogenic trypanosomes reduced tsetse fecundity by 30% relative to infections with the non-immunogenic strain. We estimate that a moderate infection prevalence of about 26% with immunogenic parasites has the potential to reduce tsetse populations. Potential repercussions for vector population growth, parasite–host coevolution, and disease prevalence are discussed

SEQUENCE ANALYSIS OF INSECTICIDE RESISTANCE AND DETOXIFICATION RELATED GENES IN Spodoptera littoralis(LEPIDOPTERA: NOCTUIDAE)

The Egyptian cotton leaf worm, Spodoptera littoralis (Boisd. ) is a well-known asone of the most destructive agricultural lepidopterous pests. It is a true generalistspecies with a promiscuous feeding strategy which enables it to attack numerouseconomically important crops all year round including vegetables, ornamentalplants, and cotton. Recently, chemical control has been commonly used to suppresspopulations of S. littoralis; however, a very large number of insecticides have ledtothe emergence ofresistance. An extensive use of insecticides also has other sideeffects, including the elimination of non-targeted organisms, environmentaldamage and harm to human health. Genome-wide high-throughput technologieshelp developing resistance management strategies, especially identifying geneticmechanisms of resistance. The aim of the present study was to produce a de novotranscriptome for S. littoralis as a resource for current and future studies of thispest species by using next-generation sequencing. This resource was then used as areference for identifying genes by encoding the target sites of insecticides currentlyin use for Egyptian cotton leaf worm control. To achieve this, a cDNA library wassequenced using 454 FLX Titanium Sequencing on the Roche platform whichrevealed good coverage of genes encoding insecticide target sites anddetoxification enzymes using a manual annotation. Annotations of assembledsequences were carried out by BLASTx against NCBI non-redundant proteinsequence databases using the software Blast2GO. The genesencodingenzymesinvolvedin insecticide detoxification such as Acetylcholinesterase,Cytochrome p450, Glutathione S-transferase were characterized. Furthermore, aphylogenetic analyses based on three protein sequences were generated in order togive evolutionary insights into insecticide resistance gene families of S. littoralis

Detection of diflubenzuron and pyrethroid resistance mutations in Culex pipiens from Mugla, Turkey

Vontas, John/0000-0002-8704-2574WOS: 000525794700015PubMed: 31836282Chemical insecticides are the main tool for vector control worldwide with pyrethroids and the larvicide diflubenzuron (DFB) used extensively against the primary West Nile virus vector Culex pipiens. in this study we monitored the presence, frequency and geographical distribution of the Chitin synthase 1 gene mutations I1043L, I1043M associated with striking diflubenzuron resistance and the knock down resistance mutation L1014F associated with pyrehtroid resistance, in Cx. pipiens populations from Turkey. DFB resistance mutations I1043L, I1043M were found at high frequencies ranging from 15.7% to 37.5% and 25% to 52.7% in all study sites (first report for the presence of DFB resistant mutations, anywhere outside Italy). the L1014F pyrethroid resistance mutation was also present at relatively high frequencies, ranging from 40% to 50%. the high frequency of both DFB and pyrethroid resistance mutations are possibly associated with the intense use of these insecticides in agricultural and mosquito control applications in the region. Given the limited number of available insecticides for vector control these findings are of major importance for public health in Turkey and neighboring countries.Mugla Metropolitan Municipality; General Secretariat for Research and Technology (GSRT)Greek Ministry of Development-GSRT [532]; Hellenic Foundation for Research and Innovation (HFRI) [532]We thank Mugla Metropolitan Municipality for their support and for providing mosquito samples used in this study. E.A. F., was supported by the General Secretariat for Research and Technology (GSRT) and the Hellenic Foundation for Research and Innovation (HFRI) in the context of the action "1st Proclamation of Scholarships from ELIDEK for PhD Candidates" (Scholarship Code: 532)

Significance plot.

<p>The log2 fold change value of each gene is shown against its base mean value. Differentially expressed genes with statistically significant difference at 5% FDR are indicated by red coloring.</p

Summary statistics for <i>Tribolium castaneum</i> transcriptome sequencing analysis.

<p>Summary statistics for <i>Tribolium castaneum</i> transcriptome sequencing analysis.</p

Transcripts with significant differential expression upon LPS-challenge in adult beetles.

<p>Transcripts with significant differential expression upon LPS-challenge in adult beetles.</p

Comparison of RNA level estimation by our recent qRT-PCR analysis [12] and present transcriptome sequencing approach.

<p>Comparison of RNA level estimation by our recent qRT-PCR analysis <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0052004#pone.0052004-Altincicek1" target="_blank">[12]</a> and present transcriptome sequencing approach.</p

Correlation of gene expression levels of selected genes by both our recent qRT-PCR [<b>12</b>] and present RNASeq approach.

<p>The determined values of the expression levels of selected genes are shown as logN values. The values of both experiments were comparable and correlated with statistical significance (Pearson correlation, P, 0).</p

Infections with immunogenic trypanosomes reduce tsetse reproductive fitness: potential impact of different parasite strains on vector population structure.

The parasite Trypanosoma brucei rhodesiense and its insect vector Glossina morsitans morsitans were used to evaluate the effect of parasite clearance (resistance) as well as the cost of midgut infections on tsetse host fitness. Tsetse flies are viviparous and have a low reproductive capacity, giving birth to only 6-8 progeny during their lifetime. Thus, small perturbations to their reproductive fitness can have a major impact on population densities. We measured the fecundity (number of larval progeny deposited) and mortality in parasite-resistant tsetse females and untreated controls and found no differences. There was, however, a typanosome-specific impact on midgut infections. Infections with an immunogenic parasite line that resulted in prolonged activation of the tsetse immune system delayed intrauterine larval development resulting in the production of fewer progeny over the fly's lifetime. In contrast, parasitism with a second line that failed to activate the immune system did not impose a fecundity cost. Coinfections favored the establishment of the immunogenic parasites in the midgut. We show that a decrease in the synthesis of Glossina Milk gland protein (GmmMgp), a major female accessory gland protein associated with larvagenesis, likely contributed to the reproductive lag observed in infected flies. Mathematical analysis of our empirical results indicated that infection with the immunogenic trypanosomes reduced tsetse fecundity by 30% relative to infections with the non-immunogenic strain. We estimate that a moderate infection prevalence of about 26% with immunogenic parasites has the potential to reduce tsetse populations. Potential repercussions for vector population growth, parasite-host coevolution, and disease prevalence are discussed