Dengue Virus Dissemination Research Articles

Developing Wolbachia-based disease interventions for an extreme environment.

Aedes aegypti mosquitoes carrying self-spreading, virus-blocking Wolbachia bacteria are being deployed to suppress dengue transmission. However, there are challenges in applying this technology in extreme environments. We introduced two Wolbachia strains into Ae. aegypti from Saudi Arabia for a release program in the hot coastal city of Jeddah. Wolbachia reduced infection and dissemination of dengue virus (DENV2) in Saudi Arabian mosquitoes and showed complete maternal transmission and cytoplasmic incompatibility. Wolbachia reduced egg hatch under a range of environmental conditions, with the Wolbachia strains showing differential thermal stability. Wolbachia effects were similar across mosquito genetic backgrounds but we found evidence of local adaptation, with Saudi Arabian mosquitoes having lower egg viability but higher adult desiccation tolerance than Australian mosquitoes. Genetic background effects will influence Wolbachia invasion dynamics, reinforcing the need to use local genotypes for mosquito release programs, particularly in extreme environments like Jeddah. Our comprehensive characterization of Wolbachia strains provides a foundation for Wolbachia-based disease interventions in harsh climates.

Correction: Dengue Virus 2 American-Asian Genotype Identified during the 2006/2007 Outbreak in Piauí, Brazil Reveals a Caribbean Route of Introduction and Dissemination of Dengue Virus in Brazil

Correction: Dengue Virus 2 American-Asian Genotype Identified during the 2006/2007 Outbreak in Piauí, Brazil Reveals a Caribbean Route of Introduction and Dissemination of Dengue Virus in Brazil

Dengue virus 2 American-Asian genotype identified during the 2006/2007 outbreak in Piauí, Brazil reveals a Caribbean route of introduction and dissemination of dengue virus in Brazil.

Dengue virus (DENV) is the most widespread arthropod-borne virus, and the number and severity of outbreaks has increased worldwide in recent decades. Dengue is caused by DENV-1, DENV- 2, DENV-3 and DENV-4 which are genetically distant. The species has been subdivided into genotypes based on phylogenetic studies. DENV-2, which was isolated from dengue fever patients during an outbreak in Piaui, Brazil in 2006/2007 was analyzed by sequencing the envelope (E) gene. The results indicated a high similarity among the isolated viruses, as well as to other DENV-2 from Brazil, Central America and South America. A phylogenetic and phylogeographic analysis based on DENV-2E gene sequences revealed that these viruses are grouped together with viruses of the American-Asian genotype in two distinct lineages. Our results demonstrate the co-circulation of two American-Asian genotype lineages in northeast Brazil. Moreover, we reveal that DENV-2 lineage 2 was detected in Piauí before it disseminated to other Brazilian states and South American countries, indicating the existence of a new dissemination route that has not been previously described.

Re: First isolation of dengue virus from the 2010 epidemic in Nepal.

We compliment the team of investigators from Kathmandu, Nepal for their meticulous serologic and molecular investigations of patients suspected with dengue virus (DENV) infection during the large 2010 epidemic in Nepal [1]. Several measures are needed to address the rapid emergence of DENV infection in different regions of Nepal. Recently, DENV infection was reported in Chitwan with a large number of patients presenting in the Chitwan Medical College Teaching Hospital and other privately-run clinics and nursing homes in Bharatpur [2]. Furthermore, in Jhapa district, 17 people, including 13 from Mechinagar Municipality alone, were found to be infected with the disease. Dengue cases were found in Kakadvitta and its adjoining areas, while 12 patients were receiving treatment in various hospitals in Parsa district and 13 had returned home after treatment [3]. In Nepal, diagnosis of DENV infections was based on serologic testing for IgM antibody at different centres in Kathmandu and Mahendranagar, Kanchanpur and Kuhsibu employing IgM-capture ELISA [4]. Molecular investigations were performed at the National Institute of Infectious Diseases, Tokyo, Japan [1]. Rather than relying on a multi-step capture ELISA, it would be convenient to opt for point-of-care, rapid diagnostics in different heath care centres across Nepal. Such assay formats involve 1–2 steps, are user friendly and require minimum equipment. Neither sophisticated laboratory facilities nor highly trained technologists are needed. A concurrent testing for NS1, IgM and IgG is ideal since it would address even cases with atypical presentations. During the 2006–2007 outbreak of DENV in Malaysia, the molecular and serologic response in in ten adults with a fatal outcome was remarkable. DENV infection was confirmed in all ten cases by serological tests. Seven were both IgM and IgG positive while three were IgM negative and IgG positive. Eight of the patients (two were unavailable) tested positive for dengue NS1 while DENV-1 was isolated from one case. Consequently, the presence of anti-dengue IG anybody with dengue NS1 antigen confirmed the secondary infection in all eight patients [5]. Screening for DENV antigenemia among international travellers at different ports of entry could be introduced to detect persons infected with the virus who could be bitten by DENV vectors during their stay in different regions of Nepal. After viral amplification in mosquitoes, a secondary dissemination of the disease could occur. Furthermore, even prospective international travellers from Nepal to DENV endemic areas should be asked to protect themselves against the mosquito bites while away on any business or pleasure trip. It is important to educate the community about otherwise ignored basic facts about of the mosquito and protection from bites. The mosquitoes of Aedes genus, A. aegypti and A. albopictus are responsible for multiplication and dissemination of dengue Virus, chikungunya virus and yellow fever virus. Both A. aegypti and A. albopictus are day-biters but will bite at night if there is sufficient artificial lighting. A. aegypti is particularly fond of ankles when searching for a good spot to bite a human being [6]. A. albopictus is a very aggressive day-time biter, with peaks occurring during early morning and late afternoon. Both are container-inhabiting species that lay eggs in domestic and peri-domestic clean water-containing receptacles. Anti-mosquito measures are practiced universally at night when insecticides and mosquito repellents and mosquito nets are used. In spite of such meticulous night-time care taking, one could still be exposed to bites from mosquitoes of the genus Aedes as they are mostly day-biters [6]. The public should be advised to wear full-length clothes to cover their arms and legs during day-time as well as in the evenings if they go outdoors. As a final suggestion, fashion designers in Nepal and elsewhere should be urged to create attractive formal and informal clothing for both sexes that would not protect against mosquito bites but also is attractive and suited to the local customs each region. Prominent public personalities like film stars, actors, athletes should wear such clothes during their appearance in public. School children should avoid use of skirts or shorts while in school. local governments should declare an exemption of such garments from sales local taxes.

Dissemination in Pigtailed Macaques after Primary Infection of Dengue-3 Virus

Nonhuman primates (NHPs) play as indispensable animal model in biomedical research for studying a variety of human health issues, diseases and disorders, therapies, and preventive strategies. Since the immunological and physiological responses of NHPs, at some extent, to experimental viral infections are similar to humans, it is possible that studies of dengue infection in NHPs may aid understanding of dengue infection in humans. In this study,we used pigtailed macaques ( Macaca nemestrina ) as the experimental animal to study dengue-3 (DEN-3) virus infection.We evaluated DEN-3 viral distribution and replication sites after a primary infection in all collected tissues. Sequential localization in tissue of DEN-3 virus was studied in pigtailed macaques euthanized three days post viral inoculation (10 pfu mL ). Pigtailed macaque that was inoculated subcutaneously or intravenously; showed the highest viremia (62.94 pfu mL and 58.62 pfu mL ) detected by one step reverse transcription real time PCR. The virus inoculated in pigtailed macaques by subcutaneous injection was rapidly disseminated from the inoculation site to the lymph nodes, adrenal glands, kidneys, heart, thyroid, liver, prostate gland, and seminal vesicles. Meanwhile, dissemination of dengue virus in pigtailed macaques inoculated intravenously was detected in lymph nodes, thymus, salivary glands, liver, and prostate gland. This study suggested that the above mentioned-tissue specimens are involved or affected by DEN-3 virus replication and the route of infection seemed to have influenced the virus dissemination.

Evaluation of the Function of a Type I Peritrophic Matrix as a Physical Barrier for Midgut Epithelium Invasion by Mosquito-Borne Pathogens in Aedes aegypti

In addition to modulating blood meal digestion and protecting the midgut epithelial cells from mechanical and chemical damage, a biological function attributed to the mosquito type I peritrophic matrix (PM) is preventing or reducing pathogen invasion, especially from Plasmodium spp. Previously, we demonstrated that chitin is an essential component of the PM and is synthesized de novo in response to blood feeding in Aedes aegypti. Therefore, knocking down chitin synthase expression by RNA interference severely disrupts formation of the PM. Utilizing this artificial manipulation, we determined that the absence of the PM has no effect on the development of Brugia pahangi or on the dissemination of dengue virus. However, infectivity of Plasmodium gallinaceum is lower, as measured by oocyst intensity, when the PM is absent. Our findings also suggest that the PM seems to localize proteolytic enzymes along the periphery of the blood bolus during the first 24 hours after blood feeding. Finally, the absence of the PM does not affect reproductive fitness, as measured by the number and viability of eggs oviposited.

Investigations of dengue‐2 susceptibility and body size among Aedes aegypti populations

The mosquito Aedes aegypti (L.) (Diptera: Culicidae) is the primary global vector for dengue virus (DENV), yet considerable genetic variation exists among populations in terms of its competence to vector DENV. Variability in adult body size has also been observed among various mosquito populations and several studies have reported a relationship between body size and arbovirus dissemination, although most of these relied on artificially derived variation in body size. Here we examine the relationship between body size and disseminated DENV infection among 10 Ae. aegypti populations reared under optimum laboratory conditions. Body size variability was inferred from wing length measurements and DENV competence was evaluated as the proportion of individuals with disseminated infections following exposure to the dengue-2 JAM1409 strain. There were significant differences in mean wing lengths among populations (anova, F(9,22)= 7.10, P < 0.0001), ranging from 2.16 mm (Bangkok population) to 2.79 mm (MOYO-S [susceptible] population). We also observed significant differences among some populations in mean DENV infection rates (Waller-Duncan K-ratio t-test), ranging from 19.54% (MOYO-R [refractory] population) to 56.60% (MOYO-S population). However, we did not observe evidence for significant interactions between body size and DENV dissemination. We suggest that either the two traits are genetically independent or that our ability to detect interactions between them was limited by their respective inheritances as quantitative traits.