Dengue in Dhaka, Bangladesh: Hospital-based cross-sectional KAP assessment at Dhaka North and Dhaka South City Corporation area.

Dengue, the most important mosquito-borne viral disease of humans is a recurring global health problem. In Bangladesh, dengue outbreaks are on the increase despite the efforts of government and it is not clear what the understanding of the general Dhaka population towards dengue fever is. Knowledge, attitude and practice (KAP) studies are essential guides in public health interventions. Hence, using KAP, this study aims to assess patient-perspectives with regards to factors associated with dengue, as well as investigate the associated factors between the two corporations in Dhaka. A Hospital-based cross-sectional study of 242 fever patients from two city-corporations in Dhaka (Dhaka North City Corporations, DNCC (n = 91, 37.6%) and Dhaka South City Corporation, DSCC (n = 151, 62.4%) was conducted using pre-tested KAP items. Wilcoxon's Rank Sum was used to determine the KAP by DNCC, DSCC and both corporations and multivariate Poisson regression analyses. The two corporations were analysed separately due to the differences in income distribution, concentration of slums, hospitals and clinics. The study found that more than half of the study population were knowledgeable about dengue (mean percentage scores was 52%), possess an appropriate and acceptable attitude towards the disease (69.2%), and about two thirds of the respondents (71.4%) engaged in practices towards its prevention. After adjusting for the potential cofounders, the factors associated with KAP about dengue fever varied between DNCC and DSCC; with duration of residency and use of mosquito nets were associated with knowledge in the north while income class and age were associated with knowledge and attitude in the south. In the pooled analysis (combining both corporations), knowledge of dengue was associated with good practice towards dengue fever among the respondents. The duration of residence in Dhaka (10+ years), not using mosquito nets and length of time spent in the hospital (7+ days) due to dengue, and decreased knowledge (Adjusted coefficient (ß) = -0.01, 95%CI: -0.02, -0.01) were associated with attitude towards dengue in DNCC. On the other hand, middle-high income class, age (40+ years) and increased knowledge were associated with practice towards dengue in DSCC (ß = 0.02, 95%CI: 0.01, 0.03). Efforts to increase knowledge about dengue fever through education by the administrations of both corporations would benefit from targeting these high-risk groups for a more sustainable outcome.

Effect of Serotype and Strain Diversity on Dengue Virus Replication in Australian Mosquito Vectors.

Dengue virus (DENV) is the most important mosquito-borne viral pathogen of humans, comprising four serotypes (DENV-1 to -4) with a myriad of genotypes and strains. The kinetics of DENV replication within the mosquito following ingestion of a blood meal influence the pathogen's ability to reach the salivary glands and thus the transmission potential. The influence of DENV serotype and strain diversity on virus kinetics in the two main vector species, Aedes aegypti and Ae. albopictus, has been poorly characterized. We tested whether DENV replication kinetics vary systematically among serotypes and strains, using Australian strains of the two vectors. Mosquitoes were blood fed with two strains per serotype, and sampled at 3, 6, 10 and 14-days post-exposure. Virus infection in mosquito bodies, and dissemination of virus to legs and wings, was detected using qRT-PCR. For both vectors, we found significant differences among serotypes in proportions of mosquitoes infected, with higher numbers for DENV-1 and -2 versus other serotypes. Consistent with this, we observed that DENV-1 and -2 generally replicated to higher RNA levels than other serotypes, particularly at earlier time points. There were no significant differences in either speed of infection or dissemination between the mosquito species. Our results suggest that DENV diversity may have important epidemiological consequences by influencing virus kinetics in mosquito vectors.

Wolbachia strain wAlbB blocks replication of flaviviruses and alphaviruses in mosquito cell culture.

BACKGROUND: Wolbachia pipientis are bacterial endosymbionts of arthropods currently being implemented as biocontrol agents to reduce the global burden of arboviral diseases. Some strains of Wolbachia, when introduced into Aedes aegypti mosquitoes, reduce or block the replication of RNA viruses pathogenic to humans. The wAlbB strain of Wolbachia was originally isolated from Aedes albopictus, and when transinfected into Ae. aegypti, persists in mosquitoes under high temperature conditions longer than other strains. The utility of wAlbB to block a broad spectrum of RNA viruses has received limited attention. Here we test the ability of wAlbB to reduce or block the replication of a range of Flavivirus and Alphavirus species in cell culture. METHODS: The C6/36 mosquito cell line was stably infected with the wAlbB strain using the shell-vial technique. The replication of dengue, West Nile and three strains of Zika (genus Flavivirus), and Ross River, Barmah Forest and Sindbis (genus Alphavirus) viruses was compared in wAlbB-infected cells with Wolbachia-free controls. Infectious virus titres were determined using either immunofocus or plaque assays. A general linear model was used to test for significant differences in replication between flaviviruses and alphaviruses. RESULTS: Titres of all viruses were significantly reduced in cell cultures infected with wAlbB versus Wolbachia-free controls. The magnitude of reduction in virus yields varied among virus species and, within species, also among the strains utilized. CONCLUSION: Our results suggest that wAlbB infection of arthropods could be used to reduce transmission of a wide range of pathogenic RNA viruses.

Recent update on anti-dengue drug discovery.

Dengue is the most important arthropod-borne viral disease of humans, with more than half of the global population living in at-risk areas. Despite the negative impact on public health, there are no antiviral therapies available, and the only licensed vaccine, Dengvaxia®, has been contraindicated in children below nine years of age. In an effort to combat dengue, several small molecules have entered into human clinical trials. Here, we review anti-DENV molecules and their drug targets that have been published within the past five years (2014-2018). Further, we discuss their probable mechanisms of action and describe a role for classes of clinically approved drugs and also an unclassified class of anti-DENV agents. This review aims to enhance our understanding of novel agents and their cognate targets in furthering innovations in the use of small molecules for dengue drug therapies.

Vector competence of Australian Aedes aegypti and Aedes albopictus for an epidemic strain of Zika virus.

BACKGROUND: Recent epidemics of Zika virus (ZIKV) in the Pacific and the Americas have highlighted its potential as an emerging pathogen of global importance. Both Aedes (Ae.) aegypti and Ae. albopictus are known to transmit ZIKV but variable vector competence has been observed between mosquito populations from different geographical regions and different virus strains. Since Australia remains at risk of ZIKV introduction, we evaluated the vector competence of local Ae. aegypti and Ae. albopictus for a Brazilian epidemic ZIKV strain. In addition, we evaluated the impact of daily temperature fluctuations around a mean of 28°C on ZIKV transmission and extrinsic incubation period. METHODOLOGY/PRINCIPAL FINDINGS: Mosquitoes were orally challenged with a Brazilian ZIKV strain (8.8 log CCID50/ml) and maintained at either 28°C constant or fluctuating temperature conditions. At 3, 7 and 14 days post-infection (dpi), ZIKV RNA copies were quantified in mosquito bodies, as well as wings and legs, using qRT-PCR, while virus antigen in saliva (a proxy for transmission) was detected using a cell culture ELISA. Despite high body and disseminated infection rates in both vectors, the transmission rates of ZIKV in saliva of Ae. aegypti (50-60%) were significantly higher than in Ae. albopictus (10%) at 14 dpi. Both species supported a high viral load in bodies, with no significant differences between constant and fluctuating temperature conditions. However, a significant difference in viral load in wings and legs between species was observed, with higher titres in Ae. aegypti maintained at constant temperature conditions. For ZIKV transmission to occur in Ae. aegypti, a disseminated virus load threshold of 7.59 log10 copies had to be reached. CONCLUSIONS/SIGNIFICANCE: Australian Ae. aegypti are better able to transmit a Brazilian ZIKV strain than Ae. albopictus. The results are in agreement with the global consensus that Ae. aegypti is the major vector of ZIKV.