New occurrences of mosquitoes (Diptera: Culicidae) in the Atlantic Forest biome of the Brazilian Northeast

ABSTRACT Background: Information regarding the distribution of Culicidae species in the northeastern region of Brazil is scarce. Methods: Immatures were collected from approximately four fragments of the Atlantic Forest. Results: This study presents new occurrences of 18 Culicidae species in Pernambuco state: Anopheles kompi, Georgecraigius fluviatilis, Culex bidens, Culex chidesteri, Culex bastagarius, Culex imitator, Mansonia humeralis, Wyeomyia incaudata, Uranotaenia apicalis, Culex mollis, Culex usquatus, Culex dunni, Culex serratimarge, Culex ybarmis, Culex microphyllus, Sabethes purpureus, Wyeomyia pilicauda, and Wyeomyia airosai. The last nine species were also new records for the northeast region. Conclusions: With the inclusion of these newly recorded species, the total number of mosquitoes documented in Pernambuco state now rises to 94.

Progress of researches on symbionts in the management of mosquito-borne infectious diseases / 中国血吸虫病防治杂志

Mosquitoes are the main vectors of many infectious diseases, including malaria and yellow fever, which seriously threaten human health across the world. In addition to the use of chemical insecticides, genetic control is a new attempt to currently available interventions used for mosquito vector control. In terms of ecological safety, however, symbiotic control as a novel approach has been proposed for mosquito control. Since there are multiple symbiotic microflora inhabiting in a variety of tissues of mosquitoes, including the digestive tract, they may affect the transmission of mosquito-borne infectious diseases through affecting the lifespan, reproductive competence, and vector competence of the host. In this review, the interactions between symbionts in mosquitoes were summarized, and the research progress of mosquito-associated symbionts in the management of mosquitoborne infectious diseases was reviewed.

Experimental infection and vector competence of Zika virus in Aedes aegypti mosquitoes from Acapulco, Guerrero, Mexico / Infección experimental y competencia vectorial del virus Zika en mosquitos Aedes aegypti de Acapulco, Guerrero, México

Abstract: Objective: To gain a better understanding of the Zika virus (ZIKV) vector transmission in Mexico, we determined the vector competence of a local population ofAe. aegypti(Acapulco, Guerrero) for a strain of ZIKV isolated from a Mexican febrile patient. Materials and methods: Eggs were hatched and larvae were reared under controlled conditions. After five days post-emergence, female mosquitoes were fed an infectious blood-meal containing ZIKV. Mosquitoes were analyzed at 4, 7 and 14-day post-infection (dpi). Infection (gut), dissemination (wings, legs and heads) and potential transmission (salivary glands) were assessed by RT-qPCR. The RockefellerAe. aegyptistrain was used as ZIKV infection control. Results: ZIKV infection, dissemination, and potential transmission rates were 96.2, 96.1 and 93.2%, respectively. Conclusions: Ae. aegypti(F1) from Acapulco were very susceptible to ZIKV infection, and showed similar vector competence to that of the susceptible Rockefeller strain. To our knowledge, this is the first report of vector competence for ZIKV performed in a Mexican laboratory.

Resumen: Objetivo: Determinar la competencia vectorial de una población local deAe. aegyptipara transmitir el virus Zika (ZIKV) aislado de un paciente febril mexicano. Material y métodos: Se desarrolló la primera generación (F1) de mosquitosAe. aegyptien el insectario a partir de huevos colectados mediante ovitrampas en la Colonia Renacimiento, Acapulco, Guerrero. Después de cinco días de la emergencia, los mosquitos hembras fueron alimentados con sangre infecciosa con ZIKV. La infección (intestino), la diseminación (alas, piernas y cabezas) y la transmisión potencial (glándulas salivales) se evaluaron mediante RT-qPCR, a los 4, 7 y 14 días después de la alimentación. Resultados: La infección por ZIKV, la diseminación y las tasas potenciales de transmisión fueron de 96.2, 96.1 y 93.2%, respectivamente. Conclusiones: Los mosquitos Ae. aegypti (F1) de Acapulco presentan una alta competencia vectorial (93.2%). Según los autores de este estudio, este es el primer informe de competencia vectorial para ZIKV realizado en un laboratorio mexicano.

Sub-lethal dose of Bacillus sphaericus suppresses vector competence of Anopheles dirus for Plasmodium yoelii by up-regulating the Imd signaling pathway

Objective: To investigate the effect of sublethal dose of Bacillus sphaericus (Bs) 2 362 strain on the malaria transmission ability of Anopheles (An.) dirus (Hainan strain) and its molecular mechanism. Methods: Firstly, the fourth instar larvae of An. dirus was treated with sublethal dose of Bacillus sphaericus. The surviving larvae were then collected and placed into mosquito cages, where they were hatched into adult mosquitoes. These mosquitoes were recorded as Bs group. Meanwhile, the control group was set without any treatment. Then, for infection with Plasmodium yoelii BY265 RFP, 3- to 5-day old female adults were kept at 24 °C and fed on Plasmodium yoelii BY265 RFP-infected Kunming mice with a gametocytemia above 0.5%. On day 9-11 post infection, mosquitoes were dissected, and the oocysts on the midguts were examined under a fluorescence microscope. Thirdly, total RNA was extracted from mosquitoes of Bs group and the control group at different time-points respectively, and the cDNA were synthesized later. Finally, SYBR quantitative PCR was conducted to investigate the expression of Imd pathway anti-malaria molecules at different time-points, including TEP1 and Rel2, in Bs and control group mosquitoes. Results: Bs treatment remarkably reduced the infection rate of Plasmodium from 23.71% (124/523) to 16.23% (87/536) (Chi-square test, P=0.002 0.05). Additionally, the intensities of melanized oocysts were compared between the two groups, and no significant difference was found, either (P=0.566>0.05). Interestingly, compared with the control group, the expression levels of TEP1 and Rel2 in Bs group were obviously up-regulated in larval, adult and infected mosquitoes. Especially in 3 dpi and 7 dpi, the expression level of TEP1 in Bs group was nearly 4 times higher than that of the control group, while Rel2 reached to approximately 7 times. Conclusions: We firstly found that the sublethal dose of Bs significantly suppressed the vector competence of An. dirus to malaria parasites, which revealed a new important role of Bs on the basis of killing mosquito larvae. Furthermore, the Imd signaling pathway might play an effective way in Bs impacting the vector competence of An. dirus through upregulating the expression of NF-kB transcription factor Rel2, enhancing the expression of TEP1, which killed the Plasmodium, but not through melanization.

Differences in the replicative capacities of clinical isolates of dengue virus in C6/36 cells and in urban populations of Aedes aegypti from Colombia, South America

ABSTRACT Dengue, the most prevalent arboviral disease worldwide, is caused by any of the four dengue virus (DENV) serotypes that co-circulate constantly in hyperendemic areas such as Medellin (Colombia), and these serotypes are transmitted by mosquitoes of the genus Aedes. In this study, we evaluated the replicative capacity of strains isolated in Medellin between 2003 and 2007 in C6/36 cells and in colonies of Aedes aegypti collected during 2010-2011 from high or low-incidence areas within the same city. The phylogenetic analysis grouped isolates according to the predominant genotypes found in the Americas, and the in vitro characterization showed differences in the morphological changes induced by the isolates of each of the isolated serotypes compared to the reference serotypes. In vitro replicative capacity studies demonstrated that genomic copy number increased at four days post-infection and that cell viability decreased significantly compared to the control for all serotypes. The largest number of genomic copies in C6/36 was produced by DENV-2, followed by DENV-1 and DENV-4; DENV-3 produced the smallest number of genomic copies and had the smallest negative effect on cell viability. Finally, differences in the in vivo replication of intercolonial serotypes between the Rockefeller colony and the field colonies and among the intracolonial serotypes were found. The replication of DENV-2 at 7 and 14 days in both high- and low-incidence colonies was higher than that of the other serotypes, and replication of DENV-3 in the mosquito colonies was the most stable on the days evaluated. Our results support the notion that replication and, possibly, DENV transmission and severity depend on many factors, including serotype and vector characteristics.

Sensitivity of RT-PCR method in samples shown to be positive for Zika virus by RT-qPCR in vector competence studies

Abstract Tissue samples from mosquitoes artificially infected with Zika virus and shown to be positive by RT-qPCR were reexamined by RT-PCR. Using these samples we compared the two methods employed in virus RNA detection for vector competence studies. Results demonstrated that, albeit useful, RT-PCR gave false negatives with low viral loads (< 106 RNA copies/ml).

Culex quinquefasciatus from areas with the highest incidence of microcephaly associated with Zika virus infections in the Northeast Region of Brazil are refractory to the virus

Zika virus (ZIKV) is widely distributed in Brazil and the Northeast Region (NE) is the most affected zone, showing the highest incidence of microcephaly associated with ZIKV congenital infections worldwide. We report attempts to infect three populations of Culex quinquefasciatus from severely affected sites in the NE and Southeast Region (SE) of Brazil with three strains of ZIKV isolated from these localities. An Aedes aegypti population from the SE was used as a positive control. All tested Cx. quinquefasciatus populations were refractory to the ZIKV isolates. For these reasons, we believe Cx. quinquefasciatus should not be considered a potential vector of ZIKV in Brazil.

Avaliação da susceptibilidade de Lutzomyia migonei (Diptera: Psychodidae) ao desenvolvimento de Leishmania (Leishmania) infantum

Leishmania (Leishmania) infantum é o agente etiológico da leishmaniose visceral (LV) mais disseminado no mundo, com taxas de mortalidade significativas em casos humanos. Na América Latina, este parasito é transmitido principalmente por Lutzomyia longipalpis, entretanto, o papel de Lutzomyia migonei como um potencial vetor deste protozoário tem sido discutido. Investigações laboratoriais e de campo têm contribuído para esta hipótese, no entanto, a prova da competência vetorial de L. migonei ainda não foi fornecida. Neste estudo, foi avaliada pela primeira vez a susceptibilidade de L. migonei para duas cepas de L. (L.) infantum e realizada a comparação com o desenvolvimento em L. longipalpis. A colônia de L. migonei foi estabelecida na Faculdade de Ciências da Charles University em Praga, República Theca de espécimes capturados no município de Baturité, estado do Ceará...

Leishmania (Leishmania) infantum is the most widespread etiological agent of visceral leishmaniases (VL) in the world, with significant mortality rates in human cases. In Latin America, this parasite is primarily transmitted by Lutzomyia longipalpis, but the role of Lutzomyia migonei as a potential vector for this protozoan has been discussed. Laboratory and field investigations have contributed to this hypothesis. However, proof of the vector competence of L. migonei has not yet been provided. In this study, we evaluate for the first time the susceptibility of L. migonei to two L. (L.) infantum strains and compared with development of L. longipalpis. Colony of L. migonei was established at Faculty of Science, Charles University in Prague from specimens captured in Baturité municipality, Ceará state...

Vector biology prospects in dengue research

We argue that using more natural blood feeding methods to study mosquito vector competence for dengue viruses and exploring the effect of viral infection on other mosquito life-history traits that influence vectorial capacity will significantly advance our understanding of dengue epidemiology.

Competencia vectorial: consideraciones entomológicas y suinfluencia sobre la epidemiología del dengue / Vector competence: entomological considerations and its implications on the epidemiology of dengue

Las enfermedades transmitidas por vectores constituyen un complejo problema de salud en el ámbito mundial, especialmente en áreas tropicales y subtropicales, que por sus condiciones ambientales favorecen la supervivencia del vector. El dengue es la principal enfermedad transmitida por vectores en el mundo, cuyo agente etiológico es el Virus Dengue, el cual es transmitido por la picadura de mosquitos hematófagos de la especie Aedes aegypti. La interacción virus-vector es esencial para una transmisión efectiva y depende de factores tanto virales como vectoriales. Entre los factores relacionados con el vector, la competencia vectorial es considerada de gran importancia, pues se refiere a la capacidad intrínseca del vector para infectarse con el virus, permitir su replicación y posteriormente su transmisión a un huésped susceptible. A su vez, la habilidad para ser un buen vector depende principalmente de barreras naturales a la infección, barreras inmunológicas y presencia de receptores específicos para el virus. Todas estas características, sumadas a las características propias del virus, favorecerán o no la transmisión del mismo. Un estudio integral dela relación virus-vector permitirá comprender sus implicaciones en la epidemiología de la enfermedad. Estos temas han sido revisados en el presente documento, discutiendo su importancia dentro del contexto entomológico y epidemiológico.

Vector-borne diseases are a serious problem in public health, especially in tropical and subtropical areas where environmental conditions favor the survival and expansion of vectors into new habitats. Dengue fever is one of the most important vector-borne diseases transmitted by arthropods (arbovirosis) worldwide. The etiologic agent of the disease is the dengue virus, which is transmitted by the bite of bloodsucking Aedes aegypti mosquitoes. The virus-vector interaction is essential for the efficient transmission of the disease, and depends on both, viral factors and vector competence or intrinsic vector capacity to be infected with the virus. Vector competence allows virus replication and subsequent transmission to susceptible hosts. Factors that influence vector capacity include: natural barriers to infection, immunological defenses as well as the presence of receptors for the virus. All these factors inaddition to the viral characteristics will determine the degree of transmission. There is a need for a better understanding of the virus-vector relationship and its epidemiological implications. These issues are addressed in this article.