Gordana Rašić

Queensland Institute of Medical Research | QIMR · Department of Population Health

Genetic markers are widely used to understand the biology and population dynamics of disease vectors, but often markers are limited in the resolution they provide. In particular, the delineation of population structure, fine scale movement and patterns of relatedness are often obscured unless numerous markers are available. To address this issue in...

Female Aedes aegypti mosquitoes infect more than 400 million people each year with dangerous viral pathogens including dengue, yellow fever, Zika and chikungunya. Progress in understanding the biology of mosquitoes and developing the tools to fight them has been slowed by the lack of a high-quality genome assembly. Here we combine diverse technolog...

Background: Hundreds of millions of people get a mosquito-borne disease every year and nearly one million die. Transmission of these infections is primarily tackled through the control of mosquito vectors. The accurate quantification of mosquito dispersal is critical for the design and optimization of vector control programs, yet the measurement o...

Domesticating Zika virus Why hasn't Zika virus (ZIKV) disease caused as much devastation in Africa, its continent of origin, as it has in the Americas? Outside of Africa, this flavivirus is transmitted by a ubiquitous mosquito subspecies, Aedes aegypti aegypti , which emerged from the African forerunner subspecies A. aegypti formosus and acquired a...

Gene drive organisms (GDOs), whose genomes have been genetically engineered to spread a desired allele through a population, have the potential to transform the way societies address a wide range of daunting public health and environmental challenges. The development, testing, and release of GDOs, however, are complex and often controversial. A key...

Close-kin mark-recapture (CKMR) methods have recently been used to infer demographic parameters such as census population size and survival for fish of interest to fisheries and conservation. These methods have advantages over traditional mark-recapture methods as the mark is genetic, removing the need for physical marking and recapturing that may...

Rising temperatures and increasing temperature variability are impacting the range and prevalence of mosquito-borne disease. A promising biocontrol technology replaces wild mosquitoes with those carrying the virus-blocking Wolbachia bacterium. Laboratory and field observations show that the most widely used strain, wMel, is adversely affected by he...

Biological control of mosquito vectors using the endosymbiotic bacteria Wolbachia is an emerging strategy for the management of human arboviral diseases. We recently described the development of a strain of Aedes aegypti infected with the Wolbachia strain wAlbB (referred to as the wAlbB2-F4 strain) through simple backcrossing of wild type Australia...

Background An optimal starting point for relating genome function to organismal biology is a high-quality nuclear genome assembly, and long-read sequencing is revolutionizing the production of this genomic resource in insects. Despite this, nuclear genome assemblies have been under-represented for agricultural insect pests, particularly from the or...

Biological control of mosquito vectors using the insect-specific bacteria Wolbachia is an emerging strategy for the management of human arboviral diseases. We recently described the development of a strain of Ae. aegypti infected with the Wolbachia strain wAlbB (referred to as the wAlbB2-F4 strain) through simple backcrossing of wild type Australia...

Close-kin mark-recapture (CKMR) methods have recently been used to infer demographic parameters such as census population size and survival for fish of interest to fisheries and conservation. These methods have advantages over traditional mark-recapture methods as the mark is genetic, removing the need for physical marking and recapturing that may...

The drivers and patterns of zoonotic virus emergence in the human population are poorly understood. The mosquito Aedes aegypti is a major arbovirus vector native to Africa that invaded most of the world's tropical belt over the past four centuries, after the evolution of a "domestic" form that specialized in biting humans and breeding in water stor...

As gene drive mosquito projects advance from contained laboratory testing to semi-field testing and small-scale field trials, there is a need to assess monitoring requirements to: i) assist with the effective introduction of the gene drive system at field sites, and ii) detect unintended spread of gene drive mosquitoes beyond trial sites, or resist...

Significance With over 40% of humans at risk from mosquito-borne diseases such as dengue, yellow fever, chikungunya, and Zika, the development of environmentally friendly mosquito-control tools is critical. The release of reproductively incompatible male mosquitoes carrying a Wolbachia bacterium can drive mating events that kill the eggs. Through r...

Background An optimal starting point for relating genome function to organismal biology is a high-quality nuclear genome assembly, and long-read sequencing is revolutionizing the production of this genomic resource in insects. Despite this, nuclear genome assemblies have been under-represented for agricultural insect pests, particularly from the or...

A rare example of a successful long-term elimination of the mosquito Aedes aegypti is in Brisbane, Queensland, where the legislatively-enforced removal of rainwater tanks drove its disappearance by the mid-1950s. However, a decade-long drought led to the mass installation of rainwater tanks throughout the region, re-introducing critical breeding si...

Background: The development of insecticide resistance in mosquitoes can have pleiotropic effects on key behaviours such as mating competition and host-location. Documenting these effects is crucial for understanding the dynamics and costs of insecticide resistance and may give researchers an evidence base for promoting vector control programs that...

Background The coconut rhinoceros beetle (CRB, Oryctes rhinoceros ) is a severe and invasive pest of coconut and other palms throughout Asia and the Pacific. The biocontrol agent, Oryctes rhinoceros nudivirus (OrNV), has successfully suppressed O. rhinoceros populations for decades but new CRB invasions started appearing after 2007. A single-SNP va...

Background Effective vector control measures are essential in a world where many mosquito-borne diseases have no vaccines or drug therapies available. Insecticidal tools remain the mainstay of most vector-borne disease management programmes, although their use for both agricultural and public health purposes has resulted in selection for resistance...

The discovery of CRISPR-based gene editing and its application to homing-based gene drive systems has been greeted with excitement, for its potential to control mosquito-borne diseases on a wide scale, and concern, for the invasiveness and potential irreversibility of a release. Gene drive systems that display threshold-dependent behavior could pot...

The coconut rhinoceros beetle (CRB, Oryctes rhinoceros ) is a severe and invasive pest of coconut and other palms throughout Asia and the Pacific. The biocontrol agent, Oryctes rhinoceros nudivirus (OrNV), has successfully suppressed O. rhinoceros populations for decades but new CRB invasions started appearing after 2007. A single-SNP variant withi...

Background: Hundreds of millions of people get a mosquito-borne disease every year, of which nearly one million die. Mosquito-borne diseases are primarily controlled and mitigated through the control of mosquito vectors. Accurately quantified mosquito dispersal in a given landscape is critical for the design and optimization of the control programs...

Oryctes nudivirus (species OrNV) has been an effective biocontrol agent against the insect pest Oryctes rhinoceros (Coleoptera: Scarabaeidae) for decades, but there is evidence that resistance could be evolving in some host populations. We detected OrNV infection in O. rhinoceros from Solomon Islands and used Oxford Nanopore Technologies (ONT) long...

Oryctes Nudivirus (OrNV) has been an effective biocontrol agent against the insect pest Oryctes rhinoceros (Coleoptera: Scarabaeidae) for decades, but there is evidence that resistance could be evolving in some host populations. We detected OrNv infection in O. rhinoceros from the Solomon Islands and used Oxford Nanopore Technologies (ONT) long-rea...

Background: Halotydeus destructor is a major pest of crops and pastures across southern parts of Australia. This invasive mite has been chemically controlled for over 50 years, but resistance to synthetic pyrethroids and organophosphates is developing. Understanding processes behind the emerging resistance is important for effective management eff...

The discovery of CRISPR-based gene editing and its application to homing-based gene drive systems has been greeted with excitement, for its potential to control mosquito-borne diseases on a wide scale, and concern, for the invasiveness and potential irreversibility of a release. Gene drive systems that display threshold-dependent behavior could pot...

Background Traditional vector control approaches such as source reduction and insecticide spraying have limited effect on reducing Aedes aegypti population. The endosymbiont Wolbachia is pointed as a promising tool to mitigate arbovirus transmission and has been deployed worldwide. Models predict a rapid increase on the frequency of Wolbachia-posit...

Repeated measures analysis (with clutch size as the repeatedly measured variable) of the square-root of the number of eggs laid by successful Aedes aegypti females in the first five oviposition cycles. (DOCX)

Frequency of Wolbachia-positive offspring during the first and fourth clutches of their relatives. Data gathered from 1932 individually screened larvae. (TIF)

Analysis of variance of the influence of kdr frequency, Wolbachia presence and density on the survival of Aedes aegypti females. (DOCX)

Ombrothermic curve of Tubiacanga during the 20 weeks of the first Wolbachia release in Rio de Janeiro. Bars represent weekly rainfall, solid line the mean temperature, the dotted line represents the average maximum temperature and dashed line represent the peak temperature measured 5 km from Tubiacanga. (TIF)

Schematic view of the backcrossing designed to produce an Aedes aegypti population resistant to pyrethroids for new releases in areas where wild mosquito population is highly resistant to insecticides (in this case Urca). (TIF)

Quality control of released wMelBr mosquitoes. (A) Wing size length of Aedes aegypti males (A) and females (B) released in the 20 weeks of Wolbachia deployment in Tubiacanga. Each week had 30 individuals randomly selected. The asterisk shows significance when released mosquitoes had wing length significantly bigger than wild-caught ones. (C) Mean a...

The frequencies of NavR1 and NavR2 alleles and genotypic frequency in wMelRio strain colony maintained under lab conditions during the second release in Tubiacanga. The two columns on the right represent the frequency of kdr alleles in the field population, week 34 representing the period between wMelBr and wMelRio releases, and week 51 during the...

Allelic frequency of the susceptible wild-type (NavS), the kdr allele with a substitution restricted to the 1534 position (NavR1), or concurrent substitutions in both 1534 and 1016 sites (NavR2) during backcrossing to produce the strain wMelBr. (TIF)

Profile of wMelRio and three Ae. aegypti mosquitoes from local field populations (Tubiacanga, Jurujuba and Urca) exposed to two adulticides: (A) the organophosphate malathion (mg/m2) and (B) the pyrethroid deltamethrin (mg/m2) with an exposure of 120 minutes. The dose used to evaluate the resistance ratio of mosquito populations to both insecticide...

Dose x mortality profile in Aedes aegypti adult females exposed to a gradient of concentrations of the larvicide Temephos for one hour, with mortality scored 24h later. (TIF)

Profile of wMelBr, wMelRio and three Ae. aegypti mosquitoes from local field populations (Tubiacanga, Jurujuba and Urca) exposed to two larvicides: (A) diflubenzuron (μg/L) and (B) the organophosphate temephos (mg/mL). Diflubenzuron is currently employed by the Brazilian Ministry of Health. (DOCX)

Logistic regression analysis of the influence of mosquito age, kdr frequency, Wolbachia presence and density on laying at least one egg during the first five clutches. (DOCX)

Female Aedes aegypti mosquitoes infect more than 400 million people each year with dangerous viral pathogens including dengue, yellow fever, Zika and chikungunya. Progress in understanding the biology of mosquitoes and developing the tools to fight them has been slowed by the lack of a high-quality genome assembly. Here we combine diverse technolog...

Medically important arboviruses such as dengue, Zika, and chikungunya viruses are primarily transmitted by the globally distributed mosquito Aedes aegypti. Increasing evidence suggests that transmission can be influenced by mosquito viromes. Herein RNA-Seq was used to characterize RNA metaviromes of wild-caught Ae. aegypti from Bangkok (Thailand) a...

The endosymbiotic bacterium Wolbachia suppresses the capacity for arbovirus transmission in the mosquito Aedes aegypti, and can spread spatially through wild mosquito populations following local introductions. Recent introductions in Cairns, Australia have demonstrated slower than expected spatial spread. Potential reasons for this include: (i) bar...

Female Aedes aegypti mosquitoes infect hundreds of millions of people each year with dangerous viral pathogens including dengue, yellow fever, Zika, and chikungunya. Progress in understanding the biology of this insect, and developing tools to fight it, has been slowed by the lack of a high-quality genome assembly. Here we combine diverse genome te...

Author summary Aedes albopictus, the Asian Tiger Mosquito, is a highly invasive disease vector with a growing global distribution. Designing strategies to prevent invasion and to control Ae. albopictus populations in invaded regions requires knowledge of how Ae. albopictus disperses. Studies comparing Ae. albopictus populations have found little ev...

Relationship between pairwise mtDNA Nei’s D estimates and geographic distance. Colour codes are the same as in Fig 3. No overall trend of IBD was observed. (TIF)

Results of Mantel tests on mtDNA haplotypes. Mantel tests found no significant relationships between Rousset’s a and any of the variables representing barriers or network isolation. (XLSX)

Mechanisms and evolutionary dynamics of sex-determination systems are of particular interest in insect vectors of human pathogens like mosquitoes because novel control strategies aim to convert pathogen-transmitting females into non-biting males, or rely on accurate sexing for the release of sterile males. In Aedes aegypti, the main vector of dengu...

Mechanisms and evolutionary dynamics of sex-determination systems are of particular interest in insect vectors of human pathogens like mosquitoes because novel control strategies aim to convert pathogen-transmitting females into nonbiting males, or rely on accurate sexing for the release of sterile males. In Aedes aegypti, the main vector of dengue...

Aedes albopictus is a highly invasive disease vector with an expanding worldwide distribution. Genetic assays using low to medium resolution markers have found little evidence of spatial genetic structure even at broad geographic scales, suggesting frequent passive movement along human transportation networks. Here we analysed genetic structure of...

Author summary Wolbachia are bacteria that live inside insect cells. In insects that act as viral vectors, Wolbachia can suppress virus transmission to new hosts. Wolbachia have been experimentally introduced into Aedes aegypti mosquito populations to reduce the transmission of dengue, Zika, and other arboviruses that cause human disease. Wolbachia...

Onsite infection frequency (p) at EHW and PP from the onset of releases to the end of D1. The white circle marks the end of releases on 18 April 2013. Infection frequencies remained stable after releases ended. (TIFF)