Densovirus Oil Suspension Significantly Improves the Efficacy and Duration of Larvicidal Activity against Aedes albopictus.

Khadija Batool,Ting Yang,Ye Xu,Siyu Zhao,Jie Xiao,Xiaoguang Chen,Intikhab Alam,Jinbao Gu,Yugu Xie,Peiwen Tao,Jiao Chen

doi:10.3390/v14030475

Khadija Batool, Ting Yang + Show 9 more

Open Access

https://doi.org/10.3390/v14030475

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Abstract

Aedes albopictus is the sole vector for various mosquito-borne viruses, including dengue, chikungunya, and Zika. Ecofriendly biological agents are required to reduce the spread of these mosquito-borne infections. Mosquito densoviruses (MDVs) are entomopathogenic mosquito-specific viruses, which can reduce the capacity of isolated vectors and decrease mosquito-borne viral disease transmission. However, their variable pathogenicity restricts their commercial use. In the present study, we developed a series of novel larvicide oil suspensions (denoted Bacillus thuringiensis (Bti) oil, Ae. albopictus densovirus (AalDV-5) oil, and a mixture of AalDV-5+Bti oil), which were tested against Ae. albopictus larvae under experimental semi-field and open-field conditions. The effect of AalDV-5 on non-target species was also evaluated. The combined effect of AalDV-5+Bti was greater than that of individual toxins and was longer lasting and more persistent compared with the laboratory AalDV-5 virus strain. The virus was quantified on a weekly basis by quantitative polymerase chain reaction (qPCR) and was persistently detected in rearing water as well as in dead larvae. Wildtype densovirus is not pathogenic to non-target organisms. The present findings confirm the improved effect of a mixed microbial suspension (AalDV-5+Bti oil) larvicide against Ae. albopictus. The development and testing of these products will enable better control of the vector mosquitoes.

Highlights

Mosquito-borne pathogens are serious health hazards and continue to affect human populations globally [1]
To improve the bio-efficacy of densovirus infection, we developed a novel biological larvicide, an oil suspension containing a mixture of Ae. albopictus densovirus (AalDV-5) and Bacillus thuringiensis (Bti) oil toxins, and evaluated its effectiveness and persistence in a field-based setting
During the 4-week semi-field study of the 0-month sample, AalDV-5+Bti oil was applied to 9 batches of larvae that were added sequentially to water buckets, with 92% total mortality observed on day 32, whereas Bti oil was applied to 8 batches of larvae with 18.66% mortality

Summary

Introduction

Mosquito-borne pathogens are serious health hazards and continue to affect human populations globally [1]. The Aedes albopictus mosquito is one of the most invasive mosquito species on the planet and is a vector of several arboviruses of public health concern in the tropics and subtropics, including dengue, chikungunya, and Zika viruses [2–4]. The use of chemical insecticides is a leading approach for controlling vector-borne diseases. Their widespread use has resulted in environmental pollution, insecticide resistance, and the need for new, long-lasting agents to control vector populations [8]. To reduce the present reliance on insecticide-based mosquito control, bio-control solutions aim to be long-term control agents and target a variety of mosquito species [12]. Bacillus thuringiensis (Bti) formulations [13,14], for example long-lasting Ae. albopictus larvicidal Bti-blocks, are highly effective in vector control strategies [15] and plant essential oils used for mosquito control [16–18]

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