Biology subjects

Capelli, G.

Publications and source records attributed to Capelli, G..

3 recordsLinked to original sources

bioRxiv2022

Investigation on key aspects of mating biology in the mosquito Aedes koreicus

Aedes koreicus is a mosquito (Diptera: Culicidae) from Northeast Asia with a rapidly expanding presence outside its original native range. Over the years the species has been discovered in several new countries, either spreading after first introduction or remaining localised to limited areas. Notably, recent studies have demonstrated the ability of the species to transmit zoonotic parasites and viruses both in the field and in laboratory settings. Combined with its invasive potential, the possible role of Ae. koreicus in pathogen transmission highlights the public health risks of its invasion. In this study, we used a recently established population from Italy to investigate aspects of biology that influence reproductive success in Ae. koreicus: autogeny, mating behaviour, mating disruption by the sympatric invasive species Aedes albopictus, and the presence of the endosymbiont Wolbachia pipientis. Our laboratory population did not exhibit autogenic behaviour and required a blood meal to complete its ovarian cycle. When we exposed Ae. koreicus females to males of Ae. albopictus, we observed repeated attempts at insemination and an aggressive, disruptive mating behaviour initiated by males. Despite this, no sperm was identified in Ae. koreicus spermathecae. Wolbachia was not detected in this Ae. koreicus population and therefore had no effect on Ae. koreicus reproduction.

ecology↗

bioRxiv2021

A highly endemic area of Echinococcus multilocula is identified through a comparative re-assessment of prevalence in red fox (Vulpes vulpes), Alto Adige (Italy: 2019-2020)

BackgroundSurveillance of E. multilocularis at the edge of its range is hindered by fragmented distributional patterns and low prevalence and burden in definitive hosts. Thus, tests with adequate levels of sensitivity are especially important for discriminating between infected and non-infected areas. AimWe reassessed the prevalence of E. multilocularis at the southern border of its distribution in Alto Adige (Italy), to improve surveillance in wildlife and provide more accurate estimates of exposure risk. MethodsWe compared results from the diagnostic test currently implemented for surveillance (based on Coproscopy+Multiplex PCR - CMPCR), against a real-time quantitative PCR (qPCR) for 235 fox faeces collected in 2019-2020. The performances of the two tests were estimated using a scraping technique (SFCT) as the gold standard applied to the small intestines of a subsample (n=123) of the same hosts. True prevalence was calculated and sample size required by each faecal test for the detection of the parasite was then estimated. ResultsTrue prevalence of E. multilocularis in foxes (14.3%) was definitely higher than reported in the last decade (never >5% from 2012 to 2018). The qPCR also had a higher sensitivity (83%) compared to CMPCR (21%). Agreement with the gold standard was far higher for qPCR (0.816) than CMPCR (0.298) as well, determining a smaller sample size required to detect the disease. ConclusionsAlto Adige should be considered a highly endemic area. Surveillance at the edges of E. multilocularis distribution should adopt qPCR diagnostics on definitive hosts on a small geographic scale. AUTHOR SUMMARYEchinococcus multilocularis is an intestinal flatworm, whose adult stage in Europe is harboured mainly by the red fox (Vulpes vulpes), which spreads parasites eggs by faeces. This parasite is the agent of a severe and potentially lethal zoonosis, the alveolar echinococcosis, affecting humans after accidental ingestion of parasites eggs. In the Italian Alpine area, which represents the southernmost border of E. multilocularis European range, surveillance is hindered by a fragmented distributional pattern, where presence in foxes has been consistently reported only in few isolated foci in Alto Adige (Bolzano province - Italy) of low prevalence. In order to improve the efficiency of monitoring efforts, we tested the performances of two diagnostic protocols on fox faeces (sedimentation, filtration, counting technique followed by standard PCR, and whole stool real-time PCR) against a benchmark technique on fox intestines (scraping, filtration, counting technique - considered as the gold standard). This allowed not only to determine qPCR as a far more sensitive and sample-efficient diagnostic tool for E. multilocularis detection in marginally affected areas, but also to re-assess its prevalence in Alto Adige, which should be considered a highly endemic area. Consequent actions in the field and modifications in the surveillance strategy should be therefore considered.

molecular biology↗

bioRxiv2020

Phylogenomics reveals that Asaia symbionts from insects underwent convergent genome reduction, preserving an insecticide-degrading gene

The mosquito microbiota is composed by several lineages of microorganisms whose ecological roles and evolutionary histories have yet to be investigated in depth. Among these microorganisms, Asaia bacteria play a prominent role, given its abundance in the gut, reproductive organs and salivary glands of different mosquito species, while its presence has also been reported in several other insects. Notably, Asaia has great potential as a tool for the control of mosquito-borne diseases. Here, we present a wide phylogenomic analysis of Asaia strains isolated from different species of mosquito vectors and from different populations of the Mediterranean fruit fly (medfly) Ceratitis capitata, an insect pest of worldwide economic importance. We show that phylogenetically distant lineages of Asaia experienced independent genome reductions, despite following a common pattern, characterized by the early loss of genes involved in genome stability. This result highlights the role of specific metabolic pathways in the symbiotic relationship between Asaia and the insect host. Finally, we discovered that all but one of the Asaia strains included in the study possess the pyrethroid hydrolase gene. Phylogenetic analysis revealed that this gene is ancestral in Asaia, strongly suggesting that it played a role in the establishment of the symbiotic association between these bacteria and the mosquito hosts. We propose that this gene from the symbiont contributed to initial pyrethroid resistance in insects harboring Asaia, also considering the widespread production of pyrethrins by several plants. ImportanceWe have studied genome reduction within several strains of the insect symbiont Asaia, isolated from different species/strains of mosquito and medfly. Phylogenetically distant strains of Asaia, despite following a common pattern involving the loss of genes related to genome stability, have undergone independent genome reductions, highlighting the peculiar role of specific metabolic pathways in the symbiotic relationship between Asaia and its host. We also show that the pyrethroid hydrolase gene is present in all the Asaia strains isolated except for the South American malaria vector An. darlingi, for which resistance to pyrethroids has never been reported, suggesting a possible involvement of Asaia in determining the resistance to insecticides.

microbiology↗