Oral Ingestion of Transgenic RIDL Ae. aegypti Larvae Has No Negative Effect on Two Predator Toxorhynchites Species

Oreenaiza Nordin,Murad Shahnaz,Teoh Guat Ney,Nor Azlina Abdul Halim,Renaud Lacroix,Sarah Scaife,Azahari Abdul Hadi,Camilla Beech,Han Lim Lee,Derric David Nimmo,Khairul Asuad Mohamed,Zulkamal Safi'In Muhammad,Luke Alphey,Wesley Donald,Wasi Ahmed Nazni,Wong Hong Ming,Andrew Robert Mckemey,Peter Winskill,Douglas M Watts

doi:10.1371/journal.pone.0058805

Abstract

Dengue is the most important mosquito-borne viral disease. No specific treatment or vaccine is currently available; traditional vector control methods can rarely achieve adequate control. Recently, the RIDL (Release of Insect carrying Dominant Lethality) approach has been developed, based on the sterile insect technique, in which genetically engineered ‘sterile’ homozygous RIDL male insects are released to mate wild females; the offspring inherit a copy of the RIDL construct and die. A RIDL strain of the dengue mosquito, Aedes aegypti, OX513A, expresses a fluorescent marker gene for identification (DsRed2) and a protein (tTAV) that causes the offspring to die. We examined whether these proteins could adversely affect predators that may feed on the insect. Aedes aegypti is a peri-domestic mosquito that typically breeds in small, rain-water-filled containers and has no specific predators. Toxorhynchites larvae feed on small aquatic organisms and are easily reared in the laboratory where they can be fed exclusively on mosquito larvae. To evaluate the effect of a predator feeding on a diet of RIDL insects, OX513A Ae. aegypti larvae were fed to two different species of Toxorhynchites (Tx. splendens and Tx. amboinensis) and effects on life table parameters of all life stages were compared to being fed on wild type larvae. No significant negative effect was observed on any life table parameter studied; this outcome and the benign nature of the expressed proteins (tTAV and DsRed2) indicate that Ae. aegypti OX513A RIDL strain is unlikely to have any adverse effects on predators in the environment.

Highlights

Epidemic dengue fever and dengue haemorrhagic fever (DHF) have emerged as major global public health problems in recent decades
There was no significant difference between larval or pupal development time for any of the treatments or the two different species of Toxorhynchites (Figure 1 and Table S1)
There was a significantly longer development time of L4 male and female larvae in the control fed group of Tx. amboinensis compared to Tx. splendens

Summary

Introduction

Epidemic dengue fever and dengue haemorrhagic fever (DHF) have emerged as major global public health problems in recent decades. According to the World Health Organization (WHO) dengue epidemiology is rapidly worsening [1] with increased frequency of outbreaks and expansion into new geographical areas. This expansion has partly been driven by the rapid increase of the global range of Aedes aegypti in the last few decades. Current control methods are based primarily on breeding site elimination with larvicides or other methods, and some use of adulticides These methods have not proven adequate to prevent epidemic dengue in any but the most favourable of circumstances [4,5,6]. The mechanism of sterility is the transmission to the progeny of a lethal transgene; equivalent to the transmission of radiation-induced dominant lethal mutations in classical SIT

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Discussion

Conclusion