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Parasites & Vectors Jun 2023Chagas disease remains a persistent vector-borne neglected tropical disease throughout the Americas and threatens both human and animal health. Diverse control methods...
BACKGROUND
Chagas disease remains a persistent vector-borne neglected tropical disease throughout the Americas and threatens both human and animal health. Diverse control methods have been used to target triatomine vector populations, with household insecticides being the most common. As an alternative to environmental sprays, host-targeted systemic insecticides (or endectocides) allow for application of chemicals to vertebrate hosts, resulting in toxic blood meals for arthropods (xenointoxication). In this study, we evaluated three systemic insecticide products for their ability to kill triatomines.
METHODS
Chickens were fed the insecticides orally, following which triatomines were allowed to feed on the treated chickens. The insecticide products tested included: Safe-Guard® Aquasol (fenbendazole), Ivomec® Pour-On (ivermectin) and Bravecto® (fluralaner). Triatoma gerstaeckeri nymphs were allowed to feed on insecticide-live birds at 0, 3, 7, 14, 28 and 56 days post-treatment. The survival and feeding status of the T. gerstaeckeri insects were recorded and analyzed using Kaplan-Meier curves and logistic regression.
RESULTS
Feeding on fluralaner-treated chickens resulted 50-100% mortality in T. gerstaeckeri over the first 14 days post-treatment but not later; in contrast, all insects that fed on fenbendazole- and ivermectin-treated chickens survived. Liquid chromatography tandem mass spectrometry (LC-QQQ) analysis, used to detect the concentration of fluralaner and fenbendazole in chicken plasma, revealed the presence of fluralaner in plasma at 3, 7, and 14 days post-treatment but not later, with the highest concentrations found at 3 and 7 days post-treatment. However, fenbendazole concentration was below the limit of detection at all time points.
CONCLUSIONS
Xenointoxication using fluralaner in poultry is a potential new tool for integrated vector control to reduce risk of Chagas disease.
Topics: Animals; Humans; Triatoma; Insecticides; Chickens; Ivermectin; Fenbendazole; Insect Vectors; Chagas Disease
PubMed: 37268980
DOI: 10.1186/s13071-023-05805-1 -
PLoS Neglected Tropical Diseases Jun 2023The high reproductive rates of insects contribute significantly to their ability to act as vectors of a variety of vector-borne diseases. Therefore, it is strategically...
Silencing of the 20S proteasomal subunit-α6 triggers full oogenesis arrest and increased mRNA levels of the selective autophagy adaptor protein p62/SQSTM1 in the ovary of the vector Rhodnius prolixus.
The high reproductive rates of insects contribute significantly to their ability to act as vectors of a variety of vector-borne diseases. Therefore, it is strategically critical to find molecular targets with biotechnological potential through the functional study of genes essential for insect reproduction. The ubiquitin-proteasome system is a vital degradative pathway that contributes to the maintenance of regular eukaryotic cell proteostasis. This mechanism involves the action of enzymes to covalently link ubiquitin to proteins that are meant to be delivered to the 26S proteasome and broken down. The 26S proteasome is a large protease complex (including the 20S and 19S subcomplexes) that binds, deubiquitylates, unfolds, and degrades its substrates. Here, we used bioinformatics to identify the genes that encode the seven α and β subunits of the 20S proteasome in the genome of R. prolixus and learned that those transcripts are accumulated into mature oocytes. To access proteasome function during oogenesis, we conducted RNAi functional tests employing one of the 20S proteasome subunits (Prosα6) as a tool to suppress 20S proteasomal activity. We found that Prosα6 silencing resulted in no changes in TAG buildup in the fat body and unaffected availability of yolk proteins in the hemolymph of vitellogenic females. Despite this, the silencing of Prosα6 culminated in the impairment of oocyte maturation at the early stages of oogenesis. Overall, we discovered that proteasome activity is especially important for the signals that initiate oogenesis in R. prolixus and discuss in what manner further investigations on the regulation of proteasome assembly and activity might contribute to the unraveling of oogenesis molecular mechanisms and oocyte maturation in this vector.
Topics: Animals; Female; Proteasome Endopeptidase Complex; Ovary; Sequestosome-1 Protein; Rhodnius; Oogenesis; Adaptor Proteins, Signal Transducing; Autophagy; Ubiquitins
PubMed: 37267415
DOI: 10.1371/journal.pntd.0011380 -
Tropical Medicine and Infectious Disease Apr 2023Currently, there are 158 valid species of triatomines, all of which are potential vectors of , the etiological agent of Chagas disease. The correct taxonomic...
Currently, there are 158 valid species of triatomines, all of which are potential vectors of , the etiological agent of Chagas disease. The correct taxonomic identification of triatomines is essential since each species hos a different epidemiological importance. The aim of the study is to compare five species of South American . Here we present a comparative study of terminal abdominal segments in females by scanning electron microscopy (SEM) of the species , , var. , , and . The results showed diagnostic characters for the studied species. The dorsal view featured more valuable characters, with seven informative characters. Similarities were observed among , var. , and , and between and , correlating with previous studies. Thus, female genital characters proved to be reliable and useful in the diagnosis of the species studied here; additional studies, along with other sets of behavioral, morphological, and molecular data, helped to reinforce the hypotheses found here.
PubMed: 37235288
DOI: 10.3390/tropicalmed8050240 -
ZooKeys 2023, (Hemiptera, Heteroptera, Reduviidae, Harpactorinae, Harpactorini) is described based on male and female specimens from Brazil. Photographs and comments about the...
, (Hemiptera, Heteroptera, Reduviidae, Harpactorinae, Harpactorini) is described based on male and female specimens from Brazil. Photographs and comments about the syntypes of Burmeister, 1835, Stål, 1872, Burmeister, 1838 and (Fabricius, 1803) are presented. The intra-specific variability and sexual dimorphic characteristics among specimens of are recorded. General characteristics of Spinola, 1837, Stål, 1866, and Gil-Santana, 2015, which seem to be closer genera, are compared, including those of the male genitalia of some species. A key to the species of Burmeister, 1835, and an updated key to Neotropical wasp-mimicking Harpactorini genera are provided.
PubMed: 37235068
DOI: 10.3897/zookeys.1152.96058 -
Insects May 2023Triatominae, the only blood-sucking subfamily in Reduviidae, are the vectors of Chagas disease. The majority of them are distributed in the Americas, while the diversity...
Triatominae, the only blood-sucking subfamily in Reduviidae, are the vectors of Chagas disease. The majority of them are distributed in the Americas, while the diversity in China has been underestimated, as only two species have been recorded. Here, we describe two new species from China, Zhao & Cai sp. nov. and . Zhao & Cai sp. nov., and provide a redescription of Hsiao, 1965, along with remarks on (De Geer, 1773). To facilitate the identification, we include photos, especially of genitalia, as well as a distribution map and a key to Chinese triatomines. We calculated the pairwise genetic distances between 23 species, which further supported the validity of these new species. We anticipate that our taxonomic review will be useful for identifying Chinese Triatominae.
PubMed: 37233078
DOI: 10.3390/insects14050450 -
Brazilian Journal of Biology = Revista... 2023Rhodnius neglectus is a wild triatomine, vector of the protozoan Trypanosoma cruzi, which causes Chagas' disease, and feeds on the blood of small mammals, being...
Rhodnius neglectus is a wild triatomine, vector of the protozoan Trypanosoma cruzi, which causes Chagas' disease, and feeds on the blood of small mammals, being essential for its growth and reproduction. Accessory glands of the female reproductive tract are important in insect reproduction, but their anatomy and histology in R. neglectus are poorly studied. The aim of this work was to describe the histology and histochemistry of the accessory gland of the female reproductive tract of R. neglectus. The reproductive tract of five females of R. neglectus was dissected and the accessory glands transferred to Zamboni's fixative solution, dehydrated in a crescent series of ethanol, embedded in historesin, sectioned at 2 µm thick, stained with toluidine blue for histological analysis or mercury bromophenol blue for detection of total proteins. The accessory gland R. neglectus is tubular, without branches, opening in the dorsal region of the vagina and differing along its length in proximal and distal regions. In the proximal region, the gland is lined by the cuticle with a layer of columnar cells associated with muscle fibers. In the distal region of the gland, the epithelium has spherical secretory cells with terminal apparatus and conducting canaliculi opening in the lumen through pores in the cuticle. Proteins were identified in the gland lumen, terminal apparatus, nucleus and cytoplasm of secretory cells. The histology of the R. neglectus gland is similar to that found in other species of this genus, but with variations in the shape and size of its distal region.
Topics: Animals; Female; Rhodnius; Insect Vectors; Chagas Disease; Trypanosoma cruzi; Reproduction; Mammals
PubMed: 37194827
DOI: 10.1590/1519-6984.271913 -
The American Journal of Tropical... Jun 2023Oral transmission from the consumption of processed food with triatomines and/or their feces infected with Trypanosoma cruzi prevails among recent cases of Chagas...
Oral transmission from the consumption of processed food with triatomines and/or their feces infected with Trypanosoma cruzi prevails among recent cases of Chagas disease in Brazil. In Paraíba, a state of the Brazilian northeast, there was an outbreak caused by the consumption of sugarcane juice that resulted in 26 cases of infection and one death. Until now, 10 species of triatomines have been reported in this Brazilian state. Thus, we developed a dichotomous key to assist in the correct identification of Paraíba triatomines based on cytogenetic data. The dichotomous key allowed the differentiation of all the species in this state. Although the purpose of CytoKeys is not to replace dichotomous keys based on morphological data, the use of these complementary keys can help to solve taxonomic problems, preventing identification errors, especially between similar species such as Triatoma brasiliensis and Triatoma petrocchiae, both present in the Brazilian northeast.
Topics: Humans; Animals; Triatominae; Brazil; Insect Vectors; Chagas Disease; Triatoma; Trypanosoma cruzi; Disease Outbreaks; Cytogenetic Analysis
PubMed: 37160280
DOI: 10.4269/ajtmh.22-0697 -
PLoS Computational Biology May 2023Chagas disease, a vector-borne parasitic disease caused by Trypanosoma cruzi, affects millions in the Americas. Dogs are important reservoirs of the parasite. Under...
BACKGROUND
Chagas disease, a vector-borne parasitic disease caused by Trypanosoma cruzi, affects millions in the Americas. Dogs are important reservoirs of the parasite. Under laboratory conditions, canine treatment with the systemic insecticide fluralaner demonstrated efficacy in killing Triatoma infestans and T. brasiliensis, T. cruzi vectors, when they feed on dogs. This form of pest control is called xenointoxication. However, T. cruzi can also be transmitted orally when mammals ingest infected bugs, so there is potential for dogs to become infected upon consuming infected bugs killed by the treatment. Xenointoxication thereby has two contrasting effects on dogs: decreasing the number of insects feeding on the dogs but increasing opportunities for exposure to T. cruzi via oral transmission to dogs ingesting infected insects.
OBJECTIVE
Examine the potential for increased infection rates of T. cruzi in dogs following xenointoxication.
DESIGN/METHODS
We built a deterministic mathematical model, based on the Ross-MacDonald malaria model, to investigate the net effect of fluralaner treatment on the prevalence of T. cruzi infection in dogs in different epidemiologic scenarios. We drew upon published data on the change in percentage of bugs killed that fed on treated dogs over days post treatment. Parameters were adjusted to mimic three scenarios of T. cruzi transmission: high and low disease prevalence and domestic vectors, and low disease prevalence and sylvatic vectors.
RESULTS
In regions with high endemic disease prevalence in dogs and domestic vectors, prevalence of infected dogs initially increases but subsequently declines before eventually rising back to the initial equilibrium following one fluralaner treatment. In regions of low prevalence and domestic or sylvatic vectors, however, treatment seems to be detrimental. In these regions our models suggest a potential for a rise in dog prevalence, due to oral transmission from dead infected bugs.
CONCLUSION
Xenointoxication could be a beneficial and novel One Health intervention in regions with high prevalence of T. cruzi and domestic vectors. In regions with low prevalence and domestic or sylvatic vectors, there is potential harm. Field trials should be carefully designed to closely follow treated dogs and include early stopping rules if incidence among treated dogs exceeds that of controls.
Topics: Animals; Dogs; Trypanosoma cruzi; Insect Vectors; Chagas Disease; Triatoma; Insecticides; Mammals
PubMed: 37155680
DOI: 10.1371/journal.pcbi.1011115 -
Heliyon May 2023has been previously reported in the Brazilian states of Amazonas and Pará, as well as in French Guiana. However, this is the first recorded presence of this species in...
has been previously reported in the Brazilian states of Amazonas and Pará, as well as in French Guiana. However, this is the first recorded presence of this species in Amapá, which is situated in the northern region of Brazil. The specimen was collected from a house in the rural area of the municipality of Porto Grande. Other triatomines, such as and were also found in the same locality in different houses. These species are vectors of which causes Chagas disease. Therefore, this report may contribute to understanding transmission in the state of Amapá, where new infections and outbreaks of Chagas disease have been recorded.
PubMed: 37153416
DOI: 10.1016/j.heliyon.2023.e15204 -
Evolutionary Applications Apr 2023Insect speciation is among the most fascinating topics in evolutionary biology; however, its underlying mechanisms remain unclear. Allopatric speciation represents one...
Insect speciation is among the most fascinating topics in evolutionary biology; however, its underlying mechanisms remain unclear. Allopatric speciation represents one of the major types of speciation and is believed to have frequently occurred during glaciation periods, when climatic oscillation may have caused suitable habitats to be fragmented repeatedly, creating geographical isolation among populations. However, supporting evidence for allopatric speciation of insects in East Asia during the Pleistocene glaciation remains lacking. We aim to investigate the effect of climatic oscillation during the Pleistocene glaciation on the diversification pattern and evolutionary history of hemipteran insects and to test the hypothesis of Pleistocene species stability using spinous assassin bugs (Hemiptera: Reduviidae), a small genus widely distributed in southern China but was later found to have cryptic species diversity. Here, using the whole mitochondrial genome (mitogenome) and nuclear ribosomal RNA genes, we investigated both interspecific and intraspecific diversification patterns of spinous assassin bugs. Approximate Bayesian computation, ecological niche modeling, and demographic history analyses were also applied to understand the diversification process and driven factors. Our data suggest that the five species of are highly diverged, despite three of them currently being cryptic. Speciation occurred during the Pleistocene when suitable distribution areas were possibly fragmented. Six phylogeographic groups in the type species were identified, among which two groups underwent expansion during the early Last Glacial Period and after Last Glacier Maximum. Our analyses suggest that this genus may have experienced climate-driven habitat fragmentation and postglacial expansion in the Pleistocene, promoting allopatric speciation and intraspecific diversification. Our results reveal underestimated species diversity in a small insect group and illustrate a remarkable example of allopatric speciation of insects in East Asia promoted by Pleistocene climatic oscillations. These findings provide important insights into the speciation processes and aid the conservation of insect species diversity.
PubMed: 37124089
DOI: 10.1111/eva.13543