using-fluorescent-dye-rhodamine-b-to-study-mating-competitiveness

Using the Fluorescent Dye, Rhodamine B, to Study Mating Competitiveness in Male <em>Aedes aegypti</em> Mosquitoes

The success of sterile or incompatible insect technique-based population suppression programs depends on the ability of released males to compete for ...

National Environmental Agency

Dengue fever is currently one of the most important mosquito-borne diseases that affect humans. With neither vaccines nor treatment available, prevention of the disease relies heavily on surveillance and control of mosquito vectors. In the present study, we have evaluated and showed the potential use of the Dengue NS1 Ag Strip(®) for the detection of dengue virus (DENV) in Aedes aegypti. Initial results showed that the sensitivity of the test kit in detecting DENV in wild-caught mosquitoes is comparable to that of real-time reverse transcriptase-polymerase chain reaction. The detection of naturally infected Ae. aegypti with the NS1 rapid test kit in our dengue cluster investigation further illustrates its potential use for surveillance of DENV in wild mosquito populations. The kit can easily be used in a simple field station, and minimal training is required. The results can be obtained in less than an hour. Employment of the kit in the field could help guide mosquito control operations in the prioritization of resources in controlling the transmission of DENV. In this study the potential of the kit for field surveillance of infected dengue vectors, which are epidemiologically important, has been demonstrated.

Evaluation of the Dengue NS1 Ag Strip® for detection of dengue virus antigen in Aedes aegypti (Diptera: Culicidae).

In August 2008, a team from the National Environmental Agency conducted an entomological investigation of a chikungunya cluster in Singapore, with the primary aim of identifying the vector responsible for the outbreak and to assess the vector control operation. A total of 173 adult mosquitoes were caught using both the sweep-net method and the BG Sentinel Traps in and around the affected workers' quarters. Of these, 120 (69.4%) were Aedes albopictus and the rest were Culex quinquefasciatus. More than 2700 Ae. albopictus larvae were also collected from 33 breeding habitats detected. No Aedes aegypti was found. During the preintervention period, 6 (8.4%) out of 71 adult female Ae. albopictus were found positive for the chikungunya virus (CHIKV). Vector control measures resulted in a 90% reduction of adult Ae. albopictus caught by BG Sentinel Traps. Postintervention surveillance revealed the presence of CHIKV-positive mosquitoes. These findings led to continued intensive vector control operation in the affected area that further reduced vector population and interrupted the transmission of the disease. The E1 gene sequence of the CHIKV was identical to those of CHIKV isolated from human chikungunya cases working in the affected area, and contained the A226V mutation. The incrimination of Ae. albopictus as a major vector involved in the transmission of A226V CHIKV had led to the revision of chikungunya control strategy in Singapore. This study suggests the benefit of a vector control program that includes the evaluation of control measures in conjunction to virological surveillance in vector population.

Entomological investigation and control of a chikungunya cluster in Singapore.

Taxonomy that utilizes morphological characteristics has been the gold standard method to identify mosquito species. However, morphological identification is challenging when the expertise is limited and external characters are damaged because of improper specimen handling. Therefore, we explored the applicability of mitochondrial cytochrome C oxidase subunit 1 (COI) gene-based DNA barcoding as an alternative tool to identify mosquito species. In the present study, we compared the morphological identification of mosquito specimens with their differentiation based on COI barcode, in order to establish a more reliable identification system for mosquito species found in Singapore.

DNA barcoding: complementing morphological identification of mosquito species in Singapore.

Understanding the interaction between Aedes vectors and dengue viruses (DENV) has significant implications in determining the transmission dynamics of dengue. The absence of an animal model and ethical concerns regarding direct feeding of mosquitoes on patients has resulted in most infection studies using blood meals spiked with laboratory-cultured DENV. Data obtained from such studies may not reflect the natural human-mosquito transmission scenario. This study explored the potential of using membrane feeding of dengue patient's blood as a substitute for direct skin feeding.

Membrane feeding of dengue patient's blood as a substitute for direct skin feeding in studying Aedes-dengue virus interaction.

Sri Lanka has achieved 'malaria-free' status and is now in the phase of prevention of re-introduction of malaria. Imported malaria remains a challenge to resurgence of the disease. The diagnostic challenges encountered and the rapid response initiated to manage a Plasmodium infection, which was later confirmed as Plasmodium knowlesi, the first reported case from Sri Lanka, is discussed.

Diagnostic challenges and case management of the first imported case of Plasmodium knowlesi in Sri Lanka.

We report a case of a Singaporean who acquired Zika virus (ZIKV) during a visit to Cuba. The infection was confirmed using molecular and serological methods. This report highlights potential drawbacks of using IgG serology for diagnosis of flavivirus infections in endemic regions. The low viremia detected during the early phase of this case resulted in low mosquito infectivity rates, suggesting the possibility of ZIKV transmission prior to clinical onset. The report also emphasizes the challenges of public health interventions for Zika fever and the importance of sustaining a low vector population to reduce the risk of arbovirus transmission in vulnerable regions.

Article	Year
Evaluation of the Dengue NS1 Ag Strip® for detection of dengue virus antigen in Aedes aegypti (Diptera: Culicidae). Vector borne and zoonotic diseases (Larchmont, N.Y.)\| PubMed ID: 21395416	2011
Entomological investigation and control of a chikungunya cluster in Singapore. Vector borne and zoonotic diseases (Larchmont, N.Y.)\| PubMed ID: 21395419	2011
DNA barcoding: complementing morphological identification of mosquito species in Singapore. Parasites & vectors\| PubMed ID: 25498759	2014
Membrane feeding of dengue patient's blood as a substitute for direct skin feeding in studying Aedes-dengue virus interaction. Parasites & vectors\| PubMed ID: 27083158	2016
Diagnostic challenges and case management of the first imported case of Plasmodium knowlesi in Sri Lanka. Malaria journal\| PubMed ID: 28327145	2017
Viral and Antibody Kinetics, and Mosquito Infectivity of an Imported Case of Zika Fever Due to Asian Genotype (American Strain) in Singapore. Viruses\| PubMed ID: 29346272	2018

Cheong Huat Tan

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