Growth inhibitory effect of phenolic extracts of Ziziphus jujuba Mill.in dengue vector Aedes aegypti(L)in parent and F1 generation

Objective: To evaluate the lethal and emergence inhibitory effect of alkaloid, phenolic and terpenoid extracts of Ziziphus jujuba(Z. jujuba; Rhamnaceae) against Aedes aegypti(Diptera: Culicidae), and to explore the effect of the most effective fraction on developmental and biochemical parameters of the dengue vector. Methods: The fourth instar larvae of Aedes aegypti were exposed to alkaloid, phenolic and terpenoid extracts from Z. jujuba leaves to test their toxicity and emergence inhibitory effects. Phenolic extract, being the most effective was further tested against the mosquitoes for their growth inhibitory effect supported by biochemical changes in the parent and F1 generation. Results: While the different secondary metabolite fractions i.e., alkaloid, phenolics and terpenoid caused mortality at larval and pupal stages, the LC_(50) value was the lowest for phenolic fraction. Further study carried out with the phenolic fraction revealed that it affected growth by decreasing adult life span, fertility and fecundity of the mosquitoes. The reduction in growth was also accompanied by decrease in carbohydrate and lipid levels. Conclusions: It is concluded that the phenolic extract of the leaves of Z. jujuba is a potential candidate for control of Aedes mosquitoes.

Recent advances on pathogenesis,diagnosis,prevention,immunological aspects,and vectors of dengue:A review

Dengue is a vector-borne disease caused by the dengue virus(DENV)of family Flaviviridae.Dengue fever is common in both developed and developing countries.Globally,approximately 400 million cases of dengue fever are reported annually,resulting in approximately 22000 fatalities.Dengue cases in India have progressively increased in the last decade.In recent years,substantial progress has been made in understanding various aspects of dengue,including its pathogenesis,diagnosis,prevention strategies,immunological responses,and the role of vectors in its transmission.The transmission of a positive RNA virus occurs through Aedes mosquitoes,specifically Aedes aegypti and Aedes albopictus.This virus is associated with a wide spectrum of symptoms,ranging from mild undifferentiated fever to severe hemorrhagic fever and shock,posing a potential threat to human health.There are 4 types of antigenically distinct dengue serotypes(DENV-1 to DENV-4)and among them,DENV-2 is more lethal and extremely severe.To overcome the severity of dengue,Dengvaxia is administered to children 9 to 16 years old with evidence of previous dengue infection.The diagnosis of dengue is carried out by ELISA-based non-structural protein(NS1)and immunoglobulin tests.However,there are no specific biomarkers to identify severe disease progression.Climatic factors and temperature play an important role in complex interaction among host,vector,and virus to manifest the severity of dengue.There is a need for the refinement of climate-based disease forecasting models in India to effectively control the spread of dengue.The mosquito repellent should be used periodically to kill or repel the Aedes mosquito to prevent the spread of dengue in humans.

The transmission of dengue virus with Aedes aegypti mosquito in a heterogeneous environment

This paper deals with dengue virus transmitted by the mosquito Aedes aegypti.A reaction-diffusion model is proposed incorporating both human and the A.aegypti population,where we divided mosquitoes into two sub-populations:the winged population and an aquatic form,with the winged mosquito population divided into the susceptible and infected classes.The threshold Qo depending on spatial heterogeneity is introduced for the mosquito population.Moreover,we introduce the basic reproduction number Rq for the infected classes,as well as its analytical properties.Qo and Ho are utilized to investigate the stability of the mosquito-established equilibriums.Our results show that the mosquitoes persist if Qo>1,while the transmission of dengue virus depends on the condition whether Ho<1 or Ho>1.

Phylogenetic Analysis of the Dengue Virus Strains Causing the 2019 Dengue Fever Outbreak in Hainan,China

Dengue virus is an arthropod-borne pathogen that is transmitted to humans primarily by Aedes spp.mosquitos,causing the acute infectious disease,dengue fever(DF).Until 2019,no dengue outbreak had been reported in Hainan Province for over 20 years.However,in early September of 2019,an increasing number of infected cases appeared and the DF outbreak lasted for over one month in Haikou City,Hainan Province.In our study,we collected 97 plasma samples from DF patients at three hospitals,as well as 1585 mosquito larvae samples from puddles in different areas of Haikou.There were 49(50.5%)plasma samples found to be strongly positive and 9(9.3%)plasma samples were weakly positive against the NS1 antigen.We discovered DENV both in the patient's plasma samples and mosquito larvae samples,and isolated the virus from C6/36 cells inoculated with the acute phase serum of patients.Phylogenetic analysis revealed that the new strains were the most closely related to the epidemic strain in the southern regions of China,belonging to lineageⅣ,genotypeⅠ,DENV-1.Compared to the seven closest strains from neighboring countries and provinces,a total of 18 amino acid mutations occurred in the coding sequences(CDS)of the new isolated strain,DENV1 HMU-HKU-2.Our data shows that dengue virus is re-emerged in Hainan,and pose new threats for public health.Thus regular molecular epidemiological surveillance is necessary for control and prevention of DENV transmission.