Biology subjects

Frentiu, F. D.

Publications and source records attributed to Frentiu, F. D..

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↗

bioRxiv2020

Temperature alters gene expression in mosquitoes during arbovirus infection

Arthropod-borne viruses (arboviruses) such as dengue, Zika and chikungunya constitute a significant proportion of the global disease burden. The principal vector of these pathogens is the mosquito Aedes (Ae.) aegypti, and its ability to transmit virus to a human host is influenced by environmental factors such as temperature. However, exactly how ambient temperature influences virus replication within mosquitoes remains poorly elucidated, particularly at the molecular level. Here, we use chikungunya virus (CHIKV) as a model to understand how the host mosquito transcriptome responds to arbovirus infection under different ambient temperatures. We exposed CHIKV-infected mosquitoes to 18 {degrees}C, 28 {degrees}C and 32 {degrees}C, and found higher temperature correlated with higher virus replication levels, particularly at early time points post-infection. Lower ambient temperatures resulted in reduced virus replication levels. Using RNAseq, we found that temperature significantly altered gene expression levels in mosquitoes, particularly components of the immune response. The highest number of significantly differentially expressed genes in response to CHIKV was observed at 28 {degrees}C, with a markedly more muted effect observed at either lower (18 {degrees}C) or higher (32 {degrees}C) temperatures. At the higher temperature, the expression of many classical immune genes, including Dicer-2 in the RNAi pathway, was not substantially altered in response to CHIKV. Upregulation of Toll, IMD and JAK-STAT pathways was only observed at 28 {degrees}C. Time post infection also led to substantially different gene expression profiles, and this effect varied depending upon the which temperature mosquitoes were exposed to. Taken together, our data indicate temperature significantly modulates mosquito gene expression in response to infection, potentially leading to impairment of immune defences at higher ambient temperatures.

microbiology↗

bioRxiv2019

Spatial and epidemiologic features of dengue in Sabah, Malaysia

In South East Asia, dengue epidemics have increased in size and geographical distribution in recent years. Most studies investigating dengue transmission and control have had an urban focus, while less consideration is currently given to rural settings, or where urban and rural areas overlap. We examined the spatiotemporal distribution and epidemiological characteristics of reported dengue cases in the predominantly rural state of Sabah, in Malaysian Borneo - an area where sylvatic and urban circulation of pathogens are known to intersect. We found that annual dengue incidence rates were spatially variable over the 7-year study period from 2010-2016 (state-wide mean annual incidence of 21 cases/100,000 people; range 5-42/100,000), but were highest in rural localities in the western districts of the state (Kuala Penyu, Nabawan, Tenom and Kota Marudu). The eastern districts exhibited lower overall dengue rates; however, we noted a concentration of severe (haemorrhagic) dengue cases (44%) in Sandakan and Tawau districts. Dengue incidence was slightly higher for males than females, and was significantly higher for both genders aged between 10 and 29 years (24/100,000; p=0.029). The largest ever recorded outbreaks occurred during 2015-2016, with the vector Aedes albopictus found to be most prevalent in both urban and rural households (House Index of 64%), compared with Ae. Aegypti (15%). These findings suggest that dengue outbreaks in Sabah are driven by the sporadic expansion of dengue virus in both urban and rural settings. This may require tailoring of preventative strategies to suit different transmission ecologies across Sabah. Further studies to better understand the drivers of dengue in Sabah may aid dengue control efforts in Malaysia, and more broadly in South East Asia.\n\nAuthor summaryIn order to combat the rising regional incidence of dengue in South East Asia, the drivers of transmission must be better characterised across different environmental settings. We conducted the first retrospective analysis of dengue epidemiology in the predominantly rural state of Sabah, Malaysia, where both urban and sylvatic transmission cycles exist. Human notification data over a 7-year period were reviewed and spatiotemporal and demographic risk factors identified. We found: O_LIUrban habitats and population density are not the only determinants mediating the spread of epidemic dengue in Sabah. Case from both urban and rural localities contributed equally to dengue outbreaks.\nC_LIO_LIHuman demographic risk factors included being aged between 10 and 29 years, and being male.\nC_LIO_LIHigh incidence areas for dengue do not predict the occurrence of severe dengue. Severe dengue was largely localised to lower incidence districts in the east of the state.\nC_LIO_LIThe sole presence of Aedes albopictus in and around the majority of urban and rural case households suggests that this vector may play a major role in facilitating outbreaks.\nC_LI\n\nA complex interplay of risk factors likely mediates dengue transmission in Sabah, influenced by both regional climate trends and localised human and ecological influences. This study emphasises that the increasing spread of dengue in urban South East Asia is also mirrored in more rural areas, and suggests a need for control strategies that address both urban and rural dengue risk.

epidemiology↗