Identification of locally isolated entomopathogenic Fusarium species from the soil of Changa Manga Forest, Pakistan and evaluation of their larvicidal efficacy against Aedes aegypti

Dengue fever vectored by the mosquito Aedes aegypti is one of the most rapidly spreading insect-borne diseases. Current reliance of dengue vector control is mostly on chemical insecticides. Growing insecticide resistance in the primary mosquito vector, Aedes aegypti, limits the effectiveness of vector control through chemical insecticides. These chemical insecticides also have negative environmental impacts on animals, plants and human health. Myco-biocontrol agents are naturally occurring organisms and are found to be less damaging to the environment as compared to chemical insecticides. In the present study, entomopathogenic potential of local strains of fungi isolated from soil was assessed for the control of dengue vector. Local fungal isolates presents better alternative to introducing a foreign biocontrol strain, as they may be better adapted to environmental conditions of the area to survive and may have more entomopathogenic efficacy against target organism. Larvicidal efficacy of Fusarium equiseti and Fusarium proliferatum was evaluated against Aedes aegypti. Local strains of F. equiseti (MK371718) and F. proliferatum (MK371715) were isolated from the soil of Changa Manga Forest, Pakistan by using insect bait method. Larvicidal activity of two Fusarium spp. was tested against forth instar larvae of A. aegypti in the laboratory, using concentrations 105, 106, 107 and 108 conidia /ml. LC50 values for F. equiseti after 24h, 48h, 72h and 96h of exposure were recorded as 3.8x 108, 2.9x107, 2.0x107, and 7.1x106 conidia /ml respectively while LC50 values for F. proliferatum were recorded as 1.21x108, 9.6x107, 4.2x107, 2.6x107 conidia /ml respectively after 24h, 48h, 72h and 96h of exposure. The results indicate that among two fungal strains F. equiseti was found to be more effective in terms of its larvicidal activity than F. proliferatum against larvae of A. aegypti.

PENGARUH SALINITAS TERHADAP PERKEMBANGAN STADIUM AKUATIK Aedes aegypti DI LABORATORIUM

Aedes aegypti is known as the species of mosquito that breeds in fresh water, but due to the nature of adaptive this species found in habitats containing salt. This laboratory experiment aims to find out how different concentration of salinity will affect aquatic stages of Aedes aegypti. Salinity concentrations or treatment used in this study were 0‰, 2‰, 4‰, 6‰, 8‰ and 10‰ with five replicates. The observed parameters is the number of hatched eggs and number of surviving larvae or pupa after exposed to media containing salt. The results show that salinity influence both the number of hatced eggs and surviving larvae or pupae. There were decrease of number of hatched eggs and also the surviving larva or pupa as salinity increase. Analysis of variance showed significant relationship between salinity and the number of larvae or pupae survived but not with number of hatched eggs. Dengue vector adaptation against salinity become a phenomenon that needs to be examined and related to the spread of vector in habitats containing salt as well as transmission of the virus.

Community Behavior in Controlling Aedes aegypti Mosquito Breeding Places before and during the Covid-19 Pandemic

The COVID-19 epidemic has brought more people into their homes, so it is hoped that their behavior towards dengue mosquito nests in their homes will improve. The design of this study was cross-sectional with a consecutive sampling approach in data collection, which was conducted between May 6, 2020 – May 9, 2020, in Indonesia. Data was collected using a questionnaire (google form) which was assessed with ten indicators. Data analysis was carried out by using the average difference test to determine differences in people’s behavior. The analysis results showed no significant difference (p>0.005) with the community’s behavior in controlling the dengue vector before and during the pandemic. Suggestions that need to be made are continuous education about DHF and efforts to prevent transmission by eradicating mosquito nests.

Wolbachia cifB induces cytoplasmic incompatibility in the malaria mosquito vector

Wolbachia, a maternally inherited intracellular bacterial species, can manipulate host insect reproduction by cytoplasmic incompatibility (CI), which results in embryo lethality in crosses between infected males and uninfected females. CI is encoded by two prophage genes, cifA and cifB. Wolbachia, coupled with the sterile insect technique, has been used in field trials to control populations of the dengue vector Aedes albopictus, but CI-inducing strains are not known to infect the malaria vector Anopheles gambiae. Here we show that cifA and cifB can induce conditional sterility in the malaria vector An. gambiae. We used transgenic expression of these Wolbachia-derived genes in the An. gambiae germline to show that cifB is sufficient to cause embryonic lethality and that cifB-induced sterility is rescued by cifA expression in females. When we co-expressed cifA and cifB in male mosquitoes, the CI phenotype was attenuated. In female mosquitoes, cifB impaired fertility, which was overcome by co-expression of cifA. Our findings pave the way towards using CI to control malaria mosquito vectors.

Knowledge discovery and dengue forecasting applied in a four-year dataset collected at Natal, RN – Brazil

Dengue, a disease recognized as a health problem, causes significant impacts on health and affects millions of people each year worldwide. A suitable method for dengue vector surveillance is to count eggs the mosquitoes Aedes aegypti have laid in spatially distributed ovitraps. In view of this approach, this study uses a database collected in 397 ovitraps distributed across the municipality of Natal, RN – Brazil. The number of eggs in each ovitrap was counted weekly, over four years (2016 - 2019), and simultaneously analyzed with the incidence of dengue. Our results confirm that dengue incidence seems to be related to socioeconomic status in Natal. Using a deep learning model, we then predict the incidence of new dengue cases based on data obtained from the previous week of dengue or the number of eggs present in the ovitraps. The analysis shows that ovitrap data allows earlier detection (four to six weeks) when compared to dengue cases themselves (one week). Furthermore, the results confirm that quantifying Aedes aegypti eggs may be valuable for planning actions and public health interventions.

Repellent activity of three essential oils against dengue and filarial vector mosquitoes

Cymbopogon nardus, Syzygium aromaticum, and Citrus sinensis have been well known to possess insecticidal activity. Here, we investigated the repellent activity of individual of three essential oils (C. nardus, S. aromaticum, C. sinensis) and a combination of essential oils (C. nardus + C. sinensis, C. nardus + S. aromaticum, and C. sinensis + S. aromaticum) against a dengue vector, Aedes aegypti and a filarial vector, Culex quinquefasciatus. The essential oils (1 mg) were smeared evenly on the surface of the left arm (three volunteers) and then subjected to 25 females of A. aegypti and C. quinquefasciatus in the cage. The number of landed mosquitos was observed every hour for 7 hours to determine the protection index (PI). The result showed that individuals of three essential oils and a combination of essential oils generated > 90% of PI until 7 hours of application for both mosquitos species tested. Overall, the data demonstrated that individual of three essential oils, i.e., C. nardus, S. aromaticum, C. sinensis, and various combinations of essential oils (C. nardus + C. sinensis; C. nardus + S. aromaticum; C. sinensis + S. aromaticum) are promising as repellent agents against A. aegypti and C. quinquefasciatus.

Exposure of Exiguobacterium spp. to dengue vector, Aedes aegypti reduces growth and reproductive fitness

Background Aedes aegypti is a major insect vector because it transmits dreadful viruses as adults that cause disease in humans and other vertebrates. The use of mosquito’s microbiota has shown great potential impacts on vector control and mosquito reproductive competence. The present study aimed to examine the resident bacteria of mosquitoes which are used as a potent range to reduce the A. aegypti fitness. Isolated resident-bacterial strains from blood-fed Aedes species were characterized using gene sequencing and phylogenetic analysis, to assess the inhabitant bacterial strains survival rate in A. aegypti midgut, instar developmental duration, malformation and reproductive competence. Results The genetic distinctiveness of isolated bacterial strains belong to the genus Exiguobacterium spp. and further non-redundant nucleotide database search revealed that the species of effective strains were E. aestuarii (MN629357) and E. profundum (MN625885). Exposure of the freshly hatched larvae with these bacteria cell densities extended the developmental duration. For instance, exposure of A. aegypti larva with 0.42 × 108, 0.84 × 108 and 1.68 × 108 cells/mL of E. aestuarii extended the total developmental duration to 11.41, 14.29 and 14.78 days, respectively. It also reduced the fecundity and hatchability of A. aegypti female, with exposure to these bacteria, from 1033.33 eggs/10 females in the control series to 656.67 eggs/10 females. Conclusions These present findings indicate that the resident-bacterial strains from blood-fed mosquito not only extend the larval durations but also rendered the A. aegypti females sterile to various extents.